Original Flight Hardware: Engine Bleed Control (Sub-Panel)

This posting focuses on a sub-panel of the Pneumatic System Control Panel of the Lockheed L-1011. The panel controls engine bleed air and is labeled as ENGINE BLEED CONTROL. The panel is organized into three bleed air systems. Each engine has a system as seen in the picture below. The individual engine bleed systems are issolated from each other by cross bleed valves, which are towards the edges of the red squares.


The bleed air system for the first engine, for example, has a number of isolation valves. These valves are:

• HI PRESS ... Isolation valve for hi-pressure bleed air for engine start
• ENG ISLN VALVE ... The engine isolation valve keeps system bleed air from the engine. Or in reverse, prevents engine bleed air from entering the bleed air system.
• CROSS BLEED ... Connects the bleed air system of the engine to the number 2 and even the number 3 bleed air system.
• PACK FLOW CONTROL ... enables engine bleed air to drive the corresponding air-conditioning pack.

Bleed air duct pressure is meassured on the bleed air system side of the engine issolation valve and shown in PSI on the associated instrument.

Besides driving the A/C packs, the engine bleed air is also used to (a) start other engines with and (b) to drive a number of de-icing systems. For example, in the picture below we can see that bleed air from ENG1 (or cross bleed air) can be sued for Left Wing Anti-Ice and that the bleed air form ENG3 (or cross bleed air) can be used for Right Wing Anit-Ice operation.


Bleed air coming from the Auxiliary Power Unit (APU) enters the system right between the engine isolation valve and the ENG2 bleed air isolation valve. The APU has the ability to drive the B and the C hydraulic systems via Air Turbine Motors (ATMs). The ATM controls are on the hydraulic panel, and we will look at that at a later point.

If neither bleed air from an engine nor the APU is available, compressed air can be supplied by a ground device. Ground air enters the system through the Engine 1 and Engine 3 as well as the cross bleed duct (as seen below).



The Engine Bleed Air system is monitored by a number of AREA and DUCT OVERHEAT sensors. Each system will sound a fire alarm in the cockpit and also illuminate a fire warning on the main instrument panel.



Engine bleed air, as mentioned above, enters the vehicle climate control system through the PAC FLOW CONTROL valves (see image below). In the next posting, we will take a close look at the air handles and the CABIN TEMP CONTROL panel.