Simulator Integration Planning: ATA 21 - Air Conditioning and Pressurization (Label Assignments - Part 3)

L-1011 Air Cycle Machine Temperature Ranges

In order to program the AC behavior of the L-1011 correctly we will have to go a bit deep on the various parameters in the system. First, lets take a look at the normal temperature ranges we should observe on the ECS Monitor in cruise flight. The numbers in the table below correspond to the numbers in the image above:

• [1] Pack Inlet Bleed Air Temperature ... 160º-200ºC in cruise
• [2] Compressor Discharge Temperature ... 60º-80ºC in cruise (depending on Turbine bypass valve setting)
• [3] Turbine Inlet Temperature ... 15º-20ºC in cruise (will vary with RAM air setting)
• [4] ACM Discharge Temperature ... 15º-20ºC in cruise. The lowest possible ACM discharge temperature is 2ºC
• [5] Hot Air Manifold Output Temperature .... 110ºC

The normal Pack Flow outflow for Pack #2 and #3 is between 2000 and 2500 CFM (#1 has 300-400 less). The spring loaded valves for the Pack Flow Control and the Hot Air Manifold will not open if the duct pressure is below 15 PSI.

Warning Indicators

• Pack Flow Control Switch OVHT light illuminates when the Compressor Discharge Temperature [2] exceeds 200ºC or when the ACM Discharge [4] temperature exceeds 96ºC.
• DUCT OVHT ... illuminates when the Hot Air Manifold Duct temperature has reached 145ºC. This causes both Hot Air Isolation Valves to close until the temperature falls below 120ºC.
• Hot Air Isolation Switch OVHT ... illuminates when the respective valve has reached 135ºC

Valve Position Values

There are a number of default valve position values that the system simulator needs to take into account.

Turbine Bypass Indicator - The turbine bypass value is positioned full warm until the RAM AIR louvers have reached the full cool position as indicated on the RAM AIR indicator (9 o'clock  on the ground or 1 o'clock position in flight). Once this status has been reached, the turbine bypass valve will now be positioned to hold the required temperature. With the pack turned off, the turbine bypass valve will be set to the 11 o'clock position by default.

RAM Air Indicator - With the Pack turned off the the louvers are automatically set to the 9 o'clock position on the ground and the 1 o'clock position in flight.

Turbine and RAM Positions on Ground.

Turbine and RAM Positions in Flight.

In part 4 of this series we are going to start developing a model that will allow us to compute the approximate temperatures and cabin zone temperatures base on the relationships established in normal cruise flight. Again, the idea is the create a systems simulation of the L-1011 air conditioning and pressurization system that is as real-world as feasible for this project. 

Original Flight Hardware: Humidity Control

To minimize Environmental Control Systems (ECS) condensation in the cabin of the Lockheed L-1011, the ACM discharge temperature is maintained at 38F (2C) regardless of any other demand inputs. The system is to be used whenever the aircraft is on the ground and ambient temperature is above 50F and should not be used above 15,000 feet.



Panel Location

Original Flight Hardware: Environmental Control System (ECS) (Sub-Panel)

The Environmental Control System (ECS) sub-panel is part of the large pneumatics panel located on the upper flight engineer station of the Lockheed L-1011. The panel is the measurement brains of the ECS. Here is a description of the various elements. Please note that today I don't have a Plack Flow Indicator (top left instrument).

Lets walk through the panel elements top left to bottom right:

• PACK FLOW INDICATOR ... indicators air output rate of selected pack (selected by the switch to the right of the pack flow indicator.
• PACK SELECT SWITCH ... selects the individual pack for flow and temperature indication.
• ECS TEMPERATURE INDICATOR ... indicates the temperature for position selected by pack selector switch (to the left) and ECS temperature selector switch (to the right).
• ECS TEMPERATURE SELECTOR SWITCH ... the temperature of each position is indicated on the ECS temperature indicator for the selected pack.
• COOL AIR OVERBOARD SWITCH ... controls overboard cooling air valves form galley and avionics compartments. IN - CLOSE is extinguished; opens galley overboard valve and arms both avionics compartment valves to open if flow is restricted. Both avionics valves open on the ground. OUT - CLOSE is illuminated and all three valves close.
• ECS MONITOR AVIONICS AIRFLOW INDICATORS ... OVBD is illuminated when respective cooling air overboard valve is open. LO FLO is illuminated when air in ventilation duct is too warm or flow is restricted (fans are operating).
• CARGO HEAT SWITCHES ... IN - recirculating fan motor is controlled by temperature sensing switch. COLD is illuminated when temperature is below minimum limit. When temperature exceeds maximum limit, HOT is illuminated and fan is turned off. OUT - recirculating fan is turned off and HOT is extinguished. COLD is illuminated if temperature is below minimum limit.
• CABIN AIR TEMPERATURE INDICATOR ... temperature of zone or duct for the position selected on cabin zone temperature selector (to the right) is indicated.
• CABIN ZONE TEMPERATURE SELECTOR ... temperature for selected zone or duct position is shown on cabin temperature indicator.
• ZONE/DUCT TEMPERATURE SELECTOR SWITCH ... IN - DUCT is illuminated. Temperature of selected zone discharge duct air is shown on cabin air temperature indicator. OUT - ZONE is illuminated. Temperature of selected zone is shown on cabin temperature indicator.