ALT & SPD INTV Buttons?

[BAe 146-100]

Hi,

I was wondering what the ALT & SPD INTV buttons on the B737 do? Why do most airlines have these two buttons covered up by plates?

Cheers
BAe 146

[Desert Dingo]

There is a listing of all the FMS updates at The 737 Technical Site
The bit you are looking for is in update 6:

Update 6.0 - 10 Jun 1992 - Ref 737-SL-34-93

1. Speed Intervention
Allows the flight crew to override the FMC target speed without disengaging vertical navigation (VNAV) through the use of the mode control panel (MCP) speed intervention on/off pushbutton, the MCP indicated airspeed/mach select pushbutton and the MCP speed select knob.
2. Altitude Intervention
Using the MCP altitude select knob and the MCP altitude intervention pushbutton, the flight crew has the capability to:
a. Delete the next altitude constraint while in climb or descent.
b. Increase the cruise altitude while in climb or cruise.
c. Initiate either a step climb or a transition to descent phase while in cruise phase.

Probably most airlines do not think it worth the cost for the benefit gained - just make the pilots work a bit harder and make their changes using the CDU keypad.

[BAe 146-100]

Thanks for that, now I know exactly what they are.

Ryanair have ALT & SPD INTV fitted on their B738s. Possibly for time saving purposes I would have thought?

http://www.airliners.net/open.file/704614/L/

Kind Regards
BAe 146

[Kit d'Rection KG]

Now, I wonder, are the Irish Favourite a 'standard Boeing' operator?