This Viper has a clean and tidy servo installation that operates the nose gear door. Note that the
servo arm rotates 90° up, aligning the pushrod through the center of the servo arm. This gives the
servo maximum leverage to hold the door closed under air loads.
variety of techniques on my models, so
let’s go through them.
First is a simple button air micro
switch that should be located so that
the landing gear strut will hit the button
and pull up the gear door. The door air
cylinder is tied into the down retract air
line. This will open the door and lower
the landing gear together.
For the gear to go up, the door air
cylinder is tied into the up air line,
but this time the air micro switch is
located between the “T” and the door air
cylinder. When the button is pushed, the
air opens the gear door.
This is a simple and reliable system,
but it limits you to only having the gear
doors open whenever the gear is down.
This is not very scalelike for a P- 51 or
a BAe Hawk because their inner gear
doors are normally closed after the gear
A second option is a gear door
sequencer and there are many units
available that work well. I have an
airplane equipped with an Assan
gear sequencer that provides many
programming features at a reasonable
price. I have used it successfully for
I switched to this unit from an early
Jet Model Products sequencer to take
advantage of the timing and end-point
programming that the unit offers. If
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