Question about B-type waypoint

[Will]

I'm on the ground at NZAA, engines are off. I'm putting in the departure. The first waypoint is BROOK, which is to be crossed at or below 4000. I put "4000B" into the FMC. Initial cruise altitude is FL330, no other altitude constraints in the FMC.

Then the FMC says "UNABLE NEXT ALT," and on the VNAV CLB page, it says the error at BROOK will be 1220 LO and 3 LONG.

Why would it give me the error if the constraint is at or below?

[Hardy Heinlin]

I don't know, but the official constraint reads ...

200/4000B2500A

... and that doesn't trigger the message.


Cheers,

|-|ardy

[Will]

I just took off, and by the time the aircraft was in flight, the error message on the CLB page has disappeared.

Just out of curiosity, where are you reading the official constraint? I'm looking at a paper chart from 19 Sept. 2013, and the only constraint I see is at or below 4000 feet.

Thanks for your help!

[Hardy Heinlin]

I selected the BROOK SID on the DEPARTURES page.

[Will]

Got it. NZAA was departing on 23L this morning, and the SID in the FMC doesn't have a 23L option (although the chart, which is from 3 years ago and possibly out of date, does).

[United744]

I don't know, but the official constraint reads ...

200/4000B2500A

... and that doesn't trigger the message.


Cheers,

|-|ardy

That may fix it, but if it was 4000B, what then? Is it an error on the part of the FMC?

[Will]

Just for the sake of clarification, since the FMC doesn't show the BROOK departure as being available for 23L (although my paper chart from September 2013 does), I put the departure manually. There is only one waypoint, BROOK, so it was simple. I put in BROOK, and then entered the crossing restriction of 4000B, and got the error message referenced in the original post (above).