Step Climb Logic

[Antares_16]

Hi, right now there's no step climbs in the FMC, so I've been using VS selecting a 500FPM climb. I've got a few observations/questions on step climb logic/procedure.

The CRZ CLB / CRZ DES modes are backwards. E.g. FL330 select VS 500FPM to FL350 the CRZ page shows CRZ DES not CRZ CLB. When reaching FL350 the CRZ and LEGS pages still show FL330 prompting me to manually key in the new FL.

Will improvements to step climb logic be part of the VNAV rewrite?

Thanks.

 

[Litjan]

5 hours ago, Antares_16 said:

Will improvements to step climb logic be part of the VNAV rewrite?

Yes!

That being said - the behaviour you are seeing and describing on the FMC is correct.

The cruise flight level in the FMC has to be changed by the pilot. Just dialing in something new on the MCP doesn´t do this (this is no Airbus) - in Classics with the ALT INTV button you can use that one to make the entry, but a lot of the older Classics (and the one we model) don´t have that button.

So the correct procedure to do a step climb would be to enter the new cruise flight level on the CRZ page and then select an appropriate vertical mode to climb (or descend) to it.

Cheers, Jan

[Antares_16]

Thanks for clearing that up!

[Litjan]

2 minutes ago, Antares_16 said:

Thanks for clearing that up!

Keep in mind that I observe the calculations for descent not dealing well with a cruise flightlevel change...while they work "ok-ish" if you pretty much follow the planned profile, changing the cruising level (or starting your flightplan while already in the air) does not work well with the descent predictions. I would recommend leaving the cruiseflightlevel alone (you can still fly higher or lower, just don´t "tell" the FMC about it ;-)) for now.

That is something also slated for improvement.

Cheers, Jan