View Full Version : why is ALT button on the A330 FCU on during ALT CRZ phase

28th Jun 2007, 14:01
Hi there

now heres my dilema <>> the ALT button on the A330 type has the same function as the Push to level off button . . . . this replaces the EXPED button which was present on the 19/20/21 ..... first of all two buttons for the same puropse ??? thats my first Q

Second Q is why is this light on during cruise ? coming in from london yesterday that was the topic of conversation for nearly 7 hours but to my surprise didnt have an adequate answer . . . .

all info appreciated


30th Jun 2007, 01:57
I would imagine that the light was on because the alt mode was engaged...just as the light would be illuminated if the AP1/2 or LS pbs were engaged.

Back Seat Driver
30th Jun 2007, 08:19
CLB is a managed mode used to climb towards FCU SEL ALT along VERT F-PLN, taking into account ALT CSTR. Available, only if NAV engaged. The A/THR is in THRUST mode (CLB).
The speed target may either be selected or managed. If managed, SPD CSTR, SPD LIM,and HOLD SPD are taken into account. ALT mode is always armed ; displayed in magenta, if the next level off is predicted at an ALT CSTR ; and in blue, if the next level off is predicted at the FCU-selected altitude.
ALT CRZ is a "Selected" mode. Therefore when the aircraft transitions to cruise flight (ALT CRZ) and the mode changes from Managed climb to (Armed) Selected ALT the ALT p/b light comes on. .... easy.

Dream Land
30th Jun 2007, 11:22
Pardon from a lowly A320 driver, so if I push this button during climb or descent it will level off at that altitude, versus pushing V/S knob? :confused:

30th Jun 2007, 12:12
As Iceman says, it will illuminate when you are at the selected altitude, nothing else. After reading the c/p from fcom, this is what i get from it.

And that means it has nothing to do with the push-to-level-off which levels off instantly.

30th Jun 2007, 13:57

And that means it has nothing to do with the push-to-level-off which levels off instantly

Specific to the A330 this button when pushed will level the aircraft off justlike the Push to Level off button or V/S mind you this is specific to A330 .... not to be confused with the EXPED button on the 320 .

[B]Backseat driver

been to FCOM 4.02.30 P3 Flight guidance principals vertical modes and the function of this button is not mentioned there dude , all it says is that ALT CRZ is a selected mode .

Back Seat Driver
30th Jun 2007, 22:52
The ALT mode maintains a target altitude. This target altitude is either the FCU selected altitude (ALT, ALT CRZ) or an altitude constraint delivered by the Flight Management (ALT CSTR).
The ALT mode arms automatically whenever the aircraft climbs or descends toward the target altitude.
When ALT is armed, the FMA displays the ALT message on its second line :
blue when the target altitude is the FCU selected altitude
magenta if the target altitude is an altitude constraint.
ALT mode engages when :
the difference between present altitude and target altitude becomes less than 40 feet with ALT* engaged.
or when the ALT pushbutton of the FCU is pressed.
The light in the ALT P/B is another indication that Selected ALT mode is engaged, eventhough the aircraft was guided to this altitude by the managed climb mode.
FCOM1 Autoflight / General
ALT puhsbutton
The pilot uses this pushbutton to command an immediate level-off.
(Unlike a Boeing that will return to the altitude that the aircraft was at when the ALT button is pressed, Le Bus will level out at a pre-determined g loading then remain at that altitude).

2nd Jul 2007, 10:29
Thanks BSD that's exactly what I was looking for . . . . .


3rd Jul 2007, 16:26
working along the same lines....

Granted no expedite button on 330, but in the Prog page it will still show distance to TOC if expedite.

My question is with no expedite button, is this simply showing what the a/c could achieve in OPN CLB with NO derate entered??


Back Seat Driver
4th Jul 2007, 07:05
EXPEDITE This field is blank, as long as the climb phase is not active. This field displays this legend when the climb phase is active.
It indicates the time and distance required to reach the altitude displayed in the 2R field, in case of a climb at green dot.(At the current vertical mode.)
For Descent
EXPEDITE If the descent phase is not active this field is blank.
Displays this legend if the descent phase is active.
It indicates the time and distance required to reach the altitude displayed in the 2R field at MMO/VMO speed.