Torque Indicator
Engine torque (TRQ) is shown by the torque indicator found on each EICAS
page. The torque indicator uses a circular scale with a moving pointer and a
digital value indicating the torque being produced by the engine. The pointer
moves through a range of 0 to 2100 foot pounds.
The PT6A-34 engine is limited to 750 SHP for takeoff and emergencies, and
700 SHP for climb and cruise. Shaft horsepower is determined using the
following equation:
SHP = Torque X Propeller RPM
5252
For Example:
750 SHP = 1790 (TRQ) X 2200 (RPM)
5252
The red line on the torque indicator is a dynamic marking depending upon
propeller RPM and represents 751 SHP. If engine torque reaches the red line
limit for longer than 5 seconds or greater than 2100 foot pounds at any time,
the pointer, digital value, and label (TRQ) turn red to show engine torque is
more than the established limits. The digital value and label (TRQ) will ash.
The torque indicator is displayed in the same conguration and location on
the default, SYSTEM and ENGINE pages.
The amber arc on the torque indicator is also a dynamic marking depending
upon propeller RPM and represents a shaft horsepower range from 701 SHP
to the upper limit of 750 SHP. If the engine torque and propeller RPM are
generating between 700 SHP and 750 SHP, the torque indicator title, pointer,
and digits will be amber.
The top of the green arc on the torque indicator is also a dynamic marking
depending upon propeller RPM and represents 700 SHP.
The indicator operates in conjunction with a transmitter located on the top
of the reduction gearbox front case. The transmitter senses the difference
between the engine torque pressure and the pressure in the engine case.
The transmitter relays this data to the GEA 71 Engine/Airframe Interface Unit
which processes and outputs torque data to the EICAS. A red X through the
torque indicator shows the indicating system is inoperative.
Figure 7-63 – Torque Indicator
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