Hi Nuno:

I have installed in my Skymaster F-16 1/8 the Air Micro Switch from BVM (part No.: BVM # 5753 at USD $ 27.50).

You can find it at:

http://www.bvmjets.com/Pages/Catalog/air.htm

I have also installed the Tamjets Gear Fail Safe and it have been working very nice. I have set the activating pressure in 50 pounds. After the gear is retracted, the strut push the button in the swicth through the lever and air flow to the doors cylinders closing them.

When gear is extended, the strut release the button of the Air Micro Switch and gears and doors open simultaneoulsy.

Regards

Guillermo