CDU questions

[Bob Reed]

So I am re learning to program the CDU. I am doing ok but I have a couple issues and I am sure it is because I am missing something when I program it. All works well until I am in decent. My V Speeds go away and the Auto Throttle is hunting. So what am I missing here?

[KyleH]

Hi Bob,

Couple of things to try;
-Do you have a STAR and arrival runway programmed in
-No discontinuities in the LEGS page
-On the PREF page, selected flaps/vref speed (Flaps 30 normal  landing)
- Is there a speed / altitude restriction somewhere in the profile

Also, are you descending in VNAV?
What mode is displayed on the PFD? VNAV speed, or VNAV PROF

Note: I don't use PM so I'm not sure what differences it may have.

[Bob Reed]

Thanks for the reply Kyle. I am not using VNav I am using LVL CNG. You may have hit on the flaps setting in the pref page. I will take a look as I am getting ready to work on the sim now.

[KyleH]

Ok, so with LVL CH, the FMC should have nothing to do with it.
For a descent it should be setting the thrust to idle, and pitching for the speed set in the MCP.

[Bob Reed]

And you are right. During decent everything works as it should it is when I go to APP mode that the trouble starts. I may still have a setting wrong. Been a long time since I set any of this up.

[KyleH]

Ah ok, that makes more sense about the throttles hunting.

Make sure you make a clean ils intercept:
- Angle to runway heading less than 30º and below the glide slope and in level flight

- Should be slowed such that you can extend flaps 5 before turning to intercept the localizer
- press the LOC button first, once you've captured the localizer (shows LOC on the PFD) then select APP mode
- once the ILS triangle is halfway between the top of the scale and on glide slope, select approach speed (Vref + 5), flaps 15 and gear down
- once the aircraft has slowed to below the MAX flaps 30 speed, select flaps 30.