Hawker Beechcraft Hawker 800XP, Руководство по эксплуатации для пилотов

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Page 10-15
Pilot’s Operating Manual
Original Issue: Feb, 2002
Sub-section 10
ENVIRONMENTAL
Hawker 800XP Pro Line 21
Section III - SYSTEMS DESCRIPTION
Pneumatic Relay
Each pneumatic relay senses cabin pressure changes as referenced by the pressure controller. These
pressure changes cause the associated outflow valve to operate via an absolute pressure regulator.
The pneumatic relays are connected to a single air jet pump. This pump, operated by engine bleed air,
ensures that the desired differential between the outflow valve reference pressure and cabin pressure
is maintained.
Absolute Pressure Regulators
The absolute pressure regulators are safety devices, set to maintain cabin altitude at 13,500
±
1500 feet
in the event of system malfunction. In this condition, the regulators operate to prevent further reduction
of the reference pressures. This causes the outflow valves to shut in an attempt to restore cabin
pressure.
MANUAL CONTROL
Manual control of pressurization is achieved by operation of a shut-off valve and a needle valve. The
shut-off valve, labelled PRESSURIZATION CONTROL has two positions, NORMAL and GROUND
TEST. This valve is connected into the ambient bleed to the pressure controller. With NORMAL
selected, the bleed is open and automatic pressurization control is available.
Selecting GROUND TEST closes the controller ambient bleed; this causes the outflow valves to shut.
Subsequently, cabin pressure can be controlled by the needle valve labelled MANUAL CABIN
ALTITUDE CONTROL. This valve connects one of the outflow valves to ambient via a venturi in the
forward luggage bay.
Rotating the MANUAL CABIN ALTITUDE CONTROL valve between INCREASE and DECREASE,
adjusts the pressure differential required to operate the outflow valve and allows a desired cabin altitude
and rate of change to be attained.
GROUND AIR CONDITIONING
With main engine(s) running and MAIN AIR VALVE(S) OPEN or with APU (if installed) running and APU
AIR OPEN, air conditioning is available on the ground by means of a fan-operated venturi. The fan is
electrically-operated and controlled by a PRESSN OVRD - AUTO switch via the landing gear lever lock
circuit.
With the airplane on the ground and AUTO set, the fan operates so the venturi reduces the reference
pressures and causes the outflow valves to open. Air circulates through the cabin with normal
temperature control available. On takeoff, the venturi fan switches off automatically; pressurization
control then operates from the normal pressure differentials. The OVRD position is used to switch off
the venturi fan in the event of auto mode failure, or to achieve cabin pressurization on the ground for
maintenance purposes.
Each outflow valve incorporates an inward relief facility. At a negative pressure differential of 0.5 psi the
outflow valves open to allow reverse flow, at ambient, to enter the cabin. In this condition, the cabin
altitude changes at airplane altitude rate of change irrespective of control settings. Also incorporated in
each outflow valve is a pressure relief valve.
The relief valve cracks open when cabin differential pressure exceeds 8.6 psi, to exhaust outflow valve
reference pressure. This causes the outflow valve to open and restrict the maximum cabin differential
pressure to 8.8 psi In this condition, normal pressurization control is inoperative.