AOA indicator poll.

I have uploaded a new video on https://bit.ly/aoaindicator.

It shows the display nearly without camera flickering... Video was taken in full light but I had to darken the exposure to avoid (mostly) a blueish effect due to saturation of the sensor with the green led.

This is nearer to the production version.

For me it is essential to have a relatively large color spot to notice it with the peripheral vision. That's why I will use leds with a wide beam, illuminating a reflector.

I've used a special plexiglas that catches the light internally, spreading it even more... But you still notice the up-down motion effect of the light.

It is possible with this material to build a kind of HUD, with the leds facing up through a prismatic plexiglas part.

New PCB almost designed...

On Tuesday, May 19, 2020 at 1:00:05 PM UTC-7, Luc Job wrote:
Hi!

I have developed last year a solid-state AOA indicator, based on a
differential pressure measurement (total pressure/pressure at angle)

Undoubtedly, this is a primary flight instrument to me:

-It shows where you are aerodynamically speaking, independently of
all the variable parameters: Load, flaps position, airbrakes...etc, and
does not need a calculation or interpretation to check if you are
flying right or not... And if the display is well done you will have a
clear indication of the ongoing tendency towards a safe or dangerous
situation.

-It give me an accurate indication to adapt the flaps position to stay
at the best glide angle through the whole speed range.

-It is a good indication of the optimal attitude during winch launch
and can prevent a high speed stall at high load factor.

Some pictures of my development are available he
https://bit.ly/aoaindicator
On the video the blinking effect is induced by the camera, the leds
simply fade in or out gradually, only the red one blinks at stall angle
or if the AOA rate of increase will induce a stall within 2 seconds...
you can see that the instrument works as good as its free
alternative...

The present system includes:

-A 5 leds indicator, red-amber-green-white-blue. The corresponding
AOA for each led is programmed in flight with a push-button.

-An audio input and output: Instead of adding a warning while flying
at higher AOA than the maximum Cz (minimum sink rate), the
instrument hashes the audio output of the vario gradually, cutting
the sound at stall. This is an excellent indication that something is
wrong without adding noise... You can continue to watch outside
while climbing at the best speed, and avoid to enter a spin in the
middle of others.

-A serial i/o for software upgrade and continuous transmission of the
data to another instrument.

-An optional light sensor to adapt the luminosity to the ambient light
level... But the indirect illumination and a better reflector (in
development) has proved that it is probably unnecessary.

The only hardware modification is the installation of an angled
pressure port at a suitable place: angle is not critical, but flow must
be as undisturbed as possible. On the DG I've put mine under the
nose, about 170 mm from the tip, where I had access to the outer
hull from the inside. I drilled a 2 mm hole and glued a small
pressure chamber inside to plug a 4 mm hose. That's all.

Power drain is lower than 20 mA @ 12V, less on ground as no led is
switched on... So no switch, but an internal polyfuse to avoid any
dangerous current drain... So it is simply added to the (fused)
instruments circuit.

Now as the system proves to be functional and efficient it's time to
do something with it.

Many options are possible:

1) I can order and sell PCB's only, with a BOM and the software...
This is obviously the cheapest way... But components are mostly
SMD... So you need an oven or a lot of patience and skill... Up to
you to make a box adapted to your needs. Price should be about $10
including shipping.

2) I can sell a complete kit with all the components, PCB, software,
connectors and box... Components are not expensive except the 2
pressure sensors ($35 each)... So I should be able to make this for
about $150...

3) If you prefer a complete instrument, ready to plug-in (except the
pressure port installation) the price should be in the 300-400$
range.

All this depends obviously on quantity... So if I have 1'000 orders it
might be significantly cheaper.

At first I need to know how many people might be interested... And
what is the best option for you.

At least we can fly again in Switzerland and France... So it might
take some time for me to build a website for this product...

Luc JOB
DG-800B

I am interested, but I would like to make the following design suggestions;

1) Make the LEDs remote from the PCB. Panel space is at a premium, in front and behind. I have a much better chance of retrofitting this in my panel if I can just drill a small hole in the panel and double stick the LED strip some place, while the "Box" with the PCB can get stashed behind the panel with some mounting tabs. Make sure the connector is small enough to go through a 1/4 hole that the LED strip then covers. This approach leaves you room for different display ideas in the future.

2) make the LED strip smaller. With the color scheme you have, the size seems too large, and makes install more challenging.

3) make the external ports easy to install, and modular. Perhaps there is a version that can be installed in the nose with the Pitot tube and the thermistor, and one for the belly as you have done. How small can the hoses be that go through the hull? would it work to mount on the side of the cockpit rather than underneath?

Sign me up for option #3 if you can incorporate the above changes.

Matt

On Friday, May 22, 2020 at 8:04:18 AM UTC-6, Luc Job wrote:
I have uploaded a new video on https://bit.ly/aoaindicator.

It shows the display nearly without camera flickering... Video was taken in full light but I had to darken the exposure to avoid (mostly) a blueish effect due to saturation of the sensor with the green led.

This is nearer to the production version.

For me it is essential to have a relatively large color spot to notice it with the peripheral vision. That's why I will use leds with a wide beam, illuminating a reflector.

I've used a special plexiglas that catches the light internally, spreading it even more... But you still notice the up-down motion effect of the light.

It is possible with this material to build a kind of HUD, with the leds facing up through a prismatic plexiglas part.

New PCB almost designed...

Nice.

On Tuesday, May 19, 2020 at 3:00:05 PM UTC-5, Luc Job wrote:
Hi!

I have developed last year a solid-state AOA indicator, based on a
differential pressure measurement (total pressure/pressure at angle)

Undoubtedly, this is a primary flight instrument to me:

-It shows where you are aerodynamically speaking, independently of
all the variable parameters: Load, flaps position, airbrakes...etc, and
does not need a calculation or interpretation to check if you are
flying right or not... And if the display is well done you will have a
clear indication of the ongoing tendency towards a safe or dangerous
situation.

-It give me an accurate indication to adapt the flaps position to stay
at the best glide angle through the whole speed range.

-It is a good indication of the optimal attitude during winch launch
and can prevent a high speed stall at high load factor.

Some pictures of my development are available he
https://bit.ly/aoaindicator
On the video the blinking effect is induced by the camera, the leds
simply fade in or out gradually, only the red one blinks at stall angle
or if the AOA rate of increase will induce a stall within 2 seconds...
you can see that the instrument works as good as its free
alternative...

The present system includes:

-A 5 leds indicator, red-amber-green-white-blue. The corresponding
AOA for each led is programmed in flight with a push-button.

-An audio input and output: Instead of adding a warning while flying
at higher AOA than the maximum Cz (minimum sink rate), the
instrument hashes the audio output of the vario gradually, cutting
the sound at stall. This is an excellent indication that something is
wrong without adding noise... You can continue to watch outside
while climbing at the best speed, and avoid to enter a spin in the
middle of others.

-A serial i/o for software upgrade and continuous transmission of the
data to another instrument.

-An optional light sensor to adapt the luminosity to the ambient light
level... But the indirect illumination and a better reflector (in
development) has proved that it is probably unnecessary.

The only hardware modification is the installation of an angled
pressure port at a suitable place: angle is not critical, but flow must
be as undisturbed as possible. On the DG I've put mine under the
nose, about 170 mm from the tip, where I had access to the outer
hull from the inside. I drilled a 2 mm hole and glued a small
pressure chamber inside to plug a 4 mm hose. That's all.

Power drain is lower than 20 mA @ 12V, less on ground as no led is
switched on... So no switch, but an internal polyfuse to avoid any
dangerous current drain... So it is simply added to the (fused)
instruments circuit.

Now as the system proves to be functional and efficient it's time to
do something with it.

Many options are possible:

1) I can order and sell PCB's only, with a BOM and the software...
This is obviously the cheapest way... But components are mostly
SMD... So you need an oven or a lot of patience and skill... Up to
you to make a box adapted to your needs. Price should be about $10
including shipping.

2) I can sell a complete kit with all the components, PCB, software,
connectors and box... Components are not expensive except the 2
pressure sensors ($35 each)... So I should be able to make this for
about $150...

3) If you prefer a complete instrument, ready to plug-in (except the
pressure port installation) the price should be in the 300-400$
range.

All this depends obviously on quantity... So if I have 1'000 orders it
might be significantly cheaper.

At first I need to know how many people might be interested... And
what is the best option for you.

At least we can fly again in Switzerland and France... So it might
take some time for me to build a website for this product...

Luc JOB
DG-800B



I'm kinda sorta interested. If the BOM can be sourced in the US....I'm even more interested. I'd like to play with one either way just to see what I can do with it.

Hi Matt!

2) make the LED strip smaller. With the color scheme you have, the size seems too large, and makes install more challenging.


Latest desing of the remote led strip is a bar of 47 mm height and 10.2 mm width, 8.2 mm thick, plus a 10x3 mm protrusion in the middle for the connector... I will setup the website with a download section so that you can download a drawing soon. The smallest useable connector I have found has a 8x3 mm section (or 10x3), so you should drill 3 holes of 3.5 mm next to the other and finish with a small file... Or if you have room to put it behind the panel, the slit for the display should be 47x7 mm.


3) make the external ports easy to install, and modular. Perhaps there is a version that can be installed in the nose with the Pitot tube and the thermistor, and one for the belly as you have done. How small can the hoses be that go through the hull? would it work to mount on the side of the cockpit rather than underneath?


There is presently no protrusion or pass-through tubes in the installation.

The system uses the pitot + static ports already installed on any glider, plus this famous angled pressure port.

It's only a drilled hole similar to the static ports.

It has to be under the nose where the angle is sufficient and in front of any perturbation (for example if the front tow hook is under the nose). Then you have to glue a small cap inside the hull (like for the statics, I think), with the tube connected to it parallel to the hull. Total thickness inside can be as low as 5 mm if you use a 4 mm PU tube. On the DG, most of the outer hull isn't easily reachable from inside except where the canopy hinge fits when closed... I had more than enough clearance to put my port there and this is precisely where the hull angle is acceptable. I will make pictures of my setup and post on the website. (glideraoa.com)

This is the simplest and most reliable setup, but if it is really impossible to have the pressure port under the nose tip for some reason, then it is possible to design a customized profiled protrusion with a 45° flat area and the port hole on it... And place it somewhere else but where the flow is undisturbed and far enough from the hull and without possible interaction with the tow/winch rope... Best place could be under a wing, if you have access... But I'm afraid that the customized antenna will be more expensive than the instrument.

Let me know first on which glider it is impossible to set it up under the nose... The Stemme, maybe... If I have a demand, I will study a suitable antenna for it... No tow rope problem.

Putting the pressure port 'antenna' on the side of the fuselage will make it sensitive to sideslip and this has to be avoided.

Last update before I order the new PCB's:

1) Having tested last season without it and without problems I will drop completely the light sensor... I see no situation where it is really useful with the present display... The colors can be seen in any situation except maybe with the direct sunlight over the display, that means very low sun from behind and In this case it will be hard to beat the sun anyway.

In the opposite situation, with the sun facing you, a light sensor on the panel will be in the shade and reduce the led's intensity instead of increasing it to allow you to see the panel despite the facing sun... Bad...

For these reasons I will replace the light sensor with a rotary encoder so that you can adjust the light yourself if needed. And the push function of the encoder will be for calibration (it needs a quite long push to trigger the calibration routine).

What do you think?

On Saturday, May 23, 2020 at 3:52:21 AM UTC-7, Luc Job wrote:
Last update before I order the new PCB's:

1) Having tested last season without it and without problems I will drop completely the light sensor... I see no situation where it is really useful with the present display... The colors can be seen in any situation except maybe with the direct sunlight over the display, that means very low sun from behind and In this case it will be hard to beat the sun anyway.

In the opposite situation, with the sun facing you, a light sensor on the panel will be in the shade and reduce the led's intensity instead of increasing it to allow you to see the panel despite the facing sun... Bad...

For these reasons I will replace the light sensor with a rotary encoder so that you can adjust the light yourself if needed. And the push function of the encoder will be for calibration (it needs a quite long push to trigger the calibration routine).

What do you think?

Since you only have to calibrate once, please make the calibration button on a cable you can hold in your hand while you fly for that one flight. then it can be unplugged and never seen again.

47 x 10mm sounds reasonable for the display. Thanks

For the connector, you should only need 6 pins, yes? Why not hard wire a 6 conductor phone cable out the back of the display, with an RJ-11 phone connector on the end. Then if I want to make a small hole, I can cut the connector, feed the cable through, and crimp on another RJ-11 once through the panel.

I understand about the port mounting now, thanks. One further question; is the sensor at the port, or do you need to run tubing back to the PCB? Much easier to run a wire to the PCB than a tube...

Matt

For the connector, you should only need 6 pins, yes? Why not hard wire a 6 conductor phone cable out the back of the display, with an RJ-11 phone connector on the end. Then if I want to make a small hole, I can cut the connector, feed the cable through, and crimp on another RJ-11 once through the panel.

Now that I have canceled the light sensor option I have gained some room for a RJ-25 plug on the PCB... I planned to use this kind of cable anyway... But it is 2.5x7 mm, so the hole through the panel will be only marginally smaller...

I understand about the port mounting now, thanks. One further question; is the sensor at the port, or do you need to run tubing back to the PCB? Much easier to run a wire to the PCB than a tube...

The sensor I2C data isn't supposed to travel more than inches away... And it is a differential gauge... So you should run a static tube to the sensor+ wiring to the panel... More complex than pulling another tube along the existing pitot and/or static... And the panel is probably less than 3-4 feets away... I'm using relatively flexible PU tubing for pneumatic applications.... It's stiff enough to be pushed everywhere, will not be pinched by chance, will not wear out and can still be bent much easier than nylon... This will be a part of the kit, I think.

And having about the same volume of air between the 2 ports and the sensors might induce a comparable damping of both sensors... I don't know if it has a real influence, but it can't hurt... Electronic damping has been introduced in the software as I manage to get the AOA data about 600 times/second.... A 1/10 second average value looks still instant and filters most of the unsignificant turbulence...

By monitoring the rate of change of this dampened value, I can predict if a stall is likely to be reached within 2 seconds... And display the corresponding warning before the critical AoA is reached, giving you some time to react before loosing control...

This is an intriguing idea. I've been interested in AOA since my university days in the 1970s. I flew my LS-3 for over a decade using a small bubble level to set the continuous flap setting of that glider (not perfect but not bad). And I had the side strings on my ASW 24 canopy for about the same amount of time (helpful at times but susceptible to gusts and slight slips/skids, as you said).

I'd be more interested in the kit than the finished instrument.

One concern: any port on the underside of the fuselage is subject to clogging when landing in dirt fields. It's not likely given the angles that you're talking about but I'd have to add one more item to my pre-flight checklist. Oh, well.

How robust are the pressure sensors? I assume if the electronics are not switched on that there is no danger of damaging them even if some idiot blows into a probe or port.

Chip Bearden
JB

How robust are the pressure sensors? I assume if the electronics are not switched on that there is no danger of damaging them even if some idiot blows into a probe or port.


The datasheet say that the proof pressure is 35psi.. about 2.3 bar... So not foolproof, but I bet that neither the mechanical ASI, nor the electronic calculator will do better...

The port is just under the nose... If you land into a swamp or a very soft field other parts of the plane will be clogged and need cleaning... It's not impossible that a bug crashes precisely there... But we have no MCAS to worry about if the AoA fails.