Flameouts have occurred as low as which altitude in a gravity-fed fuel system?

Flameouts have occurred as low as which altitude in a gravity-fed fuel system?

• A. 7,000 feet
• B. 5,000 feet
• C. 9,000 feet
• D. 11,000 feet

Answer: (A)

In a gravity-fed fuel system, fuel moves to the engine purely by gravity, with no pump to boost pressure. That means the engine can only be fed as long as the liquid fuel is continuously covering the pickup and maintaining a steady head pressure. If the fuel starts to vaporize or form air pockets in the line, or if the fuel sloshes away from the pickup, fuel flow can be interrupted and the engine can flame out. This fragility shows up even at relatively moderate altitudes because lower ambient pressure and possible fuel heating increase the tendency for vapor formation and fuel starvation in the feed line. Real-world experience has shown flameouts occurring down to around seven thousand feet in gravity-fed systems, making that level the best-supported threshold among the options. Higher altitudes can also pose risk if the head pressure continues to drop or vapor lock develops, but the observation at about seven thousand feet best fits the common scenario described.

In a gravity-fed fuel system, fuel moves to the engine purely by gravity, with no pump to boost pressure. That means the engine can only be fed as long as the liquid fuel is continuously covering the pickup and maintaining a steady head pressure. If the fuel starts to vaporize or form air pockets in the line, or if the fuel sloshes away from the pickup, fuel flow can be interrupted and the engine can flame out.

This fragility shows up even at relatively moderate altitudes because lower ambient pressure and possible fuel heating increase the tendency for vapor formation and fuel starvation in the feed line. Real-world experience has shown flameouts occurring down to around seven thousand feet in gravity-fed systems, making that level the best-supported threshold among the options. Higher altitudes can also pose risk if the head pressure continues to drop or vapor lock develops, but the observation at about seven thousand feet best fits the common scenario described.