If You Can’t Beat Them, Join Them

Reverse flow operation (starts at 45s)

See also this diagram

The GE Engine

GE will be attempting to challenge Pratt & Whitney in the turboprop market, where the PT6 turboprop completely dominates the market.

Of interest to me is that GE will be copying the basic operating principals of the PT6,(paid subscription required) P&W’s reverse flow operation.

The inlet is at the back of the engine, and air flows forward. This allows the compressor and the compressor turbine to be completely separate from the power turbine and prop.

While the air flow is rather more circuitous than that of a straight through engine, it has a number of significant advantages:

  • No need for concentric shafts while still maintaining a two spool compressor and turbine.
  • A smaller and lighter starter motor.
  • More easily adopted to different power levels.
  • Greater simplicity and reliability.

The PT6 has used this formula to completely dominate the market, and it looks like GE will be aping their approach, with a lot of additive manufacturing throw into the mix:


Then there’s the ATP, GE’s Advanced Turboprop engine (see photo, above). This is a very big deal in terms of technology and targeting.

For those cloistered monks among you, some background: Pratt & Whitney Canada’s PT6 family has reigned supreme among turboprops since, well, forever. And for good reason. The type ranges in power from 500-2,000 shp and has demonstrated rock-solid reliability through decades of operation. Its bulletproof reputation is the reason almost all single-turboprop-powered aircraft—from the Piper’s owner-flown M600 to Beechcraft’s PT-6 Texan II military trainer to the do-it-all Pilatus PC-12—are fitted with a PT-6. More than 51,000 PT6s have been produced since the engine’s introduction in the 1960s. It has been expanded to include 69 versions that power some 100 different aircraft models, including all production King Airs.

GE hopes the ATP will break Pratt’s near monopoly. Developed at the company’s “turboprop center of excellence” in Prague with a $400 million investment, this, the world’s most “printed” engine (additive manufacturing has replaced 855 parts with a mere dozen 3D-printed components)features a single-lever integrated engine and propeller control, 16:1 pressure ratio, reverse-flow combustor and output of 850-1,650 shp. The design promises 20% better fuel burn, 10% more power and longer maintenance intervals than you know what.

This is, in its own way, a tribute to the genius of the design team that first devised the PT6.

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