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signal loss parachute

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After reading a couple threads on another board regarding people doing AP over inhabited areas and the threat of signal loss causing potential harm, I got to thinking about ways to make things safer in the event of a problem between the transmitter and plane. I came across this board while searching the web and saw the LoMA project.

Here's my question - is there any reason you couldn't use something similar to release a parachute? It seems like you could use something like a large model rocketry parachute, stuffed in a tube (heck, why not use a model rocket tube :)) with a deployment method TBD - perhaps a pilot chute of some sort to pull the main chute out of the tube. On loss of signal, the idea would be to have the add-on circuit deploy the chute.

If the ESC fries (from what I've read, this is probably the scariest situation, since the motor can go WOT) would that trigger the LoMA circuit? It would probably make sense to use a separate BEC for this, i'd think, either that or have the mechanical part of the project be essentially "normally open" - ie. it uses a small amount of current to keep from activating and if it loses power it releases the chute.

Any ideas?

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The important thing to keep in mind is that not all signal loss is permanent. So, you would want a solution that makes good decisions before it releases a parachute. Otherwise, the model would release it even when signal recovery was just a moment away.

LOMA could be used, but it will release the parachute upon the first loss of signal, even a short one. I do not think that is a good idea. This could be imroved by adding a longer lost signal validation time. However, a perfect solution would make decisions based on air speed, altititude, attitude, and such.

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true. However, given that AP frequently happens over inhabited areas or roads, you wouldn't want to have much "wait-and-see" time in the system. Obviously the best solution would be based on other factors than just signal loss, but for something simple, it sounds like your LOMA circuit would be a great starting point.

I could see a flowchart working something like:

0. normal function

1. signal loss recognized

2. timer starts

3. if signal restored < 1 second (adjustable value perhaps?) return to 0.

4. LoS condition reached

4a. motor power cut (NO relay between battery and ESC, perhaps?)

4b. recovery device deployed (NO relay preventing deployment before LOS)

Typically you'd be talking about perhaps 25-35 oz worth of weight. For a three pound plane, to slow decent to ~5ft/sec vertical, you need a chute with a diameter of approximately 13 inches. that doesn't require much space at all, and wouldn't weigh much either. the hardest part would be ensuring deployment.

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LOMA might not be a good candidate for the parachute control. When it boots up its output beeps three times to announce it is online. Its lost signal validation timer is well under 1 sec (closer to 200mS or so). The best solution would be to design something that is purpose specific.

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Oh, I'm sure. I only found your site last night, I just think LOMA would be a good starting point. I ordered a PIC programmer via Ebay, I haven't done that sort of stuff since college and it's been a while. :) Once I get the programmer and some ICs to work with I'll see what I can come up with.

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It sounds like an interesting project. Please keep us informed as you progress along.

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