Ferry tanks

Flying a Cirrus SR22 to China or a Cessna 172 to Europe, for example, typically requires adding a ferry tank, filling it with avgas, and plumbing it into the existing fuel system. Many ferry tanks are portable, but the FAA must approve each installation, and pilots are required to thoroughly test them to ensure they work properly before heading over the horizon.

Especially long trips may require additional FAA permits to fly above the airplane’s maximum gross weight.

Ferry tanks are usually made of metal and placed in the fuselage. Others are collapsible rubber bladders. Whatever the material, ferry tanks must be properly secured, resist leaking or rupturing, and be vented or pressurized so that fuel stored inside the tanks can drain into the aircraft fuel system and flow to the engine.

Ferry pilots typically start long trips by using fuel in the airplane’s permanent fuel tanks first. Then there’s a moment of truth in which they switch to the ferry tank. Doing so usually refills the permanent fuel tanks and allows the engine to continue operating normally.

On rare occasions, however, ferry tanks have failed during oceanic crossings, leading pilots to ditch far offshore or improvise under stress to get fuel flowing properly again. Ferry tanks are designed to be sturdy, mechanically simple, and reliable because the consequences of failure can be so severe.

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