Chamonix
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AOA Indicator:Make It Standard!

Thu Sep 08, 2011 9:15 pm

Sorry if this has been mentioned but why is the AOA indicator not standard on liners?
Does it even exist as an option?
Have any liners ever been fitted with AOA indicator?
Many thanks!
 
vc10
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RE: AOA Indicator:Make It Standard!

Thu Sep 08, 2011 9:33 pm

Yes Concorde had an Angle of Attack indicator, which was very valuable to the pilots
 
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Starlionblue
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RE: AOA Indicator:Make It Standard!

Thu Sep 08, 2011 11:11 pm

Quoting Chamonix (Thread starter):
Sorry if this has been mentioned but why is the AOA indicator not standard on liners?

Not to be sarcastic, but the reason is that it has not been deemed necessary to make operation safe. If that view is changing in the industry is a good question.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Chamonix
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RE: AOA Indicator:Make It Standard!

Thu Sep 08, 2011 11:23 pm

The Fokker F-28 was fitted with AOA gauge.
 
Max Q
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RE: AOA Indicator:Make It Standard!

Fri Sep 09, 2011 12:07 am

It should be mandated, the information it provides is so useful normally and can be vital in abnormal or emergency situations.



Every Jet transport has AOA vanes providing information for stall warning, it is ridiculous that this information is not displayed constantly to the Pilots.
The best contribution to safety is a competent Pilot.
 
DC8FriendShip
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RE: AOA Indicator:Make It Standard!

Fri Sep 09, 2011 1:02 am

Quoting Max Q (Reply 4):
Every Jet transport has AOA vanes providing information for stall warning, it is ridiculous that this information is not displayed constantly to the Pilots.

There is a lot of information already coming to the pilots in a modern airliner. sometimes too much can be overwhelming in high stress situations.
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N243NW
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RE: AOA Indicator:Make It Standard!

Fri Sep 09, 2011 2:02 am

Quoting Chamonix (Thread starter):
Does it even exist as an option?
Have any liners ever been fitted with AOA indicator?

Yes. From http://www.b737.org.uk/flightinsts.htm#NG_Flight_Instruments:

One of the many customer PFD options is an analogue/digital angle of attack display. The red line is the angle for stick shaker activation, the green band is the range of approach AoA.

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tdscanuck
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RE: AOA Indicator:Make It Standard!

Fri Sep 09, 2011 4:27 am

Quoting Chamonix (Thread starter):
why is the AOA indicator not standard on liners?

The function is covered up by other systems (primarily stall warning and the PFD).

Quoting Chamonix (Thread starter):
Does it even exist as an option?

Yes.

Quoting Chamonix (Thread starter):
Have any liners ever been fitted with AOA indicator?

Yes.

Quoting Max Q (Reply 4):
Every Jet transport has AOA vanes providing information for stall warning, it is ridiculous that this information is not displayed constantly to the Pilots.

Other than loss of airspeed (in which case some existing jets do revert to raw AoA), what would having AoA displayed tell you that you don't already get from the airspeed tape + stick shaker indication?

Tom.
 
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Starlionblue
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RE: AOA Indicator:Make It Standard!

Fri Sep 09, 2011 4:57 am

Ok so riddle me this. On an Airbus in normal law the aircraft will not stall so an AoA indicator may be a bit redundant. However if flight laws are degraded would it have value? No stick shaker here.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
KELPkid
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RE: AOA Indicator:Make It Standard!

Fri Sep 09, 2011 5:14 am

Quoting Starlionblue (Reply 8):



Ok so riddle me this. On an Airbus in normal law the aircraft will not stall so an AoA indicator may be a bit redundant. However if flight laws are degraded would it have value? No stick shaker here.

I'm sure that the AF447 crew would have benefitted from knowing what in the hell the aircraft was actually doing in regards to angle of attack. The key to successful stall recovery is reducing AoA below a stalling angle of attack. Having a visual AoA indication would certainly have helped.
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tdscanuck
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RE: AOA Indicator:Make It Standard!

Fri Sep 09, 2011 5:38 am

Quoting Starlionblue (Reply 8):
On an Airbus in normal law the aircraft will not stall so an AoA indicator may be a bit redundant. However if flight laws are degraded would it have value? No stick shaker here.

If you're in degraded laws, or the airspeed is messed up, or any of several other failures it's invaluable. I'm not convinced that it should be there 100% as, during normal operation, it's more likely to distract than aid (not my opinion alone...many technical pilots feel that way as well, including all the Airbus and Boeing flight operations groups as evidenced by the fact that they haven't made it standard).

I'd like to see it triggered by abnormal events, just like attitude recovery symbology is.

Tom.
 
Chamonix
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RE: AOA Indicator:Make It Standard!

Fri Sep 09, 2011 8:33 am

Great article here as to why the AOA should be standard:
http://findarticles.com/p/articles/mi_m0UBT/is_8_14/ai_59664858/
 
Max Q
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RE: AOA Indicator:Make It Standard!

Fri Sep 09, 2011 8:35 am

Quoting tdscanuck (Reply 7):

Other than loss of airspeed (in which case some existing jets do revert to raw AoA), what would having AoA displayed tell you that you don't already get from the airspeed tape + stick shaker indication?

The answer to your question is written by you:

Quoting tdscanuck (Reply 10):

If you're in degraded laws, or the airspeed is messed up, or any of several other failures it's invaluable.
Quoting tdscanuck (Reply 7):
what would having AoA displayed tell you that you don't already get from the airspeed tape + stick shaker indication?

A lot, if you think flying with no valid airspeed indications is adequately compensated by having a stick shaker just look
at AF447, not to mention two B757 fatal crashes and others.




As far as an AOA gauge being a distraction in normal ops, I completely disagree, it is an option on many Aircraft and should be mandatory.
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CosmicCruiser
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RE: AOA Indicator:Make It Standard!

Fri Sep 09, 2011 12:41 pm

Our -11s have AoA on the HUD disp;ay.
 
Chamonix
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RE: AOA Indicator:Make It Standard!

Fri Sep 09, 2011 12:58 pm

Quoting CosmicCruiser (Reply 13):
Our -11s have AoA on the HUD disp;ay.

You mean MDs?
Wow,cool stuff I wonder if the 787 has the same arrangement or A380?
 
2H4
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RE: AOA Indicator:Make It Standard!

Fri Sep 09, 2011 7:52 pm

I think AOA indicators are not more common because airline management can get away with omitting them and thus, saving money.

I also think the small amount of visual clutter the indicators introduce can be greatly offset by their usefulness in bad situations, provided they're accompanied by good training. The crew of Colgan 3407 would have benefited from a clear understanding of their AOA.
Intentionally Left Blank
 
mandala499
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RE: AOA Indicator:Make It Standard!

Fri Sep 09, 2011 7:59 pm

AoA Indicators?
I guess all the talk about AoA indicators are due to AF447...
Well... On the Airbus, AoA indicator is, like in Boeings, an option... get it if you want to... go and ask airlines for it...   

If you lose the airspeeds... on the Bus you can fly using the BUSS (Back Up Speed Scale)...

Quoting Max Q (Reply 4):
Every Jet transport has AOA vanes providing information for stall warning, it is ridiculous that this information is not displayed constantly to the Pilots.

I guess the E170/190 isn't jet transport category then... no AoA vanes on those planes (replaced by 4 "smart pitot/static probes sets"

Quoting tdscanuck (Reply 10):
I'd like to see it triggered by abnormal events, just like attitude recovery symbology is.

I agree on this. If on the Bus, the ALTN LAW is announced by the ECAM, the AoA indicator appearing somewhere is probably something to go by...

But having a lateral FPV indication is probably a better thing to have in such situations. That way it can be displayed within the EADI, right where one needs it (instead of an AoA gauge outside the EADI but within the PFD).

And, calculated AoA based on the IRS is better than a vane based. More precise.
In the case of AF447, one should note that the AoA numbers (based on the AoA vane) showed that one of the AoAs were stuck for part of the tragedy...

Mandala499
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KELPkid
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RE: AOA Indicator:Make It Standard!

Fri Sep 09, 2011 8:03 pm

Quoting mandala499 (Reply 16):
In the case of AF447, one should note that the AoA numbers (based on the AoA vane) showed that one of the AoAs were stuck for part of the tragedy...

Airframe icing? That certainly should raise some eyebrows... I don't think AoA vanes are heated, either? (someone correct me if I'm wrong!).
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Jetlagged
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RE: AOA Indicator:Make It Standard!

Fri Sep 09, 2011 8:53 pm

Quoting KELPkid (Reply 17):
Airframe icing? That certainly should raise some eyebrows... I don't think AoA vanes are heated, either? (someone correct me if I'm wrong!).

Alpha vanes are heated, usually whenever probe heat is selected.
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rwessel
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RE: AOA Indicator:Make It Standard!

Fri Sep 09, 2011 10:14 pm

Quoting mandala499 (Reply 16):
And, calculated AoA based on the IRS is better than a vane based. More precise.

That couldn't take any winds (horizontal or vertical) into account, and thus cannot be particularly accurate.

The attraction of an actual alpha sensor (and a traditional flapping AoA vane is not the only way to do that) and display, is that it provides direct information about the single most important parameter affecting the performance of the wing.

Alpha should be one of the primary flight instruments, and airspeed should be relegated to a secondary role.
 
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tb727
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RE: AOA Indicator:Make It Standard!

Sat Sep 10, 2011 1:10 am

Quoting Jetlagged (Reply 18):

Alpha vanes are heated, usually whenever probe heat is selected.

Yeah, they leave a nice straight burn mark on your finger.
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tdscanuck
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RE: AOA Indicator:Make It Standard!

Sat Sep 10, 2011 1:28 am

Quoting rwessel (Reply 19):
Alpha should be one of the primary flight instruments, and airspeed should be relegated to a secondary role.

Within the normal envelope, why would you care about AoA? AoA for a particular flight condition is hugely weight dependant. It's certainly useful when you're near the edges of the envelope but that's never supposed to happen (I'm not advocating no AoA, just don't understand the requests for 100%). What utility does it have during normal operation?

Also, although I appreciate the pure aesthetic of AoA as primary and airspeed as secondary, in a modern ATC environment not using airspeed as primary is just totally impractical. How is ATC supposed to do IFR planning and coordination without knowing airspeed?

Tom.
 
mandala499
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RE: AOA Indicator:Make It Standard!

Sat Sep 10, 2011 9:29 am

Quoting rwessel (Reply 19):
That couldn't take any winds (horizontal or vertical) into account, and thus cannot be particularly accurate.

IRS also measure instant VSI, pitch angle, and with groundspeed, the flight path angle... pitch - fpa = AoA...
The AoA vane doesn't care what winds are there (be it vertical or horizontal components), it just measures the angle that it's at... nothing that an IRS cannot do.

But, IRS can go further than what the AoA can do... it can horizontal wind... measuring the difference between the nose heading and the aircraft track angle, and the aircraft groundspeed.

Combine that with air data and you can calculate the vertical wind components, albeit the calculations are going to be a little bit more complex.

In the Airbus FBW, the IRS already perform an air data cross check with the AoA vane. It takes airspeed from the ADR, the AoA from the ADR, and the calculated AoA from the IRS, and compare those numbers (for each ADR and each IRS) with a theoretical value based on the aircraft current gross weight and flap configuration from the FMGC... if the ADR's numbers don't match, the ADR self-rejects itself from providing ADR inputs to the flight control processing computers.

The capability and reliability of IRS calculated AoA is there.
How do you think the FDR data plot has the wind plot?

Quoting rwessel (Reply 19):
The attraction of an actual alpha sensor (and a traditional flapping AoA vane is not the only way to do that) and display, is that it provides direct information about the single most important parameter affecting the performance of the wing.

There are 2 ways of flying the aircraft... one, fly the speed, second, fly the AoA. Fly the AoA, is military stuff (it is here anyways)... coz it's useful as a backup when you have only one pitot tube!   

Quoting rwessel (Reply 19):
Alpha should be one of the primary flight instruments, and airspeed should be relegated to a secondary role.

Errrr... and bye bye speed control in congested airspace then... and airspeed indication is more stable than AoA indication.

Quoting KELPkid (Reply 17):
Airframe icing? That certainly should raise some eyebrows... I don't think AoA vanes are heated, either? (someone correct me if I'm wrong!).

Well, if there are icing enough to overwhelm the certification requirements of the Pitot tubes, which are heated (along with the AoA vanes), there are is a chance that parts of the body of the aircraft has icing... but to what extent it is, is not measured.
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Jetlagged
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RE: AOA Indicator:Make It Standard!

Sat Sep 10, 2011 2:41 pm

Quoting rwessel (Reply 19):
Alpha should be one of the primary flight instruments, and airspeed should be relegated to a secondary role.

Why? Airspeed conveys much more useful information than AOA and can display stall limits just as well on a PFD. AOA indication is a useful secondary display, but it must be accurately calibrated to be usable at all. Vane angle is usually wildly different to wing AOA and you must compensate for pitch rate. Airspeed will always be the primary indication. Expecting pilots to transfer from maintaining speeds to maintaining AOA is not a practical proposition and would introduce more safety issues.
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tdscanuck
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RE: AOA Indicator:Make It Standard!

Sat Sep 10, 2011 4:25 pm

Quoting mandala499 (Reply 22):
IRS also measure instant VSI, pitch angle, and with groundspeed, the flight path angle... pitch - fpa = AoA...

Pitch - fpa is only equal to AoA if the relative wind is horizontal. That's not generally true. Any up or down draft will change the AoA without altering pitch or fpa.

Quoting mandala499 (Reply 22):
The AoA vane doesn't care what winds are there (be it vertical or horizontal components), it just measures the angle that it's at... nothing that an IRS cannot do.

The IRS cannot see wind quickly. It can only get it by back-deriving the difference between intertial velocity and relative velocity. As a result, the reaction time is too slow to give accurate AoA. The airplane velocities have to actually change before the IRS can "see" an AoA change. An AoA vane sees the change "instantly", long before the airplane actually starts to react.

Quoting mandala499 (Reply 22):
The capability and reliability of IRS calculated AoA is there.
How do you think the FDR data plot has the wind plot?

FDR wind takes seconds to update...that's way too slow for AoA.

Tom.

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