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#21
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In article ,
Jim wrote: I have experienced stall buffet at 60 degrees of bank in a thermal in a DG-505, and I fly with a forward CG. Granted, stall buffet is not yet a stall, and the DG's stall characteristics may be pretty benign, but I no longer trust that a glider will be hard to stall in steep turns. I haven't flown a 505, but I've tried a DG-1000, and it has a *lot* of available elevator power compared to most recent training gliders. The thing can not only be held so deep into a stall that it will virtually always drop one wing or the other, it can be flick rolled! (and the POH permits that, with the 18m tips on) But it gave so much notice that you were dicing with the stall that I wouldn't be at all worried thermalling it slow. -- Bruce |
#22
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"Vaughn" wrote
that's what they teach their students because they don't know anything else. Actually there are many reasons, some of them may be found in the SEL PTS. True. I oversimplified. Far be it from me to suggest that the FAA isn't a big part of the problem - it is. Some of the stuff in the PTS is garbage. It's getting better again, though. Real slow flight is back - for several years, slow flight was redefined as 1.2 Vso. Steep turns were redefined to 45 degrees and I see no hope of change there. The 180 to a landing is back in the commercial PTS though, and that's a plus. Another is that airports with lots of light aircraft training end up with huge "follow the leader" patterns. Ah, yes - the "everybody is doing it" argument. Actually, I do understand - sometimes the safest thing to do is just grit your teeth and do it the same way everyone else does it. Only when I learned to fly I was taught that when the pattern is strung out that way, you hold your altitude until you reach power-off gliding distance of the field, then reduce to idle and glide in. Come to think of it, the FAA has changed landings since our trainers were designed. Vaguely 20 years ago, there was a sea change in the way landing technique was taught because someone in the FAA decided that normal landings would be accomplished with full flaps. Well, that makes sense to me. As far as I'm concerned, the normal landing is made with full flaps. Anything less is a special case - a reduced-workload training exercise for an early presolo student, strong crosswind in an airplane where flaps reduce rudder/elevator authority, that kind of deal. Otherwise, why accept the higher touchdown speed with its attendant risks, extra wear on tires and brakes, etc? The normal technique that is taught these days (at least in a Cezzna) is the first notch on downwind, second notch on base and full flaps on final. And there's the problem. What's wrong with a clean downwind, two notches on base to adjust the glide, and then the rest on final when it looks right? I was taught to land that way. In fact, I was taught to land a Cessna by bringing the power to idle abeam the numbers and adding flaps as necessary to control glideslope. Might have had something to do with the fact that my primary instructor flew gliders too... This adds so much drag that you either do a high (and or tight) pattern or you must drag the thing around the pattern with power. Guess which one they usually teach? Right - because that's all they know. They really don't know enough about flying a tight high pattern to teach it. In a multiengine turbine airplane, what they teach is actually the right thing to do. Those engines take time to spool up, so you dirty the plane up, keep the engines spooled up, and for a go-around you clean up the plane - this way you can get a climb going before the engines are fully spooled up. The problem is, we're flying light piston airplanes. Michael |
#23
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Because in a turn the inside wing is flying at a higher
AOA than the outside wing, the inside wing will likely stall, and drop, before the outside wing. I understand that in some gliders without the newer wing designs this inside wing stall may well be followed an eye-blink later with an out-the-bottom spin entry. Actually, this is a common misconception, but there is no such thing as an inside wing stall on any turn, unless it is a very shallow turn in a pre-stall configuration, and the pilot suddenly applies aileron opposite the turn, in which case the inside wing will stall first. This is the common situation when pilots are trying to prolong the glide by holding the nose high and doing skidding turns. The opposite aileron is the only way to prevent the wings from banking more (which is what the pilot is erroneously trying to prevent). That is why, it is repeated so many times, by so many people, so many books, that you can't spin from a steep turn, only from a shallow turn. The "Pooch" may be such a glider. I don't know where you got this from. The Puchacz has absolutely marvelous characteristics. I spun and instructed in them for years. |
#24
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"Gldcomp" wrote in message om... That is why, it is repeated so many times, by so many people, so many books, that you can't spin from a steep turn, only from a shallow turn. This is an overstatement. While it is certainly more difficult to spin from a steep turn, spins are possible from any attitude depending mostly on the CG position and the general susceptibility of the glider in question to spins. I have flown several gliders which would spin from an accelerated stall in a near 90 digree bank. Whether these gliders spin "over the top" or out the bottom" depends on the rudder input at the moment of the stall. It's an "E" ticket ride to be sure. Bill Daniels |
#25
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#26
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And as a general statement, it is completely bull****.
There are a lot of gliders which don't have the elevator authority to stall from a steep bank angle. However, there ARE gliders which can do that. Long wings help on that, and flying in turblent air like rotors (where you usually circle with decent bank angles) does help very well. -- Bert Willing ASW20 "TW" "Gldcomp" a écrit dans le message de om... That is why, it is repeated so many times, by so many people, so many books, that you can't spin from a steep turn, only from a shallow turn. |
#27
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On Mon, 14 Jun 2004 22:57:59 GMT, "Gldcomp"
wrote: Because in a turn the inside wing is flying at a higher AOA than the outside wing, the inside wing will likely stall, and drop, before the outside wing. I understand that in some gliders without the newer wing designs this inside wing stall may well be followed an eye-blink later with an out-the-bottom spin entry. Actually, this is a common misconception, but there is no such thing as an inside wing stall on any turn, unless it is a very shallow turn in a pre-stall configuration, and the pilot suddenly applies aileron opposite the turn, in which case the inside wing will stall first. Wow. "... there is no such thing as an inside wing stall on any turn, unless it is a very shallow turn ...". Maybe it's just me, but I think I'll just continue to consider this sort of stall something to be alert to. YMMV. This is the common situation when pilots are trying to prolong the glide by holding the nose high and doing skidding turns. The opposite aileron is the only way to prevent the wings from banking more (which is what the pilot is erroneously trying to prevent). That is why, it is repeated so many times, by so many people, so many books, that you can't spin from a steep turn, only from a shallow turn. The "Pooch" may be such a glider. I don't know where you got this from. The Puchacz has absolutely marvelous characteristics. I spun and instructed in them for years. |
#28
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Actually, this is a common misconception, but there is no such thing as an
inside wing stall on any turn, unless it is a very shallow turn in a pre-stall configuration, and the pilot suddenly applies aileron opposite the turn, in which case the inside wing will stall first. I had to think about this for a while. My thought process when something like this: If the AOA is the same on the inside and outside wing there will be no tendency for the wing to stall one way or the other. In a coordinated turn the AOA should be the same on the inside and outside wing. This is obviously true in level flight and in 90degree bank turn. However in a 45 degree bank turn it is obvious that the inside wing travels less distance than the outside wing in 360 degree turn, thus it must be flying at a lower relative airspeed than the outside wing. It turns out that this is what causes overbanking tendency. To compensate for overbanking tendancy the aircraft must have short wings and/or a lot of dihedral. Dihedrall effectivaly increases the wing area of the inside wing so and increase in AOA is not required. If there is not enought dihedral for the turn then the overbanking tendancy must be compensated for by the ailerons which increase the angle of attack of the inside wing. Thus you get an inside wing stall. A 2-33 should demostrate this very will as it has a very large overbanking tendancy. |
#29
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Actually, this is a common misconception, but there is no such thing as an
inside wing stall on any turn, unless it is a very shallow turn in a pre-stall configuration, and the pilot suddenly applies aileron opposite the turn, in which case the inside wing will stall first. Expanding on my previous thought process. Execesive Overbanking tendancy may be the reason that some aircraft won't (or at least are difficult to) stall the inside wing. The 2-33 for example the overbanking tendancy is so bad that it may run out of aileron to hold it in a constant bank turn at low speed. This requires the pilot either lower the nose or apply opposite rudder to prevent the turn from getting any steeper, both of which will lower the AOA on the inside wing. If the pilot allows the bank to get steeper the airplane runs out of elevator authority and the nose drops on its own increasing the airspeed and also lowering the angle of attack. As is almost always the case moveing the CG back will give the airplane more elevator authority and a better change of being able to stall the inside wing. |
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