Tachometer, Chronometric, Type C-11, WWII, Air Corps US Army C-47 see illustration from the B-17G

see illustration from the B-17G Erection and Maintenance Manual in the photos

were one of several generations of radio navigational systems installed in an aircraft such as the heavy bomber B-24 Liberator

48 hr switch indicates 2 x 24-hour time periods

The pressure differential between the impact and the static pressure operates the airspeed indicator

The outer ring of the dial counts up to 10 seconds and the inner dial located at the standard 12:00 position count up to 10 minutes of the 10-second revolutions

Tachometer, Chronometric, Type C-11, WWII, Air Corps US Army C-47 see illustration from the B-17GHere is an example of the WWII era Chronometric (i. e. mechanical) Tachometer, Type 11, as used by single engine aircraft of the Air Corps US Army. According to the US Army Air Force Maintenance Interchangeability Chart dated Feb 1945, the C 11 tachometer was used in fighters P 40 Warhawk (E N), early versions of the P 47 Thunderbolt, and P 51 Mustang, dive bombers A 35 Vengeance and A 36 Apache, and transports UC 61 and UC 64A. This tachometer has a