FMC/DU Altitude Readings

[scotfree 0]

Can anyone help me to understand a little better the meaning of some of the altitudes displayed in the FMC/DU in the LEGS page.

 

What I'm trying to understand is the meaning of the A or B suffix used with some altitudes in, for example, a SID departure profile - for example what do the following mean : 3000A, 3000, 3000B.

 

Any guidance would be appreciated.

 

 

Scotfree

[Hirschi 1]

3000 means "at 3000' exactly"

3000A means "3000' or above"

3000B means "below 3000'"

 

But be careful. Approach charts can often provide additional information which rhe FMC or planning software cannot take into account. Sometimes a xxxxA restriction would lead to a very steep descent afterwards while in the charts is written "ATC may clear lower altitudes". But thats for approaches.

For SIDs you must only ensure to stick to this restrictions but the FMC does it for you. Reasons behind may be noise abatement, traffic equalization, airspace management/restricitions or geographical reasons.

 

Regards

Hirschi

[Mickel 42]

Tutorial 1 and in particular Tutorial 2 have several useful bits about using and understanding the FMC.

[scotfree 0]

Many thanks Hirchi and Mickel for the information and advice. I now have a better understanding of SID's and STAR's and their limitations.

 

Scotfree