Hydro-mechanical vs FADEC Systems

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Questions and Answers

What is the primary purpose of the fuel control unit (FCU) or fuel management unit (FMU)?

To control the exhaust gas and bypass air for forward thrust or lift

To regulate airflow through the compressor

To monitor the engine temperature and pressure

To maintain the engine speed and air flow demanded by the pilot (correct)

What is the function of the pneumatic capsules in the FCU/FMU?

To direct fuel flow

To control acceleration and deceleration rates

To restrict fuel flow

To modify flows according to prevailing atmospheric conditions (correct)

What is the purpose of the dashpot/spring/damper combinations in the FCU/FMU?

To control airflow through the compressor

To regulate fuel flow

To monitor engine temperature and pressure

To control acceleration and deceleration rates (correct)

What is the benefit of using FADEC system?

Improved engine control and monitoring Signup and view all the answers

What is the primary difference between VIGVs and VSVs?

VIGVs affect airflow at the inlet of the compressor, while VSVs vary airflow within the compressor Signup and view all the answers

What is the primary purpose of air flow control?

To maintain a safe margin from the engine surge line Signup and view all the answers

What is the evolution of engine control system based on system requirements and constraints?

From hydro-mechanical control to electronic/hydro-mechanical control to FADEC Signup and view all the answers

What is the purpose of the valves in the FCU/FMU?

To direct fuel flow Signup and view all the answers

What is the primary function of the Full Authority Digital Engine Control (FADEC) system?

To autonomously control the engine throughout its whole operating range Signup and view all the answers

Which of the following is a component of the FADEC system?

Cylinder Head Temperature (CHT) Sensor Signup and view all the answers

What is the benefit of using a FADEC system in terms of reliability?

It decreases the Mean Time Between Failures (MTBF) by 54% Signup and view all the answers

What is the function of the Health Status Annunciator (HSA) in the FADEC system?

To display the engine's health status Signup and view all the answers

How does the FADEC system improve engine control and monitoring?

By using digital sensors and computer control Signup and view all the answers

What is the advantage of the FADEC system in terms of cost?

It decreases the cost by 63% Signup and view all the answers

What is the function of the Master Power Control Units (MPC-1 and MPC-2) in the FADEC system?

To control the engine's operation Signup and view all the answers

What is the benefit of using a FADEC system in terms of weight?

It decreases the weight by 62% Signup and view all the answers

What is the primary function of a FADEC system in an aircraft engine?

To provide optimum engine efficiency for a given flight condition Signup and view all the answers

What is the role of the Engine Electronic Control (EEC) in a FADEC system?

It is the core of the FADEC system and controls engine operation Signup and view all the answers

What is the purpose of the FADEC system's adaptive control feature?

To automatically take the necessary measures to avoid exceeding a certain engine temperature Signup and view all the answers

What type of sensors are used to measure engine speed in a FADEC system?

Pulse probes Signup and view all the answers

What is the benefit of using a FADEC system in an aircraft engine?

It allows the manufacturer to program engine limitations and receive engine health and maintenance reports Signup and view all the answers

What is the function of the fuel flow control component in a FADEC system?

To control fuel flow to the engine Signup and view all the answers

What is the purpose of the FADEC system's prognostic feature?

To predict engine maintenance requirements Signup and view all the answers

What is the role of the FADEC system's air data computer (ADC) in a FADEC system?

It provides air data to the FADEC system Signup and view all the answers

What is the benefit of using a FADEC system with a centralized arrangement of servo-valves in the HMU?

It allows for more efficient engine control and monitoring Signup and view all the answers

What is the purpose of the FADEC system's diagnostic feature?

To identify engine faults and provide repair recommendations Signup and view all the answers

Study Notes

FADEC System Overview

FADEC (Full Authority Digital Engine Control) system is a type of engine control system that enables flexible and complex control, fault detection and accommodation, continual health monitoring, and airframe interface.
FADEC system provides reduced weight and cost, increased reliability, and fault reporting to flight and maintenance crews.

FADEC Background

FADEC system is able to autonomously control the engine throughout its whole operating range from demanded engine start until demanded engine shutdown, in both normal and fault conditions.
It comprises of Electric Engine Control (EEC) and other accessories that control all aspects of aircraft engine.

FADEC Components

Two Master Power Control Units (MPC-1 and MPC-2)
Sensors for manifold temperature and pressure, cylinder head temperature (CHT), exhaust gas temperature (EGT), speed, and fuel pressure
Low and high voltage harness
Throttle body assembly
Health Status Annunciator (HSA)
Fuel injection system

How FADEC Works

FADEC receives multiple input variables of the current flight condition including air density, throttle lever position, engine temperatures, and engine pressures.
It computes engine operating parameters such as fuel flow, stator vane position, and bleed valve position from this data and applies them as appropriate.
FADEC controls engine starting and restarting, and provides optimum engine efficiency for a given flight condition.
It allows the manufacturer to program engine limitations and receive engine health and maintenance reports.

FADEC System Architecture

Contains EEC, sensors, and fuel metering unit (FMU) or hybrid monitoring unit (HMU)
EEC is the core of the system
FADEC alternator provides power supply in case of electrical power failure from the aircraft.

Data and Sensors

Sensors located within the gas turbine engine measure throttle position, air data, total temperature, engine speed, engine temperature, pressure ratio, nozzle position, fuel flow, and air flow control.
Signals from sensors are transmitted to the FADEC system for processing and control.

Air Flow Control

Air flow control is used to maintain efficient operation over a wide range of environmental conditions and to maintain a safe margin from the engine surge line.
It can be controlled through variable inlet guide vanes (VIGVs) or variable stator vanes (VSVs).

FCU/FMU

Fuel control unit (FCU) or fuel management unit (FMU) is used to maintain conditions demanded by the pilot.
It is a hydro-mechanical device mounted on the engine that contains valves to direct fuel and restrict fuel flow, pneumatic capsules to modify flows according to prevailing atmospheric conditions, and dashpot/spring/damper combinations to control acceleration and deceleration rates.

Evolution of Engine Control System

Prior to 1970: Evolution of Hydro-mechanical Control
1970 – 1990: Evolution of Electronic/Hydro-mechanical Control
After 1990: Evolution of FADEC

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Description

Compare and contrast hydro-mechanical and FADEC systems, including their components and reliability. Learn about the Fuel Flow Regulator and Fuel Metering Unit in aircraft fuel control.