FADEC

Question 1

What does FADEC stand for?

Answer 1

Full Authority Digital Electronic Control

Question 2

What is the FADEC designed to do?

Answer 2

Enhance flight safety

Reduce pilot workload

Question 3

What are the FADEC provisions?

Answer 3

Provides:

• Precise control of Nr
• Engine automatic start
• Crew Alerting System (CAS)

Question 4

What does the CAS provide?

Answer 4

• Continuous monitoring
• Reduced signal sensing
• Self diagnostics

Question 5

Give a general description of FADEC version and components.

Answer 5

The FADEC is a 5.4 version using a single channel control with 1 microprocessor and 1 electronic lane
With a MANUAL mode Hydromechanical (HMU) backup
2 Main components:
1. Airframe Mounted ECU (brains)
2. Engine Mounted HMU (muscle)

Question 6

What does the ECU do?

Answer 6

Monitors inputs to send signals to the HMU for proper fuel flow modulation instructions

Question 7

How many sources does the ECU receive information from, and what are they?

Answer 7

1. MGT
2. Ng
3. Np
4. Nr
5. Engine Torquemeter Oil Pressure (TMOP)
6. Collective Pitch (CP) and Rate
7. Compressor Inlet Temperature (CIT)
8. Ambient Pressure (P1)
9. Power Lever Angle (PLA)/Throttle Position

Question 8

What makes up the HMU?

Answer 8

2FFCAHO (2 fuzzy fuzzy caterpillars attack henry outside)

• 2 stage fuel pump
• Fuel metering assembly
• Fuel Shutoff Valve
• Changover solenoid valve
• Altitude compensated bellows
• Hot start fuel solenoid valve
• Overspeed Valve

Question 9

How many modes of fuel modulation does the HMU provide and what are they?

Answer 9

1. AUTO - via a stepper motor

2. Manual - hydro-mechanical actuator

Question 10

When does the FADEC have complete control over engine operation?

Answer 10

Flight in AUTO with throttle in fly (PLA 70 degrees) the FADEC has complete control over engine operation to maintain Nr within limits.

Question 11

What makes up the Digital Electronic Control System?

Answer 11

2 Electrical Governors

1. Primary channel - controls, monitors, limits engine power
2. Reversionary Governor - can automatically take control of engine if primary fails, only has a limited set of inputs, and provides basic electronic governing

Question 12

What is the FADECs power source?

Answer 12

28VDC bus supplies electrical power to the ECU until engine achieves 85% Np

Above 85% Np ECU selects power source with highest voltage as primary, other as secondary

1. 28 VDC bus
2. Engine-Driven PMA

Question 13

How does the aircraft operate in AUTO mode?

Answer 13

1. With throttle in FLY (PLA 70 degrees) the FADEC has complete control of engine operations to maintain Nr
2. ECU takes inputs and sends instructions to HMU
3. HMU modulates stepper motor and adjusts fuel metering valve to achieve desired engine performance

Question 14

How does the aircraft operate in MANUAL mode?

Answer 14

1. The fuel metering valve responds to PLA position
2. High pressure fuel enters both sides of HMU into 2 pistons: Manual Load Piston (slow piston) and then PLA Follower Piston (fast piston)
3. The pistons move to contact the fuel metering valve
4. When the pilot moves the controls the varying fuel pressure in the HMU moves pistons which moves the fuel metering valve enabling the pilot to control engine rpm

Question 15

Explain the transition of the pistons to MANUAL mode at a LOW fuel flow.

Answer 15

Initial condition: AUTO Mode, low engine fuel flow, throttle in FLY position

1. FADEC to MANUAL mode (either selection or direct reversion to)
2. AUTO/MANUAL changeover solenoid - de-energized: allowing fuel into the Manual load piston and PLA follower piston.
3. PLA follower piston “rapidly” extends to contact fuel metering valve in ~1.0 sec
4. Concurrently, Manual load piston “slowly” extends engaging metering valve lever in ~2.0 seconds.
5. When both pistons engage, MANUAL Mode is established and no delay exists between throttle (PLA) movement and fuel flow changes.

Question 16

Explain the transition of the pistons to MANUAL mode at a HIGH fuel flow.

Answer 16

Initial condition: AUTO Mode, low engine fuel flow, throttle in FLY position

1. FADEC to MANUAL mode (either selection or direct reversion to)
2. AUTO/MANUAL changeover solenoid - de-energized: allowing fuel to enter the Manual load piston and PLA follower piston.
3. PLA follower piston “rapidly” extends in ~0.1 seconds to to contact the fuel metering lever
4. Concurrently, Manual load piston “slowly” extends, engaging metering valve lever in 6.0-7.0 seconds.
5. When both pistons engage, MANUAL Mode is established and no delay exists between throttle (PLA) movement and fuel flow changes.

Question 17

Which is the “slow” piston?

Answer 17

Manual Load Piston

Question 18

Which is the “fast”piston?

Answer 18

PLA Follower Piston

Question 19

How many CAS messages are related to the FADEC and what are they?

Answer 19

8 total

Warning (red)

1. Engine Out
2. Engine Overspeed
3. FADEC Fail

Caution (yellow)

4. FADEC Degraded
5. FADEC Fault
6. FADEC Manual

Advisory (white)

7. Restart Fault
8. Auto Relight

Question 20

How many categories of FADEC faults are there and how are they divided?

Answer 20

5 total

4 related to Inflight Emergencies
1 related to Maintenance Advisory faults displayed on shut down

Question 21

What are the 5 categories of FADEC Faults?

Answer 21

1. FADEC Fail/FADEC Manual - Direct Reversion to Manual Mode
2. FADEC Degraded
3. FADEC Fault
4. Restart Fault
5. FADEC Reversionary Governor

Question 22

Describe the FADEC Fail/FADEC Manual fault category.

Answer 22

Direct Reversion to Manual Mode either through selection or FADEC failure.

Question 23

Describe the FADEC Degraded fault category.

Answer 23

Remains in AUTO mode
Displayed Immediately
Possible Nr droop or lag

Question 24

Describe the FADEC Fault, fault category.

Answer 24

Remains in AUTO mode
Displayed Immediately
PMA/MGT/Ng/Np limiting not available

Question 25

Describe the Restart Fault, fault category.

Answer 25

Shouldn't affect performance Displayed Immediately Wont be able to restart in AUTO mode

Question 26

Describe the Maintenance Advisory fault category.

Answer 26

Displayed on Shutdown | Maintenance Action Required

Question 27

What is the FADEC Hot Start Logic

Answer 27

1. >885C less than 10,000 2. >912C greater than 10,000 3. <10.3 VDC Starter stays engaged for 60 seconds until the MGT is <150C

Question 28

Engine Overspeed Protection

Answer 28

Np 102.1% and above for 2.5 seconds Np 107.3% immediately 1. At 118.5 +/- 1% activates solenoid, reducing fuel 2. At 112.5 +/-2% deactivates solenoid, resuming fuel 3. If uncontrollable, it holds 112.5-118.5% using throttle and collective

Question 29

FADEC Maint CAS

Answer 29

FADEC lamp test failure during power-up self test and in flight -mx action required

Question 30

Describe flight in Manual Mode

Answer 30

- High pressure fuel enters both sides of HMU and moves pistons (Manual Load and PLA Follower) from parked positions into contact with fuel metering valve - Throttle manipulation changes PLA to achieve variable fuel pressure in the PLA Follower piston - Varying fuel pressure in HMU moves fuel metering valve lever to enable pilot to effectively control engine RPM

Question 31

What is the purpose of the Reversionary (Backup) Governor?

Answer 31

During certain fault conditions, in order to eliminate a FADEC Fail, it allows for operations to continue in AUTO mode with some degraded items.

Question 32

What are the CAS messages associated with the operation of the Reversionary Governor? What are the flight results and actions?

Answer 32

FADEC Fault Restart Fault FADEC Degrade Possible Nr droop/lag Continued flight in AUTO mode Fly smoothly Maintenance required prior to next flight