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radfordc

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I was also taken with the CGS Hawk ultralight that was flying at Paradise City in some pretty strong winds. It had the 28 horse Hirth engine on it and was performing quite well but with all the wind down the field it looked like the takeoff roll was all of 35 feet or so. Landing wasn't much longer.
Dale....once you go Hawk you never go back!
 

radfordc

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  • AOA for flight control and its lack of usefulness - It works great for driving aural warnings, but a lot of data shows it lags other indicators for general flying;
OK, I would like to hear more about this. I always thought that AoA was superior to airspeed indication for flying. Doesn't the Navy use only AoA to come aboard aircraft carriers?
 

billyvray

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A guy named Henry Palmer. Supposedly it flew, but it was marginal, and underpowered for two people.
 
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wsimpso1

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OK, I would like to hear more about this. I always thought that AoA was superior to airspeed indication for flying. Doesn't the Navy use only AoA to come aboard aircraft carriers?
I sat through this talk by Ed Wischmeyer. He took data with his airplane and others. He had several runs with slow and fast pitch cycles, some where g's stayed close to unity and others where g's went up and down. AOA never lead anything, sometimes it just tracked along with other things like airspeed and stick deflections and g's, while other events it lagged badly. In no case did AOA lead the other flight outputs, and so is tough to use to fly the bird. In a number of cases, like light to moderate chop, it is very noisy and can be misleading. Then he cited a number of other learned papers that came to similar conclusions about how AOA is not terribly useful compared to airspeed and others.

He did talk about when Navy pilots use AOA - it is not used during the break, downwind, or even the circling turn. According to Ed, the pilots look at AOA only on final (all of about 12 seconds long usually), manipulating throttle and stick to hold glideslope and AOA. I am not sure exactly how that all stays together, but the pilot's eyes are at the front of the plane flying the ball (glideslope) while the tail hook is way back so if it is to go to the right place, the deck angle of the airplane has to be a constant. Fly steady airspeed, steady AOA and then fly the ball, and the tailhook should hit the number three wire.

His big takeaway for us is that it is a good data source to drive an aural stall warning.

Ed has been on EAA's homebuilder council, and I asked him when he would publish in Sport Aviation. He was skeptical this topic would get published...

Billski
 
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BBerson

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AoA and airspeed both lag behind stick position. Langewiesche said an AoA indicator isn't effective because most pilots don't think about or understand angle of attack anyway. A stick position horn might help, but probably not.
 

radfordc

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He did talk about when Navy pilots use AOA - it is not used during the break, downwind, or even the circling turn. According to Ed, the pilots look at AOA only on final (all of about 12 seconds long usually), manipulating throttle and stick to hold glideslope and AOA.

Billski
Not being a Navy pilot I can't argue. I watched a Navy training film on Youtube that said that pilots are to establish the correct AoA on the downwind leg before turning to final. But, it was an older film so maybe they have changed the procedure. My understanding of AoA first came from Wolfgang Langewiesche's Stick and Rudder.
 

radfordc

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Langewiesche said an AoA indicator isn't effective because most pilots don't think about or understand angle of attack anyway.
Possibly because we don't have instruments for AoA and aren't trained to use them? Anyone who ever stalled and spun while turning at low altitude (I have) would probably welcome an effective AoA stall warning device.
 

BBerson

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I think most pilots when startled will keep pulling no matter how many devices are installed. Because they rarely rub the edge of stalls in normal flight year after year. Glider pilots fly on the edge of stall in thermals, and get a bunch of stall practice.
 

radfordc

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Here is the Navy training film I watched. The discussion of AoA and how to fly the pattern starts at 9:50. What it shows doesn't match up with what was presented at SnF.

 

BBerson

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BJC

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Here is the Navy training film I watched. The discussion of AoA and how to fly the pattern starts at 9:50. What it shows doesn't match up with what was presented at SnF.

Billski:

Did the SnF speaker discuss the difference between a vane-driven AoA indication (very small dead time in the system) verses the typical E-AB differential pressure system (typical of those common on E-AB) that has more dead time, especially with the typical 1/4” tubing between the wing tip sensing location and the pressure sensor?


BJC
 

gtae07

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Did the SnF speaker discuss the difference between a vane-driven AoA indication (very small dead time in the system) verses the typical E-AB differential pressure system (typical of those common on E-AB) that has more dead time, especially with the typical 1/4” tubing between the wing tip sensing location and the pressure sensor?
I saw Ed's presentation in person at a local EAA meeting a couple months ago. I don't recall him mentioning anything about a vane-driven system..
However, I'm pretty sure what he's referring to as "lag" isn't an effect from "dead time" or quarter-inch tubing, as the airspeed in most of these setups is using the exact same tubing with near-identical routing. As I recall, any mention of "lag" was more to do with "make a slow pitch up, airspeed starts to fall immediately, it doesn't show up in AOA till later" since the change in pitch was small and g loads were low.

I do specifically recall him saying that part of why he thought AOA was not of much use in the pattern was (1) you still have to look back at the panel, (2) it's "noisy" and jumps around a lot, and (3) you can't add wind and gust values to it like you can with airspeed. Ed has a lot more experience than me, but... I've flown with airspeed on an an EFIS and not only do I still have to look back at the panel, but I've seen airspeed readouts be pretty noisy too, and I've never added steady-state wind to airspeed for an approach.

I have also read much testimony from others that have found it (AOA) very useful. The guys with aural feedback AOA systems (i.e. ones that have progressive tones or otherwise provide information beyond just "you're close to stalling") seem to be especially emphatic and I've read many who say "I never look at airspeed in the pattern now, except to cross-check my AOA". http://www.vansairforce.com/community/showthread.php?t=148638 is one example of such a system.


In the face of conflicting evidence and opinion, I'm going to withhold personal feedback or judgment until I have time flying behind such a system and can evaluate it for myself.
 

wsimpso1

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Billski:

Did the SnF speaker discuss the difference between a vane-driven AoA indication (very small dead time in the system) verses the typical E-AB differential pressure system (typical of those common on E-AB) that has more dead time, especially with the typical 1/4” tubing between the wing tip sensing location and the pressure sensor?


BJC
His work was with the pitot-static based systems. His data showed one system was well damped but slow to respond (and behind other system responses) and another that was quicker to respond but with a lot of undamped movement. One of his biggest criticisms was that systems he had run were either behind the other airplane responses or were difficult to interpret because the needle was bouncing around, and neither was good guidance for flying the airplane in even mild chop, much less in medium turbulence. He praised AOA for use as a basis for aural warnings, which is how we use the information in jetliners and the like.
 
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wsimpso1

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If the device improves safety, we should have enough airplanes out there with AOA displays that we should be able to analyze the accident data and see if presence of the device makes a measurable difference in stall-spin accident frequency.
 

ScaleBirdsScott

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Well I can't speak to all the AOA discussions, but I just got back from Sun n Fun late last night and have had to quickly adjust to the old reality where I'm not cramming my day full of tasks and running at WEP to get ready for the show.

Probably gained 10 lbs from all the go-go juice keeping me going through those long days and the lack of sleep working on CAD after the compressors and drills had to go quiet. But I'm happy with what we've done and we never intentionally compromised doing it right for doing it fast. (We just compromised on about everything else.)

So now that I'm back I need to get a shave and haircut, go on a diet, clean the entire shop and office (which would have benefitted from a tornado running through if anything) and get back to making airplane parts.

Got lots of great feedback on what we've built so far, lots of people interested in engines, and lots of others were interested in maybe what they could help provide to help us out. If that's the goal of attending a show like this, mission accomplished.

It was great meeting those of you who showed up (and who I had the ability to recognize, I'm bad on a good day with that) and no-one seemed to complain too loudly about my amateur approximation of an airframe so, I appreciate the good words I've been given.

As for enjoying sun and/or obtaining fun (or the other way around) I got both. The show was always pretty laid-back compared to an AirVenture in my experience, and this was definitely true this year. I enjoyed seeing the various aircraft out there, did not spend enough time at the Warbird or Ultralight areas, but in general I don't feel I missed anything.

Food vendors were indeed on point. I can't complain much about price of quality. The mention of a lack of hand sanitizer is something I never personally noticed, but that's because I ended up using the proper indoor washroom/restroom in the buildings all week and it was usually well stocked.

The show could use some extra hands with managing traffic in some of the tighter areas of the exhibitor space. When at the beginning and end of the day you've got all sorts of chaos with trucks and trailers and semis and flatbeds and golf-carts and curious attendees who just somehow get in early/stay out late wandering through the middle of the roads at slow/random directions, it's surprising things get done at all and without injury. On the final day trying to break down, all vendors were kept out until after 6:30, despite impending inclement weather, so that people inside the buildings could break down and load trucks. Thus we waited outside, tried in vain to keep the gusts from damaging our tents, and packed trailers in the rain. I'm sure there's logistical reasons for doing things in a given order but, and I say this as someone who sometimes has good ideas, maybe some consideration is to be paid to getting the people outside (with their airplanes and engines and trailers and such) out of the way before big-rigs come and dump trailers in the middle of the only other available space. Surely a few hours to get company trailers and aircraft packed and moved away from the various hangers would not hurt?

But who pays more for their space? Haha, well, that answers the question right there.

In any event it's always a good time even when I'm working harder than I should be (it's not college anymore) and I look forward to AirVenture in a few short months. Lots to get done!
 
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