WEBVTT 00:00:00.000 --> 00:00:01.952 [CLICKING] 00:00:13.352 --> 00:00:14.810 PHILIP GREENSPUN: All right, folks. 00:00:14.810 --> 00:00:15.880 Tina is going to tell you more. 00:00:15.880 --> 00:00:17.180 We had a little bit of weight and balance 00:00:17.180 --> 00:00:18.850 before that flight planning example, 00:00:18.850 --> 00:00:21.970 but Tina is now going to give you the real story. 00:00:24.807 --> 00:00:27.140 TINA SRIVASTAVA: So are guys all ready to go out and get 00:00:27.140 --> 00:00:29.960 your drone license? 00:00:29.960 --> 00:00:30.690 Good. 00:00:30.690 --> 00:00:31.480 I'm really glad. 00:00:31.480 --> 00:00:34.995 PHILIP GREENSPUN: [INAUDIBLE] 00:00:34.995 --> 00:00:36.120 TINA SRIVASTAVA: All right. 00:00:36.120 --> 00:00:41.020 Weight and balance So we talked a little bit. 00:00:41.020 --> 00:00:43.260 We've actually had quite a few discussions throughout 00:00:43.260 --> 00:00:47.310 about stability, about where the center of G 00:00:47.310 --> 00:00:49.800 is, how that affects your controllability 00:00:49.800 --> 00:00:51.070 of the aircraft. 00:00:51.070 --> 00:00:53.910 So weight and balance is not only an important thing 00:00:53.910 --> 00:00:55.770 to know, but it's a required thing 00:00:55.770 --> 00:00:59.080 that you have to do before you go flying each time. 00:00:59.080 --> 00:01:01.260 And one thing that's also relevant 00:01:01.260 --> 00:01:04.090 is to understand the center of gravity, 00:01:04.090 --> 00:01:06.090 and you want to make sure that center of gravity 00:01:06.090 --> 00:01:10.430 is within the limits for your given aircraft. 00:01:10.430 --> 00:01:13.360 So we talked about-- 00:01:13.360 --> 00:01:16.660 yesterday, when we were talking about aerodynamic flight, 00:01:16.660 --> 00:01:19.330 that certain aircraft have to be reinforced 00:01:19.330 --> 00:01:21.050 to do certain operations. 00:01:21.050 --> 00:01:22.860 So again, it really has to do with that. 00:01:22.860 --> 00:01:25.360 And by the way, from yesterday, mark 00:01:25.360 --> 00:01:29.815 left behind some of his aerodynamic procedure diagrams. 00:01:29.815 --> 00:01:33.340 So if you want to take a look at that, those are up front. 00:01:33.340 --> 00:01:34.840 Well, one thing that really you have 00:01:34.840 --> 00:01:37.900 to keep in mind in terms of what the aircraft can handle 00:01:37.900 --> 00:01:40.540 is just what is the max gross weight. 00:01:40.540 --> 00:01:45.700 So what can this airframe sustain, in terms of stresses 00:01:45.700 --> 00:01:47.570 on its body. 00:01:47.570 --> 00:01:51.350 We also talked this morning about performance 00:01:51.350 --> 00:01:56.270 and discussed certain things like the distance-- 00:01:56.270 --> 00:01:59.480 the length of the runway and the distance you need to take off 00:01:59.480 --> 00:02:02.960 are affected by how the airplane is weighted. 00:02:02.960 --> 00:02:06.410 So we're going to talk about those things specifically, 00:02:06.410 --> 00:02:08.780 and then one thing I have on here 00:02:08.780 --> 00:02:11.300 is if you go over your gross weight, 00:02:11.300 --> 00:02:14.600 then you get into test pilot territory, 00:02:14.600 --> 00:02:16.557 and right after this-- 00:02:16.557 --> 00:02:18.140 we'll grab lunch and come back-- we'll 00:02:18.140 --> 00:02:20.750 hear from [INAUDIBLE],, a test pilot who's 00:02:20.750 --> 00:02:24.450 going to tell you some really cool things as well. 00:02:24.450 --> 00:02:27.470 All right, so it's just some basic terms to get started off. 00:02:27.470 --> 00:02:30.320 So when you're thinking about an aircraft, 00:02:30.320 --> 00:02:33.920 one piece of information is its standard empty weight. 00:02:33.920 --> 00:02:36.140 So that's the weight of the airplane, 00:02:36.140 --> 00:02:39.110 and there's also some fuel in the tank 00:02:39.110 --> 00:02:43.670 that sometimes it's hard to drain, and when you refill, 00:02:43.670 --> 00:02:47.090 that fuel sits at the bottom and can't be used by the aircraft, 00:02:47.090 --> 00:02:49.370 so that's the unusable fuel, and then 00:02:49.370 --> 00:02:51.650 there's some different fluids and fuel 00:02:51.650 --> 00:02:52.940 oil inside the aircraft. 00:02:52.940 --> 00:02:55.490 So all those count in the calculation 00:02:55.490 --> 00:02:57.410 of the standard empty weight. 00:02:57.410 --> 00:02:59.390 There's also the basic empty weight, 00:02:59.390 --> 00:03:02.330 where you have some optional equipment inside, 00:03:02.330 --> 00:03:07.970 and we'll go to a aircraft's POH to look into what it actually 00:03:07.970 --> 00:03:09.365 reports about what it contains. 00:03:12.380 --> 00:03:13.790 There's also a good rule of thumb 00:03:13.790 --> 00:03:17.450 to know about what weight you're going to associate 00:03:17.450 --> 00:03:19.710 with the per gallon of fuel. 00:03:19.710 --> 00:03:23.240 So it's generally a good number is six pounds. 00:03:23.240 --> 00:03:24.710 For the fuel that you'll be using, 00:03:24.710 --> 00:03:28.965 it's slightly more for different types of fuel. 00:03:28.965 --> 00:03:30.590 So right at the beginning of the class, 00:03:30.590 --> 00:03:33.890 we talked about weight, which is the force pulling 00:03:33.890 --> 00:03:39.170 the aircraft down, which has to oppose the lift pulling it up. 00:03:39.170 --> 00:03:43.650 So the weight actually becomes less as you burn fuel. 00:03:43.650 --> 00:03:46.670 So when you take off, you have all the fuel on the aircraft. 00:03:46.670 --> 00:03:48.560 As you've been flying for a while, that 00:03:48.560 --> 00:03:52.820 fuel is used in the aircraft has less weight. 00:03:52.820 --> 00:03:55.960 So there's a fully loaded aircraft. 00:03:55.960 --> 00:03:59.020 Has something called the maximum ramp weight. 00:03:59.020 --> 00:04:02.530 So that has fuel that will be expended even 00:04:02.530 --> 00:04:05.440 when it's just taxiing over to the runway, 00:04:05.440 --> 00:04:08.590 and so you make certain assumptions about how 00:04:08.590 --> 00:04:10.240 much fuel you'll actually burn off 00:04:10.240 --> 00:04:14.710 just taxiing up to the runway and then before you take off. 00:04:14.710 --> 00:04:17.110 And so when you're calculating the weight of the airplane 00:04:17.110 --> 00:04:19.029 when it takes off, it'll be slightly 00:04:19.029 --> 00:04:21.940 different than how you fueled it when it was sitting parking 00:04:21.940 --> 00:04:24.580 on the ramp. 00:04:24.580 --> 00:04:27.500 OK, some of the biggest things that you 00:04:27.500 --> 00:04:29.870 would keep in mind that you change every time you 00:04:29.870 --> 00:04:31.160 get into the airplane. 00:04:31.160 --> 00:04:33.050 So there's the weight of the passengers, 00:04:33.050 --> 00:04:34.760 the baggage you take with you, and then 00:04:34.760 --> 00:04:39.260 how much fuel you fill the plane with before you take off. 00:04:39.260 --> 00:04:43.890 So the payload in this case is the passengers and the cargo. 00:04:43.890 --> 00:04:46.190 So whatever baggage and the weight of those bags 00:04:46.190 --> 00:04:49.190 that you take with you. 00:04:49.190 --> 00:04:53.160 So one thing to keep in mind in addition to just the weight, 00:04:53.160 --> 00:04:57.450 we have to figure out where that vector, that force vector, 00:04:57.450 --> 00:04:59.260 acts on the aircraft. 00:04:59.260 --> 00:05:01.253 If all of the weight is really at the front, 00:05:01.253 --> 00:05:02.670 you might have a center of gravity 00:05:02.670 --> 00:05:06.360 at the front, which will create a moment on the airplane. 00:05:06.360 --> 00:05:09.040 So it'll cause it to bend in a particular direction. 00:05:09.040 --> 00:05:10.650 And if all that weight was acting 00:05:10.650 --> 00:05:12.025 at the back of the plane, you had 00:05:12.025 --> 00:05:14.820 a lot of really heavy bricks at your tail, which is not 00:05:14.820 --> 00:05:17.520 a good idea, it would cause that force vector 00:05:17.520 --> 00:05:19.740 to act over here and create a moment. 00:05:19.740 --> 00:05:23.170 So that's all related to torque, which we talked about before. 00:05:23.170 --> 00:05:25.710 So it's also important, not just to calculate 00:05:25.710 --> 00:05:27.570 what the weight is of the airplane 00:05:27.570 --> 00:05:29.910 once everybody and everything is inside, 00:05:29.910 --> 00:05:33.540 but also how that weight is distributed in the airplane 00:05:33.540 --> 00:05:35.880 and how it affects the airplane's center of gravity. 00:05:38.780 --> 00:05:41.970 All right, so I think that many of you have already-- 00:05:41.970 --> 00:05:44.270 It looks like most folks in the rooms 00:05:44.270 --> 00:05:47.360 were either MIT undergrad or grad student, which 00:05:47.360 --> 00:05:50.240 means you already understand some of these basic physics 00:05:50.240 --> 00:05:52.820 terms about torque and moment, so we'll 00:05:52.820 --> 00:05:55.220 discover them very briefly. 00:05:55.220 --> 00:05:58.790 The moment is the weight times the arm. 00:05:58.790 --> 00:06:02.900 So basically where the wait is times how far away it 00:06:02.900 --> 00:06:05.900 is from a particular location that you're calculating it 00:06:05.900 --> 00:06:06.800 from. 00:06:06.800 --> 00:06:10.140 So we're going to do a couple basic examples. 00:06:10.140 --> 00:06:12.090 So we have a seesaw here. 00:06:12.090 --> 00:06:15.980 So in this case, whenever you're calculating your moment, 00:06:15.980 --> 00:06:17.630 you have to pick a reference point 00:06:17.630 --> 00:06:21.690 and make sure you're consistent as you use it. 00:06:21.690 --> 00:06:25.210 So in this case, they have a-- 00:06:25.210 --> 00:06:27.620 their data point is at that triangle 00:06:27.620 --> 00:06:29.990 at that fulcrum in the middle, and so they 00:06:29.990 --> 00:06:33.260 have a moment on the right and a moment on the left. 00:06:33.260 --> 00:06:35.840 So you see various rectangles that 00:06:35.840 --> 00:06:39.440 represent different objects or different weight, 00:06:39.440 --> 00:06:40.670 and then they calculate it. 00:06:40.670 --> 00:06:45.290 So that blue box that's five pounds is 10 inches away. 00:06:45.290 --> 00:06:48.170 So to figure out what the moment is that it applies, 00:06:48.170 --> 00:06:52.330 you just calculate the weight times how far away is. 00:06:52.330 --> 00:06:56.350 OK, so in order to figure out what the center of gravity is, 00:06:56.350 --> 00:06:59.290 you might want to consider where you're 00:06:59.290 --> 00:07:00.830 doing that reference point. 00:07:00.830 --> 00:07:02.890 So rather than doing the reference point 00:07:02.890 --> 00:07:05.583 from right in the middle of the aircraft, in this case, 00:07:05.583 --> 00:07:06.750 they're starting at the end. 00:07:06.750 --> 00:07:08.500 So where that yellow line is where it says 00:07:08.500 --> 00:07:11.710 datum is where they're starting, and then they're 00:07:11.710 --> 00:07:14.660 using the length from that same reference point. 00:07:14.660 --> 00:07:17.650 So now you have a purple box of five pounds 00:07:17.650 --> 00:07:21.280 that's 10 inches from that datum, and then three pounds 00:07:21.280 --> 00:07:23.650 then a green weight that's father, 00:07:23.650 --> 00:07:26.830 and the red box that's the farthest away. 00:07:26.830 --> 00:07:30.840 So here they've listed all those different boxes 00:07:30.840 --> 00:07:34.660 and the weight of each of those boxes times how far it is. 00:07:34.660 --> 00:07:37.780 You multiply that to get the moment that it applies. 00:07:37.780 --> 00:07:40.420 And use that to calculate the location 00:07:40.420 --> 00:07:41.890 of the center of gravity. 00:07:45.140 --> 00:07:49.160 And just in terms of if you've been on a seesaw before, 00:07:49.160 --> 00:07:51.893 who has been on a seesaw before? 00:07:51.893 --> 00:07:52.560 All right, good. 00:07:52.560 --> 00:07:54.030 I'm glad. 00:07:54.030 --> 00:07:57.090 So as you know that that fulcrum or where 00:07:57.090 --> 00:07:59.520 that triangle is, if you put that triangle 00:07:59.520 --> 00:08:01.150 at the center of gravity. 00:08:01.150 --> 00:08:04.343 So all the kids sitting on one side of the seesaw 00:08:04.343 --> 00:08:05.760 weigh the same as the kids sitting 00:08:05.760 --> 00:08:08.640 on the other side of the seesaw at the appropriate lengths 00:08:08.640 --> 00:08:10.830 away, so they're applying the same moment. 00:08:10.830 --> 00:08:12.940 Then the fulcrum balances. 00:08:12.940 --> 00:08:15.750 So if we determined what the center of gravity 00:08:15.750 --> 00:08:18.618 of this airplane was and I put my finger there, 00:08:18.618 --> 00:08:20.160 then it would balance and it wouldn't 00:08:20.160 --> 00:08:22.400 tilt one way or the other. 00:08:22.400 --> 00:08:25.380 So that's the whole idea. 00:08:25.380 --> 00:08:28.980 So for a given aircraft, there is not only 00:08:28.980 --> 00:08:33.210 the center of gravity, but in the testing process, 00:08:33.210 --> 00:08:36.480 they understand what is that approved range of where 00:08:36.480 --> 00:08:39.780 that center of gravity can be such that the aircraft is still 00:08:39.780 --> 00:08:41.100 stable. 00:08:41.100 --> 00:08:44.220 So if you're thinking about putting a lot of weight 00:08:44.220 --> 00:08:47.820 at the front of the aircraft and less weight 00:08:47.820 --> 00:08:50.250 at the back of the aircraft, then the center of gravity 00:08:50.250 --> 00:08:52.590 moves forward, and there's a limit 00:08:52.590 --> 00:08:55.350 to how far forward that center of gravity 00:08:55.350 --> 00:08:59.160 can be that allows the plane still to be stable. 00:08:59.160 --> 00:09:01.740 So that's the forward CG limit, and then you 00:09:01.740 --> 00:09:03.120 see the same thing at the back. 00:09:03.120 --> 00:09:06.330 Aft just means back, so how far back the center of gravity 00:09:06.330 --> 00:09:09.010 can be. 00:09:09.010 --> 00:09:10.840 All right, so we've already discussed some 00:09:10.840 --> 00:09:14.320 of the performance things, but just to just to remind you, 00:09:14.320 --> 00:09:18.280 what are some of the things that can happen if your air plane is 00:09:18.280 --> 00:09:20.540 overloaded? 00:09:20.540 --> 00:09:22.670 You want to just a shout out some things 00:09:22.670 --> 00:09:24.230 that you would experience if you have 00:09:24.230 --> 00:09:27.314 a very, very heavy airplane. 00:09:27.314 --> 00:09:29.110 AUDIENCE: Longer take off. 00:09:29.110 --> 00:09:31.600 TINA SRIVASTAVA: Yes, very good. 00:09:31.600 --> 00:09:33.760 Just to repeat it, longer to take off. 00:09:33.760 --> 00:09:37.010 So we have takeoff and landing distances increase. 00:09:37.010 --> 00:09:39.280 So if you have a very heavy airplane, 00:09:39.280 --> 00:09:44.085 you may not be able to take off from a short field runway. 00:09:44.085 --> 00:09:45.460 And then of course it was talking 00:09:45.460 --> 00:09:49.990 about if your aircraft gets outside the approved envelope, 00:09:49.990 --> 00:09:52.380 it will talk about what we mean by envelope, 00:09:52.380 --> 00:09:57.640 then it hasn't been tested to be stable at those areas, 00:09:57.640 --> 00:10:00.340 and so now you've become a test pilot, which you may not 00:10:00.340 --> 00:10:01.490 want to do. 00:10:01.490 --> 00:10:05.630 Again, we're going to hear from a test pilot very soon. 00:10:05.630 --> 00:10:07.560 OK, so what happens if-- not just 00:10:07.560 --> 00:10:09.480 that it's overloaded, maybe it's still 00:10:09.480 --> 00:10:12.910 within the envelope for the total amount of weight, 00:10:12.910 --> 00:10:15.210 but what if the center of gravity 00:10:15.210 --> 00:10:19.080 has moved too far forward and pass that forward CG limit. 00:10:19.080 --> 00:10:22.500 So your plane naturally wants to be nose down. 00:10:22.500 --> 00:10:24.060 So what is the impact of that? 00:10:28.240 --> 00:10:30.450 Well, it'd be harder to climb, right? 00:10:30.450 --> 00:10:32.900 It's harder to climb because your nose keeps 00:10:32.900 --> 00:10:36.350 pulling it down, for example. 00:10:36.350 --> 00:10:39.650 What does it mean to have a stall speed increased? 00:10:39.650 --> 00:10:41.424 Is that a good thing? 00:10:41.424 --> 00:10:43.322 AUDIENCE: No. 00:10:43.322 --> 00:10:44.530 TINA SRIVASTAVA: And why not? 00:10:44.530 --> 00:10:45.820 Why is it not a good thing? 00:10:49.540 --> 00:10:51.870 AUDIENCE: [INAUDIBLE] 00:10:51.870 --> 00:10:54.450 TINA SRIVASTAVA: Yeah, so basically, if your stall speed 00:10:54.450 --> 00:10:58.590 has increased, that means you're likely to stall at a higher 00:10:58.590 --> 00:10:59.530 speed. 00:10:59.530 --> 00:11:04.020 So if traditionally can fly at 60 knots 00:11:04.020 --> 00:11:07.260 without stalling but that stall speed has increased from 00:11:07.260 --> 00:11:09.900 say 40 knots up to 60 knots, that 00:11:09.900 --> 00:11:11.460 means that when you traditionally 00:11:11.460 --> 00:11:13.320 have been able to fly safely at 60 knots, 00:11:13.320 --> 00:11:15.000 you could actually stall at 60 knots. 00:11:15.000 --> 00:11:19.250 So an increased stall speed is bad. 00:11:19.250 --> 00:11:20.960 And what about an aft CG? 00:11:20.960 --> 00:11:24.170 Having the weight too far to the back. 00:11:24.170 --> 00:11:27.915 What is the impact there? 00:11:27.915 --> 00:11:29.390 AUDIENCE: They pitch up. 00:11:29.390 --> 00:11:30.260 TINA SRIVASTAVA: They tend to pitch up. 00:11:30.260 --> 00:11:30.760 Right. 00:11:30.760 --> 00:11:35.150 And so one thing that they are talking about here is flare. 00:11:35.150 --> 00:11:38.810 So this is when you're coming into land, you go down, 00:11:38.810 --> 00:11:43.400 but then you flare up, and it could actually over flare, 00:11:43.400 --> 00:11:46.220 and that can cause some really strange things when you're 00:11:46.220 --> 00:11:47.870 trying to land, such as bouncing, 00:11:47.870 --> 00:11:49.720 and you definitely don't want to do that. 00:11:49.720 --> 00:11:51.470 But all of these things you might actually 00:11:51.470 --> 00:11:54.260 just notice when you're feeling the airplane. 00:11:54.260 --> 00:11:56.930 It acts differently than you want it to act. 00:11:59.660 --> 00:12:02.840 So here's just basically a cross section. 00:12:02.840 --> 00:12:05.900 If you took off the wings and the top of the fuselage 00:12:05.900 --> 00:12:07.340 and you were looking at the plane, 00:12:07.340 --> 00:12:10.140 it shows you the pilot sitting in the left seat, 00:12:10.140 --> 00:12:13.490 a passenger in the right seat, two passengers in the back. 00:12:13.490 --> 00:12:17.210 This one actually has a third row of passengers, and then 00:12:17.210 --> 00:12:19.280 two baggage compartments. 00:12:19.280 --> 00:12:20.960 So this is just showing-- 00:12:20.960 --> 00:12:23.210 traditionally, when you're loading up an airplane, 00:12:23.210 --> 00:12:26.300 they payload again is your passengers and your baggage, 00:12:26.300 --> 00:12:28.225 where do they sit? 00:12:28.225 --> 00:12:30.350 So now I'm going to go over to this document viewer 00:12:30.350 --> 00:12:32.130 and talk about specific airplane. 00:12:32.130 --> 00:12:39.220 The plane I like to fly, a Cessna 172. 00:12:39.220 --> 00:12:44.310 OK, so this book is talking about a particular aircraft, 00:12:44.310 --> 00:12:48.520 a Skyhawk, so it's a Cessna 172. 00:12:48.520 --> 00:12:50.290 This is a plane that many of you guys 00:12:50.290 --> 00:12:53.110 might use as a flying aircraft. 00:12:53.110 --> 00:12:54.640 We've also talked about for example 00:12:54.640 --> 00:12:57.760 a Piper, which is a low wing airplane that you might use. 00:12:57.760 --> 00:12:59.260 So this is what a Cessna looks like, 00:12:59.260 --> 00:13:02.770 and it has a tricycle gear at the bottom. 00:13:02.770 --> 00:13:05.550 Whatever plane you are using for training, 00:13:05.550 --> 00:13:07.960 I would get very familiar with this book, 00:13:07.960 --> 00:13:11.550 and in particular, remember what the table of contents is. 00:13:11.550 --> 00:13:16.440 Because when you get your oral exam on your FAA examination, 00:13:16.440 --> 00:13:18.390 it's OK if you don't remember everything. 00:13:18.390 --> 00:13:21.180 What's really great is if you know how to find information, 00:13:21.180 --> 00:13:24.630 and you can say, hey, if I didn't remember this, 00:13:24.630 --> 00:13:27.480 I would go look at my POH, and I would go look 00:13:27.480 --> 00:13:30.850 at the weight and balance section, section 6 of my book, 00:13:30.850 --> 00:13:33.870 and I'd be able to flip and find this information very quickly. 00:13:33.870 --> 00:13:36.113 So oftentimes, you'll get questions in that oral exam 00:13:36.113 --> 00:13:37.530 where they would ask how you would 00:13:37.530 --> 00:13:39.630 go about finding information. 00:13:39.630 --> 00:13:41.850 We discussed that a lot with regard to weather data. 00:13:41.850 --> 00:13:43.600 What are the sources of weather data, 00:13:43.600 --> 00:13:45.450 so with regard to weight and balance, 00:13:45.450 --> 00:13:47.580 the information about your airplane 00:13:47.580 --> 00:13:51.720 is found with a book made about your particular airplane. 00:13:51.720 --> 00:13:54.220 And if you're at a particular flight school, 00:13:54.220 --> 00:13:56.840 and we'll show you that in an example, 00:13:56.840 --> 00:13:59.340 they might have a-- they most likely have all of this weight 00:13:59.340 --> 00:14:02.040 and balance information listed in a spreadsheet, 00:14:02.040 --> 00:14:04.110 sometimes it's accessible online so you 00:14:04.110 --> 00:14:07.380 know for your exact airplane what its gross weight is. 00:14:10.040 --> 00:14:14.320 So if we flip to that section 6, it 00:14:14.320 --> 00:14:16.660 has a fair amount of information, including 00:14:16.660 --> 00:14:18.340 the picture we just showed you. 00:14:21.210 --> 00:14:24.060 So it talks about-- 00:14:24.060 --> 00:14:26.730 in this case, there are only two rows of seats. 00:14:26.730 --> 00:14:29.460 So that the pilot and passenger, one row of seats, 00:14:29.460 --> 00:14:32.912 so it seats four people, and then it has a baggage area. 00:14:32.912 --> 00:14:34.620 But what's really important to understand 00:14:34.620 --> 00:14:37.800 is that even though the Cessna can fit four people, 00:14:37.800 --> 00:14:43.620 it will show you that if you put four 200 pound people in there 00:14:43.620 --> 00:14:46.848 with a bunch of bags, you'll actually exceed the allotment. 00:14:46.848 --> 00:14:48.390 So just because there are four seats, 00:14:48.390 --> 00:14:51.660 doesn't mean you can take four large people on a flight. 00:14:51.660 --> 00:14:54.930 Some of it is something we'll keep in mind, 00:14:54.930 --> 00:14:58.650 and maybe you can reduce bags and reduce fuel such that you 00:14:58.650 --> 00:14:59.970 can make that weight workout. 00:15:02.730 --> 00:15:04.220 So we talked about envelopes. 00:15:08.580 --> 00:15:12.510 So the envelope is basically a line 00:15:12.510 --> 00:15:17.340 on this graph that shows where the center of gravity can be, 00:15:17.340 --> 00:15:19.770 and the envelope is where is it safe to be. 00:15:19.770 --> 00:15:22.260 So if you're inside the envelope, 00:15:22.260 --> 00:15:26.460 so inside this line, if your calculations result 00:15:26.460 --> 00:15:28.620 in a center of gravity inside, then you're 00:15:28.620 --> 00:15:29.920 within the envelope. 00:15:29.920 --> 00:15:32.745 If you're outside of it, then you're not. 00:15:32.745 --> 00:15:36.660 You can see a little pencil mark towards the top 00:15:36.660 --> 00:15:38.850 where I took a flight recently, and I 00:15:38.850 --> 00:15:41.820 was trying to calculate whether or not I was inside 00:15:41.820 --> 00:15:43.140 and in fact I was. 00:15:43.140 --> 00:15:45.930 And it's OK that I'm right at the edge of the envelope. 00:15:45.930 --> 00:15:47.670 As long as you're inside, you're still 00:15:47.670 --> 00:15:50.190 with inside the tested limits. 00:15:50.190 --> 00:15:52.230 Now, there are two different categories 00:15:52.230 --> 00:15:53.640 or two different lines here. 00:15:53.640 --> 00:15:56.520 There's a bigger line that says normal category, 00:15:56.520 --> 00:15:58.860 and then there's a smaller line-- 00:15:58.860 --> 00:16:02.380 smaller envelope-- that's talking about utility category. 00:16:02.380 --> 00:16:03.880 Does anyone know what the difference 00:16:03.880 --> 00:16:06.338 is between normal and utility? 00:16:06.338 --> 00:16:08.290 AUDIENCE: G limits. 00:16:08.290 --> 00:16:09.940 TINA SRIVASTAVA: G limits. 00:16:09.940 --> 00:16:12.110 Is that what you're going to say? 00:16:12.110 --> 00:16:14.200 So there's different restrictions. 00:16:16.562 --> 00:16:18.520 One question you might get asked is, how do you 00:16:18.520 --> 00:16:19.900 find out where the answer is? 00:16:29.312 --> 00:16:30.270 And it's right in here. 00:16:30.270 --> 00:16:31.437 Right where you think it is. 00:16:34.330 --> 00:16:37.530 And I'm actually going to show you real examples, 00:16:37.530 --> 00:16:42.490 so we're going to go through an example of loading up 00:16:42.490 --> 00:16:44.087 an airplane. 00:16:44.087 --> 00:16:45.670 Don't want to embarrass anyone, but we 00:16:45.670 --> 00:16:47.795 might ask some of you what your weight is. 00:16:47.795 --> 00:16:48.295 So beware. 00:16:51.470 --> 00:16:54.730 So every time you have to calculate your weight 00:16:54.730 --> 00:16:56.570 and balance, you can do it by hand, 00:16:56.570 --> 00:16:58.990 or you can use a computer to do it, 00:16:58.990 --> 00:17:02.560 and I would just caution that you have to double check 00:17:02.560 --> 00:17:03.490 all the information. 00:17:03.490 --> 00:17:06.819 So here's a great link that tells you 00:17:06.819 --> 00:17:11.869 for a particular Cessna 172, a weight and balance calculator. 00:17:11.869 --> 00:17:15.790 So here, you can actually type in the empty weight. 00:17:15.790 --> 00:17:19.152 Now, there's a big Warning here, use your own AC data. 00:17:19.152 --> 00:17:19.985 What is that saying? 00:17:23.800 --> 00:17:24.619 What is AC? 00:17:24.619 --> 00:17:25.430 AUDIENCE: Aircraft. 00:17:25.430 --> 00:17:26.000 TINA SRIVASTAVA: Aircraft. 00:17:26.000 --> 00:17:27.380 Use your own aircraft's data. 00:17:27.380 --> 00:17:30.440 So look at your actual information 00:17:30.440 --> 00:17:33.890 from your school to figure out for the plane 00:17:33.890 --> 00:17:38.270 that you're renting what those pieces of information are. 00:17:38.270 --> 00:17:42.020 So here is a link from east coast aero club 00:17:42.020 --> 00:17:44.030 just as an example, and they have 00:17:44.030 --> 00:17:46.880 provided for every aircraft that they 00:17:46.880 --> 00:17:49.740 have a bunch of information. 00:17:53.390 --> 00:17:57.310 So for each aircraft, they have provided the empty weight 00:17:57.310 --> 00:18:01.450 and the CG, the moment, gross weight, useful load, 00:18:01.450 --> 00:18:04.810 and then they also talk about two different settings 00:18:04.810 --> 00:18:05.750 for fuel. 00:18:05.750 --> 00:18:09.700 So you can have full fuel or fuel to tabs. 00:18:09.700 --> 00:18:13.570 So that is something you'll hear pretty frequently. 00:18:13.570 --> 00:18:15.200 Fill the fuel to tabs. 00:18:15.200 --> 00:18:19.780 So if you want to have extra mass, extra weight 00:18:19.780 --> 00:18:23.120 in your plane, you have some heavier folks flying with you, 00:18:23.120 --> 00:18:25.480 you might only want the fuel to tabs. 00:18:25.480 --> 00:18:27.550 But if it's just you or you and your instructor 00:18:27.550 --> 00:18:29.590 and you want to fly a cross-country flight, 00:18:29.590 --> 00:18:31.360 you might want to fuel full. 00:18:31.360 --> 00:18:34.760 So these are all things you can change. 00:18:34.760 --> 00:18:36.960 This calculator has some restrictions, 00:18:36.960 --> 00:18:43.610 which is that the weight is identified here in terms of-- 00:18:43.610 --> 00:18:44.945 so they have the oil. 00:18:44.945 --> 00:18:48.290 So you might want to check what is the oil 00:18:48.290 --> 00:18:50.600 level inside your engine. 00:18:50.600 --> 00:18:54.638 For a Cessna 172, six quarts is a really good number to have, 00:18:54.638 --> 00:18:56.930 but you check it every time and during your pre-flight. 00:18:56.930 --> 00:18:59.365 It could be five quarts, it could be seven quarts, 00:18:59.365 --> 00:19:00.740 so you want to double check that. 00:19:00.740 --> 00:19:02.980 And of course, if you see that it's low, 00:19:02.980 --> 00:19:05.000 four quarts, you really want to ask someone 00:19:05.000 --> 00:19:07.700 to fill that up before you go flying. 00:19:07.700 --> 00:19:09.980 But the other thing here is you actually 00:19:09.980 --> 00:19:13.970 list the weight of the people that are sitting 00:19:13.970 --> 00:19:15.680 in the front and the back. 00:19:15.680 --> 00:19:18.410 So I talked about embarrassing folks. 00:19:18.410 --> 00:19:20.900 Well, let's not let's not embarrass folks right now. 00:19:20.900 --> 00:19:23.990 So let's say the pilot and let's say 00:19:23.990 --> 00:19:26.330 you're doing some great resource management. 00:19:26.330 --> 00:19:28.385 You have another pilot sitting next to you, 00:19:28.385 --> 00:19:32.540 so your co-pilot is there, and you also 00:19:32.540 --> 00:19:37.220 have some big folks sitting in the back, both the left 00:19:37.220 --> 00:19:38.540 and the right side. 00:19:38.540 --> 00:19:42.050 And you want to take a bunch of pictures and stuff, 00:19:42.050 --> 00:19:44.340 but you want to get as low as you want, 00:19:44.340 --> 00:19:46.430 so you put in some bags. 00:19:46.430 --> 00:19:49.870 So this-- it's actually hard to see because there's 00:19:49.870 --> 00:19:51.040 too much weight. 00:19:51.040 --> 00:19:54.970 This red little plus sign is showing 00:19:54.970 --> 00:19:57.820 where your center of gravity fell 00:19:57.820 --> 00:20:02.560 and whether it's within that utility or normal category. 00:20:02.560 --> 00:20:05.660 So in this case, we have three people. 00:20:05.660 --> 00:20:08.350 Front two are 200 pounds each, one person 00:20:08.350 --> 00:20:13.110 in the rear with 200, and bags there weighing about 10 pounds. 00:20:13.110 --> 00:20:16.630 Is this safe to fly? 00:20:16.630 --> 00:20:20.560 No, so you're a little red dot went outside the limits. 00:20:20.560 --> 00:20:23.470 If you have a much smaller person sitting 00:20:23.470 --> 00:20:26.500 in the back seat, you cross over that line, 00:20:26.500 --> 00:20:28.960 and now you're back into the normal categories 00:20:28.960 --> 00:20:30.490 so you can fly. 00:20:30.490 --> 00:20:33.070 Again, another thing you can alter 00:20:33.070 --> 00:20:38.870 is, of course, you fill the fuel to tabs. 00:20:38.870 --> 00:20:41.010 So this is also talking about-- 00:20:41.010 --> 00:20:47.143 so most of the time in the POH book, so the section 6 00:20:47.143 --> 00:20:48.310 is about weight and balance. 00:20:48.310 --> 00:20:49.820 So although the one example I just 00:20:49.820 --> 00:20:53.660 showed you was for a Cessna 172, the Piper Warrior 00:20:53.660 --> 00:20:56.210 also has that consistent, so really 00:20:56.210 --> 00:21:01.790 recommend just memorizing the table of contents for your POH. 00:21:01.790 --> 00:21:05.930 So the way that you go about calculating it 00:21:05.930 --> 00:21:08.540 is the same way we entered it into their little calculator. 00:21:08.540 --> 00:21:11.870 So first you have to determine the basic empty weight 00:21:11.870 --> 00:21:15.110 of the aircraft and then the moment. 00:21:15.110 --> 00:21:18.740 Section 6 almost always also has a place for you 00:21:18.740 --> 00:21:21.020 to do that calculation, and so they 00:21:21.020 --> 00:21:23.240 have a place right there where you 00:21:23.240 --> 00:21:26.750 can enter in your airplane, the moment, 00:21:26.750 --> 00:21:29.570 and it does the same steps that we just saw on the slide. 00:21:29.570 --> 00:21:31.850 So you start with that basic empty weight, 00:21:31.850 --> 00:21:35.180 then you focus on the fuel, and it gives you 00:21:35.180 --> 00:21:38.330 the 6 pounds per gallon is what you're 00:21:38.330 --> 00:21:41.370 going to most likely be using. 00:21:41.370 --> 00:21:43.710 What is the max number of gallons? 00:21:43.710 --> 00:21:46.440 What is the amount for tabs? 00:21:46.440 --> 00:21:49.200 You want to actually look this up for your airplane. 00:21:49.200 --> 00:21:51.960 The weight of the pilot in the front passenger, 00:21:51.960 --> 00:21:55.320 rear passengers, and the baggage area, and then you 00:21:55.320 --> 00:21:57.630 get this ramp weight. 00:21:57.630 --> 00:21:59.580 And as I talked about, you can actually 00:21:59.580 --> 00:22:02.730 have your plane be a little heavier than the envelope right 00:22:02.730 --> 00:22:04.680 when it's fueled on the ramp because there's 00:22:04.680 --> 00:22:08.898 some allowance for the fuel that you'll burn off during a taxi, 00:22:08.898 --> 00:22:09.940 and so that's right here. 00:22:09.940 --> 00:22:13.110 So fuel allowance for engine start, taxi, and run up. 00:22:13.110 --> 00:22:16.380 So they took off about eight pounds over there, 00:22:16.380 --> 00:22:17.970 and then you can calculate it. 00:22:17.970 --> 00:22:20.070 And once you locate the point, then you 00:22:20.070 --> 00:22:23.470 go to that diagram right here. 00:22:23.470 --> 00:22:25.690 So you go to the weight and the moment, 00:22:25.690 --> 00:22:29.698 and you figure out whether or not you're in the safe-- 00:22:29.698 --> 00:22:31.240 whether or not you're in the envelope 00:22:31.240 --> 00:22:35.760 for that normal category of aircraft. 00:22:35.760 --> 00:22:37.980 So what we just went through is the same procedure 00:22:37.980 --> 00:22:39.120 that's listed right here. 00:22:43.020 --> 00:22:45.900 And so here is it just doing that same example 00:22:45.900 --> 00:22:47.810 for a particular Piper Warrior. 00:22:47.810 --> 00:22:51.410 So they have the basic empty weight of the aircraft. 00:22:51.410 --> 00:22:54.660 Just as a hint, if it's something round like 1,500, 00:22:54.660 --> 00:22:57.470 then you probably didn't get the exact accurate amount. 00:22:57.470 --> 00:23:00.320 So again, if you look at the real thing, 00:23:00.320 --> 00:23:06.160 you're getting it down to some very specific accurate numbers. 00:23:06.160 --> 00:23:10.060 So 1,196.63. 00:23:10.060 --> 00:23:11.530 That means you got a real number. 00:23:14.240 --> 00:23:16.690 Here's our Piper Warrior. 00:23:16.690 --> 00:23:20.500 And so they have the basic empty weight, the passengers 00:23:20.500 --> 00:23:22.530 in the front and the rear. 00:23:22.530 --> 00:23:25.060 They don't have any bags here right now, 00:23:25.060 --> 00:23:29.230 and they basically multiplied the weight times the arm. 00:23:29.230 --> 00:23:31.930 The arm is really indicated in the book 00:23:31.930 --> 00:23:34.510 and in these calculators as to where 00:23:34.510 --> 00:23:36.520 the location is of the chair. 00:23:36.520 --> 00:23:38.700 Now, of course, the seats slide forward and back, 00:23:38.700 --> 00:23:40.950 but they usually don't-- they don't get into that many 00:23:40.950 --> 00:23:44.320 specifics, and then you can calculate here the moment. 00:23:44.320 --> 00:23:46.660 So next, we do the ramp condition. 00:23:46.660 --> 00:23:49.150 So ramp condition is basically, what's 00:23:49.150 --> 00:23:51.490 the weight and loading of your airplane 00:23:51.490 --> 00:23:53.770 once it's fueled up and sitting on the ramp? 00:23:53.770 --> 00:23:55.600 Then you, in this case, they took off 00:23:55.600 --> 00:23:58.690 seven pounds for that taxi, and run up 00:23:58.690 --> 00:24:01.900 and then you're takeoff condition, in this case, 00:24:01.900 --> 00:24:10.420 is 2,440 pounds, and it has a moment here as calculated. 00:24:10.420 --> 00:24:12.970 So you basically do the same thing we just showed. 00:24:12.970 --> 00:24:15.760 So you you look at the weight on the left, 00:24:15.760 --> 00:24:18.370 and the CG location as the vertical line, 00:24:18.370 --> 00:24:20.590 and you see where those two lines intersect 00:24:20.590 --> 00:24:23.681 and you see whether or not it's inside the envelope. 00:24:26.390 --> 00:24:28.640 You can also check the landing condition. 00:24:28.640 --> 00:24:33.450 In general, you will have burned fuel during your flight, 00:24:33.450 --> 00:24:36.290 and so your landing condition will be lower, 00:24:36.290 --> 00:24:39.380 but you might have heard big jets, 00:24:39.380 --> 00:24:43.100 and you've heard that sometimes they have to do a fuel dump. 00:24:43.100 --> 00:24:44.840 Why did they have to do a fuel dump? 00:24:44.840 --> 00:24:47.660 Well, maybe they calculated their landing 00:24:47.660 --> 00:24:49.382 based on having flown across the country, 00:24:49.382 --> 00:24:50.840 but their flight across the country 00:24:50.840 --> 00:24:52.820 was canceled because of weather or whatever, 00:24:52.820 --> 00:24:55.787 and so they had to dump their fuel in order to land, 00:24:55.787 --> 00:24:58.370 which you don't like to hear is once they've dumped their fuel 00:24:58.370 --> 00:25:00.500 then you have another delay in the air, and you're like, hey, 00:25:00.500 --> 00:25:01.083 what happened? 00:25:01.083 --> 00:25:03.560 I thought we dumped all of our fuel. 00:25:03.560 --> 00:25:06.020 But of course, as a small little airplane, 00:25:06.020 --> 00:25:08.060 dumping fuel is not really a procedure 00:25:08.060 --> 00:25:11.030 you're going to be doing, so it might be a good idea 00:25:11.030 --> 00:25:14.750 to just calculate the landing and the runway lengths 00:25:14.750 --> 00:25:19.220 with the full fuel in case you have to make it landing right 00:25:19.220 --> 00:25:22.010 then and there before you've flown all the distance you 00:25:22.010 --> 00:25:25.300 thought you were going to get to fly. 00:25:25.300 --> 00:25:30.710 So in general, as you can see that where we were beforehand 00:25:30.710 --> 00:25:32.620 was higher and the weight goes down, 00:25:32.620 --> 00:25:34.940 so your landing condition is almost always 00:25:34.940 --> 00:25:37.710 going to stay within the envelope. 00:25:37.710 --> 00:25:40.450 There's some places, where if you're CG 00:25:40.450 --> 00:25:42.830 is too far aft or too far forward, 00:25:42.830 --> 00:25:44.930 where actually that reduction in weight 00:25:44.930 --> 00:25:47.171 could cause you to come outside the envelope. 00:25:49.820 --> 00:25:52.530 All right, so there are also a lot of spreadsheets available. 00:25:52.530 --> 00:25:55.410 You can make your own spreadsheet pretty quickly 00:25:55.410 --> 00:25:58.920 in Excel using the data from the particular aircraft 00:25:58.920 --> 00:26:00.420 that you're renting or buying. 00:26:03.780 --> 00:26:07.220 All right, and these are just some snapshots 00:26:07.220 --> 00:26:09.020 from the book that we just looked at 00:26:09.020 --> 00:26:11.540 and the show pictures of where the seats are 00:26:11.540 --> 00:26:15.350 in the airplane in order for you to calculate that. 00:26:15.350 --> 00:26:19.910 You could also calculate the moment left to right. 00:26:19.910 --> 00:26:21.800 It's pretty easy to think about, though, 00:26:21.800 --> 00:26:23.750 that in that tiny little airplane, 00:26:23.750 --> 00:26:26.287 if you're sitting on the front in the left and no one's 00:26:26.287 --> 00:26:28.370 sitting on your right and you have someone sitting 00:26:28.370 --> 00:26:31.610 in the back on the left, then you're going to be tilted over. 00:26:31.610 --> 00:26:33.370 It's very easy to fix that problem, 00:26:33.370 --> 00:26:36.680 just make sure you have someone sitting on the other side. 00:26:36.680 --> 00:26:39.540 I have noticed some of these effects before. 00:26:39.540 --> 00:26:42.080 I'm a little bit of a smaller person, 00:26:42.080 --> 00:26:45.140 and there was a very, very large instructor sitting next to me, 00:26:45.140 --> 00:26:47.750 and I actually could tell as I was flying that it 00:26:47.750 --> 00:26:49.370 was a little bit tilted. 00:26:49.370 --> 00:26:52.100 And so with the future flights, we put some more bags 00:26:52.100 --> 00:26:55.250 on my side, and it was a little bit more evened out. 00:26:55.250 --> 00:26:58.130 Usually, you won't run into that too much as an issue. 00:26:58.130 --> 00:27:02.570 In some of the small puddle jumper aircraft and so 00:27:02.570 --> 00:27:06.650 a commercial aircraft, they have sometimes a situation 00:27:06.650 --> 00:27:10.322 where there's only one row of seats on one side 00:27:10.322 --> 00:27:11.780 and then there's the aisle and then 00:27:11.780 --> 00:27:13.407 two seats on the other side. 00:27:13.407 --> 00:27:14.990 Have you guys seen that configuration? 00:27:14.990 --> 00:27:16.710 I'm getting a lot of head nods. 00:27:16.710 --> 00:27:20.270 So in that situation, they might enforce 00:27:20.270 --> 00:27:22.940 that you have to sit in the seat that was assigned to you. 00:27:22.940 --> 00:27:26.420 And when people try to move from the side that 00:27:26.420 --> 00:27:28.787 only had one seat in the row to the side that 00:27:28.787 --> 00:27:31.370 has two seats because they just want more space to spread out, 00:27:31.370 --> 00:27:33.537 they might say, hey, for weight and balance reasons, 00:27:33.537 --> 00:27:37.040 you have to sit in the seat that was assigned for takeoff 00:27:37.040 --> 00:27:40.290 and so that's what they're talking about. 00:27:40.290 --> 00:27:42.480 There any questions about weight and balance? 00:27:51.230 --> 00:27:53.280 Do you guys think you could do weight and balance 00:27:53.280 --> 00:27:54.580 calculations? 00:27:54.580 --> 00:27:55.080 Yes? 00:27:55.080 --> 00:27:57.540 OK, I'm getting a lot of head nods, so everyone took physics. 00:27:57.540 --> 00:27:58.040 That's good. 00:27:58.040 --> 00:27:58.620 Good job. 00:27:58.620 --> 00:27:59.120 Yes? 00:27:59.120 --> 00:28:03.129 AUDIENCE: So I assume that [INAUDIBLE] the helicopter has 00:28:03.129 --> 00:28:05.524 lateral elements in the chart. 00:28:05.524 --> 00:28:08.400 [INAUDIBLE] 00:28:08.400 --> 00:28:10.230 TINA SRIVASTAVA: Helicopter question. 00:28:10.230 --> 00:28:13.320 I will actually defer to Philip, who flies helicopters 00:28:13.320 --> 00:28:14.410 quite frequently. 00:28:14.410 --> 00:28:18.300 So once he's back, we'll ask him about helicopter CG limits. 00:28:18.300 --> 00:28:20.610 Good question. 00:28:20.610 --> 00:28:23.074 Anything else? 00:28:23.074 --> 00:28:24.026 Yes? 00:28:24.026 --> 00:28:32.730 AUDIENCE: [INAUDIBLE] 00:28:32.730 --> 00:28:35.030 TINA SRIVASTAVA: So the question is, 00:28:35.030 --> 00:28:36.710 when you're actually flying, do you 00:28:36.710 --> 00:28:38.603 do this calculation every single time, 00:28:38.603 --> 00:28:40.520 or do you mostly only do it when you're really 00:28:40.520 --> 00:28:41.690 loading the aircraft? 00:28:41.690 --> 00:28:43.790 So it's actually required that you have 00:28:43.790 --> 00:28:45.662 the weight and balance done. 00:28:45.662 --> 00:28:47.870 The reason you don't do it every single time, though, 00:28:47.870 --> 00:28:50.340 is you frequently fly in the same configuration. 00:28:50.340 --> 00:28:52.550 So if you rent from a flight school, 00:28:52.550 --> 00:28:55.940 you might frequently rent you know a couple aircraft, 00:28:55.940 --> 00:28:59.960 and you might frequently fly just yourself, 00:28:59.960 --> 00:29:02.570 doing a solo flight, or fly with your instructor. 00:29:02.570 --> 00:29:05.150 So you might just keep it stored that you 00:29:05.150 --> 00:29:08.240 have a couple of pieces of paper in your flight bag 00:29:08.240 --> 00:29:11.000 that are the weight and balance calculations for what you 00:29:11.000 --> 00:29:13.520 almost always fly and is almost always 00:29:13.520 --> 00:29:16.580 within the normal category envelope. 00:29:16.580 --> 00:29:19.670 But you definitely want to do those calculations 00:29:19.670 --> 00:29:22.460 if you're getting passengers in the back seat. 00:29:22.460 --> 00:29:24.890 Whenever we go on these MIT fly outs, 00:29:24.890 --> 00:29:28.080 we actually ask people for their weights, 00:29:28.080 --> 00:29:31.070 and it's actually a big restriction too. 00:29:31.070 --> 00:29:33.443 So when we're trying to get passengers to sit down, 00:29:33.443 --> 00:29:35.360 just because I fly assessment with four seats, 00:29:35.360 --> 00:29:38.980 as we just saw from the example, I don't have four pass-- 00:29:38.980 --> 00:29:40.810 I don't have three passengers to offer. 00:29:40.810 --> 00:29:44.690 I often say, I have 220 pounds available, 00:29:44.690 --> 00:29:49.160 and so they then have to sort out, Sebastian and his team, 00:29:49.160 --> 00:29:52.963 as to who to assign to my plane versus another plane. 00:29:52.963 --> 00:29:54.380 And also, if people aren't being-- 00:29:54.380 --> 00:29:56.743 if you notice people aren't being overly forthcoming 00:29:56.743 --> 00:29:58.160 about their weight, you might want 00:29:58.160 --> 00:30:00.440 to increase the amount that they gave you. 00:30:00.440 --> 00:30:02.870 PHILIP GREENSPUN: Yeah, let me add that-- 00:30:02.870 --> 00:30:05.180 obviously, have a lot more experience 00:30:05.180 --> 00:30:12.222 being over overweight than Tina might have, but also-- 00:30:12.222 --> 00:30:13.930 actually, these pants are a good example. 00:30:13.930 --> 00:30:17.060 20 years ago, some friends and I, 00:30:17.060 --> 00:30:20.120 we made a web front end to a Levi Strauss factory that 00:30:20.120 --> 00:30:22.130 could make custom cut khakis. 00:30:22.130 --> 00:30:23.660 So we asked people in the web form 00:30:23.660 --> 00:30:25.820 when they ordered what's your waist size, what's 00:30:25.820 --> 00:30:28.520 your inseam, what's your height and weight. 00:30:28.520 --> 00:30:32.000 And from that, we had software to try 00:30:32.000 --> 00:30:35.287 to infer their actual weight, their actual waist size, 00:30:35.287 --> 00:30:37.370 and then we make them-- you can't really see this, 00:30:37.370 --> 00:30:39.790 but these pants just say pair number 7. 00:30:39.790 --> 00:30:42.490 They don't say anything about what size it actually is. 00:30:42.490 --> 00:30:43.820 They would get their pants-- 00:30:43.820 --> 00:30:45.660 this was in 1997. 00:30:45.660 --> 00:30:47.720 They would get their pants, if they didn't fit, 00:30:47.720 --> 00:30:50.303 they'd say, look, it needs to be a little looser in the waist. 00:30:50.303 --> 00:30:52.370 It needs to be a little shorter, and then 00:30:52.370 --> 00:30:55.520 a revised pair would be made and sent to them, 00:30:55.520 --> 00:30:58.130 but we never relied on their stated weight 00:30:58.130 --> 00:31:00.872 or their stated waist size, exactly. 00:31:00.872 --> 00:31:03.080 TINA SRIVASTAVA: Philip, there was a question for you 00:31:03.080 --> 00:31:06.950 that I wasn't able to answer about helicopter CGs, 00:31:06.950 --> 00:31:09.210 and really thinking it was the lateral CG. 00:31:09.210 --> 00:31:10.710 What was your question specifically? 00:31:10.710 --> 00:31:13.230 AUDIENCE: [INAUDIBLE] 00:31:13.230 --> 00:31:16.250 PHILIP GREENSPUN: It's very hard to get a-- the question is 00:31:16.250 --> 00:31:19.240 it's very hard to get a helicopter out of lateral CG, 00:31:19.240 --> 00:31:20.230 as with an aircraft. 00:31:20.230 --> 00:31:23.350 If you have to have you people in the back and a light person 00:31:23.350 --> 00:31:29.700 in the front, it's easy to get out of front back CG, 00:31:29.700 --> 00:31:32.160 longitudinal CG, but-- 00:31:32.160 --> 00:31:34.660 TINA SRIVASTAVA: He's talking about, what we just discussed, 00:31:34.660 --> 00:31:36.493 it's frequently the case that you might have 00:31:36.493 --> 00:31:39.490 a forward CG or an aft CG, but you don't usually 00:31:39.490 --> 00:31:43.810 have an issue with the CG on the left or the right, unless-- 00:31:43.810 --> 00:31:47.090 it's very visible in a four seat aircraft 00:31:47.090 --> 00:31:48.548 how to fix those types of problems. 00:31:48.548 --> 00:31:50.423 PHILIP GREENSPUN: One issue with the Robinson 00:31:50.423 --> 00:31:52.510 is they put the main fuel tank on the left, 00:31:52.510 --> 00:31:53.970 so they're budgeting for-- 00:31:53.970 --> 00:31:57.490 in a solo situation, a pilot of at least a certain minimum 00:31:57.490 --> 00:31:59.440 weight in the front right. 00:31:59.440 --> 00:32:02.320 So very lightweight, sometimes when 00:32:02.320 --> 00:32:04.630 teenagers are learning to fly helicopters, 00:32:04.630 --> 00:32:06.790 they have to add a little bit of ballast, 00:32:06.790 --> 00:32:10.240 let's say like a big heavy gym weight. 00:32:10.240 --> 00:32:13.810 A 50 pound gym weight in the front 00:32:13.810 --> 00:32:15.790 left footwell or something. 00:32:15.790 --> 00:32:18.640 AUDIENCE: The other thing that could go wrong is-- 00:32:18.640 --> 00:32:21.850 so when you do your pre-flight, one of the things that you do 00:32:21.850 --> 00:32:24.890 is that if you're sitting in the pilot's seat, so 00:32:24.890 --> 00:32:27.040 on the left side, so to your right 00:32:27.040 --> 00:32:28.810 in the middle at the bottom, there's 00:32:28.810 --> 00:32:31.300 a little knob where you can say whether you want 00:32:31.300 --> 00:32:34.990 the fuel to be coming from the left tank, the right tank, 00:32:34.990 --> 00:32:35.860 or both. 00:32:35.860 --> 00:32:38.830 And pretty much, all the time, the checklist 00:32:38.830 --> 00:32:40.663 says that after you've parked the plane, 00:32:40.663 --> 00:32:42.580 you want to twist it to the left or the right, 00:32:42.580 --> 00:32:44.110 and the reason is you don't want-- 00:32:44.110 --> 00:32:45.850 while it's sitting there, fuel to be 00:32:45.850 --> 00:32:49.960 sloshing across the plane, and so you set it to left, 00:32:49.960 --> 00:32:51.020 for example. 00:32:51.020 --> 00:32:53.590 Now, if you skipped that step, even though it comes up 00:32:53.590 --> 00:32:56.020 several times throughout your pre-flight 00:32:56.020 --> 00:33:00.160 and then your run up check, if you didn't put the fuel 00:33:00.160 --> 00:33:03.430 to draw from both tanks and it's only drawing from one tank, 00:33:03.430 --> 00:33:07.598 then you might experience that instability. 00:33:07.598 --> 00:33:09.390 PHILIP GREENSPUN: All right, why don't we-- 00:33:09.390 --> 00:33:12.280 should we take a 15-minute break so people can run out, 00:33:12.280 --> 00:33:14.890 grab food, bring it back, and then we'll hear from 00:33:14.890 --> 00:33:16.150 [INAUDIBLE] about-- 00:33:16.150 --> 00:33:19.870 TINA SRIVASTAVA: The test pilot and life potentially outside 00:33:19.870 --> 00:33:21.570 of the limits.