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#21
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This is exactly how I learned to fly hang gliders. I mostly use my ears, but the bar pressure is also important. It also helps to have a helmet with earholes in it - you can sometimes hear which side the thermal is on. An important difference between planes & hang gliders is that the trim is always set at the same speed, so you can tell if you're at min sink or best glide using bar pressure. |
#22
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Angle of attack
Eric Greenwell wrote:
The big problem is AOA is an abstract engineering parameter, because pilots can't see it, can't hear it, and can't feel it. We can see attitude and airpeed... The only airspeed I've ever "seen" in a glider was indicated on the face of the mechanical ASI--a rather remote approximation--and as a sole indication of stalling speed can be hugely misleading. AOA, within the limitations of the instrument and the installation, is never wrong--no matter the speed, g-loading, or aircraft weight. ...we can hear airspeed and stall rumble, and we can feel stick position and stick forces, so that is what we use to fly by. I sure don't think about AOA when I'm flying. You would if you had an AOA to think about. In its absence you have learned to substitute those other vague indications, some of which are present in some situations but not in others, and some of which, though present, are of little use in any but the narrowest of circumstances. Don't knock AOA until you've used it. Until we can hear it, see it, or feel it, we won't be able to use [it]. And until you use it, you won't be able to hear, see, or feel it. It's basically the difference between a (ASI) love letter and a (AOA) caress. I know which I prefer, especially when time is of the essence--which it is anytime an object is in motion. Jack |
#23
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Angle of attack
toad wrote:
While I agree that understanding of AOA is crucial for a pilot. I don't think that a AOA indicator would be very useful in gliders Why would the best reference for the actual performance of the aircraft be less desirable than an error-prone and very approximate indication which, like a stopped clock, is exactly right about twice a day? I think that stall accidents are caused by lack of awareness and lack of attention. Letting the airspeed "creep away" and incorrectly responding to the loss of airspeed. Substituting an AOA dial for the airspeed dial, won't change that. It is my understanding that one is supposed to be able to fly a glider safely without reference to the ASI, and I suppose that should also then apply to AOA as well. Obviously, not everyone can do so. And there are a few each year that manage to demonstrate the inability to fly safely in spite of the availability of a working ASI. It is also possible that the fact that the stall speed of a given sailplane on a given flight could be +/- 15%, or more, from book speed _in one-g flight_ should be given more thorough consideration. Do we know then what it might be in a 30-60 degree banked final turn, or in a wind shear condition where the ASI reads considerably below the book stalling speed? "More" is an answer, in one case, and "Less" in the other. How much more or less we find by trial and error, guesswork and luck--or not. An AOA would tell us instantly and throughout the normal operating range of the glider, and beyond, just how close to the stall we are operating. AOA gauges seem best suited for heavy aircraft flown by reference to instruments. Where you might have to wait a couple of minutes after setting the AOA and power lever to get the airspeed to respond. Gliders will change their airspeed much quicker than a 747 or F-14. I can't use the F-14 or the 747 as a reference, because I have not flown either. My understanding is that the F-14 can accelerate rather rapidly and slow down pretty quickly as well. High performance military aircraft which I have flown certainly exhibited that capability. To say that any of them, or even a 747, could not accelerate more rapidly than an unpowered glider in a specified attitude seems an incompletely considered statement, but perhaps you can provide some evidence to support your claim. We also only really fly at 2 or 3 different weights. So we only really have to remember the best L/D speed for these conditions. Be my guest--memorize as many speeds as you like. You'll still be guessing at how close your ASI is to the actual stalling speed at any particular moment. AOA never lies: any g-load; any altitude; any attitude; any airspeed. Jack |
#24
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Angle of attack
J a c k wrote:
Eric Greenwell wrote: The big problem is AOA is an abstract engineering parameter, because pilots can't see it, can't hear it, and can't feel it. We can see attitude and airpeed... The only airspeed I've ever "seen" in a glider was indicated on the face of the mechanical ASI--a rather remote approximation-- The AIS is close enough, except in a slip, because doesn't have to be accurate, just consistent. The flight manual values are based on what it shows, not what the actual airspeed is. and as a sole indication of stalling speed can be hugely misleading. Indeed, and that's why we use other indications in addition. AOA, within the limitations of the instrument and the installation, is never wrong--no matter the speed, g-loading, or aircraft weight. In fact, the AOA instrument on every glider I've owned (six) was always "wrong", because none of them had one. I like the idea, but the reality is I've never had one, so I've never used one. Ditto for most pilots when flying gliders. ...we can hear airspeed and stall rumble, and we can feel stick position and stick forces, so that is what we use to fly by. I sure don't think about AOA when I'm flying. You would if you had an AOA to think about. Well, yeah, but I don't. In its absence you have learned to substitute those other vague indications I never had an AOA indicator, so I didn't learn to "substitute" for it, I learned the vague indications from the very beginning. IF a suitable AOA indicator became available in my glider, I would probably learn to substitute it for the vague indications. Or maybe not - I don't know how much value it would have for my flying until I try it. , some of which are present in some situations but not in others, and some of which, though present, are of little use in any but the narrowest of circumstances. On the contrary, the "vague indications" have served me well for 5000+ hours of flying cross country! Don't knock AOA until you've used it. I have never knocked AOA indicators as a *potentially* useful device. I like the idea. I am skeptical that teaching pilots about AOA will reduce accidents, as Bill suggested, UNLESS we have an AOA indicator for them to look at (or hear/feel). I haven't seen any documentation that AOA will improve safety or performance significantly, just personal opinions that it will, so I am skeptical of enthusiastic claims that it will do so. Until we can hear it, see it, or feel it, we won't be able to use [it]. And until you use it, you won't be able to hear, see, or feel it. It's basically the difference between a (ASI) love letter and a (AOA) caress. I know which I prefer, especially when time is of the essence--which it is anytime an object is in motion. Which one do you use in your glider, and where can I get one for my glider? We need to have units in gliders, in use, before we can make any serious claims about it's effectiveness. It seems like it should help, but so far, the people that have used them were flying jets. Apparently, it's essential in then environment, but jets aren't gliders. so we still don't know. I hope some pilots will try the Safeflight unit and the DG unit (and others I'm not aware of), and report their experiences. If the reports are positive, it might spur further use and lead to improved units, and the best techniques for using them. -- 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 |
#25
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Angle of attack
Be my guest--memorize as many speeds as you like. You'll still be guessing at how close your ASI is to the actual stalling speed at any particular moment. AOA never lies: any g-load; any altitude; any attitude; any airspeed. While I think an AOA indicator might be useful, isn't this over selling it's ability? How about with ice, rain, or bugs on the wing - is the stalling AOA still the same? Does the AOA indicator read correctly in slip? Does it read the AOA of the inboard tip and the outboard tip in a turn? What if it freezes, or gets water it? -- 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 |
#26
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Angle of attack
Sorry Bob,
I can't agree to that. In level flight and coordinated turns, the nose attitude as an absolute reference for the AoA for a given flap setting. Most stall/spin entries happen exactly in this configuration (at least here in Europe, maybe in the US you die differently) when people fly at critical AoA close to the ground and then initiate a turn. On flapped gliders, this happens with the flaps in thermal position, so who cares about the AoA for the other flap positions? Haven't heared of any fatal stall accident where the flaps have been at -10 degree... If a pilot isn't aware that the nose is too high, why the hell would he care what an AoA meter tells him? Bert "Bob Kuykendall" wrote in message ... On Dec 13, 2:16 am, "Bert Willing" bw_no_spam_ple...@tango- whisky.com wrote: ... Nose attitude is the onboard AoA, and it works... Apologies for the dogpile, but I think that's wrong and wrong. I believe that thinking like that is exactly what leads to the types of insidious stall/spin entries that most often become accidents. That's not to say that nose angle isn't a useful tool. In straight-and- level flight, and in stable coordinated turns, nose angle and nose angle rate are key indicators of speed and acceleration. However, straight-and-level flight and stable coordinated turns constitute a very small subset of the available flight regimes, and are among those least likely to offer unanticipated stall spin entries. Also, in flapped ships, and especially in glidepath-flapped ships, nose angle is virtually useless as a speed reference independent of flap deflection. In a good old HP glider, you can have your toes on the horizon and be tearing along at a stable 80 kts. Or you can be going almost straight down at a stable 80 kts and viewing the horizon through the crown of the canopy. So far as soaring and sailplanes go, I'm basically an anti- gadgetarian. For years, the most complicated device in my ship was the digital clock. However, I think that a simple, effective AOA indicator with an intuitive display would be a real asset. And, it would be useful not only for stall/spin protection but also for cruise and thermal optimization. Thanks, Bob K. |
#27
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Angle of attack
Eric Greenwell wrote:
Be my guest--memorize as many speeds as you like. You'll still be guessing at how close your ASI is to the actual stalling speed at any particular moment. AOA never lies: any g-load; any altitude; any attitude; any airspeed. While I think an AOA indicator might be useful, isn't this over selling it's ability? How about with ice, rain, or bugs on the wing - is the stalling AOA still the same? Does the AOA indicator read correctly in slip? Does it read the AOA of the inboard tip and the outboard tip in a turn? What if it freezes, or gets water it? See both Daniels' and Pfeiffer's recent comments in the nearby "AoA Keep it Going" thread. Jack |
#28
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Angle of attack
On Dec 16, 8:06 pm, J a c k wrote:
toad wrote: While I agree that understanding of AOA is crucial for a pilot. I don't think that a AOA indicator would be very useful in gliders Why would the best reference for the actual performance of the aircraft be less desirable than an error-prone and very approximate indication which, like a stopped clock, is exactly right about twice a day? I think that stall accidents are caused by lack of awareness and lack of attention. Letting the airspeed "creep away" and incorrectly responding to the loss of airspeed. Substituting an AOA dial for the airspeed dial, won't change that. It is my understanding that one is supposed to be able to fly a glider safely without reference to the ASI, and I suppose that should also then apply to AOA as well. Obviously, not everyone can do so. And there are a few each year that manage to demonstrate the inability to fly safely in spite of the availability of a working ASI. It is also possible that the fact that the stall speed of a given sailplane on a given flight could be +/- 15%, or more, from book speed _in one-g flight_ should be given more thorough consideration. Do we know then what it might be in a 30-60 degree banked final turn, or in a wind shear condition where the ASI reads considerably below the book stalling speed? "More" is an answer, in one case, and "Less" in the other. How much more or less we find by trial and error, guesswork and luck--or not. An AOA would tell us instantly and throughout the normal operating range of the glider, and beyond, just how close to the stall we are operating. AOA gauges seem best suited for heavy aircraft flown by reference to instruments. Where you might have to wait a couple of minutes after setting the AOA and power lever to get the airspeed to respond. Gliders will change their airspeed much quicker than a 747 or F-14. I can't use the F-14 or the 747 as a reference, because I have not flown either. My understanding is that the F-14 can accelerate rather rapidly and slow down pretty quickly as well. High performance military aircraft which I have flown certainly exhibited that capability. To say that any of them, or even a 747, could not accelerate more rapidly than an unpowered glider in a specified attitude seems an incompletely considered statement, but perhaps you can provide some evidence to support your claim. We also only really fly at 2 or 3 different weights. So we only really have to remember the best L/D speed for these conditions. Be my guest--memorize as many speeds as you like. You'll still be guessing at how close your ASI is to the actual stalling speed at any particular moment. AOA never lies: any g-load; any altitude; any attitude; any airspeed. Jack AOA is my favorite subject to teach. It is not easy but is a life saver. Most pilots really don't understand relative wind. Ask them to explain it. What happens when a gust is encountered + or -? Near a stall the asi pitot tube is at an angle to the wind and is less accurate. I use a pieceof yarn taped to the side od the canopy with a "normal" air flow line marked. A the moment of the stall, the string rises as you approach the stall. It is only a cheap teaching aid. I probe my students understanding of why and where does the AOA COME FROM AND WHY. Lift depends on speed of the air and angle of attack...and it varies in many ways. At altitude, my students get a lot of slow flight experience. They know! Fred |
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