AIRCRAFT SYSTEMS POWER PLANT
SA227‐ SERIES/FCOM/VTM
6.71.1
POWER PLANT The METRO III is equipped with two Garrett Engine Turbine Company TPE331‐11U‐611G, or ‐612G single‐shaft turboprop engines rated at 1,000 shaft horsepower maximum continuous or dry takeoff power, and 1,100 shaft horsepower for a wet takeoff. At 100% engine RPM, the propeller rotates at 1,591 RPM. The major components of the engine power section consist of a two stage centrifugal compressor, an annular reverse‐flow combustion chamber, and a three stage axial flow turbine. During operation, ram air enters the upper air scoop and is directed into the center of the first stage compressor where the air is compressed and directed to the second stage compressor. After second stage compression, the air is directed into the plenum surrounding the combustion chamber and then into the combustion chamber. Fuel is sprayed into the combustion chamber, mixed with the compressed air, and ignited. As the mixture ignites, it expands with a great increase in temperature and pressure. The air exits the combustion chamber and is directed to the first axial flow turbine. As the air flows through the axial flow turbine blades, the turbine wheel is rotated and the air velocity decreases. This process is repeated over the remaining two turbine wheels extracting most of the heat and energy from the air and converting it to rotating mechanical energy. This energy is used to drive the centrifugal compressors, the reduction gears, the propeller, and various engine components. Labyrinth seals situated between the various turbine and compressor wheels prevent back flow of hot gasses from one stage to another.
Figure 6.71‐1
Revision: Original Aug 1,2013
GO/FCOM/SA227‐SERIES/VTM