L-1011 Engine: Rotating Assemblies

The RB.211 engines used on the Lockheed L-1011 have three rotating assemblies rather than two. Many more stages would be necessary to get the same compressions ratio which would create a very long engine. The 3 spooled design results in a short rigid engine which has less parts.

Compressors are referenced as a Low Pressure (LP), Intermediate  Pressure (IP) and High Pressure (HP).

The HP compressor drives accessories through a step aside gear box. Accessories are mounted on the LH and LP compressor case. 

L-1011 Engine: RB211-524B-02 Engine (71-1)

The Rolls Royce RB211-524 engine is flat rated to 84ºF ambient temperature with 50,000 lbs. of thrust. The engine has three spools: N1, N2 and N3.

• N1 - Low Pressure (LP) compressor which a single stance fan and three stage turbine. 
• N2 - Intermediate Pressure (IP) compressor with a 7 stage axial flow single stage turbine 
• N3 - High Pressure (HP) compressors with a 6 stage axial flow single stage turbine 

Direction of orations is counterclockwise as viewed from the rear. The image above show the hot stream air slow as well as the cold stream airflow. 

L-1011 APU: APU Application (49-11)

Flow of pneumatic air from the APU load compressor can be monitored and controlled at the Flight Engineer's Engine Bleed Control Panel. Duct pressure may be monitored on the duct pressure indicators.

As can be seen from the panel schematic, APU pneumatic air is available for engine starting, ATM operation, or air conditioning pack operation. APU air is never mixed with air from another source to prevent damage to the APU. 

L-1011 APU: APU Fuel Supply (49-10)

Fuel for the APU is supplied by the aircraft fuel system through the No. 2 engine fuel tank valve and fuel line. By using cross feed, fuel can be supplied by any tank to the APU. Two emergency shutoff valves are provided to isolate fuel from the APU in case of fire. In-transit lights for the valves are located on the Flight Engineer's fuel panel. 

L-1011 APU: Fault Flags (49-7)

There are four fault circuits that will cause the APU to shut down to protect against malfunctions that could damage the APU. The fault circuits are:

• OVERSPEED N2 - Free turbine speed in excess of 110%
• LOW PRESS OIL - Oil pressure drop below 50 PSI for 10 seconds with ≥ 55% RPM
• HIGH OIL TEMP - Protects against high oil temperature
• OVERTEMP TGT - Protects against over temperature TGT during starting and in normal operation. 

Any fault or combination of faults will shut down the APU automatically. 

L-1011 APU: APU Controls (49-6)

Most of the controls and indicators for normal operation are located on the APU control panel at the Flight Engineer's station.

Two indicators are provided for monitoring gas generator RPM and TGT.

There are seven advisory lights to indicate abnormal conditions. Switches for controlling starting, stopping, and pneumatic air supply controls are located on the control panel. A switch for arming the Auto Fire Shutdown circuit to allow unattended operation of the APU is also located on the APU control panel.

L-1011 APU: APU Doors (49-5)

Ambient air enters the gas generator through the engine inlet door. The air passes through a four stage compressor, three axial and one centrifugal stage, and enters a combustion chamber. Fuel is mixed with compressed air and ignited. The resultant gasses expand driving the gas generator turbine and the free turbine.

The free turbine is driven at a constant speed to maintain a frequency of 400Hz at the APU generator. The APU generator is driven by the free free turbine through an adapter gearbox. A cooling fan is also driven by the adapter gearbox.

The cooling fan provides cooling airflow for the APU hot section, exhaust manifold and oil cooling.

A load compressor is also driven by the free turbine. The load compressor receives ambient air through an opening in the fuselage. The air passes through a set of inlet guide vanes which control the amount of air to the load compressor. Air from the load compressor is then routed to the aircraft systems if needed, excess load compressor output is dumped into the exhaust manifold through a surge dump valve.

L-1011 APU: APU Operation and Location (49-3/4)

The APU can be started from sea level to flight level 250 and will operate up to flight level 310.

The APU is installed at the rear of the aircraft below the No. 2 engine "S" duct forward of the No. 2 engine firewall. The APU is contained in a fireproof compartment and the platform the APU is mounted on is part of the aircraft skin. 

L-1011 APU: Overview (49-1/2)

The Auxiliary Power Unit (APU) is installed on the L-1011 as an auxiliary power source to be used primarily on the ground. The APU can also be used in flight as a back-up for the aircraft's pneumatic, hydraulic, and electrical systems.

The APU will supply pneumatic power for air conditioning, engine starting and to power the ATM's for hydraulic power.

The APU generator can supply up to 81 KW to an altitude of 14,000 and 54 KW above 14,000 feet. 

L-1011 Navigation: INS CDU (34-43)

This is the CDU as it appears with the test switch pressed. The intensity of all controls which are shown illuminated is controlled by the DIM knob on top of the data selector. The illumination of the keyboard is controlled through the center pedestal rheostat (external to the device). 

L-1011 Navigation: Model Selector Unit (INS) (34-43)

 The attitude position (ATT) disables the navigation computer but retains the platform for attitude reference.

There are two mechanical stops - one between the standby and align positions of the switch, and one between the NAV and ATT positions. To move the switch past the stop, the switch must be pulled up and rotated past the stop. Once the mode selector has been placed in the NAV position, it can be returned to the align position without dumping the program in the computer. However, if the switch is placed in either the standby or attitude positions, the program is cleared and the set must be realigned before it can be used for navigation. 

L-1011 Navigation: Inertial Navigation Systems (34-43)

The NAV position is the normal operating position. The mode switch must be placed to NAv, and the computer must enter the NAV mode prior to moving the aircraft. If the aircraft is moved prior to entering the NAV mode, the computer will dump its program and the set will have to re-aligned. If the mode selector is place directly to NAV and present position inserted, the set will cycle through the standby and align modes and enter the NAV mode; however, placing the switch to NAV directly would be an abnormal procedure.

Automatic overheat protection is disabled in the NAV mode to prevent inadvertent shutdown in flight. 

L-1011 Navigation: Inertial Navigation System (34-38)

Additional controls for the Inertial Navigation System are the mode selectors, the control display units and the associated aircraft interfaces.

The standby position erects the gyros and brings he computer up to temperature. When the selector switch is standby, automatic overheat shutdown protection is also provided.

The mode selector switch is normally positioned directly from off to align. The computer will automatically progress through the standby mode and enter the alignment mode. The alignment cycle requires a minimum of 11.5 minutes and must be completed before the aircraft is taxied. Automatic overheat shutdown protection is also provides in the ALIGN mode.

The green light indicates that alignment process has progressed to he point where the set is capable of navigation. This light will illuminate with the mode selector switch in the align position and extinguishes when the computer entered the navigation mode.