L-1011 Engine: RB.211 Airflow Controls

The air flow control system of the RB.211 engine improves the surge margin at low power acceleration and deceleration.

Variable Inlet Guide Vanes for the first stage of IP vary from -7.5º to 33.5º full close at idle. They open with increasing power.

Two IP and two HP stages. One IP and both HP valves are controlled by the VIGV control unit. The other IP has a separate control unit which closes the valve at a slightly higher pressure ratio than the first three.

When the engine is off the valves are in the following stage:

• VIGV's are Closed
• Bleed Valves are Open

When the engine is running at specific EPRs:

• EPR 1.12 both HP Valves are RH IP Closed
• EPR 1.23 LH IP closed 
• EPR 1.6 VIVG's full open