Fuel

Question 1

When will the airplane be L mode?

Answer 1

Ballast fuel or as per MEL

Question 2

How does TFM control the CG? When does it start?

Answer 2

Attempts to maintain 2% forward of aft CG limit.

Starts at slat retraction

Question 3

What are the requirements for TFM?

Answer 3

FSC in auto
60k fuel at engine start
No tail tank ballast
At least 2000 lb usable fuel in upper aux with ballast

Question 4

When does TFM terminate normally?

Answer 4

Any main tank reaches 11.5k (to keep tip tanks full)
At 51k total- no more fuel sent aft
Thru FL270- tail fuel sent forward (level off between 270-200 TFM will resume)
Thru FL180 and configured- no more transfer, fuel is trapped

Question 5

When will TFM terminate for abnormal condition?

Answer 5

FSC to manual
Cold fuel recirc fails
Inop hardware or data

Question 6

When does cold fuel recirc work? Does it work in manual?

Answer 6

Only in auto, pumps fuel from inner cell to outer cells
Wing tanks- 6+5=11, not 15
- begins at 6* above freeze temp
- continues until temp climbs 5* or 15 min

Tail tank- 8-5=3

 - within 8* of freeze point- recirc within the tail tank
 - within 5* of freeze point- 1/3 of fuel exchanged with fwd tank
 - within 3* of freeze point- TFM terminated and fuel sent fwd