Gliding - airbrakes in final turn

[IFMU]

Originally Posted by mary meagher

Theres only one thing for it, you must pay us a visit! Volcanos permitting, of course.

Mary,

Should I ever get over there I would love to check out the local soaring hospitality. Perhaps some day business will take me there.

I suspect that though we root through the differences on these threads, it is hard not to find common ground while in the air, or even over a beer talking flying. I have found this whole discussion rather interesting.

Hope your health issues subside, and you can get airborne again.

-- IFMU

[douglas.lindsay]

They are also encouraged to do a well banked turn (say 30 degrees) since there is evidence that it is more difficult to spin from such a turn as compared to a flat turn if speed is lost.

I'm intrigued - my gliding instructors have taught me to turn final at 30 deg but my power instructor wasn't keen on anything above 20 deg. Is there a difference between gliders and power here, or just different traditions? Anybody any idea? Any books I can read that explain a bit more?

[gpn01]

Originally Posted by douglas.lindsay

I'm intrigued - my gliding instructors have taught me to turn final at 30 deg but my power instructor wasn't keen on anything above 20 deg. Is there a difference between gliders and power here, or just different traditions? Anybody any idea? Any books I can read that explain a bit more?

Anecdotal evidence (the best sort according to Dogbert) is that many power instructors are either wannabe airline pilots or are training novices with the expectation that they'll want to fly big jets with passengers in them. In either case passengers don't like it when their airplane banks steeply, ergo, power pilots tend to do gentle turns. Compare this to glider pilots who will sometimes fly at bank angles up to 60 degrees in order to stay with a small/tight thermal. I know that PPL's often express discomfort when a tight turn is demonstrated in a glider but once they realise that it doesn't cause the glider to fall out of the sky they do actually start to enjoy it :-)

[douglas.lindsay]

Yeah - I was a little reluctant the first couple of times I was told to execute a "well-banked turn onto finals" at about 60k in a K21 (unaccelerated stall at MAUW is ~40kts I think), but I'm happy enough doing it now. Not sure I want to do it much slower than that, though one instructor suggests I should pull the whole base/final segment back to 50...

But I was particularly interested in the suggestion that well-banked turns are less likely to produce a spin than, say, a gentle 15 degrees. Anybody got any more info on that bit? Or is it just because there's less chance of a subconscious boot to the rudder to pull the nose round?

[tinpilot]

Or is it just because there's less chance of a subconscious boot to the rudder to pull the nose round?

That's a big part of the reason.

Low-timers have a tendency to look down at the landing area rather than over the nose. An underbanked turn with a bit too much back pressure slows the glider down, add in your subconscious boot . . .

In a well banked turn, the tendency is for the nose to drop a little and the glider picks up a few extra knots - untidy but safe.

Stall speed for the K21 is in the high 30s, yellow triangle speed is 49 knots. I would consider 50 knots to be a safe minimum approach speed for perfect conditions (ie dead calm, clean wings, flat airfield).

[cats_five]

Suggest you ask Kevin about this on Thursday - assuming you are the Douglas I think you are!

[ProfChrisReed]

Part of the reason is that many (most even?) gliders don't have enough elevator authority to stall the aircraft in a well-banked turn. In my Open Cirrus I can thermal at 45 degrees with the stick full back, though the buffet shows I'm near the stall and a gust can tip the balance.

Something to explore at height I'd say.

Another reason is that a 45 degree banked turn completes the turn with the lowest possible height loss - although the glider sinks faster than at 20 degrees the amount of time in the turn is less and more than compensates.

All these are explained properly in the standard books for pre-solo glider training.

[douglas.lindsay]

Stall speed for the K21 is in the high 30s

I'm probably being too cautious, then... it was dead calm (or nearly) and of course when we did turn final at 50k the thing was solid as a rock, no lack of authority, no buffet, etc - but I was rather keenly aware of how good my speed control had to be. And of how finely controlled my round-out - er - isn't yet.

Thanks all, interesting stuff. And cats_five, let me know who you are on Thursday

[gpn01]

Originally Posted by douglas.lindsay

I'm probably being too cautious, then... it was dead calm (or nearly) and of course when we did turn final at 50k the thing was solid as a rock, no lack of authority, no buffet, etc - but I was rather keenly aware of how good my speed control had to be. And of how finely controlled my round-out - er - isn't yet.

Thanks all, interesting stuff. And cats_five, let me know who you are on Thursday

No doubt your instructor(s) will soon be demonstrating stalling in various attitudes and showing how G-loading affects your stalling speed. This'll be a good opportunity for you to learn what the speed at which the particular glider you're flying, in its configuration on the day (i.e. pilot weights, how clean/dirty/wet the wings are, etc.) stalls at when flying straight and how this changes according to various G-loadings (achieved by altering bank angles).