What I do is to take my new airplane up to a safe altitude & do some power-off full-flap (aka approach) stalls, at the normal flying weight. Then I try different approach speeds, based on & keeping in mind that stall speed. Add a little airspeed when heavily loaded, take away a whisker when light.

It's my understanding that you have to go out and do some stalls to calibrate an AOA system anyway-- why not just note the indicated airspeeds & skip the middleman by working with those. After you get a handle on the most effective airspeed(s), you end up pretty much flying it by feel anyway like MTV says.

Here's a quote from a C180 pirep in the May 1977 issue of Plane & Pilot:
"....equipped with an angle of attack indicator. Bob put one in at the top left of the panel and used it considerably at first, but then found he was by habit frequently crosschecking with the airspeed indicator. By now, it's a seat-of-the-pants feeling, and the AOA indicator is referenced infrequently". I suspect this is how it goes for most people who install these things.

I'm still geeking out that you bought a Wilga! Grats!

I love mine!

mtv wrote:1) The sensor: Every one of the sensors I've seen on these things look mysteriously like a pitot/static head for experimental aircraft from Aircraft Spruce, and remarkably similar to the pitot/static head of a Piper Warrior. In other words, the things are "measuring" the AOA based on almost exactly the same data that's being fed into an airspeed instrument. Essentially, you're now using lights instead of a dial to suggest AOA. Maybe.

Actually, there are two main categories- vane type and pressure probe type. Both are present in various forms on both GA and other aircraft. It is easy to measure angle of attack at low (<M0.6 or so) using either method, and easier with vane types above that.

mtv wrote:2) Mounting location of the sensor: These are without exception mounted assymetrically on the airframe, as in out on a wing. For obvious reasons, the most obvious being a propeller. Nevertheless, our wings are not always moving at the same speed, nor are they always at the same AOA in regular flight regimes. Now, maybe this difference between wings isn't enough to make a big difference, BUT every sophisticated AOA sensor system I've seen includes a means of measuring AOA of each wing and averaging.

Most AOA systems are installed on the fuselage for heavier aircraft. Dual AOA systems are usually for redundancy, and are pretty rare except on a few military aircraft. Even fewer installed systems are intended to measure the AOA of each wing individually. Doing so would yield more accurate information to be sure, but the practical usability is small given that, even in a really tight turn in a GA plane, the difference in AOA of the nominal chord between the inside and outside wing is generally well under a degree. The thinking is that if you are that close to a stall in a normal airplane, you are close enough to a stall to take action with a single point AOA.

mtv wrote:All of which suggests to me that we can do just as well with an A/S indicator, or better yet with our butts than one of these things can do.

The AOA is another tool for learning to make consistent approaches. Not that it matters- the airspeed is just fine for us bug smashers. The change in stall speed from light weight to gross in most airplanes is on the order of just a couple to a few percent. Airspeed is more delayed than most AOA systems, but again, it is not a big deal for most people flying light airplanes.

mtv wrote:The F/A 18 has a real AOA system.

The GA systems work fine as well.

I designed, built, and sold a pressure type AOA sensor for multiple aircraft. The install is easy, is battery powered, and merely screws on to the nav light sconce, and communicates via Bluetooth. The unit, like most AOA's, is accurate when compared head to head with vane type instruments. I had wanted to market them, but rapidly came to the conclusion that I, like most people who tried them, eventually decided they were not very useful for most small GA planes for most pilots. Those that did find them meaningful were more apt to be looking for something to burn a $2000-$4000 hole in their pocket than were seeking something truly indispensable...and a $200 unit that did the same thing did not fill that intangible need. The people that truly find them useful are students and short field enthusiasts, and these are too few and far between to create a low-end market.

lesuther wrote:

mtv wrote:1) The sensor: Every one of the sensors I've seen on these things look mysteriously like a pitot/static head for experimental aircraft from Aircraft Spruce, and remarkably similar to the pitot/static head of a Piper Warrior. In other words, the things are "measuring" the AOA based on almost exactly the same data that's being fed into an airspeed instrument. Essentially, you're now using lights instead of a dial to suggest AOA. Maybe.

Actually, there are two main categories- vane type and pressure probe type. Both are present in various forms on both GA and other aircraft. It is easy to measure angle of attack at low (<M0.6 or so) using either method, and easier with vane types above that.

mtv wrote:2) Mounting location of the sensor: These are without exception mounted assymetrically on the airframe, as in out on a wing. For obvious reasons, the most obvious being a propeller. Nevertheless, our wings are not always moving at the same speed, nor are they always at the same AOA in regular flight regimes. Now, maybe this difference between wings isn't enough to make a big difference, BUT every sophisticated AOA sensor system I've seen includes a means of measuring AOA of each wing and averaging.

Most AOA systems are installed on the fuselage for heavier aircraft. Dual AOA systems are usually for redundancy, and are pretty rare except on a few military aircraft. Even fewer installed systems are intended to measure the AOA of each wing individually. Doing so would yield more accurate information to be sure, but the practical usability is small given that, even in a really tight turn in a GA plane, the difference in AOA of the nominal chord between the inside and outside wing is generally well under a degree. The thinking is that if you are that close to a stall in a normal airplane, you are close enough to a stall to take action with a single point AOA.

mtv wrote:All of which suggests to me that we can do just as well with an A/S indicator, or better yet with our butts than one of these things can do.

The AOA is another tool for learning to make consistent approaches. Not that it matters- the airspeed is just fine for us bug smashers. The change in stall speed from light weight to gross in most airplanes is on the order of just a couple to a few percent. Airspeed is more delayed than most AOA systems, but again, it is not a big deal for most people flying light airplanes.

mtv wrote:The F/A 18 has a real AOA system.

The GA systems work fine as well.

I designed, built, and sold a pressure type AOA sensor for multiple aircraft. The install is easy, is battery powered, and merely screws on to the nav light sconce, and communicates via Bluetooth. The unit, like most AOA's, is accurate when compared head to head with vane type instruments. I had wanted to market them, but rapidly came to the conclusion that I, like most people who tried them, eventually decided they were not very useful for most small GA planes for most pilots. Those that did find them meaningful were more apt to be looking for something to burn a $2000-$4000 hole in their pocket than were seeking something truly indispensable...and a $200 unit that did the same thing did not fill that intangible need. The people that truly find them useful are students and short field enthusiasts, and these are too few and far between to create a low-end market.

Interesting feedback, thanks.

MTV

mtv wrote:Okay, you're seeing and flying with "real" AOA systems. Before you jump on one of these "general aviation AOA indicators", take a good look at:

1) The sensor: Every one of the sensors I've seen on these things look mysteriously like a pitot/static head for experimental aircraft from Aircraft Spruce, and remarkably similar to the pitot/static head of a Piper Warrior. In other words, the things are "measuring" the AOA based on almost exactly the same data that's being fed into an airspeed instrument. Essentially, you're now using lights instead of a dial to suggest AOA. Maybe.

2) Mounting location of the sensor: These are without exception mounted assymetrically on the airframe, as in out on a wing. For obvious reasons, the most obvious being a propeller. Nevertheless, our wings are not always moving at the same speed, nor are they always at the same AOA in regular flight regimes. Now, maybe this difference between wings isn't enough to make a big difference, BUT every sophisticated AOA sensor system I've seen includes a means of measuring AOA of each wing and averaging.

After all, a spin is a flight regime where one wing has a greater AOA than the other. So, again, I'm assuming that these "AOA systems" for GA figure this into their algorithms (or whatever voodoo they claim to use) and actually INDICATE a slightly higher AOA than the wing actually sees, for saftey's sake.

All of which suggests to me that we can do just as well with an A/S indicator, or better yet with our butts than one of these things can do.

MTV

I am sorry Mike - but I have to disagree with all the above:

Based on what's written above, perhaps there is some confusion about how these things work. They are quite different to an ASI as has been pointed out. For instance, you can stall an aerobatic aircraft at 200kts if you pull hard enough, and AoA would clearly warn of the onset of such a stall where ASI would not. Same goes for bush planes in tight turns at lower speeds. The net effect is the pilot receives a warning as they approach the stall. It doesn't need to be perfect, its a safety device. It also provides a great reference point to how the wing is performing under different conditions, for example in turbulence and different gross weights.

AOA systems hugely helpful to pilots in times of high workload, and are life saving devices. I have certainly experienced the benefits, personally. Tight turns in restricted spaces are a great example. Everyone is saying they are important for the future of aircraft safety, EAA, FAA, AOPA, etc etc. There is a reason why they are getting popular.

Yes, not all are created equal, and some are a less useful than others. Personally I like to keep eyes outside, so I only like ones with audio warnings - like a progressive stall warning you can receive without looking inside the panel.

Sorry to beat a dead horse.

8GCBC wrote:Opinion: AOA is not needed if you develop your skills (VFR).

Couldn't agree more.

One other thought:

1. As has been suggested, you could spend ten thousand dollars on fuel over year(s), learning how to fly the plane safely close to the edge. But you have to take risks. You are human, you get tired sometimes, distracted, you can make mistakes.

2. Or install an instrument which makes it much easier to fly safely close to the edge, right from the beginning. You spend the hours doing the same stuff as 1. building the same broad base of experience, but with a lot of added safety as you do it. You still get all the benefits of 1. after the time has elapsed, but you've always had a safety net.

Yes, option 1 gets you the expert skills. So does option 2; but keeps you safe while you learn. The old macho attitude "I don't need no stinking safety net" gets you one thing... a hard landing. We see it all the time at work, it's a cultural issue.

2c. YMMV

P.S. I am not suggesting everyone needs one to be safe, nor that flying without one means you are a danger to yourself. What I am saying is, given the choice, there are a lot of good reasons for installing an AoA system - provided it's a quality system.

Battson wrote:.....Everyone is saying they are important for the future of aircraft safety.....

They say that about ADS-B too.

hotrod180 wrote:That is significant.
Your engine upgrade lowers the gross weight? First time I've heard of that, usually it leaves it alone or hopefully increases it. For example, my C150/150TD had a 1760# gross per the STC, vs a 1600# gross stock. Which was good, as it was quite a bit heavier than the normal stock airplane-- 1240 or so empty vs 1100 or so for my first airplane, a stock 1969 C150J.

Yeah, it's an annoying quirk in the conversion STC. The stock P172D had a 2500# gross, but the Avcon conversion not only adds a little to the empty weight (slightly heavier engine, about 35#) but reduces the gross to 2350#. Why, I haven't the slightest clue.

Cary

Cary wrote:

hotrod180 wrote:That is significant.
Your engine upgrade lowers the gross weight? First time I've heard of that, usually it leaves it alone or hopefully increases it. For example, my C150/150TD had a 1760# gross per the STC, vs a 1600# gross stock. Which was good, as it was quite a bit heavier than the normal stock airplane-- 1240 or so empty vs 1100 or so for my first airplane, a stock 1969 C150J.

Yeah, it's an annoying quirk in the conversion STC. The stock P172D had a 2500# gross, but the Avcon conversion not only adds a little to the empty weight (slightly heavier engine, about 35#) but reduces the gross to 2350#. Why, I haven't the slightest clue.

Cary

An IA who lived in Fairbanks at the time got several field approvals to reverse that portion of the STC. Name was Fred Dyen, he's in the lower 48 now, but I don't know where.

MTV

test

mtv wrote:

Cary wrote:

hotrod180 wrote:That is significant.
Your engine upgrade lowers the gross weight? First time I've heard of that, usually it leaves it alone or hopefully increases it. For example, my C150/150TD had a 1760# gross per the STC, vs a 1600# gross stock. Which was good, as it was quite a bit heavier than the normal stock airplane-- 1240 or so empty vs 1100 or so for my first airplane, a stock 1969 C150J.

Yeah, it's an annoying quirk in the conversion STC. The stock P172D had a 2500# gross, but the Avcon conversion not only adds a little to the empty weight (slightly heavier engine, about 35#) but reduces the gross to 2350#. Why, I haven't the slightest clue.

Cary

An IA who lived in Fairbanks at the time got several field approvals to reverse that portion of the STC. Name was Fred Dyen, he's in the lower 48 now, but I don't know where.

MTV

At the elevations I fly, I don't think I'd want to fly much heavier anyway. At a calculated weight near 2350#, there's not a lot of performance above about 11,000' anyway (yeah, it will climb to 14,000' on a good day, but sloooooooooooowly). The only benefit I can see is that if I happened to prang whilst a few pounds over 2350#, I wouldn't be violated for being over weight--just under smart.

Cary

Cary