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• Flight crew must turn fuel off
• Observe a 30 second windmill/dry
motor period between start attempts
Selected Abbnnoorrmaall Coonnddiittiioonnss
Second start attempted with both ignitors for 15 seconds
If no lightoff on second attempt
• Start is aborted
• Fuel and ignition turned off
• Dry-motor for 30 seconds to purge the system of fuel
• Flight deck advisory
158
Flight Operations Support
10 September 2005
CFM PROPRIETARY INFORMATION
Subject to restrictions on the cover or first pa ge
Autostart Hot Starts, Start Stalls, Overtemperature Logic
Ground
If a hot start, start stall, or overtemperature
is detected
• Fuel metering valve closes for 6 seconds,
then opens with 7% fuel decrement
• Start fuel flow schedule is reduced at a
total of 21% in three 7% decerements
In-flight
If a hot start, start stall, or
overtemperature is encountered
• The flight crew must abort the
start
• Observe a 30 second
windmill/dry period between
start attempts
If the abnormality occurs after the third increment
• Start is aborted
• Fuel and ignition off
• Flight deck advisory
Selected Abbnnoorrmaall Coonnddiittiioonnss
159
Flight Operations Support
10 September 2005
CFM PROPRIETARY INFORMATION
Subject to restrictions on the cover or first pa ge
CFM56-5 Autostart Miscellaneous Adaptive Logic
Low acceleration
• If the engine is accelerating slowly and the EGT is low, the
FADEC will abort the start on the ground. If in flight, the pilot
must abort the start
• Observe a 30 second windmill/dry motoring period between start
attempts
Low acceleration with reduced fuel flow schedule due to overtemp or
start stall
• If the engine is accelerating slowly and the EGT is low, the fuel
flow schedule is slowly incremented back up to standard
Selected Abbnnoorrmaall Coonnddiittiioonnss
160
Flight Operations Support
10 September 2005
CFM PROPRIETARY INFORMATION
Subject to restrictions on the cover or first pa ge
Low Speed Stall Characteristics: Lightoff Stall
• Engine speed stagnates
immediately after lightoff
• EGT rises rapidly
• Not self-recovering
- Recovery requires FADEC
or flight crew intervention
Seelleecctteedd Abbnnoorrmaall
Idle
N2
Time
Lightoff
Idle
N1
Time
Lightoff
EGT
Time
Lightoff
EGT continues
to rise
FF
Time
Fuel shutoff
open
N2 40% in stall N1 10% in stall
725°C EGT limit
ENG 1 START FAULT
Coonnddiittiioonnss
EGT OVERLIMIT
161
Flight Operations Support
10 September 2005
CFM PROPRIETARY INFORMATION
Subject to restrictions on the cover or first pa ge
• Engine stalls just below idle
• EGT rises rapidly
• Not self-recovering
- Recovery requires FADEC
or flight crew intervention
Idle
N2
Time
Lightoff
Idle
N1
Time
Lightoff
EGT
Time
Lightoff
725°C EGT limit
FF
Time
Fuel shutoff
open
Stall
Stall
Stall
Stall
Low Speed Stall Characteristics: High Sub-idle Stall
ENG 1 START FAULT
Seelleecctteedd Abbnnoorrmaall Coonnddiittiioonnss
HUNG START
162
Flight Operations Support
10 September 2005
CFM PROPRIETARY INFORMATION
Subject to restrictions on the cover or first pa ge
Airlines are fully involved for the engine choice, but crews
are the main contributors for saving the engine
• Pilots are the single most important influence on the engine operation
• 99% of engine operating time is dedicated to the pilot
• Over the last 20 years, engine technology has deeply changed and
determines pilots behaviour in terms of aircraft operations.
• New generations of engines being not any more handled as in the past,
pilot should adapt to new managing.
Pilots need to be fully informed and confident about either
comprehensive overview of optimized engine operation and
development of what is qualified as an Economical Reflex to ensure
proper and longer Time On Wing.
163
Flight Operations Support
10 September 2005
CFM PROPRIETARY INFORMATION
Subject to restrictions on the cover or first pa ge
Airlines are fully involved for the engine choice,...
…But crews are the main contributors for saving the engine...
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CFFM556 Flight Operations Support(24)
