Failure of the tail retraction jack ram seals can also prevent the main gear being retracted and/or locking down as the fluid would cycle around the circuit and pressure would not build up.

This problem is identified by selecting the gear down before engine start. On start up the gear lever flicks into idle when pressure builds to 1100psi. If it does not click into “Idle”, you don’t go fly. This of course could also indicate failure of the hydraulic pump.

Initially the blow down bottle was connected to the main jacks only. A later modification added a shuttle valve to the tail retract jack so that all three legs could be blown down.