Recently, we had an issue with the Aux hydraulic system while operating the cargo ramp. While manually operating the ramp in position 4, the the ramp would begin to lower uncommanded. The original thought was the return line check valve was bad. However, after canning one from another plane to trouble shoot, the same issue was occurring. During all other phases of manual operation, the ramp was operating perfectly, locking pressure was at about 650psi, unlocking was 720psi. Virtually everything was changed out and the problem was still occurring.
We finally decided to open up the doghouse panel and found the ramp locking cylinder was bypassing, but only in manual position 4. This was obviously a very uncommon occurrance and just wanted to be able to help out if this happens again
Flying an empty C-130 around Vietnam and a flight engineer buys the beer.