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Mesa Airlines > E175 Engines > Flashcards

E175 Engines Flashcards

1
Q

Engine Type

A

General Electric CF34-8E5. It’s a high bypass, dual-rotor turbofan engine. It has a 10-stage compressor with variable geometry, a 2-stage high-pressure turbine, a 1-stage fan, and a 4-stage low-pressure turbine.

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2
Q

Takeoff thrust time limit

A

10 minutes or POSTMOD SB 170-73-0002

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3
Q

Maximum Engine Start Temperature

A

815C

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4
Q

EICAS

A

Engine Indicating & Crew Alerting System

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5
Q

EICAS Markings

A
  • Red: Max & Min Limitations
  • Yellow: Caution Range
  • Green: Normal Operating Range
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6
Q

Flex Takeoff

A

A takeoff with reduced thrust. Thrust setting is based off an assumed temperature (telling the FADEC that it is warmer than it actually is so it will reduce the thrust)

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7
Q

Flex Takeoff Limitations

A

25% maximum reduction in thrust. Flex is Prohibited on contaminated runways.

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8
Q

ATTCS

A

Automatic Takeoff Thrust Control System. Must be on for all takeoffs and landings.

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9
Q

Engine Starter Duty Cycle

A
  • Attempts 1 & 2: 90* seconds on, 10 seconds off
  • Attempts 3-5: 90* seconds on, 5 minutes off
  • 120 seconds in flight
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10
Q

Dry Motoring Duty Cycle Limits

A
  • Attempt 1: 90 seconds on, 5 minutes off
  • Attempts 2-5: 30 seconds on, 5 minutes off
  • After 5 attempts, you can repeat the cycle after a 15 minute cool down.
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11
Q

Maximum Thrust

A

14,200lbs

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12
Q

What are the different ways the engine can be started?

A

APU air start, Crossbleed air start (engine assist), External air source start (air cart or huffer cart), or a windmilling start (airborne only).

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13
Q

Starting and ignition system components

A

ATS (air turbine starter), 2 igniters per engine, and starter control valve

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14
Q

How is the engine start sequence controlled?

A

By the dual-channel FADEC (full authority digital engine control). For air starts the FADEC ignores the “off” position selected on the ignition.

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15
Q

Normal start sequence

A
  1. ) Select engine start
  2. ) N2 rotation begins
  3. ) at 7% N2 ingition begins
  4. ) at 20% N2 fuel flow is introduced (light-off within 5 seconds)
  5. ) N2 rises and oil pressure stays within limits
  6. ) at 50% N2 ignition turns off and the starter cuts off
  7. ) Engine accelerates and reaches normal operating temperature
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16
Q

Thrust reverser system

A
  • Hydraulically actuated
  • FADEC provides interlock protection against inadvertent deployment
  • Idle thrust is commanded if opened in flight
  • For ground use only
  • Idle thrust is commanded while cowls are not totally deployed
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17
Q

Engine FADEC

A
  • ESS (essential electical bus) powered below 50% N2
  • PMA (permanent magnet alternator) powered above 50% N2
  • 1 installed per engine
  • Each FADEC has 2 channels (active and standby)
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18
Q

ATTCS (automatic takeoff thrust control system)

A
  • Controlled by the FADEC
  • Automatically commands maximum thrust reserve (RSV) whenever it’s armed, thrust levers are set to TO/GA, and one of the following occurs
    - DIfference between N1 values greater than 15%
    - One engine failure during takeoff
    - One engine failure during a go-around
    - Windshear detection
  • Automatically armed for normal GA (go-around) mode
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19
Q

N1

A

-LP/fan rotation speed as a percentage of the maximum nominal speed

  • Target (cyan tick): max N1 for selected engine thrust mode
  • Rating (green tick): max N1 allowed for current thrust rating and current operating conditions
  • Request (moving arc): value requested based on TLA (thrust lever angle)
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20
Q

Different Thrust ratings

A 
TO-1 (takeoff) *
TO-1 RSV (takeoff reserve)*
GA (go-around) *
GA-RSV (go-around reserve)*
CON (maximum continuous thrust)
CLB (Max Climb Thrust)
CRZ (Max Cruise Thrust)
Idle
*10 minute time limit
21
Q

Engine Protection

A

During engine start, the FADEC will prevent…

  • Hung starts (inhibited in flight) - compressor not accelerating enough to provide sufficient airflow
  • Hot starts (inhibited in flight) - insufficient airflow to keep ITT under control
  • No light-off - air and fuel but no ignition
22
Q

Engine Overspeed

A
  • If N2 reaches 102% the FADEC will command an engine shutdown
  • In the event of 3 consecutive shutdowns due to an overspeed within 30 seconds, the FADEC will not attempt a relight
23
Q

Over-temperature

A
  • FADEC will prevent fuel flow during a ground start until the ITT (interstage turbine temperature) is at or below 120°C
  • Automatic dry motoring occurs and fuel flow is commanded with ITT below 120°C
24
Q

What is ITT?

A

Interstage turbine temperature. It is the temperature of the exhaust gases between the high-pressure and the low-pressure turbines

25
Q

What is dry motoring?

A

The term dry start motoring means activating the engine starting system without the introduction of fuel or ignition. This is often done to clear unlit fuel from the engine in the event of a no-light-off situation. This procedure can also be used should a hot start or hung start occur to cool the engine down.

26
Q

Describe the N1 spool

A

A single-stage spool and a 4-stage LP turbine

27
Q

Describe the N2 spool

A

a 10-stage compressor (gas generator) and a 2-stage HP turbine

28
Q

How many igniters are there per engine?

A

2

29
Q

How many igniters activate for engine start?

A
  • Ground - 1 igniter (switch in auto)

- Flight - 2 igniters (switch in auto)

30
Q

What happens when the ignition switch is set to OVRD?

A

Activates both igniters on the ground or in flight

31
Q

Can the igniters be turned off during flight?

A

The switch may be moved to the OFF position but the FADEC disregards the command. The OFF position is used for dry motoring on the ground only.

32
Q

What controls the engine?

A

A two-channel FADEC. One channel is active and the other channel remains in standby as a backup.

33
Q

Is only one FADEC channel used every flight?

A

No. They automatically alternate with each engine start

34
Q

What does the cyan line on the N1 gauge represent during approach? When does it appear?

A
  • The minimum N1 for bleed requirements in icing conditions

- Configured for landing < 1200’ RA (when anti-ice is ‘ON’)

35
Q

Does the FADEC provide engine start protection?

A

Only on the ground for a hot start, hung start or no light-off

36
Q

What will the FADEC automatically do in case of a start on the ground?

A

FADEC will not allow FF if ITT >120°C, and will automatically dry motor engine and introduce fuel when ITT <120°C

37
Q

Describe the engine start sequence

A 
Start switch momentarily to START:
7% N2 --> Ignition
20% N2 --> Fuel flow
20% N2+ 5 sec --> Light-off
50% --> N2 Ignition off
50% --> N2 Starter cutout
38
Q

Engine stabilizes

A 
N1 = 27%
ITT = 460°C
N2 = 62%
FF = 550 lbs/hr
Oil Pressure >25 psi
39
Q

What does WML mean on the engine indications?

A

Windmilling engine. The FADEC has detected a flame-out and is attempting an auto re-light, or an assisted start has been commanded

40
Q

What provides underspeed and overspeed protection?

A
  • The FADEC via the FMU

- Approximately 52% N2 and 102% N2 respectively

41
Q

What happens after 3 overspeed detection events?

A

FADEC will not re-light the engine

42
Q

What heats the fuel and cools the engine oil?

A

Fuel/Oil heat exchanger

43
Q

What is ATTCS? What controls it?

A

Automatic Take-off Thrust Control System. It provides max thrust reserve (RSV) according to current rate previously selected via the MCDU. FADEC controlled.

44
Q

What will trigger an ATTCS event?

A
  • N1 difference >15% between engines
  • Engine failure during TOGA
  • Windshear detected
45
Q

When is thrust reverse available?

A

Weight-on-wheels (ground use only)

46
Q

What happens if a thrust reverser inadvertently deploys?

A

FADEC limits respective engine thrust to IDLE

47
Q

What engine thrust rating(s) may only be used for 10 minutes?

A
  • TO-1
  • TO-1 RSV (TL beyond TOGA)
  • GA (two-engine go-around)
  • GA-RSV (one-engine go-around or windshear)
48
Q

Can the FLEX thrust be reduced lower than CLB thrust?

A

No

Mesa Airlines (14 decks)

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