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present a problem for start
Expect warmer starts with high residual EGT
Crosswinds
• No significant impact on start characteristics
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131
Flight Operations Support
10 September 2005
CFM PROPRIETARY INFORMATION
Subject to restrictions on the 6837H 0103A cover or first pa ge
Start up procedure
Faster/colder ground starts on the SAC Engine
Average start up time SAC 30 s
DAC 1 mn
SAC Cross bleed start procedure with the DAC engine
(The operational case is when you start first the DAC engine, then the SAC engine)
Thrust has to be increased at 30% N1 on the DAC engine before lauching the start on the SAC, otherwise you
could stay at idle or even have face a roll back on the DAC engine and not be able to start the SAC.
Ground Idle
• Higher EGT & higher fuel flow (25% at idle )can be noticed on the DAC engine.
• Lower N1 and Higher N2 at ground idle and Lower N1 and N2 at min idle in flight on the SAC Engine
• Depending on engine age &/or type &/or bleed supply, the range of EGT
difference can reach, basically, from 30°– 40°to 200°-250°C ** on the DAC engine.
• Quicker acceleration in N1 speed range from idle to 50% N1 on the SAC Engine
Start SAC/DAC intermix
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132
Flight Operations Support
10 September 2005
CFM PROPRIETARY INFORMATION
Subject to restrictions on the cover or first pa ge
Pilot positions mode select switch to IGN/START
Pilot selects MASTER LEVER ON
• Start valve opens*
• APU speed (if used) increases
• Pack valves close
• Ignition comes on at 16% N2*
• Fuel comes on at 22% N2*
• At 50% N2 starter valve is commanded closed and ignition is turned off*
• APU (if used) speed reduces and pack valves open
Ground Autostart Sequence
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*The FADEC initiates automatic sequence
FADEC Full authority for Start Protection up to Idle on:
• EGT & Starter engagement time
• Any engine abnormal start
• The starter re-engagement
133
Flight Operations Support
10 September 2005
CFM PROPRIETARY INFORMATION
Subject to restrictions on the cover or first pa ge
Ground Manual Start Sequence
Pilot selects mode selector switch to IGN/START
Pilot depresses MANUAL START PB
• Start valve opens (25 psi desirable)
• APU speed increases
• Pack valve close
Pilot selects MASTER SWITCH ON at 22% N2 or maximum achievable N2
(minimum 20% N2)
• Dual ignition and fuel flow
• At 50% N2 starter valve is commanded closed and ignition is turned off
Start protection during Ground Manual Start
FADEC shall provide faults to FWC
LIMITED AUTHORITY TO ABORT THE STARTING SEQUENCE ONLY FOR EGT
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134
Flight Operations Support
10 September 2005
CFM PROPRIETARY INFORMATION
Subject to restrictions on the cover or first pa ge
In-flight Autostart Sequence
Same as ground procedure
FADEC selects starter assisted start if N2 is below windmill start threshold
• 12% N2 at or below 20,000 ft
• 15% N2 above 20,000 ft
Starter assisted
• Starter valve opens
• Dual igniters come on immediately
• Fuel comes on at 15%
• At 50% N2, starter valve is commanded closed and ignition is turned off
Windmill: Dual ignition comes on slightly before fuel flow
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Start protection during Inflight Autostart
FADEC shall provide faults to FWC
NO AUTHORITY TO ABORT THE STARTING SEQUENCE
Start malfunction advisories are operative, but pilot must abort the start if malfunction occurs
IN-FLIGHT RELIGHT ENVELOPE SAC/DAC Intermix
DAC envelope (More restrictive) must be applied in
intermix
•The DAC Relight envelope (20 KFt) is lower than the
SAC (27.0 KFt). In intermix
configuration, DAC envelope must be applied.
135
Flight Operations Support
10 September 2005
CFM PROPRIETARY INFORMATION
Subject to restrictions on the cover or first pa ge
In-flight Manual Start Sequence
In the manual mode a starter assisted start is commanded through FADEC
Pilot positions mode select switch to IGN/START
Pilot depresses MANUAL START PB
Pilot selects MASTER SWITCH ON at 15% N2 or maximumachievable N2
• Dual ignition and fuel flow
• At 50% N2 starter valve is commanded closed and ignition is turned off
• APU speed decreases and pack valves open (30 second delay)
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CFFM556 Flight Operations Support(19)
