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.
This work-horse of an aircraft has earned a reputation as one of the most capable bush planes ever built, and it was easy to see why as we flew out over the ocean and through island valleys in the remote stretches of the Kodiak archipelago.
When it comes to airplane engines, radial engines are the true classic
Ever since Louis Bleriot crossed the English Channel in 1909, the radial engine has been an integral part of modern aviation. Their simple yet powerful design has been improved upon throughout the 1900’s, but the basic principles behind the airplane engine have remained constant. Pratt and Whitney R-985 and R-1340 radial engines were designed starting in the 1920’s, and have withstood the test of time. Many of these radial engines are still in use today, thanks to companies like ours who are able to perform the overhaul and maintenance required for these masterpieces.
The R-1340 radial engine was Pratt and Whitney’s first foray into airplane engines, and approximately 35,000 engines were produced. The next engine to be mass-produced was the R-985. This engine was manufactured from the 1930’s to the 1950’s, and over 39,000 of them were made
Radial engines played a major part in the First World War, outlasting and outperforming rotary engines over time. The R-985 and R-1340 engines became the standard aircraft engine for World War II, powering airplanes used in basic training as well as military versions of civil aircraft. After the war, R-985 engines were used in various smaller civil and military airplanes, including utility aircraft, small transports and agricultural aircraft. Their simple design and reliability made them popular among airplane enthusiasts around the country.
Today, you’ll find most R-985 and R-1340 engines in bush planes and agricultural aircraft, as well as on WarBirds. Parts for these engines are still available on the market, but repair and overhaul of R-985 and R-1340 radial engines requires a skilled technician. As a certified FAA Repair Station, our Radial Engine Division is the largest R-985 and R-1340 overhaul facility in the world, and we pride ourselves on being true artisans when it comes to overhaul and maintenance of radial engines.
So, if you’ve got a plane with one of these engineering marvels, be sure to entrust its maintenance to a facility that specializes in the radial engine. They can keep your engine running for years to come.
This blog is republished with the permission of Jim Savage. His website, VintageSpartanAircraft.com which features his 1939 Spartan Executive, is a must visit.
What do you do to make your Spartan so shiny? That’s a question I am
often asked and the answer may be easier than you expect. Obviously, it
takes quite a bit of polishing, using quality polishing supplies and
good polishing techniques. Most experienced metal polishers with bare
metal airplanes already know that. The missing piece has to do with how
light behaves when it reaches the airplane. Specifically, it is either
reflected or it is absorbed. The more light that is reflected, the
shinier the airplane appears to be. The trick is to eliminate anything
that absorbs the light. In the case of Spartan NC17634, it has minimal
paint trim, so there is more surface available to reflect light. Of
course, that holds true for many bare metal airplanes. The other source
of light absorption is the tiny black rings around each of the rivet
heads. Although often unnoticed unless you are specifically looking for
them, almost every bare metal has these light absorbing rings,
including ones that have been judged as Grand Champions. They originate
during the normal polishing process and over time and many polishings,
they slowly accumulate. With the passage of time, these rings become
extraordinarily difficult to eliminate.
While a tiny black ring around a single rivet doesn’t seem like much,
consider what the cumulative amount is if you have 9000+ polished
rivets, as is the case with NC17634. To the best of my knowledge, there
is no magic potion that easily removes the black residue. It is simply a
matter of finding a process that works best for you and then
proceeding, one rivet at a time. While the removal of all traces of
black from every rivet of an entire airplane is a daunting task, the
results are clearly noticeable.
Here are some close-up pictures rivets on a 1939 Spartan Executive. The first nine pictures show examples of what domed rivets with black rings look like on a highly polished airplane.
The next nine pictures show similar views of the same Spartan, after removal of the black rings.
For those of you who are really, really curious about how long it took to remove all traces of black from the 9000 rivets on the Spartan, it is probably far more than you can imagine and likely far more than you will believe. It took approximately 800 hours of effort but as the following picture shows, the final results can be stunning.
Though the 1928 Ford Tri-Motor aircraft, also called the “Tin Goose,” is no time machine, the pilot and passengers agreed the 30-minute ride on the first commercial aircraft and mass-produced airliner gets close enough.
The Pratt & Whitney R-985 Wasp Junior is a series of nine-cylinder, air-cooled, radialaircraft engines built by the Pratt & Whitney Aircraft Company from the 1930s to the 1950s. These engines have a displacement of 985 in; initial versions produced 300 hp (220 kW), while the most widely used versions produce 450 hp (340 kW).