Reliable Retracts

Retractable landing gear are mechanical and pneumatic contraptions that require proper installation, some periodic maintenance and preflight inspection if we are to expect reliable operation.


BVM kit instructions cover the installation of the units, struts and wheels. We would like to emphasize here that when using retract units with up locks, the struts and wheels should not touch or rub against any structure when in the gear up position.
Any such interference when the gear is trying to reach the "up lock" position requires extra force from the air cylinder. If that force is available and it does get to the up and locked position, there is a good chance that the gear will not unlock and extend because each cycle reduces the available air pressure.
If your model experiences a hard landing or hits a bad bump or hole in the runway such that the strut is bent even slightly, it may cause the above situation to occur.
Prior to the first flight of the day, cycle the landing gear system and watch the air pressure gauge on your pump or the mini gauge in your model to observe how much pressure drop occurs to retract the gear. Observe the gauge to be sure that it does not continue to drop while the gear is up. Sometimes it takes a few cycles for the cylinder "O"-rings to seal, especially on a cold day.
The BVM thin lube will usually help a lazy cylinder to reseal.

Sourcing an Air Leak

If you hear a hissing sound coming from the air selector valve, there is a good chance that the valve is not at fault, but rather a cylinder "O"-ring is not sealing and the air is bypassing and thus exiting at the valve.
Unless an air leak is very obvious, i.e. a disconnected tube, use a pair of forceps to pinch off sections of the system, starting at the air selector valve until you isolate the problem.
The solid color (verses translucent) air line tubing that BVM switched to in 2001 appears to be good for at least 3 years of use in a model and we sometimes pressurize the systems to 120psi.

High Flow Rate Selector Valve
BVM #5760


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