Add failsafe when someone turns off transmitter before disconnecting Lipo

[GoogleCodeExporter]

What steps will reproduce the problem?
1. tie down your arduCopter
2. turn on transmitter, connect lipo
3. spin up engines slightly to ensure all is working
4. turn off transmitter

What is the expected output? What do you see instead?
- Ideally the motors should either stay at their current rate or perhaps slowly 
(or quickly?) turn themself off.  Certainly they shouldn't go to full power 
which is maybe what they dol.

Original issue reported on code.google.com by rmackay...@gmail.com on 26 Nov 2010 at 6:57

[GoogleCodeExporter]

I've implemented a safety check in ArduCopterNG and you can see the code here:  

http://code.google.com/p/arducopter/source/browse/trunk/ArducopterNG/Radio.pde  
(search for "// special checks for throttle").

The way it works is:
   - when the throttle is held low (i.e. MIN_THROTTLE+100) for 1second the safety check engages
   - the safety check is released if the throttle is moved up slowly but if it's moved up quickly it will disarm the engines

We need to be a little careful of bad interactions with the upcoming altitude 
hold code if it allows people to hold throttle low for > 1 second.

Original comment by rmackay...@gmail.com on 28 Nov 2010 at 10:27

• Changed state: Done