The PT6A – The Legend Tells Its Story

THE PT6 ENGINE MILESTONES

It’s the remarkable story of a remarkable engine. With more than 51,000 engines delivered to power some 130 different applications, the PT6 engine can tell quite a story of creativity and transformation. While we had a lot to choose from, we’ve put together a list of milestones for the engine as we mark its golden anniversary.

1957 – P&WC assembled a team of 12 talented young engineers after studies showed a market opportunity for 500 shp (shaft horsepower) class turboprop engines in the aircraft market then powered by piston engines. P&WC saw an opportunity to channel some of the profits from its piston engine spare parts business towards the development of gas turbine engines smaller than those made by its U.S. parent.

Twelve key men on the PT6 engine design team: Gordon Hardy, Jim Rankin, Fernand Desrochers, Fred Glasspoole, Ken Elsworth, Allan Newland, Pete Peterson, Hugh Langshur, Jean-Pierre Beauregard, Elvie Smith, Dick Guthrie and Thor Stephenson.

Twelve key men on the PT6 engine design team: Gordon Hardy, Jim Rankin, Fernand Desrochers, Fred Glasspoole, Ken Elsworth, Allan Newland, Pete Peterson, Hugh Langshur, Jean-Pierre Beauregard, Elvie Smith, Dick Guthrie and Thor Stephenson. © Library and Archives Canada. Reproduced with the permission of Library and Archives Canada. Source: Library and Archives Canada/Credit: Bruce Moss/Weekend Magazine collection/PA-167966.

1963 – It’s what our celebration is all about. In December 1963, P&WC shipped the first PT6 production engine, the PT6A-6, to Beech Aircraft Company for its Beech 87, which later became the King Air. The PT6A-6 was a highly innovative gas turbine that represented a significant advance in technology from the traditional piston-driven engines used to power small aircraft.  Gas turbines have a higher power to weight ratio than piston engines.

The first PT6 production engine.

The first PT6 production engine. P&WC Archives (Records and Information Management).

1967 – Piper’s PA-31 Navajo took its first flight powered by PT6A-20s. Piper had enjoyed enormous success building light aircraft since the 1930s, but it took P&WC years of effort to get Piper to adopt turbine engines and move away from their traditional reliance on piston-driven engines.

1968 – P&WC’s ST6L73 engine (a derivative of the PT6A without the gearbox second stage) entered into service as an auxiliary power unit (APU) for the Lockheed L1011 airliner.

1968 – Bell Helicopter placed its initial order for P&WC’s first turboshaft, the PT6T Twin-Pac® engine

1970 – P&WC’s PT6T Twin Pac® entered into service. It is two engines coupled in a single package to power medium-sized, twin-engine helicopters.

1970 – The United States Military ordered 294 Bell 212s under the designation UH-1N equipped with PT6T Twin-Pac® turboshaft engines. Delivery also began in 1970.

1973 – The second-stage power turbine was introduced on the PT6A-41. This was a step change in engine power and efficiency.

1979 – An Air Tractor agricultural aircraft is powered by a PT6A engine and flies to the National Agricultural Aviation Association convention in Las Vegas – the first time such a combination was displayed in public.

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The P-750 XSTOL and the P&W PT6-34 Engine

Pacific Aerospace describes its flagship product, the P-750 XSTOL, as the world’s first Extremely Short Take-Off and Landing (XSTOL) aircraft and as the best in the world for the missions it was designed to accomplish. Bold claims from the New Zealand based company, to be sure, but not without foundation, as it can boast some pretty impressive performance. Much of that performance can be credited to the Pratt & Whitney PT6A-34 engine that powers the plane, but more on that in a moment.

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The T-6 Texan: Then and Now

Since it was first produced in 1937, the T-6 Texan and its offshoots have filled many roles for many different institutions in dozens of countries. It proved to be one of the more enduring, durable, and useful aircraft ever designed, and that’s further evidenced by the evolution in the 1990’s of the Beechcraft T-6 Texan II, which is a modern version of the original WWII trainer.

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Radial Engine Time Between Overhaul: What’s My TBO for the R-985 & R-1340?

 

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.

AT-302
Ayres AT-301 Air Tractors VH-ODB and VH-ODM at Tintinara SA in May 1989
Designed by Leland P. Snow, the AT-302 designation indicates 320 gallon hopper and P&W R-1340 radial engine
From http://www.goodall.com.au/photographs/aerial-agriculture-80-1/80saerialag-1.html

“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.

Weatherly 620A VH-WEA
Manufactuered in 1989, Weatherly 620A VH-WEA is powered by a 9-cylinder, Pratt & Whitney R-985 radial engine however the aircraft itself has a relatively low spraying capacity of 1200 litres. From http://airqueensland.blogspot.com/2015/01/r-mach-aviation_7.html

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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Daher’s Kodiak 100 delivery to Héli-Béarn marks the first French customer for this turboprop-powered utility aircraft

Tarbes, France, January 21, 2021 – The delivery of a Kodiak 100 to Héli-Béarn makes this air services company the first French customer for the utility aircraft member of Daher’s single-engine turboprop-powered airplane product line.

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Jet Speed with Turboprop Efficiency: The Epic E1000

The Epic E1000 is drawing attention for its sleek carbon-fiber design and intelligent engineering, producing the fastest turboprop available. Emerging from roughly a decade of perfecting its kit-plane predecessor (The Epic LT Dynasty), the E1000 promises to build on the devoted following growing around Epic Aircraft with exhilarating speed, fuel efficiency, and plenty of space. 

epic e 1000
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Tracking Starts And Flights: Understanding Abbreviated Cycles and Full Cycles for PT6 Engine Maintenance

As most of you know, there are life-limited components in a PT6. These components include the CT and PT Disks and the Compressor Disks. After a certain number of cycles they must be replaced.

starts and flights pt6a compressor disk

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