WEBVTT 00:00:15.642 --> 00:00:17.100 PHILLIP GREENSPUN: All right, we're 00:00:17.100 --> 00:00:21.370 going to talk about aircraft performance, which 00:00:21.370 --> 00:00:26.660 is figuring out all of this stuff 00:00:26.660 --> 00:00:28.240 if you're an airplane, basically, 00:00:28.240 --> 00:00:30.634 how much runway you're going to use on both ends, 00:00:30.634 --> 00:00:32.509 how long it's going to take you to get there, 00:00:32.509 --> 00:00:34.634 which is another way of saying how much fuel you're 00:00:34.634 --> 00:00:36.040 going to use. 00:00:36.040 --> 00:00:38.770 If it's a helicopter, it's a little bit different. 00:00:38.770 --> 00:00:42.170 Mostly, you're worried about hover performance. 00:00:42.170 --> 00:00:45.282 So if you're going to a friend's house, 00:00:45.282 --> 00:00:47.740 are you going to be able to park the helicopter in midair-- 00:00:47.740 --> 00:00:49.870 that's called an out of ground effect hover-- 00:00:49.870 --> 00:00:55.660 and very slowly descend into the backyard, dodging the trees 00:00:55.660 --> 00:00:57.920 and power lines and anything else? 00:00:57.920 --> 00:00:59.740 So these are all things that can be 00:00:59.740 --> 00:01:03.040 found in the aircraft manuals. 00:01:03.040 --> 00:01:06.940 And the FAA will test you on them a little bit. 00:01:06.940 --> 00:01:09.060 This is important partly because you 00:01:09.060 --> 00:01:13.590 want to be able to complete your flight safely, and also because 00:01:13.590 --> 00:01:18.030 of FAR 91.103, which is that, before you do a flight, 00:01:18.030 --> 00:01:20.640 you've got to become a-- 00:01:20.640 --> 00:01:24.600 it's pretty all-embracing, all-available information 00:01:24.600 --> 00:01:28.470 concerning weather, and aircraft performance, how the aircraft's 00:01:28.470 --> 00:01:32.640 going to perform given the altitude of where you're going, 00:01:32.640 --> 00:01:38.040 and the temperature that's prevailing there at the time. 00:01:38.040 --> 00:01:39.480 Wind also, you know? 00:01:39.480 --> 00:01:43.440 If you find out that there's a 40 knot wind scheduled 00:01:43.440 --> 00:01:46.680 for where you're going and it's a direct crosswind 00:01:46.680 --> 00:01:48.940 to the only runway, then that might 00:01:48.940 --> 00:01:52.940 to cause you to choose a different airport. 00:01:52.940 --> 00:01:59.370 OK, here's a reminder of the thrust and drag. 00:01:59.370 --> 00:02:01.530 Whenever you're generating lift, you're 00:02:01.530 --> 00:02:03.300 also generating some drag. 00:02:03.300 --> 00:02:06.400 And that's lifting the unwanted direction of backwards, 00:02:06.400 --> 00:02:06.900 usually. 00:02:09.720 --> 00:02:15.210 So the aircraft is also producing a parasitic drag 00:02:15.210 --> 00:02:18.570 by trying to punch its way through this vicious fluid 00:02:18.570 --> 00:02:21.540 of air. 00:02:21.540 --> 00:02:26.400 Where these summed up drag curves 00:02:26.400 --> 00:02:31.750 intersect is pretty much the bottom 00:02:31.750 --> 00:02:35.635 of the total drag curve, the minimum drag, or L over D max. 00:02:38.830 --> 00:02:44.030 The climb performance, the best speeds to go 00:02:44.030 --> 00:02:46.790 are all kind of tied into this drag curve. 00:02:49.400 --> 00:02:52.850 And the best angle of climb is what you use. 00:02:52.850 --> 00:02:55.880 That's a slower airspeed and the best rate of climb. 00:02:55.880 --> 00:02:57.380 If you're in a small airport, trying 00:02:57.380 --> 00:02:59.420 to clear the trees at the end of the runway, 00:02:59.420 --> 00:03:02.750 you're going to fly Vx, the best angle of climb. 00:03:02.750 --> 00:03:04.310 This is one of those few V speeds 00:03:04.310 --> 00:03:07.700 that you're actually expected to know the abbreviation for. 00:03:07.700 --> 00:03:11.780 And if you're going to just take off out of a big airport, 00:03:11.780 --> 00:03:13.730 like Hanscom Field, and just want 00:03:13.730 --> 00:03:16.520 to get up to your cruising altitude reasonably quickly, 00:03:16.520 --> 00:03:18.060 then you-- 00:03:18.060 --> 00:03:18.560 hey. 00:03:18.560 --> 00:03:20.150 Thanks, Richard. 00:03:20.150 --> 00:03:23.090 Richard's a Mooney pilot. 00:03:23.090 --> 00:03:26.656 Made it to California many times. 00:03:26.656 --> 00:03:34.460 AUDIENCE: [INAUDIBLE] 00:03:34.460 --> 00:03:42.430 PHILLIP GREENSPUN: So if you actually look at the Vx, 00:03:42.430 --> 00:03:46.130 one thing to notice is that it all depends a bit on the wind. 00:03:46.130 --> 00:03:50.643 Let's say there's 100 knot wind blowing down the runway. 00:03:50.643 --> 00:03:52.310 You don't need to fly very fast in order 00:03:52.310 --> 00:03:54.102 to clear the trees at the end of the runway 00:03:54.102 --> 00:03:56.010 because you're basically already flying. 00:03:56.010 --> 00:03:58.680 And you can go straight up like a helicopter in terms 00:03:58.680 --> 00:04:01.100 of your path over the ground, whereas Vy, 00:04:01.100 --> 00:04:03.290 just to gain altitude, that doesn't depend 00:04:03.290 --> 00:04:05.732 at all on the prevailing wind. 00:04:05.732 --> 00:04:07.940 So if you're trying to clear something on the ground, 00:04:07.940 --> 00:04:08.648 the wind matters. 00:04:08.648 --> 00:04:10.540 A tail tailwind would be very destructive. 00:04:10.540 --> 00:04:12.950 It'll be pushing you towards the obstacle. 00:04:12.950 --> 00:04:15.200 And a headwind will be very helpful. 00:04:15.200 --> 00:04:16.880 Cruise climb, most of the time you 00:04:16.880 --> 00:04:19.880 don't actually push the airplane to these speeds. 00:04:19.880 --> 00:04:21.829 They're pretty far nose up, which 00:04:21.829 --> 00:04:24.830 is a little bit alarming to passengers. 00:04:24.830 --> 00:04:26.885 And it's harder to see over the nose, 00:04:26.885 --> 00:04:29.510 and the engine isn't getting as much cooling air at these lower 00:04:29.510 --> 00:04:30.600 speeds. 00:04:30.600 --> 00:04:35.660 So typically we'll fly about 10 knots faster in a GA airplane. 00:04:35.660 --> 00:04:41.300 So for the Cirrus, for example, 96 is the book Vy at sea level, 00:04:41.300 --> 00:04:46.120 and flying something like 105 knots is more conventional. 00:04:46.120 --> 00:04:48.980 The PC-12 climbs-- you know, it might 00:04:48.980 --> 00:04:52.167 be able to do 3,000 feet a minute at 120 knots. 00:04:52.167 --> 00:04:53.750 But if you're not in a desperate hurry 00:04:53.750 --> 00:04:57.410 to get up above the bumpy clouds or something, 00:04:57.410 --> 00:05:00.770 then 150 knots is more conventional. 00:05:00.770 --> 00:05:08.810 OK, so let's remember that you've got thrust and power. 00:05:08.810 --> 00:05:14.120 So the thrust is a force that lets 00:05:14.120 --> 00:05:16.880 you climb up over the trees. 00:05:16.880 --> 00:05:21.200 The power is thrust times the speed. 00:05:21.200 --> 00:05:27.120 And it's thrust operating over a period of time. 00:05:27.120 --> 00:05:29.810 So the more excess power you have, the higher the rate 00:05:29.810 --> 00:05:31.670 at which you can climb. 00:05:31.670 --> 00:05:35.000 Anyway, we'll see some more of that here. 00:05:35.000 --> 00:05:38.600 You've got a best glide ratio. 00:05:38.600 --> 00:05:42.350 If you want to get to the decent place to land 00:05:42.350 --> 00:05:48.230 and you've lost your engine, what's a good speed to fly? 00:05:48.230 --> 00:05:52.280 Well, L over D max is an excellent speed to fly, 00:05:52.280 --> 00:06:00.540 because that's where the lift over drag 00:06:00.540 --> 00:06:02.132 is at its highest point and you'll 00:06:02.132 --> 00:06:03.590 make the best time over the ground. 00:06:03.590 --> 00:06:06.600 Again, that has to be adjusted a little bit for wind. 00:06:06.600 --> 00:06:10.710 If you're going into 100 knot wind and the Cirrus best 00:06:10.710 --> 00:06:13.423 glide speed is 96 knots, that's not 00:06:13.423 --> 00:06:14.590 going to work out very well. 00:06:14.590 --> 00:06:16.590 You're not going to go anywhere over the ground. 00:06:23.370 --> 00:06:26.193 That's a photo that I took at the Newport Jazz Festival. 00:06:26.193 --> 00:06:27.610 I don't want to say self portrait. 00:06:30.470 --> 00:06:36.030 Anyway, weight has a huge factor on all these speeds, 00:06:36.030 --> 00:06:40.530 because actually a lot of them are related to angle of attack. 00:06:40.530 --> 00:06:42.870 And it certainly affects your performance. 00:06:42.870 --> 00:06:46.290 So everything about higher weight is pretty bad. 00:06:46.290 --> 00:06:54.880 Wind, you might think that a tailwind is always good. 00:06:54.880 --> 00:06:58.690 But really, the tailwind is only good for extending your cruise 00:06:58.690 --> 00:06:59.560 range. 00:06:59.560 --> 00:07:04.000 Everything else, pretty much, the headwind is better for. 00:07:04.000 --> 00:07:06.250 So think about the headwind. 00:07:06.250 --> 00:07:08.680 Again, think of these extreme cases. 00:07:08.680 --> 00:07:12.160 If you've got 100 knot wind right in your face, 00:07:12.160 --> 00:07:14.380 then you can fly without moving. 00:07:14.380 --> 00:07:17.830 That's basically a wind tunnel. 00:07:17.830 --> 00:07:20.110 OK, center of gravity. 00:07:20.110 --> 00:07:23.670 This is also a little bit counterintuitive. 00:07:23.670 --> 00:07:28.170 If you load the airplane up so that all the way to the back, 00:07:28.170 --> 00:07:30.930 and it's super nose up, and you're 00:07:30.930 --> 00:07:35.220 having to push the stick forward to keep the plane level, 00:07:35.220 --> 00:07:38.010 that actually is where you get your maximum performance. 00:07:38.010 --> 00:07:41.740 Everything is better about having an aft center of gravity 00:07:41.740 --> 00:07:44.850 with one exception, which is the stability of the handling 00:07:44.850 --> 00:07:46.320 of the aircraft. 00:07:46.320 --> 00:07:48.900 And obviously, if you load it up so much in the back 00:07:48.900 --> 00:07:50.800 that you can't push the nose over, 00:07:50.800 --> 00:07:53.400 that would be outside of the CG range, or well outside 00:07:53.400 --> 00:07:55.930 of this range, let's hope. 00:07:55.930 --> 00:07:58.710 Then you wouldn't even be able to control 00:07:58.710 --> 00:08:01.950 the aircraft because you can't get the nose down enough. 00:08:01.950 --> 00:08:05.640 So having that forward CG gives you more stability. 00:08:05.640 --> 00:08:09.425 That's where you're going to be when you're a student pilot. 00:08:09.425 --> 00:08:11.550 If you're in a four-seat aircraft and it's just you 00:08:11.550 --> 00:08:14.790 and the instructor in front and the back seats are empty, 00:08:14.790 --> 00:08:18.950 then it's pretty obvious that it's 00:08:18.950 --> 00:08:21.510 going to be a somewhat forward CG, because the aircraft is 00:08:21.510 --> 00:08:26.730 designed to hold at least some weight in the back seats. 00:08:26.730 --> 00:08:29.790 One thing you can do is sort of, just as a first approximation, 00:08:29.790 --> 00:08:31.260 you know, pay attention-- 00:08:31.260 --> 00:08:33.480 we're going to have a talk on weight and balance 00:08:33.480 --> 00:08:34.289 later from Tina. 00:08:34.289 --> 00:08:38.070 But just keep in mind that the aircraft is kind of designed 00:08:38.070 --> 00:08:40.440 for, you know, two adults in the front 00:08:40.440 --> 00:08:43.330 and maybe one adult in the back, or two kids in the back. 00:08:43.330 --> 00:08:45.330 So if you load it up that way, it's 00:08:45.330 --> 00:08:47.100 almost always going to work. 00:08:47.100 --> 00:08:52.020 If, on the other hand, you have a big, heavy friend 00:08:52.020 --> 00:08:56.970 and, you know, his other big heavy friend or his box 00:08:56.970 --> 00:08:59.805 of anvils, and the guy says, well, look, 00:08:59.805 --> 00:09:01.180 I just want to sleep in the back, 00:09:01.180 --> 00:09:03.630 I don't want to be up front and get distracted, 00:09:03.630 --> 00:09:06.110 and you're a lightweight person all by yourself 00:09:06.110 --> 00:09:09.330 from the front, you know, that's the situation where it's 00:09:09.330 --> 00:09:10.980 important to really do the calculations 00:09:10.980 --> 00:09:12.480 and think carefully about it. 00:09:12.480 --> 00:09:14.910 Because that wasn't something that Cessna and Piper 00:09:14.910 --> 00:09:18.590 were thinking about when they designed the aircraft. 00:09:18.590 --> 00:09:20.625 OK, atmospheric pressure. 00:09:24.420 --> 00:09:27.180 Remember we talked about how the atmosphere 00:09:27.180 --> 00:09:31.920 is going to be expanded when it's hot 00:09:31.920 --> 00:09:33.840 and contracted when it's cold? 00:09:33.840 --> 00:09:36.000 And the altimeter is really telling you 00:09:36.000 --> 00:09:40.560 how much of the atmosphere you've climbed up through. 00:09:40.560 --> 00:09:47.910 So you can see here on the right, if you look over here, 00:09:47.910 --> 00:09:49.860 and you're measuring your altitude, 00:09:49.860 --> 00:09:52.620 you're basically getting this whole stack of molecules 00:09:52.620 --> 00:09:55.170 contributing to the pressure, whereas if you're 00:09:55.170 --> 00:09:57.660 up high in the stratosphere or something, 00:09:57.660 --> 00:10:01.050 only a handful of molecules are on top of you putting pressure 00:10:01.050 --> 00:10:02.417 into your altimeter. 00:10:05.400 --> 00:10:08.820 OK, here's that standard atmosphere again. 00:10:08.820 --> 00:10:11.880 So you can see it's two niner niner two and 15 00:10:11.880 --> 00:10:15.410 degrees at sea level. 00:10:15.410 --> 00:10:20.240 So the aircraft performance is hugely affected by changes 00:10:20.240 --> 00:10:25.850 in air density, which themselves are affected by the prevailing 00:10:25.850 --> 00:10:29.480 pressure, which is mostly a function of altitude, 00:10:29.480 --> 00:10:32.630 the temperature, and the humidity. 00:10:32.630 --> 00:10:36.830 Usually, the conditions are referenced to the ISA, 00:10:36.830 --> 00:10:38.762 the standard atmosphere. 00:10:38.762 --> 00:10:40.220 The summertime, it'll be, you know, 00:10:40.220 --> 00:10:43.340 ISA plus 15 or ISA plus 20. 00:10:43.340 --> 00:10:49.230 And if it's the wintertime, it might be ISA or ISA minus 20. 00:10:49.230 --> 00:10:52.460 When the air density is reduced and there are fewer molecules 00:10:52.460 --> 00:10:56.360 around, the engine is not taking in as much air for combustion. 00:10:56.360 --> 00:10:59.630 Remember that the jet engines are normally aspirated. 00:10:59.630 --> 00:11:03.170 And the piston engines also that are without a turbocharger, 00:11:03.170 --> 00:11:06.703 they're just trying to burn up a fixed volume of air. 00:11:06.703 --> 00:11:08.870 And that's going to correspond to a different number 00:11:08.870 --> 00:11:14.990 of molecules of air and fuel depending on the altitude. 00:11:14.990 --> 00:11:17.490 The only good thing about going up high-- 00:11:17.490 --> 00:11:18.890 the propeller's also not grabbing 00:11:18.890 --> 00:11:21.795 as much air for thrust. 00:11:21.795 --> 00:11:23.420 The only thing good about going up high 00:11:23.420 --> 00:11:25.460 is that drag is reduced, and that's 00:11:25.460 --> 00:11:28.250 why you see the airliners up high. 00:11:28.250 --> 00:11:31.460 They go faster and they save a lot of fuel. 00:11:31.460 --> 00:11:34.050 OK, some definitions. 00:11:34.050 --> 00:11:39.370 The pressure altitude is just the-- 00:11:39.370 --> 00:11:43.430 it's going to be your height above sea level 00:11:43.430 --> 00:11:47.240 with the altimeter set to two niner niner two. 00:11:47.240 --> 00:11:51.680 You just have to take the two niner niner 00:11:51.680 --> 00:11:54.950 two minus the actual altimeter setting that's being published, 00:11:54.950 --> 00:12:00.480 multiply that by 1,000, so a full inch of altimeter 00:12:00.480 --> 00:12:03.555 adjustment, from two niner niner two to three zero 00:12:03.555 --> 00:12:06.690 niner two would correspond to 1,000 foot difference 00:12:06.690 --> 00:12:07.800 in pressure altitude. 00:12:10.590 --> 00:12:13.265 And you can calculate that by a chart. 00:12:13.265 --> 00:12:14.640 Here's a chart that they give you 00:12:14.640 --> 00:12:15.890 if you don't like the formula. 00:12:15.890 --> 00:12:19.860 So this is something, again, you might have to do on a test. 00:12:19.860 --> 00:12:23.960 I'll say, OK, at two nine niner two, the correction is 0. 00:12:23.960 --> 00:12:28.800 At 30.0, the correction is minus 73. 00:12:28.800 --> 00:12:32.340 So up here you can see we've got this formula where 00:12:32.340 --> 00:12:35.610 we interpolated between the two to try to figure out, 00:12:35.610 --> 00:12:38.010 what would the pressure altitude be 00:12:38.010 --> 00:12:42.077 if we start with a field elevation of 3,563 00:12:42.077 --> 00:12:44.160 and the altimeter is two niner niner six, which is 00:12:44.160 --> 00:12:46.080 just a little bit non-standard? 00:12:46.080 --> 00:12:48.310 We would expect a 40 foot difference. 00:12:48.310 --> 00:12:51.000 If we look at the table and we interpolate, 00:12:51.000 --> 00:12:54.000 we come up with a 36.5 foot difference. 00:12:54.000 --> 00:12:56.100 And we find out that the airplane 00:12:56.100 --> 00:13:00.450 feels as though it's only at 3,526 feet above sea level, 00:13:00.450 --> 00:13:05.900 assuming the temperature matches that ISA standard. 00:13:05.900 --> 00:13:08.530 All right, so density altitude is a lot more important. 00:13:08.530 --> 00:13:13.260 And oftentimes it will be reported on the ASOS or ATIS. 00:13:13.260 --> 00:13:15.780 So the airport will actually tell you 00:13:15.780 --> 00:13:19.560 density altitude is 3,000 feet or 2,000 feet 00:13:19.560 --> 00:13:21.990 or whatever it is. 00:13:21.990 --> 00:13:25.860 That you get from correcting what's usually 00:13:25.860 --> 00:13:29.550 a relatively small correction for pressure altitude compared 00:13:29.550 --> 00:13:32.430 to the actual altitude, but correcting it 00:13:32.430 --> 00:13:34.680 for the non-standard temperature. 00:13:34.680 --> 00:13:36.908 I think, as I said earlier, you know, 00:13:36.908 --> 00:13:39.450 flying is a lot more popular in New England in the summertime 00:13:39.450 --> 00:13:43.110 than in the wintertime, so it's usually warmer than standard. 00:13:43.110 --> 00:13:47.670 Density altitude has a huge effect on performance. 00:13:47.670 --> 00:13:50.130 And it's a non-linear relationship, 00:13:50.130 --> 00:13:52.110 so you have to look it up in a table 00:13:52.110 --> 00:13:54.490 or calculate it with the E6B. 00:13:54.490 --> 00:13:54.990 We'll see. 00:13:54.990 --> 00:13:57.980 Maybe I'll play around with the E6B 00:13:57.980 --> 00:14:00.105 so people can look at it during breaks. 00:14:00.105 --> 00:14:05.508 I have the slide rule and the manual right here. 00:14:05.508 --> 00:14:07.800 And I think we'll try to get the document camera going, 00:14:07.800 --> 00:14:10.380 so maybe I can show you guys some exciting slide 00:14:10.380 --> 00:14:14.150 rule activities. 00:14:14.150 --> 00:14:16.590 OK, so you can calculate it, though, using the E6B, 00:14:16.590 --> 00:14:18.930 like I said, using charts. 00:14:18.930 --> 00:14:22.540 And there's various web and app way of doing it. 00:14:22.540 --> 00:14:24.390 So the density altitude, here's a chart. 00:14:24.390 --> 00:14:26.085 So again, this is the kind of stuff 00:14:26.085 --> 00:14:27.210 that's on the written exam. 00:14:27.210 --> 00:14:30.580 You guys are all pretty good at working with charts and tables, 00:14:30.580 --> 00:14:33.230 so I'm sure you won't have any trouble. 00:14:33.230 --> 00:14:36.360 They're giving you these initial conditions up here 00:14:36.360 --> 00:14:38.930 on your left. 00:14:38.930 --> 00:14:41.750 So you look to find where the pressure 00:14:41.750 --> 00:14:44.610 altitude is on the chart. 00:14:44.610 --> 00:14:48.200 And it says to, you know, add 626 feet, which 00:14:48.200 --> 00:14:50.990 is interpolating between those two. 00:14:50.990 --> 00:14:53.360 Then you've got this pressure altitude 00:14:53.360 --> 00:15:03.250 line of going from here down to here at 5,856. 00:15:03.250 --> 00:15:06.240 And now we've got to correct that for temperature. 00:15:06.240 --> 00:15:12.760 So here's our temperature of about 80 degrees, 81 degrees. 00:15:12.760 --> 00:15:15.670 And then we go over to the left, and we can read that-- 00:15:15.670 --> 00:15:17.710 I think I told you guys that, in the summertime, 00:15:17.710 --> 00:15:21.270 usually the density altitude is about 2,000 feet higher 00:15:21.270 --> 00:15:23.500 than the pressure altitude. 00:15:23.500 --> 00:15:28.900 And sure enough, here it's 8,250, 00:15:28.900 --> 00:15:35.080 which is about 2,400 feet higher than the pressure altitude. 00:15:35.080 --> 00:15:39.790 So the density altitude gave us a little more than a 2,000 foot 00:15:39.790 --> 00:15:42.100 boost for that non-standard temperature. 00:15:42.100 --> 00:15:45.570 The reason it's so much, I guess, is it's not-- 00:15:45.570 --> 00:15:47.980 80 degrees at sea level wouldn't be 00:15:47.980 --> 00:15:50.560 that high above the standard temperature. 00:15:50.560 --> 00:15:55.830 But 81 degrees Fahrenheit at a mile above sea level 00:15:55.830 --> 00:15:59.975 is quite a spectacular temperature compared 00:15:59.975 --> 00:16:01.100 to the standard atmosphere. 00:16:01.100 --> 00:16:06.285 Let's go back to the standard atmosphere. 00:16:06.285 --> 00:16:09.800 Yeah, so at 5,000 feet, it's only 00:16:09.800 --> 00:16:12.125 supposed to be seven degrees Celsius. 00:16:17.120 --> 00:16:20.520 And here we said it was about 27 degrees Celsius. 00:16:20.520 --> 00:16:22.100 So that's ISA plus 20. 00:16:22.100 --> 00:16:24.680 Just like I said, if you look at a lot of jet performance 00:16:24.680 --> 00:16:27.980 charts, you have ISA minus 20 ISA and ISA plus 20. 00:16:32.066 --> 00:16:34.770 Oh, flight computer demo if there's time. 00:16:34.770 --> 00:16:38.100 Let me just futz with that at the end of all this. 00:16:38.100 --> 00:16:41.102 I'll give you an E6B intro. 00:16:41.102 --> 00:16:42.060 When are they the same? 00:16:44.940 --> 00:16:47.640 I think this is an FAA test question, when the temperature 00:16:47.640 --> 00:16:54.490 distribution is the same as that of the standard atmosphere. 00:16:54.490 --> 00:16:58.370 OK, humidity is also another enemy, a little bit more 00:16:58.370 --> 00:17:00.350 surprisingly. 00:17:00.350 --> 00:17:03.560 The water vapor molecules, actually, in the air 00:17:03.560 --> 00:17:06.260 actually reduce the density of the air. 00:17:06.260 --> 00:17:08.628 You might think that they would increase it. 00:17:08.628 --> 00:17:09.170 I don't know. 00:17:09.170 --> 00:17:12.290 Maybe there's a chemist or a physicist in this crowd who 00:17:12.290 --> 00:17:13.190 can explain why. 00:17:13.190 --> 00:17:15.170 I'm not exactly sure myself. 00:17:15.170 --> 00:17:17.839 But it's just something to remember, that contrary-- 00:17:17.839 --> 00:17:20.690 if the air feels heavy to you, it 00:17:20.690 --> 00:17:24.440 feels light to your aircraft engine and to your wings. 00:17:24.440 --> 00:17:26.990 It's a smaller effect than temperature, 00:17:26.990 --> 00:17:28.730 but the engine performance supposedly 00:17:28.730 --> 00:17:32.210 can be reduced by about 7%. 00:17:32.210 --> 00:17:35.210 This is not something that we normally correct for. 00:17:35.210 --> 00:17:38.210 However, there is this nice web calculator 00:17:38.210 --> 00:17:41.294 that I found for free on pilotfriend.com. 00:17:41.294 --> 00:17:47.510 And you get to enter the relative humidity of the air. 00:17:47.510 --> 00:17:51.230 So where is that? 00:17:51.230 --> 00:17:53.270 We have the air temperature. 00:17:53.270 --> 00:17:54.920 Oh, we have the dew point, right? 00:17:54.920 --> 00:17:58.520 So we said it was a 30 degree temperature and a 28 degree dew 00:17:58.520 --> 00:17:59.520 point. 00:17:59.520 --> 00:18:03.050 So that's a pretty narrow spread. 00:18:03.050 --> 00:18:06.200 And therefore, it's a pretty high humidity day. 00:18:06.200 --> 00:18:09.980 So they say, well, it's 78% humidity, 00:18:09.980 --> 00:18:14.290 and we're correcting that up to 8,107. 00:18:14.290 --> 00:18:16.040 You can play around with this on your own. 00:18:16.040 --> 00:18:18.662 If you reduce the dew point to 10 degrees Celsius, 00:18:18.662 --> 00:18:20.120 which is going to be a really dry-- 00:18:20.120 --> 00:18:24.290 you know, 30 to 10 split is a nice, dry day out west 00:18:24.290 --> 00:18:28.760 or, you know, here occasionally a crisp day-- 00:18:28.760 --> 00:18:30.650 then it's only 7,735. 00:18:30.650 --> 00:18:37.130 So the change in humidity had about a 300-foot effect 00:18:37.130 --> 00:18:38.570 on the altitude. 00:18:38.570 --> 00:18:48.160 But the change in temperature was nearly 3,000 feet. 00:18:48.160 --> 00:18:53.660 OK, the maximum convenience way to do this is with apps. 00:18:53.660 --> 00:18:57.560 So ForeFlight, for example, will just tell you. 00:18:57.560 --> 00:19:00.260 The density altitude-- this was, I think, 00:19:00.260 --> 00:19:01.910 Sunday night at Bedford. 00:19:01.910 --> 00:19:03.200 Let's look at this beautiful-- 00:19:03.200 --> 00:19:05.617 I don't know how many people will come to [INAUDIBLE] now. 00:19:05.617 --> 00:19:09.440 So Bedford's approximately at sea level, about 130 feet 00:19:09.440 --> 00:19:10.520 above sea level. 00:19:10.520 --> 00:19:13.790 It was minus 4 degrees, and the density altitude 00:19:13.790 --> 00:19:16.640 was minus 1,400. 00:19:16.640 --> 00:19:19.833 So we were flying, you know, skimming 00:19:19.833 --> 00:19:21.500 the surface of the Dead Sea or something 00:19:21.500 --> 00:19:23.730 in terms of performance. 00:19:23.730 --> 00:19:26.420 So the airplane will be really happy about flying 00:19:26.420 --> 00:19:28.790 all wintertime, and it'll climb better 00:19:28.790 --> 00:19:32.450 than the book, most of the numbers in the book. 00:19:32.450 --> 00:19:35.900 OK, the density altitude is often 00:19:35.900 --> 00:19:40.195 just kind of baked into the performance chart. 00:19:44.090 --> 00:19:46.070 Pipers normally take off with no flaps. 00:19:46.070 --> 00:19:48.320 But if you want to get off the ground really quickly, 00:19:48.320 --> 00:19:51.110 like taking off over grass or mud or something, 00:19:51.110 --> 00:19:53.720 you can put down the flaps and try 00:19:53.720 --> 00:19:56.060 to have less time on the ground and not be 00:19:56.060 --> 00:19:57.920 going so fast over the ground. 00:19:57.920 --> 00:19:59.650 Your ground rill will be shortened. 00:19:59.650 --> 00:20:01.760 Anyway, so here, they don't actually 00:20:01.760 --> 00:20:04.730 ask you to ever calculate the density altitude. 00:20:04.730 --> 00:20:09.500 They just say, OK, it's almost 30 degrees outside. 00:20:09.500 --> 00:20:12.650 And it looks like we're up here at about 1,500 feet. 00:20:12.650 --> 00:20:16.050 So we'll start here on the performance chart. 00:20:16.050 --> 00:20:17.200 These people are virtuous. 00:20:17.200 --> 00:20:21.900 The only weigh 2,175 total, so we come down a little bit. 00:20:21.900 --> 00:20:23.940 And we can come over here, and we 00:20:23.940 --> 00:20:25.540 find that it's going to take-- 00:20:28.725 --> 00:20:30.320 is there a wind here-- 00:20:30.320 --> 00:20:32.040 15 knots of headwind. 00:20:32.040 --> 00:20:35.180 So we come down this graph and we 00:20:35.180 --> 00:20:39.650 find that it will take us 1,500 feet 00:20:39.650 --> 00:20:44.450 to take off over a 50 foot obstacle. 00:20:50.960 --> 00:20:52.220 Fair enough? 00:20:52.220 --> 00:20:55.580 So anyway, we never figured out what the density altitude was. 00:20:55.580 --> 00:21:01.110 It was just something that affected 00:21:01.110 --> 00:21:02.360 where we started on the chart. 00:21:02.360 --> 00:21:03.920 I guess, maybe it's implicit in here. 00:21:07.320 --> 00:21:08.820 I think it is implicit, right? 00:21:08.820 --> 00:21:11.130 Because we're starting up high. 00:21:11.130 --> 00:21:13.350 Maybe somebody who is smarter can figure this out. 00:21:13.350 --> 00:21:14.835 Yeah, so sea level at 0-- 00:21:18.250 --> 00:21:21.673 Yeah, I think we can pull it out of those graphs. 00:21:21.673 --> 00:21:24.090 But nobody would, because what you're really interested in 00:21:24.090 --> 00:21:26.940 is the number of how long you're going to be on the runway. 00:21:26.940 --> 00:21:31.660 All right, you'll have to slow down if you're in turbulence. 00:21:31.660 --> 00:21:34.570 So if you plan for some kind of flight a certain amount of time 00:21:34.570 --> 00:21:36.220 and it's going to be very bumpy-- 00:21:36.220 --> 00:21:38.440 I remember we talked about maneuvering speed. 00:21:38.440 --> 00:21:42.100 Depending on your weight, you'll have to slow down 00:21:42.100 --> 00:21:44.140 to avoid bending the aircraft. 00:21:44.140 --> 00:21:47.140 Or, you know, turbulence that's severe enough 00:21:47.140 --> 00:21:49.600 to bend the aircraft is extremely rare. 00:21:49.600 --> 00:21:53.530 But turbulence that's sufficient to make you and your passengers 00:21:53.530 --> 00:21:55.810 unhappy is a lot more common. 00:21:55.810 --> 00:21:59.260 And in both cases, you know, you pull away back on the speed. 00:21:59.260 --> 00:22:01.510 So in the Pilatus, for example, you'll 00:22:01.510 --> 00:22:04.580 pull back to 150 knots from 200 knots. 00:22:04.580 --> 00:22:08.080 In the Cirrus, you know, you might pull back from 130 down 00:22:08.080 --> 00:22:09.715 to 100. 00:22:09.715 --> 00:22:11.890 And in a helicopter, you know, you'll 00:22:11.890 --> 00:22:16.500 pull back from 110 knots to maybe 70. 00:22:16.500 --> 00:22:18.190 OK, pilot technique. 00:22:18.190 --> 00:22:23.260 So all the book numbers depend on the pilot 00:22:23.260 --> 00:22:25.180 doing what the book says. 00:22:25.180 --> 00:22:28.060 So think about clearing an obstacle 00:22:28.060 --> 00:22:29.440 at the end of the runway. 00:22:29.440 --> 00:22:33.280 That's dependent on the pilot rotating within a couple 00:22:33.280 --> 00:22:36.910 knots of the specified rotation speed, getting the gear 00:22:36.910 --> 00:22:41.110 and the flaps retracted if they've been deployed, 00:22:41.110 --> 00:22:46.150 or if the gear are retractable at the recommended airspeed, 00:22:46.150 --> 00:22:50.100 and just generally having the pitch attitude and the air 00:22:50.100 --> 00:22:54.690 speeds where the manufacturer tested the aircraft. 00:22:54.690 --> 00:22:55.605 And think about it. 00:22:55.605 --> 00:22:57.730 You might say, well, you know, anybody can do that. 00:22:57.730 --> 00:23:00.420 You're rolling down the runway at Hanscom Field. 00:23:00.420 --> 00:23:01.900 It's a mile and a half long. 00:23:01.900 --> 00:23:05.472 You know, you're fresh, so that performance 00:23:05.472 --> 00:23:07.930 is-- you're probably going to come pretty close to the book 00:23:07.930 --> 00:23:09.730 performance. 00:23:09.730 --> 00:23:11.260 But think about doing a go-around. 00:23:11.260 --> 00:23:13.210 You've just done a two hour flight. 00:23:13.210 --> 00:23:14.960 You were trying to land at the airport. 00:23:14.960 --> 00:23:18.910 You know, somehow, either there was somebody else on the runway 00:23:18.910 --> 00:23:21.160 or, you know, you didn't get the approach just right, 00:23:21.160 --> 00:23:23.530 so you decided you're going to go around and try again. 00:23:23.530 --> 00:23:24.988 At that point, you know, you've got 00:23:24.988 --> 00:23:27.640 to reconfigure the airplane, change the flap configuration, 00:23:27.640 --> 00:23:29.140 change the gear configuration. 00:23:31.950 --> 00:23:38.248 There's a couple interesting incidents that have happened. 00:23:38.248 --> 00:23:40.290 Well, it was, unfortunately, not very interesting 00:23:40.290 --> 00:23:41.140 for the people involved. 00:23:41.140 --> 00:23:42.960 But there was an American Airlines flight 00:23:42.960 --> 00:23:46.590 that got disoriented in Colombia in the clouds. 00:23:46.590 --> 00:23:48.690 And the terrain warning system said, you know, 00:23:48.690 --> 00:23:50.850 terrain, terrain, pull up, pull up. 00:23:50.850 --> 00:23:54.840 And so they advanced the thrust levers. 00:23:54.840 --> 00:23:57.000 You can follow that link and read about it. 00:23:57.000 --> 00:24:00.150 They advanced the thrust levers and had maximum power, 00:24:00.150 --> 00:24:03.330 but they neglected to-- they had the spoilers deployed 00:24:03.330 --> 00:24:04.590 for a descent. 00:24:04.590 --> 00:24:07.170 They didn't retract the spoilers, 00:24:07.170 --> 00:24:09.720 so the airplane was climbing but not nearly as 00:24:09.720 --> 00:24:13.080 well as it would have without the spoilers retracted. 00:24:13.080 --> 00:24:15.000 So that's an example where, you know, 00:24:15.000 --> 00:24:19.470 in a critical situation or a fatigue situation, 00:24:19.470 --> 00:24:20.130 you may not-- 00:24:23.140 --> 00:24:25.540 I wish I could get this-- 00:24:25.540 --> 00:24:27.540 I don't know if I can move this onto the screen. 00:24:27.540 --> 00:24:30.040 I want to show a picture of this crazy airplane that I flew. 00:24:32.660 --> 00:24:33.660 Tada! 00:24:33.660 --> 00:24:35.450 Look at that Russian seaplane. 00:24:35.450 --> 00:24:37.370 It's got two Cirrus engines in there. 00:24:45.932 --> 00:24:47.390 I don't even see the second engine. 00:24:47.390 --> 00:24:48.020 Well, there it is. 00:24:48.020 --> 00:24:49.603 You can see that propeller over there. 00:24:51.820 --> 00:24:52.320 So sorry. 00:24:52.320 --> 00:24:54.000 There's one propeller sticking up. 00:24:54.000 --> 00:24:55.020 There is the other one. 00:24:55.020 --> 00:24:57.920 So it's got two Cirrus engines, 200 horsepower each mounted 00:24:57.920 --> 00:24:59.150 on pods. 00:24:59.150 --> 00:25:02.090 And if you say, how can that airplane climb 00:25:02.090 --> 00:25:07.250 after an engine failure on one little Cirrus engine 00:25:07.250 --> 00:25:08.048 when it has-- 00:25:08.048 --> 00:25:08.590 I don't know. 00:25:08.590 --> 00:25:10.310 I think it could seat seven people. 00:25:10.310 --> 00:25:11.780 The answer is it really can't. 00:25:14.430 --> 00:25:17.360 So I tested that airplane out because I thought it was cool. 00:25:17.360 --> 00:25:19.790 And I went flying with an airline captain. 00:25:19.790 --> 00:25:22.520 And piston twins aren't really required 00:25:22.520 --> 00:25:25.160 to demonstrate any kind of climb performance. 00:25:25.160 --> 00:25:27.170 For jets, there are certain minimums. 00:25:27.170 --> 00:25:30.560 On one engine, it has to be able to still climb 750 00:25:30.560 --> 00:25:31.970 feet per minute or something. 00:25:31.970 --> 00:25:36.570 But for these piston twins, the FAA says, you know, 00:25:36.570 --> 00:25:38.570 you should know that you're buying a pig anyway. 00:25:38.570 --> 00:25:41.420 And if you care, go and get yourself a turbine, 00:25:41.420 --> 00:25:43.230 or don't load everybody in there. 00:25:43.230 --> 00:25:45.020 But anyway, this [INAUDIBLE] thing, it 00:25:45.020 --> 00:25:46.750 could not climb on one engine. 00:25:46.750 --> 00:25:49.388 We couldn't even maintain altitude on one engine. 00:25:49.388 --> 00:25:50.930 And it turned out that we'd forgotten 00:25:50.930 --> 00:25:53.270 to close the cowl flaps. 00:25:53.270 --> 00:25:56.210 It had these extra openings for cooling 00:25:56.210 --> 00:25:59.370 to provide extra cooling at high power settings. 00:25:59.370 --> 00:26:01.370 And if you don't close them, there's extra drag. 00:26:01.370 --> 00:26:03.912 And that extra drag was enough to turn what should have been, 00:26:03.912 --> 00:26:10.460 you know, 150 foot climb rate or something into 150 foot sink 00:26:10.460 --> 00:26:11.870 rate or something. 00:26:11.870 --> 00:26:14.730 So that's another thing that can affect performance. 00:26:14.730 --> 00:26:16.520 OK, runway condition. 00:26:16.520 --> 00:26:18.792 This really affects your planning, 00:26:18.792 --> 00:26:20.750 whether you can take off, whether you can land, 00:26:20.750 --> 00:26:23.040 how much weight you can put in there. 00:26:23.040 --> 00:26:27.320 So for example, if it's dry grass, 00:26:27.320 --> 00:26:30.560 you need a longer runway than if it's paved. 00:26:30.560 --> 00:26:35.390 Alternatively, you can take off at a lower weight. 00:26:35.390 --> 00:26:39.300 If it's wet grass, you need a lot more room to land 00:26:39.300 --> 00:26:43.610 and, you know, yet more room to take off. 00:26:43.610 --> 00:26:46.310 At the airline, if the runway was 00:26:46.310 --> 00:26:49.460 grooved, which almost all bigger US airports have 00:26:49.460 --> 00:26:53.300 these grooved runways, we didn't make any adjustments. 00:26:53.300 --> 00:26:55.043 Didn't matter how heavy the rain was. 00:26:55.043 --> 00:26:56.960 It didn't matter how long it had been raining. 00:26:56.960 --> 00:27:00.110 We just assumed it was going to perform exactly the same as 00:27:00.110 --> 00:27:02.590 if it were dry. 00:27:02.590 --> 00:27:04.320 If it's not a grooved runway, though, 00:27:04.320 --> 00:27:06.020 and water can sit on the runway, it 00:27:06.020 --> 00:27:07.830 can have a big effect on performance. 00:27:07.830 --> 00:27:09.650 So here are some numbers that I pulled. 00:27:09.650 --> 00:27:11.960 I'm type rated in the Cessna Mustang, which 00:27:11.960 --> 00:27:13.880 is an interesting little business jet. 00:27:13.880 --> 00:27:16.820 It lands at about the same speed as the Beechcraft Baron, 00:27:16.820 --> 00:27:19.040 so it's a great beginner jet. 00:27:19.040 --> 00:27:23.180 Anyway, so in conditions where you need 3,000 feet of runway, 00:27:23.180 --> 00:27:25.240 that's up at pretty high altitude, 00:27:25.240 --> 00:27:28.730 you're going to need 4,240, Cessna says, if it's wet. 00:27:28.730 --> 00:27:32.480 If water is actually standing on it, I think 0.1 inches of water 00:27:32.480 --> 00:27:35.810 was even more, you'll need yet more runway. 00:27:35.810 --> 00:27:38.360 If it's snow, a little bit more. 00:27:38.360 --> 00:27:41.270 Wet ice, it was just off the chart. 00:27:41.270 --> 00:27:44.390 But if you started at 2,200 feet of dry runway, 00:27:44.390 --> 00:27:47.360 you would need 16,600 feet. 00:27:47.360 --> 00:27:51.830 So actually, oftentimes, when the surface is contaminated, 00:27:51.830 --> 00:27:54.080 that's one reason why even fairly small business 00:27:54.080 --> 00:27:56.600 jets may need a long runway, like at Logan 00:27:56.600 --> 00:27:58.100 or at Hanscom Field. 00:27:58.100 --> 00:28:01.340 Even an airport like Nashua, which has 6,000 feet 00:28:01.340 --> 00:28:04.160 may not be enough if they're reporting that there's 00:28:04.160 --> 00:28:07.260 snow on the runway. 00:28:07.260 --> 00:28:09.550 OK, what about slope? 00:28:09.550 --> 00:28:14.910 So going downhill is obviously a lot easier than going uphill. 00:28:14.910 --> 00:28:18.740 And you can see here-- and also stopping going uphill 00:28:18.740 --> 00:28:19.750 is a lot easier. 00:28:19.750 --> 00:28:22.170 So here are some numbers from the Cirrus book 00:28:22.170 --> 00:28:26.550 that every one degree of slope increases your takeoff run 00:28:26.550 --> 00:28:30.750 by 22% at sea level, for example. 00:28:30.750 --> 00:28:39.200 And you also get a 9% reduction in the landing distance. 00:28:39.200 --> 00:28:41.700 OK, ceiling. 00:28:41.700 --> 00:28:43.290 The service ceiling of the aircraft 00:28:43.290 --> 00:28:46.050 is a little bit below the absolute ceiling. 00:28:46.050 --> 00:28:47.760 That's where the FAA says the plane will 00:28:47.760 --> 00:28:50.010 climb 100 feet per minute. 00:28:50.010 --> 00:28:51.970 The manufacturer has demonstrated to the FAA 00:28:51.970 --> 00:28:55.260 that the airplane could, at least when it was brand new, 00:28:55.260 --> 00:28:57.540 make 100 feet per minute in climb rate. 00:28:57.540 --> 00:29:02.820 So that's 13,500 feet for a 172 Cessna. 00:29:02.820 --> 00:29:05.340 And I think that's pretty typical for these normally 00:29:05.340 --> 00:29:06.870 aspirated four-seaters. 00:29:06.870 --> 00:29:09.920 Somewhere around there is where it'll stop climbing. 00:29:09.920 --> 00:29:12.480 The Cirrus, there's a limitation in there 00:29:12.480 --> 00:29:16.620 that says maximum operating altitude is 17,500 feet. 00:29:16.620 --> 00:29:18.570 I think that's more regulatory, because you 00:29:18.570 --> 00:29:21.490 can't take the Cirrus up into the flight levels. 00:29:21.490 --> 00:29:25.740 They need extra equipment to go up above 18,000 feet, maybe. 00:29:25.740 --> 00:29:28.140 I don't think it's really practical to get up 00:29:28.140 --> 00:29:31.800 to 17,500 feet at maximum gross weight 00:29:31.800 --> 00:29:33.270 in the standard atmosphere. 00:29:33.270 --> 00:29:37.110 I've gotten into about 13,000 feet out west in the summer, 00:29:37.110 --> 00:29:40.320 so that is more like being at 15,000 feet. 00:29:40.320 --> 00:29:42.730 But it was barely climbing. 00:29:42.730 --> 00:29:46.320 OK, range versus endurance. 00:29:46.320 --> 00:29:50.850 So we're going to get back into the power and drag curves here. 00:29:50.850 --> 00:29:53.400 The max range airspeed is going to depend on the wind, 00:29:53.400 --> 00:29:55.720 like I said earlier. 00:29:55.720 --> 00:29:57.990 If you have 100 knot headwind, then you 00:29:57.990 --> 00:30:03.320 have to go faster than 100 knots in order to go anywhere. 00:30:03.320 --> 00:30:05.860 If you want to loiter for some reason-- this year at Oshkosh 00:30:05.860 --> 00:30:08.470 was a nightmare for people who didn't go IFR. 00:30:08.470 --> 00:30:10.390 They had a lot of marginal VFR weather. 00:30:10.390 --> 00:30:15.970 So for the first couple of days, when people were arriving, 00:30:15.970 --> 00:30:18.640 there were these short windows, just an hour or two, 00:30:18.640 --> 00:30:20.980 when people could really get in legally, 00:30:20.980 --> 00:30:23.000 the VFR homebuilder types. 00:30:23.000 --> 00:30:24.970 So they were just holding. 00:30:24.970 --> 00:30:27.460 People were literally holding for three hours 00:30:27.460 --> 00:30:30.190 and then finally had to give up and go and refuel somewhere. 00:30:30.190 --> 00:30:31.690 But if you're in that situation, you 00:30:31.690 --> 00:30:35.260 want to set your speed to whatever the minimum fuel 00:30:35.260 --> 00:30:36.280 consumption speed is. 00:30:36.280 --> 00:30:38.330 And it can be quite different. 00:30:38.330 --> 00:30:42.190 The Robinson R44 manual talks about 100 knots for max range. 00:30:42.190 --> 00:30:45.820 I believe that's assuming a 10 knot headwind, since usually 00:30:45.820 --> 00:30:47.320 we're suffering with a headwind more 00:30:47.320 --> 00:30:49.150 often than with a tailwind. 00:30:49.150 --> 00:30:51.080 And you might say, how is that possible? 00:30:51.080 --> 00:30:53.870 How is it possible to have a headwind-- 00:30:53.870 --> 00:30:57.740 unless God hates you, how is it possible to have 00:30:57.740 --> 00:30:59.240 a headwind more than half the time? 00:30:59.240 --> 00:31:01.000 If you think about it-- 00:31:01.000 --> 00:31:02.320 Richard, you know the answer? 00:31:02.320 --> 00:31:02.903 RICHARD: I do. 00:31:02.903 --> 00:31:04.153 PHILLIP GREENSPUN: What is it? 00:31:04.153 --> 00:31:05.508 RICHARD: Here's the question. 00:31:05.508 --> 00:31:08.540 You're flying 100 miles to an airport. 00:31:11.640 --> 00:31:13.300 In zero wind, how long does it take 00:31:13.300 --> 00:31:15.920 to fly-- you're on an airplane that flies 100 miles an hour. 00:31:15.920 --> 00:31:17.620 How long does it take to fly round trip? 00:31:17.620 --> 00:31:19.037 PHILLIP GREENSPUN: Trick question. 00:31:21.230 --> 00:31:23.910 RICHARD: 100 miles apart, 100 miles an hour airplane, 00:31:23.910 --> 00:31:24.950 no wind. 00:31:24.950 --> 00:31:26.808 How long is a round trip going to take? 00:31:26.808 --> 00:31:27.764 AUDIENCE: 2 hours? 00:31:27.764 --> 00:31:28.720 RICHARD: Yeah. 00:31:28.720 --> 00:31:31.772 Let's say you have a 50 knot headwind. 00:31:31.772 --> 00:31:33.340 It's exactly on your nose. 00:31:33.340 --> 00:31:35.920 You can get 50 knots headwind on the way out 00:31:35.920 --> 00:31:38.223 and 50 knot tailwind on the way back. 00:31:38.223 --> 00:31:39.140 How long does it take? 00:31:39.140 --> 00:31:40.440 AUDIENCE: 2 hours. 00:31:40.440 --> 00:31:41.560 RICHARD: Wrong. 00:31:41.560 --> 00:31:43.788 Work it out. 00:31:43.788 --> 00:31:45.580 PHILLIP GREENSPUN: Well, that's one aspect. 00:31:45.580 --> 00:31:49.510 You're going to spend more of your time, as Richard's saying. 00:31:49.510 --> 00:31:52.990 It's going to take you two hours to get there in one direction, 00:31:52.990 --> 00:31:55.630 and then it won't take you zero time to get back, 00:31:55.630 --> 00:31:59.050 so you're spending more of your time in the headwind 00:31:59.050 --> 00:32:00.225 than in the tailwind. 00:32:00.225 --> 00:32:01.600 But there's something even worse. 00:32:01.600 --> 00:32:03.225 I saw this the other day in the Cirrus. 00:32:03.225 --> 00:32:07.833 There was about a 70 knot wind that was actually 00:32:07.833 --> 00:32:09.250 a little bit-- it should have been 00:32:09.250 --> 00:32:10.570 a little bit of a tailwind. 00:32:10.570 --> 00:32:14.770 It was more than 90 degrees off my desired track. 00:32:14.770 --> 00:32:16.930 But if you think about it, the airplane's 00:32:16.930 --> 00:32:20.500 constantly having to fight its way back into that wind, 00:32:20.500 --> 00:32:22.910 so it's effectively taking a longer flight path. 00:32:22.910 --> 00:32:28.300 So even the wind is directly a beam wind 90 degrees off, 00:32:28.300 --> 00:32:32.910 there's actually-- the majority of the circle, 00:32:32.910 --> 00:32:35.350 the 360 degrees circle of wind directions, 00:32:35.350 --> 00:32:38.110 the majority of that is subtracting 00:32:38.110 --> 00:32:44.000 from your performance and has at least some headwind component. 00:32:44.000 --> 00:32:45.590 Sound crazy? 00:32:45.590 --> 00:32:46.640 Think about it, yeah. 00:32:46.640 --> 00:32:50.780 So if you're going 100 miles and there's also this 100 knot side 00:32:50.780 --> 00:32:53.480 wind, you're having to spend quite 00:32:53.480 --> 00:32:59.930 a bit of your energy continuing to steer into that side wind. 00:32:59.930 --> 00:33:07.010 OK, here is a power and drag curve for an RV-6A. 00:33:07.010 --> 00:33:10.700 The experimental guys are, in this case, 00:33:10.700 --> 00:33:13.880 more aggressive about producing charts. 00:33:13.880 --> 00:33:17.480 So if you actually care about where you're going, 00:33:17.480 --> 00:33:22.160 you want to be a little bit up the power required curve. 00:33:22.160 --> 00:33:25.040 You want to find out where it's tangent to one of these lines 00:33:25.040 --> 00:33:26.360 going back to zero. 00:33:26.360 --> 00:33:29.037 And if all you care about is maximum endurance, 00:33:29.037 --> 00:33:30.620 you just want to be at the point where 00:33:30.620 --> 00:33:32.720 the curve is at its bare minimum, 00:33:32.720 --> 00:33:35.300 because then you're consuming the least power and, in theory, 00:33:35.300 --> 00:33:37.600 burning the least amount of fuel. 00:33:37.600 --> 00:33:38.660 Does that make sense? 00:33:43.962 --> 00:33:46.490 All right, The terms. 00:33:46.490 --> 00:33:51.860 Ground roll, these performance charts 00:33:51.860 --> 00:33:54.140 in the book that you get with the airplane, 00:33:54.140 --> 00:33:55.890 they will assume a static start. 00:33:55.890 --> 00:33:57.770 So that means you're holding the brakes, 00:33:57.770 --> 00:34:00.980 you slam the power forward, you let off the brakes, 00:34:00.980 --> 00:34:03.980 and you're going to get the book numbers, because there's 00:34:03.980 --> 00:34:07.460 no acceleration time for the engine. 00:34:07.460 --> 00:34:10.217 And actually, that's how jets are supposed to take off, too. 00:34:10.217 --> 00:34:12.800 But you probably remember from your commercial flights, that's 00:34:12.800 --> 00:34:14.489 not really how it happens. 00:34:14.489 --> 00:34:17.300 The pilots don't hold the brakes, you know, spend-- 00:34:17.300 --> 00:34:20.870 it takes maybe 10 seconds for a really heavy jet engine 00:34:20.870 --> 00:34:21.969 to spool up to full power. 00:34:21.969 --> 00:34:24.344 They don't just sit there holding the brakes, 00:34:24.344 --> 00:34:26.130 engine's at the max, and everything's 00:34:26.130 --> 00:34:28.130 screaming in the airplane, shaking, because it's 00:34:28.130 --> 00:34:29.360 just uncomfortable. 00:34:29.360 --> 00:34:31.113 So they usually cheat-- 00:34:31.113 --> 00:34:32.780 technically, they're not really supposed 00:34:32.780 --> 00:34:36.050 to do it because, you know, at that point, your test pilots. 00:34:36.050 --> 00:34:39.409 You don't really have any data for a rolling takeoff. 00:34:39.409 --> 00:34:42.090 But, you know, again, it would be 00:34:42.090 --> 00:34:43.840 kind of unnerving for passengers, I think, 00:34:43.840 --> 00:34:46.048 if they are sitting there with the airplane straining 00:34:46.048 --> 00:34:46.850 against the brakes. 00:34:49.580 --> 00:34:51.583 OK, same deal here. 00:34:51.583 --> 00:34:53.000 Ground roll and the total distance 00:34:53.000 --> 00:34:54.409 to clear the 50 foot obstacle, this 00:34:54.409 --> 00:34:56.951 is what I was telling you about the other day with the Cirrus 00:34:56.951 --> 00:34:59.420 hero who wanted to go to, I think, 00:34:59.420 --> 00:35:01.340 about 2,500 feet of runway. 00:35:01.340 --> 00:35:02.920 Actually, we had to subtract some. 00:35:02.920 --> 00:35:05.510 I think it was 2,700 minus 400. 00:35:05.510 --> 00:35:07.900 He had about 2,300 feet of runway. 00:35:07.900 --> 00:35:11.090 And he wanted to go there in the Cirrus, which takes 2,100 feet. 00:35:11.090 --> 00:35:12.720 Another guy actually wanted to go to-- 00:35:12.720 --> 00:35:16.340 there's a private air park in Falmouth, Massachusetts 00:35:16.340 --> 00:35:18.680 where you can have a house right next to the runway 00:35:18.680 --> 00:35:21.530 and keep the airplane in your garage. 00:35:21.530 --> 00:35:24.260 And that airport's only 2,300 feet long. 00:35:24.260 --> 00:35:27.200 And another east coast aero club guy-- 00:35:27.200 --> 00:35:29.000 I was handing the airplane over to him 00:35:29.000 --> 00:35:30.542 and he had this huge friend with him. 00:35:30.542 --> 00:35:32.960 This guy was like a NFL linebacker. 00:35:32.960 --> 00:35:34.820 So it was just the two of them, but big. 00:35:34.820 --> 00:35:38.255 And he wanted it also at full, topped off on fuel, 00:35:38.255 --> 00:35:40.130 so they're going to be right at gross weight. 00:35:40.130 --> 00:35:41.297 I said, where are you going? 00:35:41.297 --> 00:35:42.700 He said Falmouth. 00:35:42.700 --> 00:35:45.020 He'd just gotten his private pilot certificate 00:35:45.020 --> 00:35:46.580 a few months earlier. 00:35:46.580 --> 00:35:48.930 This guy was not commercial IFR rated like the other. 00:35:48.930 --> 00:35:51.620 And I said, look, you know, if you do everything perfect, 00:35:51.620 --> 00:35:54.950 you're going to use up 92% of that runway 00:35:54.950 --> 00:35:57.780 because it's hemmed in by these obstacles. 00:35:57.780 --> 00:35:59.270 So don't do it. 00:35:59.270 --> 00:36:03.110 So he did end up going to Hyannis, I think. 00:36:03.110 --> 00:36:07.400 All right, landing technique can actually 00:36:07.400 --> 00:36:10.250 affect the performance. 00:36:10.250 --> 00:36:14.790 So they talk about, an average pilot, the book numbers, 00:36:14.790 --> 00:36:17.060 they're predicated on extremely aggressive braking, 00:36:17.060 --> 00:36:20.810 like right to the point where you would flat spot the tires. 00:36:20.810 --> 00:36:23.480 So don't count on getting those book numbers unless you're 00:36:23.480 --> 00:36:28.010 willing to be more aggressive than probably you 00:36:28.010 --> 00:36:29.000 would want to be. 00:36:29.000 --> 00:36:32.600 And actually, I'll tell you a story about my airline days. 00:36:32.600 --> 00:36:35.180 I did a visual approach in the Laguardia. 00:36:35.180 --> 00:36:38.430 And with jets, it's not conventional to try 00:36:38.430 --> 00:36:40.430 to do the really greaser landings that you would 00:36:40.430 --> 00:36:42.140 do in a little airplane, because you 00:36:42.140 --> 00:36:45.410 need to get the airplane down and the spoilers to pop up. 00:36:45.410 --> 00:36:47.000 The jets are very efficient gliders. 00:36:47.000 --> 00:36:49.710 They don't have a big prop in front. 00:36:49.710 --> 00:36:52.010 And when you pull the power back on a piston aircraft, 00:36:52.010 --> 00:36:54.410 it really slows down dramatically because the prop 00:36:54.410 --> 00:36:55.777 has a lot of air resistance. 00:36:55.777 --> 00:36:57.860 None of that's going for you with the jet which is 00:36:57.860 --> 00:36:59.750 more efficient to begin with. 00:36:59.750 --> 00:37:02.720 So basically, the task of an airline pilot 00:37:02.720 --> 00:37:06.530 is really to slam it on, and that way the spoilers pop up 00:37:06.530 --> 00:37:08.780 and then the brakes start really working effectively. 00:37:08.780 --> 00:37:10.850 And you turn off the runway in Laguardia 00:37:10.850 --> 00:37:13.250 before you go into the river. 00:37:13.250 --> 00:37:14.960 So I landed like a Cirrus, because it 00:37:14.960 --> 00:37:18.770 was my first month on the job, and I chewed up 00:37:18.770 --> 00:37:22.700 by 1,500 feet of runway before the airplane touched down. 00:37:22.700 --> 00:37:25.520 And I applied fairly gentle braking and thrust reverse 00:37:25.520 --> 00:37:27.980 and turned off after about 5,000 feet of runway. 00:37:27.980 --> 00:37:29.480 And the captain's like, that sucked. 00:37:29.480 --> 00:37:32.030 I'm going to show you how it's done the next leg. 00:37:32.030 --> 00:37:36.860 So we did Laguardia to Charlotte, North Carolina. 00:37:36.860 --> 00:37:39.323 Who else did that leg? 00:37:39.323 --> 00:37:40.585 AUDIENCE: [INAUDIBLE] 00:37:40.585 --> 00:37:41.960 PHILLIP GREENSPUN: Captain Sully. 00:37:41.960 --> 00:37:45.330 So he dumped his passengers into a filthy cold river 00:37:45.330 --> 00:37:47.170 and they called him a hero. 00:37:47.170 --> 00:37:50.250 I got my passengers to Charlotte warm and dry, 00:37:50.250 --> 00:37:52.070 and where was my medal? 00:37:52.070 --> 00:37:53.940 Where is my fame? 00:37:53.940 --> 00:37:54.630 Nowhere. 00:37:54.630 --> 00:37:55.980 All right, so life is unfair. 00:37:55.980 --> 00:37:57.190 You've learned that. 00:37:57.190 --> 00:37:59.460 Anyway, so the captain takes this one. 00:37:59.460 --> 00:38:00.840 Air traffic control lines us up. 00:38:00.840 --> 00:38:02.010 Instead of the visual approach where 00:38:02.010 --> 00:38:04.593 you're doing everything by eye and following another aircraft, 00:38:04.593 --> 00:38:07.020 and you can't use any of the fancy automation, 00:38:07.020 --> 00:38:11.190 we were lined up 10 or 15 miles out for a straight in approach 00:38:11.190 --> 00:38:14.370 to this angled runway at Charlotte. 00:38:14.370 --> 00:38:17.280 And all the captain had to do was-- on autopilot, 00:38:17.280 --> 00:38:19.328 all he had to do was tweak the thrust levers 00:38:19.328 --> 00:38:20.370 for the perfect airspeed. 00:38:20.370 --> 00:38:21.850 The autopilot's flying. 00:38:21.850 --> 00:38:25.180 He disconnects the autopilot a couple feet above the ground. 00:38:25.180 --> 00:38:26.070 Now he's hand flying. 00:38:26.070 --> 00:38:28.500 All he has to do-- the CRJ doesn't have, 00:38:28.500 --> 00:38:30.790 the 50-seater, any leading edge devices, 00:38:30.790 --> 00:38:33.930 so it has to be pointed down a bit like a lawn dart. 00:38:33.930 --> 00:38:36.560 It's not that different from landing a Cirrus. 00:38:36.560 --> 00:38:38.350 It's unconventional for an airliner. 00:38:38.350 --> 00:38:40.380 The airliners, you notice they usually-- 00:38:40.380 --> 00:38:42.270 because of the leading edge devices, 00:38:42.270 --> 00:38:43.950 even when they're going 120 knots or so, 00:38:43.950 --> 00:38:46.900 they can be kind of nose up and they still fly pretty well. 00:38:46.900 --> 00:38:48.990 So the airplane almost can be flown-- 00:38:48.990 --> 00:38:51.570 and it can auto land, in some cases, 00:38:51.570 --> 00:38:54.510 onto the runway by itself with just a slight additional flare 00:38:54.510 --> 00:38:55.410 at the end. 00:38:55.410 --> 00:38:59.670 The CRJ has to be kept nose down 145 knots faster than all 00:38:59.670 --> 00:39:04.170 but the very biggest jets, and then it has to be, you know, 00:39:04.170 --> 00:39:07.740 flared from minus five to maybe plus five or plus 00:39:07.740 --> 00:39:09.210 seven at the end. 00:39:09.210 --> 00:39:13.440 So the captain, after telling me what a bad job I had done, 00:39:13.440 --> 00:39:17.190 he flared about five feet too high, 00:39:17.190 --> 00:39:20.100 and the airplane just sailed over 4,500 feet of runway, 00:39:20.100 --> 00:39:22.860 I think, before it finally touched down. 00:39:22.860 --> 00:39:25.270 And he slammed on the brakes, maximum thrust reverse. 00:39:25.270 --> 00:39:26.290 We barely made it off. 00:39:26.290 --> 00:39:29.430 I think we made it off after 7,200 feet of runway, 00:39:29.430 --> 00:39:32.700 so we would have been, I think, in the water in Laguardia. 00:39:32.700 --> 00:39:35.850 So that's the kind of thing where, you know, you can't-- 00:39:35.850 --> 00:39:38.970 that's why these safety margins are 00:39:38.970 --> 00:39:42.385 good to build into your own flying, because, you know, 00:39:42.385 --> 00:39:44.010 the book number said the airplane would 00:39:44.010 --> 00:39:46.557 land a lot shorter than that. 00:39:46.557 --> 00:39:49.140 Also, in a jet, there's really not a good go-around technique. 00:39:49.140 --> 00:39:50.515 Once you're below 50 feet, you're 00:39:50.515 --> 00:39:53.970 not supposed to try to add power and go around 00:39:53.970 --> 00:39:57.030 because it takes a while to spool the engines up. 00:39:57.030 --> 00:39:59.100 All right, in turbulence, you usually 00:39:59.100 --> 00:40:00.580 will increase your approach speed, 00:40:00.580 --> 00:40:03.240 which means you're going to chew up more runway. 00:40:03.240 --> 00:40:06.670 You're supposed to add half the gust factor as a rule of thumb. 00:40:06.670 --> 00:40:09.570 So if the wind is 15 gusting 25, you're 00:40:09.570 --> 00:40:11.790 going to speed up your approach by five knots. 00:40:11.790 --> 00:40:14.550 And I got the numbers here for the Cirrus. 00:40:14.550 --> 00:40:16.530 75 is kind of a good overall number, 00:40:16.530 --> 00:40:18.330 and then you'll beef it up to 80. 00:40:18.330 --> 00:40:21.210 But that means, unless it really is a headwind when you're 00:40:21.210 --> 00:40:24.540 landing, you're going to chew up a little more runway 00:40:24.540 --> 00:40:26.060 than expected. 00:40:26.060 --> 00:40:29.520 OK, flaps, as Tina mentioned, they 00:40:29.520 --> 00:40:31.440 enable you to keep your approach speed 00:40:31.440 --> 00:40:34.920 low while having a nice steep approach angle. 00:40:34.920 --> 00:40:38.335 So that's good for getting over trees and stuff. 00:40:38.335 --> 00:40:40.710 If you're in an aerobatic airplane or something else that 00:40:40.710 --> 00:40:42.210 doesn't have flaps, you can actually 00:40:42.210 --> 00:40:45.180 slip and go sideways down towards the runway 00:40:45.180 --> 00:40:48.060 and get over the obstacles, but it's a lot easier 00:40:48.060 --> 00:40:49.720 just to put the flaps down. 00:40:49.720 --> 00:40:57.840 OK, the charts come in all kinds of variations in the POH, 00:40:57.840 --> 00:40:59.880 especially for the bigger airplanes. 00:40:59.880 --> 00:41:01.680 You'll have, you know, 10 charts that 00:41:01.680 --> 00:41:03.930 look identical except for a couple of numbers, 00:41:03.930 --> 00:41:07.590 like the exact flap position, whether the anti-icing is 00:41:07.590 --> 00:41:08.250 on or off. 00:41:11.220 --> 00:41:13.330 The Piper Warrior POH is a lot simpler, 00:41:13.330 --> 00:41:15.180 and that's some of the charts we're 00:41:15.180 --> 00:41:19.260 going to cover in addition to some of the anonymous airplane 00:41:19.260 --> 00:41:22.500 charts that the FAA gives you with the test. 00:41:22.500 --> 00:41:25.140 So one thing to remember if you're a renter, in addition 00:41:25.140 --> 00:41:28.410 to the fact that you want to build in maybe some charter 00:41:28.410 --> 00:41:31.290 and airline minimums into your flying, 00:41:31.290 --> 00:41:33.390 is that all those numbers were with the brand 00:41:33.390 --> 00:41:36.180 new airplane that was perfectly straight 00:41:36.180 --> 00:41:38.870 and had a perfect engine. 00:41:38.870 --> 00:41:42.300 OK, so wind components. 00:41:42.300 --> 00:41:44.580 You're going to get a shorter takeoff and landing 00:41:44.580 --> 00:41:47.300 distances with a headwind. 00:41:47.300 --> 00:41:49.260 A tailwind, actually, it may not be 00:41:49.260 --> 00:41:51.240 legal to operate a high performance 00:41:51.240 --> 00:41:53.533 aircraft on a runway with a tailwind of more 00:41:53.533 --> 00:41:54.450 than a certain amount. 00:41:54.450 --> 00:41:56.220 I think for the c.r. 00:41:56.220 --> 00:41:57.030 It was 10 knots. 00:41:57.030 --> 00:42:03.000 We just simply could not land with a 10 knot tailwind or more 00:42:03.000 --> 00:42:05.040 than a 10 knot tailwind. 00:42:05.040 --> 00:42:09.088 Crosswind is a little bit different. 00:42:09.088 --> 00:42:11.130 You'll get a max demonstrated crosswind component 00:42:11.130 --> 00:42:11.850 in the manual. 00:42:11.850 --> 00:42:14.760 So it'll tell you a test pilot managed 00:42:14.760 --> 00:42:17.520 to hold this airplane straight on the runway with full flaps, 00:42:17.520 --> 00:42:23.280 or whatever the normal landing configuration is, and there 00:42:23.280 --> 00:42:28.380 was enough rudder to land with a 15 knot crosswind. 00:42:28.380 --> 00:42:30.180 So that's max demonstrated. 00:42:30.180 --> 00:42:31.800 It's not a limitation. 00:42:31.800 --> 00:42:35.550 So if it is, it'll say, this is a limitation. 00:42:35.550 --> 00:42:39.000 But max demonstrated just means a test pilot did it. 00:42:39.000 --> 00:42:42.540 It'll probably work for you too if you manipulate 00:42:42.540 --> 00:42:44.280 the controls in the same way. 00:42:44.280 --> 00:42:47.160 And beyond that, you can't be sure. 00:42:47.160 --> 00:42:51.000 So one thing that people will do is 00:42:51.000 --> 00:42:56.440 they will adjust the flap amount to have-- 00:42:56.440 --> 00:42:59.670 a reduced use of flaps in a heavy crosswind, 00:42:59.670 --> 00:43:01.350 that keeps the airspeed up. 00:43:01.350 --> 00:43:02.853 You will chew up more runway. 00:43:02.853 --> 00:43:04.770 But when the wheels actually touch the ground, 00:43:04.770 --> 00:43:09.338 the wheels provide a little bit of stabilization and help 00:43:09.338 --> 00:43:11.130 keep you from getting blown off the runway. 00:43:11.130 --> 00:43:16.810 You're going to see tomorrow Dojo from the Brazilian Air 00:43:16.810 --> 00:43:21.030 Force is going to tell you about testing the various airplanes, 00:43:21.030 --> 00:43:25.980 but especially the Super Tucano, in very heavy crosswinds down 00:43:25.980 --> 00:43:27.900 there in South America. 00:43:27.900 --> 00:43:29.820 They have some pretty heavy winds. 00:43:29.820 --> 00:43:31.782 I think they went to Chile to do that. 00:43:31.782 --> 00:43:32.490 I could be wrong. 00:43:32.490 --> 00:43:35.770 Or maybe it was just right next to the Andes in Brazil. 00:43:35.770 --> 00:43:38.310 OK, crosswind chart. 00:43:38.310 --> 00:43:46.650 So this here shows you that, if you have a 40 knot wind at a 30 00:43:46.650 --> 00:43:51.510 degree angle, you go over here on the chart to the 30 degree 00:43:51.510 --> 00:44:00.030 line, you use this 40 knot ring, and then 00:44:00.030 --> 00:44:04.050 you can find that it's a 35 knot headwind and a 20 knot 00:44:04.050 --> 00:44:04.650 crosswind. 00:44:04.650 --> 00:44:06.780 Does that make sense? 00:44:06.780 --> 00:44:08.640 I will tell you when I was getting a type 00:44:08.640 --> 00:44:11.430 rating for this Cessna Mustang flight safety, 00:44:11.430 --> 00:44:14.220 there were a couple of Boeing 737 pilots there, 00:44:14.220 --> 00:44:16.410 and they had no idea how to use this chart. 00:44:16.410 --> 00:44:18.740 And they couldn't even give the right answers. 00:44:18.740 --> 00:44:23.610 If you said, you know, you're landing on runway 27 00:44:23.610 --> 00:44:27.690 and the wind's coming from 315, is that 00:44:27.690 --> 00:44:29.880 a tailwind or a headwind? 00:44:29.880 --> 00:44:33.290 And they couldn't answer that question either. 00:44:33.290 --> 00:44:36.640 Basically, all they do is go from towered airport 00:44:36.640 --> 00:44:37.560 to towered airport. 00:44:37.560 --> 00:44:40.212 The tower tells them what runway to use. 00:44:40.212 --> 00:44:41.670 They are from the Philippines, so I 00:44:41.670 --> 00:44:43.900 guess it's not insanely windy there 00:44:43.900 --> 00:44:46.020 like it would be in Argentina. 00:44:46.020 --> 00:44:49.170 I once landed in Argentina in Ushuaia 00:44:49.170 --> 00:44:52.860 on a commercial airline flight, and it was 50 knot-- 00:44:52.860 --> 00:44:56.400 the wind was, I think, 35 gusting 50. 00:44:56.400 --> 00:45:00.102 And the pilots, you know, I talked to them afterwards. 00:45:00.102 --> 00:45:01.560 They said it was just a normal day. 00:45:01.560 --> 00:45:05.160 They wouldn't even bother talking about that. 00:45:05.160 --> 00:45:09.330 So anyway, these skills apparently rest. 00:45:09.330 --> 00:45:11.760 I'm sure those guys, you know, had used a chart like that 00:45:11.760 --> 00:45:13.710 at one point in their training. 00:45:13.710 --> 00:45:16.102 They did get their type rating, so the good news 00:45:16.102 --> 00:45:18.060 is you can get your type rating without knowing 00:45:18.060 --> 00:45:19.030 how to use that. 00:45:19.030 --> 00:45:20.655 OK, here's one of the FAA charts. 00:45:20.655 --> 00:45:22.280 This is what they give you on the test. 00:45:22.280 --> 00:45:25.620 It's a lot easier to use than the POH. 00:45:25.620 --> 00:45:26.560 Here's a problem. 00:45:26.560 --> 00:45:29.250 They're giving you an example problem. 00:45:29.250 --> 00:45:29.820 Let's see. 00:45:29.820 --> 00:45:33.750 We're at somewhere in Colorado, apparently 5,650 feet. 00:45:33.750 --> 00:45:36.270 We weigh 2,950 pounds in this airplane 00:45:36.270 --> 00:45:38.250 that they won't tell us what it is. 00:45:38.250 --> 00:45:43.230 It's nine knots of headwind. 00:45:43.230 --> 00:45:44.730 Notice these associated conditions. 00:45:44.730 --> 00:45:46.230 These are really critical. 00:45:46.230 --> 00:45:48.780 And again, if they give you a choice of multiple charts, 00:45:48.780 --> 00:45:49.890 that's where the trick is. 00:45:49.890 --> 00:45:53.130 You know, they're trying to get you to use the wrong chart. 00:45:53.130 --> 00:45:56.380 That's more on the AP exam than on the private one. 00:45:56.380 --> 00:46:01.960 But yeah, see here, powerful throttle, cowl flaps are open. 00:46:01.960 --> 00:46:07.590 This is some kind of more complicated plane, 00:46:07.590 --> 00:46:10.440 that you got the right mixture set even before you take off 00:46:10.440 --> 00:46:11.910 for high altitude. 00:46:11.910 --> 00:46:15.100 All right, so what do we got here? 00:46:15.100 --> 00:46:17.767 We got temperature of 15. 00:46:17.767 --> 00:46:19.350 We go up to the air pressure altitude, 00:46:19.350 --> 00:46:21.162 pretty close to 6,000. 00:46:21.162 --> 00:46:22.620 We come over here, we're apparently 00:46:22.620 --> 00:46:24.787 right at gross weight, so at least that's realistic. 00:46:24.787 --> 00:46:30.840 Most aircraft take off right at gross weight for most flights. 00:46:30.840 --> 00:46:32.730 There's nine knots of wind, so that's 00:46:32.730 --> 00:46:35.830 going to subtract a little bit from our runway requirements. 00:46:35.830 --> 00:46:41.240 And here we can see it's 1,500 feet of ground roll 00:46:41.240 --> 00:46:42.920 and a little over-- 00:46:42.920 --> 00:46:44.645 what is that, 2,300? 00:46:44.645 --> 00:46:47.000 Yeah, 2,300 to clear the 50 foot obstacle. 00:46:47.000 --> 00:46:48.500 So these charts are not hard to use. 00:46:48.500 --> 00:46:52.550 And in the real world, maybe in the FAA figure, 00:46:52.550 --> 00:46:54.050 they actually give you this example. 00:46:54.050 --> 00:46:56.450 So you can see how it's done and then, you know, 00:46:56.450 --> 00:46:59.190 you just draw the lines in a different place. 00:46:59.190 --> 00:47:01.350 So they're not trying to trick you. 00:47:01.350 --> 00:47:04.610 Here's a chart for the Pilatus PC-12. 00:47:04.610 --> 00:47:06.490 There's also apps to do it, which 00:47:06.490 --> 00:47:10.300 I'll show you a little bit later, 00:47:10.300 --> 00:47:12.700 similar to that Piper chart we saw earlier 00:47:12.700 --> 00:47:15.700 where you calculate the density altitude without realizing 00:47:15.700 --> 00:47:18.650 that you've calculated it. 00:47:18.650 --> 00:47:20.660 Yeah, so here you've got pressure altitude 00:47:20.660 --> 00:47:22.670 and temperature, and you're implicitly 00:47:22.670 --> 00:47:24.620 calculating density altitude. 00:47:24.620 --> 00:47:26.042 Then you go over to weight. 00:47:26.042 --> 00:47:26.750 Look at this one. 00:47:26.750 --> 00:47:30.730 The Pilatus guys, I think they are having some fun here. 00:47:30.730 --> 00:47:33.580 They're saying you're taking off at 7,000 pounds. 00:47:33.580 --> 00:47:39.400 So you're missing almost 3,000 pounds of people and bags. 00:47:39.400 --> 00:47:41.290 You paid all this money for this airplane 00:47:41.290 --> 00:47:43.643 and you're barely using it. 00:47:43.643 --> 00:47:46.060 So I don't think that happens too often unless you've just 00:47:46.060 --> 00:47:49.470 dropped everybody off at an airport with no fuel 00:47:49.470 --> 00:47:50.572 and you're repositioning. 00:47:50.572 --> 00:47:52.030 Anyway, so you've got the headwind. 00:47:52.030 --> 00:47:54.655 They've got uphill and downhill all baked into this nice chart. 00:47:54.655 --> 00:47:56.620 You can get all these good numbers. 00:47:56.620 --> 00:48:00.570 This is why Cirrus is better, why they're the best seller. 00:48:00.570 --> 00:48:02.433 They just say, look, here is this table. 00:48:02.433 --> 00:48:03.850 There's a few corrections that you 00:48:03.850 --> 00:48:07.490 can use if you want to up there in the upper right 00:48:07.490 --> 00:48:09.890 for headwind, tailwind, grass. 00:48:09.890 --> 00:48:13.400 But basically, they make the usual case very simple 00:48:13.400 --> 00:48:17.540 of a level runway, a paved runway. 00:48:17.540 --> 00:48:20.210 It's always more conservative to go more. 00:48:20.210 --> 00:48:21.950 You know, you don't have to interpolate. 00:48:21.950 --> 00:48:24.450 You can just say, well, it's 25 degrees, 00:48:24.450 --> 00:48:26.360 so I'll use the 30 degree number. 00:48:31.790 --> 00:48:36.210 OK, what is the rate of climb here? 00:48:36.210 --> 00:48:39.630 We're in a gross weight of 1,670 pounds. 00:48:39.630 --> 00:48:42.290 It's 2,000 feet. 00:48:42.290 --> 00:48:44.190 How do we figure that out? 00:48:44.190 --> 00:48:47.810 This is one of the FAA example tables, 00:48:47.810 --> 00:48:52.850 and it's as simple as finding the right row in the table, row 00:48:52.850 --> 00:48:55.230 and column in the table. 00:48:55.230 --> 00:48:56.510 Or actually, have a look here. 00:48:56.510 --> 00:48:58.135 So they're saying the mixture has to be 00:48:58.135 --> 00:48:59.410 lean to get these numbers. 00:48:59.410 --> 00:49:00.490 The flaps have to be up. 00:49:00.490 --> 00:49:01.907 You've got to be at full throttle. 00:49:05.830 --> 00:49:07.810 OK, same deal, max rate of climb. 00:49:07.810 --> 00:49:09.931 I forget if this a-- 00:49:09.931 --> 00:49:14.090 this might be a paper chart, but you 00:49:14.090 --> 00:49:15.950 can see that associated conditions up there 00:49:15.950 --> 00:49:17.150 in the top left. 00:49:17.150 --> 00:49:20.560 That's absolutely critical. 00:49:20.560 --> 00:49:22.030 You know, The gross weight-- 00:49:22.030 --> 00:49:24.640 Cirrus, actually, a lot of the performance numbers 00:49:24.640 --> 00:49:29.470 in the Cirrus for cruise speed are at 2,600 pounds 00:49:29.470 --> 00:49:34.070 and you're flying along at 2,950 because you took off at 3,000. 00:49:34.070 --> 00:49:36.580 You're wondering, how come I'm not getting these numbers? 00:49:36.580 --> 00:49:41.420 But of course, you know, they're being optimistic about-- 00:49:41.420 --> 00:49:43.420 they're putting their airplane in the best light 00:49:43.420 --> 00:49:46.510 by positing some weight that probably 00:49:46.510 --> 00:49:48.430 doesn't exist in real life. 00:49:48.430 --> 00:49:53.230 All right, here they give us an example of 5,000 feet pressure 00:49:53.230 --> 00:50:01.410 altitude, OAT of 16 degrees, so ISA plus 11, max rate of climb, 00:50:01.410 --> 00:50:02.950 374. 00:50:02.950 --> 00:50:06.300 So I guess, yeah, 5,000 feet. 00:50:06.300 --> 00:50:07.390 Here's ISA plus 11. 00:50:07.390 --> 00:50:12.040 It says 376 with some kind of elaborate interpolation. 00:50:12.040 --> 00:50:14.680 I guess you find that last couple feet per minute 00:50:14.680 --> 00:50:15.430 that you subtract. 00:50:19.390 --> 00:50:20.590 Here's cruise charts. 00:50:20.590 --> 00:50:23.725 I think, again, this is from the FAA test supplement. 00:50:23.725 --> 00:50:25.600 They're just giving you-- remember I told you 00:50:25.600 --> 00:50:27.160 it would be ISA minus 20? 00:50:27.160 --> 00:50:28.380 That's the chart on the left. 00:50:28.380 --> 00:50:30.410 The one in the middle is the standard day. 00:50:30.410 --> 00:50:34.460 And on the right is a summer day, ISA plus 20. 00:50:34.460 --> 00:50:40.210 Notice that they'll give you fuel flow and the true airspeed 00:50:40.210 --> 00:50:43.340 given various engine speed and manifold pressure settings. 00:50:43.340 --> 00:50:46.800 This looks like it's for a piston twin. 00:50:46.800 --> 00:50:50.008 OK, landing performance is a pretty similar kind of chart. 00:50:50.008 --> 00:50:51.550 Not going to go through this exactly, 00:50:51.550 --> 00:50:54.580 but you can see they're giving you the worked example. 00:50:54.580 --> 00:50:56.720 And you come up with-- 00:50:56.720 --> 00:50:57.220 let's see. 00:50:57.220 --> 00:51:02.270 It's going to be about a little over 1,000 feet of ground 00:51:02.270 --> 00:51:11.070 roll and 1,700 feet, they claim, to clear a 50 foot obstacle. 00:51:11.070 --> 00:51:13.540 Here's an FAA question, actually. 00:51:13.540 --> 00:51:14.308 So let's see. 00:51:14.308 --> 00:51:16.350 Determine the total distance required for takeoff 00:51:16.350 --> 00:51:18.420 to clear a 50 foot obstacle. 00:51:18.420 --> 00:51:21.990 Standard temperature, sea level. 00:51:21.990 --> 00:51:23.700 So actually, this is testing you. 00:51:23.700 --> 00:51:25.470 This is pretty advanced, right? 00:51:25.470 --> 00:51:30.070 They're saying it's the standard temperature at sea level, 00:51:30.070 --> 00:51:34.770 so you have to know that it's 15 degrees. 00:51:34.770 --> 00:51:44.700 We only weigh 2,700 pounds, so we're 00:51:44.700 --> 00:51:50.190 going to have to ride down this curve a little bit. 00:51:50.190 --> 00:51:51.600 And the wind's calm, so we're not 00:51:51.600 --> 00:51:54.690 going to get any boost from the wind. 00:51:54.690 --> 00:51:56.870 So what do you guys think? 00:51:56.870 --> 00:51:59.580 Have any of you been able to kind of see 00:51:59.580 --> 00:52:02.520 what the most likely number is by following these? 00:52:07.760 --> 00:52:10.560 Somebody says A? 00:52:10.560 --> 00:52:11.510 Let's see. 00:52:11.510 --> 00:52:13.350 It's a little bit lighter. 00:52:13.350 --> 00:52:14.875 That kind of makes sense. 00:52:14.875 --> 00:52:16.250 But on the other hand, the wind's 00:52:16.250 --> 00:52:19.980 calm, so we didn't get that reduction from the wind. 00:52:19.980 --> 00:52:20.682 Let's see. 00:52:20.682 --> 00:52:22.140 So if we came down here, it's going 00:52:22.140 --> 00:52:28.270 to start from sea level, 15 degrees. 00:52:28.270 --> 00:52:29.080 Come over here. 00:52:29.080 --> 00:52:36.640 Come down here over a 50 foot obstacle, 00:52:36.640 --> 00:52:37.600 then we have to go up. 00:52:41.180 --> 00:52:43.300 Anybody want to revise their estimate? 00:52:43.300 --> 00:52:45.470 A, we heard A last time. 00:52:45.470 --> 00:52:47.750 It seems a little short to clear the 50 foot obstacle. 00:52:47.750 --> 00:52:50.060 I agree with you that you'd be well off the ground 00:52:50.060 --> 00:52:54.418 by 1,000 feet. 00:52:54.418 --> 00:52:54.918 Tada! 00:52:57.720 --> 00:52:59.940 All right, obviously, you know, if you 00:52:59.940 --> 00:53:05.850 have a pencil and a little more time to do that, it's easier. 00:53:05.850 --> 00:53:07.660 That's kind of the hard way. 00:53:07.660 --> 00:53:10.740 Let's look at the easy way. 00:53:10.740 --> 00:53:13.620 Getting the runway numbers for low performance aircraft, 00:53:13.620 --> 00:53:16.140 it actually remains pretty common to just use the POH. 00:53:16.140 --> 00:53:18.233 People aren't usually in a situation 00:53:18.233 --> 00:53:19.650 where they have to worry about it. 00:53:19.650 --> 00:53:21.942 If you're going from Hanscom Field or Martha's Vineyard 00:53:21.942 --> 00:53:23.370 and back, you know, both airports 00:53:23.370 --> 00:53:26.730 are big enough for a Boeing, and you're not 00:53:26.730 --> 00:53:29.940 going to be carefully calculating these numbers 00:53:29.940 --> 00:53:33.060 unless you really don't have much else to do. 00:53:33.060 --> 00:53:36.263 Apps, though, are available even for low performance aircraft, 00:53:36.263 --> 00:53:37.930 and they're very useful if you're going, 00:53:37.930 --> 00:53:40.020 you know, into tighter airports And you 00:53:40.020 --> 00:53:43.350 might have to worry about that. 00:53:43.350 --> 00:53:46.440 The time and fuel stuff is everywhere 00:53:46.440 --> 00:53:47.550 on the web and the apps. 00:53:47.550 --> 00:53:50.572 But the actual runway numbers are a little bit less common. 00:53:50.572 --> 00:53:52.030 Let me show you a couple of things. 00:53:52.030 --> 00:53:53.190 Here's Gyronimo. 00:53:55.870 --> 00:53:59.450 So they sell these for different aircraft. 00:53:59.450 --> 00:54:02.800 This is just off their website. 00:54:02.800 --> 00:54:07.130 And for an SR22, you can see you put in-- 00:54:07.130 --> 00:54:08.330 they must be European. 00:54:08.330 --> 00:54:11.890 They say aircraft mass 3,359. 00:54:11.890 --> 00:54:15.100 And you've got your temperature, your takeoff elevation, 00:54:15.100 --> 00:54:18.620 your altimeter, runway conditions. 00:54:18.620 --> 00:54:21.890 I don't know what that plus 5% is. 00:54:21.890 --> 00:54:26.370 Maybe they're saying-- oh, I don't know if that's between-- 00:54:26.370 --> 00:54:28.960 is it half grass and half paved? 00:54:28.960 --> 00:54:31.110 Anyway, you can put in everything relevant 00:54:31.110 --> 00:54:34.140 and it's going to tell you how much ground roll 00:54:34.140 --> 00:54:36.600 and how much takeoff distance. 00:54:36.600 --> 00:54:37.770 So that's pretty slick. 00:54:37.770 --> 00:54:42.500 It's a lot easier than relying on the POH. 00:54:42.500 --> 00:54:45.660 The calculator for the Pilatus is free. 00:54:45.660 --> 00:54:48.150 That's the good news. 00:54:48.150 --> 00:54:50.970 And here, same deal. 00:54:50.970 --> 00:54:55.650 You put in your weight, the temperature, 00:54:55.650 --> 00:54:58.380 if there's any headwind, the airport elevation, 00:54:58.380 --> 00:54:59.820 and you get the numbers. 00:55:03.300 --> 00:55:10.110 All right, we can try to get the doc camera working 00:55:10.110 --> 00:55:11.390 for a demo in a minute here. 00:55:11.390 --> 00:55:14.010 But in the meantime, first of all, are there questions? 00:55:14.010 --> 00:55:15.795 And secondly, what is this aircraft? 00:55:15.795 --> 00:55:16.920 And what's it designed for? 00:55:20.315 --> 00:55:21.770 AUDIENCE: Question about the test. 00:55:21.770 --> 00:55:28.725 Will it be on the [INAUDIBLE] for this class? 00:55:28.725 --> 00:55:30.240 Because it's online, right? 00:55:30.240 --> 00:55:31.240 PHILLIP GREENSPUN: Yeah. 00:55:31.240 --> 00:55:32.650 Well, you can print out the test supplement. 00:55:32.650 --> 00:55:33.310 That's public. 00:55:33.310 --> 00:55:34.270 It's in our Dropbox. 00:55:34.270 --> 00:55:36.700 And also, the FAA makes this chart supplement public, 00:55:36.700 --> 00:55:38.450 so you can see all the figures that you're 00:55:38.450 --> 00:55:41.945 going to see before the test. 00:55:41.945 --> 00:55:44.070 I think, actually, when you're done with your test, 00:55:44.070 --> 00:55:45.460 I think you can print out all the questions 00:55:45.460 --> 00:55:47.116 and it'll show you what you got right. 00:55:47.116 --> 00:55:47.658 AUDIENCE: OK. 00:55:47.658 --> 00:55:50.665 Because for the grass, this is going to be harder for me 00:55:50.665 --> 00:55:51.290 to [INAUDIBLE]. 00:55:51.290 --> 00:55:51.940 PHILLIP GREENSPUN: Oh, yeah. 00:55:51.940 --> 00:55:53.260 Yeah, just print out the chart. 00:55:53.260 --> 00:55:55.793 Yeah, sure, another chart supplement. 00:55:59.212 --> 00:56:01.420 Anybody have any brilliant ideas about this aircraft? 00:56:07.650 --> 00:56:08.880 It says Grizz on it. 00:56:12.233 --> 00:56:17.510 AUDIENCE: [INAUDIBLE] 00:56:17.510 --> 00:56:19.970 PHILLIP GREENSPUN: That's a Burt Rutan design, the climate 00:56:19.970 --> 00:56:20.750 change denier. 00:56:23.630 --> 00:56:27.620 And this is a super short field airplane. 00:56:27.620 --> 00:56:30.130 It actually doesn't land as short as you might think. 00:56:30.130 --> 00:56:31.880 I think it might be a four-seater, though, 00:56:31.880 --> 00:56:34.570 so I guess it is pretty darn short for a four-seater. 00:56:34.570 --> 00:56:37.280 But it has huge flaps and a lot of wing area, 00:56:37.280 --> 00:56:39.140 and it's got that-- 00:56:39.140 --> 00:56:41.040 I think it has ordinary-- 00:56:41.040 --> 00:56:45.220 Yeah, see, it has essentially three surfaces right? 00:56:45.220 --> 00:56:49.010 It's got kind of a helper wing or a canard 00:56:49.010 --> 00:56:52.700 out in front, the regular wing, and then 00:56:52.700 --> 00:56:54.650 an ordinary conventional tail plane. 00:56:59.460 --> 00:57:02.510 Let me see if I can get this doc camera working. 00:57:05.120 --> 00:57:08.190 All right, so let's say we want to know how much fuel we're 00:57:08.190 --> 00:57:09.600 going to use. 00:57:09.600 --> 00:57:11.190 See that fuel pounds there? 00:57:14.200 --> 00:57:15.160 Where is that? 00:57:18.140 --> 00:57:23.740 Somewhere along here-- well, actually, I 00:57:23.740 --> 00:57:29.470 happen to know it's got to be somewhere-- we're 10 pounds. 00:57:29.470 --> 00:57:31.720 Yeah, see, there's US gallons right there. 00:57:31.720 --> 00:57:33.730 So we line this up. 00:57:33.730 --> 00:57:36.100 And you can tell this was designed for piston folks, 00:57:36.100 --> 00:57:37.750 because their idea of fuel weight 00:57:37.750 --> 00:57:41.440 is six pounds per gallon, and jet fuel weighs 6.7. 00:57:41.440 --> 00:57:43.690 But at this point, now we've got our handy slide rule. 00:57:43.690 --> 00:57:50.280 So we know, if we load on, for example, 10 gallons of fuel, 00:57:50.280 --> 00:57:53.600 it's going to be 60 pounds. 00:57:53.600 --> 00:57:59.170 And the Cirrus holds 56 gallons, so that's 00:57:59.170 --> 00:58:02.770 going to weigh 300 and-- 00:58:02.770 --> 00:58:04.640 looks like 345. 00:58:04.640 --> 00:58:07.130 Oh, sorry, 335 gallons. 00:58:07.130 --> 00:58:08.470 335 pounds. 00:58:11.270 --> 00:58:18.290 More to the point, you can calculate density altitude. 00:58:18.290 --> 00:58:19.940 So over here, for example, you can 00:58:19.940 --> 00:58:24.050 say the pressure altitude is-- 00:58:24.050 --> 00:58:26.520 let's call it sea level. 00:58:26.520 --> 00:58:28.160 And it's very hot, though. 00:58:28.160 --> 00:58:29.850 It's plus 40 degrees. 00:58:29.850 --> 00:58:32.240 So now you see the density altitude up there 00:58:32.240 --> 00:58:34.190 is about 2,000 feet. 00:58:34.190 --> 00:58:36.050 Does that make sense? 00:58:36.050 --> 00:58:39.980 So you've set the pressure altitude at the bottom 00:58:39.980 --> 00:58:42.330 or inside this little window at zero, 00:58:42.330 --> 00:58:44.900 and then the density altitude gets read out here 00:58:44.900 --> 00:58:49.350 after you line it up with a temperature. 00:58:49.350 --> 00:58:53.130 There's also something that you can do, well, 00:58:53.130 --> 00:58:54.460 just with the basic rate. 00:58:54.460 --> 00:58:57.727 So let's say you decide that you're going to be going-- 00:58:57.727 --> 00:58:59.310 this is more for performance planning. 00:58:59.310 --> 00:59:05.250 But let's say you're a Cirrus and you're going 150 knots. 00:59:05.250 --> 00:59:11.250 If you end up needing to go, let's say, 300 nautical miles, 00:59:11.250 --> 00:59:14.310 it tells you that'll take you two hours. 00:59:14.310 --> 00:59:20.290 Not too exciting, but the wind side is a little more exciting. 00:59:20.290 --> 00:59:23.597 I'll bring a pencil tomorrow for the flight planning talk 00:59:23.597 --> 00:59:25.680 and we can play around with wind vectors on there. 00:59:25.680 --> 00:59:27.870 But anyway, fortunately, a lot of this stuff 00:59:27.870 --> 00:59:29.160 is explained in the book. 00:59:29.160 --> 00:59:32.580 You guys are free to come up and play around with it anytime. 00:59:32.580 --> 00:59:37.250 There's a temperature conversion scale here on the bottom. 00:59:37.250 --> 00:59:39.470 And it's a fun toy. 00:59:39.470 --> 00:59:43.110 Tina, anything else that we should cover here? 00:59:43.110 --> 00:59:44.070 Or should be segue? 00:59:44.070 --> 00:59:45.400 What's the next-- 00:59:45.400 --> 00:59:46.750 TINA SRIVASTAVA: So we're going to take questions, 00:59:46.750 --> 00:59:48.656 and then there's a short break, and then weather data. 00:59:48.656 --> 00:59:50.970 PHILLIP GREENSPUN: OK, the next one's weather data. 00:59:50.970 --> 00:59:54.000 You'll need a break for that one. 00:59:54.000 --> 00:59:56.080 That's how you find out all this stuff. 00:59:56.080 --> 00:59:58.050 Let me go back to the PC. 00:59:58.050 --> 01:00:01.660 Who else has questions? 01:00:01.660 --> 01:00:03.473 AUDIENCE: Can you go [INAUDIBLE]?? 01:00:06.877 --> 01:00:09.210 PHILLIP GREENSPUN: Go back over and look at a POH graph? 01:00:09.210 --> 01:00:09.930 AUDIENCE: Yeah. 01:00:09.930 --> 01:00:11.610 PHILLIP GREENSPUN: Which one? 01:00:11.610 --> 01:00:13.640 You want to do with the FAA exam ones? 01:00:13.640 --> 01:00:15.417 AUDIENCE: Yeah, the last one. 01:00:15.417 --> 01:00:17.250 PHILLIP GREENSPUN: Lane landing performance, 01:00:17.250 --> 01:00:19.470 or this one from the actual test? 01:00:19.470 --> 01:00:20.637 AUDIENCE: Yeah, [INAUDIBLE]. 01:00:20.637 --> 01:00:21.803 PHILLIP GREENSPUN: This one? 01:00:21.803 --> 01:00:23.110 AUDIENCE: Yeah. 01:00:23.110 --> 01:00:25.140 PHILLIP GREENSPUN: OK, so I don't think they 01:00:25.140 --> 01:00:26.940 ever give it worked out for you. 01:00:29.880 --> 01:00:34.210 Let me switch to the laser pointer mode. 01:00:34.210 --> 01:00:37.110 OK, so what do they tell us? 01:00:37.110 --> 01:00:38.990 They told us it was standard and sea level. 01:00:38.990 --> 01:00:40.907 That's the one part of the standard atmosphere 01:00:40.907 --> 01:00:43.270 that people, I think, are expected to remember, 01:00:43.270 --> 01:00:46.600 that at sea level it should be 15 degrees Celsius. 01:00:46.600 --> 01:00:48.240 So we come down here. 01:00:48.240 --> 01:00:50.310 We say it's 15 degrees out. 01:00:50.310 --> 01:00:53.670 We're going to hit the sea level pressure altitude. 01:00:53.670 --> 01:00:57.090 We're going to slide over this way, just like in the example. 01:00:59.760 --> 01:01:05.490 And then we're going to slide down, following this curve, 01:01:05.490 --> 01:01:07.590 to 2,700 pounds. 01:01:07.590 --> 01:01:11.320 And we're going to go over here, and we're going 01:01:11.320 --> 01:01:12.620 to say, look, there's no wind. 01:01:12.620 --> 01:01:16.720 The wind's calm, so we'll keep going over here, 01:01:16.720 --> 01:01:23.360 and we find that we need about a little less than 1,000 feet, 01:01:23.360 --> 01:01:27.932 maybe 800 feet, for a ground roll. 01:01:27.932 --> 01:01:30.140 But to clear the 50 foot obstacle, look at the bottom 01:01:30.140 --> 01:01:31.040 there. 01:01:31.040 --> 01:01:33.650 We need to go up, following one of these lines, 01:01:33.650 --> 01:01:37.190 and that's how we get to the 1,400 number. 01:01:37.190 --> 01:01:40.280 Did that help? 01:01:40.280 --> 01:01:42.590 You still look a little bit skeptical. 01:01:42.590 --> 01:01:45.920 AUDIENCE: Yeah, it just doesn't look like that line [INAUDIBLE] 01:01:45.920 --> 01:01:47.540 PHILLIP GREENSPUN: Well, remember, we 01:01:47.540 --> 01:01:50.882 would be doing this with a virtual pencil. 01:01:50.882 --> 01:01:52.340 These lines are just for reference, 01:01:52.340 --> 01:01:55.670 telling you kind of what slope to follow with your pencil. 01:01:55.670 --> 01:02:02.980 So it's not like these are the only available points. 01:02:02.980 --> 01:02:05.560 So it's not like it's going to be either this for the answer, 01:02:05.560 --> 01:02:07.560 or this for the answer, or this for your answer. 01:02:07.560 --> 01:02:08.970 Even in their worked example, you 01:02:08.970 --> 01:02:12.340 can see their red line for the answer is just parallel 01:02:12.340 --> 01:02:16.780 to that gray line. 01:02:16.780 --> 01:02:19.010 They're not picking one of the gray lines. 01:02:19.010 --> 01:02:21.640 So they're guidelines for how you should 01:02:21.640 --> 01:02:25.910 move your pencil in each phase. 01:02:25.910 --> 01:02:28.210 I hope this motivates you to buy that Gyronimo app. 01:02:28.210 --> 01:02:30.363 It certainly would motivate me to do it. 01:02:30.363 --> 01:02:32.780 TINA SRIVASTAVA: If you want to look at it on a real book, 01:02:32.780 --> 01:02:39.890 I'll pass around-- again, this is my POH for Cessna 172. 01:02:39.890 --> 01:02:41.930 So this might be the type of plane 01:02:41.930 --> 01:02:45.020 that you're using as your training aircraft. 01:02:45.020 --> 01:02:47.540 And I have a couple of pages that are 01:02:47.540 --> 01:02:49.280 marked with a piece of paper. 01:02:49.280 --> 01:02:53.360 So one talks about how you calculate the takeoff distance. 01:02:53.360 --> 01:02:54.815 And one is weight and balance. 01:02:54.815 --> 01:02:56.690 We'll actually have a whole section dedicated 01:02:56.690 --> 01:02:57.740 to weight and balance. 01:02:57.740 --> 01:02:59.720 But just to give you a sense of how 01:02:59.720 --> 01:03:02.030 you can follow with your pencil, and you'll actually 01:03:02.030 --> 01:03:05.840 see some pencil markings of my own fairly 01:03:05.840 --> 01:03:09.920 close to the limits here of our center of gravity moment 01:03:09.920 --> 01:03:11.970 envelope here, but still within the box, 01:03:11.970 --> 01:03:14.240 so just to give you an idea of how you can do that 01:03:14.240 --> 01:03:18.165 with a real paper and pencil. 01:03:18.165 --> 01:03:19.139 AUDIENCE: Yeah. 01:03:19.139 --> 01:03:34.390 [INAUDIBLE] So within that [INAUDIBLE] Is that the reason? 01:03:34.390 --> 01:03:35.390 PHILLIP GREENSPUN: Yeah. 01:03:35.390 --> 01:03:40.280 So the question is, you know, we don't have any kind of readout 01:03:40.280 --> 01:03:42.940 in the aircraft for density altitude. 01:03:42.940 --> 01:03:45.450 So is that why we're always calculating with our handy E6B 01:03:45.450 --> 01:03:49.380 or listening to the ASOS or whatever? 01:03:49.380 --> 01:03:49.880 So, yeah. 01:03:49.880 --> 01:03:51.880 Yeah, basically your instruments in the aircraft 01:03:51.880 --> 01:03:55.760 can tell you the temperature, outside air temperature, 01:03:55.760 --> 01:03:58.280 maybe not quite as accurate as the one from the airport 01:03:58.280 --> 01:03:59.750 if you're on the ground. 01:03:59.750 --> 01:04:02.540 And they can also show you, if you set your altimeter 01:04:02.540 --> 01:04:07.730 to two niner niner two, you can see the pressure altitude. 01:04:07.730 --> 01:04:10.300 But the relationship between the two is not simple. 01:04:10.300 --> 01:04:13.310 And there's nothing onboard the aircraft conventionally 01:04:13.310 --> 01:04:14.730 that will calculate it for you. 01:04:14.730 --> 01:04:16.230 And I don't think that's quite true. 01:04:16.230 --> 01:04:17.960 I think a lot of modern GPS boxes 01:04:17.960 --> 01:04:19.760 will do that calculation for you. 01:04:23.340 --> 01:04:25.140 But you have to type in all the numbers. 01:04:25.140 --> 01:04:27.170 They don't usually just grab it. 01:04:27.170 --> 01:04:29.630 They will give you things like true air speed. 01:04:29.630 --> 01:04:31.130 They'll definitely calculate that. 01:04:31.130 --> 01:04:33.703 So if you're indicating 150 but you're up really high, 01:04:33.703 --> 01:04:35.120 they'll tell you, well, now you're 01:04:35.120 --> 01:04:37.308 going 200 knots in true air speed, 01:04:37.308 --> 01:04:39.350 and then they'll give you your ground speed, too. 01:04:39.350 --> 01:04:41.360 And they'll even show you with a wind vector. 01:04:44.678 --> 01:04:46.220 TINA SRIVASTAVA: Any other questions? 01:04:50.370 --> 01:04:50.870 OK, great. 01:04:50.870 --> 01:04:53.180 So we'll just take a 10 minute break 01:04:53.180 --> 01:04:56.360 and start up again at 2:15 with weather data. 01:04:56.360 --> 01:04:58.640 And that's the one you guys seem to keep asking about, 01:04:58.640 --> 01:05:01.130 so we'll talk about also, towards the end 01:05:01.130 --> 01:05:05.890 of that talk, how you build your own ADS-B receiver.