Old 744 Forum

Archived posts

Simfest Crew Event

Page: < 1 2

Author Post
Moderator
Registered: May 2009
Posts: 5140
Hardy Heinlin wrote
If someone can confirm LNAV/VNAV works with any number of inop engines, I'll remove that rule from PSX.

Britjet wrote
Not sure myself. I seem to remember seeing this is the big sim as well once, but can't be sure. Sorry. There appears to be no tech information on this at all. Strange one...
Yet if this was the case you would think it would be in the Boeing QRH...

It seems the QRH doesn't always tell every detail. E.g. for all the probe heat failures it doesn't say that LNAV/VNAV will be inop. Other documents and at least one real-world incident showed that LNAV/VNAV is unavailable when any probe heat power is off.

|-|ardy
Member
Registered: Oct 2014
Posts: 22
Location: London UK
Britjet wrote
Dejan,

I would just like to say on behalf of all of us at Simfest, a very big thank you for your very generous contributions to the charities.

Peter


Peter,

Thank you and the team for putting on a great show for a very serious cause! It is great to see that our hobby can make a difference.

Cheers,

Dejan
Member
Registered: Jun 2015
Posts: 1
The AMM says that LNAV and VNAV engagement is not possible with more than one engine failed.

HTH
Member
Registered: Aug 2014
Posts: 375
Location: Camberley, UK
Excellent! You sound like a useful person to know..
Welcome to the forum!

What's an AMM, may I ask?

Peter
Moderator
Registered: May 2009
Posts: 5140
Aircraft Maintenance Manual :-)
Member
Registered: Aug 2014
Posts: 375
Location: Camberley, UK
I thought as much. Obviously Boeing think there is no need to let the pilots know - you do have to wonder sometimes..:-)
Member
Registered: May 2010
Posts: 843
What part of the aircraft decides that LNAV/VNAV shouldn't engage? Does the FMC stop sending data to the FCCs?

Is the aircraft responding to fuel cutoff lever position? Fuel flow data? RPMs below idle?
Moderator
Registered: May 2009
Posts: 5140
I think the FMC uses the same "engine-running" condition that is included in the validation of the A/T engagement. And that is, if I recall correctly, N2/N3 > 45%, and the FMC gets the N2/N3 data from the EIU.

The FMC decides whether LNAV/VNAV is to be engaged. It can be armed anytime. But the engagement criteria are computed in the FMC.

Page: < 1 2

Old 744 Forum is powered by UseBB 1 Forum Software