Engine Flashcards
Draw the Engine System
See Study Guide
What specific engine do we have?
GE CF34-8E5
What type of engine do we have?
Hi-bypass, dual-rotor turbofan (2-spool), axial-flow
What are the 4 engine stages?
Intake, Compression, Ignition, Exhaust
Describe the N2 spool.
10-stage compressor with variable geometry, 2-stage HP turbine
Describe the N1 Spool.
Single-stage fan, 4-stage LP turbine
What is the engine’s max thrust?
14,200 lbs single engine, or 13,000 with both engines
Draw the engine
See notes
Draw the engine fuel system
see study guide or systems manual
Which parts have lubrication systems?
Each engine, IDG?, and the APU have their own independent systems
Starting and Ignition System Components
ATS (Air Turbine Starter), 2 igniters per engine, starter control valve, each engine can be started by APU air, crossbleed air, external air source, or windmilling start
What is the normal engine start sequence?
FADEC controlled, for air starts the FADEC ignores the OFF position selected on the ignition NORMAL SEQUENCE: N2 rotation - 7% N2=Ignition, 20% N2=fuel flow (light off within 5sec), Normal acceleration and oil pressure, 50%N2=ignition off and starter cut-out, normal acceleration and stabilization
Describe the thrust reverser system
hydraulically actuated, FADEC provides interlock protection against inadvertent deployment, Idle thrust commanded if opened in flight, for ground use only, idle thrust reverse is commanded while cowls are not totally deployed
Describe the engine FADEC
ESS powered below 50%N2, PMA powered above 50%N2, 1 for each engine, each FADEC has 2 channels - one active and one standby
Describe the ATTCS Automatic Takeoff Thrust Control System
Controlled by the FADEC, automatically provides max engine thrust (RSV) whenever it’s armed, thrust levers TOGA, and one of the following occur: difference between N1 and N2 values greater than 15%, one engine failure during takeoff, one engine failure during go-around, windshear detection (automatically armed for normal go-around mode)
Describe FLEX takeoff
Reduced thrust for takeoff based on an assumed temperature
Describe N1 indications on EICAS
Target N1 = cyan tick (max N1 for selected engine thrust mode), Rating N1 = green tick (max N1 allowed for current thrust rating and current operating conditions, Request N1 = moving arc (value requested based on TLA (Thrust Lever Angle))
What are the different thrust rating settings available?
TO-1 (Takeoff) (10min max), TO-1 RSV (Takeoff Reserve) (10min max), GA (10min max), GA-RSV (10min max), CON (Max Continuous Thrust), CLB (Max Climb Thrust), CRZ (max cruise), Idle
How is the engine protected during start?
The FADEC will prevent a hung start (inhibited in flight) where the compressor is not accelerating to generate required airflow, prevent a hot start (inhibited in flight) where insufficient airflow to keep ITT under control, prevent a no light-off where air and fuel but no ignition
What happens if the engine overspeeds?
If N2 reaches 102%, the FADEC commands an automatic shutdown, in the event of 3 consecutive shutdowns due to an overspeed within 30 seconds, the FADEC will not attempt a relight
What happens if the engine is over temperature?
The FADEC will prevent fuel flow during ground start until ITT is at or below 120 deg C, automatically dry-motoring occurs and fuel flow is commanded with ITT below 120 deg C
What types of engines are on the aircraft?
2 general electric CF34-8E5 engines that are high-bypass, 2-spool, axial-flow, turbo-fan engines
How much thrust do the engines produce?
13,000-14,200 lbs (ISA)
Describe N1 spool
single-stage fan, 4-stage LP turbine
Describe N2 Spool
10-stage compressor (gas generator), 2-stage HP turbine
How many igniters are there per engine?
2
How many igniters activate for engine start?
Ground = 1 igniter (switch in AUTO), Flight = 2 igniters (switch in AUTO)
What happens when the ignition switch is selected to OVRD?
Activates both igniters on the ground or in flight
Can the igniters be turned off during flight?
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
What controls the engine?
a 2 channel FADEC, one channel is active and the other is in standby as a backup
Is only one FADEC channel used every flight?
No. They automatically alternate with each engine start
What does the cyan line on the N1 gauge represent during approach? When does it appear?
The minimum N1 for bleed requirements in icing conditions, configured for landing less than 1,200’ RA (when anti-ice is ON)
What sources are available for engine starting?
APU, Ground Source (air cart or air bottle), opposite engine (crossfeed start), windmill start
Does the FADEC provide engine start protection?
only on the ground for hot and hung start, also no light-off in air and on the ground?
What will the FADEC automatically do in case of a start on the the ground?
FADEC will not allow FF Fuel Flow if ITT is greater than 120 deg C, FADEC will automatically dry motor engine and introduce fuel with ITT is less than 120 deg C
Describe the engine start sequence
Start switch momentarily to START, 7%N2 Ignition, 20%N2 Fuel Flow, 20%N2 + 5sec Light-Off, 50%N2 Ignition Off, 50%N2 Starter Cutout
The engine stabilizes when:
N1=27%, ITT=460deg C, N2=62%, FF=550lbs/hr, Oil pressure is greater than 25 psi
What does WML mean on the engine indications?
Windmilling engine, the FADEC has detected a flame-out and is attempting an auto re-light or an assisted start has been commanded
What provides underspeed and overspeed protection?
The FADEC via the FMU, approximately 52%N2 and 102%N2 respectively
What happens after 3 overspeed detection events?
FADEC will not re-light the engine
What heats the fuel and cools the engine oil?
Fuel/heat exchanger
What is ATTCS? What controls it?
Automatic takeoff thrust control system, it is controlled by the FADEC, it provides max thrust reserve (RSV) according to current rate previously selected via the MCDU
What will trigger an ATTCS event?
N1 difference greater than 15% between engines, engine failure during TOGA, windshear detection
When is thrust reverse available?
Weight-on-wheels (ground use only)
What happens if a thrust reverser inadvertently deploys?
FADEC limits respective engine thrust to IDLE
What engine thrust ratings are limited to 10minutes? 5min?
10min 1 engine 5min for both
What is FLEX?
Reduced takeoff thrust based on assumed temperature (telling the FADEC that it is warmer than it actually is so it will reduce the thrust)
Can the FLEX thrust be reduced lower than CLB thrust?
No
What is dry motoring? When must dry motoring not be considered?
TBD. Dry motoring cannot be used for a low oil pressure condition
If starting engine via air start cart, which engine is the preferred one to start?
Engine 2 is preferred because of the pneumatic system ducts geometry the pneumatic cart may provide less pneumatic pressure when used to start engine 1
What is the purpose of the engine battery start checklist?
This procedure allows engine starts with batteries as the only electrical power and a pneumatic source (i.e., HPU or APU bleed air).
What powers the FADEC?
The PMA above 50%N2, the electrical system below 50%N2
What controls the Fuel Metering Unit?
The FADEC
Each thrust reverser HALF has how many hydraulic actuators
2
What type of engine is the GE CF34-8E5?
High-bypass 2 spool turbofan
During normal engine start, how is the starter control valve operated?
The FADEC opens and closes the starter control valve SCV automatically.
How many igniters are energized for each engine start?
1 on the ground, 2 in-flight
In what situations is continuous ignition required?
Flight in areas of moderate or heavier turbulence, icing and rain require use of continuous ignition until clear of such areas.
Firewall Thrust
Thrust Levers advanced to forward stop.
Max Thrust
Thrust Levers forward until just below any EICAS redline parameter (N1, N2, ITT) per CFM limitations.
Takeoff Thrust
The minimum N1% required by the airport analysis to meet all performance criteria for a normal Takeoff.
TOGA Thrust
N1 set for Takeoff/Go-Around per performance charts.
MCT Max Continuous Thrust
Thrust set to, but not to exceed, “max continuous” parameters on EICAS for N1, N2, or ITT per CFM limitations (i.e., “top of green” on most restrictive parameter).
(Max Continuous Thrust CON is the highest thrust that does not require maintenance to inspect the engine earlier than planned. It is used in emergency situations and is 12,800lbs. The highest possible thrust is TO-1 RSV or GA RSV, RSV meaning that ATTCS is activated. TO-1 RSV and GA RSV produce 14,200lbs of thrust or 13,000lbs SE)