Maintenance thrills

stackj · #1 06-08-03, 11:34 PM

We had a little problem with the skymaster last Thursday. Jenny and I were practicing instrument approaches and I happened to notice that the front engine oil pressure gauge was indicating 0 psi. We immediately shut down the engine and secured it. (Looks like that can be fixed with a little wiring repair).

Jenny continued the approach, put the gear handle down upon intercepting the glide slope... Guess what??? No gear. Jenny initiated a go around, I manually pumped the gear down and we landed without incident.

I'm guessing the rear engine hydraulic pump has failed. (yes, this particular aircraft DOES have the redundant pump on the rear engine.) I have a spare pump which was on the previous front engine, but it had been sitting in the hangar for about 5 years with no use and it was loosely mounted to the old engine so there is a little corrosion on the face of the mounting flange. Here are my questions.

1. What should I do the the spare pump to insure it is serviceable before installing it. We checked with folks on rebuilds and prices. Apparently Cessna will not allow these units to be rebuilt, however, THEY will kindly send you a new one for only $1350.00. (If you will return the core --- hmmm, thought they said they can't be rebuilt... wonder why they want the core?)

2. What is the best way to recondition the mounting flange face? (should only require a little corrosion removal - it's not very deep.)

3. In going over the hydraulic system, I noted that if the check valve on the front system fails, you would also not get fluid flow to the gear system with only the rear pump running. It would only run backwards throught the other pump (Path of least resistance).

Any suggestions would be much appreciated.

rick bell · #2 06-09-03, 10:56 PM

confused? if you have two hyd pumps why would the gear not come down from the second pump that was also working? maybe it is something else, from my experience there are several things that can efect the gear

stackj · #3 06-09-03, 11:17 PM

Actually, I'm guessing it's not working.

stackj · #4 06-10-03, 06:40 AM

Sorry, I missed what you missed. When I shut down the engine, the good hydraulic pump shut down with it. The bad pump is on the engine that was still running.

stackj · #5 06-11-03, 06:36 AM

Wire is fixed. Oil pressure indications OK. wire was pulling tightly against terminal on engine cluster causing socket to make poor contact with pin on back of oil pressure gauge. If I had jiggled it in flight, I would have gotten my reading back... Oh well.