Guess I'm outta the loop ?

[jaybee]

I admit, with all my helichopper flying its probably been over a year since I've even been in an airplane...

anyhow... what is all the fuss lately about AOA indicators ?

do they not teach stall recognition/recovery anymore ?

 

[Velocity173]

I admit, with all my helichopper flying its probably been over a year since I've even been in an airplane...

anyhow... what is all the fuss lately about AOA indicators ?

do they not teach stall recognition/recovery anymore ?

I've wondered the same thing. My Glasair isn't as forgiving as a typical certified and I have no stall horn/light or AOA. It's called knowing your aircraft and recognizing what particular flight profile you're in.

The thing that most of these stall horn & AOA proponents fail to grasp is the panic factor. Stall spin accidents have been happening for decades with awareness devices alerting the pilot. You can bet these things were blaring away while the pilots were spinning the aircraft in. I don't know how many times I've read about OSH and Sun Fun arrivals spinning in because they were distracted in the pattern. They had warning of the impending stall, they just ignored it. When people panic, the urge to keep pulling to miss the ground sometimes overrides the need to lower the nose and keep flying. The Colgan accident proved that even with a stick shaker, pilots can sometimes disregard what the aircraft is telling them.

 

[timwinters]

This is going to get interesting.

 

[jaybee]

No reason for 14 year old girl drama, it was a serious question.

I guess what really prompted it was the St Barth thread and the guy that was emphatically worried about the chirping of the stall horn. Someone else was talking about AoA indicator (which I've seen mentioned a few more times lately).

I just remember asking my primary instructor why we take it all the way to stall instead of recovering at the sound of the horn. He said "not all aircraft have horns".

 

[ClimbnSink]

Yeah might as well send texts to teenagers while they are driving to remind them to pay attention to the road.

 

[poadeleted20]

I'm guessing that the "recent fuss" stems from the FAA's announcement last week that they are streamlining the approval process for AOA indicator systems so they can be less expensive to purchase and install. The new policy may be found here.

There is no question that an AOA indicator can be an invaluable aid to the pilot for determining best approach, climb, cruise, and range speeds, best turn performance , and to help warn of an impending stall. The expense and complexity of such installations due to regulatory requirements has been a barrier to putting them in light planes, and the recent change may help ease that burden.

 

[timwinters]

No reason for 14 year old girl drama, it was a serious question.

Well, except that's what happens to 75% of the threads here. That's why the "ignore thread" feature comes in so handy.

I don't have an AoA but I can definitely see one being a very useful tool especially for nailing the approach speeds during short field operations. And AoA would eliminate the need for going through a bunch of mental math (which would still be less accurate).

I'd like to have one since fly in/out of short fields (<1800') regularly. But I don't, and I manage. It's just another tool.

 

[Geico266]

I had one in an RV -9a I owned for a short time. Extremely accurate and repeatable results. I used it to fly into and out of a 1200' strip dozens of time.

 

[Blackhawk]

AOA indicators are very good for giving a pilot more accurate information on AOA than an airspeed indicator. A good example, most POH/AFM/PIMs only have one airspeed for approach, an airspeed based upon maximum gross weight. While this speed will work for a 5000' strip, you start getting into shorter airports or operating at high DA's and the speed can be quite excessive. An AOA can help a pilot is such a scenario.

 

[Velocity173]

Ok so it sounds like this device is used to fly as close as possible to critical AOA while conducting a short field landing. Couldn't one do the same thing with a stall horn? You note the airspeed the horn/light comes on during final and then ride that airspeed all the way down. We're looking at maybe a couple knot difference in technique.

 

[timwinters]

I don't think my stall warning would go off at the proper short field approach speed, unless it's so short that I'm dragging it in behind the power curve, which I've done, and yes, it's blaring then!

A good example, most POH/AFM/PIMs only have one airspeed for approach, an airspeed based upon maximum gross weight. While this speed will work for a 5000' strip, you start getting into shorter airports or operating at high DA's and the speed can be quite excessive. An AOA can help a pilot is such a scenario.

I put together the attached spreadsheet and have it taped to the back of one of my clipboards. It's an easy quick reference (after some quick mental math to determine weight). It'll get me pretty close but an AoA would still be far superior.

 

[poadeleted20]

Ok so it sounds like this device is used to fly as close as possible to critical AOA while conducting a short field landing.

Not quite. It is used to nail the correct AOA for the operation, not "as close as possible to critical [stalling] AOA". A properly adjusted stall horn will not normally be sounding at proper short-field approach speed. Stall horns typically sound off 5-10 knots above stall, and best short-field approach speed usually isn't in that range. Further, even if it were that way, the best airspeed for that varies with weight, but the best AoA does not. With an AoA gauge, you don't have to compute the change in speed off the book recommended value for less than max gross weight -- just nail the correct AoA regardless of actual weight.

Further, it will do the same for best range glide speed, best endurance speed, max range cruise, Vy, Vx, etc. Makes it a lot easier to fly the plane for any desired performance parameter.

 

[Velocity173]

Not quite. It is used to nail the correct AOA for the operation, not "as close as possible to critical [stalling] AOA". A properly adjusted stall horn will not normally be sounding at proper short-field approach speed. Stall horns typically sound off 5-10 knots above stall, and best short-field approach speed usually isn't in that range. Further, even if it were that way, the best airspeed for that varies with weight, but the best AoA does not. With an AoA gauge, you don't have to compute the change in speed off the book recommended value for less than max gross weight -- just nail the correct AoA regardless of actual weight.

Further, it will do the same for best range glide speed, best endurance speed, max range cruise, Vy, Vx, etc. Makes it a lot easier to fly the plane for any desired performance parameter.

So my AA-5 manual shows a 61 kt approach speed for a short field landing. If I make no adjustment to that based on weight are you saying that will be a significant difference from the correct AOA for the approach? Would I not still be in the "green donut" area at 61 kts?

 

[poadeleted20]

So my AA-5 manual shows a 61 kt approach speed for a short field landing. If I make no adjustment to that based on weight are you saying that will be a significant difference from the correct AOA for the approach?

Yes, about 1 knot for every 100 lb below max gross. If you fly that AA-5 with two aboard and half tanks, you'll be about 4 knots fast at 61 knots, and that's a lot of extra energy when you start the flare.

Would I not still be in the "green donut" area at 61 kts?

Not if you're as light as I suggested.

BTW, the doughnut was amber, not green (the "slow" chevron was green and the "fast" chevron red) in the fighter types I was in, although I know of no FAA standard on that point, so I guess you could color them any way you want if you were building one today for light civilian planes.

 

[txflyer]

The way you calibrate the Alpha systems AOA is to fly slow flight, no flaps, level and not losing or gaining any altitude. This is your optimum alpha angle set point. So when you're coming in with flaps, you have gobs of lift reserve.

The AOA or LRI (lift reserve indicator) see's lift. It doesn't care about density altitude, weight, speed, wind, or technique.

Some landings in our 180 can be so slow that the ASI is useless. The AOA continue's to work at those slower speeds. If you do really short fields, AOA's are a good tool.

 

[Velocity173]

Yes, about 1 knot for every 100 lb below max gross. If you fly that AA-5 with two aboard and half tanks, you'll be about 4 knots fast at 61 knots, and that's a lot of extra energy when you start the flare.

Not if you're as light as I suggested.

BTW, the doughnut was amber, not green (the "slow" chevron was green and the "fast" chevron red) in the fighter types I was in, although I know of no FAA standard on that point, so I guess you could color them any way you want if you were building one today for light civilian planes.

Ok, looks like I'm going to have to buy one of these and try it out. Sounds like it can make for more precise flying. I don't think it'll actually keep me from getting into a spin but might help me fly a specific profile better. Now, just have to justify the price compared to the type of flying I do.

 

[Anymouse]

BTW, the doughnut was amber, not green (the "slow" chevron was green and the "fast" chevron red) in the fighter types I was in, although I know of no FAA standard on that point, so I guess you could color them any way you want if you were building one today for light civilian planes.

I'm guessing he's referencing one of the more popular AOA's.

http://advanced-flight-systems.com/Products/AOA/aoa.html

 

[poadeleted20]

Ok, looks like I'm going to have to buy one of these and try it out. Sounds like it can make for more precise flying.

Absolutely!

I don't think it'll actually keep me from getting into a spin but might help me fly a specific profile better.

Exactly.

Now, just have to justify the price compared to the type of flying I do.

I believe some are available for around $600 plus installation, and we don't yet know what's going to become available under the FAA's new policy. Might be worth waiting to see about that.

 

[poadeleted20]

I'm guessing he's referencing one of the more popular AOA's.

http://advanced-flight-systems.com/Products/AOA/aoa.html

Got it.

 

[Jimmy cooper]

I've seen and done some amazing short field landings in a Stearman, champ, mooney without the aid of one. I've seen some pilots , high time in Mooneys do amazing short field landings, not to mention a fellow named bill newnam , former corsair pilot , and former long time FBO of easton maryland! now deceased , throw a shrike commander around like a cub! short field landings! take offs! etc. I stress high time in type in each case. Their aoa was built into their body where they sat, plus many hours as a pilot and in type.

 

[Jim Logajan]

I've wondered the same thing. My Glasair isn't as forgiving as a typical certified and I have no stall horn/light or AOA. It's called knowing your aircraft and recognizing what particular flight profile you're in.

The thing that most of these stall horn & AOA proponents fail to grasp is the panic factor. Stall spin accidents have been happening for decades with awareness devices alerting the pilot.

Disagree with the basic assumption: that AOA is only solving stall-spin.

AOA should help reduce runway loss-of-control (RLOC) accidents, not just stall-spin. The problem is that the average low time pilot is likely going to err on the side of landing too fast than too slow, which ends up yielding more landing accidents.

The average pilot who rents a plane is also unlikely to be able to fly a lot of hours like a Glasair owner can, so is forever handicapped by lack of flight time and aircraft "feel". AOA is a good thing for those fliers.

Lastly, since you have no instruments telling you how often you have approached stall during your approaches, or whether you have been landing faster than you need to, there is nothing other than your simple survival to date to indicate whether you have been just plain lucky or have achieved experienced uber-pilot status. In neither case is your anecdote relevant to the value of AOA indicators to the general pilot population.

 

[Velocity173]

Disagree with the basic assumption: that AOA is only solving stall-spin.

AOA should help reduce runway loss-of-control (RLOC) accidents, not just stall-spin. The problem is that the average low time pilot is likely going to err on the side of landing too fast than too slow, which ends up yielding more landing accidents.

The average pilot who rents a plane is also unlikely to be able to fly a lot of hours like a Glasair owner can, so is forever handicapped by lack of flight time and aircraft "feel". AOA is a good thing for those fliers.

Lastly, since you have no instruments telling you how often you have approached stall during your approaches, or whether you have been landing faster than you need to, there is nothing other than your simple survival to date to indicate whether you have been just plain lucky or have achieved experienced uber-pilot status. In neither case is your anecdote relevant to the value of AOA indicators to the general pilot population.

If a pilot has a RLOC or a bounced landing it's not because of lack of an AOA indicator, it's because they weren't even flying the POHs approach speed to begin with. If they have an AOA and don't follow it, the same thing will happen. If a pilot is flying the book speed, the few knots of difference between that and a proper AOA, isn't going to be either making the runway length or going off the end. There are other important factors (wind, DA, braking action, touch down point) then simply getting the correct AOA for an approach. Sometimes we simply try and force an aircraft to produce a landing that it's just not capable of.

I know when I'm approaching stall in my Glasair due to the "burble" I feel just prior to stall. I don't need a horn, light or AOA to tell me that I need to relax the stick to continue flying. I've done arrival, departure and accelerated stalls in it and all were predictable and easily recoverable if coordinated. There are no surprises if you're intimately familiar with your aircraft. In the Glasair, that means an appreciation for high wing loading and the importance of maintaining proper airspeed.

I suppose with an AOA indicator I could reduce my rollout by a couple hundred feet or save a pint of gas by flying the proper cruise AOA but I'm not sure it's worth the money to install right now.

 

[tehmightypirate]

I put together the attached spreadsheet and have it taped to the back of one of my clipboards. It's an easy quick reference (after some quick mental math to determine weight). It'll get me pretty close but an AoA would still be far superior.

Mind sharing the actual Excel file. I'd love to work up one for the 172 I fly but figure why reinvent the wheel when you have it 90% done.

 

[jaybee]

Thanks for all the well detailed answers, very appreciated. It sounds like a useful tool.

 

[poadeleted20]

If a pilot has a RLOC or a bounced landing it's not because of lack of an AOA indicator, it's because they weren't even flying the POHs approach speed to begin with.

The problem with POH approach speeds is a) they are normally only printed for max gross weight, and 2) they are often tempered by concerns for liability (e.g., Cessna printing 65-70 KIAS in 172 with flaps as far as full in an apparent effort to ensure nobody stalls on final). IOW, if you fly the Cessna 172 POH airspeeds with a typical 2-people/partial fuel/no bags load, you're way too bloody fast. With an AoA indicator, you just fly the correct AoA and speed takes care of itself without further calculation.

 

[Velocity173]

The problem with POH approach speeds is a) they are normally only printed for max gross weight, and 2) they are often tempered by concerns for liability (e.g., Cessna printing 65-70 KIAS in 172 with flaps as far as full in an apparent effort to ensure nobody stalls on final). IOW, if you fly the Cessna 172 POH airspeeds with a typical 2-people/partial fuel/no bags load, you're way too bloody fast. With an AoA indicator, you just fly the correct AoA and speed takes care of itself without further calculation.

I agree. I got checked out in a C-172 once. After check out I went to practice some approaches with just me on board and light on fuel. I was slightly fast on approach and bounced it three times before doing a go around.

I know when had my Traveler, I bounced it a couple times and it was only when I was slightly fast on approach. Definitely don't want to hit the nose gear on that aircraft!

In the Glasair, high speed on final isn't an issue. I've touched down fast (70kts) before and it never bounced me up. It's actually quite forgiving and the fiberglass gear is quite strong. I suppose one of the few selling points of the aircraft.

 

[bluerooster]

The Yankee we had liked a relatively fast approach speed (compared to 172, or PA-28-140)
An AOA would probably help considerably in that little bundle of fun.

 

[poadeleted20]

The Yankee we had liked a relatively fast approach speed (compared to 172, or PA-28-140)

If you're speaking of one of the original 1969-70 AA-1's, that is true -- radically different airfoil than other light planes of its time. If you're speaking of a 1971-79 AA-1A/1B/1C, that is not true, and many of those have been damaged by ill-informed/misinformed people trying to fly them at AA-1 speeds on final.

An AOA would probably help considerably in that little bundle of fun.

It would certainly end the confusion over what speed to fly on final in a 2-seat Grumman -- just put it "on speed" by the AoA indexer and keep it there.