Something to keep in mind: if you fly part 91, overhauls are never mandatory.

PWC can specify them all they want, but the FAA only cares about inspections (checking for airworthiness), not overhauls (adding new life), for being airworthy.

So that's the legal side of things.

For the practical side, turbine engines are fairly robust to idleness, far more so than piston engines, despite how detailed the idle instructions might be in the manuals. It is entirely conceivable these engines would operate fine in service, especially if they did get at least some periodic ground runs.

If I was buying into this situation, I'd make the deal assuming the engines will have to be gone through. Once past the deal, I'd do a borescope, general inspection, run them for a bit (say 30 minute ground runs), then do an oil analysis.

If the borescope, general inspection, ground run data, and oil come back clean, I'd go fly. I'd probably do 20 hour oil analysis just to keep tabs on the bearings and gears for a bit.

If they don't check out, or problems develop later, then you made a deal with the financial margin to handle it.

I lay odds the engine will be fine, or the problems they have are not due entirely to idleness.

Mike C.

Can you share any numbers for estimates on the light OH cost?

If I was buying into this situation, I'd make the deal assuming the engines will have to be gone through.

As a former PW (USA) and Garrett engineer, I dealt with lots of engines sitting idle for considerable periods of time.

Issues to consider:

Fuel system: fuel control seals failing, orifices getting gummed up etc
Lube system: bearings showing corrosion, scoring (if allowed to windmill for extended periods of time)

The exterior of the engine may look unsightly, depending on the environment (moisture) oxidizing cases and controls. It’s a protective layer, but still upsets customers who want a bright shiny engine

As a former PW (USA) and Garrett engineer, I dealt with lots of engines sitting idle for considerable periods of time.

Issues to consider:

Fuel system: fuel control seals failing, orifices getting gummed up etc
Lube system: bearings showing corrosion, scoring (if allowed to windmill for extended periods of time)

The exterior of the engine may look unsightly, depending on the environment (moisture) oxidizing cases and controls. It’s a protective layer, but still upsets customers who want a bright shiny engine

As a former PW (USA) and Garrett engineer, I dealt with lots of engines sitting idle for considerable periods of time.

Issues to consider:

Fuel system: fuel control seals failing, orifices getting gummed up etc
Lube system: bearings showing corrosion, scoring (if allowed to windmill for extended periods of time)

The exterior of the engine may look unsightly, depending on the environment (moisture) oxidizing cases and controls. It’s a protective layer, but still upsets customers who want a bright shiny engine

If the plane has not been flown in 4 years, you must get a healthy discount off current market value or walk away.

As a former PW (USA) and Garrett engineer, I dealt with lots of engines sitting idle for considerable periods of time.

Issues to consider:

Fuel system: fuel control seals failing, orifices getting gummed up etc
Lube system: bearings showing corrosion, scoring (if allowed to windmill for extended periods of time)

The exterior of the engine may look unsightly, depending on the environment (moisture) oxidizing cases and controls. It’s a protective layer, but still upsets customers who want a bright shiny engine

Pratt & Whitney maintenance manual ch 72-00-00 page 306

(1) Engines inactive 0 to 7 days.
…
(2) Engines inactive 8 to 28 days.
…
(3) Engines inactive 29 to 90 days.
…

(4) For period greater than 91 days to less than 1 year:
(a) Do the 0 to 7 day unpreserved engine procedure requirement.
(b) Prior engine start, do a Total Acid Number (TAN) test of oil in engine per related lubricating oil SB13001.
1 If TAN test is above limits, remove the engine and send to an approved facility for light overhaul.
2 If TAN is acceptable, inspect the internal of the AGB and RGB using a borescope for presence of corrosion or internal coating flaking. If corrosion and/or flaking are found, remove the engine and send to an approved facility for light overhaul.
(c) Replace the oil filter.
(d) Drain and flush oil (Ref. Para. 5. E.).
(e) Rotate propeller with your hand and check for binding. If binding, inspect per applicable EMM requirements (Ref. Inspection).
(f) Inspect the engine externals and linkages for condition and evidence of corrosion.
(g) Inspect the compressor for corrosion and cleanliness. Do compressor desalination wash, if dirty or salt laden (Ref. 71-00-00, POWER PLANT - CLEANING).
(h) Inspect fuel filter.
(i) Clean fuel nozzles, perform leak and functional test.
(j) Route FCU to an approved shop for inspection and functional test.
(k) Once the FCU installed (original unit or replacement), disconnect fuel tube at inlet of flow divider and flush fuel system per a wet motoring run.
(l) Run engine at 80% TO power for 10 minutes and do acceleration check.
(m) Remove and inspect internal AGB scavenge pump inlet screen, oil filter, and chip detector(s). If anything abnormal is found refer to applicable EMM.
(n) Check for evidence of fuel and oil leaks at propeller shaft seal, accessory mounting pads, external tubes and hoses.
(o) If further storage is required, preserve depending on the expected period of inactivity per applicable EMM.
(p) After return to service, repeat inspection of oil filter and chip detector(s) after 10 and 50 hours. If anything abnormal is found, refer to applicable EMM otherwise return to standard periodic interval.