"the trigger valve is an OK cheap way to work doors But I've found it only works reliable when you've got a forward retracting gear that you use for the trigger strut. the air pressure in flight on that gear slows it down from retracting so all the gear have an opportunity to get up and tucked away before the switch is pressed, otherwise it's luck of the draw and if the trigger gear happens to not be the last gear up then the doors close on the other gear."





I use the buttons for the nose gear doors on most of my BVM sport planes, and find they work perfectly only if you slow the gear servo way down, like 4-5 seconds transition. This would not work for the electronic valves, of course. If you don't slow the servo down, you are absolutely right about snagging a door.

Ooops! I mis-spoke there. My KC and ARF Bandit use normal servo speeds and the N/G strut contacts the button. When the gear is coming up, the door must stay open until the strut is fully retracted, and when going down, although gear cylinder and door cylinder are opening simultaneously, the small volume air cylinder pops the door open faster than the gear cylinder can pull the gear down.

On my BCARF with the eccentric arm that is driving the button, then the servo must be slowed down to work. Same deal on other planes I have had with the button pushed by the BVM or similar retract cylinder.