Gravity fuel feeding A320
 

Hi guys. Have a question regarding gravity fuel feeding ceiling. FCOM says that if the flight time above FL300 is less than 30 minutes(fuel non-deaerated), then the gravity fuel feeding ceiling is FL300. However, if you are on an easterly track, where FL300 is not an option, what would your gravity ceiling be? Would it be FL290, or do you have to descend all the way down to FL150? Would appreciate an answer. Thanks in advance!

Where on earth did you pluck FL150 from? Why not FL100?

If the limit is FL300, then any level up to and including FL300 is OK. So, FL290 is within that limit and is fine. Simples ....

Gravity feed ceiling

Flight time above FL 300 less than 30 min - FL 300

Aircraft flight level never exceeded FL 300 - FL 150, or 7 000 ft above takeoff
airport, whichever is higher


If you are on easterly track and flying FL 290 (not crossed FL 300 yet) then ceiling is FL 150 or 7000 ft above takeoff airport.

If on easterly track and flying something like FL 310 (less than 30 min above FL 300) then as ceiling is FL 300. As FL 300 is not available you may go down to FL 290. Here ceiling means the max FL at which gravity feed is possible. No worries if flying below max.

Anyone understand these posts from India?:confused:

Gravity fuel feeding
 

Top Bunk. FCOM says FL 100 for gravity fuel feeding if Jet B fuel is used. Otherwise it is FL 150. Thanks for your reply

Gravity fuel feeding
 

BOAC. This post is with respect to A320 family gravity fuel feeding. Refer PRO-ABN-28 p33/34

gaMBL3. Thanks.

CMpilot1& gaMGle3
As the aircraft climbs the pressure is dropping and the air mixed in the fuel keeps bubbling out much the same way as beer going flat. The time it takes to climb to 30000ft plus 30mts all the air should have gone out but if the aircraft hasn't climbed to 30000ft or hasn't spent 30mts above 30000ft then there can be significant amount of air in the fuel. The only option available is to keep it under higher pressure to prevent the bubbling. That is achieved by descending to 15000ft or 30000ft in the later case. Anything below is even better.

John Smith. FL290 is not FL300. I know that. So, my understanding is that if it were you, you would descent all the way to FL150 or below?

Vilas. Thanks for your reply. The A320 in question that experienced flame out-did it follow the FCOM gravity fuel feeding procedure?

CMpilot1
I had slightly misunderstood your question so I changed the reply. If you never went to 300 then you need to go down to 150 but if you were cruising higher than FL300 then you descent to FL300 if not possible then 290 is fine.

Vilas. Thanks. So your take is FL290 is alright. Copied that..

This must be a darn complicated aircraft what you guys are flying..

On any heading, your limitation is FL300. What FL is available is strictly between you and ATC.

flyingchanges. The definition of ceiling according to dictionary is 'an upper limit'. So, in this case, as long as you don't bust FL300, which is the ceiling(upper limit)you are alright. I have started looking at the gravity ceiling with a different perspective now. Thanks to everyone who contributed.

Sorry for digressing ever so slightly from the subject
I had a discussion with one of my colleagues about the consequences of starting your engines with Fuel pumps OFF. To my surprise he said, its no big deal and that the engines would start normally as they would be fed by gravity( Gravity fuel feed ceiling being FL150) . I have not seen any literature which approves this viewpoint. Has anyone ever accidentally tried switching on the engines without fuel pumps running ?

What is your battery start procedure.

Bkdoss
Engines starts without fuel pumps but there will be ECAM warning. There was an incident when both engines were started with fuel pumps off and ECAM warnings were cleared without even noticing the warning. Crew climbed to FL380 when both engines flamed out. They relit engines and landed back. You do not seem to understand gravity feed limitations. Descent is made to 150 to prevent vapour lock, you do not climb to 150. Lower is better. Read my earlier post.

Vilas
What I meant was that since the ceiling is FL150, and almost all the airports I can think of being at an altitude lower than that, Fuel pumps should feed by gravity . I didn't mean that the aircraft has to climb to FL 150