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#11
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AoA keep it going!
On Dec 17, 12:37 pm, "Bill Daniels" bildan@comcast-dot-net wrote:
"Eric Greenwell" wrote in message news:UCz9j.4239$Xh1.3090@trndny03... Bill Daniels wrote: Maneuvering for landing in gusty wind shear is exactly where I'd want an AOA. It will show the maximum gust induced AOA so the airspeed can be increased just enough that no gust stalls the glider but not so much that you'll need to dump a lot of energy in ground effect. Bill, have you used an AOA indicator in the conditions you describe? What one was it? And how did you know the "maximum gust induced" AOA it showed you was the maximum you were going to encounter before landing? Yes, Eric. I've flown with very high quality instruments in airplanes and jury-rigged "pitch strings" in gliders. The pitch strings don't work as well as the expensive units but, aside from the hassle, they are nonetheless very useful. There's no big mystry about AOA indicators, they go back to the very beginnings of aviation. They aren't common because of cost and difficulty implementing them on small airplanes. Until now, nobody gave much thought to gliders. Just look at the jitter or swing in the needle/string. The max swing in the positive direction is the max gust induced AOA. By the time you have flown the pattern and are on short final, you should have a pretty good idea about the level of turbulence you are dealing with and have selected a minimum safe margin for the "over the fence" airspeed. I've seen pilots who have no real knowledge of just what their gust-stall margin is so they keep adding airspeed until it's a problem for them on roll out. It does no good to have a wide margin over stall in the air only to hit a fence on rollout. Just standing on the ground watching glider landings shows a wide range of techniques. Some patterns look like a ground attack fighter rolling in on a target. Others float around the pattern tail low. I have to believe if they had an AOA indicator, they be more consistent - or at least, have rational excuses. In off field landings especially, it's a balance between stall margin in the air and rollout distance on the ground. I practice a short landing on every flight - partly to be ready for a possible off field landing and partly because my trailer is near the approach end and I hate pushing back. I'd love to have a quality AOA indicator to make those landings easier and safer. Bill Daniels This is a life saving discussion and the best I've heard or read. Most, or too many instructors do not know how to teach the subject. Most cannot tell you why "relative wind" exists,. much less how to anticipate the maximum aoa. Airfoils are much more forgiving now, but there is a video of a DG spinning in on final. It's late now and I don't have the link. The ship that spun in on my field in 68, ended with bones sticking out and no bleeding. Some of the pieces are still there to remind skepticks. Bless all of you that care .Fred |
#12
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AoA keep it going!
Bill Daniels wrote:
I'd love to have a quality AOA indicator to make those landings easier and safer. What did you think of this idea from my post: I suggest 5 to 10 proponents of AOA meters, and other interested pilots, buy some AOA meters (like from Safeflight, DG , Aircraft Spruce) as a group. This will reduce the cost for each pilot to try several AOA meters. Have each member of the group try each of the meter(s) for while, then report their experiences. Someone has to try some these devices in gliders, so we have some data that applies to our sport. As the primary promoter of the value of an AOA gauge, you seem to be the obvious choice to lead an effort that proves the value. At that point, a few of the clever people in the sport will likely develop units more suited to gliders, and maybe bring the cost down. There are units available, but I don't see anyone buying and using them. That suggests to me that, while we all agree it's probably a good idea, we don't think it's good enough to spend the $500-$2000 to actually buy and install one. So, someone has to just do it and show the results to us. -- Eric Greenwell - Washington State, USA * Change "netto" to "net" to email me directly * "Transponders in Sailplanes" http://tinyurl.com/y739x4 * "A Guide to Self-launching Sailplane Operation" at www.motorglider.org |
#13
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AoA keep it going!
On 17 Dec, 20:37, "Bill Daniels" bildan@comcast-dot-net wrote:
I'd love to have a quality AOA indicator to make those landings easier and safer. I generally find that my attention is fully occupied while landing. If I had an AoA indicator, I would have to take attention away from something else to look at it (I always have the audio vario and radio off for the final approach). Would an AoA also indicator free up some of my attention, and if so, from what? Ian |
#14
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AoA keep it going!
I generally find that my attention is fully occupied while landing. If
I had an AoA indicator, I would have to take attention away from something else to look at it (I always have the audio vario and radio off for the final approach). Would an AoA also indicator free up some of my attention, and if so, from what? Ian Ian, do you look at your airspeed indicator while landing (well, during the approach, of course - no one looks at their airspeed while actually landing, do they?)? If you do, then a properly designed AoA indicator could make your approaches easier and safer. Remember, airspeed is just an inaccurate way to show angle of attack - the AoA gauge shows it directly. Now, if all gliders had AoA gauges, you could jump from one glider to another and not worry about what the right approach speed is for the glider you happen to be in. Ditto min sink, etc. Sure would be nice with ballasted two-seaters, that can have a significant difference in approach and thermalling speeds depending on crew and ballast weight. Right now, the closest we have is the yellow triangle on german gliders - approach speed at max gross, I think? (please correct me if I'm wrong on that one). Still dreaming... Kirk 66 |
#15
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AoA keep it going!
On Dec 19, 2:38 pm, "kirk.stant" wrote:
I generally find that my attention is fully occupied while landing. If I had an AoA indicator, I would have to take attention away from something else to look at it (I always have the audio vario and radio off for the final approach). Would an AoA also indicator free up some of my attention, and if so, from what? Ian Ian, do you look at your airspeed indicator while landing (well, during the approach, of course - no one looks at their airspeed while actually landing, do they?)? If you do, then a properly designed AoA indicator could make your approaches easier and safer. Remember, airspeed is just an inaccurate way to show angle of attack - the AoA gauge shows it directly. Why might an AoA guage be any more accurate than an ASI? Now, if all gliders had AoA gauges, you could jump from one glider to another and not worry about what the right approach speed is for the glider you happen to be in. But you might be concered about what the correct AoA was for them? Right now, the closest we have is the yellow triangle on german gliders - approach speed at max gross, I think? (please correct me if I'm wrong on that one). *minimum* suggested approach speed. Assuming the dial is marked correctly. |
#16
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AoA keep it going!
kirk.stant wrote:
Now, if all gliders had AoA gauges, you could jump from one glider to another and not worry about what the right approach speed is for the glider you happen to be in. Whatever happened to the old fashioned custom to familiarize oneself with the particularities of a glider before flying it? Right now, the closest we have is the yellow triangle on german gliders - approach speed at max gross, I think? (please correct me if I'm wrong on that one). Nothing to do with German, it's a JAR requirement. Suggested minimal approach speed at max gross without water ballast. The triangle is handy, but just reading the POH works, too. |
#17
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AoA keep it going!
On Dec 19, 12:22 pm, John Smith wrote:
kirk.stant wrote: Now, if all gliders had AoA gauges, you could jump from one glider to another and not worry about what the right approach speed is for the glider you happen to be in. Whatever happened to the old fashioned custom to familiarize oneself with the particularities of a glider before flying it? That's a great custom, which I wholeheartedly endorse. Now, put yourself in the postion to jump into a variety of gliders in rapid succession. You are current and qualified in all of them, of course. But can you instantly recall the exact speeds for all of them, under pressure, without fail? My personal experience was in giving commercial rides (sightseeing and aerobatic) in 2-33s, 2-32s, G-103s, and ASK-21s. With a wide variety of passenger size, in no particular order, often moving to a different glider immediately after landing. Fortunately, one soon learns the individual characteristics of the gliders one flies frequently, and on a nice big field, a little extra airspeed doesn't hurt until you slow down in the flare. So TLAR works surprisingly well. But it would still be nice to have ACCURATE instrumentation. While airspeed works, it is by design only an approximation of the correct speed. We are lucky that most gliders are so forgiving that this is mainly an academic argument. Now, get slow on your turn to final in a 2-32 and you may wish you had an AoA indicator! Right now, the closest we have is the yellow triangle on german gliders - approach speed at max gross, I think? (please correct me if I'm wrong on that one). Nothing to do with German, it's a JAR requirement. Suggested minimal approach speed at max gross without water ballast. The triangle is handy, but just reading the POH works, too. Absolutely correct. I find that I don't use it in my own ship, but look for it when I get in a club ship that I havn't flown in a while - as a starting point for pattern speed. Kirk |
#18
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AoA keep it going!
kirk.stant wrote:
That's a great custom, which I wholeheartedly endorse. Now, put yourself in the postion to jump into a variety of gliders in rapid succession. You are current and qualified in all of them, of course. But can you instantly recall the exact speeds for all of them, under pressure, without fail? Yes. But if I really couldn't and were in the situation you describe, I just would write them into a little booklet which I could take with me and consult before getting into the glider. Just as I do with many other things. (Besides: If you can't remember the exact speeds to fly, why should you be able to remember the exact AoA to fly?) My personal experience was in giving commercial rides (sightseeing and aerobatic) in 2-33s, 2-32s, G-103s, and ASK-21s. With a wide variety of passenger size, in no particular order, often moving to a different glider immediately after landing. I shudder at the thought that a pilot would give commercial rides to passengers without being absolutely sure of the exact speeds to fly! But it would still be nice to have ACCURATE instrumentation. While airspeed works, it is by design only an approximation of the correct speed. It may not be ACCURATE, but it certainly is accurate enough. For me, anyway. Now, get slow on your turn to final in a 2-32 and you may wish you had an AoA indicator! The solution is simple: Just don't get slow on your turn to final. This has been hammered into my head since my very first flight, and it works for me. I don't see what an AoA instrument could add to this. If you are distracted enough to get slow with an ASI, then I see no reason why you wouldn't be distracted enough to get slow with an AoAI. |
#19
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AoA keep it going!
On Dec 19, 3:43 pm, John Smith wrote:
....snip... for me. I don't see what an AoA instrument could add to this. If you are distracted enough to get slow with an ASI, then I see no reason why you wouldn't be distracted enough to get slow with an AoAI. This seems to be the real reason people stall. It's not that they don't know what the speed is, it's that they can't maintain the speed that they do know ! Todd Smith 3S |
#20
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AoA keep it going!
toad wrote:
On Dec 19, 3:43 pm, John Smith wrote: ...snip... for me. I don't see what an AoA instrument could add to this. If you are distracted enough to get slow with an ASI, then I see no reason why you wouldn't be distracted enough to get slow with an AoAI. This seems to be the real reason people stall. It's not that they don't know what the speed is, it's that they can't maintain the speed that they do know ! An indicator for an AoA meter could consist of something as simple as three LEDs, say a bright red one for approaching stall, green for minimum sink, blue for best L/D and above, with the red LED blinking faster as AoA gets closer to stall. The LEDs could be mounted on a short stick above the instrument glare shield, or even attached to sunglasses such that it would always be at the edge of the field of view. All the interpretation required is that the bright flashing red light means get the nose down, right now. No one has said anything about taking away anyones ASI... Marc |
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