Oil Pressure, Dual, Set for 4-Engine Aircraft, Type B-9A USSR According to the Maintenance Interchangeability

According to the Maintenance Interchangeability gude dated Feb 1945

the aircraft is at its maximum allowable airspeed or maximum allowable mach speed

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When rotated to the desired letter by the Sender

Oil Pressure, Dual, Set for 4-Engine Aircraft, Type B-9A USSR According to the Maintenance InterchangeabilityHere is a set of WWII era Type B 9A Dual Oil Pressure Indicators, as used in four engine of the US Army Air Force such as bombers B 17, B 24, and B 29 and transport C 54. These are Bendix Autosyn indicators, which used pressure sensors at the engines which electrically transmitted the signal to these electrical indicators. Both are labeled "AF US ARMY" on their faces. The indicator marked for engines 3 & 4 has a 1944 manufacturing serial number