WEBVTT Kind: captions Language: en-GB 1 00:00:00.130 --> 00:00:05.520 I am in an unpowered glider somewhere over Oxfordshire, with Bruce, my pilot and instructor, 2 00:00:05.520 --> 00:00:07.700 behind me. Bruce, thank you very much. 3 00:00:07.700 --> 00:00:10.000 And I have a bottle of water with me. 4 00:00:10.000 --> 00:00:14.400 Now we're in level flight at the moment, so as you'd expect, the water in the bottle is about level. 5 00:00:14.450 --> 00:00:17.119 But watch what happens when we start to turn. 6 00:00:17.119 --> 00:00:20.819 Bruce, give us a -- there we go. Bit of a turn to the left. 7 00:00:20.819 --> 00:00:22.819 Oh, that's a heck of a view! Now, look at that. 8 00:00:22.819 --> 00:00:28.749 Have a look at the horizon line. According to the camera, it's massively away from horizontal. 9 00:00:28.749 --> 00:00:33.860 But look at this bottle: the water level here is still flat. If you can't see the horizon, 10 00:00:33.860 --> 00:00:36.410 then as far as you're concerned: you're not in a turn. 11 00:00:36.410 --> 00:00:38.100 And look how fast we're going round! 12 00:00:38.100 --> 00:00:41.370 Now, that's very strange, isn't it? But if you've ever been in a jetliner, an actual 13 00:00:41.370 --> 00:00:46.380 commercial aircraft, you'll know that: a commercial aircraft can do this kind of turn without 14 00:00:46.380 --> 00:00:49.860 slopping your in-flight meal or your drink all over the place. 15 00:00:49.860 --> 00:00:51.690 Thank you, Bruce, let's go back to level. 16 00:00:51.690 --> 00:00:55.260 So what would happen if we couldn't see the horizon? 17 00:00:55.260 --> 00:00:59.840 'Cos there's some really weird sensory illusions that come into effect there. 18 00:00:59.840 --> 00:01:03.930 If you lose sight of the horizon, and you've been turning for about 15-20 seconds, your 19 00:01:03.930 --> 00:01:08.479 ears, the balance centres of your brain, get used to it. The only difference you feel is 20 00:01:08.479 --> 00:01:12.549 a little bit of G-force, but that's really difficult to detect. 21 00:01:12.549 --> 00:01:16.249 And if all you've got to go on is what you think is down: well, the forces are adding 22 00:01:16.249 --> 00:01:20.929 up so down is always going to be towards your feet even if you're turning. 23 00:01:20.929 --> 00:01:24.499 And even a bottle of water or something isn't going to clue you in. 24 00:01:24.499 --> 00:01:29.039 So again, as we turn to the right: still straight here. 25 00:01:29.039 --> 00:01:32.389 So if we were a little bit higher, if we were under those quite scary clouds above us, and 26 00:01:32.389 --> 00:01:33.950 we couldn't see: 27 00:01:33.950 --> 00:01:36.780 we wouldn't know if we were turning. And that's worrying. 28 00:01:36.780 --> 00:01:41.459 Because if you turn, you start to lose a little bit of altitude. And if you're starting to 29 00:01:41.459 --> 00:01:45.889 descend, if your altimeter says you're going down: and you think you're flying le vel? 30 00:01:45.889 --> 00:01:51.450 Then you're going to pull up, to try and keep your height together. In a turn, that just 31 00:01:51.450 --> 00:01:55.639 makes it worse. That just tightens the turn and tightens the turn, and you go into something 32 00:01:55.639 --> 00:01:59.810 that is a called the graveyard spiral, for obvious reasons. 33 00:01:59.810 --> 00:02:04.420 That is also the reason that we are not flying in cloud or at night. 34 00:02:04.420 --> 00:02:09.640 BRUCE: I'm going to accelerate to 100 knots, pull up level, and then gradually pull up... 35 00:02:09.640 --> 00:02:10.729 TOM: Oh boy. Yep, yep, yep. 36 00:02:10.729 --> 00:02:11.460 BRUCE: Here we go. 37 00:02:11.460 --> 00:02:13.260 TOM: Oh boy. Oh boy. Don't freak out. 38 00:02:13.300 --> 00:02:18.740 Don't freak out. Don't freak out. Don't freak out. 39 00:02:18.740 --> 00:02:19.860 [SHOUTING] 40 00:02:19.860 --> 00:02:23.250 BRUCE: Look up. 41 00:02:23.250 --> 00:02:29.350 TOM: Oh my. Oh wow. [INCOHERENT] 42 00:02:29.350 --> 00:02:31.980 BRUCE: Yee-ha! 43 00:02:31.980 --> 00:02:35.230 TOM: Bruce. Thank you so much. 44 00:02:35.230 --> 00:02:36.390 BRUCE: That was awesome. 45 00:02:36.390 --> 00:02:40.790 TOM: Bruce is from the Edinburgh University Gliding Club, I also need to thank the Loughborough 46 00:02:40.790 --> 00:02:43.720 University Gliding Club and Alistair who brought me up here. 47 00:02:43.720 --> 00:02:46.960 Let's get safely down on the ground. Thank you so much. 48 00:02:46.960 --> 00:02:55.500 That was astonishing.