If there is a failure of motive flow, is it possible to get fuel into the collector tanks?

• A. No, impossible
• B. Yes, gravity feed lines will keep them full
• C. Only by transferring from main tanks
• D. Only with external fuel source

Answer: (B)

When motive flow fails, fuel can still reach the collector tanks if a gravity-feed path exists from the main tanks. The key idea is that gravity provides the driving pressure—the elevation difference between the main tanks (higher) and the collector tanks (lower) pushes fuel through the feed line even without pump pressure. If the gravity-feed line is properly designed and unobstructed, the collector tanks stay full and ready to supply the engines or to receive pump flow again once the issue is resolved. This relies on having fuel in the main tanks above the collectors and on a clear, correctly routed line; if the main tanks are empty or the line is blocked, gravity won’t fill the collectors.