Cessna Twin Hydrolics

[tolakuma manki]

Cessna twin, one landing gear won't retract in flight. Will on jacks.
Hydrolic system.
Flaps work normal.
Thoughts please

[stevef]

Which Cessna model? Which landing gear: nose or main?

[tolakuma manki]

Which Cessna model? Which landing gear: nose or main?
404 main landing gear

[piggybank]

I do not know your specific model but comment may be valid. Has any avionics work been done recently ref wiring to undercarriage microswitches? I had an undercarriage problem similar on a Puma helicopter after 'someone' sprayed the internal receptacles of the electrical socket with can of spray paint. In our case the nose undercart started to raise, got half way and then dropped down again.

[Big Pistons Forever]

I had a similar problem happen on a C 421. The valve on the emergency nitrogen bottle was leaking which pressurized the down lines.

[grounded27]

The simple nuts and bolts test is (if you can pin your gear). On the ground, retract and take a long handled screw driver. Apply it to the retract actuator and listen from the other end, it may be by-passing internally, enough to work on the ground but not in flight, heat is another factor as compared to the other gear.

[tolakuma manki]

The valve on the emergency nitrogen bottle was leaking which pressurized the down lines. Thanks, but no pressure in outlet fitting of Nitro bottle

Apply it to the retract actuator and listen from the other end, it may be by-passing internally, enough to work on the ground but not in flight,Won't unlock in flight

[stevef]

Further to the other good suggestions:
What rig are you ground testing the gear with? Is it producing constant normal system pressure? It it's retracting the gear at a lower pressure in the hangar, perhaps the seal isn't leaking to the other side of the ram, as it might when using the engine-driven hydraulic system at full pressure. I'd be tempted to remove the actuator and test it at 1.5 x normal px with the return port uncapped to see if there's any leakage.
The other possibility is (I may well be wrong as I've not worked on a Titan for a long time) is that the downlock microswitch on the actuator is defective, which is sending a pressure cut-off signal to the hydraulic system once the other gears have retracted. But that doesn't explain why the system works fine when the a/c is on jacks. It would be interesting to see the system hydraulic/electrical schematic. http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/confused.gif

Has it got a spring-loaded downlock inside the actuator?

[tolakuma manki]

Has it got a spring-loaded downlock inside the actuator?
Yes
System requirement same on ground and in air.
400 -500 psi ending with 1700 to finis uplock

[tolakuma manki]

as you were told already.
Really
Have good idea what is already.
Can't pull actuator from bottom and try, must get from overseas, want to make sure anything else might have missed