When an aircraft is positioned for weighing on scales located under each landing gear wheel, which of the following may cause erroneous scale readings?

• A. Parking brakes set.
• B. Wheels inflated to the wrong pressure.
• C. Tire wear abnormal.
• D. Crew wearing heavy clothing.

Answer: (A)

The readings from the scales rely on each gear transferring the full vertical load of the aircraft to its respective scale when the aircraft is properly positioned for weighing. If the parking brakes are set, the wheels are locked and a braking torque is applied to the wheel hub. That braking action changes how the weight is transmitted through the wheel/gear to the scale, effectively perturbing the load path and causing the scale to read a value that does not represent the true vertical load on that gear. In other words, the brake hardware can introduce forces that skew the measurement, so to obtain accurate results the brakes should be released and the aircraft allowed to settle on the scales.

Wheels inflated to the wrong pressure, tire wear, or crew clothing are far less likely to produce the immediate, direct interference with the load path that a locked brake does during weighing. They can influence surface contact or redistribution of load in other ways, but the most direct cause of erroneous scale readings in this weighing setup is the parking brakes being set.