PILOT’S OPERATING HANDBOOK
SECTION 7
DESCRIPTION
Edition 0 -- October 31, 2013
Rev. 1
Page 7.6.1
7.6 - POWERPLANT
TURBOPROP ENGINE OPERATION
(Figure 7.6.1)
The PRATT & WHITNEY CANADA turboprop engine (PT6A-66D model) is a free turbine engine rated at 850 SHP
and developing a thermodynamic power of 1825 ESHP.
Intake air enters engine through an annular casing and is then ducted toward compressor. The latter consists of
four axial stages and one single centrifugal stage assembly to form a whole assembly. Compressed air and fuel are
mixed and sprayed into combustion chamber by fuel nozzles. The mixture is first ignited by two spark igniter plugs,
then combustion continues as a result of air-fuel mixture flow. Gases resulting from combustion expand through a
series of turbines. The first one (gas generator turbine) drives compressor assembly and accessories, the two
other ones (power turbines), independant from the first one, drive propeller shaft through a reduction gear box. Hot
gases are evacuated through two exhaust stubs located laterally on both sides forward of engine cowling.
All engine driven accessories, except power turbine tachometer, propeller governor and overspeed governor are
installed on accessory gearbox located rearward of engine.
