AOA indicator

[Jonathan St. Cloud]

Was just reading about the Aspen suite of avionics for GA
http://www.flyingmag.com/way-to-aoa?src=PPC&dom=fb&con=Aspen-FB-Ads.
Was wondering if Air-Avionics Butterfly, LX 90XX or similar modern glide computers would be capable of such algorithms to have a working AOA?

[son_of_flubber]

WRT OP's question. I'd guess that Butterfly has the sensor input to compute AOA. I don't know if they have the computation resources to complete the calculation in the real time constraints (but they will in the future generation of chips). I don't think that offering this functionality would increase their revenue. It would increase their costs, in particular their liability costs. Has anyone ever been sued for an inaccurate vario reading?


The video raises other questions:

At :30 in the video "he steepens the bank, stalls and spins, even though the aircraft was well above the published stall speed".

I understand that steeper bank increases load factor and that increases the speed at which critical AOA is reached. What I don't understand is why do power pilots use such low Va (such that an increase in bank commonly causes a stall/spin!).

Is it because the stall speeds are so much higher in a power plane relative to the lengths of the runways? So a power pilot needs to fly slow, close to stall speed, to have an acceptable runout?

I also notice in power flying forums that the notion of increasing Va proportional to wind/gust conditions gets little attention.

I noticed power planes fly slow Va (a low multiple of their stall speed), shallow glide slopes and shallow bank turns. Gliders do the opposite. Why?

I'm curious because I'm planning to take some lessons in a tailwheel power Kitfox, and I'd rather not pay to argue these points with my CFI.

[Per Carlin]

All modern computers has a stall varning algoritm, it doesn't need more than stall speed in strait flight, actual speed and load to calculate if you are above or below stall. With a total pressure sensor and g-meter is the math easy.

It is trickier with unknown variables as load and bugs,that has to be correctly inputted by the pilot.

[Dan Marotta]

The Dynon D10 in my Stemme has an AoA indexer display near the bottom
left corner of the display. I'll have to go up and watch that while I
practice stalls and falls. I'll report back if it actually works.

On 4/8/2016 2:25 PM, Per Carlin wrote:
> All modern computers has a stall varning algoritm, it doesn't need more than stall speed in strait flight, actual speed and load to calculate if you are above or below stall. With a total pressure sensor and g-meter is the math easy.
>
> It is trickier with unknown variables as load and bugs,that has to be correctly inputted by the pilot.

--
Dan, 5J

[SoaringXCellence]

On Friday, April 8, 2016 at 1:17:10 PM UTC-7, son_of_flubber wrote:
> WRT OP's question. I'd guess that Butterfly has the sensor input to compute AOA. I don't know if they have the computation resources to complete the calculation in the real time constraints (but they will in the future generation of chips). I don't think that offering this functionality would increase their revenue. It would increase their costs, in particular their liability costs. Has anyone ever been sued for an inaccurate vario reading?
>
>
> The video raises other questions:
>
> At :30 in the video "he steepens the bank, stalls and spins, even though the aircraft was well above the published stall speed".
>
> I understand that steeper bank increases load factor and that increases the speed at which critical AOA is reached. What I don't understand is why do power pilots use such low Va (such that an increase in bank commonly causes a stall/spin!).
>
> Is it because the stall speeds are so much higher in a power plane relative to the lengths of the runways? So a power pilot needs to fly slow, close to stall speed, to have an acceptable runout?
>
> I also notice in power flying forums that the notion of increasing Va proportional to wind/gust conditions gets little attention.
>
> I noticed power planes fly slow Va (a low multiple of their stall speed), shallow glide slopes and shallow bank turns. Gliders do the opposite. Why?
>
> I'm curious because I'm planning to take some lessons in a tailwheel power Kitfox, and I'd rather not pay to argue these points with my CFI.

Please research the V-G diagram, it describes the concept of Va, which is not what I think you're referring to. The Va speed is not selected by the "pilot" it is a construct of load factor, the angle of attack for a stall(both positive and negative), and the speed at which it occurs. It is often described as the speed at which a full control deflection (usually with regard to pitch) will result in a stall occurring before the load factor reaches a value that will damage the aircraft. Recent studies have shown that the other controls (for Yaw and Roll) may in fact cause damage below the Va speed.

Here's a pretty good Video:
https://www.youtube.com/watch?v=ZjBXAosfcco

[son_of_flubber]

On Saturday, April 9, 2016 at 2:04:16 AM UTC-4, SoaringXCellence wrote:
> On Friday, April 8, 2016 at 1:17:10 PM UTC-7, son_of_flubber wrote:
> > WRT OP's question. I'd guess that Butterfly has the sensor input to compute AOA. I don't know if they have the computation resources to complete the calculation in the real time constraints (but they will in the future generation of chips). I don't think that offering this functionality would increase their revenue. It would increase their costs, in particular their liability costs. Has anyone ever been sued for an inaccurate vario reading?
> >
> >
> > The video raises other questions:
> >
> > At :30 in the video "he steepens the bank, stalls and spins, even though the aircraft was well above the published stall speed".
> >
> > I understand that steeper bank increases load factor and that increases the speed at which critical AOA is reached. What I don't understand is why do power pilots use such low Va (such that an increase in bank commonly causes a stall/spin!).
> >
> > Is it because the stall speeds are so much higher in a power plane relative to the lengths of the runways? So a power pilot needs to fly slow, close to stall speed, to have an acceptable runout?
> >
> > I also notice in power flying forums that the notion of increasing Va proportional to wind/gust conditions gets little attention.
> >
> > I noticed power planes fly slow Va (a low multiple of their stall speed), shallow glide slopes and shallow bank turns. Gliders do the opposite. Why?
> >
> > I'm curious because I'm planning to take some lessons in a tailwheel power Kitfox, and I'd rather not pay to argue these points with my CFI.
>
> Please research the V-G diagram, it describes the concept of Va, which is not what I think you're referring to. The Va speed is not selected by the "pilot" it is a construct of load factor, the angle of attack for a stall(both positive and negative), and the speed at which it occurs. It is often described as the speed at which a full control deflection (usually with regard to pitch) will result in a stall occurring before the load factor reaches a value that will damage the aircraft. Recent studies have shown that the other controls (for Yaw and Roll) may in fact cause damage below the Va speed.
>
> Here's a pretty good Video:
> https://www.youtube.com/watch?v=ZjBXAosfcco

I meant Vat (V approach) not Va (maneuvering speed) which makes no sense in the context of my comment.

[Jonathan St. Cloud]

Several decades ago the SSA sponsored a contest to design an AOA, now we have the technology to have a viable solution. Just saying

[Dan Marotta]

Wasn't there something years back that was attached to the trailing edge
of the wing? It included two holes, one above the wing and one below.
These holes were connected via tubing to an instrument in the cockpit
which displayed the difference in dynamic pressures between the top and
bottom of the wing which, I would assume, could be marked to show where
a stall could be expected.

Or was that one of Dick Johnson's devices for measuring drag?

On 4/9/2016 8:16 AM, Jonathan St. Cloud wrote:
> Several decades ago the SSA sponsored a contest to design an AOA, now we have the technology to have a viable solution. Just saying

--
Dan, 5J

[firsys]

On Friday, April 8, 2016 at 2:39:56 PM UTC-4, Jonathan St. Cloud wrote:
> Was just reading about the Aspen suite of avionics for GA
> http://www.flyingmag.com/way-to-aoa?src=PPC&dom=fb&con=Aspen-FB-Ads.
> Was wondering if Air-Avionics Butterfly, LX 90XX or similar modern glide computers would be capable of such algorithms to have a working AOA?

At the epoch of the SSA AoA indicator, I did some work on another approach.
It consisted of a microphone, amp., and a variable Hi/low pass filter
to select airflow noise in a limited band. It was sucessfull in
showing approach to the stall in a Puchaz by a rise in the
low frequency flow detachment near the TE. I concluded that it was insufficiently robust to be generally usefull.

John f

[SoaringXCellence]

I've done some research into developing a pitch/yaw AOA device. It can replace the Pitot tube and provide the angle of yaw and pitch as well as airspeed. It's based on a 5-port pitot combined with today's very small, sensitive, pressure transducers, computed by a micro-processor like an Arduino or Raspberry-Pi, Including the display screen, I think it can be constructed for under $100.

Unfortunately it's a ways down on the task list, and I just spent all my pennies on a Trig22. Maybe next year.

MB

Websites to peruse:

Here's a patent for a three-port Pitot/AOA system
http://www.google.com/patents/US4378696

Dynon makes a Pitot that is a simpler two port system for positive AOA only (page 1-4):

https://www.dynonavionics.com/downloads/Install_Guides/Heated_Unheated_AOA_Pitot_Probe_Installation_Guide _-_Rev_C.pdf

[son_of_flubber]

In a skidding turn is the low wing AOA higher than high wing AOA?

[[email protected]]

Anyone use a side string/s for AOA? DG has an article about it on their website.

[NG[_2_]]

On Tuesday, April 12, 2016 at 11:43:26 AM UTC-4, son_of_flubber wrote:
> In a skidding turn is the low wing AOA higher than high wing AOA?

In any turn, whether coordinated or slipping or skidding, and with no change in angle of bank, all parts of the aircraft have the same vertical velocity relative to the air mass, and the outside wingTIP is moving faster than the inside wingTIP, so the outside wingTIP has a lower angle of attack. Near the fuselage, there is not much difference in angle of attack, except for some side-flow effects from slipping or skidding.

[[email protected]]

Dear kristi... and Jonathan,

I have indeed "installed" the mentioned Side String in form of a wool string of 25-30 cm length for the last 5 years on an ASG 29 and ASH 31. It works quite well - once "calibrated" on stall and best glide speed, it's fast and IMHO pretty accurate in straight level flight taking speed and g-load into account. It seems robust in different flap settings (actually it is a great optical reminder for keeping proper flap settings...). When banking/thermaling (especially with a slight side slip) it might loose some of its absolute accuracy due to turbulence and flow changes on the front fuselage but it still provides a good and fast tendency regarding getting closer to stalling the glider (completely in sync with the weakening feeling in the controls when approaching a stall). Drawback might be that attaching the string to the lower canopy creates a turbulence wake on a possibly laminar flow in the front part of the fuselage but given that the bug wipers kill that flow anyway 50 cm behind the string, I recon that this is almost irrelevant...

Best regards
Marc (S2)

[[email protected]]

I have had two sidestrings on my Pilatus B4.
I works fairly okay, but the location was a bit tricky in my case. In some cases it would not move at all (except during tail-slides :-)).

Here is a video of a spin with my setup:
https://www.youtube.com/watch?v=RWPya_vchDQ

You can see the vortex on the right-hand side which is generated by the high yaw rate of my glider.

[danlj]

I put yaw strings on each side of the canopy of my Ventus Cm a few years ago, and found them instructive. Didn't replace them when they fell off, but will do so in the future, to re-learn the lessons they taught.

[Soartech]

I have been casually working on building a low-cost AOA measurement system using a small side vane. This would be easy to install, battery powered so require no digging into your panel to find power. The parts cost does add up faster than I thought so it would still be a few hundred dollars after parts, building and overhead is factored in. My glider gives a very audible vibration approaching stall so I am wondering if it is even worth it. I am a relatively low-time sailplane pilot. Too many skilled pilots continue to spin in which makes me wonder if their ships don't give any hint of approaching stall or what else is going on.

[son_of_flubber]

On Wednesday, April 13, 2016 at 10:56:34 AM UTC-4, Soartech wrote:
> I have been casually working on building a low-cost AOA measurement system... My glider gives a very audible vibration approaching stall so I am wondering if it is even worth it. ...

I think that if I were impaired by fatigue and dehydration, I might ignore the plane's warning vibration, and I think I would be even more likely to ignore the stall horn. The stall horn is calibrated to go off before the stall, and if I had one, I would have (as an unintended side effect) trained myself to ignore it (on every landing). Plus I think that in a stall spin on turn to final, the buffeting, stall and spin would come quickly while I was decisively increasing the bank, and I would not react to a dropping wing properly in time.

So to mitigate my risk, I'd learn to recognize and foresee my fatigue impairment, have a good pee and hydration system, use high pattern speeds, and for short field landings, I'd reduce airspeed to minimum AFTER the turn to final (and practice this often). In short, develop protective habits.

[kirk.stant]

On Tuesday, April 12, 2016 at 10:43:26 AM UTC-5, son_of_flubber wrote:
> In a skidding turn is the low wing AOA higher than high wing AOA?

No, it I lower. This is basic aero, but can be easily understood with a simple visual aid - or a good scale model of a glider.

First, made a simple paper or cardboard wing, about the size of a standard foot-long ruler. Has to be stiff enough to support its own weight.

Hold it at eye level as if it was a glider flying directly at you. Tilt a bit to simulate a flying angle of attack. Now rotate in yaw, and notice that the apparent angle of attack of both wings is the same, despite the yaw.

Now Bend the wing a little in the middle, simulating a reasonable amount of dihedral. Rotate again, and note the difference in apparent angle of attack between the forward and aft wing. That's why you can roll (slowly) using only rudder.

Now, bank your wing as if in a turn, and repeat the yawing exercise. Remember, a skid will have the upper wing forward (too much rudder into the turn) while a slip will have the lower wing forward (not enough rudder).

It should be pretty obvious what is happening to the AOA of each wing and why.

See also the threads about using a bit of a slip to counter the overbanking effect of long wings (the "yaw string to the outside" discussion).

Now the 64 K question - which way and why will you spin out of a skidding turn?

Kirk
66

[kirk.stant]

On Wednesday, April 13, 2016 at 9:56:34 AM UTC-5, Soartech wrote:
Too many skilled pilots continue to spin in which makes me wonder if their ships don't give any hint of approaching stall or what else is going on.

I think a lot of pilots, both low-time and skilled, spend way too little time exploring the corners of the envelope of their gliders - both high and low speed, negative to positive Gs, shallow to steep banks.

Get high and practice trying to kill yourself in the pattern, to the point that you recognize instinctively a dangerous condition and apply the right corrective actions. This is a basic flying skill, NOT an intellectual exercise!

Kirk
66

[bumper[_4_]]

I purchased a vane type AOA, a CYA-100, when the inventor was first starting out, at considerably less than the $625 price at Aircraft Spruce:

http://www.aircraftspruce.com/catalog/inpages/aoacya100.php

It consists of a balanced carbon fiber vane on a short aerodynamic strut, turning a rotary hall effect sensor.

http://sensing.honeywell.com/products/hall-position-sensors

and a row of LED lights for a display. Set points are adjustable.

It works very nicely on my Husky, being especially useful for very short off field work where minimal energy is needed and short final is at or below 1.1 Vso. Also good when down in a steep Idaho canyon, loaded to the hilt with camping gear, flying close to the canyon wall, and needing to to a sharp turn to drop over some tall trees into a short back country strip. Sure, you can do it seat of the pants, maybe, but the AOA is very reassuring, letting you know what the margin is while cranking and banking down low when all one's senses are on edge. I like it.

Don't feel the need for one on my glider. Maybe 3 MKIV yaw strings. !!!Conflict of Interest Alert!!!

bumper
MKIV & QV

[Jim Lewis[_2_]]

On Wednesday, April 13, 2016 at 11:54:17 AM UTC-7, kirk.stant wrote:
> On Tuesday, April 12, 2016 at 10:43:26 AM UTC-5, son_of_flubber wrote:
> > In a skidding turn is the low wing AOA higher than high wing AOA?
>
> No, it I lower. This is basic aero, but can be easily understood with a simple visual aid - or a good scale model of a glider.
>
> First, made a simple paper or cardboard wing, about the size of a standard foot-long ruler. Has to be stiff enough to support its own weight.
>
> Hold it at eye level as if it was a glider flying directly at you. Tilt a bit to simulate a flying angle of attack. Now rotate in yaw, and notice that the apparent angle of attack of both wings is the same, despite the yaw.
>
> Now Bend the wing a little in the middle, simulating a reasonable amount of dihedral. Rotate again, and note the difference in apparent angle of attack between the forward and aft wing. That's why you can roll (slowly) using only rudder.
>
> Now, bank your wing as if in a turn, and repeat the yawing exercise. Remember, a skid will have the upper wing forward (too much rudder into the turn) while a slip will have the lower wing forward (not enough rudder).
>
> It should be pretty obvious what is happening to the AOA of each wing and why.
>
> See also the threads about using a bit of a slip to counter the overbanking effect of long wings (the "yaw string to the outside" discussion).
>
> Now the 64 K question - which way and why will you spin out of a skidding turn?
>
> Kirk
> 66

My understanding is the glider will spin in the direction of the applied rudder. If that is the case then the glider will spin to the inside of the skidding turn. But, if the AoA of the inside wing is lower than the AoA of the outside wing why would the inside wing stall first and drop so the glider spins in the direction of the inside wing? I have no idea.

[son_of_flubber]

On Wednesday, April 13, 2016 at 11:08:12 PM UTC-4, Jim Lewis wrote:
> But, if the AoA of the inside wing is lower than the AoA of the outside wing why would the inside wing stall first and drop so the glider spins in the direction of the inside wing? I have no idea.

And where do you mount your AOA sensor so that it works equally well for both left and right turns/skid/slip?

[Ben Coleman]

On Thursday, 14 April 2016 13:42:34 UTC+10, son_of_flubber wrote:
> On Wednesday, April 13, 2016 at 11:08:12 PM UTC-4, Jim Lewis wrote:
> > But, if the AoA of the inside wing is lower than the AoA of the outside wing why would the inside wing stall first and drop so the glider spins in the direction of the inside wing? I have no idea.
>
> And where do you mount your AOA sensor so that it works equally well for both left and right turns/skid/slip?

A tuft on the left, another on the right and joint the ends with a piece of wool for real time mechanical averager, bonus points for being in the natural line of sight.

You do have two clearview panels in your glider of course?

Cheers Ben

[Surge]

On Thursday, 14 April 2016 05:08:12 UTC+2, Jim Lewis wrote:
> My understanding is the glider will spin in the direction of the applied rudder. If that is the case then the glider will spin to the inside of the skidding turn. But, if the AoA of the inside wing is lower than the AoA of the outside wing why would the inside wing stall first and drop so the glider spins in the direction of the inside wing? I have no idea.


Kirk 66 has it wrong.
The angle of attack on the inside wing (low wing) in a banked turn is higher than the outside (high) wing. Both wings descend at the same rate but the outside wing travels further (and faster) than the inside wing.
The AoA of the inside wing is higher which is why it stalls first. Trying to pick up the inside wing with aileron only aggravates the situation because you're increasing the angle of attack of the wing tip (chord line changes) and the additional drag also holds the inside wing even further back which in turn adds pro skid yaw.

A skidding turn makes the situation even worse because now you're holding the slower inside wing back and the fuselage starts to disrupt some of the air flow to the inboard portion of the inside wing which now has to work even harder to provide the same amount of lift. In order to increase lift at a given speed you need to increase the angle of attack and this pushes the inside wing even closer to a stalled state. It all has a compounding effect when added together.

I think too much emphasis is placed on gadgetry and ideas to stop people spinning instead of training pilots to fly safer speeds.
If safe speed control is taught and adhered to then wings won't stall, and if there are no stalls there will be no spins either.
Personally I always fly at about 10 knots faster than minimum recommended approach speed (taking wind into account) in the circuit and only slow down on finals if I need to. I also thermal about 10 knots faster when I'm below 2000 feet AGL. Yes, it's less efficient but it's also safer. What I've found though is that my higher speed habits lower down become my habits higher up too. I tend to fly faster than required everywhere because flying slower feels unnatural unless it's during round out on landing.
I can live with flying less efficiently and my family won't need to hear that they just lost their husband and father due to a silly and avoidable accident.

[Bruce Hoult]

On Wednesday, April 13, 2016 at 9:54:17 PM UTC+3, kirk.stant wrote:
> On Tuesday, April 12, 2016 at 10:43:26 AM UTC-5, son_of_flubber wrote:
> > In a skidding turn is the low wing AOA higher than high wing AOA?
>
> No, it I lower. This is basic aero, but can be easily understood with a simple visual aid - or a good scale model of a glider.
>
> First, made a simple paper or cardboard wing, about the size of a standard foot-long ruler. Has to be stiff enough to support its own weight.
>
> Hold it at eye level as if it was a glider flying directly at you. Tilt a bit to simulate a flying angle of attack. Now rotate in yaw, and notice that the apparent angle of attack of both wings is the same, despite the yaw.
>
> Now Bend the wing a little in the middle, simulating a reasonable amount of dihedral. Rotate again, and note the difference in apparent angle of attack between the forward and aft wing. That's why you can roll (slowly) using only rudder.
>
> Now, bank your wing as if in a turn, and repeat the yawing exercise. Remember, a skid will have the upper wing forward (too much rudder into the turn) while a slip will have the lower wing forward (not enough rudder).
>
> It should be pretty obvious what is happening to the AOA of each wing and why.
>
> See also the threads about using a bit of a slip to counter the overbanking effect of long wings (the "yaw string to the outside" discussion).
>
> Now the 64 K question - which way and why will you spin out of a skidding turn?

Well, you're right that it's basic aero, but you've somehow managed to get it backwards.

Both wings are descending through the air at the same speed (or you'd be rolling). The inner wing is travelling less distance therefore the angle of attack is greater.

Looking at it another way, the inner wing is travelling slower but has to generate the same amount of lift, therefore its angle of attack must be greater.

Stable slips or skids and dihedral don't make any difference to this. Of course if you kick in some yaw then at the moment the speeds and distances traveled will be different. Putting in some slip/top rudder will accelerate the bottom wing and (briefly) take it to a lower AoA -- and possibly even out of stall if it was a little bit stalled.

[son_of_flubber]

On Thursday, April 14, 2016 at 7:05:36 AM UTC-4, Bruce Hoult wrote:

> Stable slips or skids and dihedral don't make any difference to this.

I was thinking that in a slip/skid, the direction of the relative wind across the airfoil changes (more diagonal flow), and the effective cross-section of the airfoil (shape) changes, and that this might raise or lower the AOA (or both raise and lower at different points along the wing). I was thinking that this may cause a discrepancy between what the AOA sensor is measuring and what the wing was actually experiencing. Maybe not a significant error, since AOA is a warning device.

Also of concern would be how slip/skid affects the AOA sensor itself.

I've seen more than one Youtube video where the stall horn is blaring for the entire final approach, and the pilot is either deliberately or erroneously ignoring it.

Is an AOA indicator (at below critical AOA) useful for optimizing powered flight, minimizing fuel consumption, maximizing rate of climb?

[Casey[_2_]]

I don't get it. Most critical time to have eyes out of cockpit...especially if landing out.

[Jonathan St. Cloud]

Well, you can use the AOA other than landing. Just so you know the navy teaches to fly by AOA for carrier landings. (Full disclosure, I am not a Navy pilot, never have been). However, I have landed on a boat and taken off from a boat, back in my helicopter days.

On Thursday, April 14, 2016 at 7:14:19 AM UTC-7, Casey wrote:
> I don't get it. Most critical time to have eyes out of cockpit...especially if landing out.

[kirk.stant]

On Thursday, April 14, 2016 at 9:14:19 AM UTC-5, Casey wrote:
> I don't get it. Most critical time to have eyes out of cockpit...especially if landing out.

Totally agree. The best way to convey AOA is with aural tones (from personal experience in F-4s that had such a system). Properly implemented, you can control your approach speed precisely without ever taking your eyes off the runway to look at the airspeed or AOA indicator, regardless of bank angle or gross weight.

Kirk
66

[kirk.stant]

On Thursday, April 14, 2016 at 6:05:36 AM UTC-5, Bruce Hoult wrote:
> On Wednesday, April 13, 2016 at 9:54:17 PM UTC+3, kirk.stant wrote:
> Well, you're right that it's basic aero, but you've somehow managed to get it backwards.
>
> Both wings are descending through the air at the same speed (or you'd be rolling). The inner wing is travelling less distance therefore the angle of attack is greater.

Unless you are spinning, I doubt the difference in distance has a greater effect than the effect of yaw on the effective AOA of each wing. Once you are in a spin, then the inside wing is definitely at a higher AOA and stalled (which is pretty much the definition of a spin).

> Looking at it another way, the inner wing is travelling slower but has to generate the same amount of lift, therefore its angle of attack must be greater.

Only if you want a constant bank. Which is why you either have to use top aileron against the overbanking tendency, which increases the camber of the bottom wing, or top rudder to increase the AOA via yaw. If you bank and do neither, the top wing will make more lift and you end up in a spiral.

> Stable slips or skids and dihedral don't make any difference to this. Of course if you kick in some yaw then at the moment the speeds and distances traveled will be different. Putting in some slip/top rudder will accelerate the bottom wing and (briefly) take it to a lower AoA -- and possibly even out of stall if it was a little bit stalled.

Any wing with dihedral (or sweepback) will roll if held in a steady yawed condition with positive AOA held. Not very effective in the typical glider, but in something like an F-4 or F-15, you can do nice 4-point rolls using only back stick and rudder.

But I'm only an amateur aerodynamicist, any experts out there to explain how I'm wrong? Always willing to learn... ;^)

[kirk.stant]

On Thursday, April 14, 2016 at 12:34:42 AM UTC-5, Surge wrote:
> On Thursday, 14 April 2016 05:08:12 UTC+2, Jim Lewis wrote:
> > My understanding is the glider will spin in the direction of the applied rudder. If that is the case then the glider will spin to the inside of the skidding turn. But, if the AoA of the inside wing is lower than the AoA of the outside wing why would the inside wing stall first and drop so the glider spins in the direction of the inside wing? I have no idea.
>
>
> Kirk 66 has it wrong.
> The angle of attack on the inside wing (low wing) in a banked turn is higher than the outside (high) wing. Both wings descend at the same rate but the outside wing travels further (and faster) than the inside wing.
> The AoA of the inside wing is higher which is why it stalls first. Trying to pick up the inside wing with aileron only aggravates the situation because you're increasing the angle of attack of the wing tip (chord line changes) and the additional drag also holds the inside wing even further back which in turn adds pro skid yaw.
>
> A skidding turn makes the situation even worse because now you're holding the slower inside wing back and the fuselage starts to disrupt some of the air flow to the inboard portion of the inside wing which now has to work even harder to provide the same amount of lift. In order to increase lift at a given speed you need to increase the angle of attack and this pushes the inside wing even closer to a stalled state. It all has a compounding effect when added together.
>
> I think too much emphasis is placed on gadgetry and ideas to stop people spinning instead of training pilots to fly safer speeds.
> If safe speed control is taught and adhered to then wings won't stall, and if there are no stalls there will be no spins either.
> Personally I always fly at about 10 knots faster than minimum recommended approach speed (taking wind into account) in the circuit and only slow down on finals if I need to. I also thermal about 10 knots faster when I'm below 2000 feet AGL. Yes, it's less efficient but it's also safer. What I've found though is that my higher speed habits lower down become my habits higher up too. I tend to fly faster than required everywhere because flying slower feels unnatural unless it's during round out on landing.
> I can live with flying less efficiently and my family won't need to hear that they just lost their husband and father due to a silly and avoidable accident.

I think we may be discussing different issues. If you skid a turn, the AOA of the lower wing will initially be lower (due to dihedral), so to keep from rolling, you will have to use a lot of top aileron to increase the lift of the lower wing. Aerodynamically, you have a flapped wing on the inside and a negative flap wing on the top. The camber of the flapped wing is greater, so the effective AOA is greater, and when you finally stall, the inside wing will drop, and with pro-spin rudder, you will probably depart into a spin INTO the turn. My LS6 will only depart (at my weight and CG) in landing flap from a grossly skidded turn, and then it will do a nice spin entry (for a quarter turn, then it transitions to a spiral dive). At any other flap setting, it just drops the nose a little.

Totally agree about maintaining extra speed when low and maneuvering - and strongly feel that pilots need to PRACTICE low speed departure and recoveries so that they know instinctively what is going on.

cheers,

Kirk
66

[son_of_flubber]

On Thursday, April 14, 2016 at 10:58:57 AM UTC-4, kirk.stant wrote:
>The best way to convey AOA is with aural tones (from personal experience in F-4s that had such a system). Properly implemented, you can control your approach speed precisely without ever taking your eyes off the runway to look at the airspeed or AOA indicator, regardless of bank angle or gross weight.

This sounds worthwhile, and I'd think it would be relatively easy to implement in software.

[Jim Lewis[_2_]]

On Thursday, April 14, 2016 at 8:36:34 AM UTC-7, kirk.stant wrote:
> On Thursday, April 14, 2016 at 12:34:42 AM UTC-5, Surge wrote:
> > On Thursday, 14 April 2016 05:08:12 UTC+2, Jim Lewis wrote:
> > > My understanding is the glider will spin in the direction of the applied rudder. If that is the case then the glider will spin to the inside of the skidding turn. But, if the AoA of the inside wing is lower than the AoA of the outside wing why would the inside wing stall first and drop so the glider spins in the direction of the inside wing? I have no idea.
> >
> >
> > Kirk 66 has it wrong.
> > The angle of attack on the inside wing (low wing) in a banked turn is higher than the outside (high) wing. Both wings descend at the same rate but the outside wing travels further (and faster) than the inside wing.
> > The AoA of the inside wing is higher which is why it stalls first. Trying to pick up the inside wing with aileron only aggravates the situation because you're increasing the angle of attack of the wing tip (chord line changes) and the additional drag also holds the inside wing even further back which in turn adds pro skid yaw.
> >
> > A skidding turn makes the situation even worse because now you're holding the slower inside wing back and the fuselage starts to disrupt some of the air flow to the inboard portion of the inside wing which now has to work even harder to provide the same amount of lift. In order to increase lift at a given speed you need to increase the angle of attack and this pushes the inside wing even closer to a stalled state. It all has a compounding effect when added together.
> >
> > I think too much emphasis is placed on gadgetry and ideas to stop people spinning instead of training pilots to fly safer speeds.
> > If safe speed control is taught and adhered to then wings won't stall, and if there are no stalls there will be no spins either.
> > Personally I always fly at about 10 knots faster than minimum recommended approach speed (taking wind into account) in the circuit and only slow down on finals if I need to. I also thermal about 10 knots faster when I'm below 2000 feet AGL. Yes, it's less efficient but it's also safer. What I've found though is that my higher speed habits lower down become my habits higher up too. I tend to fly faster than required everywhere because flying slower feels unnatural unless it's during round out on landing.
> > I can live with flying less efficiently and my family won't need to hear that they just lost their husband and father due to a silly and avoidable accident.
>
> I think we may be discussing different issues. If you skid a turn, the AOA of the lower wing will initially be lower (due to dihedral), so to keep from rolling, you will have to use a lot of top aileron to increase the lift of the lower wing. Aerodynamically, you have a flapped wing on the inside and a negative flap wing on the top. The camber of the flapped wing is greater, so the effective AOA is greater, and when you finally stall, the inside wing will drop, and with pro-spin rudder, you will probably depart into a spin INTO the turn. My LS6 will only depart (at my weight and CG) in landing flap from a grossly skidded turn, and then it will do a nice spin entry (for a quarter turn, then it transitions to a spiral dive). At any other flap setting, it just drops the nose a little.
>
> Totally agree about maintaining extra speed when low and maneuvering - and strongly feel that pilots need to PRACTICE low speed departure and recoveries so that they know instinctively what is going on.
>
> cheers,
>
> Kirk
> 66

Something just doesn't ring for me in this. I am easily confused though. I guess I'll just do my best to stay away from trouble!

[[email protected]]

Poor mans AOA? A string with a nut tied to the end tied to bottom if panel and hanging down with two kines marked on the floor. One for-aft, one side to side drawn at right angles to each other. Works great in a pinch, costs 23cents.

[[email protected]]

On Thursday, April 14, 2016 at 5:17:04 PM UTC-7, wrote:
> Poor mans AOA? A string with a nut tied to the end tied to bottom if panel and hanging down with two kines marked on the floor. One for-aft, one side to side drawn at right angles to each other. Works great in a pinch, costs 23cents.

Will not work under acceleration.

[[email protected]]

On Thursday, April 14, 2016 at 8:58:15 AM UTC-7, son_of_flubber wrote:
> On Thursday, April 14, 2016 at 10:58:57 AM UTC-4, kirk.stant wrote:
> >The best way to convey AOA is with aural tones (from personal experience in F-4s that had such a system). Properly implemented, you can control your approach speed precisely without ever taking your eyes off the runway to look at the airspeed or AOA indicator, regardless of bank angle or gross weight.
>
> This sounds worthwhile, and I'd think it would be relatively easy to implement in software.

I will write the firmware, if others do the hardware...

Marc

[[email protected]]

Audio aoa
https://www.youtube.com/watch?v=H81AcnZeaMQ

[son_of_flubber]

On Friday, April 15, 2016 at 12:54:52 AM UTC-4, wrote:
> Audio aoa
> https://www.youtube.com/watch?v=H81AcnZeaMQ

Not quite. This is just a beeping stall horn that goes off at a discrete threshold. I imagined an audible AOA that would produce different tones for different AOA, so that you could use it to gauge AOA that is less than critical AOA. How is that useful? You could use it to hold the plane a notch below critical AOA during maneuvers, like a dive recovery.

It would sound something like an audible variometer. You'd probably want to automatically turn the audible variometer off perhaps when current AOA got within range of critical AOA.

Surely this exists already. There are AOA indicators that provide a visual readout of current AOA over the entire range.

[Dan Marotta]

Who cares?

Feel the force, Luke.

On 4/15/2016 7:06 AM, son_of_flubber wrote:
> On Friday, April 15, 2016 at 12:54:52 AM UTC-4, wrote:
>> Audio aoa
>> https://www.youtube.com/watch?v=H81AcnZeaMQ
> Not quite. This is just a beeping stall horn that goes off at a discrete threshold. I imagined an audible AOA that would produce different tones for different AOA, so that you could use it to gauge AOA that is less than critical AOA. How is that useful? You could use it to hold the plane a notch below critical AOA during maneuvers, like a dive recovery.
>
> It would sound something like an audible variometer. You'd probably want to automatically turn the audible variometer off perhaps when current AOA got within range of critical AOA.
>
> Surely this exists already. There are AOA indicators that provide a visual readout of current AOA over the entire range.

--
Dan, 5J

[[email protected]]

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

[Paul Agnew]

"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.

[kirk.stant]

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

[Bruce Hoult]

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!

[kirk.stant]

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 Marotta]

"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

[[email protected]]

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.

[Soartech]

> 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.

[Jonathan St. Cloud]

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.

[[email protected]]

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...

[[email protected]]

On Sunday, April 17, 2016 at 9:56:30 PM UTC-7, Jonathan St. Cloud wrote:
> Or perhaps you could do it with software as per the original post.

Some flight computers and PDA programs already have "stall warnings" calculated using airspeed and G loading. My sole experience actually using this feature was on a CAI 302, I don't remember it being particularly useful or if it was all that accurate.

[Dan Daly[_2_]]

On Monday, April 18, 2016 at 1:47:46 AM UTC-4, wrote:
> On Sunday, April 17, 2016 at 9:56:30 PM UTC-7, Jonathan St. Cloud wrote:
> > Or perhaps you could do it with software as per the original post.
>
> Some flight computers and PDA programs already have "stall warnings" calculated using airspeed and G loading. My sole experience actually using this feature was on a CAI 302, I don't remember it being particularly useful or if it was all that accurate.

Why re-invent something currently available? In my SZD-55, it works.
http://www.olk.com.pl/indexen.php?bo=prod&prx=products&lpx=26

[Bruce Hoult]

On Monday, April 18, 2016 at 5:32:22 PM UTC+12, wrote:
> 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...

PCBs are easy. I can put you onto a friend who designs PCBs at home in Dunedin, gets them made in China cheap. He even has a small pick-and-place machine at home for production runs up to a few hundred or low thousands of units.

The hard part is the software to filter and calibrate and interpret the signals. It'd take a few hours of flying, recording the signals, and comparing to a known accurate AOA measurement method (e.g. a decent sized vane on a stick out in the freestream)

I did a similar thing with using an Arduino and exposed thermistor to get a precise (0.01 C relative) and stable temperature measurement for my home heating control. On stormy winter nights with a few draughts around it was amazing how noisy the thermistor output was! No, you don't need to control the temperature to 0.01 C ... 0.1 or 0.2 is fine ... but more accurate measurement lets you pick up any trend early. And in fact I found I was able to usually keep the temperature (as measured by the controller anyway) usually within 0.02 just by switching an oil filled electric heater on or off at 30 second intervals. Worst case errors from starting or stopping cooking, boiling the kettle etc were 0.2 to 0.3, corrected in about 20 minutes -- those heaters have a LONG thermal constant.

[Jonathan St. Cloud]

Or you could use the readily available software already developed as per the information in original post, just like Aspen did.

[[email protected]]

On Monday, April 18, 2016 at 2:48:16 AM UTC-7, Bruce Hoult wrote:
> PCBs are easy. I can put you onto a friend who designs PCBs at home in Dunedin, gets them made in China cheap. He even has a small pick-and-place machine at home for production runs up to a few hundred or low thousands of units.

I do embedded software and know enough about digital logic design to get into trouble, but design of a proper PCB (or analog circuitry) is beyond me. It is getting quite easy to cobble together sophisticated devices on a breadboard.

> The hard part is the software to filter and calibrate and interpret the signals. It'd take a few hours of flying, recording the signals, and comparing to a known accurate AOA measurement method (e.g. a decent sized vane on a stick out in the freestream)

I'm not so sure one needs an accurate absolute numeric AoA, so much as a repeatable measure of how close you are to stall AoA. Such a system would need to be calibrated for each glider installation by going up and stalling in various configurations. I have some practical experience on the filtering side, including working with another poster is this group to build a flight computer with digitally differentiated variometer about a decade ago (when there was more of a need for analog circuitry). We did hours of flying (and driving fast up/down steep hills), before we managed to get the filtering right.

[Craig Funston]

On Monday, April 18, 2016 at 1:16:33 PM UTC-7, wrote:
> On Monday, April 18, 2016 at 2:48:16 AM UTC-7, Bruce Hoult wrote:
> > PCBs are easy. I can put you onto a friend who designs PCBs at home in Dunedin, gets them made in China cheap. He even has a small pick-and-place machine at home for production runs up to a few hundred or low thousands of units.
>
> I do embedded software and know enough about digital logic design to get into trouble, but design of a proper PCB (or analog circuitry) is beyond me.. It is getting quite easy to cobble together sophisticated devices on a breadboard.
>
> > The hard part is the software to filter and calibrate and interpret the signals. It'd take a few hours of flying, recording the signals, and comparing to a known accurate AOA measurement method (e.g. a decent sized vane on a stick out in the freestream)
>
> I'm not so sure one needs an accurate absolute numeric AoA, so much as a repeatable measure of how close you are to stall AoA. Such a system would need to be calibrated for each glider installation by going up and stalling in various configurations. I have some practical experience on the filtering side, including working with another poster is this group to build a flight computer with digitally differentiated variometer about a decade ago (when there was more of a need for analog circuitry). We did hours of flying (and driving fast up/down steep hills), before we managed to get the filtering right.

It is amazing the amount of processing power that's available. Here's a board with a magnetometer, 3-axis accelerometer and precision pressure sensor for under $16. The pressure sensor is calibrated for a limited range of atmospheric presssures (ground level to 500 mbar), but this is still pretty cool.

https://www.element14.com/community/docs/DOC-65084/l/xtrinsic-sensor-board

[[email protected]]

On Monday, April 18, 2016 at 1:27:39 PM UTC-7, Craig Funston wrote:
> It is amazing the amount of processing power that's available. Here's a board with a magnetometer, 3-axis accelerometer and precision pressure sensor for under $16. The pressure sensor is calibrated for a limited range of atmospheric presssures (ground level to 500 mbar), but this is still pretty cool.
>
> https://www.element14.com/community/docs/DOC-65084/l/xtrinsic-sensor-board

I use these for drone projects:

http://www.drotek.com/shop/en/home/290-imu-10dof-mpu9150-ms5611-.html

$21 if you don't have to pay VAT. MS5611 makes a very nice variometer throughout our altitude range with proper software...

[Charlie M. (UH & 002 owner/pilot)]

While this is a great idea, what happens to a pilot that flies a different glider?
I, myself, can bounce around multiple gliders in a day/weekend.

As an ex CFIG, I feel not enough training upfront to help out.

I will admit the annual numbers disagree with me.

Maybe it's a case of, "You can't fix stupid".......

Make all the rules you want, Darwin will eventually win.......

[[email protected]]

On Monday, April 18, 2016 at 2:12:07 PM UTC-7, Charlie M. (UH & 002 owner/pilot) wrote:
> While this is a great idea, what happens to a pilot that flies a different glider?
> I, myself, can bounce around multiple gliders in a day/weekend.
>
> As an ex CFIG, I feel not enough training upfront to help out.
>
> I will admit the annual numbers disagree with me.
>
> Maybe it's a case of, "You can't fix stupid".......
>
> Make all the rules you want, Darwin will eventually win.......

My answer would be: the vast majority of the time for the vast majority of pilots, letting the AoA wander into the danger zone is not going to be a problem. However, after 6+ hours in the cockpit, tired, hungry, perhaps dehydrated and/or hypoxic, in gusty turbulent conditions, I've known myself to make silly mistakes. Given that I only end up doing these sorts of flights in my own glider, a little reminder about attitude might just help the one time I really need it. Over and above that, a workable AoA system would be quite helpful during winch launches.

[Soartech]

On Monday, April 18, 2016 at 7:44:39 AM UTC-4, Jonathan St. Cloud wrote:
> Or you could use the readily available software already developed as per the information in original post, just like Aspen did.

I just watched the video referenced in the original (first) post in this thread.
It says the software came from the Italian Aerospace Center for Research so I went to
http://www.cira.it/en/comunicazione-en/news/aspen-avionics-annuncia-il-primo-prodotto-risultato-della-collaborazione-col-cira
and found this sentance: "The system is based on a patent-pending technology shared between CIRA and ASPEN, with four CIRA's researchers among the key inventors." So this is not "readily available software". It is patented and not available without paying for it.

[Jonathan St. Cloud]

It really is amazing. While not an instrument designer nor software engineer I think Air-avionics Butterfly and perhaps LX 90xx have all the necessary hardware to get the information on AOA, just needs software, which has been developed by other parties for this purpose.

On Monday, April 18, 2016 at 1:27:39 PM UTC-7, Craig Funston wrote:

> It is amazing the amount of processing power that's available. Here's a board with a magnetometer, 3-axis accelerometer and precision pressure sensor for under $16. The pressure sensor is calibrated for a limited range of atmospheric presssures (ground level to 500 mbar), but this is still pretty cool.
>
> https://www.element14.com/community/docs/DOC-65084/l/xtrinsic-sensor-board

[Tango Eight]

On Monday, April 18, 2016 at 5:12:07 PM UTC-4, Charlie M. (UH & 002 owner/pilot) wrote:
> While this is a great idea, what happens to a pilot that flies a different glider?


I guess you have to make do with only six indications (impending) stall.

How will you ever cope?

T8

[waremark]

Having reversing aids on my car encourages me to keep going back until they tell me I cannot go any further. I fear that having an AoA indication is as likely to encourage pushing the limits as keeping pilots away from them. Train pilots to monitor the ASI and always to keep the speed up when low and they are less likely to stall and spin in.

[Dan Marotta]

Don't forget about accelerated stalls! Airspeed alone is not enough
indication. Likewise, I never trust the backup camera, sensors, and
audio warnings in my car. I actually (gasp) look outside!

On 4/19/2016 5:52 AM, waremark wrote:
> Having reversing aids on my car encourages me to keep going back until they tell me I cannot go any further. I fear that having an AoA indication is as likely to encourage pushing the limits as keeping pilots away from them. Train pilots to monitor the ASI and always to keep the speed up when low and they are less likely to stall and spin in.

--
Dan, 5J

[[email protected]]

Yep Dan the same goes for Flarm and other cockpit "aids", they are just that, aids. Ya better learn basic stick n rudder skills before relying on the gizmos.
Dan

[Jonathan St. Cloud]

I learned to fly in an Aeronica Champ that had to be hand propped to start. Stick and rudder is essential, but having the "aids" leaves more brain power to aviate, less brain power and eyes down navigating... One must know how to fly without the "aids" and to fly well, but the "aids" can make the flight safer. Hence if AOA is within the technology offered (at reasonable price and utility) I would have it. Virtually all of my flying is in the mountains with many hours low in a mountain valley climbing up the mountain to get on top.

On Tuesday, April 19, 2016 at 9:11:56 AM UTC-7, wrote:
> Yep Dan the same goes for Flarm and other cockpit "aids", they are just that, aids. Ya better learn basic stick n rudder skills before relying on the gizmos.
> Dan

[kirk.stant]

On Tuesday, April 19, 2016 at 6:52:42 AM UTC-5, waremark wrote:
> Having reversing aids on my car encourages me to keep going back until they tell me I cannot go any further. I fear that having an AoA indication is as likely to encourage pushing the limits as keeping pilots away from them.. Train pilots to monitor the ASI and always to keep the speed up when low and they are less likely to stall and spin in.

I have to totally disagree with you. What you suggest is what is currently taught - and doesn't work particularly well - and never has.

Instead, teach a pilot what AOA means, and give him a simple way to monitor it, and perhaps you will see an improvement in stall/spin incidents.

Pilots are not stupid (well, most, perhaps...); do you really believe it's better to use an "approximate" instrument (airspeed in turning, accelerated flight) by simpley "adding enough to be safe", instead of using an instrument that would tell you EXACTLY what your margin is, and using that information to keep out of trouble?

Again, pilots who either do not really understand angle of attack vs airspeed, or have never actually used a good AOA system, seem amazingly reluctant (the term pig-headed comes to mind) to consider any improvements in how we fly - instead lets just stick to what we have always done - it's good enough!

Probably has a lot to do with glider pilot and type A personalities.

Now, how about unplugging our GPSs and going back to charts and whiskey compasses... in our fabric covered, biplane open cockpit gliders, bungee launched off the local hill.

Progress - it's not just a Soviet spacecraft!

Kirk
66

[BobW]

On 4/19/2016 8:38 PM, kirk.stant wrote:
> On Tuesday, April 19, 2016 at 6:52:42 AM UTC-5, waremark wrote:
>> Having reversing aids on my car encourages me to keep going back until
>> they tell me I cannot go any further. I fear that having an AoA
>> indication is as likely to encourage pushing the limits as keeping pilots
>> away from them. Train pilots to monitor the ASI and always to keep the
>> speed up when low and they are less likely to stall and spin in.
>
> I have to totally disagree with you. What you suggest is what is currently
> taught - and doesn't work particularly well - and never has.

I'm with Kirk. We've roughly a century's worth of (gloomy) data to ponder on
this front!
- - - - - -

> Instead, teach a pilot what AOA means, and give him a simple way to monitor
> it, and perhaps you will see an improvement in stall/spin incidents.

What a concept!

The U.S. Navy sure seems to like it the idea of using AOA as a primary
pattern/final-approach aid, and few will argue that landing fast,
high-wing-loading aircraft on moving targets, whether at night or not, is one
of the easier piloting tasks around. I'll wager Real Money that off-field
glider landings - not to mention home-airport glider landings - are trivially
easy by comparison.
- - - - - -

> Pilots are not stupid (well, most, perhaps...); do you really believe it's
> better to use an "approximate" instrument (airspeed in turning, accelerated
> flight) by simply "adding enough to be safe", instead of using an
> instrument that would tell you EXACTLY what your margin is, and using that
> information to keep out of trouble?
>
> Again, pilots who either do not really understand angle of attack vs
> airspeed, or have never actually used a good AOA system, seem amazingly
> reluctant (the term pig-headed comes to mind) to consider any improvements
> in how we fly - instead lets just stick to what we have always done - it's
> good enough!

Certainly a person doesn't have to look far to find examples of "better being
an enemy of good enough"...e.g. personally, my interest in (say) glider
navigation assisted by GPS is about zero. That's not a knock against any/all
of the pros associated with GPS navigation, but rather reflects a personal
philosophy that works for me ==>in this sport/country!<== Similarly, "stuff"
like flavors of trackers, gee-whiz-bang varios and soaring flight computers
hold little interest for me...which is not to suggest that I think all the
effort and brainpower expended on them/technology is a waste of time, for I
Most Surely do NOT so think.

To the point of this thread's topic, I think it would be the cat's meow to
have a gliding equivalent of a simple, repeatable, easily
calibratable,'HUD-based' AOA indicator in any glider I may fly, & part of me
sometimes wonders why I never bothered to mess around with taping yarn to
either side of my ship's canopy...was it simple laziness or passive acceptance
of "ASI-&-'feel'" being good enough? Point being, I guess, that inertia can be
a powerful thing...but I make a distinction between inertia and how a person
*thinks* about the possibility/worth of change.

I'm of the opinion that it's misguided thinking to argue "ASI as AOA proxy" is
better than "direct AOA".

> Probably has a lot to do with glider pilot and type A personalities.

Heh - I doubt anyone has ever accused me of being a Type A!
- - - - - -

> Now, how about unplugging our GPSs and going back to charts and whiskey
> compasses... in our fabric covered, biplane open cockpit gliders, bungee
> launched off the local hill.
>
> Progress - it's not just a Soviet spacecraft!
>
> Kirk 66
>

Technology - use it wisely.
- - - - - -

Bob - sometimes inaccurately branded a Luddite - W.

[Martin Gregorie[_5_]]

On Tue, 19 Apr 2016 21:23:32 -0600, BobW wrote:

> On 4/19/2016 8:38 PM, kirk.stant wrote:
>> Instead, teach a pilot what AOA means, and give him a simple way to
>> monitor it, and perhaps you will see an improvement in stall/spin
>> incidents.
>
> What a concept!
>
> The U.S. Navy sure seems to like it the idea of using AOA as a primary
> pattern/final-approach aid, and few will argue that landing fast,
> high-wing-loading aircraft on moving targets, whether at night or not,
> is one of the easier piloting tasks around. I'll wager Real Money that
> off-field glider landings - not to mention home-airport glider landings
> - are trivially easy by comparison.
> - - - - - -
>
Not an instrument as such, but...

Even after all this time and despite it being written for power pilots,
there's a lot of sense in Wolfgang Langewiesche's "Stick and Rudder" with
its advice to "fly the wing".

I think a copy belongs in a glider pilot's library alongside the books by
Piggott, Moffat, Reichman and Wolters.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[[email protected]]

Yep Martin, wolfgang's book studied and digested is a must have exsersize for anyone who trully wants to master flight.
Dan

[krasw]

No one has thought that AoA indicator could be useful tool to optimize your thermalling performance, in addition to stallwarning? Fly the correct AoA and disregard airspeed. I think DG-600 had some sort of AoA instrument because the wing profile required correct AoA to work at slow speed, not sure how that was implemented.

I do think that proper AoA measurement needs a separate sensor (vane or similar).

[[email protected]]

On Wednesday, April 20, 2016 at 8:04:48 AM UTC-5, wrote:
> Yep Martin, wolfgang's book studied and digested is a must have exsersize for anyone who trully wants to master flight.
> Dan

I read my Langewiesche every couple of years. He had it all figured out some 60 years ago, you have to admire that. Should still be mandatory for all pilots today - although the old-style airplanes in his hand-drawn pictures look really funny today.
Herb

[Bruce Hoult]

On Wednesday, April 20, 2016 at 5:05:48 PM UTC+3, wrote:
> On Wednesday, April 20, 2016 at 8:04:48 AM UTC-5, wrote:
> > Yep Martin, wolfgang's book studied and digested is a must have exsersize for anyone who trully wants to master flight.
> > Dan
>
> I read my Langewiesche every couple of years. He had it all figured out some 60 years ago, you have to admire that. Should still be mandatory for all pilots today - although the old-style airplanes in his hand-drawn pictures look really funny today.
> Herb

Published 72 years ago now.

I actually thought it was older than that...

[BobW]

On 4/20/2016 5:16 AM, Martin Gregorie wrote:
> Not an instrument as such, but...
>
> Even after all this time and despite it being written for power pilots,
> there's a lot of sense in Wolfgang Langewiesche's "Stick and Rudder" with
> its advice to "fly the wing".

"Roger all previous comments on 'Stick and Rudder'..."

As to "fly the wing," somewhere or other I read an interview of Bob Hoover in
which he noted that his 'messing around' (my words) in a(n ~37hp) E2 Cub prior
to becoming a military cadet taught him how to fly a wing.

His autobiography "Forever Flying" also notes his self-taught aerobatics began
(in pre "Stick and Rudder" days) with a somewhat technical book by "Bernie"
Lay, which Hoover more or less memorized before ever having an opportunity to
get in an airplane. Lest anyone think I'm advocating aerobatics self-taught as
THE way to learn how to 'fly the wing,'
the first few chapters of "Forever Flying" will make it abundantly clear how
Darwinian such an approach is!

Bob W.

[[email protected]]

Always thought the darwinian approach wasnt so bad, sure weeds out the chaff from the grain real quickly.

[Jonathan St. Cloud]

Funny, I have always thought the gene pool needed more chlorine, but as we all know the darwinian approach is not good for the sport. My point in starting this thread was to perhaps let the manufactures of these new computers to keep AOA in mind and try to develop software approach to AOA.

On Wednesday, April 20, 2016 at 11:18:20 AM UTC-7, wrote:
> Always thought the darwinian approach wasnt so bad, sure weeds out the chaff from the grain real quickly.

[[email protected]]

True Johnathan, there has been talk over the years about adapting AOA for the crop dusting world, as we are working with very high wing loadings and at times very high density altitude situations carrying astronomically heavy loads, but it never caught on. For our world since we fly so many hours ( last year I flew over 400 hours in 6 months in the same ship) guys just develop a feel for what their ship is doing.
Dan

[Jonathan St. Cloud]

Dan, I certainly agree, time in the saddle beats any gadget. However, the reason years ago the SSA sponsored a contest to develop AOA is for safety. Many pilots just do not fly enough, or cannot make enough time to fly enough. They are on the fine edge of currency and compentancy. Maybe early season.

I am sure I will be fine without an AOA, but for the sport, I think it would be a good idea with the internal nav units we have as varios. I was under the impression that the Butterfly vario and LX90xx with horizon had all the necessary hardware, just needed software for AOA. Might save a life or two.

One thing I have learned through years of flying, sailplanes, helicopters and airplanes are that anyone can be distracted for a moment and anyone can make a mistake.



On Wednesday, April 20, 2016 at 12:33:51 PM UTC-7, wrote:
> True Johnathan, there has been talk over the years about adapting AOA for the crop dusting world, as we are working with very high wing loadings and at times very high density altitude situations carrying astronomically heavy loads, but it never caught on. For our world since we fly so many hours ( last year I flew over 400 hours in 6 months in the same ship) guys just develop a feel for what their ship is doing.
> Dan

[[email protected]]

True

[[email protected]]

Thats when darwin takes over. Actually the wright bros were the first to develop and use an AOA way before we had airspeeds. But I dont think they will ever come into vogue. What I worry about is more cockpit distraction. By the time a guy hears, recognises and responds to an AOA horn honking, he is already into the sheeit too deep.

When I am instructing, before a student goes solo, we pick a good soaring day and work for over an hour on stall after stall, flying the edges of stall, accelerated and soecially turning at various bank angles. I jnow instructors who only take their students thru full stalls and never give them a good dose of tasting all the edges. I also do eyes closed sensing, and airspeed covered up sensing, etc. i want all the signs of inpending doom well ingrained in my students psyche.
Dan
Dan

[Bruce Hoult]

On Thursday, April 21, 2016 at 7:57:57 AM UTC+12, Jonathan St. Cloud wrote:
> Dan, I certainly agree, time in the saddle beats any gadget. However, the reason years ago the SSA sponsored a contest to develop AOA is for safety.. Many pilots just do not fly enough, or cannot make enough time to fly enough. They are on the fine edge of currency and compentancy. Maybe early season.
>
> I am sure I will be fine without an AOA, but for the sport, I think it would be a good idea with the internal nav units we have as varios. I was under the impression that the Butterfly vario and LX90xx with horizon had all the necessary hardware, just needed software for AOA. Might save a life or two.
>
> One thing I have learned through years of flying, sailplanes, helicopters and airplanes are that anyone can be distracted for a moment and anyone can make a mistake.
>
>
>
> On Wednesday, April 20, 2016 at 12:33:51 PM UTC-7, wrote:
> > True Johnathan, there has been talk over the years about adapting AOA for the crop dusting world, as we are working with very high wing loadings and at times very high density altitude situations carrying astronomically heavy loads, but it never caught on. For our world since we fly so many hours ( last year I flew over 400 hours in 6 months in the same ship) guys just develop a feel for what their ship is doing.
> > Dan

How exactly do you think a computer is going to calculate AoA without an AoA measurement? Using what inputs? IAS? TAS? AUW? G loading? What else?

I don't think you can do it, at least not well enough to me more useful than pilot feel. But I'm willing to be surprised.

[Jonathan St. Cloud]

Read the first post of this thread to see example.

On Wednesday, April 20, 2016 at 1:19:30 PM UTC-7, Bruce Hoult wrote:

> How exactly do you think a computer is going to calculate AoA without an AoA measurement? Using what inputs? IAS? TAS? AUW? G loading? What else?
>
> I don't think you can do it, at least not well enough to me more useful than pilot feel. But I'm willing to be surprised.

[Steve Koerner]

I would wish for an AOA sensor as well. What I would not want is a computed AOA even though I agree that the information is already present to compute it. AOA needs to be a direct sensor (sorry, Jonathan). If you are landing to the AOA indication and it is not right you may be in serious trouble. A computed AOA could be wrong for several different reasons. For example: pilot fails to enter ballast correctly, error in any one of multiple dependent sensors, extraordinary bug loading, precipitation or other contamination on wing, erroneous calibration factors for aircraft (setup errors happen all the time). The point is that this is situation that calls for direct measurement so that it has independent, stand-alone usefulness and relaibility.

An inferred AOA might be interesting as a teaching tool but I don't think it's a flying tool.

[[email protected]]

On Wednesday, April 20, 2016 at 1:30:46 PM UTC-7, Jonathan St. Cloud wrote:
> Read the first post of this thread to see example.
>
> On Wednesday, April 20, 2016 at 1:19:30 PM UTC-7, Bruce Hoult wrote:
>
> > How exactly do you think a computer is going to calculate AoA without an AoA measurement? Using what inputs? IAS? TAS? AUW? G loading? What else?
> >
> > I don't think you can do it, at least not well enough to me more useful than pilot feel. But I'm willing to be surprised.

Given airspeed, measured stall speed at specific weight, actual weight, and load factor (from an accelerometer), a flight computer can get a pretty approximation of the expected stall speed in normal straight or tuning flight.. Get the weight wrong, however (say using dry instead of wet weight), then the calculated stall speed will be wrong. During a winch launch, the wing is also being loaded by the rope, so the calculated stall speed will also be incorrect. By contrast, a properly installed AoA probe or vane will determine when you are approaching stall angle, independent of weight or any added loading during a winch launch...

[Steve Koerner]

I would also add that I think a direct measuring AOA sensor could help with thermalling performance -- most particularly if the slow, gooey computer operating the pitch plane might be replaced with a better one. There's an opportunity for a big soaring advance here, IMO.

[Bruce Hoult]

On Thursday, April 21, 2016 at 1:02:51 AM UTC+3, wrote:
> On Wednesday, April 20, 2016 at 1:30:46 PM UTC-7, Jonathan St. Cloud wrote:
> > Read the first post of this thread to see example.
> >
> > On Wednesday, April 20, 2016 at 1:19:30 PM UTC-7, Bruce Hoult wrote:
> >
> > > How exactly do you think a computer is going to calculate AoA without an AoA measurement? Using what inputs? IAS? TAS? AUW? G loading? What else?
> > >
> > > I don't think you can do it, at least not well enough to me more useful than pilot feel. But I'm willing to be surprised.
>
> Given airspeed, measured stall speed at specific weight, actual weight, and load factor (from an accelerometer), a flight computer can get a pretty approximation of the expected stall speed in normal straight or tuning flight. Get the weight wrong, however (say using dry instead of wet weight), then the calculated stall speed will be wrong. During a winch launch, the wing is also being loaded by the rope, so the calculated stall speed will also be incorrect. By contrast, a properly installed AoA probe or vane will determine when you are approaching stall angle, independent of weight or any added loading during a winch launch...

It's worse than that.

Say you're well above S&L stall speed -- 50 knots say, in a 45º turn, and stalled. Or pulling out of a dive and stalled. The load factor will be less than the maximum CL load factor at that speed. But it might well be above 1.0.

e.g. if your S&L stall is 40 knots, then at 50 knots you can pull 1.56 G.

If you're at 50 knots and pulling 1.3 G, are you well above the stall .. or ARE YOU ALREADY STALLED?

Other than a direct measurement of AoA from a vane or differential pressure, I don't even know what kind of input you can give to your calculation to tell you that. Attitude (from gyro or multiple GPS receivers) won't help.

[Craig Funston]

On Wednesday, April 20, 2016 at 3:20:09 PM UTC-7, Steve Koerner wrote:
> I would also add that I think a direct measuring AOA sensor could help with thermalling performance -- most particularly if the slow, gooey computer operating the pitch plane might be replaced with a better one. There's an opportunity for a big soaring advance here, IMO.

Since we're dreaming big here and taking advantage of wireless electronics it would be great to have an AOA probe near each wingtip.

Craig

[Bruce Hoult]

On Wednesday, April 20, 2016 at 11:30:46 PM UTC+3, Jonathan St. Cloud wrote:
> Read the first post of this thread to see example.
>
> On Wednesday, April 20, 2016 at 1:19:30 PM UTC-7, Bruce Hoult wrote:
>
> > How exactly do you think a computer is going to calculate AoA without an AoA measurement? Using what inputs? IAS? TAS? AUW? G loading? What else?
> >
> > I don't think you can do it, at least not well enough to me more useful than pilot feel. But I'm willing to be surprised.

Yes, I've watched the video.

I simply don't believe it. It's marketing bull****. It might work in a GA plane, flown sedately. It's not going to work in a glider.

It doesn't even know the correct freaking current flap position! What;s it going to do in a glider with 5 or 6 flap settings in common use, and intermediate positions possible.

[Dan Marotta]

You really don't need an AoA gauge. An indexer will do just fine.
Here's a link to one example
<https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=&url=http%3A%2F%2Fairfactsjournal.com%2F2015%2F07%2 Fsmoke-flames-report-ga-safety-picture-changing%2F&psig=AFQjCNGjTLiBuCDXvQMOmNlJQJJod6173g&ust=1461287874599677>.
Something could me made with a simple vertical stack of different
colored LEDs. You could mount one in the center of the glare shield,
one on each corner of the glare shield, or one on each canopy rail at
about the same position as the edge of the glare shield.

You don't have to look at them, you will see them peripherally.

On 4/20/2016 2:13 PM, wrote:
> Thats when darwin takes over. Actually the wright bros were the first to develop and use an AOA way before we had airspeeds. But I dont think they will ever come into vogue. What I worry about is more cockpit distraction. By the time a guy hears, recognises and responds to an AOA horn honking, he is already into the sheeit too deep.
>
> When I am instructing, before a student goes solo, we pick a good soaring day and work for over an hour on stall after stall, flying the edges of stall, accelerated and soecially turning at various bank angles. I jnow instructors who only take their students thru full stalls and never give them a good dose of tasting all the edges. I also do eyes closed sensing, and airspeed covered up sensing, etc. i want all the signs of inpending doom well ingrained in my students psyche.
> Dan
> Dan

--
Dan, 5J

[Dan Marotta]

Search the document that comes up when you follow the link, for the
string, AoA. You'll see the picture there.

On 4/20/2016 7:21 PM, Dan Marotta wrote:
> You really don't need an AoA gauge. An indexer will do just fine.
> Here's a link to one example
> <https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=&url=http%3A%2F%2Fairfactsjournal.com%2F2015%2F07%2 Fsmoke-flames-report-ga-safety-picture-changing%2F&psig=AFQjCNGjTLiBuCDXvQMOmNlJQJJod6173g&ust=1461287874599677>.
> Something could me made with a simple vertical stack of different
> colored LEDs. You could mount one in the center of the glare shield,
> one on each corner of the glare shield, or one on each canopy rail at
> about the same position as the edge of the glare shield.
>
> You don't have to look at them, you will see them peripherally.
>
> On 4/20/2016 2:13 PM, wrote:
>> Thats when darwin takes over. Actually the wright bros were the first to develop and use an AOA way before we had airspeeds. But I dont think they will ever come into vogue. What I worry about is more cockpit distraction. By the time a guy hears, recognises and responds to an AOA horn honking, he is already into the sheeit too deep.
>>
>> When I am instructing, before a student goes solo, we pick a good soaring day and work for over an hour on stall after stall, flying the edges of stall, accelerated and soecially turning at various bank angles. I jnow instructors who only take their students thru full stalls and never give them a good dose of tasting all the edges. I also do eyes closed sensing, and airspeed covered up sensing, etc. i want all the signs of inpending doom well ingrained in my students psyche.
>> Dan
>> Dan
>
> --
> Dan, 5J

--
Dan, 5J

[Jonathan St. Cloud]

Not that I am arguing with anyone, but my flight computer, knows my flap position, it also knows when I dump water and for how long (LX 90xx). I have in the profile the empty weight of glider and my weight with chute. True I need to set the amount of ballast and bugs. The argument that if the pilot does not enter the glider weight the results are wrong. It is nearly impossible to design idiot proof equipment, because they always make better idiots. As for software vs direct measure, there is a reason I do not have a vario named after me. Good discussion though and perhaps someone with a sharp pencil will design such a unit.

[[email protected]]

On Wednesday, April 20, 2016 at 6:35:08 PM UTC-7, Jonathan St. Cloud wrote:
> Not that I am arguing with anyone, but my flight computer, knows my flap position, it also knows when I dump water and for how long (LX 90xx). I have in the profile the empty weight of glider and my weight with chute. True I need to set the amount of ballast and bugs. The argument that if the pilot does not enter the glider weight the results are wrong. It is nearly impossible to design idiot proof equipment, because they always make better idiots. As for software vs direct measure, there is a reason I do not have a vario named after me. Good discussion though and perhaps someone with a sharp pencil will design such a unit.

Not gonna work during a winch launch, no matter what, and for many people (including myself, if we ever get one here), that's a big omission.

[JS]

During yesterday's flight I wondered how many times an AoA indicator would have been crying "The sky is falling!"
Seems OK for the C172 Family Truckster. Not sure how it would behave in turbulent narrow thermals or rotor, where AoA changes frequently.
Perhaps more aggravating than useful?
Jim

[kirk.stant]

On Saturday, April 23, 2016 at 12:10:26 AM UTC-5, JS wrote:
> During yesterday's flight I wondered how many times an AoA indicator would have been crying "The sky is falling!"
> Seems OK for the C172 Family Truckster. Not sure how it would behave in turbulent narrow thermals or rotor, where AoA changes frequently.
> Perhaps more aggravating than useful?
> Jim

Was your stall warning going off? Because that little vane or whatever they use on Cezznas these days is just a crude on/off AOA indicator, calibrated to go off just before stalling AOA.

If it's turbulent enough to affect AOA that significantly, i would think it would be nice to know - so as to speed up enough to stay out of the stall range?

I will admit that it wasn't ever a problem in the F-4; 78 lbs/sq ft at 540 knots doesn't get bounced around much...

Information is information - AOA provides direct information, in real time, of what your wing is doing with regards to producing lift. Airspeed does not - it just tells you how fast you are moving through the air. Both are useful, for different reasons.

Ever tried a really hard slip in a modern glider? Or a K-21, even? What does the airspeed show? Hmm, it sure flies nice at zero airspeed! A properly designed AOA system would work at pretty much any realistic yaw angle, so you could slip without having to guess how fast you are going. Nice to have since the FAA still wants slips to a landing during a checkride!

(Just joking a bit there, but you get the idea...).

Kirk
66

[Jonathan St. Cloud]

I think sometimes the Cessna stall warning tabs are affected by gravity too, not just AOA. I was in the pattern at Bishop, CA in a Cessna 340 (pressurized twin, cabin class) with a Vso of 64 (with vortex generators) flying 120 knots. It was turbulent and the stall warning horn kept going off in the bumps, checked both ASI's and GPS speed, controls felt firm, no mushing, so I ignored the warnings landed fine, checked the stall tab, it appeared to operate normally. It seems like flying into Minden or Lake Tahoe I had encountered much worse turbulence yet never had the stall warning horn. While we trust instruments, keep your mind in the loop.

On Saturday, April 23, 2016 at 8:20:32 AM UTC-7, kirk.stant wrote:

> Was your stall warning going off? Because that little vane or whatever they use on Cezznas these days is just a crude on/off AOA indicator, calibrated to go off just before stalling AOA.
>
> If it's turbulent enough to affect AOA that significantly, i would think it would be nice to know - so as to speed up enough to stay out of the stall range?
>
> I will admit that it wasn't ever a problem in the F-4; 78 lbs/sq ft at 540 knots doesn't get bounced around much...
>
> Information is information - AOA provides direct information, in real time, of what your wing is doing with regards to producing lift. Airspeed does not - it just tells you how fast you are moving through the air. Both are useful, for different reasons.
>
> Ever tried a really hard slip in a modern glider? Or a K-21, even? What does the airspeed show? Hmm, it sure flies nice at zero airspeed! A properly designed AOA system would work at pretty much any realistic yaw angle, so you could slip without having to guess how fast you are going. Nice to have since the FAA still wants slips to a landing during a checkride!
>
> (Just joking a bit there, but you get the idea...).
>
> Kirk
> 66

[[email protected]]

We all have stall warning horns/lights in ag spray planes. Almost everyone has disconnected them. Another useless instrument when it comes to flying that is necessarily stick and rudder.
Dan

[kirk.stant]

On Saturday, April 23, 2016 at 11:59:42 AM UTC-5, wrote:
> We all have stall warning horns/lights in ag spray planes. Almost everyone has disconnected them. Another useless instrument when it comes to flying that is necessarily stick and rudder.
> Dan

Dan, while I tend to agree that most stall warning indicators are of marginal use if you are current and have lots of experience in a particular plane, remember we are talking about glider pilots - most do not fly that much each year, and many may fly several different types frequently.

Heck, if you are comfortable in your plane, hardly any instrument is really needed. But if I could only have one - it would be a good AOA indicator :^)!

Kirk
66

[2G]

On Saturday, April 23, 2016 at 3:19:47 PM UTC-7, kirk.stant wrote:
> On Saturday, April 23, 2016 at 11:59:42 AM UTC-5, wrote:
> > We all have stall warning horns/lights in ag spray planes. Almost everyone has disconnected them. Another useless instrument when it comes to flying that is necessarily stick and rudder.
> > Dan
>
> Dan, while I tend to agree that most stall warning indicators are of marginal use if you are current and have lots of experience in a particular plane, remember we are talking about glider pilots - most do not fly that much each year, and many may fly several different types frequently.
>
> Heck, if you are comfortable in your plane, hardly any instrument is really needed. But if I could only have one - it would be a good AOA indicator :^)!
>
> Kirk
> 66

Gliders are flown substantially differently than most other aircraft: we circle just above stall speed at high bank angles. A stall warning would be going off continuously and would be more annoying than anything. Above 30 degrees bank angle I find it impossible to stall the glider anyway; a stall will usually occur because of a gust. I don't know what an AOA indicator would add because AOA varies from the inner wing tip to the outer wing tip. The MOST important thing to do is to maintain coordinated flight. Maybe you could put an audible warning on the yaw string!

Tom

[kirk.stant]

On Friday, April 29, 2016 at 6:18:00 PM UTC-5, 2G wrote:

> Gliders are flown substantially differently than most other aircraft: we circle just above stall speed at high bank angles. A stall warning would be going off continuously and would be more annoying than anything. Above 30 degrees bank angle I find it impossible to stall the glider anyway; a stall will usually occur because of a gust. I don't know what an AOA indicator would add because AOA varies from the inner wing tip to the outer wing tip. The MOST important thing to do is to maintain coordinated flight. Maybe you could put an audible warning on the yaw string!
>
> Tom

Tom, in many respects gliders are flown just like fighter planes - either fast or hard turning, at varying g loads and weights. Which is why AOA is often used instead of airspeed in those conditions. This is not a stall warning system, but an indication of what the actual AOA of the plane is. It can be an averaged indication - the critical AOA will be the same once calibrated. Momentary excursions due to gusts are handled just like on the airspeed indicator - you ignore them!

Amazing how almost everyone who actually hasn't used a real AOA system dismisses the concept out of hand. Kinda reminds me of the Brits before WW2 who totally dismissed Frank Whittle's ideas about jets (after all, he was just a lowly Flight Lieutenant) and as a result missed out on possibly having jet fighters during the Battle of Britain...

Cheers,

Kirk
66

[kirk.stant]

On Friday, April 29, 2016 at 6:18:00 PM UTC-5, 2G wrote:

The MOST important thing to do is to maintain coordinated flight. Maybe you could put an audible warning on the yaw string!
>
> Tom

I don't agree. The MOST important thing is to not exceed stalling AOA. Below that, yaw (within limits) adds drag (or may help a bit - see discussions about slipping turns while thermalling) and may be less efficient; but you can still control your glider - exceed the critical AOA, and you are a passenger until you reduce it.

Airspeed indicators are required (which are indirect AOA indicators). Yaw strings or slip balls are not.

Kirk
66

[[email protected]]

The most important thing is not either of those two instruments, its your ass, and situational awareness. Most folks get into stall/spin trouble by not having a clue that they are flying on or approaching the edge. An instrument only helps when theres time to scan it, but your ass can tell you immediately whats going on.
Dan

[Dan Marotta]

Whittle... :-D

Dan - 5J

On 4/30/2016 8:01 AM, kirk.stant wrote:
> On Friday, April 29, 2016 at 6:18:00 PM UTC-5, 2G wrote:
>
>> Gliders are flown substantially differently than most other aircraft: we circle just above stall speed at high bank angles. A stall warning would be going off continuously and would be more annoying than anything. Above 30 degrees bank angle I find it impossible to stall the glider anyway; a stall will usually occur because of a gust. I don't know what an AOA indicator would add because AOA varies from the inner wing tip to the outer wing tip. The MOST important thing to do is to maintain coordinated flight. Maybe you could put an audible warning on the yaw string!
>>
>> Tom
> Tom, in many respects gliders are flown just like fighter planes - either fast or hard turning, at varying g loads and weights. Which is why AOA is often used instead of airspeed in those conditions. This is not a stall warning system, but an indication of what the actual AOA of the plane is. It can be an averaged indication - the critical AOA will be the same once calibrated. Momentary excursions due to gusts are handled just like on the airspeed indicator - you ignore them!
>
> Amazing how almost everyone who actually hasn't used a real AOA system dismisses the concept out of hand. Kinda reminds me of the Brits before WW2 who totally dismissed Frank Whittle's ideas about jets (after all, he was just a lowly Flight Lieutenant) and as a result missed out on possibly having jet fighters during the Battle of Britain...
>
> Cheers,
>
> Kirk
> 66

--
Dan, 5J

[[email protected]]

On Saturday, April 30, 2016 at 9:07:40 AM UTC-5, kirk.stant wrote:
> On Friday, April 29, 2016 at 6:18:00 PM UTC-5, 2G wrote:
>
> The MOST important thing to do is to maintain coordinated flight. Maybe you could put an audible warning on the yaw string!
> >
> > Tom
>
> I don't agree. The MOST important thing is to not exceed stalling AOA. Below that, yaw (within limits) adds drag (or may help a bit - see discussions about slipping turns while thermalling) and may be less efficient; but you can still control your glider - exceed the critical AOA, and you are a passenger until you reduce it.
>
> Airspeed indicators are required (which are indirect AOA indicators). Yaw strings or slip balls are not.
>
> Kirk
> 66

I think you got it right, Kirk. Not all of us can be fighter pilots but we all can learn about AOA and how critically important it is in most flight regimes. Every couple of years I read my "Stick and Rudder" by Langewiesche.. He was a very smart man and put things together 70 years ago that are still a mystery to many of us.

[Dave Nadler]

On Saturday, April 30, 2016 at 10:01:15 AM UTC-4, kirk.stant wrote:
> Amazing how almost everyone who actually hasn't used a real AOA
> system dismisses the concept out of hand.

Some years ago, I was asked to evaluate an AOA sensor (vane type,
mounted on a Duo, with an audio warning). Even in a relatively
smooth thermal, it squawked often for no good reason (I'm pretty
familiar with the Duo and my thermalling doesn't really suck bad).
With sensitivity turned down, it didn't give indication until
too late to be helpful (yes, I know, I already stalled).

I don't know whether it is possible to make something that
is helpful safety-wise. With a gear-down interlock it won't
help the guy thermalling low.

For what its worth from somebody who has tried one in a glider,
Best Regards, Dave

[Skypilot]

I don't know if using AoA for safety would really work in a glider unless it was mounted and calibrated to remove gusts and other abnormalities. One idea would be a speed sensor matched with AoA over a 10 second gap below 1000'agl. Then all it does is say "speed speed" like bitching Betty.

I guess it's important to point out that the is a big difference in pitch and AoA in our type of Ops.

I think they could be useful matched to a Johnson type of drag meter.

I.e. Flap setting vs speed in different thermal strengths.
AoA to fly on long skinny glides and near the ground.
AoA to fly with underpowered turbos
AoA to fly in wave

I guess at some point we will move to HUD's. Once we do that there will be a plethora of stuff available to us. I guess the speed to fly will be a pipper based on track and macready, perhaps it will default to AoA at stable critical times such as the classic low level stall spin.

Just a thought from someone who flew the death pencil "Metroliner" and the AoA was pretty important. :)

Justin



On Saturday, April 30, 2016 at 10:01:15 AM UTC-4, kirk.stant wrote:
Amazing how almost everyone who actually hasn't used a real AOA
system dismisses the concept out of hand.

Some years ago, I was asked to evaluate an AOA sensor (vane type,
mounted on a Duo, with an audio warning). Even in a relatively
smooth thermal, it squawked often for no good reason (I'm pretty
familiar with the Duo and my thermalling doesn't really suck bad).
With sensitivity turned down, it didn't give indication until
too late to be helpful (yes, I know, I already stalled).

I don't know whether it is possible to make something that
is helpful safety-wise. With a gear-down interlock it won't
help the guy thermalling low.

For what its worth from somebody who has tried one in a glider,
Best Regards, Dave

[[email protected]]

I may be weird, but I see four scenarios in which an audio AoA meter would be helpful enough to me that I'm tempted to prototype one:

1. Aerotow, increasingly raucous warning as AoA approaches stall. Recognized by landing gear down, acceleration profile corresponding to aerotow, dynamic pressure has been close to zero since last time landing gear was up.

2. Winch launch, gentle progressive audio warning if AoA goes above or below optimal (calibrated best L/D AoA?), increasingly raucous warning as AoA approaches stall. Recognized by landing gear down, acceleration profile corresponding to winch launch, dynamic pressure has been zero since last time landing gear was up.

3. Thermaling, gentle progressive audio warning if AoA goes above or below optimal (calibrated minimum sink AoA?), option to provide stall AoA warning if it's not annoying. Recognized by landing gear up, appropriate dynamic pressure, acceleration magnitude greater than 1G for 10 seconds or so.

4. Approach, gentle audio warning if AoA goes above or below calibrated approach AoA, increasingly raucous warning warning as AoA approaches stall. Recognized by landing gear down (combined with gear warning if dive brakes open), dynamic pressure has not approached zero since last time landing gear was up.

AoA measurement filtered by a few seconds of moving average combined with gust filtering. If it's quiet, I'm almost certainly doing OK, only annoying if I get out of the envelope for a given scenario. Fairly trivial to program using a pair of available cheap high resolution digital interface differential pressure sensors and a two port probe. Recognizing the difference between aero and winch launch will likely take a bit of cleverness.

[kirk.stant]

On Saturday, April 30, 2016 at 12:57:10 PM UTC-5, Dave Nadler wrote:

> Some years ago, I was asked to evaluate an AOA sensor (vane type,
> mounted on a Duo, with an audio warning). Even in a relatively
> smooth thermal, it squawked often for no good reason (I'm pretty
> familiar with the Duo and my thermalling doesn't really suck bad).
> With sensitivity turned down, it didn't give indication until
> too late to be helpful (yes, I know, I already stalled).

Nice to know someone is trying, but it sounds like the AOA sensing mechanism needs developing - if the overall AOA of the Duo's wing was jumping around that much, I would think performance would suffer!


> I don't know whether it is possible to make something that
> is helpful safety-wise. With a gear-down interlock it won't
> help the guy thermalling low.

As always, the devil is in the details - how to measure and display useful information.

If you think about it, we already use a coarse AOA indication while thermalling - nose position relative to the horizon. We then crosscheck against airspeed (and "feel") and adjust accordingly. That really wouldn't change with a working, glider-optimized AOA system, it would just allow better calibration of our "feel" vs what is really happening - and provide a useful warning if we misjudge and get too slow.

>
> For what its worth from somebody who has tried one in a glider,
> Best Regards, Dave

Interesting. Thanks.

Kirk
66

[Dave Nadler]

On Saturday, April 30, 2016 at 8:43:09 PM UTC-4, Skypilot wrote:
> ...calibrated to remove gusts and other abnormalities...

Except that's when a wing stalls...

> One idea would be a speed sensor matched with AoA over a
> 10 second gap below 1000'agl.

It takes less than 10 seconds to spin into the ground.

> ...I guess at some point we will move to HUD's...

To interfere with our vision of thermal clues and traffic?

Always trade-offs...
Hope that helps clarify,
Best Regards, Dave

[2G]

On Saturday, April 30, 2016 at 7:07:40 AM UTC-7, kirk.stant wrote:
> On Friday, April 29, 2016 at 6:18:00 PM UTC-5, 2G wrote:
>
> The MOST important thing to do is to maintain coordinated flight. Maybe you could put an audible warning on the yaw string!
> >
> > Tom
>
> I don't agree. The MOST important thing is to not exceed stalling AOA. Below that, yaw (within limits) adds drag (or may help a bit - see discussions about slipping turns while thermalling) and may be less efficient; but you can still control your glider - exceed the critical AOA, and you are a passenger until you reduce it.
>
> Airspeed indicators are required (which are indirect AOA indicators). Yaw strings or slip balls are not.
>
> Kirk
> 66

Well, I definitely take issue with "ASI are indirect AOA indicators". This falls into the category of "it either is or it isn't" category.

I am not dismissing AOA indicators since I have never flown with one. I think I will put one on for my next flight (a yaw string taped to the side of the canopy).

You are very dismissive of the roll of gusts: a former FAA administrator was killed by one (and his inability to deal with it). You also did not comment on my comment about not being able to stall a glider above a 30 degree bank angle. Recovering from a straight-ahead stall is a ho-hum event at best; dealing with stall-spins is a totally different animal.

Tom

[[email protected]]

2G makes some very valid points. Let me add, A slow shallow turn is the killer of many a not-so-wise pilot. The steeper the turn the safer for the following reason;
At steep bank angles as we all know a guy has to hold a whole hell of a lot of back pressure. This high back pressure tells any fool that he had better be carefull with these high AOA's.
Secondly, in this configuration, try increasing the bank angle, the aircraft will not immediately spin but will fall inward trying to drop its nose attempting to gain the speed needed or lesson the AOA it needs to keep flying. The aircraft WANTS to keep flying and will do what is needed on its own if allowed.

In my opinion while a "working" AOA would be somewhat helpfull, both an AOA and an airspeed can lead to a false sense of security. But understanding the dynamics of turning flight is the best key to real safety. Langshweger or however you spell/pronounce his name in the classic "Stick and Rudder" knew this 60 years ago.
Dan

[kirk.stant]

On Sunday, May 1, 2016 at 8:20:34 PM UTC-5, wrote:

> In my opinion while a "working" AOA would be somewhat helpfull, both an AOA and an airspeed can lead to a false sense of security. But understanding the dynamics of turning flight is the best key to real safety. Langshweger or however you spell/pronounce his name in the classic "Stick and Rudder" knew this 60 years ago.
> Dan

Dan, please explain how a "working" AOA indicator could lead to a false sense of security? I know how a working airspeed indicator can, and I also (from personal experience - war story) know how a "not-working correctly" AOA indicator can lead to a false sense of security; which is why you are taught to cross check the two to make sure they are both working and make sense..

Last comment on AOA vs Airspeed. AOA is a control instrument, like an attitude indicator or yaw string. Airspeed is a performance instrument, like the altimeter and variometer.

Kirk
66

[kirk.stant]

On Sunday, May 1, 2016 at 7:36:58 PM UTC-5, 2G wrote:
>
> Well, I definitely take issue with "ASI are indirect AOA indicators". This falls into the category of "it either is or it isn't" category.


No. Airspeed is exactly that - how fast your glider is moving through the air. I can be at 60 knots and zero angle of attack, or at 60 knots and stalling angle of attack (depending on the plane). But your glider will only stall at the stalling AOA, period. The reason we use ASI is tradition and ease of measurement, and the fact that in most flying airspeed is a suitable stand-in for AOA - assuming you know the speeds for various wing loadings, bank angles, configurations etc... But if you forget that you are heavy, and bank a bit too much, and slow down a bit too much, and your plane will stall (yes, most gliders may not), and you remember the wrong airspeed, or you are in a new-to-you plane or you are tired and forget...airspeed can lie - AOA cannot. Period. Luckily for us, gliders are usually extremely forgiving, and we can get by on "feel". Most of the time. Apparently power planes are not so forgiving, which is why almost all require at least a basic AOA system: a stall warning indicator! The Pawnees I tow with definitely have a big red light in the middle of the panel hooked up to a vane on the leading edge - tripped when approaching stall AOA. Interestingly, the Supercub I also tow in does not - I guess cub pilots were either better trained or less valuable ;^)


> I am not dismissing AOA indicators since I have never flown with one. I think I will put one on for my next flight (a yaw string taped to the side of the canopy).

It's a fun little experiment. But not very practical in the real world for a bunch of reasons.

> You are very dismissive of the roll of gusts: a former FAA administrator was killed by one (and his inability to deal with it). You also did not comment on my comment about not being able to stall a glider above a 30 degree bank angle. Recovering from a straight-ahead stall is a ho-hum event at best; dealing with stall-spins is a totally different animal.

Not at all, I've had my share of upsets in gusty thermals. And the fix is the same whether you fly airspeed or AOA/Attitude: fly faster by lowering your AOA to give you more pad above stall. As far as not being able to stall a glider above 30 degrees of bank, so what? That just means that you are elevator limited, but you still want to fly as close to optimum AOA as possible, and it's nice to know what that is. Or do you just pull till the stick is in you lap and live with whatever it gives you? Somehow, I don't think that is an efficient way to thermal. Oh, and some gliders will stall very nicely at steep bank angles, by the way; the fabulous 2-32 comes to mind!

A stall only becomes a spin if you are unprepared for it and respond incorrectly. Knowing why you are about to stall is a good start, IMO. If you are focusing on airspeed to determine if you are stalled or flying, you are focusing on the wrong parameter - you need to decrease your AOA before you can fly, regardless of airspeed!

Cheers,

Kirk
66

[[email protected]]

As to an AOA leading to a false sense of security, the key word is "working" as we have discussed all of the variables that need to be accounted for to have a usefull gayge for sailplane application. But given someone developes an AOA that accounts for them, there is the gust factor. This is the one variable that in my opinion can not be eliminated. Since they occur so instantaneously, if a guy is relying on the AOA or for that matter the airspeed indicator to tell him hes in trouble, its already too late.

Secondly, while the pawnee and most other spray planes have a stall warning based upon airflow they are worthless. So much so that as I stated in an earlier post, most duster pilots either disengage them or ignore them.

The very first thing I do when flying an unknown aircraft or one I have limited experience in, I take her up and run a stall series. I want to directly know what she is like in slow flight and what she tells me around the slow end of the envelop. I also want to know how she actually stalls. Case in point that wonderfull 2-32. She breaks sharply and rapidly with not much warning, as does my old pilatus. In fact I do this with every aircraft I am tasked with flying. Pawnees vary in their behavior. I once flew one which would fall off rapidly and suddenly to the right if just a little right rudder was held in near the stall, but was as gentle as a pussy cat when flown on the edge to the left. She had to have been crooked due to all her previous accidents and repairs.

What I am attempting to do in each of these excercises is teach my butt and flight senses to memorize the symptoms and behavior of the craft way before or irrespective of what the flight manual numbers say or for that matter what the airspeed says. Our pawnee back at my home club in FL is a good 20 mph off. Reading 80 mph indicated is in actuality 60 mph. If a guy doesnt "feel" what that pawnee is doing and just goes by the indicated airspeed he is gonna be in deep ****.
Dan

[[email protected]]

Rereading some of the earlier posts, you brought up the same point I am trying to makeOn Wednesday, April 13, 2016 at 9:56:34 AM UTC-5, Soartech wrote:
Too many skilled pilots continue to spin in which makes me wonder if their ships don't give any hint of approaching stall or what else is going on.

"I think a lot of pilots, both low-time and skilled, spend way too little time exploring the corners of the envelope of their gliders - both high and low speed, negative to positive Gs, shallow to steep banks.

Get high and practice trying to kill yourself in the pattern, to the point that you recognize instinctively a dangerous condition and apply the right corrective actions. This is a basic flying skill, NOT an intellectual exercise! "

Kirk
66

[Skypilot]

QUOTE=Dave Nadler;924639]On Saturday, April 30, 2016 at 8:43:09 PM UTC-4, Skypilot wrote:
...calibrated to remove gusts and other abnormalities..

"Except that's when a wing stalls..."

I always thought they stalled when the Critical Angle of Attack was exceeded. Therefore if you could remove the inaccuracies of a vane type AoA it would be good.

"It takes less than 10 seconds to spin into the ground"


Yes but I cant help but feel if you never ended up in a fully developed spin below 1000' it might be a good start. I suspect that at the end of a 5 hour task having a system that says "hey numpty, you are thermalling below 1000', you are in ery little lift and I have noticed that you keep increasing your AoA, if you continue to do this we might enter a spin from which you may not be able to recover from before we hit the ground. Why don't you unload the wing a little and increase speed to give yourself a nice tight circle with a reduced AoA



...I guess at some point we will move to HUD's..

"To interfere with our vision of thermal clues and traffic?"


Yeah because no cockpit I have ever seen has flarm, moving map or instruments below the coaming. I mean no pilot looks at all that stuff when they should have their heads outside do they ???. Yet one simple piper could give you track, speed to fly and selectable FLARM



kind regards

Justin

[Bruce Hoult]

On Saturday, April 30, 2016 at 5:01:15 PM UTC+3, kirk.stant wrote:
> Amazing how almost everyone who actually hasn't used a real AOA system dismisses the concept out of hand.

Not me. I'd love one. I merely stipulate that it needs to measure the actual AOA (whether by a vane or differential pitot pressures I don't care), and not *assume* the AOA because of some guesstimated data input to a PDA or "vario" or whatever.

I'm a computer programmer with experience doing embedded stuff. As a result, I have much less faith in them than many others do!

Also, it's FAR easier to optimise something -- that is, to find the maximum or minimum of a smooth function -- than it is to precisely predict the location of a discontinuity such as a stall.

[Dan Marotta]

On 5/1/2016 8:09 PM, kirk.stant wrote:
> you need to decrease your AOA before you can fly, regardless of airspeed!
Some folks just don't get the above simple statement and will argue the
point to the death (hopefully figuratively). Frankly, I'd love to
replace my ASI with a good AoA, but I don't see anything available that
would fit the bill, not to mention the sometimes not so thoughtful FAA
that would bust you for not having an ASI. And yes, Virginia, you
/_can_/ fly in a 90 deg bank without stalling (for a little while, at
least). Note that I didn't say, "level", a word often left out in these
discussions.
--
Dan, 5J