744 Left IRU Inop

[Luftis]

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?

[Mac74]

The left IRU provides the v/s data to the GPWS. Just as the left ILS cannot be inoperative (G/S signal -> GPWS).

Mac74

[main_dog]

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!

[Luftis]

That's great, Gentlemen.

Thanks for that!

[NSEU]

Do your 747-400's have Enhanced GPWS (Terrain)? Usually the EGPWS has two IRU inputs.

Rgds
NSEU

[Luftis]

I see some of the later airframes have L and R IRU inputs to the GPWS.

Thanks for the inputs.