Cessna asymmetric fuel system: (hence the wing wagging)
Asymmetric fuel delivery
Asymmetric (uneven) fuel delivery was a well known phenomenon in single engine Cessna aircraft. The Cessna Pilots Association, (CPA) Santa Maria CA, highlighted the issue in a 1993 Tech Note #003 Uneven Fuel Feeding in Single Engine Cessnas.
The CPA describe the problem as being common on the 150/152, 172 and pre-1979 182 aircraft models.
The reason for asymmetric fuel delivery was attributed to the design of the fuel venting system, which allowed for a greater head of pressure in the left tank than the right, promoting faster delivery of fuel from the left tank. The CPA advised that due to the long and shallow design of the fuel tanks, their sensitivity to tank/ head pressure was increased. While the design incorporated a crossover vent line between the tanks, equalisation of head pressure could not be assured. The CPA highlighted that when the fuel tanks were filled above a certain level (typically half full), there was also the capability of fuel sloshing from the left tank to the right tank through the crossover vent line. That action resulted in the right tank retaining a higher level of fuel than the left, while still supplying the engine.
The Cessnas I flew back in the day all had a wooden dip stick in the shape of a T that we used to double check the fuel level in the tanks.
Like this!
