Simulator Integration Planning: ATA 21 - Air Conditioning and Pressurization

ATA 21 is the Systems chapter for Air Conditioning and Pressurization (a complete listing of ATA chapter numbers can be found here). I decided to work through the simulator system integration according to the ATA chapters and that way everything stays in a somewhat logic order. The upper panel of the flight engineer console on the L-1011 is largely consumed by control and indicator elements for ATA 21 and ATA 36 (which is Pneumatic).

Below are images from the original documentation of the L-1011 simulator created by Singer Link Division in the 1980s.

Environmental Control System (ECS) Monitor Panel (*791/A9)

The simulator implements all component pieces of the ECS monitoring panel.

L-1011 Trainer - ECS Monitoring System (Component Labels)

Implemented Components

Gauges
M10 ... Pack Flow 
M11 ... ECS Temperature
M12 ... Cabin Temperature

Switches
S10 ... Pack Select 
S11 ... ECS Temperature Select 
S12 ... Cabin Zone Temperature Select    

Switch Lights
SDS26 . Cool Air Overboard
SDS27 . Cargo Heat Forward
SDS28 . Cargo Heat Mid
SDS29 . Cargo HEat Aft
SDS30 . Instrument Cooling

Annunciators
DS14 .. Avionic Air Forward
DS15 .. Avionic Air Mid

Cabin Pressurization (*791/A9)

Several of the gauges for the pressurization panel are photo simulations on the original Singer Link Division L-1011 simulator. These instruments will be replaced with the real flight hardware as part of the simulator outfit at the museum. However, several switch and annunciator elements are already fully implemented.

L-1011 Trainer - Pressurization (Component Labels)

Implemented Components

Gauges

M1  ... Forward Outflow Valve 

M2  ... Aft Outflow Valve

Switches

S1  ... Forward Outflow Valve Manual Control 

S2  ... Aft Outflow Valve Manual Control 

S9  ... Cabine Altitude Horn Cutout

Switch Lights

SDS1 .. Forward Outflow Valve Manual/Automatic

SDS2 .. Aft Outflow Valve Manual/Automatic

Annunciators

DS12 .. Forward Safety Valve 

DS13 .. Aft Safety Valve

Cabin Temp Control (*791/A9)

The Cabin Temperature and Engine Bleed Control panels are combined. The lower portion of the panel is the cabin temperature control panel. For the ATA 21 integration we will only cover the lower portion of the panel. 

Implemented Components

Gauges
M4  ... #1 Turbine Bypass Valve Position 
M5  ... #1 RAM AIR Valve Position
M6  ... #2 Turbine Bypass Valve Position 
M7  ... #2 RAM AIR Valve Position
M8  ... #3 Turbine Bypass Valve Position 
M9  ... #3 RAM AIR Valve Position

Switches
S1  ... #1 Valve Cool
S2  ... #1 Valve Warm
S3  ... #2 Valve Cool
S4  ... #2 Valve Warm

S5  ... #3 Valve Cool
S6  ... #3 Valve Warm

S7  ... Area Overheat

S8  ... Area Overheat Test

Switch Lights
SDS10 . #1 Pack Flow Control
SDS11 . #2 Pack Flow Control 
SDS12 . #3 Pack Flow Control
SDS13 . #1 Valve Control Auto and Manual
SDS14 . #2 Valve Control Auto and Manual
SDS15 . #3 Valve Control Auto and Manual
SDS16 . Left Hot Air 
SDS17 . Right Hot Air
SDS18 . Left Isolation Valve
SDS19 . Right Isolation Valve
SDS20 . Ground Cont
SDS21 . Flight Station Open Close
SDS22 . Forward Cabin Open Close
SDS23 . Mid Cabin Open Close
SDS24 . Aft Cabin Open Close
SDS25 . Galley Open Close

Annunciators
DS7 ... Area A Overheat
DS8 ... Area H Overheat
DS9 ... Area B Overheat 
DS10 .. Area C Overheat
DS11 .. Planum Duct Overheat

Avionics Bending: ECS Temperature Indicator (Pinout)

The L-1011 ECS temperature indicator is part of the ECS monitoring panel. There are actually two temperature gauges on that sub panel, one to measure various ECS system temperature outputs and the other to measure cabin zone temperature with. The one described here in this posting is the one displaying ECS system temperatures.

The schematic below is in fact for the Cabin Temperature gauge, however, the ECS Temperature indicator is built exactly the same way.

The pinout of the instrument is rather simple.

Pin 1: 5V AC Lighting
Pin 2: 5V AC Lighting
Pin 3: 115V 400Hz Power In
Pin 4: 115V 400Hz Lo
Pin 5: Temperature Sensor +
Pin 6: Temperature Sensor -

Avionics Bending: RAM Position Indicator (Pinout)

The L-1011 has three air-conditioning packs. Each of the Packs has a RAM Air intake that can be controlled an Turbine By-Pass Valve that can be controlled from the ECS panel. In essence, what the instrument indicates is the valve posting from all the way closed to all the way open. These valves are either driven automatically by the climate control system or they can be operated by manually with the monetary switches located below the indicators.

The instrument again is a rather simple indicator and here is the schematic for it:

By the way the schematic and the pinout is identical for the Turbine Bypass indicator.

Here is the pin-out:

Pin A: 5VAC Lighting
Pin B: 5V AC Lighting
Pin C  Instrument and Sensor Power
Pin D: Pot-H
Pin E: Pot - Wiper form Sensor Side
Pin F: Pot-L

Avionics Bending: Pack Flow Indicator (Pinout)

The pack flow indicator shows the amount of cubic feet of ear being cycled through the packs per minute. The pack selector to the right selects which pack flow is being indicated.

The instrument is very basic and only uses four pins, two for instrument lighting and two for the DC indicator value. 

Here is the instrument pinout:

Pin 1 - 5V AC Lighting
Pin 2 - 5V AC Lighting
Pin 4 - Pack Flow GND
Pin 5 - Pack Flow Value (+)

L-1011 ECS: Cold Air Plenum (21-14)

Outputs from all three air conditioning packs discharge through a check valve and into a common chamber called the cold air plenum.

The cold air plenum is a rectangular box which receives air from the three air conditioning packs, then mixes and distributes the available air to the four aircraft zones. The plenum is decided down its whole length by a perforated baffle. The air from packs 2 and 3 and approximately 60% of pack No. 1 air is mixed together for distribution to the three cabin zones. The other 40% from pack No. 1 is diverted by another baffle which directs the supply towards the flight station outlet duct.

The plenum is located at the rear right hand side of the FESC.

L-1011 ECS: Cabin Airflow (21-13)

The conditioned air is distributed throughout the cabin zones from ducting that runs up the forward right side of the fuselage to three supply ducts located above the passenger cabin ceiling. The air entered the cabin zones through aspirator units that are attached on the bottom side of the distribution ducting. This creates circulation of the air by mixing existing cabin air with the incoming conditioned air. The total volume of air in the cabin is changed approximately every 4 minutes. The cabin air then exhausts through grills in the sidewalls of the cabin floor venting down through the lower compartments before passing overboard through the pressurization outflow vales. 

L-1011 ECS: Pack and Temperature Control

The control and operation for the air conditioning pack system and the zone trim system is accomplished from the lower half of the engine bleed cabin temp control panel (aka. ECS panel). The operation of each system is automatic. In case the automatic function fails,t here is a manual control for pack and zone temperature operation. 

L-1011 ECS: Hot Air Manifold (21-15)

The pneumatic bleed air after it has been cycled through the air conditioning packs and distributed into the cold air plenum is too cold for distribution to the cabin zones by it self. During normal operation, all packs are programmed to provide air of a temperature required by the zone calling for the coldest temperature. To prevent other zones from being too cold, pack 2 and 3 also supply temperature regulated hot air which comes from the output of the primary heat exchanger and a tap off prior to the heat exchangers, to the hot air manifold. Hot air is then ducted to the hot air zone trim valves which modulate to maintain the selected temperature for each zone by mixing the air leaving the cold air plenum with the hot zone trim air. 

L-1011 ECS: Cabin Pressure Control Panel (21-17/18)

The pressure control panel is located on the FE/SO upper control panel. The pressure control panel provides selection of the cabin pressure planned parameters. On the panel, the selectors and controls asset in the programming of the required cabin pressure, while indicators monitor the outflow valve position. The resulting cabin altitude levels and rates of pressure change are provided by aircraft indicators in order to monitor passenger comfort levels. 

The profile displays the cabin altitude in relation to normal operating differential pressure. As can be seen, the cabin can be maintained at sea level up to an aircraft altitude of 22,000 feet and will not exceed a cabin altitude of 8,000 feet when the aircraft is at 43,000 feet when maintaining a max. operating pressure differential of 8.44 psi. 

L-1011 ECS: Cabin Altitude And Differential Pressure Indicator (21-23)

The main function of the cabin altitude and differential pressure indicator is to monitor the cabin altitude and cabin differential pressure throughout the flight.

The indicator has two scales (or two instruments in case of a TWA or Eastern panel configuration), the outer scale and larger pointer represents cabin altitude in thousands of feet. The barometric knob and window are used to set the correct barometric pressure in inches of mercury to correct for non-standard day conditions. Only this gauge is affected by the setting.

The inner scale and small pointer indicate cabin differential pressure. The amber range represents the maximum differential pressure controlled by the outflow valves. The red range represents the maximum  differential pressure which is limited by the positive pressure safety valves. Note that the maximum differential pressure for takeoff and landing is 0.15 psi and is placarded above the indicator. A pressure lower than 0.15 psi will allow all exits to be able to open in case of an emergency evacuation. 

L-1011 ECS: Outflow Valves (21-22)

Pressurization is maintained by two electrically driven outflow valves. Both outflow valves are located on the lower left side oft he fuselage. The outflow valves maintain pressure by restricting the outflow of air from the aircraft. With one outflow valve closed, the remaining outflow valve is sufficient to control normal pressurization.

Each outflow valve has an AC and DC motor which drives the outflow valve through common push rod linkage and gearing. The AC motor is utilized for normal (automatic) operation and standby (semi-automatic) operation. The DC motor is used as a backup in case of failure of the normal or standby mode. Manual operation is selected by latching in the MNL switch lights and controlled using the three-position toggle switches.

The position of the outflow valve is displayed by two indicators on the pressurization panel. 

L-1011 ECS: Normal Rate Selector (21-21)

The normal rate selector controls the cabin altitude rate of change when the mode selector is in the NORM position. When set a the DOT, the cabin rate of change is approximately 500 feet per minute up and 300 feet per minute down. The desired rate of cabin change can be changed by selecting different positions with the rate knob. Here are the pressurization rate limitations:

Ascent

• Minimum 50 to 400 FPM
• Dot Indexed 400 to 850 FPM
• Maximum 1250 to 2400 FPM 

Descent 

• Minimum 50 to 350 FPM
• Dot Indexed 150 to 550 FPM
• Maximum 750 to 1450 FPM

L-1011 ECS: Cabin Pressure Control Panel (21-20)

Cabin pressure is controlled electronically and is regulated electromechanical. The pressurization control system regulates and maintains cabin pressure and the rate of cabin pressure change as a function of settings on the pressure control panel. This is accomplished by regulating the exhaust airflow from the cabin through two motor-driven, variable-gate cabin outflow vales. The pressurization control system generates the necessary controlling signals to regulate the position of the outflow valve gates. This can be accomplished in any of the three modes of operation: Normal (NORM) Mode, Standby (STBY) Mode or MANUAL. The pressure control panel also provides a check (GND CHK) mode that conduct checks of the system while on the ground. 

L-1011 ECS: Air Distribution (21-19)

The pressurized areas of the aircraft  are the cabin area, flight station, FESC, forward cargo, MESC and the mid and aft cargo areas. The only pressures area on the L-1011 not accessible in flight are the mid and aft cargo hold areas. 

L-1011 ECS: Pneumatic System Valves (21-10)

By unlatching various switch lights any single or all bleed air sources can either be isolated or completely turned off. 

L-1011 ECS: Crossbleed Valves (21-9)

The main purpose of the crossbreed valves is so each bleed channel can be individually  isolated. IT allows flow from either direction and they lock closed automatically for high flow trips. With loss of electoral power the valve automatically closes. 

L-1011 ECS: Engine Isolation Valve

Primary functions of the Engine Isolation Valve are:

• Shut-Off Valve
• Pressure Regulator
• Check Valve

It also allows revers flow during engine start, APU/GND air to reverser switch during engine shutdown.
The engine isolation valve locks closed automatically for; a duct overheat, bleed duct overpressure, excessive flow and will close when the fire handle is pulled. With loss of electrical power the valve is fail save open. 

L-1011 ECS: Bleed Air Channels (21-7)

The pneumatic supply system consists of distribution manifold, components and three essentially identical engine bleed channels, which provide regulation and distribution of Low Pressure (LP) and High Pressure (HP) air to the various pneumatic systems on the aircraft. 

L-1011 ECS: Engine Bleed Air (21-5/6)

The Bleed Control System supplies pneumatic air from three available sources to operate various systems throughout the aircraft.  The major bleed air users are:

• Air Conditioning 
• Engine Starters
• Wing Anti-Ice
• ATM Operation 
• Cabin Pressurization

The image below shows the approximate location of these bleed air consumers:

L-1011 ECS: Overview (21-1)

The Environmental Control System (ECS) consists of the following systems:

• Pneumatic Supply System - Provides the source of cabin air supply by selecting engine bleed air from the proper compressor stage, and regulating the temperature, pressure, and flow of this air supplied to the using systems. 
• Pack Control System - Regulates the cooling of air provided by each of the three air conditioning packs according to the demands of the 4 temperature zones in the aircraft.  
• Zone Control System - Regulates the addition of warm trim air to the pack outputs for those 4 zones requiring warmer supply air than provided by the packs. 
• Pressurization Control System - Controls the flow of air out of the cabin to maintain a comfortable cabin pressure, and to maintain the selected rate of pressure change during ascent and descent 

These major systems are operated and controlled from the Environment Control Panel which dominates the upper section of the flight engineer station. The engine bleed and cabin temperature control portion of being on the left side of the ECS panel, provides for the operation and control of the pneumatic bleed air supply system and the air conditioning Pack Control/Zone Control system. The pressurization control is operated, controlled and monitored from the pressurization panel in the upper right hand portion of the panel. The ECS monitor panel in the lower right hand portion was incorporated in the system for monitoring the performance of the Engine Bleed/Cabin Temperature Control System, to trouble-shoot individual systems and to aid in writing accurate squawks.