"Airball" AoA / sideslip instrument

[ihab]

Dear friends,

I have been working for a while on an idea for a new display of AoA and sideslip information. I just got a demo video up so I thought I'd share it. This is intended to enhance safety, flight training, and general fun, for light VFR aircraft like the Sonex. Some notes before we start:

1. This is intended to be part of an aircraft PFD, even though so far my demos run on phones and tablets; and
2. This can be added to any PFD with an AoA probe as made by Garmin, Dynon and others as a simple software patch only.

The basic display is a "ball" that shows "where the relative wind is coming from" (and is therefore sensitive to AoA and angle of sideslip) and the diameter of which is proportional to IAS. It is shown against a "totem pole" with annotations, and a "cow catcher" at the bottom shows your stall AoA. This can be shown alone or with other information to create a complete PFD:

airball-analog.png (14.08 KiB) Viewed 3486 times

airball-pfd.png (50.63 KiB) Viewed 3486 times

A video of the simulator (Airball on an Android tablet with the X-Plane flight sim) is here:

https://www.youtube.com/watch?v=vfteJ_cBS_c

A high level description of the idea: http://goo.gl/wUY9AM
Download the Android app: https://play.google.com/store/apps/deta ... ball.phone
Android app instructions: http://goo.gl/trHTH0
Github repo for app: https://github.com/ihab/airball-for-android

Please let me know what you think, and if this would help you in your flying. If it is helpful, it is something that I think I'd like to convince avionics manufacturers to add to their PFDs.

Ihab

[Rynoth]

Iran, that's very cool that you designed all this yourself! This looks pretty similar in functionality to the "flight path marker" or "velocity vector" indicator found in military heads-up displays.

http://youtu.be/2Y4AgKOpUco

[ihab]

Hi Ryan,

This looks pretty similar in functionality to the "flight path marker" or "velocity vector" indicator found in military heads-up displays.

Wow thank you -- I didn't know about that.

And yes, this highlights one important question I'm puzzled by. If you put the airball on the same display as the regular artificial horizon, would the scaling be appropriate for AoA, or would it be too "coarse"? Of course, you could simply "cheat" and expand the AoA scale....

That said, my first hope for this instrument is to act as an aid to stick and rudder flying for cases where people don't really even need an artificial horizon. Or as an independent "mode" in a more traditional PFD that comes on during approach, or at low speeds, or something.

The most "pure" form of this is to have an airdata probe providing AoA, sideslip, static and dynamic pressure, and use that and nothing else to drive the "PFD" version of the instrument. But that's a bit -- well -- purist? ;)

Ihab

[ihab]

The most "pure" form of this is to have an airdata probe providing AoA, sideslip, static and dynamic pressure, and use that and nothing else to drive the "PFD" version of the instrument. But that's a bit -- well -- purist?

In fact, check out the "micro air data computer" sold by these folks:

http://www.aeroprobe.com/products-and-s ... a-computer

If you look at the top right corner of the flight test video, you can see a graph that is basically an Airball -- except they have positive AoA values "up" which is imho "wrong". ;)

In my proposal for putting this into an existing PFD, I would use AoA from the probe as usual, but would infer sideslip by scaling the lateral acceleration "ball" signal to the IAS. That would not be a perfect measurement of sideslip angle, but it would be good enough -- and would at least correct for the loss of sensitivity of the regular ball that happens at low IAS (when you need it most). And it would avoid having to install more airdata sensors, and allow the whole thing to be just a simple software patch.

Ihab