AOA indicator

On Friday, April 15, 2016 at 8:15:35 AM UTC-7, Dan Marotta wrote:
Feel the force, Luke.

I pulled my 302 and sent it back for the GPS fix. Decided to go flying before it came back and forgot that I hadn't plugged the tubing as soon as I got airborne. So I not only had no audio, but my airspeed showed between 30 and 60 knots maximum due to the pitot leak.

Had a very pleasant XC flight without a single stall or even incipient. And yes, I was thermaling at high AOA, but so what. Maybe because I'm relatively current with 1500 hours in the ASH-26E, it was a complete non event flying by feel, attitude and sound.

I think it might be nice to have AOA to optimize flap settings in the glide and as an extra stall warning, but not as yet another distraction in the cockpit. :-)

5Z

"Stupid instrument, it tells you your angle of attack - if you don't know, you shouldn't be flying". ~ Gen. Chuck Yeager

I liked having an AOA in the Lear60, but it was more useful for high-altitude cruise flight level determination than for pattern work.

I've always been amazed at how underappreciated (and even dismissed) AOA is among pilots. We wouldn't think of flying without an airspeed indicator, and we all stick a piece of yarn (or buy expensive Mk IVs) to see EXACTLY what our yaw is, but ignore the one potential instrument that cab actually tell you, regardless of wingloading, Gs, bank angle, etc., how your wing is doing - and how close you are to busting your ass.

Airspeed is nice for setting and cruising at your Mccready speed and for high speed passes, but for just about everything else you do in a glider, what you really care about is your AOA - and unlike IAS it can be easily and unambiguously measured, displayed, and used.

We hear a constant litany about accidents in the landing pattern, stall - spins at low altitude, hard landings, fast landings, etc. ALL are caused by poor AOA control due to trying to use the ASI to manage what your glider is doing. Sure it can be done, but it really isn't the best way. And pilots die all the time because of that misuse of instrumentation.

The interesting little video of a simulation of an F-4 AOA tone is fun, but totally fails to convey just how easy it is to use a properly designed system. Imagine flying your pattern, or winch launching, while keeping your eyes outside the cockpit 100% of the time and still knowing your AOA (or desired airspeed, if you wish) within a knot or two of the ideal, regardless of how much ballast you loaded or your passenger weighs, or how steep you are banking to save that overshot final... That was state of the art back in, oh, 1962?

But hey, if Chuck Y thinks an AOA gauge is stupid, who are we to argue... (although I would prefer to hear Bob Hoover's opinion on the matter...)

Me, I would have a simple AOA aural system tied to the gear - gear down, AOA tones are on (slow beep at 1.5Vs, for example, increasing to a steady tone at 1.3Vs or yellow triangle, then a faster "sink" tone when approaching stall AOA). Gear up, a simple AOA indicator (slow-min sink/CLmax-fast lights) for thermalling.

Not holding my breath, tho ;^)

Kirk
66

On Saturday, April 16, 2016 at 6:02:57 AM UTC+12, kirk.stant wrote:
I've always been amazed at how underappreciated (and even dismissed) AOA is among pilots. We wouldn't think of flying without an airspeed indicator, and we all stick a piece of yarn (or buy expensive Mk IVs) to see EXACTLY what our yaw is, but ignore the one potential instrument that cab actually tell you, regardless of wingloading, Gs, bank angle, etc., how your wing is doing - and how close you are to busting your ass.

Airspeed is nice for setting and cruising at your Mccready speed and for high speed passes, but for just about everything else you do in a glider, what you really care about is your AOA - and unlike IAS it can be easily and unambiguously measured, displayed, and used.

We hear a constant litany about accidents in the landing pattern, stall - spins at low altitude, hard landings, fast landings, etc. ALL are caused by poor AOA control due to trying to use the ASI to manage what your glider is doing. Sure it can be done, but it really isn't the best way. And pilots die all the time because of that misuse of instrumentation.

The interesting little video of a simulation of an F-4 AOA tone is fun, but totally fails to convey just how easy it is to use a properly designed system. Imagine flying your pattern, or winch launching, while keeping your eyes outside the cockpit 100% of the time and still knowing your AOA (or desired airspeed, if you wish) within a knot or two of the ideal, regardless of how much ballast you loaded or your passenger weighs, or how steep you are banking to save that overshot final... That was state of the art back in, oh, 1962?

But hey, if Chuck Y thinks an AOA gauge is stupid, who are we to argue... (although I would prefer to hear Bob Hoover's opinion on the matter...)

Me, I would have a simple AOA aural system tied to the gear - gear down, AOA tones are on (slow beep at 1.5Vs, for example, increasing to a steady tone at 1.3Vs or yellow triangle, then a faster "sink" tone when approaching stall AOA). Gear up, a simple AOA indicator (slow-min sink/CLmax-fast lights) for thermalling.

"We wouldn't think of flying without an airspeed indicator".

But it's not that difficult. We expect students to be able to make a safe flight and landing will all instruments "failed" (covered) before they fly solo.

I completely agree that AOA is *the* prime thing you want to know, and it would be nice to have an instrument for it. However, the stick position is a pretty good proxy for it, I think.

e.g. winch launch failure? There's no need to shove the stick hard forward (in fact this can cause the wings to stall in -ve AOA). Leaving it in the middle is fine, no matter how low the airspeed over the top. Just don't pull it back into your stomach in an attempt to stop the nose falling through!

On Friday, April 15, 2016 at 1:26:07 PM UTC-5, Bruce Hoult wrote:

"We wouldn't think of flying without an airspeed indicator".

But it's not that difficult. We expect students to be able to make a safe flight and landing will all instruments "failed" (covered) before they fly solo.

I completely agree that AOA is *the* prime thing you want to know, and it would be nice to have an instrument for it. However, the stick position is a pretty good proxy for it, I think.

e.g. winch launch failure? There's no need to shove the stick hard forward (in fact this can cause the wings to stall in -ve AOA). Leaving it in the middle is fine, no matter how low the airspeed over the top. Just don't pull it back into your stomach in an attempt to stop the nose falling through!

Bruce, I would agree with you (and have flown a 500k without an airspeed indicator or TE vario), but the crash record seems to indicate that it's not that easy!

Airspeed, stick position, wind noise, buffet, stick "feel", these are ALL indirect indications of how the wing is doing. We all learn to compensate for their inaccuracies and limitations, and many of us get really good at flying by "feel", but the penalty for getting it wrong can be pretty severe!

Sure, if you are current, it's easy to "feel the force" as Dan would say; but for a low time or out of practice pilot, perhaps in a strange glider with different speeds and controls than he is used to, and a stressfull situation - the picture is depressingly different. And all the pundits shake their heads and can't imagine how someone could pooch a pattern so badly, or spin out of a thermal...

Cu's out the office window today - hoping for some XC tomorrow - who hoo!

Kirk
66

"Feel the Force" was tongue in cheek, though that doesn't come through
in the printed word.

Yes, I've flown with AoA indexers and think they're the cat's ass, but I
wonder if there's a low drag type of sensor to feed the thing. I can't
imagine sticking a a pair big vanes or probes on the sides of my
fuselage, but I'll bet there's a way to calculate a pseudo-A0A from
gross weight (pilot set during preflight), indicated airspeed,
barometric pressure, temperature, yaw angle, and g-loading. All of the
above are available in the glider (with a modern soaring computer) and
it's incumbent on the pilot to know the gross weight and not screw that
up (or we could have weight sensors on the landing gear). A vertical
tape could be driven by the output of a simple micro computer and
displayed on most of our moving maps or on a multi-colored LED stack
mounted either to the top center of the glare shield or a pair of them
on the left and right sides.

There, I've done the top-level systems engineering. Now, if hardware
and software would step up and get this thing moving...

Cheers!

Dan

On 4/15/2016 12:50 PM, kirk.stant wrote:
On Friday, April 15, 2016 at 1:26:07 PM UTC-5, Bruce Hoult wrote:
"We wouldn't think of flying without an airspeed indicator".

But it's not that difficult. We expect students to be able to make a safe flight and landing will all instruments "failed" (covered) before they fly solo.

I completely agree that AOA is *the* prime thing you want to know, and it would be nice to have an instrument for it. However, the stick position is a pretty good proxy for it, I think.

e.g. winch launch failure? There's no need to shove the stick hard forward (in fact this can cause the wings to stall in -ve AOA). Leaving it in the middle is fine, no matter how low the airspeed over the top. Just don't pull it back into your stomach in an attempt to stop the nose falling through!
Bruce, I would agree with you (and have flown a 500k without an airspeed indicator or TE vario), but the crash record seems to indicate that it's not that easy!

Airspeed, stick position, wind noise, buffet, stick "feel", these are ALL indirect indications of how the wing is doing. We all learn to compensate for their inaccuracies and limitations, and many of us get really good at flying by "feel", but the penalty for getting it wrong can be pretty severe!

Sure, if you are current, it's easy to "feel the force" as Dan would say; but for a low time or out of practice pilot, perhaps in a strange glider with different speeds and controls than he is used to, and a stressfull situation - the picture is depressingly different. And all the pundits shake their heads and can't imagine how someone could pooch a pattern so badly, or spin out of a thermal...

Cu's out the office window today - hoping for some XC tomorrow - who hoo!

Kirk
66

--
Dan, 5J

On Saturday, April 16, 2016 at 8:46:36 AM UTC-7, Dan Marotta wrote:
Yes, I've flown with AoA indexers and think they're the cat's ass,
but I wonder if there's a low drag type of sensor to feed the
thing.* I can't imagine sticking a a pair big vanes or probes on the
sides of my fuselage

A single probe can provide AoA, airspeed, static, and total energy, it just needs more holes and tubing. Better yet, discard the tubing, put all of the electronics and sensors in the probe, send the data to the cockpit via Bluetooth.

A single probe can provide AoA, airspeed, static, and total energy, it just needs more holes and tubing. Better yet, discard the tubing, put all of the electronics and sensors in the probe, send the data to the cockpit via Bluetooth.

While it's true this can be done these days it will require thousands of man-hours of expensive engineering time. You will end up with something like the Garmin AOA system which is like $1400. My idea was to use a very small vane that has negligable drag and low cost electronics with a much lower price to the pilot so that more people will actually own it. This entire discussion has been very helpful to me and am now considering adding the audio tone option for use on landing approach.

Or perhaps you could do it with software as per the original post.

On Sunday, April 17, 2016 at 7:09:28 PM UTC-7, Soartech wrote:
A single probe can provide AoA, airspeed, static, and total energy, it just needs more holes and tubing. Better yet, discard the tubing, put all of the electronics and sensors in the probe, send the data to the cockpit via Bluetooth.

While it's true this can be done these days it will require thousands of man-hours of expensive engineering time. You will end up with something like the Garmin AOA system which is like $1400. My idea was to use a very small vane that has negligable drag and low cost electronics with a much lower price to the pilot so that more people will actually own it. This entire discussion has been very helpful to me and am now considering adding the audio tone option for use on landing approach.

On Sunday, April 17, 2016 at 7:09:28 PM UTC-7, Soartech wrote:
A single probe can provide AoA, airspeed, static, and total energy, it just needs more holes and tubing. Better yet, discard the tubing, put all of the electronics and sensors in the probe, send the data to the cockpit via Bluetooth.

While it's true this can be done these days it will require thousands of man-hours of expensive engineering time. You will end up with something like the Garmin AOA system which is like $1400. My idea was to use a very small vane that has negligable drag and low cost electronics with a much lower price to the pilot so that more people will actually own it. This entire discussion has been very helpful to me and am now considering adding the audio tone option for use on landing approach.

Vanes have their own downsides, in particular being rather fragile. If I was working for Garmin, yes, it would take thousands of man-hours of expensive engineering, but I'm not working for Garmin.

For a 2 hole probe with audio output, I'm not seeing where one needs much more than a couple of high resolution absolute or (preferably) differential i2c pressure sensors, a simple audio amplifier, and a cheap microcontroller with DAC. Easy breadboard project, minimal coding, but I can't design a PCB. Only for experimental gliders, of course...