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Bell 407 > FADEC > Flashcards

FADEC Flashcards

1
Q

What does FADEC stand for?

A

Full Authority Digital Electronic Control

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2
Q

What is the FADEC designed to do?

A

Enhance flight safety

Reduce pilot workload

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3
Q

What are the FADEC provisions?

A

Provides:

  • Precise control of Nr
  • Engine automatic start
  • Crew Alerting System (CAS)
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4
Q

What does the CAS provide?

A
  • Continuous monitoring
  • Reduced signal sensing
  • Self diagnostics
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5
Q

Give a general description of FADEC version and components.

A

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)

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6
Q

What does the ECU do?

A

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

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7
Q

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

A
  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
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8
Q

What makes up the HMU?

A

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
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9
Q

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

A
  1. AUTO - via a stepper motor

2. Manual - hydro-mechanical actuator

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10
Q

When does the FADEC have complete control over engine operation?

A

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

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11
Q

What makes up the Digital Electronic Control System?

A

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
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12
Q

What is the FADECs power source?

A

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
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13
Q

How does the aircraft operate in AUTO mode?

A
  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
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14
Q

How does the aircraft operate in MANUAL mode?

A
  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
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15
Q

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

A

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.
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16
Q

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

A

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.
17
Q

Which is the “slow” piston?

A

Manual Load Piston

18
Q

Which is the “fast”piston?

A

PLA Follower Piston

19
Q

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

A

8 total

Warning (red)

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

Caution (yellow)

  1. FADEC Degraded
  2. FADEC Fault
  3. FADEC Manual

Advisory (white)

  1. Restart Fault
  2. Auto Relight
20
Q

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

A

5 total

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

21
Q

What are the 5 categories of FADEC Faults?

A
  1. FADEC Fail/FADEC Manual - Direct Reversion to Manual Mode
  2. FADEC Degraded
  3. FADEC Fault
  4. Restart Fault
  5. FADEC Reversionary Governor
22
Q

Describe the FADEC Fail/FADEC Manual fault category.

A

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

23
Q

Describe the FADEC Degraded fault category.

A

Remains in AUTO mode
Displayed Immediately
Possible Nr droop or lag

24
Q

Describe the FADEC Fault, fault category.

A

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

25
Q

Describe the Restart Fault, fault category.

A

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

26
Q

Describe the Maintenance Advisory fault category.

A

Displayed on Shutdown

Maintenance Action Required

27
Q

What is the FADEC Hot Start Logic

A
  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

28
Q

Engine Overspeed Protection

A

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
29
Q

FADEC Maint CAS

A

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

30
Q

Describe flight in Manual Mode

A
  • 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
31
Q

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

A

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

32
Q

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

A

FADEC Fault
Restart Fault
FADEC Degrade

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

Bell 407 (19 decks)

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