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Flight Management System (FMS) for the Agusta AW139/AB139 Helicopter
Additional Explanation of Fuel Quantity and Fuel Flow
The FMS fuel weight is equal to the gauge value when the aircraft
is on the ground. This is the case when either no engines or one
engine is running. After completion of engine start for both
engines, the FMS fuel weight is set equal to the gauge value.
This value is then decremented by the sensed fuel flow.
This method permits for fuel leak detection. The FMS computes
fuel weight based on the sensed fuel flow to the engines. The
gauges give the sensed fuel weight based on engine usage and
leakage (when a leak exists). The scratchpad message
COMPARE FUEL QUANTITY is displayed when the FMS fuel
weight differs from the gauge value by more than 2.5% of the
BOW. This message is inhibited when the fuel quantity has been
manually entered on the PERFORMANCE INIT 3/3 page.
Entering a manual fuel flow can create significant differences
between the FMS fuel quantity and the actual fuel quantity. No
entry of fuel is recommended to be made unless the sensed fuel
flow is not available.
NOTE:
— 2L and 2R -- The current ground speed and airspeed are
displayed on this line. No entries are permitted.
— 3L and 3R -- The ground and air specific ranges are displayed
on this line. The specific ranges are based on the ground speed,
airspeed, and fuel flow shown on the page. No entries are
permitted.
A28- - 1146- - 181
REV 3 Mar 2009
Honeywell International Inc. Do not copy without express permission of Honeywell.
Entry of a fuel flow at 1R is not the same as entry on
PERF INIT 2/3 for pilot entered SPD/FF.
Performance
5-37
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