Cargo Ramp free falling

[Koza]

Hi, I work on a H model and I have a question about the Cargo ramp. It has a weird tendency to "free fall" whether there's 0 psi or 3,000 psi on the auxiliary system. When the grasshopper arms are disconnected it eventually falls to the ground in less than 15 minutes(from air drop position). This happens regardless of the sequencer being in 3N or 6N, and with only 2 people(average 200lbs each) on the ramp with no other weight.

It's a Sterer type manifold and by our books its allowed to free fall when hand pumping it up or down. However, at the rate that it drops to the ground it seems like there's something else wrong, but I dont know what. Anyone have any ideas?

[Steve1300]

That is not an uncommon problem. Various aircraft may have some drooping in the ramp if left alone for a period of time. Most of those drooping ramps take days to go from the airdrop position to the ground. The bad ones do it quickly.

There are only three problem areas that I personally have found. If there are others, I'd appreciate those of you who know to share the information.

The ramp and door maniforld control valve (stack valve) can allow the fluid to move and the ramp to go down under its own weight. That is the most rare of the three. The other two have been the actuators themselves. If fluid can get past one of the two ramp actuator piston seals, then the fluid that should actually lock the actuators in position will bypass the seal on one side or the other and allow the ramp to drop due to gravity.

Most often, the bypassing actuator has been the cause of the problem.

[tenten]

As the original post “History Repeated†of the "free falling" of cargo ramp with a control manifold valve manufactured by “Sterer†(the drop seems to be fast) within less than 30 minutes the ramp free falls from air drop position to the ground.

No leak detected on the ramp actuator lines, ramp operation checked manually and electrically no abnormality detected except the above.

1- Is it a normal drop with this type of control manifold valve?

2- If abnormal; which one of the three should I go for first? Left actuator, right, or the control manifold valve?

3-And is there any Possibility that the cause of this defect is due to valve sequencing problems caused by rotating the ramp manual control knob counter-clockwise?

3-Finally Is there any technique/tips to target the defective one?

Help will be appreciated.