Chapter 2.1.3- Engine Control System

Question 1

What are the major components?

Answer 1

HMU, ODV, EDECU, alternator, fuel flow control valves

Question 2

What is the relationship between HMU and EDECU?

Answer 2

HMU provides gas generator control and EDECU trims the HMU

Question 3

Engine Control quadrant

Answer 3

2 PCLS, 2 fuel selectors, 2 engine t-handles, rotor brake interlock

Question 4

PCL positions

Answer 4

OFF - shuts off fuel at fuel shutoff valve in HMU
IDLE- HMU automatically controls start sequence fuel flow
FLY- sets max level of power that could be supplied if demanded
LOCKOUT - PCL used to manually control Np and Ng

Question 5

What do you lose in LOCKOUT?

Answer 5

TGT limiting, Np governing, and loadsharing

Np overspeed protection is retained

Question 6

What does the rotorbrake interlock do?

Answer 6

Prevents the PCLs from being advanced above idle with rotor brake on

Question 7

Load Demand System

Answer 7

FLY - HMU responds to collective position

LOCKOUT - engine will still vary power in regards to collective position

Question 8

Engine Drive Fuel Pump

Answer 8

Provides reliable suction fuel from fuel tank to engine

Provides discharge pressure to satisfy high pressure fuel pump

Question 9

Parts of HMU

Answer 9

Ng governor
Fuel pump
Metering valve
Torque Motor Servo
Variable geometry servo
Metering valve
Ng overspeed valve
LVDT

Question 10

Engine Fuel Filter

Answer 10

Filtration of solid particulate matter only

Pressure differential across the filter, impending bypass PDI extends, and cannot be reset until the filter element and bowl are removed.

FUEL BYPASS illuminates when bypass valve opens

Question 11

HMU Fuel taps

Answer 11

Metering valve
variable geometry vane servo and start bleed valve
Amplifies signals (t2, p3, Ng)

Question 12

HMU inputs

Answer 12

2 mechanical, 1 electronic
LDS, PCL, and EDECU

Question 13

HMU operation

Answer 13

Failsafe to high power - loss of electrical current to torque motor servo will return to highest power level

Power Available with OEI - In engine failure, good engine can increase pwer up to contingency power

Question 14

HMU provides?
RANFAN

Answer 14

Rapid engine transient response through collective compensation
Auto fuel scheduling for engine start
Ng overspeed protection - 110+-2%
Ng governing
Acceleration limiting
Flameout and compressor stall protection

Question 15

ODV provides? PPTR

Answer 15

Provides fuel to 12 fuel injectors
Purges fuel overboard after shutdown to prevent coking
Traps fuel upsteam in the fuel/oil heat exchanger
Returns fuel to HMU if Np overspeed is energized or hot start

Question 16

Engine limiting

Answer 16

TGT limiting - by reaching MRP or CRP within EDECU
HMU Fuel limiting - Max fuel flow limited by size of fuel lines, HMU protector compressor by limiting fuel flow
Increasing collective during TGT limiting will result in droop
Torque limiting - Ch4 limits
Ng limiting - Ch4 Limits