Page 18 - Volume 15 Number 4

MAINTENANCE TIP
All PT6 engines have at least one compressor bleed valve installed just forward of the engine inlet screen, some models have two. These valves (called Bleed
16 • KING AIR MAGAZINE
Off Valves, or BOVs by many mechanics) serve to vent excess compressor air not needed in the combustion chamber and to prevent compressor stalls.
Low Torque: Hot Section or Bleed Valves?
When you reach max power during takeoff, you’ve got your eye on the ITT and torque. If ITT is high but torque is lagging, you might worry that a hot section problem has developed in the engine. Before leaping to that conclusion, however, consider the compressor bleed valve(s).
by Dean Benedict
I don’t want to insult anyone’s intelligence here, but I want to make sure we are all on the same page. If you live and breathe all things PT6, bear with me for a second. The bleed valves discussed herein have nothing to do with bleed air taken off the engine to run the pressurization and pneumatic air systems.
The PT6A-20, -21, -28 and -135A engines have just one bleed valve located at the 6 o’clock position forward of the engine inlet screen.
The high pressure bleed valve in the 3 o’clock position on a PT6A-42 engine.
APRIL 2021