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PHILLIP GREENSPUN:
All right, we're

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going to talk about
aircraft performance, which

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is figuring out
all of this stuff

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if you're an
airplane, basically,

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how much runway you're
going to use on both ends,

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how long it's going to
take you to get there,

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which is another way of
saying how much fuel you're

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going to use.

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If it's a helicopter, it's
a little bit different.

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Mostly, you're worried
about hover performance.

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So if you're going
to a friend's house,

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are you going to be able to
park the helicopter in midair--

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that's called an out of
ground effect hover--

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and very slowly descend into
the backyard, dodging the trees

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and power lines
and anything else?

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So these are all
things that can be

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found in the aircraft manuals.

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And the FAA will test
you on them a little bit.

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This is important
partly because you

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want to be able to complete your
flight safely, and also because

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of FAR 91.103, which is
that, before you do a flight,

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you've got to become a--

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it's pretty all-embracing,
all-available information

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concerning weather, and aircraft
performance, how the aircraft's

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going to perform given the
altitude of where you're going,

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and the temperature that's
prevailing there at the time.

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Wind also, you know?

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If you find out that there's
a 40 knot wind scheduled

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for where you're going and
it's a direct crosswind

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to the only runway,
then that might

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to cause you to choose
a different airport.

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OK, here's a reminder
of the thrust and drag.

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Whenever you're
generating lift, you're

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also generating some drag.

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And that's lifting the unwanted
direction of backwards,

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usually.

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So the aircraft is also
producing a parasitic drag

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by trying to punch its way
through this vicious fluid

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of air.

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Where these summed
up drag curves

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intersect is pretty
much the bottom

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of the total drag curve, the
minimum drag, or L over D max.

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The climb performance,
the best speeds to go

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are all kind of tied
into this drag curve.

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And the best angle of
climb is what you use.

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That's a slower airspeed
and the best rate of climb.

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If you're in a small
airport, trying

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to clear the trees at
the end of the runway,

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you're going to fly Vx,
the best angle of climb.

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This is one of
those few V speeds

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that you're actually expected
to know the abbreviation for.

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And if you're going to just
take off out of a big airport,

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like Hanscom Field,
and just want

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to get up to your cruising
altitude reasonably quickly,

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then you--

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hey.

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Thanks, Richard.

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Richard's a Mooney pilot.

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Made it to California
many times.

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AUDIENCE: [INAUDIBLE]

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PHILLIP GREENSPUN: So if
you actually look at the Vx,

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one thing to notice is that it
all depends a bit on the wind.

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Let's say there's 100 knot
wind blowing down the runway.

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You don't need to fly
very fast in order

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to clear the trees at
the end of the runway

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because you're basically
already flying.

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And you can go straight up
like a helicopter in terms

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of your path over the
ground, whereas Vy,

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just to gain altitude,
that doesn't depend

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at all on the prevailing wind.

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So if you're trying to clear
something on the ground,

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the wind matters.

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A tail tailwind would
be very destructive.

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It'll be pushing you
towards the obstacle.

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And a headwind will
be very helpful.

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Cruise climb, most
of the time you

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don't actually push the
airplane to these speeds.

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They're pretty
far nose up, which

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is a little bit
alarming to passengers.

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And it's harder to
see over the nose,

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and the engine isn't getting as
much cooling air at these lower

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speeds.

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So typically we'll fly about 10
knots faster in a GA airplane.

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So for the Cirrus, for example,
96 is the book Vy at sea level,

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and flying something like 105
knots is more conventional.

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The PC-12 climbs--
you know, it might

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be able to do 3,000 feet
a minute at 120 knots.

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But if you're not
in a desperate hurry

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to get up above the bumpy
clouds or something,

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then 150 knots is
more conventional.

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OK, so let's remember that
you've got thrust and power.

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So the thrust is
a force that lets

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you climb up over the trees.

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The power is thrust
times the speed.

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And it's thrust operating
over a period of time.

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So the more excess power you
have, the higher the rate

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at which you can climb.

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Anyway, we'll see some
more of that here.

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You've got a best glide ratio.

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If you want to get to
the decent place to land

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and you've lost your engine,
what's a good speed to fly?

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Well, L over D max is an
excellent speed to fly,

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because that's where
the lift over drag

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is at its highest
point and you'll

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make the best time
over the ground.

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Again, that has to be adjusted
a little bit for wind.

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If you're going into 100
knot wind and the Cirrus best

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glide speed is 96
knots, that's not

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going to work out very well.

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You're not going to go
anywhere over the ground.

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That's a photo that I took
at the Newport Jazz Festival.

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I don't want to
say self portrait.

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Anyway, weight has a huge
factor on all these speeds,

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because actually a lot of them
are related to angle of attack.

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And it certainly affects
your performance.

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So everything about higher
weight is pretty bad.

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Wind, you might think that
a tailwind is always good.

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But really, the tailwind is only
good for extending your cruise

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range.

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Everything else, pretty much,
the headwind is better for.

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So think about the headwind.

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Again, think of
these extreme cases.

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If you've got 100 knot
wind right in your face,

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then you can fly without moving.

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That's basically a wind tunnel.

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OK, center of gravity.

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This is also a little
bit counterintuitive.

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If you load the airplane up so
that all the way to the back,

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and it's super
nose up, and you're

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having to push the stick
forward to keep the plane level,

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that actually is where you
get your maximum performance.

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Everything is better about
having an aft center of gravity

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with one exception, which is
the stability of the handling

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of the aircraft.

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And obviously, if you load
it up so much in the back

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that you can't
push the nose over,

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that would be outside of the
CG range, or well outside

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of this range, let's hope.

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Then you wouldn't even
be able to control

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the aircraft because you can't
get the nose down enough.

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So having that forward CG
gives you more stability.

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That's where you're going to
be when you're a student pilot.

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If you're in a four-seat
aircraft and it's just you

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and the instructor in front
and the back seats are empty,

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then it's pretty
obvious that it's

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going to be a somewhat forward
CG, because the aircraft is

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designed to hold at least
some weight in the back seats.

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One thing you can do is sort of,
just as a first approximation,

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you know, pay attention--

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we're going to have a
talk on weight and balance

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later from Tina.

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But just keep in mind that the
aircraft is kind of designed

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for, you know, two
adults in the front

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and maybe one adult in the
back, or two kids in the back.

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So if you load it
up that way, it's

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almost always going to work.

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If, on the other hand, you
have a big, heavy friend

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and, you know, his other
big heavy friend or his box

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of anvils, and the
guy says, well, look,

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I just want to
sleep in the back,

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I don't want to be up
front and get distracted,

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and you're a lightweight
person all by yourself

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from the front, you know,
that's the situation where it's

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important to really
do the calculations

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and think carefully about it.

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Because that wasn't something
that Cessna and Piper

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were thinking about when
they designed the aircraft.

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OK, atmospheric pressure.

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Remember we talked
about how the atmosphere

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is going to be
expanded when it's hot

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and contracted when it's cold?

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And the altimeter is
really telling you

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how much of the atmosphere
you've climbed up through.

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So you can see here on the
right, if you look over here,

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and you're measuring
your altitude,

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you're basically getting
this whole stack of molecules

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contributing to the
pressure, whereas if you're

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up high in the
stratosphere or something,

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only a handful of molecules are
on top of you putting pressure

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into your altimeter.

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OK, here's that standard
atmosphere again.

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So you can see it's two
niner niner two and 15

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degrees at sea level.

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So the aircraft performance
is hugely affected by changes

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in air density, which themselves
are affected by the prevailing

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pressure, which is mostly
a function of altitude,

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the temperature,
and the humidity.

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Usually, the conditions
are referenced to the ISA,

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the standard atmosphere.

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The summertime,
it'll be, you know,

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ISA plus 15 or ISA plus 20.

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And if it's the wintertime, it
might be ISA or ISA minus 20.

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When the air density is reduced
and there are fewer molecules

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around, the engine is not taking
in as much air for combustion.

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Remember that the jet engines
are normally aspirated.

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And the piston engines also
that are without a turbocharger,

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they're just trying to burn
up a fixed volume of air.

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And that's going to correspond
to a different number

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of molecules of air and fuel
depending on the altitude.

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The only good thing
about going up high--

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the propeller's
also not grabbing

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as much air for thrust.

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The only thing good
about going up high

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is that drag is
reduced, and that's

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why you see the
airliners up high.

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They go faster and they
save a lot of fuel.

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OK, some definitions.

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The pressure altitude
is just the--

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00:11:39,370 --> 00:11:43,430
it's going to be your
height above sea level

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00:11:43,430 --> 00:11:47,240
with the altimeter set
to two niner niner two.

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00:11:47,240 --> 00:11:51,680
You just have to take
the two niner niner

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00:11:51,680 --> 00:11:54,950
two minus the actual altimeter
setting that's being published,

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00:11:54,950 --> 00:12:00,480
multiply that by 1,000, so
a full inch of altimeter

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00:12:00,480 --> 00:12:03,555
adjustment, from two niner
niner two to three zero

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00:12:03,555 --> 00:12:06,690
niner two would correspond
to 1,000 foot difference

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00:12:06,690 --> 00:12:07,800
in pressure altitude.

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00:12:10,590 --> 00:12:13,265
And you can calculate
that by a chart.

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00:12:13,265 --> 00:12:14,640
Here's a chart
that they give you

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00:12:14,640 --> 00:12:15,890
if you don't like the formula.

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00:12:15,890 --> 00:12:19,860
So this is something, again,
you might have to do on a test.

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I'll say, OK, at two nine
niner two, the correction is 0.

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At 30.0, the
correction is minus 73.

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So up here you can see
we've got this formula where

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00:12:32,340 --> 00:12:35,610
we interpolated between the
two to try to figure out,

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00:12:35,610 --> 00:12:38,010
what would the
pressure altitude be

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if we start with a
field elevation of 3,563

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and the altimeter is two
niner niner six, which is

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just a little bit non-standard?

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We would expect a
40 foot difference.

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00:12:48,310 --> 00:12:51,000
If we look at the table
and we interpolate,

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we come up with a
36.5 foot difference.

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And we find out
that the airplane

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feels as though it's only at
3,526 feet above sea level,

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00:13:00,450 --> 00:13:05,900
assuming the temperature
matches that ISA standard.

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00:13:05,900 --> 00:13:08,530
All right, so density altitude
is a lot more important.

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00:13:08,530 --> 00:13:13,260
And oftentimes it will be
reported on the ASOS or ATIS.

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00:13:13,260 --> 00:13:15,780
So the airport will
actually tell you

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00:13:15,780 --> 00:13:19,560
density altitude is
3,000 feet or 2,000 feet

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or whatever it is.

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That you get from
correcting what's usually

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a relatively small correction
for pressure altitude compared

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00:13:29,550 --> 00:13:32,430
to the actual altitude,
but correcting it

243
00:13:32,430 --> 00:13:34,680
for the non-standard
temperature.

244
00:13:34,680 --> 00:13:36,908
I think, as I said
earlier, you know,

245
00:13:36,908 --> 00:13:39,450
flying is a lot more popular in
New England in the summertime

246
00:13:39,450 --> 00:13:43,110
than in the wintertime, so it's
usually warmer than standard.

247
00:13:43,110 --> 00:13:47,670
Density altitude has a
huge effect on performance.

248
00:13:47,670 --> 00:13:50,130
And it's a non-linear
relationship,

249
00:13:50,130 --> 00:13:52,110
so you have to look
it up in a table

250
00:13:52,110 --> 00:13:54,490
or calculate it with the E6B.

251
00:13:54,490 --> 00:13:54,990
We'll see.

252
00:13:54,990 --> 00:13:57,980
Maybe I'll play
around with the E6B

253
00:13:57,980 --> 00:14:00,105
so people can look
at it during breaks.

254
00:14:00,105 --> 00:14:05,508
I have the slide rule and
the manual right here.

255
00:14:05,508 --> 00:14:07,800
And I think we'll try to get
the document camera going,

256
00:14:07,800 --> 00:14:10,380
so maybe I can show you
guys some exciting slide

257
00:14:10,380 --> 00:14:14,150
rule activities.

258
00:14:14,150 --> 00:14:16,590
OK, so you can calculate
it, though, using the E6B,

259
00:14:16,590 --> 00:14:18,930
like I said, using charts.

260
00:14:18,930 --> 00:14:22,540
And there's various web
and app way of doing it.

261
00:14:22,540 --> 00:14:24,390
So the density altitude,
here's a chart.

262
00:14:24,390 --> 00:14:26,085
So again, this is
the kind of stuff

263
00:14:26,085 --> 00:14:27,210
that's on the written exam.

264
00:14:27,210 --> 00:14:30,580
You guys are all pretty good at
working with charts and tables,

265
00:14:30,580 --> 00:14:33,230
so I'm sure you won't
have any trouble.

266
00:14:33,230 --> 00:14:36,360
They're giving you these
initial conditions up here

267
00:14:36,360 --> 00:14:38,930
on your left.

268
00:14:38,930 --> 00:14:41,750
So you look to find
where the pressure

269
00:14:41,750 --> 00:14:44,610
altitude is on the chart.

270
00:14:44,610 --> 00:14:48,200
And it says to, you
know, add 626 feet, which

271
00:14:48,200 --> 00:14:50,990
is interpolating
between those two.

272
00:14:50,990 --> 00:14:53,360
Then you've got this
pressure altitude

273
00:14:53,360 --> 00:15:03,250
line of going from here
down to here at 5,856.

274
00:15:03,250 --> 00:15:06,240
And now we've got to correct
that for temperature.

275
00:15:06,240 --> 00:15:12,760
So here's our temperature of
about 80 degrees, 81 degrees.

276
00:15:12,760 --> 00:15:15,670
And then we go over to the
left, and we can read that--

277
00:15:15,670 --> 00:15:17,710
I think I told you guys
that, in the summertime,

278
00:15:17,710 --> 00:15:21,270
usually the density altitude
is about 2,000 feet higher

279
00:15:21,270 --> 00:15:23,500
than the pressure altitude.

280
00:15:23,500 --> 00:15:28,900
And sure enough,
here it's 8,250,

281
00:15:28,900 --> 00:15:35,080
which is about 2,400 feet higher
than the pressure altitude.

282
00:15:35,080 --> 00:15:39,790
So the density altitude gave us
a little more than a 2,000 foot

283
00:15:39,790 --> 00:15:42,100
boost for that
non-standard temperature.

284
00:15:42,100 --> 00:15:45,570
The reason it's so much,
I guess, is it's not--

285
00:15:45,570 --> 00:15:47,980
80 degrees at sea
level wouldn't be

286
00:15:47,980 --> 00:15:50,560
that high above the
standard temperature.

287
00:15:50,560 --> 00:15:55,830
But 81 degrees Fahrenheit
at a mile above sea level

288
00:15:55,830 --> 00:15:59,975
is quite a spectacular
temperature compared

289
00:15:59,975 --> 00:16:01,100
to the standard atmosphere.

290
00:16:01,100 --> 00:16:06,285
Let's go back to the
standard atmosphere.

291
00:16:06,285 --> 00:16:09,800
Yeah, so at 5,000
feet, it's only

292
00:16:09,800 --> 00:16:12,125
supposed to be seven
degrees Celsius.

293
00:16:17,120 --> 00:16:20,520
And here we said it was
about 27 degrees Celsius.

294
00:16:20,520 --> 00:16:22,100
So that's ISA plus 20.

295
00:16:22,100 --> 00:16:24,680
Just like I said, if you look
at a lot of jet performance

296
00:16:24,680 --> 00:16:27,980
charts, you have ISA minus
20 ISA and ISA plus 20.

297
00:16:32,066 --> 00:16:34,770
Oh, flight computer
demo if there's time.

298
00:16:34,770 --> 00:16:38,100
Let me just futz with that
at the end of all this.

299
00:16:38,100 --> 00:16:41,102
I'll give you an E6B intro.

300
00:16:41,102 --> 00:16:42,060
When are they the same?

301
00:16:44,940 --> 00:16:47,640
I think this is an FAA test
question, when the temperature

302
00:16:47,640 --> 00:16:54,490
distribution is the same as
that of the standard atmosphere.

303
00:16:54,490 --> 00:16:58,370
OK, humidity is also another
enemy, a little bit more

304
00:16:58,370 --> 00:17:00,350
surprisingly.

305
00:17:00,350 --> 00:17:03,560
The water vapor molecules,
actually, in the air

306
00:17:03,560 --> 00:17:06,260
actually reduce the
density of the air.

307
00:17:06,260 --> 00:17:08,628
You might think that
they would increase it.

308
00:17:08,628 --> 00:17:09,170
I don't know.

309
00:17:09,170 --> 00:17:12,290
Maybe there's a chemist or a
physicist in this crowd who

310
00:17:12,290 --> 00:17:13,190
can explain why.

311
00:17:13,190 --> 00:17:15,170
I'm not exactly sure myself.

312
00:17:15,170 --> 00:17:17,839
But it's just something to
remember, that contrary--

313
00:17:17,839 --> 00:17:20,690
if the air feels
heavy to you, it

314
00:17:20,690 --> 00:17:24,440
feels light to your aircraft
engine and to your wings.

315
00:17:24,440 --> 00:17:26,990
It's a smaller effect
than temperature,

316
00:17:26,990 --> 00:17:28,730
but the engine
performance supposedly

317
00:17:28,730 --> 00:17:32,210
can be reduced by about 7%.

318
00:17:32,210 --> 00:17:35,210
This is not something that
we normally correct for.

319
00:17:35,210 --> 00:17:38,210
However, there is this
nice web calculator

320
00:17:38,210 --> 00:17:41,294
that I found for free
on pilotfriend.com.

321
00:17:41,294 --> 00:17:47,510
And you get to enter the
relative humidity of the air.

322
00:17:47,510 --> 00:17:51,230
So where is that?

323
00:17:51,230 --> 00:17:53,270
We have the air temperature.

324
00:17:53,270 --> 00:17:54,920
Oh, we have the
dew point, right?

325
00:17:54,920 --> 00:17:58,520
So we said it was a 30 degree
temperature and a 28 degree dew

326
00:17:58,520 --> 00:17:59,520
point.

327
00:17:59,520 --> 00:18:03,050
So that's a pretty
narrow spread.

328
00:18:03,050 --> 00:18:06,200
And therefore, it's a
pretty high humidity day.

329
00:18:06,200 --> 00:18:09,980
So they say, well,
it's 78% humidity,

330
00:18:09,980 --> 00:18:14,290
and we're correcting
that up to 8,107.

331
00:18:14,290 --> 00:18:16,040
You can play around
with this on your own.

332
00:18:16,040 --> 00:18:18,662
If you reduce the dew point
to 10 degrees Celsius,

333
00:18:18,662 --> 00:18:20,120
which is going to
be a really dry--

334
00:18:20,120 --> 00:18:24,290
you know, 30 to 10 split
is a nice, dry day out west

335
00:18:24,290 --> 00:18:28,760
or, you know, here
occasionally a crisp day--

336
00:18:28,760 --> 00:18:30,650
then it's only 7,735.

337
00:18:30,650 --> 00:18:37,130
So the change in humidity
had about a 300-foot effect

338
00:18:37,130 --> 00:18:38,570
on the altitude.

339
00:18:38,570 --> 00:18:48,160
But the change in temperature
was nearly 3,000 feet.

340
00:18:48,160 --> 00:18:53,660
OK, the maximum convenience
way to do this is with apps.

341
00:18:53,660 --> 00:18:57,560
So ForeFlight, for example,
will just tell you.

342
00:18:57,560 --> 00:19:00,260
The density altitude--
this was, I think,

343
00:19:00,260 --> 00:19:01,910
Sunday night at Bedford.

344
00:19:01,910 --> 00:19:03,200
Let's look at this beautiful--

345
00:19:03,200 --> 00:19:05,617
I don't know how many people
will come to [INAUDIBLE] now.

346
00:19:05,617 --> 00:19:09,440
So Bedford's approximately
at sea level, about 130 feet

347
00:19:09,440 --> 00:19:10,520
above sea level.

348
00:19:10,520 --> 00:19:13,790
It was minus 4 degrees,
and the density altitude

349
00:19:13,790 --> 00:19:16,640
was minus 1,400.

350
00:19:16,640 --> 00:19:19,833
So we were flying,
you know, skimming

351
00:19:19,833 --> 00:19:21,500
the surface of the
Dead Sea or something

352
00:19:21,500 --> 00:19:23,730
in terms of performance.

353
00:19:23,730 --> 00:19:26,420
So the airplane will be
really happy about flying

354
00:19:26,420 --> 00:19:28,790
all wintertime, and
it'll climb better

355
00:19:28,790 --> 00:19:32,450
than the book, most of
the numbers in the book.

356
00:19:32,450 --> 00:19:35,900
OK, the density
altitude is often

357
00:19:35,900 --> 00:19:40,195
just kind of baked into
the performance chart.

358
00:19:44,090 --> 00:19:46,070
Pipers normally take
off with no flaps.

359
00:19:46,070 --> 00:19:48,320
But if you want to get off
the ground really quickly,

360
00:19:48,320 --> 00:19:51,110
like taking off over
grass or mud or something,

361
00:19:51,110 --> 00:19:53,720
you can put down
the flaps and try

362
00:19:53,720 --> 00:19:56,060
to have less time on
the ground and not be

363
00:19:56,060 --> 00:19:57,920
going so fast over the ground.

364
00:19:57,920 --> 00:19:59,650
Your ground rill
will be shortened.

365
00:19:59,650 --> 00:20:01,760
Anyway, so here,
they don't actually

366
00:20:01,760 --> 00:20:04,730
ask you to ever calculate
the density altitude.

367
00:20:04,730 --> 00:20:09,500
They just say, OK, it's
almost 30 degrees outside.

368
00:20:09,500 --> 00:20:12,650
And it looks like we're up
here at about 1,500 feet.

369
00:20:12,650 --> 00:20:16,050
So we'll start here on
the performance chart.

370
00:20:16,050 --> 00:20:17,200
These people are virtuous.

371
00:20:17,200 --> 00:20:21,900
The only weigh 2,175 total,
so we come down a little bit.

372
00:20:21,900 --> 00:20:23,940
And we can come
over here, and we

373
00:20:23,940 --> 00:20:25,540
find that it's going to take--

374
00:20:28,725 --> 00:20:30,320
is there a wind here--

375
00:20:30,320 --> 00:20:32,040
15 knots of headwind.

376
00:20:32,040 --> 00:20:35,180
So we come down
this graph and we

377
00:20:35,180 --> 00:20:39,650
find that it will
take us 1,500 feet

378
00:20:39,650 --> 00:20:44,450
to take off over a
50 foot obstacle.

379
00:20:50,960 --> 00:20:52,220
Fair enough?

380
00:20:52,220 --> 00:20:55,580
So anyway, we never figured out
what the density altitude was.

381
00:20:55,580 --> 00:21:01,110
It was just something
that affected

382
00:21:01,110 --> 00:21:02,360
where we started on the chart.

383
00:21:02,360 --> 00:21:03,920
I guess, maybe it's
implicit in here.

384
00:21:07,320 --> 00:21:08,820
I think it is implicit, right?

385
00:21:08,820 --> 00:21:11,130
Because we're starting up high.

386
00:21:11,130 --> 00:21:13,350
Maybe somebody who is
smarter can figure this out.

387
00:21:13,350 --> 00:21:14,835
Yeah, so sea level at 0--

388
00:21:18,250 --> 00:21:21,673
Yeah, I think we can pull
it out of those graphs.

389
00:21:21,673 --> 00:21:24,090
But nobody would, because what
you're really interested in

390
00:21:24,090 --> 00:21:26,940
is the number of how long you're
going to be on the runway.

391
00:21:26,940 --> 00:21:31,660
All right, you'll have to slow
down if you're in turbulence.

392
00:21:31,660 --> 00:21:34,570
So if you plan for some kind of
flight a certain amount of time

393
00:21:34,570 --> 00:21:36,220
and it's going to
be very bumpy--

394
00:21:36,220 --> 00:21:38,440
I remember we talked
about maneuvering speed.

395
00:21:38,440 --> 00:21:42,100
Depending on your weight,
you'll have to slow down

396
00:21:42,100 --> 00:21:44,140
to avoid bending the aircraft.

397
00:21:44,140 --> 00:21:47,140
Or, you know, turbulence
that's severe enough

398
00:21:47,140 --> 00:21:49,600
to bend the aircraft
is extremely rare.

399
00:21:49,600 --> 00:21:53,530
But turbulence that's sufficient
to make you and your passengers

400
00:21:53,530 --> 00:21:55,810
unhappy is a lot more common.

401
00:21:55,810 --> 00:21:59,260
And in both cases, you know,
you pull away back on the speed.

402
00:21:59,260 --> 00:22:01,510
So in the Pilatus,
for example, you'll

403
00:22:01,510 --> 00:22:04,580
pull back to 150
knots from 200 knots.

404
00:22:04,580 --> 00:22:08,080
In the Cirrus, you know, you
might pull back from 130 down

405
00:22:08,080 --> 00:22:09,715
to 100.

406
00:22:09,715 --> 00:22:11,890
And in a helicopter,
you know, you'll

407
00:22:11,890 --> 00:22:16,500
pull back from 110
knots to maybe 70.

408
00:22:16,500 --> 00:22:18,190
OK, pilot technique.

409
00:22:18,190 --> 00:22:23,260
So all the book numbers
depend on the pilot

410
00:22:23,260 --> 00:22:25,180
doing what the book says.

411
00:22:25,180 --> 00:22:28,060
So think about
clearing an obstacle

412
00:22:28,060 --> 00:22:29,440
at the end of the runway.

413
00:22:29,440 --> 00:22:33,280
That's dependent on the pilot
rotating within a couple

414
00:22:33,280 --> 00:22:36,910
knots of the specified rotation
speed, getting the gear

415
00:22:36,910 --> 00:22:41,110
and the flaps retracted
if they've been deployed,

416
00:22:41,110 --> 00:22:46,150
or if the gear are retractable
at the recommended airspeed,

417
00:22:46,150 --> 00:22:50,100
and just generally having the
pitch attitude and the air

418
00:22:50,100 --> 00:22:54,690
speeds where the manufacturer
tested the aircraft.

419
00:22:54,690 --> 00:22:55,605
And think about it.

420
00:22:55,605 --> 00:22:57,730
You might say, well, you
know, anybody can do that.

421
00:22:57,730 --> 00:23:00,420
You're rolling down the
runway at Hanscom Field.

422
00:23:00,420 --> 00:23:01,900
It's a mile and a half long.

423
00:23:01,900 --> 00:23:05,472
You know, you're fresh,
so that performance

424
00:23:05,472 --> 00:23:07,930
is-- you're probably going to
come pretty close to the book

425
00:23:07,930 --> 00:23:09,730
performance.

426
00:23:09,730 --> 00:23:11,260
But think about
doing a go-around.

427
00:23:11,260 --> 00:23:13,210
You've just done
a two hour flight.

428
00:23:13,210 --> 00:23:14,960
You were trying to
land at the airport.

429
00:23:14,960 --> 00:23:18,910
You know, somehow, either there
was somebody else on the runway

430
00:23:18,910 --> 00:23:21,160
or, you know, you didn't
get the approach just right,

431
00:23:21,160 --> 00:23:23,530
so you decided you're going
to go around and try again.

432
00:23:23,530 --> 00:23:24,988
At that point, you
know, you've got

433
00:23:24,988 --> 00:23:27,640
to reconfigure the airplane,
change the flap configuration,

434
00:23:27,640 --> 00:23:29,140
change the gear configuration.

435
00:23:31,950 --> 00:23:38,248
There's a couple interesting
incidents that have happened.

436
00:23:38,248 --> 00:23:40,290
Well, it was, unfortunately,
not very interesting

437
00:23:40,290 --> 00:23:41,140
for the people involved.

438
00:23:41,140 --> 00:23:42,960
But there was an
American Airlines flight

439
00:23:42,960 --> 00:23:46,590
that got disoriented in
Colombia in the clouds.

440
00:23:46,590 --> 00:23:48,690
And the terrain warning
system said, you know,

441
00:23:48,690 --> 00:23:50,850
terrain, terrain,
pull up, pull up.

442
00:23:50,850 --> 00:23:54,840
And so they advanced
the thrust levers.

443
00:23:54,840 --> 00:23:57,000
You can follow that
link and read about it.

444
00:23:57,000 --> 00:24:00,150
They advanced the thrust
levers and had maximum power,

445
00:24:00,150 --> 00:24:03,330
but they neglected to-- they
had the spoilers deployed

446
00:24:03,330 --> 00:24:04,590
for a descent.

447
00:24:04,590 --> 00:24:07,170
They didn't retract
the spoilers,

448
00:24:07,170 --> 00:24:09,720
so the airplane was
climbing but not nearly as

449
00:24:09,720 --> 00:24:13,080
well as it would have without
the spoilers retracted.

450
00:24:13,080 --> 00:24:15,000
So that's an example
where, you know,

451
00:24:15,000 --> 00:24:19,470
in a critical situation
or a fatigue situation,

452
00:24:19,470 --> 00:24:20,130
you may not--

453
00:24:23,140 --> 00:24:25,540
I wish I could get this--

454
00:24:25,540 --> 00:24:27,540
I don't know if I can
move this onto the screen.

455
00:24:27,540 --> 00:24:30,040
I want to show a picture of
this crazy airplane that I flew.

456
00:24:32,660 --> 00:24:33,660
Tada!

457
00:24:33,660 --> 00:24:35,450
Look at that Russian seaplane.

458
00:24:35,450 --> 00:24:37,370
It's got two Cirrus
engines in there.

459
00:24:45,932 --> 00:24:47,390
I don't even see
the second engine.

460
00:24:47,390 --> 00:24:48,020
Well, there it is.

461
00:24:48,020 --> 00:24:49,603
You can see that
propeller over there.

462
00:24:51,820 --> 00:24:52,320
So sorry.

463
00:24:52,320 --> 00:24:54,000
There's one propeller
sticking up.

464
00:24:54,000 --> 00:24:55,020
There is the other one.

465
00:24:55,020 --> 00:24:57,920
So it's got two Cirrus engines,
200 horsepower each mounted

466
00:24:57,920 --> 00:24:59,150
on pods.

467
00:24:59,150 --> 00:25:02,090
And if you say, how
can that airplane climb

468
00:25:02,090 --> 00:25:07,250
after an engine failure on
one little Cirrus engine

469
00:25:07,250 --> 00:25:08,048
when it has--

470
00:25:08,048 --> 00:25:08,590
I don't know.

471
00:25:08,590 --> 00:25:10,310
I think it could
seat seven people.

472
00:25:10,310 --> 00:25:11,780
The answer is it really can't.

473
00:25:14,430 --> 00:25:17,360
So I tested that airplane out
because I thought it was cool.

474
00:25:17,360 --> 00:25:19,790
And I went flying with
an airline captain.

475
00:25:19,790 --> 00:25:22,520
And piston twins
aren't really required

476
00:25:22,520 --> 00:25:25,160
to demonstrate any kind
of climb performance.

477
00:25:25,160 --> 00:25:27,170
For jets, there are
certain minimums.

478
00:25:27,170 --> 00:25:30,560
On one engine, it has to
be able to still climb 750

479
00:25:30,560 --> 00:25:31,970
feet per minute or something.

480
00:25:31,970 --> 00:25:36,570
But for these piston twins,
the FAA says, you know,

481
00:25:36,570 --> 00:25:38,570
you should know that
you're buying a pig anyway.

482
00:25:38,570 --> 00:25:41,420
And if you care, go and
get yourself a turbine,

483
00:25:41,420 --> 00:25:43,230
or don't load
everybody in there.

484
00:25:43,230 --> 00:25:45,020
But anyway, this
[INAUDIBLE] thing, it

485
00:25:45,020 --> 00:25:46,750
could not climb on one engine.

486
00:25:46,750 --> 00:25:49,388
We couldn't even maintain
altitude on one engine.

487
00:25:49,388 --> 00:25:50,930
And it turned out
that we'd forgotten

488
00:25:50,930 --> 00:25:53,270
to close the cowl flaps.

489
00:25:53,270 --> 00:25:56,210
It had these extra
openings for cooling

490
00:25:56,210 --> 00:25:59,370
to provide extra cooling
at high power settings.

491
00:25:59,370 --> 00:26:01,370
And if you don't close
them, there's extra drag.

492
00:26:01,370 --> 00:26:03,912
And that extra drag was enough
to turn what should have been,

493
00:26:03,912 --> 00:26:10,460
you know, 150 foot climb rate
or something into 150 foot sink

494
00:26:10,460 --> 00:26:11,870
rate or something.

495
00:26:11,870 --> 00:26:14,730
So that's another thing
that can affect performance.

496
00:26:14,730 --> 00:26:16,520
OK, runway condition.

497
00:26:16,520 --> 00:26:18,792
This really affects
your planning,

498
00:26:18,792 --> 00:26:20,750
whether you can take off,
whether you can land,

499
00:26:20,750 --> 00:26:23,040
how much weight you
can put in there.

500
00:26:23,040 --> 00:26:27,320
So for example,
if it's dry grass,

501
00:26:27,320 --> 00:26:30,560
you need a longer runway
than if it's paved.

502
00:26:30,560 --> 00:26:35,390
Alternatively, you can
take off at a lower weight.

503
00:26:35,390 --> 00:26:39,300
If it's wet grass, you need
a lot more room to land

504
00:26:39,300 --> 00:26:43,610
and, you know, yet
more room to take off.

505
00:26:43,610 --> 00:26:46,310
At the airline,
if the runway was

506
00:26:46,310 --> 00:26:49,460
grooved, which almost all
bigger US airports have

507
00:26:49,460 --> 00:26:53,300
these grooved runways, we
didn't make any adjustments.

508
00:26:53,300 --> 00:26:55,043
Didn't matter how
heavy the rain was.

509
00:26:55,043 --> 00:26:56,960
It didn't matter how
long it had been raining.

510
00:26:56,960 --> 00:27:00,110
We just assumed it was going
to perform exactly the same as

511
00:27:00,110 --> 00:27:02,590
if it were dry.

512
00:27:02,590 --> 00:27:04,320
If it's not a grooved
runway, though,

513
00:27:04,320 --> 00:27:06,020
and water can sit
on the runway, it

514
00:27:06,020 --> 00:27:07,830
can have a big effect
on performance.

515
00:27:07,830 --> 00:27:09,650
So here are some
numbers that I pulled.

516
00:27:09,650 --> 00:27:11,960
I'm type rated in the
Cessna Mustang, which

517
00:27:11,960 --> 00:27:13,880
is an interesting
little business jet.

518
00:27:13,880 --> 00:27:16,820
It lands at about the same
speed as the Beechcraft Baron,

519
00:27:16,820 --> 00:27:19,040
so it's a great beginner jet.

520
00:27:19,040 --> 00:27:23,180
Anyway, so in conditions where
you need 3,000 feet of runway,

521
00:27:23,180 --> 00:27:25,240
that's up at pretty
high altitude,

522
00:27:25,240 --> 00:27:28,730
you're going to need 4,240,
Cessna says, if it's wet.

523
00:27:28,730 --> 00:27:32,480
If water is actually standing on
it, I think 0.1 inches of water

524
00:27:32,480 --> 00:27:35,810
was even more, you'll
need yet more runway.

525
00:27:35,810 --> 00:27:38,360
If it's snow, a little bit more.

526
00:27:38,360 --> 00:27:41,270
Wet ice, it was
just off the chart.

527
00:27:41,270 --> 00:27:44,390
But if you started at
2,200 feet of dry runway,

528
00:27:44,390 --> 00:27:47,360
you would need 16,600 feet.

529
00:27:47,360 --> 00:27:51,830
So actually, oftentimes, when
the surface is contaminated,

530
00:27:51,830 --> 00:27:54,080
that's one reason why
even fairly small business

531
00:27:54,080 --> 00:27:56,600
jets may need a long
runway, like at Logan

532
00:27:56,600 --> 00:27:58,100
or at Hanscom Field.

533
00:27:58,100 --> 00:28:01,340
Even an airport like
Nashua, which has 6,000 feet

534
00:28:01,340 --> 00:28:04,160
may not be enough if they're
reporting that there's

535
00:28:04,160 --> 00:28:07,260
snow on the runway.

536
00:28:07,260 --> 00:28:09,550
OK, what about slope?

537
00:28:09,550 --> 00:28:14,910
So going downhill is obviously
a lot easier than going uphill.

538
00:28:14,910 --> 00:28:18,740
And you can see here-- and
also stopping going uphill

539
00:28:18,740 --> 00:28:19,750
is a lot easier.

540
00:28:19,750 --> 00:28:22,170
So here are some numbers
from the Cirrus book

541
00:28:22,170 --> 00:28:26,550
that every one degree of slope
increases your takeoff run

542
00:28:26,550 --> 00:28:30,750
by 22% at sea
level, for example.

543
00:28:30,750 --> 00:28:39,200
And you also get a 9% reduction
in the landing distance.

544
00:28:39,200 --> 00:28:41,700
OK, ceiling.

545
00:28:41,700 --> 00:28:43,290
The service ceiling
of the aircraft

546
00:28:43,290 --> 00:28:46,050
is a little bit below
the absolute ceiling.

547
00:28:46,050 --> 00:28:47,760
That's where the FAA
says the plane will

548
00:28:47,760 --> 00:28:50,010
climb 100 feet per minute.

549
00:28:50,010 --> 00:28:51,970
The manufacturer has
demonstrated to the FAA

550
00:28:51,970 --> 00:28:55,260
that the airplane could, at
least when it was brand new,

551
00:28:55,260 --> 00:28:57,540
make 100 feet per
minute in climb rate.

552
00:28:57,540 --> 00:29:02,820
So that's 13,500 feet
for a 172 Cessna.

553
00:29:02,820 --> 00:29:05,340
And I think that's pretty
typical for these normally

554
00:29:05,340 --> 00:29:06,870
aspirated four-seaters.

555
00:29:06,870 --> 00:29:09,920
Somewhere around there is
where it'll stop climbing.

556
00:29:09,920 --> 00:29:12,480
The Cirrus, there's
a limitation in there

557
00:29:12,480 --> 00:29:16,620
that says maximum operating
altitude is 17,500 feet.

558
00:29:16,620 --> 00:29:18,570
I think that's more
regulatory, because you

559
00:29:18,570 --> 00:29:21,490
can't take the Cirrus up
into the flight levels.

560
00:29:21,490 --> 00:29:25,740
They need extra equipment to
go up above 18,000 feet, maybe.

561
00:29:25,740 --> 00:29:28,140
I don't think it's really
practical to get up

562
00:29:28,140 --> 00:29:31,800
to 17,500 feet at
maximum gross weight

563
00:29:31,800 --> 00:29:33,270
in the standard atmosphere.

564
00:29:33,270 --> 00:29:37,110
I've gotten into about 13,000
feet out west in the summer,

565
00:29:37,110 --> 00:29:40,320
so that is more like
being at 15,000 feet.

566
00:29:40,320 --> 00:29:42,730
But it was barely climbing.

567
00:29:42,730 --> 00:29:46,320
OK, range versus endurance.

568
00:29:46,320 --> 00:29:50,850
So we're going to get back into
the power and drag curves here.

569
00:29:50,850 --> 00:29:53,400
The max range airspeed is
going to depend on the wind,

570
00:29:53,400 --> 00:29:55,720
like I said earlier.

571
00:29:55,720 --> 00:29:57,990
If you have 100 knot
headwind, then you

572
00:29:57,990 --> 00:30:03,320
have to go faster than 100
knots in order to go anywhere.

573
00:30:03,320 --> 00:30:05,860
If you want to loiter for some
reason-- this year at Oshkosh

574
00:30:05,860 --> 00:30:08,470
was a nightmare for
people who didn't go IFR.

575
00:30:08,470 --> 00:30:10,390
They had a lot of
marginal VFR weather.

576
00:30:10,390 --> 00:30:15,970
So for the first couple of
days, when people were arriving,

577
00:30:15,970 --> 00:30:18,640
there were these short
windows, just an hour or two,

578
00:30:18,640 --> 00:30:20,980
when people could
really get in legally,

579
00:30:20,980 --> 00:30:23,000
the VFR homebuilder types.

580
00:30:23,000 --> 00:30:24,970
So they were just holding.

581
00:30:24,970 --> 00:30:27,460
People were literally
holding for three hours

582
00:30:27,460 --> 00:30:30,190
and then finally had to give
up and go and refuel somewhere.

583
00:30:30,190 --> 00:30:31,690
But if you're in
that situation, you

584
00:30:31,690 --> 00:30:35,260
want to set your speed to
whatever the minimum fuel

585
00:30:35,260 --> 00:30:36,280
consumption speed is.

586
00:30:36,280 --> 00:30:38,330
And it can be quite different.

587
00:30:38,330 --> 00:30:42,190
The Robinson R44 manual talks
about 100 knots for max range.

588
00:30:42,190 --> 00:30:45,820
I believe that's assuming a 10
knot headwind, since usually

589
00:30:45,820 --> 00:30:47,320
we're suffering
with a headwind more

590
00:30:47,320 --> 00:30:49,150
often than with a tailwind.

591
00:30:49,150 --> 00:30:51,080
And you might say,
how is that possible?

592
00:30:51,080 --> 00:30:53,870
How is it possible
to have a headwind--

593
00:30:53,870 --> 00:30:57,740
unless God hates you, how
is it possible to have

594
00:30:57,740 --> 00:30:59,240
a headwind more
than half the time?

595
00:30:59,240 --> 00:31:01,000
If you think about it--

596
00:31:01,000 --> 00:31:02,320
Richard, you know the answer?

597
00:31:02,320 --> 00:31:02,903
RICHARD: I do.

598
00:31:02,903 --> 00:31:04,153
PHILLIP GREENSPUN: What is it?

599
00:31:04,153 --> 00:31:05,508
RICHARD: Here's the question.

600
00:31:05,508 --> 00:31:08,540
You're flying 100
miles to an airport.

601
00:31:11,640 --> 00:31:13,300
In zero wind, how
long does it take

602
00:31:13,300 --> 00:31:15,920
to fly-- you're on an airplane
that flies 100 miles an hour.

603
00:31:15,920 --> 00:31:17,620
How long does it take
to fly round trip?

604
00:31:17,620 --> 00:31:19,037
PHILLIP GREENSPUN:
Trick question.

605
00:31:21,230 --> 00:31:23,910
RICHARD: 100 miles apart,
100 miles an hour airplane,

606
00:31:23,910 --> 00:31:24,950
no wind.

607
00:31:24,950 --> 00:31:26,808
How long is a round
trip going to take?

608
00:31:26,808 --> 00:31:27,764
AUDIENCE: 2 hours?

609
00:31:27,764 --> 00:31:28,720
RICHARD: Yeah.

610
00:31:28,720 --> 00:31:31,772
Let's say you have
a 50 knot headwind.

611
00:31:31,772 --> 00:31:33,340
It's exactly on your nose.

612
00:31:33,340 --> 00:31:35,920
You can get 50 knots
headwind on the way out

613
00:31:35,920 --> 00:31:38,223
and 50 knot tailwind
on the way back.

614
00:31:38,223 --> 00:31:39,140
How long does it take?

615
00:31:39,140 --> 00:31:40,440
AUDIENCE: 2 hours.

616
00:31:40,440 --> 00:31:41,560
RICHARD: Wrong.

617
00:31:41,560 --> 00:31:43,788
Work it out.

618
00:31:43,788 --> 00:31:45,580
PHILLIP GREENSPUN:
Well, that's one aspect.

619
00:31:45,580 --> 00:31:49,510
You're going to spend more of
your time, as Richard's saying.

620
00:31:49,510 --> 00:31:52,990
It's going to take you two hours
to get there in one direction,

621
00:31:52,990 --> 00:31:55,630
and then it won't take
you zero time to get back,

622
00:31:55,630 --> 00:31:59,050
so you're spending more of
your time in the headwind

623
00:31:59,050 --> 00:32:00,225
than in the tailwind.

624
00:32:00,225 --> 00:32:01,600
But there's
something even worse.

625
00:32:01,600 --> 00:32:03,225
I saw this the other
day in the Cirrus.

626
00:32:03,225 --> 00:32:07,833
There was about a 70 knot
wind that was actually

627
00:32:07,833 --> 00:32:09,250
a little bit-- it
should have been

628
00:32:09,250 --> 00:32:10,570
a little bit of a tailwind.

629
00:32:10,570 --> 00:32:14,770
It was more than 90 degrees
off my desired track.

630
00:32:14,770 --> 00:32:16,930
But if you think about
it, the airplane's

631
00:32:16,930 --> 00:32:20,500
constantly having to fight
its way back into that wind,

632
00:32:20,500 --> 00:32:22,910
so it's effectively taking
a longer flight path.

633
00:32:22,910 --> 00:32:28,300
So even the wind is directly
a beam wind 90 degrees off,

634
00:32:28,300 --> 00:32:32,910
there's actually-- the
majority of the circle,

635
00:32:32,910 --> 00:32:35,350
the 360 degrees circle
of wind directions,

636
00:32:35,350 --> 00:32:38,110
the majority of
that is subtracting

637
00:32:38,110 --> 00:32:44,000
from your performance and has at
least some headwind component.

638
00:32:44,000 --> 00:32:45,590
Sound crazy?

639
00:32:45,590 --> 00:32:46,640
Think about it, yeah.

640
00:32:46,640 --> 00:32:50,780
So if you're going 100 miles and
there's also this 100 knot side

641
00:32:50,780 --> 00:32:53,480
wind, you're having
to spend quite

642
00:32:53,480 --> 00:32:59,930
a bit of your energy continuing
to steer into that side wind.

643
00:32:59,930 --> 00:33:07,010
OK, here is a power and
drag curve for an RV-6A.

644
00:33:07,010 --> 00:33:10,700
The experimental guys
are, in this case,

645
00:33:10,700 --> 00:33:13,880
more aggressive about
producing charts.

646
00:33:13,880 --> 00:33:17,480
So if you actually care
about where you're going,

647
00:33:17,480 --> 00:33:22,160
you want to be a little bit
up the power required curve.

648
00:33:22,160 --> 00:33:25,040
You want to find out where it's
tangent to one of these lines

649
00:33:25,040 --> 00:33:26,360
going back to zero.

650
00:33:26,360 --> 00:33:29,037
And if all you care about
is maximum endurance,

651
00:33:29,037 --> 00:33:30,620
you just want to be
at the point where

652
00:33:30,620 --> 00:33:32,720
the curve is at
its bare minimum,

653
00:33:32,720 --> 00:33:35,300
because then you're consuming
the least power and, in theory,

654
00:33:35,300 --> 00:33:37,600
burning the least
amount of fuel.

655
00:33:37,600 --> 00:33:38,660
Does that make sense?

656
00:33:43,962 --> 00:33:46,490
All right, The terms.

657
00:33:46,490 --> 00:33:51,860
Ground roll, these
performance charts

658
00:33:51,860 --> 00:33:54,140
in the book that you
get with the airplane,

659
00:33:54,140 --> 00:33:55,890
they will assume a static start.

660
00:33:55,890 --> 00:33:57,770
So that means you're
holding the brakes,

661
00:33:57,770 --> 00:34:00,980
you slam the power forward,
you let off the brakes,

662
00:34:00,980 --> 00:34:03,980
and you're going to get the
book numbers, because there's

663
00:34:03,980 --> 00:34:07,460
no acceleration
time for the engine.

664
00:34:07,460 --> 00:34:10,217
And actually, that's how jets
are supposed to take off, too.

665
00:34:10,217 --> 00:34:12,800
But you probably remember from
your commercial flights, that's

666
00:34:12,800 --> 00:34:14,489
not really how it happens.

667
00:34:14,489 --> 00:34:17,300
The pilots don't hold the
brakes, you know, spend--

668
00:34:17,300 --> 00:34:20,870
it takes maybe 10 seconds
for a really heavy jet engine

669
00:34:20,870 --> 00:34:21,969
to spool up to full power.

670
00:34:21,969 --> 00:34:24,344
They don't just sit
there holding the brakes,

671
00:34:24,344 --> 00:34:26,130
engine's at the max,
and everything's

672
00:34:26,130 --> 00:34:28,130
screaming in the airplane,
shaking, because it's

673
00:34:28,130 --> 00:34:29,360
just uncomfortable.

674
00:34:29,360 --> 00:34:31,113
So they usually cheat--

675
00:34:31,113 --> 00:34:32,780
technically, they're
not really supposed

676
00:34:32,780 --> 00:34:36,050
to do it because, you know, at
that point, your test pilots.

677
00:34:36,050 --> 00:34:39,409
You don't really have any
data for a rolling takeoff.

678
00:34:39,409 --> 00:34:42,090
But, you know,
again, it would be

679
00:34:42,090 --> 00:34:43,840
kind of unnerving for
passengers, I think,

680
00:34:43,840 --> 00:34:46,048
if they are sitting there
with the airplane straining

681
00:34:46,048 --> 00:34:46,850
against the brakes.

682
00:34:49,580 --> 00:34:51,583
OK, same deal here.

683
00:34:51,583 --> 00:34:53,000
Ground roll and
the total distance

684
00:34:53,000 --> 00:34:54,409
to clear the 50
foot obstacle, this

685
00:34:54,409 --> 00:34:56,951
is what I was telling you about
the other day with the Cirrus

686
00:34:56,951 --> 00:34:59,420
hero who wanted
to go to, I think,

687
00:34:59,420 --> 00:35:01,340
about 2,500 feet of runway.

688
00:35:01,340 --> 00:35:02,920
Actually, we had
to subtract some.

689
00:35:02,920 --> 00:35:05,510
I think it was 2,700 minus 400.

690
00:35:05,510 --> 00:35:07,900
He had about 2,300
feet of runway.

691
00:35:07,900 --> 00:35:11,090
And he wanted to go there in the
Cirrus, which takes 2,100 feet.

692
00:35:11,090 --> 00:35:12,720
Another guy actually
wanted to go to--

693
00:35:12,720 --> 00:35:16,340
there's a private air park
in Falmouth, Massachusetts

694
00:35:16,340 --> 00:35:18,680
where you can have a house
right next to the runway

695
00:35:18,680 --> 00:35:21,530
and keep the airplane
in your garage.

696
00:35:21,530 --> 00:35:24,260
And that airport's
only 2,300 feet long.

697
00:35:24,260 --> 00:35:27,200
And another east
coast aero club guy--

698
00:35:27,200 --> 00:35:29,000
I was handing the
airplane over to him

699
00:35:29,000 --> 00:35:30,542
and he had this huge
friend with him.

700
00:35:30,542 --> 00:35:32,960
This guy was like
a NFL linebacker.

701
00:35:32,960 --> 00:35:34,820
So it was just the
two of them, but big.

702
00:35:34,820 --> 00:35:38,255
And he wanted it also at
full, topped off on fuel,

703
00:35:38,255 --> 00:35:40,130
so they're going to be
right at gross weight.

704
00:35:40,130 --> 00:35:41,297
I said, where are you going?

705
00:35:41,297 --> 00:35:42,700
He said Falmouth.

706
00:35:42,700 --> 00:35:45,020
He'd just gotten his
private pilot certificate

707
00:35:45,020 --> 00:35:46,580
a few months earlier.

708
00:35:46,580 --> 00:35:48,930
This guy was not commercial
IFR rated like the other.

709
00:35:48,930 --> 00:35:51,620
And I said, look, you know,
if you do everything perfect,

710
00:35:51,620 --> 00:35:54,950
you're going to use
up 92% of that runway

711
00:35:54,950 --> 00:35:57,780
because it's hemmed
in by these obstacles.

712
00:35:57,780 --> 00:35:59,270
So don't do it.

713
00:35:59,270 --> 00:36:03,110
So he did end up going
to Hyannis, I think.

714
00:36:03,110 --> 00:36:07,400
All right, landing
technique can actually

715
00:36:07,400 --> 00:36:10,250
affect the performance.

716
00:36:10,250 --> 00:36:14,790
So they talk about, an average
pilot, the book numbers,

717
00:36:14,790 --> 00:36:17,060
they're predicated on
extremely aggressive braking,

718
00:36:17,060 --> 00:36:20,810
like right to the point where
you would flat spot the tires.

719
00:36:20,810 --> 00:36:23,480
So don't count on getting those
book numbers unless you're

720
00:36:23,480 --> 00:36:28,010
willing to be more
aggressive than probably you

721
00:36:28,010 --> 00:36:29,000
would want to be.

722
00:36:29,000 --> 00:36:32,600
And actually, I'll tell you a
story about my airline days.

723
00:36:32,600 --> 00:36:35,180
I did a visual approach
in the Laguardia.

724
00:36:35,180 --> 00:36:38,430
And with jets, it's
not conventional to try

725
00:36:38,430 --> 00:36:40,430
to do the really greaser
landings that you would

726
00:36:40,430 --> 00:36:42,140
do in a little
airplane, because you

727
00:36:42,140 --> 00:36:45,410
need to get the airplane down
and the spoilers to pop up.

728
00:36:45,410 --> 00:36:47,000
The jets are very
efficient gliders.

729
00:36:47,000 --> 00:36:49,710
They don't have a
big prop in front.

730
00:36:49,710 --> 00:36:52,010
And when you pull the power
back on a piston aircraft,

731
00:36:52,010 --> 00:36:54,410
it really slows down
dramatically because the prop

732
00:36:54,410 --> 00:36:55,777
has a lot of air resistance.

733
00:36:55,777 --> 00:36:57,860
None of that's going for
you with the jet which is

734
00:36:57,860 --> 00:36:59,750
more efficient to begin with.

735
00:36:59,750 --> 00:37:02,720
So basically, the task
of an airline pilot

736
00:37:02,720 --> 00:37:06,530
is really to slam it on, and
that way the spoilers pop up

737
00:37:06,530 --> 00:37:08,780
and then the brakes start
really working effectively.

738
00:37:08,780 --> 00:37:10,850
And you turn off the
runway in Laguardia

739
00:37:10,850 --> 00:37:13,250
before you go into the river.

740
00:37:13,250 --> 00:37:14,960
So I landed like a
Cirrus, because it

741
00:37:14,960 --> 00:37:18,770
was my first month on
the job, and I chewed up

742
00:37:18,770 --> 00:37:22,700
by 1,500 feet of runway before
the airplane touched down.

743
00:37:22,700 --> 00:37:25,520
And I applied fairly gentle
braking and thrust reverse

744
00:37:25,520 --> 00:37:27,980
and turned off after about
5,000 feet of runway.

745
00:37:27,980 --> 00:37:29,480
And the captain's
like, that sucked.

746
00:37:29,480 --> 00:37:32,030
I'm going to show you how
it's done the next leg.

747
00:37:32,030 --> 00:37:36,860
So we did Laguardia to
Charlotte, North Carolina.

748
00:37:36,860 --> 00:37:39,323
Who else did that leg?

749
00:37:39,323 --> 00:37:40,585
AUDIENCE: [INAUDIBLE]

750
00:37:40,585 --> 00:37:41,960
PHILLIP GREENSPUN:
Captain Sully.

751
00:37:41,960 --> 00:37:45,330
So he dumped his passengers
into a filthy cold river

752
00:37:45,330 --> 00:37:47,170
and they called him a hero.

753
00:37:47,170 --> 00:37:50,250
I got my passengers to
Charlotte warm and dry,

754
00:37:50,250 --> 00:37:52,070
and where was my medal?

755
00:37:52,070 --> 00:37:53,940
Where is my fame?

756
00:37:53,940 --> 00:37:54,630
Nowhere.

757
00:37:54,630 --> 00:37:55,980
All right, so life is unfair.

758
00:37:55,980 --> 00:37:57,190
You've learned that.

759
00:37:57,190 --> 00:37:59,460
Anyway, so the captain
takes this one.

760
00:37:59,460 --> 00:38:00,840
Air traffic control lines us up.

761
00:38:00,840 --> 00:38:02,010
Instead of the
visual approach where

762
00:38:02,010 --> 00:38:04,593
you're doing everything by eye
and following another aircraft,

763
00:38:04,593 --> 00:38:07,020
and you can't use any
of the fancy automation,

764
00:38:07,020 --> 00:38:11,190
we were lined up 10 or 15 miles
out for a straight in approach

765
00:38:11,190 --> 00:38:14,370
to this angled
runway at Charlotte.

766
00:38:14,370 --> 00:38:17,280
And all the captain had
to do was-- on autopilot,

767
00:38:17,280 --> 00:38:19,328
all he had to do was
tweak the thrust levers

768
00:38:19,328 --> 00:38:20,370
for the perfect airspeed.

769
00:38:20,370 --> 00:38:21,850
The autopilot's flying.

770
00:38:21,850 --> 00:38:25,180
He disconnects the autopilot a
couple feet above the ground.

771
00:38:25,180 --> 00:38:26,070
Now he's hand flying.

772
00:38:26,070 --> 00:38:28,500
All he has to do--
the CRJ doesn't have,

773
00:38:28,500 --> 00:38:30,790
the 50-seater, any
leading edge devices,

774
00:38:30,790 --> 00:38:33,930
so it has to be pointed
down a bit like a lawn dart.

775
00:38:33,930 --> 00:38:36,560
It's not that different
from landing a Cirrus.

776
00:38:36,560 --> 00:38:38,350
It's unconventional
for an airliner.

777
00:38:38,350 --> 00:38:40,380
The airliners, you
notice they usually--

778
00:38:40,380 --> 00:38:42,270
because of the
leading edge devices,

779
00:38:42,270 --> 00:38:43,950
even when they're
going 120 knots or so,

780
00:38:43,950 --> 00:38:46,900
they can be kind of nose up
and they still fly pretty well.

781
00:38:46,900 --> 00:38:48,990
So the airplane
almost can be flown--

782
00:38:48,990 --> 00:38:51,570
and it can auto
land, in some cases,

783
00:38:51,570 --> 00:38:54,510
onto the runway by itself with
just a slight additional flare

784
00:38:54,510 --> 00:38:55,410
at the end.

785
00:38:55,410 --> 00:38:59,670
The CRJ has to be kept nose
down 145 knots faster than all

786
00:38:59,670 --> 00:39:04,170
but the very biggest jets, and
then it has to be, you know,

787
00:39:04,170 --> 00:39:07,740
flared from minus five to
maybe plus five or plus

788
00:39:07,740 --> 00:39:09,210
seven at the end.

789
00:39:09,210 --> 00:39:13,440
So the captain, after telling
me what a bad job I had done,

790
00:39:13,440 --> 00:39:17,190
he flared about
five feet too high,

791
00:39:17,190 --> 00:39:20,100
and the airplane just sailed
over 4,500 feet of runway,

792
00:39:20,100 --> 00:39:22,860
I think, before it
finally touched down.

793
00:39:22,860 --> 00:39:25,270
And he slammed on the brakes,
maximum thrust reverse.

794
00:39:25,270 --> 00:39:26,290
We barely made it off.

795
00:39:26,290 --> 00:39:29,430
I think we made it off
after 7,200 feet of runway,

796
00:39:29,430 --> 00:39:32,700
so we would have been, I think,
in the water in Laguardia.

797
00:39:32,700 --> 00:39:35,850
So that's the kind of thing
where, you know, you can't--

798
00:39:35,850 --> 00:39:38,970
that's why these
safety margins are

799
00:39:38,970 --> 00:39:42,385
good to build into your own
flying, because, you know,

800
00:39:42,385 --> 00:39:44,010
the book number said
the airplane would

801
00:39:44,010 --> 00:39:46,557
land a lot shorter than that.

802
00:39:46,557 --> 00:39:49,140
Also, in a jet, there's really
not a good go-around technique.

803
00:39:49,140 --> 00:39:50,515
Once you're below
50 feet, you're

804
00:39:50,515 --> 00:39:53,970
not supposed to try to
add power and go around

805
00:39:53,970 --> 00:39:57,030
because it takes a while
to spool the engines up.

806
00:39:57,030 --> 00:39:59,100
All right, in
turbulence, you usually

807
00:39:59,100 --> 00:40:00,580
will increase your
approach speed,

808
00:40:00,580 --> 00:40:03,240
which means you're going
to chew up more runway.

809
00:40:03,240 --> 00:40:06,670
You're supposed to add half the
gust factor as a rule of thumb.

810
00:40:06,670 --> 00:40:09,570
So if the wind is 15
gusting 25, you're

811
00:40:09,570 --> 00:40:11,790
going to speed up your
approach by five knots.

812
00:40:11,790 --> 00:40:14,550
And I got the numbers
here for the Cirrus.

813
00:40:14,550 --> 00:40:16,530
75 is kind of a
good overall number,

814
00:40:16,530 --> 00:40:18,330
and then you'll
beef it up to 80.

815
00:40:18,330 --> 00:40:21,210
But that means, unless it
really is a headwind when you're

816
00:40:21,210 --> 00:40:24,540
landing, you're going to
chew up a little more runway

817
00:40:24,540 --> 00:40:26,060
than expected.

818
00:40:26,060 --> 00:40:29,520
OK, flaps, as Tina
mentioned, they

819
00:40:29,520 --> 00:40:31,440
enable you to keep
your approach speed

820
00:40:31,440 --> 00:40:34,920
low while having a nice
steep approach angle.

821
00:40:34,920 --> 00:40:38,335
So that's good for getting
over trees and stuff.

822
00:40:38,335 --> 00:40:40,710
If you're in an aerobatic
airplane or something else that

823
00:40:40,710 --> 00:40:42,210
doesn't have flaps,
you can actually

824
00:40:42,210 --> 00:40:45,180
slip and go sideways
down towards the runway

825
00:40:45,180 --> 00:40:48,060
and get over the obstacles,
but it's a lot easier

826
00:40:48,060 --> 00:40:49,720
just to put the flaps down.

827
00:40:49,720 --> 00:40:57,840
OK, the charts come in all
kinds of variations in the POH,

828
00:40:57,840 --> 00:40:59,880
especially for the
bigger airplanes.

829
00:40:59,880 --> 00:41:01,680
You'll have, you
know, 10 charts that

830
00:41:01,680 --> 00:41:03,930
look identical except
for a couple of numbers,

831
00:41:03,930 --> 00:41:07,590
like the exact flap position,
whether the anti-icing is

832
00:41:07,590 --> 00:41:08,250
on or off.

833
00:41:11,220 --> 00:41:13,330
The Piper Warrior
POH is a lot simpler,

834
00:41:13,330 --> 00:41:15,180
and that's some of
the charts we're

835
00:41:15,180 --> 00:41:19,260
going to cover in addition to
some of the anonymous airplane

836
00:41:19,260 --> 00:41:22,500
charts that the FAA
gives you with the test.

837
00:41:22,500 --> 00:41:25,140
So one thing to remember if
you're a renter, in addition

838
00:41:25,140 --> 00:41:28,410
to the fact that you want to
build in maybe some charter

839
00:41:28,410 --> 00:41:31,290
and airline minimums
into your flying,

840
00:41:31,290 --> 00:41:33,390
is that all those numbers
were with the brand

841
00:41:33,390 --> 00:41:36,180
new airplane that was
perfectly straight

842
00:41:36,180 --> 00:41:38,870
and had a perfect engine.

843
00:41:38,870 --> 00:41:42,300
OK, so wind components.

844
00:41:42,300 --> 00:41:44,580
You're going to get a
shorter takeoff and landing

845
00:41:44,580 --> 00:41:47,300
distances with a headwind.

846
00:41:47,300 --> 00:41:49,260
A tailwind, actually,
it may not be

847
00:41:49,260 --> 00:41:51,240
legal to operate
a high performance

848
00:41:51,240 --> 00:41:53,533
aircraft on a runway
with a tailwind of more

849
00:41:53,533 --> 00:41:54,450
than a certain amount.

850
00:41:54,450 --> 00:41:56,220
I think for the c.r.

851
00:41:56,220 --> 00:41:57,030
It was 10 knots.

852
00:41:57,030 --> 00:42:03,000
We just simply could not land
with a 10 knot tailwind or more

853
00:42:03,000 --> 00:42:05,040
than a 10 knot tailwind.

854
00:42:05,040 --> 00:42:09,088
Crosswind is a
little bit different.

855
00:42:09,088 --> 00:42:11,130
You'll get a max demonstrated
crosswind component

856
00:42:11,130 --> 00:42:11,850
in the manual.

857
00:42:11,850 --> 00:42:14,760
So it'll tell you a
test pilot managed

858
00:42:14,760 --> 00:42:17,520
to hold this airplane straight
on the runway with full flaps,

859
00:42:17,520 --> 00:42:23,280
or whatever the normal landing
configuration is, and there

860
00:42:23,280 --> 00:42:28,380
was enough rudder to land
with a 15 knot crosswind.

861
00:42:28,380 --> 00:42:30,180
So that's max demonstrated.

862
00:42:30,180 --> 00:42:31,800
It's not a limitation.

863
00:42:31,800 --> 00:42:35,550
So if it is, it'll say,
this is a limitation.

864
00:42:35,550 --> 00:42:39,000
But max demonstrated just
means a test pilot did it.

865
00:42:39,000 --> 00:42:42,540
It'll probably work for
you too if you manipulate

866
00:42:42,540 --> 00:42:44,280
the controls in the same way.

867
00:42:44,280 --> 00:42:47,160
And beyond that,
you can't be sure.

868
00:42:47,160 --> 00:42:51,000
So one thing that
people will do is

869
00:42:51,000 --> 00:42:56,440
they will adjust the
flap amount to have--

870
00:42:56,440 --> 00:42:59,670
a reduced use of flaps
in a heavy crosswind,

871
00:42:59,670 --> 00:43:01,350
that keeps the airspeed up.

872
00:43:01,350 --> 00:43:02,853
You will chew up more runway.

873
00:43:02,853 --> 00:43:04,770
But when the wheels
actually touch the ground,

874
00:43:04,770 --> 00:43:09,338
the wheels provide a little
bit of stabilization and help

875
00:43:09,338 --> 00:43:11,130
keep you from getting
blown off the runway.

876
00:43:11,130 --> 00:43:16,810
You're going to see tomorrow
Dojo from the Brazilian Air

877
00:43:16,810 --> 00:43:21,030
Force is going to tell you about
testing the various airplanes,

878
00:43:21,030 --> 00:43:25,980
but especially the Super Tucano,
in very heavy crosswinds down

879
00:43:25,980 --> 00:43:27,900
there in South America.

880
00:43:27,900 --> 00:43:29,820
They have some
pretty heavy winds.

881
00:43:29,820 --> 00:43:31,782
I think they went
to Chile to do that.

882
00:43:31,782 --> 00:43:32,490
I could be wrong.

883
00:43:32,490 --> 00:43:35,770
Or maybe it was just right
next to the Andes in Brazil.

884
00:43:35,770 --> 00:43:38,310
OK, crosswind chart.

885
00:43:38,310 --> 00:43:46,650
So this here shows you that, if
you have a 40 knot wind at a 30

886
00:43:46,650 --> 00:43:51,510
degree angle, you go over here
on the chart to the 30 degree

887
00:43:51,510 --> 00:44:00,030
line, you use this 40
knot ring, and then

888
00:44:00,030 --> 00:44:04,050
you can find that it's a 35
knot headwind and a 20 knot

889
00:44:04,050 --> 00:44:04,650
crosswind.

890
00:44:04,650 --> 00:44:06,780
Does that make sense?

891
00:44:06,780 --> 00:44:08,640
I will tell you when
I was getting a type

892
00:44:08,640 --> 00:44:11,430
rating for this Cessna
Mustang flight safety,

893
00:44:11,430 --> 00:44:14,220
there were a couple of
Boeing 737 pilots there,

894
00:44:14,220 --> 00:44:16,410
and they had no idea
how to use this chart.

895
00:44:16,410 --> 00:44:18,740
And they couldn't even
give the right answers.

896
00:44:18,740 --> 00:44:23,610
If you said, you know,
you're landing on runway 27

897
00:44:23,610 --> 00:44:27,690
and the wind's coming
from 315, is that

898
00:44:27,690 --> 00:44:29,880
a tailwind or a headwind?

899
00:44:29,880 --> 00:44:33,290
And they couldn't answer
that question either.

900
00:44:33,290 --> 00:44:36,640
Basically, all they do is
go from towered airport

901
00:44:36,640 --> 00:44:37,560
to towered airport.

902
00:44:37,560 --> 00:44:40,212
The tower tells them
what runway to use.

903
00:44:40,212 --> 00:44:41,670
They are from the
Philippines, so I

904
00:44:41,670 --> 00:44:43,900
guess it's not
insanely windy there

905
00:44:43,900 --> 00:44:46,020
like it would be in Argentina.

906
00:44:46,020 --> 00:44:49,170
I once landed in
Argentina in Ushuaia

907
00:44:49,170 --> 00:44:52,860
on a commercial airline
flight, and it was 50 knot--

908
00:44:52,860 --> 00:44:56,400
the wind was, I
think, 35 gusting 50.

909
00:44:56,400 --> 00:45:00,102
And the pilots, you know, I
talked to them afterwards.

910
00:45:00,102 --> 00:45:01,560
They said it was
just a normal day.

911
00:45:01,560 --> 00:45:05,160
They wouldn't even bother
talking about that.

912
00:45:05,160 --> 00:45:09,330
So anyway, these
skills apparently rest.

913
00:45:09,330 --> 00:45:11,760
I'm sure those guys, you know,
had used a chart like that

914
00:45:11,760 --> 00:45:13,710
at one point in their training.

915
00:45:13,710 --> 00:45:16,102
They did get their type
rating, so the good news

916
00:45:16,102 --> 00:45:18,060
is you can get your type
rating without knowing

917
00:45:18,060 --> 00:45:19,030
how to use that.

918
00:45:19,030 --> 00:45:20,655
OK, here's one of
the FAA charts.

919
00:45:20,655 --> 00:45:22,280
This is what they
give you on the test.

920
00:45:22,280 --> 00:45:25,620
It's a lot easier
to use than the POH.

921
00:45:25,620 --> 00:45:26,560
Here's a problem.

922
00:45:26,560 --> 00:45:29,250
They're giving you
an example problem.

923
00:45:29,250 --> 00:45:29,820
Let's see.

924
00:45:29,820 --> 00:45:33,750
We're at somewhere in Colorado,
apparently 5,650 feet.

925
00:45:33,750 --> 00:45:36,270
We weigh 2,950 pounds
in this airplane

926
00:45:36,270 --> 00:45:38,250
that they won't
tell us what it is.

927
00:45:38,250 --> 00:45:43,230
It's nine knots of headwind.

928
00:45:43,230 --> 00:45:44,730
Notice these
associated conditions.

929
00:45:44,730 --> 00:45:46,230
These are really critical.

930
00:45:46,230 --> 00:45:48,780
And again, if they give you
a choice of multiple charts,

931
00:45:48,780 --> 00:45:49,890
that's where the trick is.

932
00:45:49,890 --> 00:45:53,130
You know, they're trying to
get you to use the wrong chart.

933
00:45:53,130 --> 00:45:56,380
That's more on the AP exam
than on the private one.

934
00:45:56,380 --> 00:46:01,960
But yeah, see here, powerful
throttle, cowl flaps are open.

935
00:46:01,960 --> 00:46:07,590
This is some kind of
more complicated plane,

936
00:46:07,590 --> 00:46:10,440
that you got the right mixture
set even before you take off

937
00:46:10,440 --> 00:46:11,910
for high altitude.

938
00:46:11,910 --> 00:46:15,100
All right, so what
do we got here?

939
00:46:15,100 --> 00:46:17,767
We got temperature of 15.

940
00:46:17,767 --> 00:46:19,350
We go up to the air
pressure altitude,

941
00:46:19,350 --> 00:46:21,162
pretty close to 6,000.

942
00:46:21,162 --> 00:46:22,620
We come over here,
we're apparently

943
00:46:22,620 --> 00:46:24,787
right at gross weight, so
at least that's realistic.

944
00:46:24,787 --> 00:46:30,840
Most aircraft take off right at
gross weight for most flights.

945
00:46:30,840 --> 00:46:32,730
There's nine knots
of wind, so that's

946
00:46:32,730 --> 00:46:35,830
going to subtract a little bit
from our runway requirements.

947
00:46:35,830 --> 00:46:41,240
And here we can see it's
1,500 feet of ground roll

948
00:46:41,240 --> 00:46:42,920
and a little over--

949
00:46:42,920 --> 00:46:44,645
what is that, 2,300?

950
00:46:44,645 --> 00:46:47,000
Yeah, 2,300 to clear
the 50 foot obstacle.

951
00:46:47,000 --> 00:46:48,500
So these charts are
not hard to use.

952
00:46:48,500 --> 00:46:52,550
And in the real world,
maybe in the FAA figure,

953
00:46:52,550 --> 00:46:54,050
they actually give
you this example.

954
00:46:54,050 --> 00:46:56,450
So you can see how it's
done and then, you know,

955
00:46:56,450 --> 00:46:59,190
you just draw the lines
in a different place.

956
00:46:59,190 --> 00:47:01,350
So they're not
trying to trick you.

957
00:47:01,350 --> 00:47:04,610
Here's a chart for
the Pilatus PC-12.

958
00:47:04,610 --> 00:47:06,490
There's also apps
to do it, which

959
00:47:06,490 --> 00:47:10,300
I'll show you a
little bit later,

960
00:47:10,300 --> 00:47:12,700
similar to that Piper
chart we saw earlier

961
00:47:12,700 --> 00:47:15,700
where you calculate the density
altitude without realizing

962
00:47:15,700 --> 00:47:18,650
that you've calculated it.

963
00:47:18,650 --> 00:47:20,660
Yeah, so here you've
got pressure altitude

964
00:47:20,660 --> 00:47:22,670
and temperature, and
you're implicitly

965
00:47:22,670 --> 00:47:24,620
calculating density altitude.

966
00:47:24,620 --> 00:47:26,042
Then you go over to weight.

967
00:47:26,042 --> 00:47:26,750
Look at this one.

968
00:47:26,750 --> 00:47:30,730
The Pilatus guys, I think
they are having some fun here.

969
00:47:30,730 --> 00:47:33,580
They're saying you're
taking off at 7,000 pounds.

970
00:47:33,580 --> 00:47:39,400
So you're missing almost 3,000
pounds of people and bags.

971
00:47:39,400 --> 00:47:41,290
You paid all this
money for this airplane

972
00:47:41,290 --> 00:47:43,643
and you're barely using it.

973
00:47:43,643 --> 00:47:46,060
So I don't think that happens
too often unless you've just

974
00:47:46,060 --> 00:47:49,470
dropped everybody off at
an airport with no fuel

975
00:47:49,470 --> 00:47:50,572
and you're repositioning.

976
00:47:50,572 --> 00:47:52,030
Anyway, so you've
got the headwind.

977
00:47:52,030 --> 00:47:54,655
They've got uphill and downhill
all baked into this nice chart.

978
00:47:54,655 --> 00:47:56,620
You can get all
these good numbers.

979
00:47:56,620 --> 00:48:00,570
This is why Cirrus is better,
why they're the best seller.

980
00:48:00,570 --> 00:48:02,433
They just say, look,
here is this table.

981
00:48:02,433 --> 00:48:03,850
There's a few
corrections that you

982
00:48:03,850 --> 00:48:07,490
can use if you want to up
there in the upper right

983
00:48:07,490 --> 00:48:09,890
for headwind, tailwind, grass.

984
00:48:09,890 --> 00:48:13,400
But basically, they make
the usual case very simple

985
00:48:13,400 --> 00:48:17,540
of a level runway,
a paved runway.

986
00:48:17,540 --> 00:48:20,210
It's always more
conservative to go more.

987
00:48:20,210 --> 00:48:21,950
You know, you don't
have to interpolate.

988
00:48:21,950 --> 00:48:24,450
You can just say,
well, it's 25 degrees,

989
00:48:24,450 --> 00:48:26,360
so I'll use the
30 degree number.

990
00:48:31,790 --> 00:48:36,210
OK, what is the
rate of climb here?

991
00:48:36,210 --> 00:48:39,630
We're in a gross
weight of 1,670 pounds.

992
00:48:39,630 --> 00:48:42,290
It's 2,000 feet.

993
00:48:42,290 --> 00:48:44,190
How do we figure that out?

994
00:48:44,190 --> 00:48:47,810
This is one of the
FAA example tables,

995
00:48:47,810 --> 00:48:52,850
and it's as simple as finding
the right row in the table, row

996
00:48:52,850 --> 00:48:55,230
and column in the table.

997
00:48:55,230 --> 00:48:56,510
Or actually, have a look here.

998
00:48:56,510 --> 00:48:58,135
So they're saying
the mixture has to be

999
00:48:58,135 --> 00:48:59,410
lean to get these numbers.

1000
00:48:59,410 --> 00:49:00,490
The flaps have to be up.

1001
00:49:00,490 --> 00:49:01,907
You've got to be
at full throttle.

1002
00:49:05,830 --> 00:49:07,810
OK, same deal,
max rate of climb.

1003
00:49:07,810 --> 00:49:09,931
I forget if this a--

1004
00:49:09,931 --> 00:49:14,090
this might be a
paper chart, but you

1005
00:49:14,090 --> 00:49:15,950
can see that associated
conditions up there

1006
00:49:15,950 --> 00:49:17,150
in the top left.

1007
00:49:17,150 --> 00:49:20,560
That's absolutely critical.

1008
00:49:20,560 --> 00:49:22,030
You know, The gross weight--

1009
00:49:22,030 --> 00:49:24,640
Cirrus, actually, a lot
of the performance numbers

1010
00:49:24,640 --> 00:49:29,470
in the Cirrus for cruise
speed are at 2,600 pounds

1011
00:49:29,470 --> 00:49:34,070
and you're flying along at 2,950
because you took off at 3,000.

1012
00:49:34,070 --> 00:49:36,580
You're wondering, how come
I'm not getting these numbers?

1013
00:49:36,580 --> 00:49:41,420
But of course, you know,
they're being optimistic about--

1014
00:49:41,420 --> 00:49:43,420
they're putting their
airplane in the best light

1015
00:49:43,420 --> 00:49:46,510
by positing some
weight that probably

1016
00:49:46,510 --> 00:49:48,430
doesn't exist in real life.

1017
00:49:48,430 --> 00:49:53,230
All right, here they give us an
example of 5,000 feet pressure

1018
00:49:53,230 --> 00:50:01,410
altitude, OAT of 16 degrees, so
ISA plus 11, max rate of climb,

1019
00:50:01,410 --> 00:50:02,950
374.

1020
00:50:02,950 --> 00:50:06,300
So I guess, yeah, 5,000 feet.

1021
00:50:06,300 --> 00:50:07,390
Here's ISA plus 11.

1022
00:50:07,390 --> 00:50:12,040
It says 376 with some kind
of elaborate interpolation.

1023
00:50:12,040 --> 00:50:14,680
I guess you find that last
couple feet per minute

1024
00:50:14,680 --> 00:50:15,430
that you subtract.

1025
00:50:19,390 --> 00:50:20,590
Here's cruise charts.

1026
00:50:20,590 --> 00:50:23,725
I think, again, this is from
the FAA test supplement.

1027
00:50:23,725 --> 00:50:25,600
They're just giving
you-- remember I told you

1028
00:50:25,600 --> 00:50:27,160
it would be ISA minus 20?

1029
00:50:27,160 --> 00:50:28,380
That's the chart on the left.

1030
00:50:28,380 --> 00:50:30,410
The one in the middle
is the standard day.

1031
00:50:30,410 --> 00:50:34,460
And on the right is a
summer day, ISA plus 20.

1032
00:50:34,460 --> 00:50:40,210
Notice that they'll give you
fuel flow and the true airspeed

1033
00:50:40,210 --> 00:50:43,340
given various engine speed and
manifold pressure settings.

1034
00:50:43,340 --> 00:50:46,800
This looks like it's
for a piston twin.

1035
00:50:46,800 --> 00:50:50,008
OK, landing performance is a
pretty similar kind of chart.

1036
00:50:50,008 --> 00:50:51,550
Not going to go
through this exactly,

1037
00:50:51,550 --> 00:50:54,580
but you can see they're
giving you the worked example.

1038
00:50:54,580 --> 00:50:56,720
And you come up with--

1039
00:50:56,720 --> 00:50:57,220
let's see.

1040
00:50:57,220 --> 00:51:02,270
It's going to be about a little
over 1,000 feet of ground

1041
00:51:02,270 --> 00:51:11,070
roll and 1,700 feet, they claim,
to clear a 50 foot obstacle.

1042
00:51:11,070 --> 00:51:13,540
Here's an FAA
question, actually.

1043
00:51:13,540 --> 00:51:14,308
So let's see.

1044
00:51:14,308 --> 00:51:16,350
Determine the total distance
required for takeoff

1045
00:51:16,350 --> 00:51:18,420
to clear a 50 foot obstacle.

1046
00:51:18,420 --> 00:51:21,990
Standard temperature, sea level.

1047
00:51:21,990 --> 00:51:23,700
So actually, this
is testing you.

1048
00:51:23,700 --> 00:51:25,470
This is pretty advanced, right?

1049
00:51:25,470 --> 00:51:30,070
They're saying it's the standard
temperature at sea level,

1050
00:51:30,070 --> 00:51:34,770
so you have to know
that it's 15 degrees.

1051
00:51:34,770 --> 00:51:44,700
We only weigh 2,700
pounds, so we're

1052
00:51:44,700 --> 00:51:50,190
going to have to ride down
this curve a little bit.

1053
00:51:50,190 --> 00:51:51,600
And the wind's
calm, so we're not

1054
00:51:51,600 --> 00:51:54,690
going to get any
boost from the wind.

1055
00:51:54,690 --> 00:51:56,870
So what do you guys think?

1056
00:51:56,870 --> 00:51:59,580
Have any of you been
able to kind of see

1057
00:51:59,580 --> 00:52:02,520
what the most likely number
is by following these?

1058
00:52:07,760 --> 00:52:10,560
Somebody says A?

1059
00:52:10,560 --> 00:52:11,510
Let's see.

1060
00:52:11,510 --> 00:52:13,350
It's a little bit lighter.

1061
00:52:13,350 --> 00:52:14,875
That kind of makes sense.

1062
00:52:14,875 --> 00:52:16,250
But on the other
hand, the wind's

1063
00:52:16,250 --> 00:52:19,980
calm, so we didn't get that
reduction from the wind.

1064
00:52:19,980 --> 00:52:20,682
Let's see.

1065
00:52:20,682 --> 00:52:22,140
So if we came down
here, it's going

1066
00:52:22,140 --> 00:52:28,270
to start from sea
level, 15 degrees.

1067
00:52:28,270 --> 00:52:29,080
Come over here.

1068
00:52:29,080 --> 00:52:36,640
Come down here over
a 50 foot obstacle,

1069
00:52:36,640 --> 00:52:37,600
then we have to go up.

1070
00:52:41,180 --> 00:52:43,300
Anybody want to
revise their estimate?

1071
00:52:43,300 --> 00:52:45,470
A, we heard A last time.

1072
00:52:45,470 --> 00:52:47,750
It seems a little short to
clear the 50 foot obstacle.

1073
00:52:47,750 --> 00:52:50,060
I agree with you that you'd
be well off the ground

1074
00:52:50,060 --> 00:52:54,418
by 1,000 feet.

1075
00:52:54,418 --> 00:52:54,918
Tada!

1076
00:52:57,720 --> 00:52:59,940
All right, obviously,
you know, if you

1077
00:52:59,940 --> 00:53:05,850
have a pencil and a little more
time to do that, it's easier.

1078
00:53:05,850 --> 00:53:07,660
That's kind of the hard way.

1079
00:53:07,660 --> 00:53:10,740
Let's look at the easy way.

1080
00:53:10,740 --> 00:53:13,620
Getting the runway numbers
for low performance aircraft,

1081
00:53:13,620 --> 00:53:16,140
it actually remains pretty
common to just use the POH.

1082
00:53:16,140 --> 00:53:18,233
People aren't usually
in a situation

1083
00:53:18,233 --> 00:53:19,650
where they have
to worry about it.

1084
00:53:19,650 --> 00:53:21,942
If you're going from Hanscom
Field or Martha's Vineyard

1085
00:53:21,942 --> 00:53:23,370
and back, you
know, both airports

1086
00:53:23,370 --> 00:53:26,730
are big enough for a
Boeing, and you're not

1087
00:53:26,730 --> 00:53:29,940
going to be carefully
calculating these numbers

1088
00:53:29,940 --> 00:53:33,060
unless you really don't
have much else to do.

1089
00:53:33,060 --> 00:53:36,263
Apps, though, are available even
for low performance aircraft,

1090
00:53:36,263 --> 00:53:37,930
and they're very
useful if you're going,

1091
00:53:37,930 --> 00:53:40,020
you know, into tighter
airports And you

1092
00:53:40,020 --> 00:53:43,350
might have to worry about that.

1093
00:53:43,350 --> 00:53:46,440
The time and fuel
stuff is everywhere

1094
00:53:46,440 --> 00:53:47,550
on the web and the apps.

1095
00:53:47,550 --> 00:53:50,572
But the actual runway numbers
are a little bit less common.

1096
00:53:50,572 --> 00:53:52,030
Let me show you a
couple of things.

1097
00:53:52,030 --> 00:53:53,190
Here's Gyronimo.

1098
00:53:55,870 --> 00:53:59,450
So they sell these for
different aircraft.

1099
00:53:59,450 --> 00:54:02,800
This is just off their website.

1100
00:54:02,800 --> 00:54:07,130
And for an SR22, you
can see you put in--

1101
00:54:07,130 --> 00:54:08,330
they must be European.

1102
00:54:08,330 --> 00:54:11,890
They say aircraft mass 3,359.

1103
00:54:11,890 --> 00:54:15,100
And you've got your temperature,
your takeoff elevation,

1104
00:54:15,100 --> 00:54:18,620
your altimeter,
runway conditions.

1105
00:54:18,620 --> 00:54:21,890
I don't know what
that plus 5% is.

1106
00:54:21,890 --> 00:54:26,370
Maybe they're saying-- oh, I
don't know if that's between--

1107
00:54:26,370 --> 00:54:28,960
is it half grass and half paved?

1108
00:54:28,960 --> 00:54:31,110
Anyway, you can put
in everything relevant

1109
00:54:31,110 --> 00:54:34,140
and it's going to tell
you how much ground roll

1110
00:54:34,140 --> 00:54:36,600
and how much takeoff distance.

1111
00:54:36,600 --> 00:54:37,770
So that's pretty slick.

1112
00:54:37,770 --> 00:54:42,500
It's a lot easier than
relying on the POH.

1113
00:54:42,500 --> 00:54:45,660
The calculator for
the Pilatus is free.

1114
00:54:45,660 --> 00:54:48,150
That's the good news.

1115
00:54:48,150 --> 00:54:50,970
And here, same deal.

1116
00:54:50,970 --> 00:54:55,650
You put in your weight,
the temperature,

1117
00:54:55,650 --> 00:54:58,380
if there's any headwind,
the airport elevation,

1118
00:54:58,380 --> 00:54:59,820
and you get the numbers.

1119
00:55:03,300 --> 00:55:10,110
All right, we can try to
get the doc camera working

1120
00:55:10,110 --> 00:55:11,390
for a demo in a minute here.

1121
00:55:11,390 --> 00:55:14,010
But in the meantime, first
of all, are there questions?

1122
00:55:14,010 --> 00:55:15,795
And secondly, what
is this aircraft?

1123
00:55:15,795 --> 00:55:16,920
And what's it designed for?

1124
00:55:20,315 --> 00:55:21,770
AUDIENCE: Question
about the test.

1125
00:55:21,770 --> 00:55:28,725
Will it be on the
[INAUDIBLE] for this class?

1126
00:55:28,725 --> 00:55:30,240
Because it's online, right?

1127
00:55:30,240 --> 00:55:31,240
PHILLIP GREENSPUN: Yeah.

1128
00:55:31,240 --> 00:55:32,650
Well, you can print out
the test supplement.

1129
00:55:32,650 --> 00:55:33,310
That's public.

1130
00:55:33,310 --> 00:55:34,270
It's in our Dropbox.

1131
00:55:34,270 --> 00:55:36,700
And also, the FAA makes this
chart supplement public,

1132
00:55:36,700 --> 00:55:38,450
so you can see all the
figures that you're

1133
00:55:38,450 --> 00:55:41,945
going to see before the test.

1134
00:55:41,945 --> 00:55:44,070
I think, actually, when
you're done with your test,

1135
00:55:44,070 --> 00:55:45,460
I think you can print
out all the questions

1136
00:55:45,460 --> 00:55:47,116
and it'll show you
what you got right.

1137
00:55:47,116 --> 00:55:47,658
AUDIENCE: OK.

1138
00:55:47,658 --> 00:55:50,665
Because for the grass, this
is going to be harder for me

1139
00:55:50,665 --> 00:55:51,290
to [INAUDIBLE].

1140
00:55:51,290 --> 00:55:51,940
PHILLIP GREENSPUN: Oh, yeah.

1141
00:55:51,940 --> 00:55:53,260
Yeah, just print out the chart.

1142
00:55:53,260 --> 00:55:55,793
Yeah, sure, another
chart supplement.

1143
00:55:59,212 --> 00:56:01,420
Anybody have any brilliant
ideas about this aircraft?

1144
00:56:07,650 --> 00:56:08,880
It says Grizz on it.

1145
00:56:12,233 --> 00:56:17,510
AUDIENCE: [INAUDIBLE]

1146
00:56:17,510 --> 00:56:19,970
PHILLIP GREENSPUN: That's a
Burt Rutan design, the climate

1147
00:56:19,970 --> 00:56:20,750
change denier.

1148
00:56:23,630 --> 00:56:27,620
And this is a super
short field airplane.

1149
00:56:27,620 --> 00:56:30,130
It actually doesn't land as
short as you might think.

1150
00:56:30,130 --> 00:56:31,880
I think it might be a
four-seater, though,

1151
00:56:31,880 --> 00:56:34,570
so I guess it is pretty darn
short for a four-seater.

1152
00:56:34,570 --> 00:56:37,280
But it has huge flaps
and a lot of wing area,

1153
00:56:37,280 --> 00:56:39,140
and it's got that--

1154
00:56:39,140 --> 00:56:41,040
I think it has ordinary--

1155
00:56:41,040 --> 00:56:45,220
Yeah, see, it has essentially
three surfaces right?

1156
00:56:45,220 --> 00:56:49,010
It's got kind of a
helper wing or a canard

1157
00:56:49,010 --> 00:56:52,700
out in front, the
regular wing, and then

1158
00:56:52,700 --> 00:56:54,650
an ordinary
conventional tail plane.

1159
00:56:59,460 --> 00:57:02,510
Let me see if I can get
this doc camera working.

1160
00:57:05,120 --> 00:57:08,190
All right, so let's say we want
to know how much fuel we're

1161
00:57:08,190 --> 00:57:09,600
going to use.

1162
00:57:09,600 --> 00:57:11,190
See that fuel pounds there?

1163
00:57:14,200 --> 00:57:15,160
Where is that?

1164
00:57:18,140 --> 00:57:23,740
Somewhere along here--
well, actually, I

1165
00:57:23,740 --> 00:57:29,470
happen to know it's got to be
somewhere-- we're 10 pounds.

1166
00:57:29,470 --> 00:57:31,720
Yeah, see, there's US
gallons right there.

1167
00:57:31,720 --> 00:57:33,730
So we line this up.

1168
00:57:33,730 --> 00:57:36,100
And you can tell this was
designed for piston folks,

1169
00:57:36,100 --> 00:57:37,750
because their idea
of fuel weight

1170
00:57:37,750 --> 00:57:41,440
is six pounds per gallon,
and jet fuel weighs 6.7.

1171
00:57:41,440 --> 00:57:43,690
But at this point, now we've
got our handy slide rule.

1172
00:57:43,690 --> 00:57:50,280
So we know, if we load on, for
example, 10 gallons of fuel,

1173
00:57:50,280 --> 00:57:53,600
it's going to be 60 pounds.

1174
00:57:53,600 --> 00:57:59,170
And the Cirrus holds
56 gallons, so that's

1175
00:57:59,170 --> 00:58:02,770
going to weigh 300 and--

1176
00:58:02,770 --> 00:58:04,640
looks like 345.

1177
00:58:04,640 --> 00:58:07,130
Oh, sorry, 335 gallons.

1178
00:58:07,130 --> 00:58:08,470
335 pounds.

1179
00:58:11,270 --> 00:58:18,290
More to the point, you can
calculate density altitude.

1180
00:58:18,290 --> 00:58:19,940
So over here, for
example, you can

1181
00:58:19,940 --> 00:58:24,050
say the pressure altitude is--

1182
00:58:24,050 --> 00:58:26,520
let's call it sea level.

1183
00:58:26,520 --> 00:58:28,160
And it's very hot, though.

1184
00:58:28,160 --> 00:58:29,850
It's plus 40 degrees.

1185
00:58:29,850 --> 00:58:32,240
So now you see the
density altitude up there

1186
00:58:32,240 --> 00:58:34,190
is about 2,000 feet.

1187
00:58:34,190 --> 00:58:36,050
Does that make sense?

1188
00:58:36,050 --> 00:58:39,980
So you've set the pressure
altitude at the bottom

1189
00:58:39,980 --> 00:58:42,330
or inside this little
window at zero,

1190
00:58:42,330 --> 00:58:44,900
and then the density
altitude gets read out here

1191
00:58:44,900 --> 00:58:49,350
after you line it up
with a temperature.

1192
00:58:49,350 --> 00:58:53,130
There's also something
that you can do, well,

1193
00:58:53,130 --> 00:58:54,460
just with the basic rate.

1194
00:58:54,460 --> 00:58:57,727
So let's say you decide that
you're going to be going--

1195
00:58:57,727 --> 00:58:59,310
this is more for
performance planning.

1196
00:58:59,310 --> 00:59:05,250
But let's say you're a Cirrus
and you're going 150 knots.

1197
00:59:05,250 --> 00:59:11,250
If you end up needing to go,
let's say, 300 nautical miles,

1198
00:59:11,250 --> 00:59:14,310
it tells you that'll
take you two hours.

1199
00:59:14,310 --> 00:59:20,290
Not too exciting, but the wind
side is a little more exciting.

1200
00:59:20,290 --> 00:59:23,597
I'll bring a pencil tomorrow
for the flight planning talk

1201
00:59:23,597 --> 00:59:25,680
and we can play around
with wind vectors on there.

1202
00:59:25,680 --> 00:59:27,870
But anyway, fortunately,
a lot of this stuff

1203
00:59:27,870 --> 00:59:29,160
is explained in the book.

1204
00:59:29,160 --> 00:59:32,580
You guys are free to come up
and play around with it anytime.

1205
00:59:32,580 --> 00:59:37,250
There's a temperature conversion
scale here on the bottom.

1206
00:59:37,250 --> 00:59:39,470
And it's a fun toy.

1207
00:59:39,470 --> 00:59:43,110
Tina, anything else that
we should cover here?

1208
00:59:43,110 --> 00:59:44,070
Or should be segue?

1209
00:59:44,070 --> 00:59:45,400
What's the next--

1210
00:59:45,400 --> 00:59:46,750
TINA SRIVASTAVA: So we're
going to take questions,

1211
00:59:46,750 --> 00:59:48,656
and then there's a short
break, and then weather data.

1212
00:59:48,656 --> 00:59:50,970
PHILLIP GREENSPUN: OK, the
next one's weather data.

1213
00:59:50,970 --> 00:59:54,000
You'll need a
break for that one.

1214
00:59:54,000 --> 00:59:56,080
That's how you find
out all this stuff.

1215
00:59:56,080 --> 00:59:58,050
Let me go back to the PC.

1216
00:59:58,050 --> 01:00:01,660
Who else has questions?

1217
01:00:01,660 --> 01:00:03,473
AUDIENCE: Can you
go [INAUDIBLE]??

1218
01:00:06,877 --> 01:00:09,210
PHILLIP GREENSPUN: Go back
over and look at a POH graph?

1219
01:00:09,210 --> 01:00:09,930
AUDIENCE: Yeah.

1220
01:00:09,930 --> 01:00:11,610
PHILLIP GREENSPUN: Which one?

1221
01:00:11,610 --> 01:00:13,640
You want to do with
the FAA exam ones?

1222
01:00:13,640 --> 01:00:15,417
AUDIENCE: Yeah, the last one.

1223
01:00:15,417 --> 01:00:17,250
PHILLIP GREENSPUN: Lane
landing performance,

1224
01:00:17,250 --> 01:00:19,470
or this one from
the actual test?

1225
01:00:19,470 --> 01:00:20,637
AUDIENCE: Yeah, [INAUDIBLE].

1226
01:00:20,637 --> 01:00:21,803
PHILLIP GREENSPUN: This one?

1227
01:00:21,803 --> 01:00:23,110
AUDIENCE: Yeah.

1228
01:00:23,110 --> 01:00:25,140
PHILLIP GREENSPUN: OK,
so I don't think they

1229
01:00:25,140 --> 01:00:26,940
ever give it worked out for you.

1230
01:00:29,880 --> 01:00:34,210
Let me switch to the
laser pointer mode.

1231
01:00:34,210 --> 01:00:37,110
OK, so what do they tell us?

1232
01:00:37,110 --> 01:00:38,990
They told us it was
standard and sea level.

1233
01:00:38,990 --> 01:00:40,907
That's the one part of
the standard atmosphere

1234
01:00:40,907 --> 01:00:43,270
that people, I think,
are expected to remember,

1235
01:00:43,270 --> 01:00:46,600
that at sea level it should
be 15 degrees Celsius.

1236
01:00:46,600 --> 01:00:48,240
So we come down here.

1237
01:00:48,240 --> 01:00:50,310
We say it's 15 degrees out.

1238
01:00:50,310 --> 01:00:53,670
We're going to hit the sea
level pressure altitude.

1239
01:00:53,670 --> 01:00:57,090
We're going to slide over this
way, just like in the example.

1240
01:00:59,760 --> 01:01:05,490
And then we're going to slide
down, following this curve,

1241
01:01:05,490 --> 01:01:07,590
to 2,700 pounds.

1242
01:01:07,590 --> 01:01:11,320
And we're going to go
over here, and we're going

1243
01:01:11,320 --> 01:01:12,620
to say, look, there's no wind.

1244
01:01:12,620 --> 01:01:16,720
The wind's calm, so we'll
keep going over here,

1245
01:01:16,720 --> 01:01:23,360
and we find that we need about
a little less than 1,000 feet,

1246
01:01:23,360 --> 01:01:27,932
maybe 800 feet,
for a ground roll.

1247
01:01:27,932 --> 01:01:30,140
But to clear the 50 foot
obstacle, look at the bottom

1248
01:01:30,140 --> 01:01:31,040
there.

1249
01:01:31,040 --> 01:01:33,650
We need to go up, following
one of these lines,

1250
01:01:33,650 --> 01:01:37,190
and that's how we get
to the 1,400 number.

1251
01:01:37,190 --> 01:01:40,280
Did that help?

1252
01:01:40,280 --> 01:01:42,590
You still look a
little bit skeptical.

1253
01:01:42,590 --> 01:01:45,920
AUDIENCE: Yeah, it just doesn't
look like that line [INAUDIBLE]

1254
01:01:45,920 --> 01:01:47,540
PHILLIP GREENSPUN:
Well, remember, we

1255
01:01:47,540 --> 01:01:50,882
would be doing this
with a virtual pencil.

1256
01:01:50,882 --> 01:01:52,340
These lines are
just for reference,

1257
01:01:52,340 --> 01:01:55,670
telling you kind of what slope
to follow with your pencil.

1258
01:01:55,670 --> 01:02:02,980
So it's not like these are
the only available points.

1259
01:02:02,980 --> 01:02:05,560
So it's not like it's going to
be either this for the answer,

1260
01:02:05,560 --> 01:02:07,560
or this for the answer,
or this for your answer.

1261
01:02:07,560 --> 01:02:08,970
Even in their
worked example, you

1262
01:02:08,970 --> 01:02:12,340
can see their red line for
the answer is just parallel

1263
01:02:12,340 --> 01:02:16,780
to that gray line.

1264
01:02:16,780 --> 01:02:19,010
They're not picking
one of the gray lines.

1265
01:02:19,010 --> 01:02:21,640
So they're guidelines
for how you should

1266
01:02:21,640 --> 01:02:25,910
move your pencil in each phase.

1267
01:02:25,910 --> 01:02:28,210
I hope this motivates you
to buy that Gyronimo app.

1268
01:02:28,210 --> 01:02:30,363
It certainly would
motivate me to do it.

1269
01:02:30,363 --> 01:02:32,780
TINA SRIVASTAVA: If you want
to look at it on a real book,

1270
01:02:32,780 --> 01:02:39,890
I'll pass around-- again,
this is my POH for Cessna 172.

1271
01:02:39,890 --> 01:02:41,930
So this might be
the type of plane

1272
01:02:41,930 --> 01:02:45,020
that you're using as
your training aircraft.

1273
01:02:45,020 --> 01:02:47,540
And I have a couple
of pages that are

1274
01:02:47,540 --> 01:02:49,280
marked with a piece of paper.

1275
01:02:49,280 --> 01:02:53,360
So one talks about how you
calculate the takeoff distance.

1276
01:02:53,360 --> 01:02:54,815
And one is weight and balance.

1277
01:02:54,815 --> 01:02:56,690
We'll actually have a
whole section dedicated

1278
01:02:56,690 --> 01:02:57,740
to weight and balance.

1279
01:02:57,740 --> 01:02:59,720
But just to give
you a sense of how

1280
01:02:59,720 --> 01:03:02,030
you can follow with your
pencil, and you'll actually

1281
01:03:02,030 --> 01:03:05,840
see some pencil markings
of my own fairly

1282
01:03:05,840 --> 01:03:09,920
close to the limits here of
our center of gravity moment

1283
01:03:09,920 --> 01:03:11,970
envelope here, but
still within the box,

1284
01:03:11,970 --> 01:03:14,240
so just to give you an
idea of how you can do that

1285
01:03:14,240 --> 01:03:18,165
with a real paper and pencil.

1286
01:03:18,165 --> 01:03:19,139
AUDIENCE: Yeah.

1287
01:03:19,139 --> 01:03:34,390
[INAUDIBLE] So within that
[INAUDIBLE] Is that the reason?

1288
01:03:34,390 --> 01:03:35,390
PHILLIP GREENSPUN: Yeah.

1289
01:03:35,390 --> 01:03:40,280
So the question is, you know, we
don't have any kind of readout

1290
01:03:40,280 --> 01:03:42,940
in the aircraft for
density altitude.

1291
01:03:42,940 --> 01:03:45,450
So is that why we're always
calculating with our handy E6B

1292
01:03:45,450 --> 01:03:49,380
or listening to the
ASOS or whatever?

1293
01:03:49,380 --> 01:03:49,880
So, yeah.

1294
01:03:49,880 --> 01:03:51,880
Yeah, basically your
instruments in the aircraft

1295
01:03:51,880 --> 01:03:55,760
can tell you the temperature,
outside air temperature,

1296
01:03:55,760 --> 01:03:58,280
maybe not quite as accurate
as the one from the airport

1297
01:03:58,280 --> 01:03:59,750
if you're on the ground.

1298
01:03:59,750 --> 01:04:02,540
And they can also show you,
if you set your altimeter

1299
01:04:02,540 --> 01:04:07,730
to two niner niner two, you
can see the pressure altitude.

1300
01:04:07,730 --> 01:04:10,300
But the relationship between
the two is not simple.

1301
01:04:10,300 --> 01:04:13,310
And there's nothing onboard
the aircraft conventionally

1302
01:04:13,310 --> 01:04:14,730
that will calculate it for you.

1303
01:04:14,730 --> 01:04:16,230
And I don't think
that's quite true.

1304
01:04:16,230 --> 01:04:17,960
I think a lot of
modern GPS boxes

1305
01:04:17,960 --> 01:04:19,760
will do that
calculation for you.

1306
01:04:23,340 --> 01:04:25,140
But you have to type
in all the numbers.

1307
01:04:25,140 --> 01:04:27,170
They don't usually just grab it.

1308
01:04:27,170 --> 01:04:29,630
They will give you things
like true air speed.

1309
01:04:29,630 --> 01:04:31,130
They'll definitely
calculate that.

1310
01:04:31,130 --> 01:04:33,703
So if you're indicating 150
but you're up really high,

1311
01:04:33,703 --> 01:04:35,120
they'll tell you,
well, now you're

1312
01:04:35,120 --> 01:04:37,308
going 200 knots
in true air speed,

1313
01:04:37,308 --> 01:04:39,350
and then they'll give you
your ground speed, too.

1314
01:04:39,350 --> 01:04:41,360
And they'll even show
you with a wind vector.

1315
01:04:44,678 --> 01:04:46,220
TINA SRIVASTAVA:
Any other questions?

1316
01:04:50,370 --> 01:04:50,870
OK, great.

1317
01:04:50,870 --> 01:04:53,180
So we'll just take
a 10 minute break

1318
01:04:53,180 --> 01:04:56,360
and start up again at
2:15 with weather data.

1319
01:04:56,360 --> 01:04:58,640
And that's the one you guys
seem to keep asking about,

1320
01:04:58,640 --> 01:05:01,130
so we'll talk about
also, towards the end

1321
01:05:01,130 --> 01:05:05,890
of that talk, how you build
your own ADS-B receiver.