Definition
A family of small free-turbine turboprop engines manufactured by Pratt & Whitney Canada, widely used in general aviation, regional, agricultural, and military trainer aircraft. The PT-6 uses a split-shaft design in which the gas generator section drives a separate, mechanically independent power turbine that turns the propeller through a reduction gearbox.
Plain English
A specific brand and model of small turboprop engine, made by Pratt & Whitney Canada, that uses two separate spinning sections — one to make hot gas, and a second one that the hot gas spins to turn the propeller.
Context Anchor
Seen in turboprop training, aircraft systems descriptions, and discussions of split-shaft/free turbine engine operation.
Derivation
Pratt & Whitney is the engine manufacturer; the Canadian division (Pratt & Whitney Canada) developed this engine family beginning in the 1960s. 'PT' stands for 'Pratt Turbine,' and the '6' indicates it is the sixth engine project in their numbering sequence. Knowing this helps pilots recognize 'PT-6' as a model designation, not a technical specification.
Why Pilots Care
Many training and personal turboprops use this engine, so pilots must know its free-turbine starting sequence and propeller response to avoid damage or loss of control.
Intuition Check
Do not read PT-6 as a general engine category. In this context, it names a specific Pratt & Whitney turboprop engine family used as an example of the free turbine design.
Example Sentence 1
The King Air 200 is powered by two Pratt & Whitney PT-6 engines.
Example Sentence 2
During an engine failure drill the instructor demonstrated that the PT-6 free turbine lets the propeller continue turning even after the gas generator is shut down.