CABIN ALT AUTO

[744]

I'm trying to cause an EICAS Alert Message, "CABIN ALT AUTO" (Level) Caution - Aural (Beeper) due to Message Logic - "Both cabin altitude controllers failed or both Outflow Valve Manual switches ON.

I've tried pulling both CB's on P6-4  J 30 & 31 and or J 28 & 29 and or selecting both Outflow Valve Manual switches ON. I can get the lower EICAS Status message to generate "CABIN ALT AUTO (A) or (B) but nothing on the upper EICAS. Their is NO associated Caution or Beeper.

Any thoughts?

Brgds - Steve.

[Hardy Heinlin]

If I pull J28 and J29 the caution appears as expected.

The caution also appears when either outflow valve is in manual control mode.


|-|ardy

[744]

RESOLVED

I've restarted the program, and it now works (CABIN ALT AUTO).............

Thanks Hardy. My apologies for wasting your time. Strange, as I was playing around with this for an hour trying to get it work.

Kind regards, Steve.

[Hardy Heinlin]

Hi all,

I can't remember whether my source was a certain document or an observation on a real 744: I'm wondering whether either of these manual mode conditions is generally true or just aircraft specific?

a) CABIN ALT AUTO appears when any outflow valve is in manual mode.

b) CABIN ALT AUTO appears when both outflow valves are in manual mode.


Regards,

|-|ardy

[John H Watson]

The Maintenance Manual says:

"If both automatic pressure controllers fail, the EICAS caution message CABIN ALT AUTO will be displayed, a caution aural will sound, and the master caution lights will illuminate. These same indications will also appear if the flight crew elects to operate both outflow valves manually."

It's also how I remember it. My training notes were a little more vague.

Cheers
JHW

[Hardy Heinlin]

OK, thanks.

Should the LDG ALT indication on the upper EICAS blank when just one outflow valve is in manual mode? Or should this effect also require both valves to be in manual mode?


Cheers,

|-|ardy

[Hardy Heinlin]

The modification re manual mode is now available in PSX version 10.1.4:

http://aerowinx.com/board/index.php?topic=4191.0


Regards,

|-|ardy

[John H Watson]

Should the LDG ALT indication on the upper EICAS blank when just one outflow valve is in manual mode? Or should this effect also require both valves to be in manual mode?

I wouldn't think one valve would blank the LDG ALT indication. The pressurisation system is quite able to operate on one outflow valve. There is an MEL for it which has no additional operational requirements (other than operating with a maximum of two packs).

[Jeroen Hoppenbrouwers]

I presume the one outflow valve on manual must be closed or nearly closed then? This is not included in the trigger conditions?

[John H Watson]

I presume the one outflow valve on manual must be closed or nearly closed then? This is not included in the trigger conditions?

Closed and CBs pulled. If it can't be closed using the manual setting, it has to be physically closed.