Engines - General (RB211) Show Schematic only

Amendments: Engine Speed card.

Introduction

Rolls Royce.

The 757-200 airplane is powered by two Rolls-Royce RB211-535E4 engines rated at 40,100 pounds of takeoff thrust each.

The 757-300 airplane is powered by two Rolls-Royce RB211-535E4-B engines rated at 42,700 pounds of takeoff thrust each.

Rolls-Royce RB211-535E4 cross-section, showing detail of the 3-rotor systems
image source: www.eng.uct.ac.za/~victor/electric/GasTurbine.htm

The engines are three-rotor axial flow turbofans of high compression and bypass ratio. The N1 rotor consists of the Fan and a Low Pressure turbine section on a common shaft. The N2 rotor consists of an Intermediate Pressure compressor section and an Intermediate Pressure turbine section on a common shaft. The N3 rotor consists of a High Pressure compressor section and a High Pressure turbine section on a common shaft. The N1, N2 and N3 rotors are mechanically independent. The N3 rotor drives the engine accessory gearbox.

Accessory Gearbox

The Engine Accessory gearbox drives the:

 

The Air-Driven Starter connects to the N3 rotor through the accessory gearbox.

Each engine has individual flight deck controls. Thrust is set by positioning the Thrust Levers. The thrust levers are positioned automatically by the autothrottle system or manually by the flight crew.

Each engine is controlled by an Electronic Engine Controller (EEC). The EECs monitor autothrottle and flight crew inputs through the Thrust Levers to automatically control the engines.

The engine incorporates automatic surge bleed valves to ensure good starting characteristics plus surge and stall free operation throughout the airplane's flight envelope.

Engine Indications are displayed on the Engine Indication and Crew Alerting System (EICAS) display.

Engine Speed Card

AMM The engine speed card receives a voltage input from the N3 tachometer transmitter proportional to the N3 rotor speed. Powered by the Standby DC Bus and using 45% N3 RPM as the threshold, the engine speed card supplies "Engine Running/Not Running" information to the:

 

Bleed Valve Control Unit

AMM To keep a stable airflow through the compressor section during certain transient and steady running conditions, a percentage of air is vented from the Intermediate Pressure (IP) and high pressure (HP) compressors. This is achieved through solenoid operated bleed valves controlled by an electronic Bleed Valve Control Unit (BVCU). An integral part of the BVCU also provides automatic control of the bleed valves in the event of abnormal deceleration of the engine at high power settings, as may be caused by a bird strike or surge.

Note: These bleed valves are separate to the normal pneumatic system engine bleed air valves

EICAS