To prevent trapped fuel, do not allow center tank quantity to reach less than ____ pounds without initiating AUX fuel transfer.

• A. 200 lbs
• B. 400 lbs
• C. 600 lbs
• D. 800 lbs

Answer: (B)

Preventing trapped fuel relies on keeping the center tank from getting so low that what remains can become isolated by the fuel lines and gravity. Initiating AUX fuel transfer when the center tank reaches four hundred pounds gives the transfer pump enough head and a continuous feed path to move fuel out of the center tank and into the wings, preventing fuel from becoming trapped. Waiting until the level is much lower increases the risk of insufficient flow and imbalance, while starting transfer much earlier wastes center tank fuel. Therefore four hundred pounds is the right threshold to maintain reliable transfer without unnecessary drain.