R Air Conditioning Panel - Location View
R Figure 003A
R 1EFF : 301-399, 1 21-55-00 Page 9
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**ON A/C ALL
(Ref. Fig. 004)
R If during a flight there is a failure in the two air conditioning packs 10HM
R (11HM), you can push the RAM AIR pushbutton switch 4HZ.
R When you push the RAM AIR pushbutton switch:
R - the altitude of the aircraft must be less than 10000 ft. (3050 m),
R - the cabin differential pressure must be less than 70mbar (1.0 psi).
R The emergency ram-air-inlet actuator 7HZ extends and the emergency ram-air
R inlet moves into the external airflow. Fresh air is pushed into the ram air
R system and flows through ducts to the mixer unit in the cabin air
R distribution and recirculation system.
R The cabin pressure controllers 11HL (12HL) control the outflow valve 10HL to
R an approximately 50% open position.
R
R You can connect a ground air cart to the LP ground connection for
R ventilation of the aircraft. It is not necessary to operate the air
R conditioning packs.
R A. Emergency Ram-Air-Inlet Actuator
R The emergency ram-air-inlet actuator 7HZ is installed on the emergency
R ram-air inlet in the LH belly fairing of the fuselage. It opens and
R closes the emergency ram-air inlet.
R B. Check Valve
R The check valve 4022HM is installed in the duct to the mixer unit. The
R emergency ram-air duct and the LP ground connection duct are connected
R upstream of the check valve. This makes sure that air from the mixer unit
R cannot flow out through the emergency ram-air inlet or the LP ground
R connection.
R 4. Component Description_____________________
R A. Emergency Ram-Air Inlet Actuator
R (Ref. Fig. 002)
R The emergency ram-air inlet actuator 7HZ has:
R - an actuator body assembly (1),
R - a split-field 28 V DC series-motor which has an electromagnetic brake
R (2),
R - a two-step gear-train (3),
R - a jack screw (6),
R - an actuator ram (9),
R - two indication microswitches (7),
R - two travel limit switches (8),
R - a shop-adjustable clutch mechanism (5),
R - a filter circuit board for EMC reasons,
Emergency Ram-Air Inlet - Electrical Schematic
Figure 004
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1 1 May 01/04
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-an electrical connector (4). The electrical motor (2), attached to the actuator body (1), drives the gear-train (3). The gear-train drives the jack screw (6) into/out of the actuator ram (9). This changes rotary motion into linear motion to extend or retract the actuator ram (9). Two microswitches (7) signal the fully extended/retracted position of the actuator ram (9). Two limit switches
(8)
are located between the two microswitches. These remove electrical power from the motor when the actuator ram (9) is at its fully extended/retracted positions. A clutch mechanism (5) disengages the jack screw (6) from the gear-train
(3)
if the emergency ram-air inlet becomes accidentally blocked. An electrical connector (4) connects 28 V DC from the aircraft electrical supply system to power the actuator.
B. Check Valve
R **ON A/C 001-049, 051-099, 101-149, 151-199, 201-299, 401-499,
(Ref. Fig. 001)
**ON A/C 301-399,
(Ref. Fig. 001A)
**ON A/C ALL
(Ref. Fig. 002) The check valve 4022HM is installed in line with the air delivery duct, between the emergency ram-air inlet and the mixer unit. It consists of a tubular housing with two semicircular flaps installed on a hinge bar. The flaps can open in one direction only and a spring holds them in the closed position. Air flow from the emergency ram-air inlet, (or the low-pressure ground connection) will cause the flaps to open. This allows the air to pass through the check valve to the mixer unit. Air flow in the opposite direction will cause the flaps to close onto their seats and stop the airflow.
5. Operation/Control and Indication
________________________________
R **ON A/C 001-049, 051-099, 101-149, 151-199, 201-299, 401-499,
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