Step Climb Procedure?

[JamesZUK10]

Hi Folks,

Thinking from a 744 point of view - During a cruise phase step climb what is your prefered procedure - to use FLCH, let VNAV climb you at THR REF or use VS?? I think I heard somewhere about using VS and a low rate of climb so as not to disturb the PAX too much. Any comments?



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James (EGNM)
PS1 user

[crl]

Hi,
Personally, I will use VS mode when the weight is light instead of high pitch and vs on VNAV for pax comfort. Also not to mention the relevance of using VS in RVSM for obvious reasons.
Other times, hardly FLCH; most of the time we just push the alt knob using VNAV.
Cheers,
CRL :)

[JamesZUK10]

CRL

Thanks fo rthe info - nice to know how its done by the guys & girls at teh frontline!!

Cheers

[whoop-whoop]

If you are only climbing 1000' VNAV will apply full climb thrust as selected on the TMSP. This can lead to a high ROC not desireable if you are in RVSM airspace or if you have TCAS proximate traffic above you. PAX may also find it disconcerting with a short burst of full climb thrust followed by an almost immediate reduction.

VS will only apply enough thrust to maintain the sellected ROC, hence less noise and a more managable climb. However it must be used with CAUTION!!!!

If the rate of climb selected exceeds the amount of thrust available to produce this ROC then the the airspeed will start to reduce. (the autopilot will 'hang on' to ROC selected regardless of airspeed) In a high workload environment the first indication of this may be the stick-shaker as you (in the worst case)approach the stall.

My preferred method for climbs of 1000' is FLCH.

The mechanics of the system will compare the a/c alt with the new alt selected in the MCP alt window, and will apply thrust accordingly. (i.e for 1000' climb it will only apply perhaps half of the available climb thrust)

Therefore you are retaining the benefits of both VNAV and VS.

As with VS - reduced ROC, less noise
As with VNAV - positive speed control.