View Full Version : B777 C1 and C2 demand pumps
felixthecat
19th Nov 2012, 19:02
The manual states that the C1 and C2 demand pumps cannot run together if turned on.
The question is can they run together if they are in auto and system load is high or is it still only 1 at a time?
The clue is in the title 'demand' . Wont come on together on selection as the 'demand' isnt there. in flight they will operate when required.
CharterJake
20th Nov 2012, 09:04
They can operate together in AUTO for take-off. (777 CBT) (Gear retraction, flight control demand, etc.) During landing only one will operate in AUTO. Certain MEL items reflect this when it states that APU has to be running with certain bleed problems to supply bleed air for gear retraction after a go-around.
felixthecat
20th Nov 2012, 12:34
Thanks for the info Charter Jake :)
BVCU it's not really in the title since they are demand pumps when in Auto.... When selected to ON then your telling them to come on despite demand.... And as manual says they can't run together if placed in On position.
gas path
21st Nov 2012, 14:12
The only time they will both run is:
Take-off (a/c in ground mode, take-off flaps selected AND ground speed > 80knots).
Undercarriage retraction.
Autoslat demand.
The reason for them both to run is to ensure enough hyd. press. and flow for the rudder (TAC) in the event of an engine failure.
Both ADP's go off after 10secs. in the air.
CharterJake
23rd Nov 2012, 11:51
I didn't have an answer nearly as accurate as gas path's but, I think he is spot on. The CBT that I have is quite a few years old and outdated as such. Looked again in the MEL but didn't find more info. I wish that Boeing would give us a bit more information but if we don't need to know the we don't need to know...