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CFM56-5B vs 7B reverse idle.

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CFM56-5B vs 7B reverse idle.

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Old 24th Apr 2014, 12:00
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CFM56-5B vs 7B reverse idle.

I've noticed on the A320 family, that when idle reverse is selected after touch-down, there is a very brief increase in thrust before the engine settles at flight idle. This doesn't seem to happen on the 737NG.

What is the reason for this?
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Old 24th Apr 2014, 18:03
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It does happen on the 737NG as well; normally up to 43/45% N1 then below 40%. Don't know the reason but I guess is something to do with the inertia of the airflow changing direction rapidly.
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Old 25th Apr 2014, 16:44
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Bleeds operating transiently perhaps?
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Old 25th Apr 2014, 17:44
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On most Boeings, there is a five second time delay on touchdown before going from approach idle to ground idle. Depending on how quickly you get the reversers deployed, you may be seeing that transition...
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Old 26th Apr 2014, 21:13
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You can hear it in this video.

easyJet Landing Madrid Barajas A319 - YouTube
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