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-   -   Not understanding AoA indicators... (https://www.airlinepilotforums.com/safety/84956-not-understanding-aoa-indicators.html)

Fluglehrer 11-23-2014 12:53 PM

Aw Gee Eddie
 
The actual name of the pilot with the great Code7700 website is James Albright, aka "Captain Eddie". The pseudonym Eddie Haskell is based on his USAF call sign. A very well organized site with much useful info.

F15Cricket 11-23-2014 09:51 PM


Originally Posted by rickair7777 (Post 1769436)
I agree, it would be good. But it's a big, big step...the FAA would have to mandate this, adjust FAR 61, and educate the CFI population.

Then primary trainers would all need AoA gauges...along with their ADS-B out.
.

As a 3000+ hour fighter pilot, I think this is an interesting thread. As a guy who also flies GA and now for an airline, let me ask the group this: what is the largest cause of GA crashes? Of all crashes? Is it mid-airs, or low altitude stall/spins? I would say the latter, yet the FAA is requiring ADS-B. If they were truly concerned with saving the maximum number of lives, AOA gauges and AOA instruction in training aircraft would benefit all pilots greatly.

The simple way I think of it is the wing flies by AOA... It doesn't care about airspeed! When teaching aerobatics in the T-6 to a friend who has 13,000 hours (mostly on floats and no jet time), we had lots of discussions about AOA, unloading the wing, how you cannot stall below stall speed if you unload, etc.

rickair7777 11-24-2014 07:31 AM


Originally Posted by F15Cricket (Post 1769891)
As a 3000+ hour fighter pilot, I think this is an interesting thread. As a guy who also flies GA and now for an airline, let me ask the group this: what is the largest cause of GA crashes? Of all crashes? Is it mid-airs, or low altitude stall/spins? I would say the latter, yet the FAA is requiring ADS-B. If they were truly concerned with saving the maximum number of lives, AOA gauges and AOA instruction in training aircraft would benefit all pilots greatly.

The simple way I think of it is the wing flies by AOA... It doesn't care about airspeed! When teaching aerobatics in the T-6 to a friend who has 13,000 hours (mostly on floats and no jet time), we had lots of discussions about AOA, unloading the wing, how you cannot stall below stall speed if you unload, etc.

ADS-B has nothing to do with GA safety, it's about improved air traffic management which has an aspect of protecting airliners from GA (but not GA from themselves).

I agree that AoA certainly has potential for GA, but current GA flying techniques (and training & testing) evolved based on other instruments. Individual GA users who have the inclination can certainly acquire and learn to use AoA instrumentation. IMO (and only my opinion) applying it broadly across all GA would require big changes from the ground up, which would be opposed by various interested parties due to cost.

AoA is a getting a more direct answer to the question at hand, but you can still get the answer through other instruments...if I'm flying the proper profile I already know what AoA is going to tell me (except in icing). It would probably be easier for private pilots to scan just an AoA gauge and the runway in the base-to-final turn, but it's probably too politically challenging and costly to mandate AoA. But no reason individuals can't take advantage of it, as long as they commit to learning and using it correctly...otherwise it's just another dust collector, and possibly a distraction.

Timbo 11-24-2014 10:49 AM

The one instrument I never trusted much in single engine G/A airplanes was the airspeed indicator. Luckily it usually reads low, not high, if you've got some dirt or a bug in there.

Even if it's clean when you depart, all it takes is one unlucky bug into the pitot tube and it's gone, so you'd better learn how to fly without depending on looking at the airspeed indicator the traffic pattern.

This is why I really liked the "Bacon Saver" AOA vane mounted on the left wing strut. I never had to look inside for airspeed in the pattern.

F15Cricket 11-24-2014 04:33 PM


Originally Posted by rickair7777 (Post 1770059)
ADS-B has nothing to do with GA safety, it's about improved air traffic management which has an aspect of protecting airliners from GA (but not GA from themselves).

I agree that AoA certainly has potential for GA, but current GA flying techniques (and training & testing) evolved based on other instruments. Individual GA users who have the inclination can certainly acquire and learn to use AoA instrumentation. IMO (and only my opinion) applying it broadly across all GA would require big changes from the ground up, which would be opposed by various interested parties due to cost.

AoA is a getting a more direct answer to the question at hand, but you can still get the answer through other instruments...if I'm flying the proper profile I already know what AoA is going to tell me (except in icing). It would probably be easier for private pilots to scan just an AoA gauge and the runway in the base-to-final turn, but it's probably too politically challenging and costly to mandate AoA. But no reason individuals can't take advantage of it, as long as they commit to learning and using it correctly...otherwise it's just another dust collector, and possibly a distraction.

If your first statement is true, then, how many airliners have had mid-airs with GA aircraft? And, if ADS-B is for traffic flow, I am ignorant of why Mode 3/C is insufficient. Mandating ADS-B in all aircraft will not increase safety, yet mandating AOA would absolutely decrease the number of stall/spin accidents, from what I understand is the #1 killer of GA pilots.

And I agree that mandating AOA in airliners would probably not be required, since we fly in the meat of the heart of the envelope.

Actually, though, the FAA, as well as some of the GA organizations, from what I understand, are "highly encouraging" AOA gauges in GA aircraft, as they see the value in it. Again, if you have not flown with it, you probably think the wing stalls at a certain airspeed, but the wing cares not about airspeed ... It flies by AOA, so why shouldn't we?

Timbo 11-24-2014 05:34 PM

Cricket, you flown the NAT Tracks and all over Europe much, in an airliner?

That's why ADS B is being implemented.

I fully agree with your views on AOA.

rickair7777 11-24-2014 05:54 PM


Originally Posted by F15Cricket (Post 1770458)
If your first statement is true, then, how many airliners have had mid-airs with GA aircraft?

??? Several, which is why TCAS came about.



Originally Posted by F15Cricket (Post 1770458)
And, if ADS-B is for traffic flow, I am ignorant of why Mode 3/C is insufficient.

Yes, it is for traffic management and replaces the functionality of secondary radar (ie mode 3C on the airplane end) and adds some capabilities. Presumably secondary radar will go away. I would welcome an improved version of mode-C because it is not entirely reliable. ADS-B will be inherently more reliable in that regard.


Originally Posted by F15Cricket (Post 1770458)
Mandating ADS-B in all aircraft will not increase safety

Correct. But NOT mandating ADS-B would significantly decrease safety since ADS-B will presumably replace mode C, so non-participants would be invisible...unless they maintain the mode-C and secondary radar forever which is probably not the intent.


Originally Posted by F15Cricket (Post 1770458)
yet mandating AOA would absolutely decrease the number of stall/spin accidents

I agree, but it wouldn't eliminate stall/spin accidents...many of the folks who fixate on the TDZ and pull & bank until they stall/spin won't be paying attention to the AoA. There would be some benefit, but it's hard to quantify.

It would be expensive since you'd have to equip all aircraft and re-vamp the training system...if you don't train them, they won't use it right. But the real issue is political will to do it...unless AOPA, NAFI, and the NBAA decides it's worth it, the FAA would be fighting an uphill battle on this one. Without AOPA on board, it would be no-go. The FAA knows this.


Originally Posted by F15Cricket (Post 1770458)
from what I understand is the #1 killer of GA pilots.

It's up there but I think CFIT or loss of attitude control in IMC is the leader.


Originally Posted by F15Cricket (Post 1770458)
And I agree that mandating AOA in airliners would probably not be required, since we fly in the meat of the heart of the envelope.

I'd mandate that first since it's useful in bad icing.


Originally Posted by F15Cricket (Post 1770458)
Actually, though, the FAA, as well as some of the GA organizations, from what I understand, are "highly encouraging" AOA gauges in GA aircraft, as they see the value in it. Again, if you have not flown with it, you probably think the wing stalls at a certain airspeed, but the wing cares not about airspeed ... It flies by AOA, so why shouldn't we?

I'm all for encouraging it, especially for the savvy GA pilot who can make good use of it. But it's too much cost vs. benefit to try to mandate for all GA (I think).

cardiomd 11-24-2014 06:13 PM


Originally Posted by F15Cricket (Post 1770458)
yet mandating AOA would absolutely decrease the number of stall/spin accidents

Unproven conjecture, possibly true, but you might be surprised. Loud stall warning horn/ lights don't prevent stall/spin accidents. Glass cockpits with big stall regime warning (would be very easy to get a "derived" AOA in a glass cockpit with AHRS) don't prevent stall/spin accidents.

Ensuring a high level of mastery of the aircraft would likely reduce stall/spin. All GA pilots (well, all pilots) should be very familiar with the concept of AOA.

Mandating yet another gauge on GA craft is very much the wrong way to go.


Originally Posted by F15Cricket (Post 1770458)
And I agree that mandating AOA in airliners would probably not be required, since we fly in the meat of the heart of the envelope.

I'm honestly not sure if you are being sarcastic or not. Airliners routinely fly quite close to the edge of the envelope in Q-corner... are you talking about something else such as structural failure?

You're taking me way back to aerodynamics and fluid dynamics.... No GA pilot has to know what mach tuck or flow separation is, or why airliners and the jet jocks have swept wings.

As far as I know AOA sensor is MEL on most modern airliners and absolutely critical. I wouldn't want anybody trying to hand fly at FL410+ for long.

GA pilots in our thick air are generally nowhere near the limit of the flight envelope for essentially all aspects of flight.


Originally Posted by F15Cricket (Post 1770458)
It flies by AOA, so why shouldn't we?

Because:

1. Most of us are not fighter pilots doing high-G maneuvers at risk of accelerated stalls at the edge of the flight envelope.

2. Getting more FAA / government mandates is generally a very bad thing.

3. Installing things, especially certified things, costs a lot of money.

4. With a bit of education most GA pilots can understand the concept of AOA, lift reserve, accelerated stalls, etc., and if they want to go ahead and install a sensor they can do so.

cardiomd 11-24-2014 06:20 PM

+1 to what RickAir said didn't read his post first.

You can just search for the latest Nall report if you are interested in why GA pilots crash. It basically depends how you classify things. The number one cause of incidents is mishaps when landing. Pretty consistently the number one cause of fatality is variants of disorientation and VFR into IMC and CFIT, then number 2 is maneuvering flight like that video link I provided awhile ago.

Fluglehrer 11-24-2014 07:25 PM

Simple things that flight instructors can teach to help prevent stalls and understand AOA without needing an AOA gauge:

1. Explain the relationship of bank angle to stall speed increase in a level turn (these are within about 1% accuracy, and easy to compute)
30 deg = 10% stall speed increase
45 deg = 20% stall speed increase
60 deg = 40% stall speed increase

2. Have the student note where the yoke/stick is when the aircraft stalls. This will be the yoke position required to exceed the critical AOA at any speed and weight (assuming configuration stays the same). Also note the difference in yoke position to stall the aircraft with flaps up vs flaps down.

3. Practice accelerated stalls with the student after noting the yoke position required to exceed the critical AOA. This will reinforce point #2.


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