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#101
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Lower, but not low. You can carry the same total energy
throughout the pattern. 9B At 05:06 30 August 2004, Eric Greenwell wrote: I can see how the 'fast' part can help, but not the 'low' part. Being low doesn't seem like an asset if you are worried about stalls and spins. |
#102
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With the big spoilers on modern gliders, there's not much risk in
adding 10 extra knots, and while your argument that it adds an increased cushion before stall is unarguable, I guess the measure of value comes in whether that reduced risk is a justified departure from the "correct" pattern airspeed. I'm with Mark... it deserves some more discussion. BTW, as I noted in another thread, spins are not caused by lack of airspeed, but uncoordinated use of the controls -- at least in modern sailplanes. Two things must happen to enter a spin: 1) you must stall, and 2) you must fail to apply sufficient rudder during your attempt to pick up the low wing with aileron. That is, the sailplane is designed with enough rudder to stop autorotation, even with full deflection of the aileron throughout the stall break. As demonstrated by my thread last fall, a Ventus 2 won't spin if the controls remain coordinated (half stick/half rudder... full stick/rudder). It enters a controlable spiral, instead. However, half rudder and full stick (or half stick and no rudder) would induce a spin if the stick is held full back throughout the stall break. Avoiding the stall is the first most important step, but thorough training of the appropriate response during an inadvertent stall is a close, close second. And I could even argue that it's more important, since once you've stalled by accident, the outcome is determined by how well you've been trained to recover (that is, it becomes the failsafe for your stall avoidance error). Though I'm not a fan of axiomatic training, there's some value in remembering that you can stall at any attitude and any speed. If you wear that axiom on your sleeve, then you'd be best served by understanding and practicing superlative stall recovery technique in addition to practicing stall avoidance. That so many capable pilots have stall/spun in relatively docile aircraft indicates to me that there is a training gap. We are clearly handling the controls diffently at low altitudes. Why? If we can agree that this is the case, then adding speed is good insurance. But it doesn't address the cause. Andy, apologies for being the pedant. I'm spitting this stuff out at 60 words per minute, so I'm not giving much thought to "balance." |
#103
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"Ian Johnston" wrote in message news:cCUlhtvFIYkV-pn2-BdEMqrRprN20@localhost...
On Fri, 27 Aug 2004 18:02:44 UTC, (Kirk Stant) wrote: : But you : shouldn't be jerking your head around while flying! Except to scan for other aircraft. Ian It's tough to see other aircraft by rapidly moving your head - you need to stop and methodically scan areas of the sky. No disagreement about the need to keep looking around at all times. But scanning, like just about everything else in flying, is a skill that needs to be taught, learned, and practiced to be effective. Kirk |
#105
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#106
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Bruce Hoult wrote:
In article , Robert Ehrlich wrote: Well, I disagree, and I strongly believe that a well-trained glider pilot, in any glider, low or high, should be every bit as comfortable and safe (if not more so) in a 50 degree bank as in a 20 degree bank. Marc Agreed for feeling safe, but when comfortable is the question, I think most pilots would find 1.02g is much more comfortable than 1.75g. That's 1.06 vs 1.56, actually. I agree, some mistyping probably in my previous calculation. |
#107
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Chris OCallaghan wrote:
BTW, as I noted in another thread, spins are not caused by lack of airspeed, but uncoordinated use of the controls -- at least in modern sailplanes. Two things must happen to enter a spin: 1) you must stall, and 2) you must fail to apply sufficient rudder during your attempt to pick up the low wing with aileron. That is, the sailplane is designed with enough rudder to stop autorotation, even with full deflection of the aileron throughout the stall break. Well, you have to precise what you are calling "uncoordinated use". I remember an incipient spin in an ASH25 (can be considered as a modern sailplane, although it existed well before I started gliding 9 years ago). My mistake was only a to high nose up attitude while circling, which was not obvious to me as it was my first flight in the aircraft (with an instructor of course). Due to its high inertia, the sailplane was slowing down very slowly to the speed corresponding to its attitude, and needed while slowing down more and more action on controls to counter induced roll and induced bank up to the point where I had almost full out stick and a lot of inner rudder when the inner wing dropped. Of course the controls were badly crossed, but some amount of cross control is normal in order to counter induced roll and induced yaw, this is not an uncoordinated flight, the yaw string is is the middle. The excess in cross control was due to the fact that both induced effects increase when speed decrease, not to a lack of coordination. Another experience I had, which is also in contradiction with this opinion (i.e. spin can only occur by lack of coordination) was when I was preparing my instructor rating. As there was no other spinable glider available, we had to demonstrate spin entry and recovery in a Fox, an aerobatic glider. My instructor was Katona, a well known aerobatic pilot, and he explained that in order to spin this glider I should slow it down just very close to the stall and then have stick and rudder to the same side. I objected that I had always be taught to push the rudder to the side I want to spin ans the stick to the opposite side. He said that in this case the Fox would do a flat spin, which is difficult to exit and was not the objective of the present exercise. |
#108
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"Ian Johnston" wrote in message news:cCUlhtvFIYkV-pn2-8OXf57VN35wC@localhost...
On Fri, 27 Aug 2004 21:38:02 UTC, (Mark James Boyd) wrote: : "Oh yeah? He had an accident? I bet he : didn't use the checklist!" I once had someone try to persuade me to use a checklist for a winch cable break. Yes, great, run through a list of actions which have to be started within a second and completed within a few ... the idiot's an instructor now, and feedback tells me that he's no less of an idiot... I recently read the accident report of the ASW20 crash (fatal) at Williams, CA. Per the check list, they did a positive control check of the elevator by having the assistant (co-owner) hold the elevator while the pilot applied force on the stick. Resistance was felt, check list passed. Only problem was the elevator was not hooked up and what the pilot felt was the push rod hitting the bottom of the elevator. Now, if the guy just LOOKED at the connection it would have been obvious that it was not hooked up (it is in plain site). Still, he had a second chance to save himself. When the glider decided to launch itself he could have immediately released and delt with the situation at a more survivable attitude (the tow pilot released him instead). Check lists are not substitutes for plain common sense. If you use them, do another walk around the glider without the list, looking for things you might have missed. Following a list may give you tunnel vision. A DC-9 was landed gear up by two experienced pilots following a check list (they missed one step). They were so certain that they had done everything right that they ignored the lack of the sound and thump of the gear lowering (common sense, again). Tom |
#109
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Chris - always thoughtful and articulate - even when
pedantic. ;-) Seriously, I agree with your point about avoidance AND early, reflexive recovery to avoid a full-on spin. I used to work on wing-drop recovery in an early S/N Ventus A/16.6 - which had the most pronounced stall break of any glider I can recall. The control input was stick forward and into the turn plus top rudder. It takes some practice to make it reflexive. I recall the main reasons for teaching stabilized approach are to provide a consistent visual reference for the pilot and to keep from changing too many flight variables at the same time. Honestly, I don't know how they come up with recommended 'correct' pattern speeds - nor how scientific or precise the algorithm. My assumption is that the speed is picked as a tradeoff between stall margin and approach energy - but that there is an acceptable range. We regularly add 1/2 the wind speed - how exact is that? My personal experience is that it's quite easy to bleed off 5-10 knots by accident in a moment of distraction, but 15-20 knots takes longer and is more apparent. 9B At 15:36 30 August 2004, Chris Ocallaghan wrote: With the big spoilers on modern gliders, there's not much risk in adding 10 extra knots, and while your argument that it adds an increased cushion before stall is unarguable, I guess the measure of value comes in whether that reduced risk is a justified departure from the 'correct' pattern airspeed. I'm with Mark... it deserves some more discussion. BTW, as I noted in another thread, spins are not caused by lack of airspeed, but uncoordinated use of the controls -- at least in modern sailplanes. Two things must happen to enter a spin: 1) you must stall, and 2) you must fail to apply sufficient rudder during your attempt to pick up the low wing with aileron. That is, the sailplane is designed with enough rudder to stop autorotation, even with full deflection of the aileron throughout the stall break. As demonstrated by my thread last fall, a Ventus 2 won't spin if the controls remain coordinated (half stick/half rudder... full stick/rudder). It enters a controlable spiral, instead. However, half rudder and full stick (or half stick and no rudder) would induce a spin if the stick is held full back throughout the stall break. Avoiding the stall is the first most important step, but thorough training of the appropriate response during an inadvertent stall is a close, close second. And I could even argue that it's more important, since once you've stalled by accident, the outcome is determined by how well you've been trained to recover (that is, it becomes the failsafe for your stall avoidance error). Though I'm not a fan of axiomatic training, there's some value in remembering that you can stall at any attitude and any speed. If you wear that axiom on your sleeve, then you'd be best served by understanding and practicing superlative stall recovery technique in addition to practicing stall avoidance. That so many capable pilots have stall/spun in relatively docile aircraft indicates to me that there is a training gap. We are clearly handling the controls diffently at low altitudes. Why? If we can agree that this is the case, then adding speed is good insurance. But it doesn't address the cause. Andy, apologies for being the pedant. I'm spitting this stuff out at 60 words per minute, so I'm not giving much thought to 'balance.' |
#110
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Knowing your glider is the key. Open class ships are built to the
limits of acceptable flying characteristics, as is the case with aerobatic aircraft (one reason they are typically certified "experimental"). You must read and understand the flight manual, noting the divergence from the norm, which is what I cited in this and previous threads. I suspect that many pilots are simply not used to the difference in force required to displace the rudder equally with the aileron. A tendency to underrudder at flying speed is common. Applying the same "balance" near the stall would produce much less rudder force, which means that the greatly increased and unbalanced aileron drag will produce a skid, and the angular momentum required to start autorotation. Flying your glider at MCA and experimenting with various displacements of the controls is a good exercise. Gentle turning stalls while using coordinated aileron and rudder (not solely determined by the yaw string but also by percentage of travel applied) to pick up the lower wing will help you understand what your glider can and cannot do in the stall. In previous threads, we discussed intentionally spinning at pattern altitudes to acclimate pilots to this "view." Such practices are patently absurd. However, regular practice flying on the edge of the stall while applying coordinated aileron and rudder should have real (and much more valuable) benefits. Does your yaw string act differntly at low speed? Are you able to accurately judge onset of the stall? During a stall, are you applying sufficient rudder? We all make assumptions that we will react correctly, but I'd guess that without regular practice of the type I descibed above, we're probably not flying as efficiently near the stall as we think. So if we get there by accident, is it possible that we might not be aggrevating the situation through improper control inputs? BTW, recall that during my test flights, I was able to avoid a spin while holding full back stick throughout the stall and ensuing spiral. Simultaneous release of back pressure and coordinated use of aileron and rudder is the key. Flying MCA and reacting this way to any sign of an impending stall is the best training you can give yourself. Then add 15 knots in the pattern to be sure you won't have to exercise those skills. Honestly, how many of you really practice stall recognition and recovery as a regular flight proficiency routine? I typically only fly on the cusp of a stall for several seconds each flight: as I take off (I get impatient) and just before I touch down. That's not a whole lot of opportunity to experience a critically important flight regime. Over my quota for the week. I'll check in next week. OC Robert Ehrlich wrote in message ... Chris OCallaghan wrote: BTW, as I noted in another thread, spins are not caused by lack of airspeed, but uncoordinated use of the controls -- at least in modern sailplanes. Two things must happen to enter a spin: 1) you must stall, and 2) you must fail to apply sufficient rudder during your attempt to pick up the low wing with aileron. That is, the sailplane is designed with enough rudder to stop autorotation, even with full deflection of the aileron throughout the stall break. Well, you have to precise what you are calling "uncoordinated use". I remember an incipient spin in an ASH25 (can be considered as a modern sailplane, although it existed well before I started gliding 9 years ago). My mistake was only a to high nose up attitude while circling, which was not obvious to me as it was my first flight in the aircraft (with an instructor of course). Due to its high inertia, the sailplane was slowing down very slowly to the speed corresponding to its attitude, and needed while slowing down more and more action on controls to counter induced roll and induced bank up to the point where I had almost full out stick and a lot of inner rudder when the inner wing dropped. Of course the controls were badly crossed, but some amount of cross control is normal in order to counter induced roll and induced yaw, this is not an uncoordinated flight, the yaw string is is the middle. The excess in cross control was due to the fact that both induced effects increase when speed decrease, not to a lack of coordination. Another experience I had, which is also in contradiction with this opinion (i.e. spin can only occur by lack of coordination) was when I was preparing my instructor rating. As there was no other spinable glider available, we had to demonstrate spin entry and recovery in a Fox, an aerobatic glider. My instructor was Katona, a well known aerobatic pilot, and he explained that in order to spin this glider I should slow it down just very close to the stall and then have stick and rudder to the same side. I objected that I had always be taught to push the rudder to the side I want to spin ans the stick to the opposite side. He said that in this case the Fox would do a flat spin, which is difficult to exit and was not the objective of the present exercise. |
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