elect PACK 1 ON after CLB thrust reduction
Select PACK 2 ON after flaps retraction
Bleeds effect
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147
Flight Operations Support
10 September 2005
CFM PROPRIETARY INFORMATION
Subject to restrictions on the cover or first pa ge
The thrust decrement is frozen by the FADEC when:
• The aircraft is on the ground
• Thrust levers at or above MCT/FLX
• The configuration is latched in flight until the thrust levers are set to CL
Bleed Failure at T/O
In case of a failure, the EGT may increase but the takeoff thrust remains.
The thrust decrement is frozen by the FADEC during the takeoff. This avoids:
• Thrust fluctuations in case of an intermittent bleed failure.
• Thrust loss in case of a bleed failure (I.e. APU auto shutdown, with APU BLEED ON).
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150
Flight Operations Support
10 September 2005
CFM PROPRIETARY INFORMATION
Subject to restrictions on the cover or first pa ge
Bleed selection for takeoff has an impact on the takeoff performance.
PACKS OFF or APU BLEED ON can be used:
• to improve performance when TOGA is used
• to reduce EGT when FLEX thrust is used:
- This will increase the engine’s life and decrease Maintenance
costs
- This will help prevent EGT exceedances on engines with reduced
EGT margins.
Zone Controller and FADEC protection logics ensure a safe takeoff in
case of abnormal bleed :
• no engine thrust asymmetry.
• no thrust loss after takeoff power application.
Bleeds effect Summary
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151
Flight Operations Support
10 September 2005
CFM PROPRIETARY INFORMATION
Subject to restrictions on the cover or first pa ge
From an engine standpoint, rolling takeoff is preferred
• Less FOD potential on contaminated runways
• Inlet vortex likely if takeoff N1 set below 30 KIAS
• Less potential for engine instability or stall during crosswind/tailwind
conditions
N1 thrust management
• Engine control computes command N1 for max or reduced thrust
• Throttle “stand up” prior to full thrust (minimizes uneven acceleration)
• Pilot sets throttle for full thrust or reduced thrust
• Aircraft/engine controls maintain N1 at command value
Takeoff
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152
Flight Operations Support
10 September 2005
CFM PROPRIETARY INFORMATION
Subject to restrictions on the cover or first pa ge
Cruise
Avoid unnecessary use of ignition
• Conserves ignitor plug life
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Cruise Operation in icing conditions
Only inlet cowl is anti-iced:
use ENG ANTI-ICE per FCOM
100
90
80
70
60
50
40
30
20
10
0
10
9
8
7
6
5
4
3
2
1
0
0 20 40 60 80 100 120 140 160 180
%N1 Fan vibes
(units)
Time (seconds)
Ice shed
point
Fan/spinner ice manifested as vibration as ice
partially sheds
• If vibration encountered in icing conditions or as a preventive measure when
operating at 70% N1 or below in moderate to severe icing conditions, perform the
following procedure (1 engine at a time):
- Reduce N1 to 45%
- Increase N1 to 80% minimum then reduce as required for flight conditions
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