Why do some a/c have an AoA indicator? If you have an AI that works, isn't that adequate?JS

Aircraft designed specificly for AI only do not have panels usually. They would not have any purpose unless a panel has been added to an AI model and it has set to be flyable. The indicator for AI might be beneficial to the aircraft designer to check the FDE of the model concerned.Angle-Of-Attack indicators supplement aerodynamic vane type stall indicators. They give an earlier warning if visually tracked of an approaching stall condition and the effectiveness of recovery. In addition perhaps they might offer some indication of flight efficiency at a specific attitude and indicated airspeed if documented for the aircraft.I'm not sure, but I wonder of aircraft designed for aerobatics frequently include them since they often operate at the edge of stall or deliberately stall for some manuvers.

I think he is referring to Attitude Indicator, not AI aircraft.Glenn

Imo he means by AI an attitude indicator, while you are talking about AI as FS's air traffic I think.Jozef http://pluizig.ath.cx/signature.jpg

Many military aircraft are fitted with AoA indicators-in particular some carrier operated(naval) aircraft which will land(recover on deck) at high angles of attack(Giving high drag) .AFAIK this is at least partly because - they land with the throttle full open in case of a go- around (bolter) and also to ensure positive contact with the wires rather than risk floating over them. If there are any RW carrier pilots out there perhaps they can confirm thisAdditionally some naval jets adopt an extreme nose up position on the catapult- altho this is achieved usually by having an extendable nosewheel oleo.Dave

Yeah, sorry, shoulda been clearer: AI = Attitude Indicator.Appreciate responses, thanks!JS

hmmm... it's a complex subject... i guess the simple introductory answer might be something along these lines... ai shows you your position (attitude) relative to the gravity vector (say, horizon) while the aoa indicator shows your position with respect to the relative wind... under normal flight conditions the ai gives you more information and part of the information approximates aoa readings reasonably well... under marginal flight conditions, such as those of carrier landing or a tight combat turn at tree top level, the approximation fails and yet, under these conditions, knowing your aoa exactly is a matter of life and death... check out stick and rudder, langewiesche's thoroughly enjoyable, even though somewhat antique, jewel of a flying bookps. now google "relative wind" ;-)

The AI gives you the vertical angle between the aircraft and the ground, with the ground treated as level. AoA is the angle between the chord of the wing and the oncomming air. Because air is a fluid medium these two angles often don't match, such as when landing, taking off, or making a sudden change in attitude. Every aircraft has a Critical AoA at which it will stall, which is why a high performance aircraft can stall at a high speed. I hope this is a somewhat intelligable explation LOL.David

<>Any aircraft can stall at any speed and at any orientation of the fusilage relative to the ground. Some experts suggest that AOA indicators ought to be standard on all aircraft and with as many stall/spin fatalities as occur every year, they may well be correct.The stall warning horn clearly does not prevent stall/spins because the transition between a flying wing and a stalled wing can happen very quickly and by the time you have reacted to the horn, you are already in a spin.The AOA indicator depicts a TREND toward a stall and therefore, could be very useful but unfortunately, they are not likely to ever be routinely installed.

>Any aircraft can stall at any speed and at any orientation of the fusilage relative to the ground.

AoA indicators are not installed because most aircraft have no use for one and in most cases would just make the pilot's job more difficult as there would be another set of numbers to remeber. They maybe useful for aerobatic and fighters who need to hold the edge of the stall for prolonged periods. Where a particular design has certain characteristics that lead to virtually no warning between unstalled flight and prehaps a viscous wing drop the UK (and I imagime all authorities) CAA require cirtain additions to the systems to warn of a possible stall. Stick shakers are one, I imagine in some cases for light aircraft an AoA could be required for a CofA although I haven't heard of such a thing.Airliners are another matter, swept wings being particuarly nasty in a stall (often resulting in a pitch up exacerbating the problem!!). All airliners have stick shakers that announce a near stall (1.05*Vs) from a combination of AoA sensor information and flap/slat configuration. The reason the flap/slats configuration is important is that the critical alhpa of the wing reduces with flap extension and increases with slat extension, imagine trying to remeber all those AoA angles for the various stages...on approach...in bad weather...with one engine...

http://www.airliners.net/open.file?id=4776...atic=yes&size=MAbove the Yoke and to the left....LearJet panelDavid

Tracy v. Gates Learjet Corp. Crash of Learjet 23 during take-off. Prosecuted against Learjet for dangerous stall characteristics and inadequate stall warning, resulting in recovery for plaintiff.

<>Quite a number of experts would disagree with you and the nearly shocking number of stall/spin fatalities, year in and year out, speak eloquently to the fact that angle of attack is one of the most poorly understood aspects of aerodynamics.In addition to the life saving aspects of an aoa indicator, they would also greatly improve normal landings for many pilots who just don't execute their flairs properly. There are quite a few nearly useless guages on light airplanes that could be appropriate places for aoa indicators...ADFs for example.In addition, an aoa indicator can be invaluable in trougleshooting rigging problems that often go entirely unnoticed and cause various ineffeciencies that, if corrected, would probably pay for the gauge over time.Don't get me wrong, I realize there is a zero chance that aoa's will be adopted in the fleet but that is largely because so many pilots don't fully understand aoa in the first place...and come to grief because of it.Regards

Right. That's why the aoa guage was added. And in the classic, "base to final, cross control, stall/spin" scenario, clealy those who get themselves into the stall/spin area of the envelope don't sit there and disregard a blaring stall horn. It happens too quickly. The horn blares and the are on their backs in a heartbeat.Regards