Turn & Bank Indicator, AN5820-1 WWII US Army Air Force BT-13 A gallon of avgas is

A gallon of avgas is ~ 6lbs

via the pointer in the upper half of the display

thus allowing the needle to return to center

This is a 25 page educational booklet

for example

Turn & Bank Indicator, AN5820-1 WWII US Army Air Force BT-13 A gallon of avgas isThe pneumatically operated, gyroscopic AN5820 1 Turn & Bank Indicator, Bendix part number 1721 2U A2, was used across all aircraft of the US Army Air Force during WWII, such as heavy bombers B 17 and B 24, medium bombers B 25 and B 26, as well as fighters P 38, P 39, P 40, P 47, and P 51, according to the US Army Air Force's Interchangeability Cross Reference Chart dated Feb 1945. In aircraft without a central vacuum filtration system, it would have