PPRuNe Forums - View Single Post - B747-400 Starter Duty Time Limits (CF6-80)
Old 5th January 2016 | 23:22
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NSEU
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Your book aligns with what Boeing wrote in their Maintenance Manual for the CF6 (a long time ago). It does seems contradictory.

The Boeing Maintenance Manual for the RB211 specifies a normal maximum of 3 minutes letting the N3 return to zero, then a second 3 minute start cycle, then a 1 minute cycle (Then a 30 minute break).
An extended cycle consists of a continuous 5 minute cycle with a 30 minute break.

Perhaps normal implies "ignition". Usually extended starter duty cyles are used for (among other reasons)
1) warming up oil (prior to fuel/ignition)
2) cooling down engine internals after a flight (so that engineers can climb into the back of the engine for maintenance purposes)
3) post-maintenance, for making sure any pooled fuel in the engine is blown out the back, prior to a normal start.
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