I'm trying to figure out how I'd like to configure the panel of a new LSA aircraft (likely a Highlander or Bush Caddy) that I'm hoping to use in STOL-type operations. I'd appreciate hearing comments concerning the advisability of including an angle of attack indicator (whether a stand-alone unit of as part of a glass display). I am suprised that they do not seem to be in greater use. Thanks very much.

Well I've never flown with an AoA indicator so I don't want to misinform. However, for minimum distance landings where AoA management is critical I take my last look at the ASI when 'established' on final and never look at it again. I let the stick, what I feel, and what I see outside the window tell me what inputs I need. If you're really operating at your limit or your aircraft's limit then I can't see how one has time to look inside, focus on the indicator, digest the information, look back outside, refocus and then do what you think you should do given this new information.

For the more benign cases, where you have lots of runway, you never really need that info anyhow because you build in a cushion well above the limit.

I could be missing the wonders of an AoA indicator but I would think that the money you spend on it would be better spent on gas, feeling out the limits of you aircraft, low and slow over a runway.

AOA is GREAT information, when it's gathered by accurate sensors. Many military fighter aircraft have very sophisticated AOA information available.

The problem with light GA type airplanes and AOA is that AOA really isn't very precise in these little airplanes, which, as Jimmy accurately noted, you can FEEL what the airplane is doing much more accurately than the very simple AOA systems available can tell you.

Consider that the AOA sensor is almost always located well out on a wing. It may in fact, offer reasonably accurate information on the AOA of that segment of that wing, but the rest of that wing, and the other wing may be at a very different AOA.

We put one of the most commonly advertised AOA units on a Cessna 185 (public aircraft, so we didn't ask the blessing of the FAA-but these things are NOT approved on any light GA aircraft). Several pilots flew that airplane quite a bit, and none of us liked the thing, or believed it provided any better information than A/S or our butts.

The company that makes these things will tell you that you can get a field approval (not required for an experimental, of course) for their product. Good luck. They'll also tell you you can install them as a "minor installation". Again, good luck if an FAA person ever looks at it.

I've asked them "If these things are THE answer to the stall/spin accident potential in this country, as the company claims, why don't you STC them?" Their answer at times has been that you don't need an stc, and at others that it's too much hassle and expense to get an stc. There's no doubt the latter is true, but again, if these things were really God's gift to GA, they should sell like hot cakes. They don't go for an STC probably because they wouldn't be able to get an STC without substantially improving the raw data being gathered.

MTV

AOA,

Well....they were in use on all the airplanes that I flew commercially. Nice "warning/trend" devices for heavy/fast/military/commercial airplanes that provide less 'seat of the pants' feel. Never flew a GA airplane with one installed until a month ago. It was on a Maule M-5-180 which I flew for 21 hours, including time at it's operating limits. The AOA indicator provided information which supported my seat of pants experience in type.

Normally when operationg my M-5-210-C at it's raggedy edge....I fly with the stall warning light just turning red.(no horn installed) The AOA indicator on the subject Maule would show the needle just in the edge of the RED limit area: exactly in agreement with my butt and the stall warning light. If you are familiar with your aircraft, it's abilitys and the seat of your pants, which you certainly should be or become....I see no advantage to the AOA indicator. It just confirmed what I already knew.

Bob

thanks very much, guys....

How does your seat of the pants feel when approaching high speed or high g stalls? If you need to make a quick and critical minimum radius turn, like in a canyon, the AOA could save you. It is like operating with the stall warning. They both are looking at angle of attack. In some cases airspeed indication is useless. I guess my seat is not very sensitive. I would not bet my life on my seat of the pants. I need all the help I can get.

flyer

I'll chime in here...I am no expert but I have the AOA option on my Kitfox 7 through my Dynon D100. I don't have a typical stall warning so this was my only option for stall warning. In the case of the Dynon, you actually calibrate it based on a series of stalls you do and the data is then saved in the EFIS. You can then set an audible alarm on the AOA to begin at the bottom, middle or top of the yellow or just at the bottom of the red. As the AOA of your wing increases, the alarm gets louder so if you know where it is set then you don't have to look in the airplane at all, you can simply go on the sound just like a stall warning in a certified aircraft. My understanding is that AOA is more reliable than an airspeed system as it will tell you if your are close to a g-induced stall or highspeed stall.

If it's audible, as in Darinh's, case then it might be a nice to have - I can see how that would be a lot more useful than one you have to look at.
I do think you need some sort of audible stall warning though ... not for the ragged edge stuff but for the when you're doing 'nothing' and decide to adjust your boxers and are taken aback by the fact that you're wearing the blue ones when you were absolutely certain you had the red ones on and ... Jesus, was that the stall alarm ?

Flyer,

Here's the problem with that assertion, when it comes to the simple AOA systems typically installed on small aircraft:

The sensor is typically installed well out on a wing, to be outside the prop thrust, obviously. So, let's say I'm making a canyon turn in a tight spot. When I pull hard in a canyon turn, that inboard wing is going to be going a good bit slower and have a significantly higher angle of attack than the other wing, at a given station.

In the meantime, I'm using FULL POWER to keep the boundary layer of air energized over the INBOARD sections of the wings and over the horizontal tail.

On that 185 I spoke of earlier with an AOA indicator installed, the device was relatively accurate in an unaccelerated stall condition, but in an accelerated condition, particularly one with power, it was VERY inaccurate, and unreliable. I could make a MUCH tighter turn quite safely with the needle well into the red in that airplane. Again, the device was properly calibrated.

MTV

Two cases where AOA can be significantly helpful - aircraft that have see differences in weight between take off and land (dropped ordnance or burned lots of gas) and maneuvering flight. The assumtion is that the information presented is reliable though, so if the current options for light civil aircraft can't consistently do that in all phases of flight, as MTV notes above, I probably wouldn't want one.

Most of the planes folks on this site are fiddling with don't require routine calculations to determine a final approach and landing speed. On aircraft that do require such calculations, AOA is a good cross check tool to verify that you're flying the right speed for your weight - the stall always occurs at the same AOA, it's the speed (that varies with weight) that changes.

In maneuvering flight, AOA can be invaluable in extracting all the performance available to perform a given maneuver. If you're defensive and someone is pulling for a shot on you, you damn well want to be flying your best turn speed - again, the airspeed at which that occurs varies with your fuel state but that performance will always occur at a given AOA value. As someone noted above though, in this regime you are largely head out of the cockpit, so military AOA hardware incorporates aural cueing as well as an indexer that falls in your line of sight (these days generally presented in a HUD).

Someday when I'm bopping around in my dream C180 I might consider adding an AOA gauge, but only after I had every other must-have bell and whistle in the panel and I'd still come in so light in my empty weight that I didn't know what to do with all the useful load. Until then, I'll just pull to tickle the stall horn when making a tight turn and fly 1.1 Vso when I want to get in short.

Good expanded discussion on final approach speeds here...
http://www.swaviator.com/html/issueJA05/BasicsJA05.html

Just fly the plane using all your senses, that is without a doubt the best way to arrive in one piece. The best analagy I can find is the new option they advertise on TV.. One of those furren cars has a auto braking system for city driving, it is a matter of time when someone sues them because she was putting on lipstick, drinking a latte and chattin on the phone and god forbid she rammed the car in front because the auto braking system didn't "get er done",,,, Had to be the cars fault If you need bells and whistles and needles to make a short approach you probably shouldn't be there in the first place............. YMMV .IMHO etc.

Ben

Sparky put one on his old 180. It didn't change my mind, but interesting reading anyway.

http://www.mountainflying.com/Pages/art ... s_aoa.html

Just tape a piece of yarn to the strut about a foot in from the outboard attach point. Lay down some making tape on the wing skin from fore to aft directly above it, and make some index marks with a sharpee. Go fly a really low speed approach or do some power on stalls and mentally mark that reading on your new ghetto AOA indicator.

I just go by when my wife starts grabbing the handle on the door post. Oh wait, she does that on every approach.

I have and recommend this stand alone unit.
www.liftreserve.com

GARYH wrote:I have and recommend this stand alone unit.
http://www.liftreserve.com

Got one in my 182 and it works great ! Simple install ,couple of hours but well worth it. Like a very sensitive ROC, Airspeed in single unit. Mine is the LRI unit with no electrical stuff. Used it for the last 7-8 years and it's paid for itself many times over. I just wish I had the heated version . Just set up unit and go fly ! I set my approach speed by the White/red line intersection and touchdown speeds will be in mid-high 40's or low 50's. With full flaps 200ft roll
outs are easy to a full stop. At 5,000 Density Altitude full stop in under 300 ft. from touchdown. And at 7,000 Density Altitude try 500 ft. roll outs to stop,
All under complete control. Having a SPORTSMAN STOL 182 does wonders ! YMMV.

I have a Lift Reserve Indicator installed on my PA-28-140 and I like it very much. You can read an article about the LRI on wikipedia here:
http://en.wikipedia.org/wiki/Airspeed_i ... _Indicator

I chose the LRI over an AOA meter for these reasons:
The LRI is fully self contained and is sensing air-powered and can be installed in certified aircraft.
It can be installed without a 337 provided that no other systems or structures are altered. No electric, not pito-static, no structural holes.
The LRI encompasses both AOA and Impact pressure to drive the readout and thus provides the pilot with more than just AOA information.
Once installed, and adjusted by the pilot, the LRI accurately measures the Potential of Wing Lift above the stall at all times and all flight conditions.
The LRI is spring-loaded towards the stall, and is more sensitive the closer to the stall you are flying.

One of the posts pointed out that mounting an AOA sensor far out on the wing could give false information during critical maneuvers. Mine is mounted at the left wingtip and works very well. I have been able to do steep slow turns below the white arc without any trouble. Any control input that changes AOA is displayed immediately. I have also climbed with two people and 2/3 fuel at 40 MPH, but the warmer it gets, the less reserve power I have and the less likely my airplane can stay on the low end of the LRI during high AOA climbs. My Cherokee 140 just doesn't have that kind of power when it gets hot outside. But when it is cool? I have me a little HOT ROD!

Using the LRI well to those real short landings takes a lot of practice, and I get rusty with it if I don't fly a lot. Take-offs are another story. While you can climb out from the center of white arc, I found out that I need to be rolling in the green before lift-off or the aircraft might not fly out of ground effect. One notch in the green is plenty for pulling into the white, but I found I can initiate a good postive steep climb by just holding and maintaining the green/white edge on the takeoff roll. When I am 100 ft over the trees I lower the nose and add airspeed, which by this time is around 40. I know I could experiment and get better, but I've been having too much fun to get that serious. Our Airport is at 85 feet and is 2940 feet long. On a 40F day I can make 1000AGL before crossing the end of the runway! I have done it!

I hope this helps. Pete