Pratt & Whitney R1340 & R 985 time before overhaul help needed

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AskBob's picture
Pratt & Whitney R1340 & R 985 time before overhaul help needed

On the engines Pratt & Whitney R1340 & R 985, he is convinced he has read somewhere that the time before overhaul is 1000 hours and that there is a 200 hour extension possible but he can’t seem to find it.

He is wondering maybe if this is a service bulletin (along the lines of SI 1009 from Lycoming) that would indicate those but he is not sure.
For reference, those 2 engines are mounted on: S-2R AYRES THRUSH & G164B AG CAT GRUMMAN.
Received by email from Herve'

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krugerk's picture

The basic TBO of the R-985 is 1200 hours with a possible approved extension to a maximum of 1600 hours which is generally approved through the local FSDO on a case by case basis based upon proper care and feeding of the engine.

The following statement is one set forth a the introduction in the 1340/985 overhauls manual, - it reads:

"Time Between Overhauls" Where engines are consistently cruised at relatively low power, such as in operations involving long range aircraft, and where conservative cruising outputs can be consistently maintained, periods of 1000 to 1600 hours (helicopter engines 500 to 800 house) (agricultural aircraft 600 to 1000 hours) between overhauls are feasible, but such extended periods between overhauls should be determined by experience with the engines of a particular model in the given type of operation, and their condition at overhauls. It is suggested that overhaul period increases be made in increments of 100 flight hours. Oil consumption is usually one of the best indications as to whether or not the engine requires overhaul, provided the engine is no indication of possible trouble or irregularities requiring more than normal line maintenance attention. A sudden increase of oil consumption, or a gradual increase of oil consumption to double that which has previously been average, is usually as for overhaul."

One thing to consider is the type of flying the aircraft are involved in. It's pretty safe to say that an aircraft flying low strafing runs followed by high-g, high power pull ups are going to feel the effects much more than an engine flown under more normal conditions. That being said, it may be more cost effective to limit the TBO on these engines to 1000-1100 hours if they are being used for ag flying. TBO can be extended but my guess is that the cost benefits will be lost at the 1600 hour TBO when more parts have worn out.

Incidentally, a quick check of the website has some interesting AD's concerning the inspection of these engines that are worth taking a look at.

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