Fellow racers

I thought I would share a radio operated airplane release mechanism I built for planes that do not have full range throttle control.

The purpose of the release is to allow me to practice when there is limited support at the field. The mechanism is servo driven off of a spare channel, and has a separate receiver, battery and switch. I believe the set up is as safe as typical restraints and the fact the servo or radio system that releases the plane is not turned on until after the plane is started and I am behind the plane gives added insurance of low consequence from an unintentional release.

The mechanism is pinned to the ground using a stake suitable for the surface condition, in my case I drive a 12" long philips screwdriver through the mechanism.
The planes tail, that has a pre-drilled hole is placed in the release and the spring loaded pin is placed through the tail and locked in place with the servo rod.
The release is left turned off.
The engine is run up.
I then move behind the airplane and turn on the power and move to my flying position. I then toggle the spring loaded switch on my transmitter which in turn disengages the spring loaded pin releasing the plane. I have used the mechanism several times on my Q500 airplanes and have drilled my Q40's for the mechanism as well.
In the testing I initially used a spring that was to weak to disengage the pin when the pull of the airplane added to much friction. A slightly heavier spring now gives a real positive release.


The equipment I use:
Hitec MG225 servo
Hitec 9 ch receiver (came with the radio, but I only use 6 and 7 channel receivers in my racers)
LIPO battery, regulator and switch (spare setup I use in the planes)

Alternates.
When I first designed the system I was going to only use a servo extension from the plane to actuate the release, I would use a connecter that would come free when the plane was launched. Since I built this mechanism after I had built the planes this was not in place, but could be done on new planes, one would need to play with different connector types to get a good release, this seems a pretty simple problem to solve. In addition I would put a separate switch in the servo lead to prevent a glitch.

The key safety element is to ensure you use a channel that is programmed to a switch that cannot be accidently engaged. This is simple to do with the Hitec system probably can be done with most other brands and I am sure a second switch could even be programmed to the sequence for added security although I have not felt the need to do this.

Of course safety is always important and I do feel comfortable with this arrangement. I know many people self launch Q500 and even Q40's and this I feel is a safer alternative for me.

wkevinm