ORIGINAL: TLH101
There is a unit that will lower the gear automaticly if the air gets low, but I can't seem to think of the company that makes it right now. (CRS)
I was not refereing to Spring Airs or any other "spring down" system. Somewhere I saw a sensor that you could set to lower the gear if pressure was lost. It was adjustable for the pressure it would lower the gear. However, Spring Air retracts are about as "fail-safe" as it gets with air retracts.