B777 Thr Ref mode: CLB mode during cruise

[extricate]

Hi there,

Any idea how come during cruise, thrust reference mode on top of the engine display remains CLB mode and not CRZ? Is it due to the system knowing it has step climb coming up?

Thanks

[andmiz]

As far as I was aware it is a company selectable option.

[stilton]

Our 757 and 767’s originally used Crz reference then were changed to Clb.


its so the autothrottles have access to Climb
thrust if needed in cruise flight


Example being you encounter mountain wave activity and start decelerating, why limit
available power when you may need it

[tdracer]

Stilton, at least on the 767, the max climb and max cruise ratings merge above either 30k or 35k (depending on the engine - I believe that's true on most if not all engine regardless of the aircraft). So I suspect it's more emotional than anything else.

[stilton]

Understand that TD, after cruise and climb limit thrust coincide at higher levels you’re not getting any more than a good feeling !

At a lower cruise altitude there would be a difference in available thrust

[extricate]

Just to share, found in FMS Guide:

"In CRUISE, the thrust reference defaults to CLB or CRZ as set in the airlinemodifiable information (AMI) database."

[JammedStab]

Just to share, found in FMS Guide:

"In CRUISE, the thrust reference defaults to CLB or CRZ as set in the airlinemodifiable information (AMI) database."

Correct...the airline decides the default setting. But the pilot can manually select a different setting from the default.

[Papa_Golf]

On other Boeing types (73) it also provides a faster autothrottle response time, is it the same on the 77?

The A/T logic is pretty much the same: faster to recover from an underspeed, slower to retard from an overspeed.

Personally, when I feel the need of having more thrust available I just select CON.