The Pratt & Whitney R-1340 Wasp was a 9 cylinder, single-row, air-cooled radial engine with horsepower ranging from 410 hp to 600 hp, depending on the model and configuration. It was used in a range of aircraft that included the North American AT-6, Boeing P-26, and Boeing 247. Jimmy Doolittle used the Wasp to set records in his Gee Bee Racer and Amelia Earhart made history using the Wasp in her Electra L-10.
Please allow me to offer some information in regard to Pratt & Whitney R-1340 & R-985 engine Time Before Overhaul intervals (TBO’s) for engines utilized on current agricultural aircraft. A letter from Pratt & Whitney (P&W) faxed to the Federal Aviation Administration (F.A.A.) dated February 13, 1990 is useful in understanding the organization’s corporate position on the radial engine.
“Pratt & Whitney have no company or F.A.A approved methods for providing any engineering substantiation or manual/publication revision relating to new methods or procedures which are being accomplished by operators and overhaul shops on Pratt & Whitney reciprocating engines.”
This letter establishes a, “hands off” attitude on P&W’s part concerning the Reciprocating Radial engines. Oil consumption is a major issue and is addressed in a cautionary statement constituting part of the P&W TBO considerations given in the R-1340 & R-985 overhaul manual (part number 123440).
“Oil consumption is usually one of the best indications as to whether or not the engine requires overhaul, provided the engine is performing normally and there 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 case for overhaul.”
The engine’s primary accessories (Carburetor, Fuel pump, Magnetos, Starter, Propeller Governor, and Generator) are designed to run to engine TBO. It is our recommendation that they be overhauled at the same TSO as the engine. Ref: AC65-12A Chapter 10 Page 411 Par. Major Overhaul Our basic TBO recommendations are 1000 to 1400 hours operating time since overhaul. In order to determine this “recommended” Time Before Overhaul we have taken into consideration all forms of Agricultural utilization of the R-1340 & R-985 engine and have averaged the operating time between overhauls of engines submitted to us for overhaul over the last 25 years.
It must be noted that there is an Airworthiness Directive 68-09-01 issued to the R-985 engine. It is concerning Crankshaft flyweights and flyweight liner replacement. This AD mandates that it be accomplished at 1200 or 1600 hrs depending on propeller installation. In order to accomplish this, the engine must be disassembled to the point it is more economically feasible to overhaul than to limit to repair and replacement only. This Time Before Overhaul recommendation is made with the assumption that all manufacturers’ recommended/required periodic inspections are complied with in a timely manner throughout the life of the engine. This recommendation is not to certify or guarantee that an operator will achieve a specific number of hours operation time before an overhaul is necessary. This TBO recommendation should in no way be considered a maximum TBO limit as it is possible to safely operate an R-1340 & R-985 past 1200 or 1400 hours TSO. It is merely a RECOMMENDATION that, hopefully, will better enable an operator to develop a safe, economic engine overhaul schedule.
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Covington Aircraft firmly believes in the history of aviation (you can’t get to where your going without knowing where you have been). So, this week, we talk about the modern marvel that is 100 years old, R-1340 Engine, Pratt & Whitney’s first engine.
Mr. Willgoos and Mr. Mead innovate a Modern Marvel
In 1925, President Calvin Coolidge had his inaugural address broadcast over the radio, a first in the United States. Richard Drew invented scotch tape, making it easier for the world to wrap Christmas presents, in 1925 as well. However, one of the most important firsts to happen in 1925 was the conception and development of the R-1340 engine, a single-row, nine-cylinder air-cooled radial design. Brought to life by Andy Willgoos and George J. Mead, the R-1340, which became the cornerstone of Pratt & Whitney Aircraft, was discovered in the small backyard garage owned by Mr. Willgoos.
The difference in the R-1340 engine from other engines was the supercharger or blower section which has remained unchanged since its humble beginnings in 1925. The blower section is attached to the rear power case and receives the fuel/air mixture from the impeller assembly. This mixture is delivered to the cylinders via the intake pipes and and then to the crankshaft using a spring loaded gear. This protects the blower gearing from sudden acceleration or deceleration.
Introduction of Different Blower
The original blower developed by Willgoos and Mead came to be known as a ball bearing blower as it was supported by three ball bearings. Pratt & Whitney later introduced a plain type blower which does not use ball bearings. Many believe that the reason for the development of the plain type blower was due to weakness of the ball bearing blowers, but this is not the case, as both types of blowers have good and bad qualities.
Classified as a top-secret design when it was developed in the 1920’s, the R-1340 engine is still as much of a modern marvel today as it was almost 100 years ago, making it one of the aviation industry’s modern marvels.
Covington Aircraft has been overhauling, selling, and maintaining radial engines and turbine engines since 1979. If you need a radial engine part, perhaps for your R-1340, make sure you visit our website and give us a call! Happy Flying!
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