Original Flight Hardware: Cabin Temperature Control (Sub-Panel)

This posting covers the second of 4 sub-panels of the large pneumatics panel on the Lockheed L-1011. The panel is titled "CABIN TEMPERATURE CONTROL" and controls the hating and cooling of the vehicle interior (except for the cargo area).

The three air conditioning packs (as seen below) are located in unpressurized compartments on either side of the nose-wheel well. The packs utilize Air Cycle Machines (ACMs) that are operated by compressed bleed air.



Compressed air from the Pack Flow Control valve is partially cooled by the primary heat exchanger. This air is routed to the ACM compressor and, in the case of the #2 and the #3 packs, through a check valve to mix with hot air from the hot air distribution system. The partially cooled air may also pass through another check valve directly to the secondary heat exchanger when the air pressure is greater than ACM compressor discharge pressure.

The cooled air from the ACM turbine and from the Turbine By-Pass Valve are routed through a water separator tot he cold air plenum for distribution to the various zones. Ambient outside air is use for cooling the heat exchangers and is exhaust overboard through exit louvers for each pack. The louvers open and close automatically (during AUTO pack operation), or can be controlled manually (during MANUAL pack operation) to control pack discharge temperature.


Air for the cold air planum can also be supplied externally on the ground. The ground A/C connections feed directly into the #1 and #2 planum system.

The control elements for the PACK TEMPERATURE CONTROL are listed below:

• PACK FLOW CONTROL ... Controls pack flow control valve to schedule a constant mass air flow. Valve is energized closed and pressure opened. The illuminated flowbar indicates flow control valve is open. If OVHT is illuminated, the valve locks closed, flowbar is extinguished and associated hot air valve closes.
• TURB BYP INDICATOR ... Shows relative position of turbine bypass valve (TBV). Pointer moves to COOLER as TBV closes.
• PACK AUTO/MANUAL SWITCH .... If AUTO is illuminated. Ram air exit louvers and turbine bypass valves modulate automatically, to provide temperature control. Setting of zone temperature selectors control packs and zone trim valves to regulate the five zone temperatures. If MNL is illuminated. Arms COOL and WARM switches for manual control of ram air exit louvers and turbine bypass valve. The zone temp selectors control zone trim valves to regulate the five zone temperatures.
• HOT AIR VALVE SWITCH .. this switch opens and closes the control manifold for hot air to be mixed into the pack outflow.