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744 Left IRU Inop

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Old 13th May 2011 | 09:41
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From: Upper Deck
744 Left IRU Inop

Anyone wanna give this one a shot?

The 744 can not be dispatched with the Left IRU inoperative; only the Right and Center. Any ideas why the Left is deemed so critical?
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Old 13th May 2011 | 12:11
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From: AMS
The left IRU provides the v/s data to the GPWS. Just as the left ILS cannot be inoperative (G/S signal -> GPWS).

Mac74
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Old 13th May 2011 | 12:21
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From: Krug departure, Merlot transition
The left IRU is hardwired to the GPWS: no IRU-L, no GPWS.

There are probably other systems hard-wired to the left IRU but I'm only certain about the GPWS.

MD

PS Mac74 beat me to it!
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Old 13th May 2011 | 12:35
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From: Upper Deck
That's great, Gentlemen.

Thanks for that!
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Old 14th May 2011 | 01:22
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Do your 747-400's have Enhanced GPWS (Terrain)? Usually the EGPWS has two IRU inputs.

Rgds
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Old 14th May 2011 | 05:59
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From: Upper Deck
I see some of the later airframes have L and R IRU inputs to the GPWS.

Thanks for the inputs.
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