1 00:00:10,948 --> 00:00:12,490 PHILIP GREENSPUN: Quick introduction. 2 00:00:12,490 --> 00:00:16,250 I know hardly anybody says they care about helicopters. 3 00:00:16,250 --> 00:00:19,830 But as God is my witness, I'm going to change that. 4 00:00:19,830 --> 00:00:25,210 If I can reach one of you airplane obsessed folks, 5 00:00:25,210 --> 00:00:26,120 I will do my best. 6 00:00:28,630 --> 00:00:33,110 So what is cool about a helicopter? 7 00:00:33,110 --> 00:00:35,320 Here, it's the view. 8 00:00:35,320 --> 00:00:37,320 So let's start, first and foremost, it's a view. 9 00:00:37,320 --> 00:00:40,430 So these are some pictures that I 10 00:00:40,430 --> 00:00:43,490 snapped on a trip from the Robinson factory 11 00:00:43,490 --> 00:00:46,330 in Los Angeles back to Boston. 12 00:00:49,817 --> 00:00:51,400 Who recognizes the city in the middle? 13 00:00:53,980 --> 00:00:56,320 Ooh, some Midwesterners here, Chicago indeed. 14 00:01:02,311 --> 00:01:04,769 Of course this is the Stata Center where we'll be tomorrow, 15 00:01:04,769 --> 00:01:10,330 remember that, 32 141. 16 00:01:10,330 --> 00:01:14,160 What are the parts of the helicopter? 17 00:01:14,160 --> 00:01:17,490 If you're between ages 3 and 5, it's 18 00:01:17,490 --> 00:01:21,540 acceptable to call it the thing on the top the propeller 19 00:01:21,540 --> 00:01:26,220 but older than that, it's better to say main rotor system. 20 00:01:26,220 --> 00:01:27,840 Tail rotor is in the back-- we'll 21 00:01:27,840 --> 00:01:30,790 talk about why we need that in a minute. 22 00:01:30,790 --> 00:01:33,540 You got to have transmissions. 23 00:01:33,540 --> 00:01:35,190 In helicopters, the speed of the engine 24 00:01:35,190 --> 00:01:38,190 is never the speed that you want, I don't think. 25 00:01:38,190 --> 00:01:40,290 And landing gear is kind of nice. 26 00:01:40,290 --> 00:01:42,180 Although for record-setting flights, 27 00:01:42,180 --> 00:01:44,250 sometimes people have taken them off 28 00:01:44,250 --> 00:01:46,230 to try to get a little higher a little faster, 29 00:01:46,230 --> 00:01:47,730 and then they just land very gently. 30 00:01:50,790 --> 00:01:54,250 So your typical helicopter drive train 31 00:01:54,250 --> 00:01:58,938 will have transmissions for both the main rotor, 32 00:01:58,938 --> 00:02:00,480 and they'll have another transmission 33 00:02:00,480 --> 00:02:03,900 to adjust the speed of the tail, maybe gear it back up 34 00:02:03,900 --> 00:02:06,000 a little bit. 35 00:02:06,000 --> 00:02:08,000 This unfortunately does introduce another source 36 00:02:08,000 --> 00:02:09,500 of unreliability. 37 00:02:09,500 --> 00:02:12,560 So in the airplane, you've got your engine, 38 00:02:12,560 --> 00:02:13,970 it's bolted to the propeller. 39 00:02:13,970 --> 00:02:17,620 As long as the engine's turning, it's hard to have a problem. 40 00:02:17,620 --> 00:02:20,365 The propellers don't generally just come apart in flight. 41 00:02:20,365 --> 00:02:21,740 But here with the helicopter, you 42 00:02:21,740 --> 00:02:23,365 might have a working engine and working 43 00:02:23,365 --> 00:02:26,240 main rotor and the transmission, all the oil might come out 44 00:02:26,240 --> 00:02:28,522 and the gears seize up. 45 00:02:28,522 --> 00:02:30,980 There's a couple of warning lights in there for when you're 46 00:02:30,980 --> 00:02:32,230 having a transmission problem. 47 00:02:35,740 --> 00:02:38,800 This is the rubber belt system that's 48 00:02:38,800 --> 00:02:41,290 used in some piston helicopters. 49 00:02:41,290 --> 00:02:44,320 I think this is probably a drawing off of a Robinson. 50 00:02:44,320 --> 00:02:48,490 But basically, you have pulleys on the engine side 51 00:02:48,490 --> 00:02:51,550 and on the drive change side, and you have these rubber belts 52 00:02:51,550 --> 00:02:52,270 connecting them. 53 00:02:52,270 --> 00:02:54,615 So you can start your engine with the belts loose 54 00:02:54,615 --> 00:02:55,990 and then tighten them up when you 55 00:02:55,990 --> 00:02:58,607 want the engine to begin driving the rotor system, 56 00:02:58,607 --> 00:03:00,940 that way you don't have to have the little starter motor 57 00:03:00,940 --> 00:03:03,550 actually turn all the rotors and stuff. 58 00:03:03,550 --> 00:03:05,120 How does it work? 59 00:03:05,120 --> 00:03:11,800 So Tina is a hard act to follow with my cave person computer 60 00:03:11,800 --> 00:03:14,350 programmers understanding of lift. 61 00:03:14,350 --> 00:03:21,520 But if you assume that the lift is a combination of Newton's 62 00:03:21,520 --> 00:03:26,200 third law and the Bernoulli principle, the sped up air 63 00:03:26,200 --> 00:03:28,720 has more kinetic energy, therefore 64 00:03:28,720 --> 00:03:30,160 for conservation of energy, it has 65 00:03:30,160 --> 00:03:31,780 to have less of something else, it's 66 00:03:31,780 --> 00:03:33,940 going to have lower static pressure. 67 00:03:33,940 --> 00:03:36,910 So here's one of the FAs diagrams here. 68 00:03:36,910 --> 00:03:39,160 We have velocity and pressure that are equal. 69 00:03:39,160 --> 00:03:40,370 They go into the Venturi. 70 00:03:40,370 --> 00:03:42,760 The velocity is higher, the pressure is lower, 71 00:03:42,760 --> 00:03:44,890 so the energy of the air is still the same. 72 00:03:44,890 --> 00:03:47,680 And it comes out again at the same velocity and pressure. 73 00:03:47,680 --> 00:03:51,700 So you're getting lift from the wing 74 00:03:51,700 --> 00:03:53,560 from both Newton's third law just 75 00:03:53,560 --> 00:03:56,080 pushing air down makes the wing go up 76 00:03:56,080 --> 00:04:00,380 and the Bernoulli principle of generating some low pressure. 77 00:04:00,380 --> 00:04:03,015 This is the same drawing you saw earlier of how 78 00:04:03,015 --> 00:04:05,140 when you exceed a certain critical angle of attack, 79 00:04:05,140 --> 00:04:08,650 depending on the air foil, your lift 80 00:04:08,650 --> 00:04:11,370 party comes to a quick end. 81 00:04:11,370 --> 00:04:14,470 It doesn't go away completely, but it's a sudden drop. 82 00:04:17,260 --> 00:04:20,910 Angle of attack, so remember there's your cord line, 83 00:04:20,910 --> 00:04:24,160 there's your relative wind, 4 degree angle of attack 84 00:04:24,160 --> 00:04:25,970 and a reasonable amount of forward speed. 85 00:04:25,970 --> 00:04:30,630 Remember the lift varies is the speed squared 86 00:04:30,630 --> 00:04:31,950 will have you going. 87 00:04:31,950 --> 00:04:34,890 And if you want to fly slowly, you just 88 00:04:34,890 --> 00:04:37,720 go to higher and higher angles of attack. 89 00:04:37,720 --> 00:04:43,500 So why not hover in your Cessna 172 90 00:04:43,500 --> 00:04:46,710 and save yourself the trouble of getting a helicopter rating? 91 00:04:46,710 --> 00:04:49,110 It's because you know off the right end 92 00:04:49,110 --> 00:04:52,560 of this chart you quickly get to the stalling angle of attack 93 00:04:52,560 --> 00:04:54,570 and the plane doesn't fly anymore. 94 00:04:54,570 --> 00:04:59,970 So there's an FA drawing I think from the pilots handbook 95 00:04:59,970 --> 00:05:03,210 where the airflow becomes turbulent somewhere between 12 96 00:05:03,210 --> 00:05:06,630 and 16 degrees angle of attack, depending on the air foil. 97 00:05:06,630 --> 00:05:09,000 And that's why the Cessna can't be 98 00:05:09,000 --> 00:05:11,790 used for hovering operations. 99 00:05:11,790 --> 00:05:16,760 What if you saw the wing off the Cessna and spin it around? 100 00:05:16,760 --> 00:05:18,910 So if you do that, the wing will always 101 00:05:18,910 --> 00:05:23,350 have airspeed even if the fuselage is not moving. 102 00:05:23,350 --> 00:05:27,550 And that was an idea that was first 103 00:05:27,550 --> 00:05:29,750 reduced to practice in 1907. 104 00:05:29,750 --> 00:05:33,160 So only four years after the Wright brothers flew, 105 00:05:33,160 --> 00:05:36,490 a couple of guys in France were actually 106 00:05:36,490 --> 00:05:38,350 hovering a little bit in the helicopter. 107 00:05:38,350 --> 00:05:42,280 The first helicopters that could be flown and controlled 108 00:05:42,280 --> 00:05:47,740 and actually operated as a practical aircraft I 109 00:05:47,740 --> 00:05:51,040 think mid 30s in Germany. 110 00:05:51,040 --> 00:05:55,690 And then Sikorsky is famous for being the first mass 111 00:05:55,690 --> 00:06:00,820 producer of helicopters with the Sikorsky R-4. 112 00:06:00,820 --> 00:06:04,120 It was used for a few computational purposes 113 00:06:04,120 --> 00:06:08,110 in World War II, search and rescue type stuff. 114 00:06:08,110 --> 00:06:10,960 But really, the Korean War was the first time 115 00:06:10,960 --> 00:06:14,470 that helicopters were widely used by the military. 116 00:06:14,470 --> 00:06:19,180 Let's talk about a very simple qualitative physics here. 117 00:06:22,540 --> 00:06:23,890 We're spending on the ramp. 118 00:06:23,890 --> 00:06:31,120 So we spin the rotor system up to 400 RPM. 119 00:06:31,120 --> 00:06:32,860 But we're still on the ramp. 120 00:06:32,860 --> 00:06:36,560 So does anybody have a brilliant idea 121 00:06:36,560 --> 00:06:39,870 for how do we get up into the air where we want to be? 122 00:06:39,870 --> 00:06:41,370 AUDIENCE: [INAUDIBLE] were negative, 123 00:06:41,370 --> 00:06:46,137 because there [INAUDIBLE] of the main rotor system. 124 00:06:46,137 --> 00:06:47,470 PHILIP GREENSPUN: OK, excellent. 125 00:06:47,470 --> 00:06:49,650 So-- what's your name? 126 00:06:49,650 --> 00:06:50,200 Sorry. 127 00:06:50,200 --> 00:06:50,950 AUDIENCE: Aziz. 128 00:06:50,950 --> 00:06:54,070 PHILIP GREENSPUN: Aziz has a correct observation 129 00:06:54,070 --> 00:06:58,060 that if you want to get the same lift out of a wing 130 00:06:58,060 --> 00:07:00,647 without changing the speed, we don't want to have this-- 131 00:07:00,647 --> 00:07:02,980 we don't want to speed up too much because the tips will 132 00:07:02,980 --> 00:07:06,070 go supersonic, and the neighbors will begin to complain. 133 00:07:06,070 --> 00:07:09,290 So we just twist the blades up a little bit. 134 00:07:09,290 --> 00:07:11,500 And as they're twisted up, they'll bite more air, 135 00:07:11,500 --> 00:07:13,780 generate more lift, and the helicopter 136 00:07:13,780 --> 00:07:16,190 will begin rising up. 137 00:07:16,190 --> 00:07:17,440 What will happen to the speed? 138 00:07:17,440 --> 00:07:21,700 Let's hear from one of these aeroengineering heroes. 139 00:07:21,700 --> 00:07:23,885 As we generate more lift, what happens? 140 00:07:23,885 --> 00:07:25,900 AUDIENCE: You now have more drag on the rotors, 141 00:07:25,900 --> 00:07:27,460 so the engine slows down. 142 00:07:27,460 --> 00:07:29,500 PHILIP GREENSPUN: More lift, more drag, 143 00:07:29,500 --> 00:07:34,222 so without adding more power, the engine-- 144 00:07:34,222 --> 00:07:36,680 well, without adding more power, the blades will slow down. 145 00:07:36,680 --> 00:07:39,640 So you want a correlator. 146 00:07:39,640 --> 00:07:43,030 As you're lifting the collective control on a helicopter, 147 00:07:43,030 --> 00:07:45,280 the correlator is opening the throttle 148 00:07:45,280 --> 00:07:48,043 and adding more power automatically. 149 00:07:48,043 --> 00:07:49,710 And there's also an electronic governors 150 00:07:49,710 --> 00:07:53,020 that will just touch that up a little bit by watching the RPM. 151 00:07:53,020 --> 00:07:55,690 Turbine helicopters all have governors. 152 00:07:55,690 --> 00:08:00,520 Most piston-- Robinsons have governors, as well. 153 00:08:00,520 --> 00:08:03,790 All right, so what if we're parked on ice? 154 00:08:03,790 --> 00:08:06,370 Has anybody here seen my favorite movie, 155 00:08:06,370 --> 00:08:09,950 Blades of Glory? 156 00:08:09,950 --> 00:08:11,703 So when Will Ferrell and his partner, 157 00:08:11,703 --> 00:08:13,870 what if they're on the ice and they push each other? 158 00:08:13,870 --> 00:08:14,412 What happens? 159 00:08:18,180 --> 00:08:22,760 Both go backwards, the pusher and the pushee. 160 00:08:22,760 --> 00:08:28,840 So keeping in mind Blades of Glory, an important physics 161 00:08:28,840 --> 00:08:31,330 work, what if we're parked on the ice? 162 00:08:31,330 --> 00:08:34,419 What happens to our helicopter after we start the engine 163 00:08:34,419 --> 00:08:35,700 and start the blades spinning? 164 00:08:39,420 --> 00:08:41,750 AUDIENCE: [INAUDIBLE] 165 00:08:41,750 --> 00:08:44,670 PHILIP GREENSPUN: Helicopter spins the other way, excellent. 166 00:08:44,670 --> 00:08:47,490 Yeah, so that's Newton's third law, once again. 167 00:08:47,490 --> 00:08:50,070 For every action, there's an equal and opposite reaction. 168 00:08:50,070 --> 00:08:52,650 You're not going to see that as dramatically if you're 169 00:08:52,650 --> 00:08:54,870 parked on pavement, because of the friction. 170 00:08:54,870 --> 00:08:57,240 So what do we do? 171 00:08:57,240 --> 00:08:59,080 We add the tail rotor. 172 00:08:59,080 --> 00:09:00,520 So here are the forces up here. 173 00:09:00,520 --> 00:09:02,200 There's the blade rotation. 174 00:09:02,200 --> 00:09:03,090 There's the torque. 175 00:09:03,090 --> 00:09:06,510 To counteract the torque, we've got the tail rotor thrust 176 00:09:06,510 --> 00:09:08,730 to blow the tail back into position. 177 00:09:08,730 --> 00:09:12,150 And the only thing here that's not corrected, you'll notice, 178 00:09:12,150 --> 00:09:14,100 is the tail rotor thrust. 179 00:09:14,100 --> 00:09:16,440 So if you set everything up the way 180 00:09:16,440 --> 00:09:19,710 you would think obvious, like put the rotor mast straight up 181 00:09:19,710 --> 00:09:22,230 and put the tail rotor on it, the whole helicopter 182 00:09:22,230 --> 00:09:26,100 with the controls neutral would drift to the right 183 00:09:26,100 --> 00:09:28,950 from the tail rotor thrust. 184 00:09:28,950 --> 00:09:30,510 Because it's pushing the tail. 185 00:09:30,510 --> 00:09:35,960 The helicopter wants to rotate that way. 186 00:09:35,960 --> 00:09:38,000 The tail rotor blows it back this way. 187 00:09:38,000 --> 00:09:41,000 And that would blow the whole machine 188 00:09:41,000 --> 00:09:43,640 off the side of the ramp if the pilot didn't 189 00:09:43,640 --> 00:09:47,570 hold a lot of left cyclic. 190 00:09:47,570 --> 00:09:50,180 So to counteract that, the helicopters 191 00:09:50,180 --> 00:09:52,820 are rigged with the mast at a slight left angle 192 00:09:52,820 --> 00:09:55,160 so that they don't have this tendency 193 00:09:55,160 --> 00:09:58,630 to go off to the right. 194 00:09:58,630 --> 00:10:01,270 AUDIENCE: [INAUDIBLE] question, what does the governor do? 195 00:10:01,270 --> 00:10:03,728 PHILIP GREENSPUN: The governor, yes, let me reinforce that. 196 00:10:03,728 --> 00:10:05,230 So yes, as you generate lift, you 197 00:10:05,230 --> 00:10:08,230 get more drag, which will cause the blades to slow down. 198 00:10:08,230 --> 00:10:10,480 So there's a mechanical correlation. 199 00:10:10,480 --> 00:10:13,670 As you're raising the collective, 200 00:10:13,670 --> 00:10:16,480 the throttle's being opened just kind of blindly. 201 00:10:16,480 --> 00:10:18,700 And the governor is touching that up. 202 00:10:18,700 --> 00:10:20,440 The governor is watching and maybe 203 00:10:20,440 --> 00:10:22,990 twisting the throttle control slightly 204 00:10:22,990 --> 00:10:25,720 to fine-tune the throttle to keep the blades exactly 205 00:10:25,720 --> 00:10:26,950 at 400 RPM. 206 00:10:26,950 --> 00:10:28,630 Let's say that's the [INAUDIBLE].. 207 00:10:28,630 --> 00:10:30,673 For a pilot, pilots are-- 208 00:10:30,673 --> 00:10:32,590 you don't want to distract the pilot too much, 209 00:10:32,590 --> 00:10:34,600 so the gauge is just calibrated in percent. 210 00:10:34,600 --> 00:10:35,920 It's 100% RPM. 211 00:10:35,920 --> 00:10:36,760 That's good. 212 00:10:36,760 --> 00:10:39,328 That's all you need to know about your helicopter. 213 00:10:39,328 --> 00:10:40,870 I think in the Robinson, it works out 214 00:10:40,870 --> 00:10:43,420 to pretty close to 400 RPM. 215 00:10:43,420 --> 00:10:47,020 All right, forward flight-- 216 00:10:47,020 --> 00:10:54,350 so we're hovering and we want to go forward. 217 00:10:54,350 --> 00:10:58,260 So it seems obvious that we want to tilt the fan. 218 00:10:58,260 --> 00:11:01,370 We want to push the fan down this way, 219 00:11:01,370 --> 00:11:05,990 and that way, we'll get some horizontal vector of thrust 220 00:11:05,990 --> 00:11:08,160 and we'll be going forward. 221 00:11:08,160 --> 00:11:13,640 But where do we push it from? 222 00:11:13,640 --> 00:11:16,990 It's a spinning gyro, so it has a lot of stability. 223 00:11:16,990 --> 00:11:20,800 If we're really strong and we reach up from our pilot seat 224 00:11:20,800 --> 00:11:22,930 and try to nudge the rotor system, 225 00:11:22,930 --> 00:11:26,350 why wouldn't that just cause the helicopter fuselage 226 00:11:26,350 --> 00:11:30,880 to move underneath the fixed rotor system, 227 00:11:30,880 --> 00:11:32,750 instead of moving the rotor system? 228 00:11:32,750 --> 00:11:36,850 There's nothing to fix unless we can call up an incredibly 229 00:11:36,850 --> 00:11:38,440 strong friend, and say, would you 230 00:11:38,440 --> 00:11:41,590 mind holding the helicopter in a fixed position? 231 00:11:41,590 --> 00:11:43,930 We don't have anything to push against in order 232 00:11:43,930 --> 00:11:45,100 to tilt the rotor. 233 00:11:45,100 --> 00:11:46,660 Does that make sense? 234 00:11:46,660 --> 00:11:49,420 You've got this gyro on top of you, and disturbing it 235 00:11:49,420 --> 00:11:51,490 is going to take a lot of power. 236 00:11:51,490 --> 00:11:53,500 And even if you had the strength, 237 00:11:53,500 --> 00:11:57,670 you don't have anywhere to stand rigidly and push. 238 00:11:57,670 --> 00:11:59,080 So what do you think? 239 00:11:59,080 --> 00:12:03,160 Could the rotor just fly itself into a new position? 240 00:12:03,160 --> 00:12:04,510 And how would that work? 241 00:12:04,510 --> 00:12:06,970 How could you use the spinning wing 242 00:12:06,970 --> 00:12:11,175 itself to fly itself into a new tilted-down position? 243 00:12:11,175 --> 00:12:12,550 Anybody have any brilliant ideas? 244 00:12:15,780 --> 00:12:17,830 AUDIENCE: You increase the angle of attack 245 00:12:17,830 --> 00:12:19,880 of the blades on one side [INAUDIBLE].. 246 00:12:19,880 --> 00:12:21,630 PHILIP GREENSPUN: What's your name, sorry? 247 00:12:21,630 --> 00:12:22,390 AUDIENCE: John. 248 00:12:22,390 --> 00:12:24,015 PHILIP GREENSPUN: John has a good idea. 249 00:12:24,015 --> 00:12:26,830 So John says, increase the angle of attack 250 00:12:26,830 --> 00:12:30,220 and decrease it as the blade moves around the disk. 251 00:12:30,220 --> 00:12:33,100 So if you can increase the lift on part of the disk 252 00:12:33,100 --> 00:12:35,020 compared to another part of the disk, 253 00:12:35,020 --> 00:12:36,730 it will naturally tilt itself. 254 00:12:36,730 --> 00:12:38,230 So if you want to go forward-- let's 255 00:12:38,230 --> 00:12:41,660 ignore gyroscopic procession for a moment, 256 00:12:41,660 --> 00:12:44,962 because I think we've proven that nobody understands it. 257 00:12:44,962 --> 00:12:47,170 Let's just say that we could make the angle of attack 258 00:12:47,170 --> 00:12:50,750 higher on the back of the disk compared to the front. 259 00:12:50,750 --> 00:12:52,840 Then the back of the disk would have more lift. 260 00:12:52,840 --> 00:12:56,890 It would rise up and the front would go lower, 261 00:12:56,890 --> 00:12:59,740 and then you would see this flight path that you do see. 262 00:12:59,740 --> 00:13:02,060 That make sense? 263 00:13:02,060 --> 00:13:05,140 So basically, you're basically flying the rotor system. 264 00:13:05,140 --> 00:13:07,113 You're not flying the helicopter. 265 00:13:07,113 --> 00:13:09,280 The helicopter's just hanging from the rotor system. 266 00:13:09,280 --> 00:13:12,040 That's a good mental model. 267 00:13:12,040 --> 00:13:17,260 And all of the power is from the engine to the rotor system. 268 00:13:17,260 --> 00:13:19,270 So that's a natural place to do it, just 269 00:13:19,270 --> 00:13:22,220 by tweaking the blade angle as it rotates around. 270 00:13:22,220 --> 00:13:26,080 So the left hand is collective, moving the blade's angle 271 00:13:26,080 --> 00:13:29,860 regardless of where they are on the disk, 272 00:13:29,860 --> 00:13:32,050 and the cyclic, which is changing the pitch 273 00:13:32,050 --> 00:13:35,090 cyclically as you suggested. 274 00:13:35,090 --> 00:13:36,850 All right, what's the magic? 275 00:13:36,850 --> 00:13:39,100 This design-- I'm not sure it's really 276 00:13:39,100 --> 00:13:41,230 changed at all since the very first helicopters. 277 00:13:41,230 --> 00:13:45,500 Maybe those brothers in Paris didn't have one in 1907, 278 00:13:45,500 --> 00:13:47,890 but I'm pretty sure that every helicopter since then 279 00:13:47,890 --> 00:13:48,910 has had this. 280 00:13:48,910 --> 00:13:50,070 There's a swashplate. 281 00:13:53,620 --> 00:13:59,660 Watch this-- so the lower part of the swashplate 282 00:13:59,660 --> 00:14:03,740 here is fixed and connected to the flight controls. 283 00:14:03,740 --> 00:14:06,290 And then there's a bearing, and the upper swashplate 284 00:14:06,290 --> 00:14:07,940 rotates with the blades. 285 00:14:07,940 --> 00:14:09,630 Does that make sense? 286 00:14:09,630 --> 00:14:12,000 So if you lift the lower swashplate up, 287 00:14:12,000 --> 00:14:14,310 that pushes the upper swashplate up, 288 00:14:14,310 --> 00:14:19,030 which pushes these rods that are connected 289 00:14:19,030 --> 00:14:20,590 to a corner of the blade. 290 00:14:20,590 --> 00:14:23,290 And that'll cause the blades to tilt. That make sense? 291 00:14:23,290 --> 00:14:24,790 So you have this rotating swashplate 292 00:14:24,790 --> 00:14:27,880 that's connected to a corner of the blade. 293 00:14:27,880 --> 00:14:29,860 And if you push the whole thing up 294 00:14:29,860 --> 00:14:32,590 by yanking up on the collective, then you 295 00:14:32,590 --> 00:14:34,150 can see the blades actually twist. 296 00:14:34,150 --> 00:14:37,390 You can do that in the hangar and see the effect of this. 297 00:14:37,390 --> 00:14:42,580 At the same time, in your right hand is the cyclic. 298 00:14:42,580 --> 00:14:46,360 And with the cyclic, you're tilting the swashplate. 299 00:14:46,360 --> 00:14:48,730 So with the tilted swashplate, that 300 00:14:48,730 --> 00:14:54,700 will just cause the blades to twist up 301 00:14:54,700 --> 00:14:57,110 and twist down as they rotate. 302 00:14:57,110 --> 00:14:59,980 So it's a pretty elegant solution. 303 00:14:59,980 --> 00:15:03,110 This is not carrying much of the load of the helicopter. 304 00:15:03,110 --> 00:15:05,110 There's still a mast holding the whole thing up. 305 00:15:05,110 --> 00:15:08,500 This really just has to carry enough force 306 00:15:08,500 --> 00:15:11,763 to twist the blades up and down, up and down, up and down. 307 00:15:11,763 --> 00:15:13,180 So that's your engineering design. 308 00:15:17,650 --> 00:15:21,180 Everybody appreciates that? 309 00:15:21,180 --> 00:15:24,750 Do we want to take off straight up like in a Hollywood movie? 310 00:15:24,750 --> 00:15:28,410 Well, if you have one or two people in a helicopter designed 311 00:15:28,410 --> 00:15:32,310 for four or five, you actually do 312 00:15:32,310 --> 00:15:34,690 have enough power to do that. 313 00:15:34,690 --> 00:15:37,140 However, there is something over here 314 00:15:37,140 --> 00:15:40,160 on the right called the "height velocity diagram." 315 00:15:40,160 --> 00:15:43,800 And you can see it says, "avoid operation in shaded areas." 316 00:15:43,800 --> 00:15:48,780 So they're saying-- we'll talk about this maybe a little 317 00:15:48,780 --> 00:15:50,940 later if people are interested. 318 00:15:54,090 --> 00:16:01,640 But if you are, let's say, up at 200 feet at zero airspeed, 319 00:16:01,640 --> 00:16:05,480 so you're just parked, hovering 200 feet above the ground, 320 00:16:05,480 --> 00:16:11,960 you don't have huge stores of forward speed, which 321 00:16:11,960 --> 00:16:14,660 is kinetic energy, or potential energy, 322 00:16:14,660 --> 00:16:16,400 because you're only up 200 feet. 323 00:16:16,400 --> 00:16:19,790 So it's going to be hard to do an auto-rotation that's 324 00:16:19,790 --> 00:16:22,550 perfect and doesn't bend anything, especially 325 00:16:22,550 --> 00:16:25,190 because the FAA says, if you're up high like that 326 00:16:25,190 --> 00:16:27,580 and the engine quits, in test pilot, 327 00:16:27,580 --> 00:16:31,640 you have to sit there with your arms folded for one second 328 00:16:31,640 --> 00:16:34,040 and do nothing, because that's what would probably 329 00:16:34,040 --> 00:16:35,210 happen in real life. 330 00:16:35,210 --> 00:16:36,950 You'd be surprised. 331 00:16:36,950 --> 00:16:40,130 People can do auto-rotations from 200 feet 332 00:16:40,130 --> 00:16:42,343 and land perfectly, but they know it's coming. 333 00:16:42,343 --> 00:16:43,760 They chop the throttle themselves. 334 00:16:43,760 --> 00:16:45,630 They immediately put the collective down 335 00:16:45,630 --> 00:16:46,880 and they do the auto-rotation. 336 00:16:46,880 --> 00:16:50,180 So but basically, if you're a pilot of average skill 337 00:16:50,180 --> 00:16:52,490 and you don't do anything for about a second 338 00:16:52,490 --> 00:16:55,130 after the engine quits, then this 339 00:16:55,130 --> 00:16:57,440 is supposed to keep you safe, by you either 340 00:16:57,440 --> 00:17:03,650 fly 50 knots or faster, or you fly 400 feet or higher at sea 341 00:17:03,650 --> 00:17:07,351 level, and higher than that at high altitude. 342 00:17:10,170 --> 00:17:12,690 So what we're actually recommended to do-- 343 00:17:12,690 --> 00:17:14,660 see this recommended takeoff profile-- 344 00:17:14,660 --> 00:17:18,083 is skim along the ground until we get up to about 45 knots 345 00:17:18,083 --> 00:17:19,500 and then let the helicopter climb. 346 00:17:19,500 --> 00:17:22,670 I think this is the curve for a Robinson R44. 347 00:17:22,670 --> 00:17:25,520 Why would you want to do that, aside from safety? 348 00:17:25,520 --> 00:17:27,740 Another good reason to do that is you 349 00:17:27,740 --> 00:17:32,490 watch these drag versus speed curves, 350 00:17:32,490 --> 00:17:35,310 and you see that you reach kind of a minimum. 351 00:17:35,310 --> 00:17:38,280 This is some generic helicopter from an FAA book. 352 00:17:38,280 --> 00:17:40,680 It's actually 55 knots for the Robinson. 353 00:17:40,680 --> 00:17:43,440 But if you can go 55 knots, you need less energy 354 00:17:43,440 --> 00:17:45,580 than any other airspeed. 355 00:17:45,580 --> 00:17:48,100 So the idea for a takeoff is you nudge the helicopter 356 00:17:48,100 --> 00:17:49,750 forward a little bit. 357 00:17:49,750 --> 00:17:52,600 If you can build up two knots of speed, 358 00:17:52,600 --> 00:17:54,520 that gives you excess power. 359 00:17:54,520 --> 00:17:57,652 You can use that excess power to climb up three inches 360 00:17:57,652 --> 00:17:59,860 or you can use that excess power to accelerate, maybe 361 00:17:59,860 --> 00:18:01,450 to three or four knots. 362 00:18:01,450 --> 00:18:03,160 And if you just keep accelerating 363 00:18:03,160 --> 00:18:04,750 using your extra power to accelerate, 364 00:18:04,750 --> 00:18:06,730 the faster you go, the less power you need. 365 00:18:06,730 --> 00:18:08,800 So even if you've never touched the collective 366 00:18:08,800 --> 00:18:10,780 or drawn any more horsepower, as long 367 00:18:10,780 --> 00:18:12,660 as you have an open area in front of you, 368 00:18:12,660 --> 00:18:13,870 you will accelerate. 369 00:18:13,870 --> 00:18:18,220 And once you hit 45 or 55 knots, your hover power 370 00:18:18,220 --> 00:18:19,840 turns into significant excess power 371 00:18:19,840 --> 00:18:21,980 that you can use for a climb. 372 00:18:21,980 --> 00:18:24,610 So that's why you often see helicopters 373 00:18:24,610 --> 00:18:29,870 at airports taking off kind of like a short-field airplane, 374 00:18:29,870 --> 00:18:33,220 and also landing a bit like a short-field airplane. 375 00:18:33,220 --> 00:18:36,860 Straight and level, it's very similar to an airplane. 376 00:18:36,860 --> 00:18:39,830 The performance is all a function of the attitude 377 00:18:39,830 --> 00:18:41,450 that the aircraft is in. 378 00:18:41,450 --> 00:18:47,030 Is it pitched up or down and how much power is being applied? 379 00:18:47,030 --> 00:18:50,120 And that's an indirect function of the collective position. 380 00:18:50,120 --> 00:18:54,170 So as with an airplane, remember, 381 00:18:54,170 --> 00:18:56,300 your pitch controls your speed. 382 00:18:56,300 --> 00:18:57,800 And the amount of power-- 383 00:18:57,800 --> 00:19:00,690 throttle in the airplane, collective in the helicopter-- 384 00:19:00,690 --> 00:19:02,690 determines whether you're climbing or descending 385 00:19:02,690 --> 00:19:04,490 at that air speed. 386 00:19:04,490 --> 00:19:08,630 Your attitude indicator in a VFR helicopter is the horizon, 387 00:19:08,630 --> 00:19:10,970 so you're watching the horizon carefully. 388 00:19:10,970 --> 00:19:14,138 The reason why people who are instrument-rated airplane 389 00:19:14,138 --> 00:19:15,680 pilots, they jump into the helicopter 390 00:19:15,680 --> 00:19:18,830 and they can fly it immediately, and people who've never flown 391 00:19:18,830 --> 00:19:19,680 have a tough time. 392 00:19:19,680 --> 00:19:21,325 It takes them 10 hours. 393 00:19:21,325 --> 00:19:22,700 And the reason is that people who 394 00:19:22,700 --> 00:19:24,620 are instrument-rated airplane pilots, 395 00:19:24,620 --> 00:19:26,360 they become very sensitive to watching 396 00:19:26,360 --> 00:19:31,510 for small changes in attitude. 397 00:19:31,510 --> 00:19:36,610 The anti-torque pedals-- remember, 398 00:19:36,610 --> 00:19:38,410 we had that tail rotor, and we adjust it 399 00:19:38,410 --> 00:19:42,820 so that the tail doesn't spin around on the ground. 400 00:19:42,820 --> 00:19:45,835 In the air, we adjust it so that the helicopter 401 00:19:45,835 --> 00:19:48,460 is streamlined into the wind. 402 00:19:48,460 --> 00:19:52,530 We don't actually have to use them to make turns. 403 00:19:52,530 --> 00:19:55,500 There's no adverse yaw as in some airplanes, 404 00:19:55,500 --> 00:19:58,350 where it'll start skidding or-- 405 00:19:58,350 --> 00:20:01,770 there's none of that, or slipping. 406 00:20:01,770 --> 00:20:04,890 All we do to make a turn is we put the helicopter, 407 00:20:04,890 --> 00:20:07,590 using the cyclic, into a little bit of a bank. 408 00:20:07,590 --> 00:20:08,610 And then we wait. 409 00:20:08,610 --> 00:20:12,020 So if we have, let's say, a 10-degree bank, 410 00:20:12,020 --> 00:20:20,570 the helicopter in one minute will make a 180-degree turn. 411 00:20:20,570 --> 00:20:24,630 Landing with power-- so again, like an airplane, 412 00:20:24,630 --> 00:20:27,050 if you see the spot in the ground, 413 00:20:27,050 --> 00:20:29,960 you adjust the power so you don't overfly the spot 414 00:20:29,960 --> 00:20:30,920 or underfly the spot. 415 00:20:30,920 --> 00:20:32,780 If the spot's rising up in the windshield 416 00:20:32,780 --> 00:20:34,910 from your perspective, that means 417 00:20:34,910 --> 00:20:37,130 you're going to land short, so you add power, 418 00:20:37,130 --> 00:20:39,230 raise collective in the helicopter. 419 00:20:39,230 --> 00:20:44,090 If the spot is descending, then you're overflying the spot, 420 00:20:44,090 --> 00:20:45,680 so you have to reduce power. 421 00:20:45,680 --> 00:20:51,500 It's a purely visual maneuver, except when 422 00:20:51,500 --> 00:20:53,120 you're landing on a pinnacle. 423 00:20:53,120 --> 00:20:56,900 And the reason for that is if you're landing on a pinnacle, 424 00:20:56,900 --> 00:20:59,540 you don't get a sensation of your forward speed 425 00:20:59,540 --> 00:21:01,250 from the ground rushing by. 426 00:21:01,250 --> 00:21:04,220 So the idea in the helicopter is to land, 427 00:21:04,220 --> 00:21:05,570 unlike with the airplane. 428 00:21:05,570 --> 00:21:09,150 It's actually a little bit less unnerving than an airplane. 429 00:21:09,150 --> 00:21:13,370 Some people get a little bit ground-shy in the airplane. 430 00:21:13,370 --> 00:21:17,510 They're happy flying 80 knots in the pattern, 431 00:21:17,510 --> 00:21:21,020 but they're not that happy flying 70 knots 432 00:21:21,020 --> 00:21:23,330 10 feet above the runway, which makes sense, 433 00:21:23,330 --> 00:21:26,000 because you don't want to slam into the ground going really 434 00:21:26,000 --> 00:21:27,020 fast. 435 00:21:27,020 --> 00:21:30,080 The good news is in the helicopter, 436 00:21:30,080 --> 00:21:31,797 you never get to that phase where 437 00:21:31,797 --> 00:21:33,380 you're going fast close to the ground, 438 00:21:33,380 --> 00:21:35,300 because when you're landing, you just 439 00:21:35,300 --> 00:21:40,713 say in my peripheral vision, how fast is the ground rushing by? 440 00:21:40,713 --> 00:21:42,380 And you just kind of keep that constant. 441 00:21:42,380 --> 00:21:44,870 Whatever it was up at 500 feet above the ground, 442 00:21:44,870 --> 00:21:48,090 that's what you want when you're five feet above the ground. 443 00:21:48,090 --> 00:21:49,828 And you'll very naturally slow down. 444 00:21:49,828 --> 00:21:51,620 You'll do the right-- your natural instinct 445 00:21:51,620 --> 00:21:54,530 to slow down as the ground begins rushing 446 00:21:54,530 --> 00:21:56,640 is a helpful one in the helicopter. 447 00:21:56,640 --> 00:21:59,780 So your peripheral vision is used for speed reference, 448 00:21:59,780 --> 00:22:05,300 and the spot moving up or down is used for a descent rate 449 00:22:05,300 --> 00:22:06,650 reference. 450 00:22:06,650 --> 00:22:10,778 And that's why you never have to look inside at the gauges, 451 00:22:10,778 --> 00:22:13,070 except when you're landing on top of an office building 452 00:22:13,070 --> 00:22:15,250 or something. 453 00:22:15,250 --> 00:22:19,730 Can you land the helicopter without power? 454 00:22:19,730 --> 00:22:21,167 It turns out the answer is yes. 455 00:22:21,167 --> 00:22:22,750 You have these three buckets of energy 456 00:22:22,750 --> 00:22:25,270 that I alluded to earlier-- 457 00:22:25,270 --> 00:22:28,540 kinetic from your forward airspeed, potential 458 00:22:28,540 --> 00:22:32,260 from being up high, and then another form of kinetic, 459 00:22:32,260 --> 00:22:34,930 which we'll call "blade inertia" from the relatively heavy 460 00:22:34,930 --> 00:22:37,070 blades spinning. 461 00:22:37,070 --> 00:22:40,300 So raise your hand if you think the forward airspeed is 462 00:22:40,300 --> 00:22:43,930 number one in terms of size. 463 00:22:43,930 --> 00:22:45,320 Let's rank these. 464 00:22:45,320 --> 00:22:49,480 What's the biggest-- airspeed, a heavy helicopter 465 00:22:49,480 --> 00:22:53,200 going 100 knots, potential energy, 466 00:22:53,200 --> 00:22:57,070 helicopter having been lifted up off the ground, 467 00:22:57,070 --> 00:23:01,720 or the blades whipping around near the speed of sound? 468 00:23:01,720 --> 00:23:04,770 Who votes for one, forward airspeed? 469 00:23:04,770 --> 00:23:05,270 A few. 470 00:23:05,270 --> 00:23:08,390 Who votes for potential? 471 00:23:08,390 --> 00:23:09,020 A fair number. 472 00:23:09,020 --> 00:23:11,773 Who votes for blade inertia, the blades whipping around? 473 00:23:11,773 --> 00:23:12,440 All right, good. 474 00:23:12,440 --> 00:23:14,720 We've got a good distribution. 475 00:23:14,720 --> 00:23:15,920 Let me give you-- 476 00:23:15,920 --> 00:23:21,410 I'll tell you about, I think it was a crazy French guy who 477 00:23:21,410 --> 00:23:25,510 got into what's now called a Eurocopter, an Alouette, 478 00:23:25,510 --> 00:23:28,670 went up to 40,000 feet to set an altitude record. 479 00:23:28,670 --> 00:23:30,800 The record was set when the engines flamed out-- 480 00:23:30,800 --> 00:23:35,450 that's why it's 40,000 and change, not 41,000 and change-- 481 00:23:35,450 --> 00:23:38,940 and then auto-rotated all the way down to the ground. 482 00:23:38,940 --> 00:23:43,490 So whatever energy bucket that was there 483 00:23:43,490 --> 00:23:45,840 had to be sufficient to make it all the way the ground. 484 00:23:45,840 --> 00:23:48,020 So what does that tell you the biggest one is? 485 00:23:48,020 --> 00:23:53,280 It's got to be something that scales up to 40,000 feet. 486 00:23:53,280 --> 00:23:54,475 Potential, yeah. 487 00:23:54,475 --> 00:23:56,100 So potential energy is a good candidate 488 00:23:56,100 --> 00:23:58,440 for the biggest, because again, you've 489 00:23:58,440 --> 00:24:00,750 got to keep the rotors spinning for longer if you're 490 00:24:00,750 --> 00:24:04,757 auto-rotating from 10,000 feet or 50,000 feet or wherever. 491 00:24:04,757 --> 00:24:06,840 I don't think that record's been broken, actually. 492 00:24:06,840 --> 00:24:09,420 It was set in the '70s. 493 00:24:09,420 --> 00:24:12,780 So number two is the forward airspeed of the helicopter. 494 00:24:12,780 --> 00:24:15,810 The blade inertia isn't good for much except for cushioning 495 00:24:15,810 --> 00:24:18,460 your fall from five or 10 feet above the ground. 496 00:24:18,460 --> 00:24:22,470 So what you do in the helicopter if the engine were to fail-- 497 00:24:22,470 --> 00:24:24,210 number one reason is fuel starvation 498 00:24:24,210 --> 00:24:25,680 from failing to top it off. 499 00:24:25,680 --> 00:24:29,910 Helicopters are often short on payload, so people will say, 500 00:24:29,910 --> 00:24:33,120 I want to take these seven people somewhere, 501 00:24:33,120 --> 00:24:35,660 and I'd be overweight if I fill the fuel tank. 502 00:24:35,660 --> 00:24:39,877 So I'll put in half an hour of fuel for this 15 minute trip. 503 00:24:39,877 --> 00:24:41,210 Actually, that would be illegal. 504 00:24:41,210 --> 00:24:42,630 20 minutes is the minimum reserve. 505 00:24:42,630 --> 00:24:45,370 So I'll put in half an hour of fuel for this 10 minute trip, 506 00:24:45,370 --> 00:24:50,060 and then there's a bit of a delay, and you run out of fuel. 507 00:24:50,060 --> 00:24:52,890 There is a warning light at 10 minutes. 508 00:24:52,890 --> 00:24:55,440 And the good news is you can land in a field, a baseball 509 00:24:55,440 --> 00:24:57,750 field, pretty easily. 510 00:24:57,750 --> 00:25:00,360 So the engine quits for whatever reason. 511 00:25:00,360 --> 00:25:03,180 Let's say you run out of fuel. 512 00:25:03,180 --> 00:25:07,350 You want to get to 60 or 70 knots, some reasonable air 513 00:25:07,350 --> 00:25:07,895 speed. 514 00:25:07,895 --> 00:25:09,270 And then the challenge is to hold 515 00:25:09,270 --> 00:25:11,740 that airspeed even as the ground is rushing up at you. 516 00:25:11,740 --> 00:25:13,740 You hold it right till you're at treetop height, 517 00:25:13,740 --> 00:25:15,450 about 40 feet above the ground. 518 00:25:15,450 --> 00:25:18,750 Then you begin to flare, just like in an airplane flaring 519 00:25:18,750 --> 00:25:19,860 for landing. 520 00:25:19,860 --> 00:25:22,330 You scrub off that forward speed. 521 00:25:22,330 --> 00:25:24,150 And that reduces your descent rate. 522 00:25:24,150 --> 00:25:28,200 So you can reduce your descent rate to zero 523 00:25:28,200 --> 00:25:30,510 by bleeding off all of that energy 524 00:25:30,510 --> 00:25:32,160 from the forward airspeed. 525 00:25:32,160 --> 00:25:34,770 And the kinetic energy, remember, is mv squared. 526 00:25:34,770 --> 00:25:35,770 So it's very important. 527 00:25:35,770 --> 00:25:40,170 There's twice as much energy at 70 knots compared to 50 knots. 528 00:25:40,170 --> 00:25:42,450 So once you've scrubbed off all your descent 529 00:25:42,450 --> 00:25:46,317 rate and all your forward speed, you're like this. 530 00:25:46,317 --> 00:25:47,650 So your tail is going to be low. 531 00:25:47,650 --> 00:25:49,608 And now you're going to just fall to the ground 532 00:25:49,608 --> 00:25:50,620 and hit the tail first. 533 00:25:50,620 --> 00:25:52,815 So it's not going to be an FAA quality-- 534 00:25:52,815 --> 00:25:54,690 you're going to walk away, but it's not going 535 00:25:54,690 --> 00:25:56,680 to be an FAA-quality landing. 536 00:25:56,680 --> 00:25:59,620 So what you can do is stick forward 537 00:25:59,620 --> 00:26:04,270 and settle by pulling up on the collective. 538 00:26:04,270 --> 00:26:06,442 So you stick forward to level the skids. 539 00:26:06,442 --> 00:26:08,650 And then when you're about five feet above the ground 540 00:26:08,650 --> 00:26:10,307 or maybe two feet above the ground, 541 00:26:10,307 --> 00:26:11,890 you start pulling up on the collective 542 00:26:11,890 --> 00:26:14,470 to cushion your fall that last few feet. 543 00:26:14,470 --> 00:26:16,480 So you've used up potential energy 544 00:26:16,480 --> 00:26:18,220 keeping the blades windmilling. 545 00:26:18,220 --> 00:26:20,953 If you just flatten the collective, 546 00:26:20,953 --> 00:26:22,870 the blades will have a relatively normal angle 547 00:26:22,870 --> 00:26:27,633 of attack to the air that's now coming from below. 548 00:26:27,633 --> 00:26:29,050 You've kept up your forward speed, 549 00:26:29,050 --> 00:26:30,850 and you bleed that off at the end 550 00:26:30,850 --> 00:26:35,200 to reduce your vertical speed. 551 00:26:35,200 --> 00:26:38,054 And then finally, you go-- 552 00:26:38,054 --> 00:26:41,036 [VIDEO PLAYBACK] 553 00:27:05,470 --> 00:27:06,613 The guy cheated. 554 00:27:06,613 --> 00:27:07,440 [END PLAYBACK] 555 00:27:07,440 --> 00:27:08,150 What's the cheat? 556 00:27:08,150 --> 00:27:11,900 And I'm telling you the cheat is you can hear it. 557 00:27:11,900 --> 00:27:14,030 You could hear the cheating going on. 558 00:27:14,030 --> 00:27:16,710 He landed with zero forward airspeed. 559 00:27:16,710 --> 00:27:17,210 Why? 560 00:27:20,930 --> 00:27:22,240 What enabled that? 561 00:27:22,240 --> 00:27:24,815 And like I said, you could hear it. 562 00:27:24,815 --> 00:27:27,605 AUDIENCE: [INAUDIBLE] 563 00:27:27,925 --> 00:27:30,050 PHILIP GREENSPUN: It's not from the engine running. 564 00:27:30,050 --> 00:27:32,060 The engine was presumably at idle. 565 00:27:32,060 --> 00:27:33,680 So what was the cheat? 566 00:27:33,680 --> 00:27:34,542 Nobody heard? 567 00:27:34,542 --> 00:27:36,250 AUDIENCE: The wind probably [INAUDIBLE].. 568 00:27:36,250 --> 00:27:38,360 PHILIP GREENSPUN: Wind, exactly, yes. 569 00:27:38,360 --> 00:27:39,256 What's your name? 570 00:27:39,256 --> 00:27:40,150 AUDIENCE: Messen. 571 00:27:40,150 --> 00:27:41,120 Messen. 572 00:27:41,120 --> 00:27:42,870 PHILIP GREENSPUN: Messen figured this out. 573 00:27:42,870 --> 00:27:45,050 So basically, he landed with probably-- it's 574 00:27:45,050 --> 00:27:47,600 very hard to kill all of your vertical speed 575 00:27:47,600 --> 00:27:49,380 and all of your forward speed. 576 00:27:49,380 --> 00:27:52,335 So if you go out and it's 15 knots down the runway, 577 00:27:52,335 --> 00:27:54,350 if you can just get down to 15 knots, 578 00:27:54,350 --> 00:27:57,440 and instead of sliding and going [MAKES NOISE] down the runway, 579 00:27:57,440 --> 00:28:01,010 which is common and not harmful to the helicopter, 580 00:28:01,010 --> 00:28:04,220 you'll have a perfect, what looks like a perfect landing. 581 00:28:04,220 --> 00:28:04,970 It's very hard. 582 00:28:04,970 --> 00:28:07,700 In the big helicopters like a Huey or something, 583 00:28:07,700 --> 00:28:11,958 it's practical to do a zero/zero landing out of an auto 584 00:28:11,958 --> 00:28:12,500 all the time. 585 00:28:12,500 --> 00:28:17,142 In a Robinson, it can be tough, but the wind helps hugely. 586 00:28:17,142 --> 00:28:19,100 And like I said, the throttle was down at idle, 587 00:28:19,100 --> 00:28:20,892 so the engine is not really doing anything. 588 00:28:20,892 --> 00:28:21,467 Question? 589 00:28:21,467 --> 00:28:23,300 AUDIENCE: The tail rotor was still spinning. 590 00:28:23,300 --> 00:28:25,872 Is auto-rotating [INAUDIBLE]? 591 00:28:25,872 --> 00:28:27,080 PHILIP GREENSPUN: It is, yes. 592 00:28:27,080 --> 00:28:27,997 Great, great question. 593 00:28:27,997 --> 00:28:32,060 So there's a sprag clutch, which prevents the rotor system 594 00:28:32,060 --> 00:28:38,910 from trying to drive the engine, because that would 595 00:28:38,910 --> 00:28:42,240 introduce a lot more drag. 596 00:28:42,240 --> 00:28:44,955 But the main rotor and the tail rotor 597 00:28:44,955 --> 00:28:48,330 are yoked together, so you still have tail rotor control. 598 00:28:48,330 --> 00:28:48,960 Great question. 599 00:28:48,960 --> 00:28:53,545 AUDIENCE: [INAUDIBLE] directional, 600 00:28:53,545 --> 00:28:56,290 because you don't really need the torque anymore, so-- 601 00:28:56,290 --> 00:28:58,123 PHILIP GREENSPUN: Yeah, you don't need much. 602 00:28:58,123 --> 00:29:00,050 I don't know. 603 00:29:00,050 --> 00:29:02,000 I'll have to think about why it's useful. 604 00:29:02,000 --> 00:29:02,875 AUDIENCE: [INAUDIBLE] 605 00:29:02,875 --> 00:29:04,917 PHILIP GREENSPUN: Yeah, it's not useful for much. 606 00:29:04,917 --> 00:29:05,872 That's for sure. 607 00:29:05,872 --> 00:29:08,080 One thing that is good about it is the hydraulic pump 608 00:29:08,080 --> 00:29:09,680 is also geared to the transmission. 609 00:29:09,680 --> 00:29:11,320 So you still have hydraulic boost 610 00:29:11,320 --> 00:29:13,755 even if you're auto-rotating from super high. 611 00:29:13,755 --> 00:29:15,130 What can you do with a helicopter 612 00:29:15,130 --> 00:29:16,630 if you have a private? 613 00:29:16,630 --> 00:29:21,010 You can visit schools. 614 00:29:21,010 --> 00:29:25,013 I visited the Winchester Public Schools. 615 00:29:25,013 --> 00:29:26,680 I'm not sure you can give them all rides 616 00:29:26,680 --> 00:29:28,030 if you only have a private. 617 00:29:28,030 --> 00:29:29,488 There's some kind of-- like I said, 618 00:29:29,488 --> 00:29:30,865 there's those charity laws that-- 619 00:29:30,865 --> 00:29:32,740 regulations that we don't really worry about, 620 00:29:32,740 --> 00:29:34,780 because we have commercial certificate 621 00:29:34,780 --> 00:29:36,780 and a letter of authority from the [INAUDIBLE].. 622 00:29:36,780 --> 00:29:40,420 But here's one of the East Coast Aero Club helicopters. 623 00:29:40,420 --> 00:29:42,730 I flew to the public schools in Winchester. 624 00:29:42,730 --> 00:29:44,560 I gave all the kids rides. 625 00:29:44,560 --> 00:29:47,650 And when we flew over houses like this, 626 00:29:47,650 --> 00:29:51,940 I said, oh, that's just like the house where I grew up. 627 00:29:51,940 --> 00:29:54,220 If you do that with kids from Weston and Lincoln, 628 00:29:54,220 --> 00:29:55,110 they believe you. 629 00:29:55,110 --> 00:29:58,930 They don't parse that as an ironic statement. 630 00:29:58,930 --> 00:30:01,450 Helicopter pilot careers, just in case any of you guys 631 00:30:01,450 --> 00:30:05,800 are thinking about leaving the desk where all the people work 632 00:30:05,800 --> 00:30:08,020 as a flight instructor, fly tours 633 00:30:08,020 --> 00:30:10,540 in the Grand Canyon or Alaska, and then they'll 634 00:30:10,540 --> 00:30:15,130 either go to offshore oil or Medevac after that. 635 00:30:15,130 --> 00:30:19,360 Usually offshore oil used to be easier to get. 636 00:30:19,360 --> 00:30:22,930 When oil prices are low, when oil catches a cold, 637 00:30:22,930 --> 00:30:25,715 the helicopter industry catches the flu. 638 00:30:25,715 --> 00:30:28,090 They shut down these oil rigs and there's a lot less need 639 00:30:28,090 --> 00:30:30,100 for helicopter transport. 640 00:30:30,100 --> 00:30:32,200 Medevac is kind of considered the plum job. 641 00:30:32,200 --> 00:30:34,300 That's my friend, Marcus. 642 00:30:34,300 --> 00:30:35,800 He trained at East Coast Aero Club 643 00:30:35,800 --> 00:30:41,050 and now he does 12-hour shifts at a volunteer fire station. 644 00:30:41,050 --> 00:30:45,340 And he gets paid in North Carolina 645 00:30:45,340 --> 00:30:48,430 and goes hospital to hospital, or sometimes picks people 646 00:30:48,430 --> 00:30:50,240 up off of highways and stuff. 647 00:30:50,240 --> 00:30:51,740 So what can you do? 648 00:30:51,740 --> 00:30:55,380 You can fly low and slow both legally and safely. 649 00:30:55,380 --> 00:30:57,310 You saw there was a carve-out for helicopters 650 00:30:57,310 --> 00:30:59,380 able to fly lower. 651 00:30:59,380 --> 00:31:04,290 One problematic aspect of flying Piper Warriors and Cessnas 652 00:31:04,290 --> 00:31:07,240 is that people-- 653 00:31:07,240 --> 00:31:09,970 their expectations of what an aircraft is and what it can do 654 00:31:09,970 --> 00:31:12,730 has been set by their airline experience. 655 00:31:12,730 --> 00:31:14,590 And the first time you try to get up and use 656 00:31:14,590 --> 00:31:16,520 the bathroom in your Piper, you'll 657 00:31:16,520 --> 00:31:19,360 discover that JetBlue has some advantages in the aircraft 658 00:31:19,360 --> 00:31:20,220 department. 659 00:31:20,220 --> 00:31:21,970 And your passengers will notice this, too. 660 00:31:21,970 --> 00:31:23,120 This is noisy. 661 00:31:23,120 --> 00:31:24,490 It's not climate controlled. 662 00:31:24,490 --> 00:31:26,830 There's no bathroom. 663 00:31:26,830 --> 00:31:28,990 The helicopters are awesome, because people usually 664 00:31:28,990 --> 00:31:30,400 haven't even been in one, so it's 665 00:31:30,400 --> 00:31:31,608 a whole different experience. 666 00:31:31,608 --> 00:31:33,370 There's a different view. 667 00:31:33,370 --> 00:31:36,310 You can take them on a 10-minute ride from Hanscom Field 668 00:31:36,310 --> 00:31:36,850 and go back. 669 00:31:36,850 --> 00:31:38,517 You don't have to say, oh, let's go have 670 00:31:38,517 --> 00:31:39,730 lunch in Martha's Vineyard. 671 00:31:39,730 --> 00:31:40,930 You just take them on a little tour 672 00:31:40,930 --> 00:31:42,388 and they say, wow, this is awesome. 673 00:31:42,388 --> 00:31:45,960 So when I actually want to show people what GA is like 674 00:31:45,960 --> 00:31:47,500 and what my world is like, I usually 675 00:31:47,500 --> 00:31:49,270 take them for a helicopter ride. 676 00:31:49,270 --> 00:31:51,160 I don't take them for a trip. 677 00:31:51,160 --> 00:31:53,790 The serious is for transportation, 678 00:31:53,790 --> 00:31:55,750 and the helicopter is really what 679 00:31:55,750 --> 00:31:58,780 I think of as the kind of aviation dream 680 00:31:58,780 --> 00:32:01,990 that people had in ancient Greece. 681 00:32:01,990 --> 00:32:05,530 They didn't dream of going to LA in six hours. 682 00:32:05,530 --> 00:32:10,570 They dreamed of soaring like a bird. 683 00:32:10,570 --> 00:32:12,172 You can land off-airport. 684 00:32:12,172 --> 00:32:13,630 That's where a lot of the challenge 685 00:32:13,630 --> 00:32:15,640 comes from the helicopter. 686 00:32:15,640 --> 00:32:17,500 People think you're a pilot of heroic skill 687 00:32:17,500 --> 00:32:19,450 if you take off and land at Hanscom. 688 00:32:19,450 --> 00:32:20,700 That's not very challenging. 689 00:32:20,700 --> 00:32:22,270 It's not really that different. 690 00:32:22,270 --> 00:32:25,960 And in some ways, it's easier than taking off and landing 691 00:32:25,960 --> 00:32:28,605 in a Piper or a Cessna. 692 00:32:28,605 --> 00:32:29,980 When you're off-airport, you have 693 00:32:29,980 --> 00:32:33,490 to exercise a lot of judgment, a lot of skill. 694 00:32:33,490 --> 00:32:35,770 And that's part of your training. 695 00:32:35,770 --> 00:32:38,020 But it's also where people get in trouble 696 00:32:38,020 --> 00:32:40,270 hitting obstacles and stuff. 697 00:32:40,270 --> 00:32:43,840 If you do get all of your airplane skills, 698 00:32:43,840 --> 00:32:47,600 you can transfer them over to helicopters very easily. 699 00:32:47,600 --> 00:32:50,500 It's 30 hours minimum of additional training 700 00:32:50,500 --> 00:32:51,940 to add a helicopter rating. 701 00:32:51,940 --> 00:32:54,200 40 is probably a good budget number. 702 00:32:54,200 --> 00:32:54,700 All right. 703 00:32:54,700 --> 00:32:57,730 Are there helicopter questions? 704 00:33:00,950 --> 00:33:02,330 AUDIENCE: [INAUDIBLE]. 705 00:33:05,100 --> 00:33:06,830 Can you just pick [INAUDIBLE]? 706 00:33:06,830 --> 00:33:07,630 OK, here it is. 707 00:33:07,630 --> 00:33:10,140 Or like, who's going to tell you [INAUDIBLE]?? 708 00:33:10,140 --> 00:33:12,462 PHILIP GREENSPUN: That is a great question. 709 00:33:12,462 --> 00:33:13,920 Is there any regulation about where 710 00:33:13,920 --> 00:33:16,860 you can land your helicopter? 711 00:33:16,860 --> 00:33:23,010 The answer is until about 5 or 10 years ago, there wasn't any. 712 00:33:23,010 --> 00:33:25,380 So it was just permission of the property owner 713 00:33:25,380 --> 00:33:27,690 and don't do anything careless or reckless. 714 00:33:27,690 --> 00:33:33,510 So basically, the whole world was open to helicopter pilots. 715 00:33:33,510 --> 00:33:36,570 There is a little bit of a tweaking of the law. 716 00:33:36,570 --> 00:33:39,150 The FAA passed this-- 717 00:33:39,150 --> 00:33:40,980 they added this regulation that I 718 00:33:40,980 --> 00:33:42,750 think was intended for airplanes, 719 00:33:42,750 --> 00:33:46,472 but they forgot to carve it out. 720 00:33:46,472 --> 00:33:48,930 So they said if you make more than 10 takeoffs and landings 721 00:33:48,930 --> 00:33:50,870 in the same place in a year, then 722 00:33:50,870 --> 00:33:53,850 you have to get it approved as an airport with a huge amount 723 00:33:53,850 --> 00:33:55,120 of regulation. 724 00:33:55,120 --> 00:33:58,080 I think it was intended for mining companies that would 725 00:33:58,080 --> 00:33:59,835 set up their own landing strip. 726 00:33:59,835 --> 00:34:01,060 It doesn't really make sense. 727 00:34:01,060 --> 00:34:03,060 For helicopters, like if you have a construction 728 00:34:03,060 --> 00:34:05,220 site that you want to regularly visit, now 729 00:34:05,220 --> 00:34:07,890 it's a bit of a hassle because that 11th landing, in theory, 730 00:34:07,890 --> 00:34:10,290 you need it to get approval as an airport. 731 00:34:10,290 --> 00:34:12,870 But as a first approximation, you 732 00:34:12,870 --> 00:34:15,000 can land anywhere that the property 733 00:34:15,000 --> 00:34:19,120 owner is happy to host you. 734 00:34:19,120 --> 00:34:20,862 And towns, also. 735 00:34:20,862 --> 00:34:22,570 They're really aggressive about harassing 736 00:34:22,570 --> 00:34:26,883 people who try to have a helipad at their house now, 737 00:34:26,883 --> 00:34:27,800 just because they can. 738 00:34:27,800 --> 00:34:29,960 They get them under zoning laws, even though they're not 739 00:34:29,960 --> 00:34:30,752 really supposed to. 740 00:34:30,752 --> 00:34:32,929 The FAA is supposed to have exclusive authority 741 00:34:32,929 --> 00:34:34,580 to regulate aviation. 742 00:34:34,580 --> 00:34:36,949 Because think about it-- there's all this-- 743 00:34:36,949 --> 00:34:39,590 there's so many levels of government in the US. 744 00:34:39,590 --> 00:34:43,405 If you let them all just forbid activities, 745 00:34:43,405 --> 00:34:44,780 eventually there would be nothing 746 00:34:44,780 --> 00:34:48,497 that was legal at all, because people in Concord and Lexington 747 00:34:48,497 --> 00:34:50,830 would say, we don't want airplanes flying over our head. 748 00:34:50,830 --> 00:34:56,400 So we'll just make it illegal to fly a Gulfstream in Concord. 749 00:34:56,400 --> 00:35:00,750 AUDIENCE: [INAUDIBLE] from flying [INAUDIBLE]?? 750 00:35:03,690 --> 00:35:05,690 PHILIP GREENSPUN: I had that in an earlier slide 751 00:35:05,690 --> 00:35:07,610 on learning to fly. 752 00:35:07,610 --> 00:35:10,710 The marginal cost is about double. 753 00:35:10,710 --> 00:35:17,190 So it goes from 150 an hour to 225, or 100 an hour 754 00:35:17,190 --> 00:35:21,360 to 200, because so many rotating components get discarded 755 00:35:21,360 --> 00:35:24,210 after 2,200 hours-- so the transmissions, 756 00:35:24,210 --> 00:35:26,890 the blades, and so forth. 757 00:35:26,890 --> 00:35:29,410 So it is more expensive per hour. 758 00:35:29,410 --> 00:35:32,040 However, like I also said, the flights 759 00:35:32,040 --> 00:35:33,330 tend to be a lot shorter. 760 00:35:33,330 --> 00:35:35,790 So I would say as a hobby overall, it's 761 00:35:35,790 --> 00:35:38,760 about the same cost, because you're not dragging people 762 00:35:38,760 --> 00:35:40,752 all the way to the Vineyard or Bar Harbor. 763 00:35:40,752 --> 00:35:42,210 You're just taking them into Boston 764 00:35:42,210 --> 00:35:46,830 and back out, which is about 20 minutes of flight time 765 00:35:46,830 --> 00:35:51,110 and 30 minutes of engine running time. 766 00:35:51,110 --> 00:35:54,050 Whereas an intro airplane flight would be an all day thing. 767 00:35:54,050 --> 00:35:56,910 You'd probably fly a couple hours, two or three hours. 768 00:35:56,910 --> 00:36:01,210 So you actually probably spend more with the airplane. 769 00:36:01,210 --> 00:36:02,210 That's a great question. 770 00:36:04,970 --> 00:36:07,470 All right, so I guess we should take a 10-minute restroom 771 00:36:07,470 --> 00:36:08,550 break. 772 00:36:08,550 --> 00:36:13,340 And after that, we're going to hear from Laz about the F-22.