Hawker 800 XP, Pilot Training Manual

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Revision 1 7-12
FOR TRAINING PURPOSES ONLY
HAWKER 800 XP PILOT TRAINING MANUAL
FlightSafety
international
An operating fuel computer electrically con-
trols fuel flow scheduling by setting the FCU
metering section pressure drop according to
throttle and engine inputs.
The FCU has two shutoff valves in series. The
throttle actuates one valve and the electronic
engine computer actuates the other valve. If
the computer sense an ultimate overspeed con-
dition, the computer closes the shutoff valve,
fuel flow stops, and the engine shuts down.
Inlet Pressure and Temperature
Sensor
An inlet pressure and temperature sensor is lo-
cated on the cowling forward of the fan inlet.
The sensor contains electrical elements for
sensing inlet air temperature (Tt
2
) and a pres-
sure tap for sensing inlet air pressure (Pt
2
).
Both inlet parameters are required by the fuel
computer. An electrical anti-icing element is
contained in the sensor.
Digital Electronic Engine
Control (Fuel Computer)
The -62 Digital Electronic Engine Control
(DEEC) for the TFE 731-5BR engine is a closed
loop control, that uses N
1
rather than N
2
as the
control parameter. The -62 DEEC minimizes N
1
overshoots following engine acceleration and
provides precise, repeatable N
1
control for all
engine operating regimes. This control does
not require engine trimming.
Two digital electronic engine controls (DEECs)
are located in the rear equipment bay. Each
DEEC controls the engine acceleration and de-
celeration. Separate ENG CMPTR switches on
the overhead panel allow automatic (AUTO) or
overspeed protection (OVSPD PROT) mode
selection (Figure 7-9). Both DEECs receive 28
VDC from the PE busbar in the automatic mode
(see Figure 7-10).
During acceleration and deceleration, the
D E E C s p r ov i d e g ove r n i n g , l i m i t i n g a n d
scheduling response to the throttle and en-
gine inputs. Inputs to each computer are:
• Engine Inlet Pressure (Pt
2
)
• Engine Inlet Temperature (Tt
2
)
• Interstage Turbine Temperature (ITT)
• N
2
Speed
• N
1
Speed
• Power Lever Angle (PLA).
Each DEEC provides appropriate output cur-
rent to the torque motor of the associated FCU
based on the various inputs.
Circuits within the DEEC monitor N
1
and N
2
continuously to provide overspeed protection.
The computer commands the engine to shut
down if the engine speed exceeds 107% N
1
or
109 % N
2
. If an overspeed occurs, the primary
overspeed circuit arms an electronic switch;
the switch energizes the overspeed solenoid
that cuts fuel to the engine. This function is
called the ultimate “overspeed protection.”
ENG CMPTR
1 AUTO 2
OVSPD PROT
O
F
F
Figure 7-9. Engine Computer Switches