My (1942) Pratt-Whitney R28000-8/-10 operators manual states:
"General reccommendations on the number of flight hours between overhauls,
to serve as a starting point for maintenance procedure, are acceptable only to operators who are begining to operate new equipment with which they have no experience. From then on, the time between overhauls is governed by the individuals operator's experience. The safe procedure with new equipment is to start with a conservative time limit, such as 350 to 400 hours, then gradually approach longer periods (preferably in incraments of 15%) based on the satisfactory condition of the engine at overhaul and the service record of dependability."
My Pratt Whitney R-985 book has the same paragraph without the 350 hours, it reccommends 400 hours. My Ranger 770-C1 book provides no guidance.
My father flew Lockheed Venturas (R-2800) in 1944 and logged almost 500 hours on a combat tour. He told me they only changed engines when performance deteriorated enough to inhibit safe operation or battle damage.
The performance deterioration was mostly due to propellor damage from coral dust and salt air corrosion.
These airplanes flew daily patrols between Tarawa and Roi-Namur, a distance of approximately 600 miles for eight months.
The November 1960 issue of the Naval Aviation News has an article about a VW-3 P2V-5 that has over 1500 hours on its original engines.
...........
