G-Forces, Gliders, and Graveyard Spirals

G-Forces, Gliders, and Graveyard Spirals


I am in an unpowered glider somewhere over
Oxfordshire, with Bruce, my pilot and instructor, behind me. Bruce, thank you very much. And I have a bottle of water with me. Now we’re in level flight at the moment, so
as you’d expect, the water in the bottle is about level. But watch what happens when we start to turn. Bruce, give us a — there we go. Bit of a
turn to the left. Oh, that’s a heck of a view! Now, look at
that. Have a look at the horizon line. According
to the camera, it’s massively away from horizontal. But look at this bottle: the water level here
is still flat. If you can’t see the horizon, then as far as you’re concerned: you’re not
in a turn. And look how fast we’re going round! Now, that’s very strange, isn’t it? But if
you’ve ever been in a jetliner, an actual commercial aircraft, you’ll know that: a commercial
aircraft can do this kind of turn without slopping your in-flight meal or your drink
all over the place. Thank you, Bruce, let’s go back to level. So what would happen if we couldn’t see the
horizon? ‘Cos there’s some really weird sensory illusions
that come into effect there. If you lose sight of the horizon, and you’ve
been turning for about 15-20 seconds, your ears, the balance centres of your brain, get
used to it. The only difference you feel is a little bit of G-force, but that’s really
difficult to detect. And if all you’ve got to go on is what you
think is down: well, the forces are adding up so down is always going to be towards your
feet even if you’re turning. And even a bottle of water or something isn’t
going to clue you in. So again, as we turn to the right: still straight
here. So if we were a little bit higher, if we were
under those quite scary clouds above us, and we couldn’t see: we wouldn’t know if we were turning. And that’s
worrying. Because if you turn, you start to lose a little
bit of altitude. And if you’re starting to descend, if your altimeter says you’re going
down: and you think you’re flying le vel? Then you’re going to pull up, to try and keep
your height together. In a turn, that just makes it worse. That just tightens the turn
and tightens the turn, and you go into something that is a called the graveyard spiral, for
obvious reasons. That is also the reason that we are not flying
in cloud or at night. BRUCE: I’m going to accelerate to 100 knots,
pull up level, and then gradually pull up… TOM: Oh boy. Yep, yep, yep. BRUCE: Here we go. TOM: Oh boy. Oh boy. Don’t freak out. Don’t freak out. Don’t freak out.
Don’t freak out. [SHOUTING] BRUCE: Look up. TOM: Oh my. Oh wow. [INCOHERENT] BRUCE: Yee-ha! TOM: Bruce. Thank you so much. BRUCE: That was awesome. TOM: Bruce is from the Edinburgh University
Gliding Club, I also need to thank the Loughborough University Gliding Club and Alistair who brought
me up here. Let’s get safely down on the ground. Thank
you so much. That was astonishing.

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