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#101
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AoA keep it going!
"Andreas Maurer" wrote in message
: Now, what is "slow"? The simple fact that you arre still able to write this proves that you know what "slow" is... Or he is lucky! Larry |
#102
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AoA keep it going!
One positive advantage to AoA is that it isn't dependent on a static
pressure source. If the static port becomes blocked, ASI readings go whacko. AoA appears to be useful for something since I routinely saw them on military aircraft (which also always had ASI as well). AoA may not be the definitive answer, but it is another available tool. Scott Nyal Williams wrote: Eric, I should have been more precise in my comment. AoA, as shown by a piece of yarn will be much quicker than an ASI. The ASI will respond quickly, as you say, but it will not arrive at a steady-state indication for a few moments if the AoA change is considerable and abrupt. I have no opinion about AoA instruments, for I have never used one. In my youth, I saw one used on an inboard strut between the wings of a bi-plane; it was a blade type that floated in the air. The pilot swore by it. At 06:42 22 December 2007, Eric Greenwell wrote: Nyal Williams wrote: The inside wing; it travels a lesser distance while sinking the same amount as the outside wing. No one seems to have observed that the AoA is instantaneous whereas the ASI indicates what the aircraft was doing moments ago. I don't think this is true: all the ASI I've had or checked seemed to respond in less than a second. Surely that's fast enough to keep up with the glider? Just try blowing gently into a pitot and see how quick the needle is. If takes 'moments' to respond, you should check the indicator and the pitot line. The reason we are told to 'fly attitude and don't chase the airspeed' is it takes the glider a while settle down to a steady speed, not because the ASI is slow. -- 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 -- Scott http://corbenflyer.tripod.com/ Gotta Fly or Gonna Die Building RV-4 (Super Slow Build Version) |
#103
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AoA keep it going!
On Dec 22, 10:36*pm, Greg Arnold wrote
One common problem with many arguments (not just on RAS!) is that people compare the status quo with an idealized world, and conclude that the status quo is flawed and must be changed. *It seems to me this may be occurring in the AoA discussion -- many posters have compared a perfectly functioning AoA indicator with our slow and inaccurate ASIs, and concluded that AoA indicators are better. *But perhaps in the real world AoA indicators on gliders would be even less accurate than ASIs? Greg, I don't see it that way. I see the basic argument is about AoA vs airspeed as the more accurate/desirable control instrument for certain phases of flight (assuming equally good instrumentation for the AoA and airspeed). As far as instrument accuracy, AoA and airspeed are fundamentally different, with different ways to be measured. You define the level of accuracy you want, and design the sensor and display accordingly. This is not rocket science - AoA indicators have been around since before the airspeed indicator, and was probably considered easier to measure at first! A side discussion relates to the fact that airspeed indicators are universal, while AoA sysems are expensive and not common in gliders. While the appropriate technology is simple and would be easy to incorporate in a glider while it is being built (a few sets of pressure ports on each wing, connected to a microprocessor and display) the current cost is in the $1500 range - plus installation - so I doubt we'll be seeing a lot of them in cockpits soon. But picture this: You have the plumbing installed while your new glider is being built (some tubing - not a lot of cost there, basically it's another multi-orifice static system in the wings). Then the latest SN-99 or LX-9999 has the software and connectors builtin (adds $500 to the box). It might start showing up - first in top of the line motorgliders, then filtering down. I fail to understand why looking at ways to make flying more efficient and safer causes such a defensive response! But then, the same thing probably happened when the first electric varios came out - "what's wrong with our PZL? Dont need no stinkin battery, works just fine! Next you'll want it to make noise!" Then there was the great GPS debate...or even radios! Kirk |
#104
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AoA keep it going!
Nyal Williams wrote:
Eric, I should have been more precise in my comment. AoA, as shown by a piece of yarn will be much quicker than an ASI. The ASI will respond quickly, as you say, but it will not arrive at a steady-state indication for a few moments if the AoA change is considerable and abrupt. Perhaps I misunderstood you. Is the lag you are talking about the time it takes for the airspeed indication to become steady after you change the glider's attitude from one steady attitude to another steady attitude; i.e., from one AOA to another AOA? If that's what you mean, then I agree: it will take a few moments for the glider's airspeed to change to the new value. What I thought you meant was the ASI (airspeed INDICATOR) reacts slowly. -- 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 |
#105
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AoA keep it going!
01-- Zero One wrote:
"Andreas Maurer" wrote in message : Now, what is "slow"? The simple fact that you arre still able to write this proves that you know what "slow" is... Or he is lucky! Oh, I am--very lucky--and have been for a long time. Jack |
#106
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AoA keep it going!
On 24 Dec, 07:26, J a c k wrote:
Oh, I am--very lucky--and have been for a long time. As Arnold Palmer is reported to have said: "It's a funny thing, but the more I practice, the luckier I get." Ian |
#107
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AoA keep it going!
On Sun, 23 Dec 2007 03:23:59 GMT, Eric Greenwell
wrote: Ralph Jones wrote: "Fly attitude and don't chase the airspeed" really means "fly AoA and don't chase the airspeed", but if you don't have an AoA indicator, you have to use the attitude as a substitute for AoA. And it's a second-rate substitute. Please pardon me if I sound a bit cranky, but how can attitude be a "second-rate substitute" for something that we don't even have? And what would a "first-rate substitute" be? You could probably design one, but okay, I concede the grammatical point. Let's put it this way: The ASI is to a good AoA meter as Hormel Potted Meat Food Product is to Underwood Deviled Ham. rj |
#108
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AoA keep it going!
Ralph Jones wrote:
On Sun, 23 Dec 2007 03:23:59 GMT, Eric Greenwell wrote: Ralph Jones wrote: "Fly attitude and don't chase the airspeed" really means "fly AoA and don't chase the airspeed", but if you don't have an AoA indicator, you have to use the attitude as a substitute for AoA. And it's a second-rate substitute. Please pardon me if I sound a bit cranky, but how can attitude be a "second-rate substitute" for something that we don't even have? And what would a "first-rate substitute" be? You could probably design one, but okay, I concede the grammatical point. Let's put it this way: The ASI is to a good AoA meter as Hormel Potted Meat Food Product is to Underwood Deviled Ham. You better not be disrespecting Spam! As a 4th generation Hawaiian, I'd have to hunt you down and hurt you, probably by showing you a video purchased at the Spam Museum. Of course I've been there! What else can you do when it rains during a contest at Albert Lea? Hmmm, am I going to have to explain all this? -- 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 |
#109
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AoA keep it going!
Eric Greenwell and Bill Daniels wrote:
I'd love to have a quality AOA indicator to make those landings easier and safer. It's more than an issue of safety, an AOA indicator will allow you to optimize flight in all configurations including circling flight at different wing loadings. The use and construction of such a device, aka a lift coefficient meter, was discussed in an article by Daniel J. Altstatt in Soaring Magazine March, 1975, page 22. No doubt a modern electronic instrument is now feasible. Pete Brown 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. -- Peter D. Brown http://home.gci.net/~pdb/ http://groups.yahoo.com/group/akmtnsoaring/ Going home after a long day http://farm2.static.flickr.com/1415/...22928754_b.jpg The fleet at Summit. Mt. McKinley is about 45nm away at 20,320 msl. http://farm1.static.flickr.com/187/4...cb8d2482_b.jpg The 170B at Bold near Eklutna Glacier http://farm1.static.flickr.com/168/4...a216d7bb75.jpg |
#110
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AoA keep it going!
Here are some links:
http://advanced-flight-systems.com/P...s/AOA/aoa.html As mentioned, aircraft spruce catalogs this and another, vane based one: http://www.aircraftspruce.com/catalo...ges/HCIaoa.php or directly, http://www.hciaviation.com/prod-aoa-a.shtml And yes, I'd be interested in how well any of these actually work in gliders. It's not clear the first one has enough resolution for performance info, for example. --Sarah Pete Brown wrote: Eric Greenwell and Bill Daniels wrote: I'd love to have a quality AOA indicator to make those landings easier and safer. It's more than an issue of safety, an AOA indicator will allow you to optimize flight in all configurations including circling flight at different wing loadings. The use and construction of such a device, aka a lift coefficient meter, was discussed in an article by Daniel J. Altstatt in Soaring Magazine March, 1975, page 22. No doubt a modern electronic instrument is now feasible. Pete Brown 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. |
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