Angle of Attach Indicator - AOA

[aviatoreb]

So I just received this months AOPA Pilot, March 2012.  It has a very interesting article regarding recent rule interpretations for AOA indicators.  Apparently the FAA small airplane directorate has just interpreted (or is about to interpret - I am not sure I understand which) that certain AOA indicators can be installed without an STC or even a 337 form, but rather just a log entry as a minor alteration. Even for non certified AOA indicators.  The AOA indicator must follow some specifics that are outlined in the interpretation, but that I cannot see - but it seems to be directed at the Alpha Systems noncertified equipment as the test case.  This is very interesting, as it brings <$1K AOA indicators available to a broad range of airplanes, Mooney's included I presume.

Am I missing something here?  Has anyone ever seen an AOA in a Mooney?

Never having used such a system, but understanding the theory quite well, I am a big fan of the idea and I would think that it could be a great safety enhancement.

 

[N601RX]

Here is the FAA letter.

http://www.alphasystemsaoa.com/pdf/AlphaSystemsLetter-Signed_Dec2012-WMb.pdf

[aviatoreb]

Quote: N601RX

Here is the FAA letter.

http://www.alphasystemsaoa.com/pdf/AlphaSystemsLetter-Signed_Dec2012-WMb.pdf

[jbs007]

Eh, might be useful for short field stuff, but for the flying envelope that standard GA aircraft do, I don't think it will give you any noticable advantage compared to just using airspeed.  If I was landing an F-18 on a carrier or a Piper cub on a flat piece of glacier, it might be useful though.

The only (but small) advantage it might have is that when using airspeed, you have to use different speeds at different weights to affect a consistent landing (because in reality, you're trying to get the same AOA).  If you followed a value on an AOA indicator your landings will be more consisntent (in flare effectiveness and how much runway you use) regardless of your weight.  This is theory, requires the pilot to be spot on every time, and how much is this really going to effect your flying anyway?

my .02 cents. My AOA indicator experience is pretty limited though. (T-34C... years ago)

[aviatoreb]

Quote: jbs007

Eh, might be useful for short field stuff, but for the flying envelope that standard GA aircraft do, I don't think it will give you any noticable advantage compared to just using airspeed.  If I was landing an F-18 on a carrier or a Piper cub on a flat piece of glacier, it might be useful though.

The only (but small) advantage it might have is that when using airspeed, you have to use different speeds at different weights to affect a consistent landing (because in reality, you're trying to get the same AOA).  If you followed a value on an AOA indicator your landings will be more consisntent (in flare effectiveness and how much runway you use) regardless of your weight.  This is theory, requires the pilot to be spot on every time, and how much is this really going to effect your flying anyway?

my .02 cents. My AOA indicator experience is pretty limited though. (T-34C... years ago)

[PTK]

If we are precision "fly by the numbers" pilots then we know what the "numbers" are. They are nothing more than angles of attack! The trim and yoke are aoa selectors. And our airspeed indicator already provides us with the quantitative information of the selected aoa. Therefore a precision oriented pilot needs a solid understanding of airspeeds ("the numbers") and that obscure Performance section of the POH. I say obscure because it is abstract for some. An aoa indicator may not really be the  best way to achieve this understanding. It may help someone try and avoid trouble. But then again it may not because it will not help them realize that they are putting the airplane in a dangerous regime. Another indicator in the panel will not  compensate for the human deficiencies in the left seat. Much like the already existing airspeed indicator has not saved some unfortunate folks.

[aviatoreb]

Quote: allsmiles

If we are precision "fly by the numbers" pilots then we know what the "numbers" are. They are nothing more than angles of attack! The trim and yoke are aoa selectors. And our airspeed indicator already provides us with the quantitative information of the selected aoa. Therefore a precision oriented pilot needs a solid understanding of airspeeds ("the numbers") and that obscure Performance section of the POH. I say obscure because it is abstract for some. An aoa indicator may not really be the  best way to achieve this understanding. It may help someone try and avoid trouble. But then again it may not because it will not help them realize that they are putting the airplane in a dangerous regime. Another indicator in the panel will not  compensate for the human deficiencies in the left seat. Much like the already existing airspeed indicator has not saved some unfortunate folks.

[John Pleisse]

There was a AOA Indicator out a year or two ago that had an aural alerter....this seemed to enhance whatever value it would have for the user. Does the alpha do this?

[aviatoreb]

Quote: N4352H

There was a AOA Indicator out a year or two ago that had an aural alerter....this seemed to enhance whatever value it would have for the user. Does the alpha do this?

[jbs007]

Quote: aviatoreb

Yes, I agree 99% of the time.  Remember - I think pilots are human, and 1% of the time we might do something by mistake.  I.e., an AOA indicator can be used in two ways

1) As a primary speed management tool instead of IAS or supplementing IAS together with excellent knowledge of the book numbers for your airplane.  I agree that it may not be possible to beat an excellent pilot with excellent speed discipline, and we should all strive to be that excellent pilot.

2) As a warning annunciator to yell at you if you ever inadvertently put the airplane near a bad situation like a stupid base to final turn.  Yes excellent pilots avoid this situation.  We are all human and can make a mistake, and I really don't see what it could hurt - other than your wallet - to stack the odds against in your favor.  

So in summary, I have seen you folks argue against #1.  Fine, I get it.  But for #2, a sort of super-stall-horn to remind us seems like a good thing.  I read that something like 7% of all GA fatalities occur on base-to-final mistakes.

[M20F]

Useful if the airspeed indicator quits working particularly in IMC among other things.  A wise person once told me if it saves your life it is worth the expense/weight.  If I could have four of everything in an airplane I would both for the safety aspect and to satisfy my personal addiction with buying stuff for airplanes.

I do though struggle with technology and its impacts on aviation.  ADF's were on of the best tools for teaching the impact of wind on an airplane (and mental math) now most students spend the barest of time learning anything other then GPS direct (iPads have drastically increased this).  Technology is great but wonder sometimes if we fail to highlight the unintended costs it comes with and train against them.

[M016576]

[jetdriven]

We have four of everything in the 747 but no AOA indicator.   CRJ didnt have one, either, but AOA was input to the air-data computers. 

[sreid]

Quote: jetdriven

We have four of everything in the 747 but no AOA indicator.   CRJ didnt have one, either, but AOA was input to the air-data computers. 

[M016576]

Quote: JimR

I would think that an AOA indicator would be especially useful in an aerobatic aircraft, so that you could tell at a glance how much more you could load up the wing before it will stall.  Neither the Great Lakes nor the Pitts that I took basic aerobatics instruction in had one, however.  Is that one of the ways that you military guys use them?  

I'm not sure that I see a lot of need for one given the way that I fly my Mooney, but I'm sure that it would be a great teaching aid and would definitely contribute to safety. 

Jim

[M016576]

Quote: jbs007

 I see what you're saying.  An AOA indicator can help yell at you.  But like you say, the stall warning does that and I believe that is based off of AOA anyway.  I'm not so much argueing against it, just saying that in GA I don't think it's going to change how you fly very much.  However, in support of the AOA indicator, it would definately add more mystique to your Mooney when pilots of the "other" brands peak in your window...  Besides, in my ideal instrument set up, I would have an extra hole on the panel and I don't know what to put in it yet...

Oh, also when I used one in the T-34, it bounces around a lot.  Maybe that's particular to the Navy buying crappy indicators but it really didn't give a good reading anyway.  That aircraft was basically a turbine bonanza so as far as approaches go, it flew pretty similar to GA aircraft.

[jetdriven]

The 747-200 shaker operates from an AOA vane on the left side of the nose.  It is modified with a signal from the left flap.  However, no indicator in the cockpit except airspeed (and attitude indicator)  is available for AOA.  The CRJ had a "green line" on the airspeed tape that represented L/D max.   I would susped the 747-400 is similar.

Quote: sreid

Are you saying that no model of the 747 has AOA? How does the stall warning system work in that airplane? Is there a shaker? 

[aviatoreb]

Quote: jbs007

[aviatoreb]

[sreid]

Quote: jetdriven

Are you saying that no model of the 747 has AOA? How does the stall warning system work in that airplane? Is there a shaker? 

[jetdriven]

For all practical purposes, its the same as the stall warning system in the Mooney.  By the time it goes off its almost too late.  So how does a talking AOA that says "stall" any more useful than a stall warning horn?   I flew some in a Liberty XL-2.  It says "stall" when the stall vane lifts up.  The thing is, it goes "stall, stall, stall" on half of the takeoffs and landings. 

[PTK]

As I said earlier we already have an aoa indicator, the airspeed indicator. An aoa indicator is more useful for aircraft carrier operations because the airplane is routinely operated at critically low airspeeds. In these cases the AS indicator probably doesn't provide accurate aoa info.

[danb35]

Quote: allsmiles

As I said earlier we already have an aoa indicator, the airspeed indicator.

[M016576]

Quote: danb35

You were wrong then, and you're wrong now.  Airspeed gives no information about AoA.  If you truly believe otherwise, you really need to revisit the basic aerodynamics part of the private pilot ground school curriculum.

Quick, what's your AoA when your ASI reads 110 kts?

[PTK]

Quote: danb35

You were wrong then, and you're wrong now.  Airspeed gives no information about AoA.  If you truly believe otherwise, you really need to revisit the basic aerodynamics part of the private pilot ground school curriculum.

Quick, what's your AoA when your ASI reads 110 kts?