Fuel exclusively stored in the fuselage reduces aircraft performance, crash safety, and practicality. The FAA and EASA have regulations for fuel storage, but additional factors ultimately determine where fuel is stored within aircraft designs.
Fuel stored in the wing is generally safer in crash events than fuel stored near the passenger cabin. Even for crash events where the plane doesn’t catch on fire, fuel is best kept off and away from passengers. Fire kept away from the cabin (in the wings) gives passengers time to escape to safety.
Surprisingly, where fuel is stored within an aircraft can drastically effect the structural weight of the aircraft. This is due to a structural effect called span loading.
Imagine yourself walking onto a steadily thinning sheet of ice on a lake. Your steps start to crack the ice.
Quick, lay down flat and spread your weight out before you fall through. The thin ice can support your weight as long as you keep your weight spread out.
In this silly example, the ice thickness represents the thickness of structural aluminum or carbon fiber in a wing. The more evenly distributed the weight of the fuel, engines, components, and payload is across the wing, the thinner the “ice” – the aluminum in the wing can be to support the same weight.
Less aluminum equals less structural weight – resulting in lower cost, better efficiency, and higher aircraft performance. Fuel stored in the wing helps accomplish that.
Long range aircraft, like airliners, carry a large portion of their total weight as fuel – over 12%. Most of the fuel weight is burned up in flight. For huge airliners, that can be hundreds of thousands of pounds of fuel burned in one flight.
Aircraft simultaneously need their Center of Gravity (CG) tightly controlled and to be near and slightly ahead of the aerodynamic center of the airplane. The CG is typically located near the wing. Slight movements in the CG – inches – have drastic impacts on aircraft stability and control. As a plane burns its fuel during flight, the CG needs to stay within a small range – the entire time.
Fuel stored in the wings is perfectly suited to keep the CG within limits as the weight of the plane reduces by tons.
Where do those checked bags go? Fuel in the fuselage limits how much baggage, cargo, cabin, and internal volume is available. Fuel is the perfect candidate to be put in the wings. It’s a liquid – which occupies odd geometries and narrow passages with ease. Fuel stored in the wings expands the amount of volume open for baggage as well as for passengers.
Fuel stored in the wings enables better safety, efficiency, performance, and affordability. With so many benefits to fuel storage in the wings, it would irresponsible to not consider it.
Author – Mason Bivens (Aerospace engineer and commercial pilot)
