Engine control

Question 1

Requirements

Answer 1

ensure safe operation

rapid/controlled acceleration

emergency shutdown

robust

Question 2

FADEC-Full Authority Digital Engine Control

Answer 2

control of thrust

control of airflow and starting functions

interface with FM and crew control

output of maintenance and reliability data

performance optimisation

Question 3

Factors affecting thrust

Answer 3

ambient air temperature

static air pressure

aircraft forward speed

ram pressure

Question 4

Fuel flow control

Answer 4

provide crew and/or FMS with control of thrust or engine speed

maintain selected throttle setting

maintain safe engine operating parameter

start and stop the engine

Question 5

Fuel flow control schematic

Answer 5

Question 6

Problems encountered at low RPM ranges

Answer 6

the airflow through LP and HP compressors becomes unstable leading to blade stall and engine surge

Question 7

Solutions to overcome blade stall and engine surge

Answer 7

automatic airflow control to provide flow stability at aft design speeds

variable inlet guide valves or variable stator blades alter the angle at which the air is directed onto the rotor blades

interstage compressor bleed may be used to improve flow characteristics

Question 8

Compressor air bleed

Answer 8

prevents stall or surge assist in emissions control of varying air/fuel ratio

Question 9

Surge margin

Answer 9

ensures rotor blade stall and engine surge do not develop