User manual

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To engage the start latches, the pilot needs to pull the throttles into
the reverse range right after shutdown of the engines but before Ng
RPM drops below approximately 50%. This will keep the propeller
blades in the beta range enabling the start latches to “snap in” and
lock the blades. To disengage the start latches, the pilot only need to
move the throttle into reverse range after engine startup has occurred
and Ng RPM is above approximately 60%. Throttling up with start
latches engaged will be noticed because of the lack of forward thrust
and little torque readout on the gauges.
In the case where the pilot fails to move the throttles into reverse
range, the propeller will feather, just like on the free turbine types of
engine. In such cases the propellers will need to be un-feathered. This
is done via the Airstart switches. The airstart switches have 3 positions
CRANK, AUTO, ON. AUTO is the normal position and will automati-
cally control fuel and ignition in accordance to the engine RPM sensing
switches. CRANK will turn on a pump called the un-feather pump. This
pump supplies oil pressure to the propeller governor forcing the
propeller blades towards full fine and beta range - no fuel or ignition is
introduced. Crank is somewhat misleading - it won´t crank the engine
by the Starter, but merely points to the fact that in air, the un-feather-
ing of the propeller will cause these to start wind-milling. ON means
that the un-feather pump as well as fuel and ignition is introduced for
an air-start. After un-feathering / air-start the Airstart switch must be
returned to AUTO. Note the Bronco has two additional ignition
switches for continuous ignition.
The description might sound complex, but is actually very straight
forward. For starting the engines on the Bronco follow this procedure:
• Power levers: GROUND IDLE
• Condition levers: SHUT OFF (NOT SHUT OFF & FEATHER)
• Primary DC bus: POWERED (BATT DISC & BATT MAIN
SWITCHES ON OR GRND PWR ON)