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#91
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The behaviour described in a previous message as an "insipient spin" with
the ASH-25 seems to be a very simple early part of a stall. If ailerons are used close to the Stall AOA, they might seem to work in reverse, which is consistent with the description given in that message. This is due to the fact that in the pre-stall, you're already close to the Stall AOA. The lowering Aileron (to pick up the low wing) will produce an increase in the AOA in that part of the low wing, thus exceeding the Stall AOA and essencially stalling that part (where the aileron is) of the low wing. In other words : Pre-stall, left wing is low (for instance), right aileron will stall the left wing tip thus increasing the bank angle and going to a spiral, an apparent control reversal, easily corrected by : The correct control input, which is to apply right rudder to pick it up, and move the stick forward enough the reduce AOA. This is the reason why instructors teach all students to pick up a low wing during pre-stall by using Rudder (opposite rudder, for that matter), and not by using coordinated controls as it is suggested, because the aileron will work against the intended recovery. Even if the glider wing was designed with some twist to lower the AOI at the wingtips, they will still suffer from this reverse effect when in a pre-stall condition. All existing airplane and glider literature clearly recomends picking up a low wing with opposite rudder during pre-stall, along with lowering the nose. I have never seen a manual suggesting to pick up a low wing at the pre-stall with "coordinated controls", it would surprise me very much if the ASH-25 suggested something like that. What it may be suggesting is that you always use coordinated controls (the correct use) while thermalling, and if you sense the glider in a pre-stall condition, lower the nose slightly and use coordinated controls to continue the turn. I wrote about this before : While thermalling, if you feel an inpending stall, it may not be necessary to "dive like mad" to recover. It may be a simple case of lowering the nose only slightly and maybe applying some opposite rudder for a few seconds. If you do it calmly, other gliders in the same thermal won't even notice that you were about to stall. Again, any experienced instructor can demonstrate this. Happy flying. "Chris OCallaghan" wrote in message om... I've noted that many 25s have wing extended wing tips, some factory, some home built. The vertical stab was designed to some theoritical maximum... This would be yet another aggrevating factor. What fascinates me about these reports is the effect in the real world of the designer's tradeoff between stability and controlability. Bigger vertical stabs would reduce the likelihood of a spin, but at the cost of much drag. Less drag is better, but you don't want a sailplane so unstable that moderate turbulence can flick it into a spin from a low speed turn. So if you want to give it a good low speed roll rate, you have to depend on the pilot's proper use of the powerful rudder he'll need to counteract adverse yaw. But pilots are people, and we all make mistakes. So the conscientious designer must needs put enough surface area back there to prevent autorotation so long as the pilot neutralizes the controls at the first indication of an insipient stall. Even if the stall progesses, so long as the controls aren't crossed, it shouldn't lead to a spin. Little modern gliders seem to reflect this philosophy. As bigger gliders become more popular among lower time pilots, shouldn't we be examining their characteristics more carefully? While manuals give very precise instructions on how to recover from a fully developed spin, they recommend coordinated use of ailerons and rudder (accompanied by a forward motion of the stick) to pick up a dropping wing during the initial phase of a stall, straight ahead or turning. In other words, the designer is recommending picking up the low wing so long as it is accompanied by a "firm easing of the control stick forward." This procedure is recommended because it results in the minimum loss of height. We were all taught, thouigh, that if the wing begins drop during a stall, we neutralize the ailerons, ease the stick forward, and kick opposite rudder. Given the number (I counted 4) of over the top spin entries noted in another thread, I wonder if we haven't been to aggressive in preventing the "insipient spin" with spin recovery control motions. And as a result, misinterpret any yawing of the nose during a stall to be the preamble to a spin. I'm splitting hairs. And it's certainly not the stuff for students to be pondering. They need a one size fits all recovery. But I'm genuinely interested in just what is going on at the stall and immediately after, and if our perceptions haven't been altered by the necessity of the shortcuts we take during training to get us quickly to the point where we can go teach urselves. Robert Ehrlich wrote in message ... Chris OCallaghan wrote: This is an interesting case. I haven't really thought this through since stalling is difficult in most properly balanced sailplanes at high angles of bank. A long wingspan adds yet another aggrevator. But your speed is higher in a steep turn, thus the vertical stabilizer is more efficient. And right off hand I can think of several outcomes that would look like spins, but are, in fact, something else. Think of a wing over, for example. If you shot the initial 90 degrees of turn after apex, it would look very much like a spin entry. Nonetheless, I haven't tried a stall from a coordinated steep turn, with controls crossed and the yaw string straight. And I won't have a chance for another month or so... Perhaps, for the time being, I need to ammend my position to say that a spin is unlikely in most sailplanes if the ailerons and rudder are neutralized. In the meantime, if you have a chance to repeat, see if the instructor will let the "spin" develop. I'm interested to see if it is really a spin (I think the chances are good, though, if the controls stay crossed). Try it again, but at entry, center the ailerons and rudder, but leave the stick back. That is, add no further aggrevation after the stall break and see what it does. By the way, how rapid was the autorotation at stall break? How much change in direction did you experience before rolling back to level? How much altitude did you lose, if you took notice? And was there anything unusual about this particular 25? There was nothing unusual about this 25, only about myself. It was my first flight in the ship, I had a very low experience at this time ( 100 hours) and had only flown ASK21 and ASK23. This happened twice in the day at a low bank angle. There was almost no autorotation or change in direction. It was rather the feeling that increasing outside stick could no more counter the overbanking tendancy, but rather increased it, that made me realize that the inner wing was stalled and the I had to quickly release back pressure to avoid some mess, so nothing wrong happened before immediate recovery. My propension to low speed flight came from my familiarity with the ASK23 whose wing loading is much lower, and from the fact that it was a weak day where low speed rather than high bank angles helps to remain close to the core of thermals, at least in the ASK23 I was usually flying. It was my first attempt to make a flight longer than 5 hours, I felt it was better to try it first with an instructor behind me and in a glider in which this may be achieved even in unfavorable weather. This last point turned out to be true, all other gliders were in the hangars when we landed at the end of the day and the duration was effectively over 5 hours. However I had to wait another season before getting my silver duration, but this is another story. BTW I cannot try what you suggest since this 25 is no more in my club, nor any other club 25 (but 2 private ones) and the instructor in such a repeat attempt would probably be myself as I got this rating during last September. |
#92
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At 09:48 31 January 2004, Arnold Pieper wrote:
The correct control input, which is to apply right rudder to pick it up, move stick forward enough the reduce AOA. Sorry to pull one part of your story out for comment. Some years ago the British Gliding Association dropped the term incipient spin and called this 'Stall With With Wing Drop'. Most older instructors and pilots were taught as you decribed to pick up the dropping wing with rudder. The current BGA instructors manual states:-) 'When a wing drops at the stall it is essential to unstall the glider before attempting to level the wings. Once the glider is unstalled, level the wings with coordinated ailerons and rudder.' Section 18 page 2 In the demonstration and practice section page 18.4. The instructor is told 'Emphasise the wings are levelled with coordinated use of ailerons and rudder, BUT ONLY AFTER the glider is unstalled.' Spinning is merely the natural consequence of failure to understand and/or recognise the onset of the problems caused by flying at or close to the stalling speed. It is for this reason that students should be taught both in theory and practice the stall symptoms and the BGA further stalling exercises. Together with the dangers of flying at of close to the stall speed in any phase of their flight. I agree that in many cases merely relaxing the back pressure on the stick to regain flying speed can prevent the onset of stalling the wing and it consequences. Dave |
#93
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![]() U=BFytkownik Bill Daniels w wiadomooci do grup = dyskusyjnych ... =20 It does make one wonder. I seem to recall something on r.a.s. to the = effect that an inspection of a Puch in the USA turned up a metal plate that = was adrift somewhere in the rudder control curcuit. This loose plate, it = was said, could prevent the rudder from moving back from the fully = deflected position. I seem to recall that it was suspected that some of the = spin-in accidents might be due to this. One day I was told about a Puchacz accident at Bielsko in southern = Poland, many years ago. The trim handle (a small green ball made of = fabric) went loose and disappeared. The student replaced it with another = one, but didn't check where's the one which got lost, and then took off = for a spin training... The ball has been left inside, and it managed to get into controls, and = in the moment they were in spin and tried to move stick forward to get = out of the spin, it locked itself preventing the stick from moving = forward. The student with instructor kept on pushing the stick, and = finally hit the ground killing themselves. Finally it became clear that if they had moved stick back for a second, = they could survive, because thic could loosen the ball... I just wonder how the student stupid had to be to not check the glider = throughly after noticing that the handle has gone. Regards, --=20 Janusz Kesik visit www.leszno.pl - home of the www.css-leszno.it.pl |
#94
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![]() U=BFytkownik Chris OCallaghan w wiadomooci do = grup dyskusyjnych = gle.com... My understanding is that the Puchaz became popular only for its spin characteristics.=20 Not only, it's just a very good trainer. It's easy to put into a spin throughout its cg range. Because it was designed for that. --=20 Janusz Kesik visit www.leszno.pl - home of the www.css-leszno.it.pl |
#95
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![]() "Janusz Kesik" wrote in message ... I just wonder how the student stupid had to be to not check the glider throughly after noticing that the handle has gone. Three thoughts: 1) I find it courious that the student was doing maintence work on the glider. and... 2) In exactly the same situation, I wonder if I would have been sufficiently courious to check all of the deep-dark spaces in the belly of the glider. Frankly, I am afraid of the answer. Perhaps that is why we let A&P's do that sort of thing? and... 3) In many gliders it is very difficult to inspect under the floorboards and back in the tailcone, yet you never really know what may be lurking there, tools, lost cellphones, critters, etc. I once saw a good-sized snake bail out of a glider just as it was landing and then slink off quickly, apparently none the worse for the experience. It was not the first flight of the day for that ship. Regards, Vaughn -- Janusz Kesik visit www.leszno.pl - home of the www.css-leszno.it.pl |
#96
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I see Dave.
I'm courious now : When you're teaching Stalls and a wing is low just before the stall, you don't pick it up until AFTER the stall ? This is not the way it's done in both countries where I fly. "Dave Martin" wrote in message ... At 09:48 31 January 2004, Arnold Pieper wrote: The correct control input, which is to apply right rudder to pick it up, move stick forward enough the reduce AOA. Sorry to pull one part of your story out for comment. Some years ago the British Gliding Association dropped the term incipient spin and called this 'Stall With With Wing Drop'. Most older instructors and pilots were taught as you decribed to pick up the dropping wing with rudder. The current BGA instructors manual states:-) 'When a wing drops at the stall it is essential to unstall the glider before attempting to level the wings. Once the glider is unstalled, level the wings with coordinated ailerons and rudder.' Section 18 page 2 In the demonstration and practice section page 18.4. The instructor is told 'Emphasise the wings are levelled with coordinated use of ailerons and rudder, BUT ONLY AFTER the glider is unstalled.' Spinning is merely the natural consequence of failure to understand and/or recognise the onset of the problems caused by flying at or close to the stalling speed. It is for this reason that students should be taught both in theory and practice the stall symptoms and the BGA further stalling exercises. Together with the dangers of flying at of close to the stall speed in any phase of their flight. I agree that in many cases merely relaxing the back pressure on the stick to regain flying speed can prevent the onset of stalling the wing and it consequences. Dave |
#97
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On Thu, 29 Jan 2004 00:07:35 UTC, Eric Greenwell
wrote: : Ian Johnston wrote: : Personally, I think the tail ends of single seaters sticking out of : fields and hill sides makes a pretty good attack on that position. : : Do these accidents show an inability to: 1) recover from full spins, 2) : from incipient spins, 3) detect the signs of an impending (but not yet : incipient) spin, 4) avoid spin precursors entirely? 5) Take spins seriously as a threat. Ian |
#98
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On Sat, 31 Jan 2004 14:46:10 +0100, "Janusz Kesik"
wrote: I just wonder how the student stupid had to be to not check the glider throughly after noticing that the handle has gone. I wonder if he thought to tell anybody else about the missing knob. -- martin@ : Martin Gregorie gregorie : Harlow, UK demon : co : Zappa fan & glider pilot uk : |
#99
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At 19:00 31 January 2004, Arnold Pieper wrote:
I see Dave. I'm courious now : When you're teaching Stalls and a wing is low just before the stall, you don't pick it up until AFTER the stall ? This is not the way it's done in both countries where I fly. Arnold Effectively Yes, and it works. Rather than me try to explain my thoughts and experience the manual explains the logic quite neatly (18.6) 'Whilst use of the rudder to prevent yaw in the direction of the down-going wing is a counsel of perfection, it must be realised that the pilot caused the inadvertent stall in the first place by inappropriate use of the controls. He is unlikely to start making skilful or precise movements now. Do not attempt to use the secondary effect of the rudder to restore the wings to the level position. This would introduce yaw which could result in the glider spinning. The priority must be to unstall the glider by moving the stick forward.' There are further spinning exercises including a demonstration of the changing effect of the rudder at the stall to emphases this point. Dave |
#100
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![]() U=BFytkownik Martin Gregorie w wiadomooci = do grup dyskusyjnych = om... I wonder if he thought to tell anybody else about the missing knob. Could be... JK |
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