power pack repair

[JAG]

Steve - thank you for your detailed response and tips. I feel better about myself now for struggling with this damn thing, and truly appreciate the "pro-tips". Disappointing to hear that your power pack was not "plug and play" like they describe; you have given some good advice that I will use on the install of mine.

Cheers,
Jeff

P.S. the scars on the back of my left hand I will wear with pride - for the memory of that damned 4th bolt...

[SteveG]

A few random additional thoughts on this project by someone who has been there and learns everything the hard way, in the hopes that they may be of some value to others working in the same area. Employ at your peril, your mileage may vary.

Start threads on all fittings and bolts while assembly is loose. Misalignment can be pulled into position with mechanical advantage of threads but immovable misalignment will prevent fitting nuts from starting without the risk of cross-threading. Hand tighten in sequential order before wrench application.

Verify actuation linkage aligns with power pack shaft before final torque of fitting nuts and mounting bolts. The rod assembly passes through a bushing before engaging the manifold shaft and there is no adjustment for this alignment, it is fixed by the structural geometry.

It is likely that the clevis end of the control linkage will require adjustment once power pack position is finalized. While moving the selector handle from full down to full up observe that stop to stop rotation on the manifold shaft is obtained without panel interference.

Observe that cam on manifold shaft ,when rotated into position, depresses roller arm of switch which in turn operates switch correctly. This should have been adjusted by the overhauler but.... trust but verify.

Cox will return the unit without safety wire in the mounting screws of the switch and switch shroud. This is intentional on their part, using lock washers in lieu of safety wire.

[mshac]

Originally Posted by SteveG

A few random additional thoughts on this project by someone who has been there and learns everything the hard way, in the hopes that they may be of some value to others working in the same area. Employ at your peril, your mileage may vary.

Start threads on all fittings and bolts while assembly is loose. Misalignment can be pulled into position with mechanical advantage of threads but immovable misalignment will prevent fitting nuts from starting without the risk of cross-threading. Hand tighten in sequential order before wrench application.

Verify actuation linkage aligns with power pack shaft before final torque of fitting nuts and mounting bolts. The rod assembly passes through a bushing before engaging the manifold shaft and there is no adjustment for this alignment, it is fixed by the structural geometry.

It is likely that the clevis end of the control linkage will require adjustment once power pack position is finalized. While moving the selector handle from full down to full up observe that stop to stop rotation on the manifold shaft is obtained without panel interference.

Observe that cam on manifold shaft ,when rotated into position, depresses roller arm of switch which in turn operates switch correctly. This should have been adjusted by the overhauler but.... trust but verify.

Cox will return the unit without safety wire in the mounting screws of the switch and switch shroud. This is intentional on their part, using lock washers in lieu of safety wire.

SteveG, thanks for your tale of the emotional roller-coaster that is DIY repair work! Your story reminded me of replacing my rear alternator, and having to remove it AGAIN due to a "bad" OH'ed unit. It may not be quite the job the powerpack R&R is, but the emotions were very similar! I do believe I had an extra finger or two of scotch that evening!

[Learjetter]

July 2024:

Cox airparts will overhaul 9881200-1 ('77 G-model) powerpack for $4242 + parts with a 3-6 week lead time.

Power Packs Plus will exchange for $4975 (+ $10K qualifying core)

Aerospace Turbine Rotables says they've never heard of part number 9881200-1.

QAA in Tulsa say they cannot IRAN or OVHL.