Tachometer, Air Ministry, Mk IA, 6C/223 (Serial 134/42) C-43

Tachometer, Air Ministry, Mk IA, 6C/223 (Serial 134/42) C-43Here is a WWII era Mk IA chronometric (mechanical) tachometer of the British Royal Air Force, Air Ministry stores reference number 6C 223, serial number 134 42. This tachometer measures from 500 to 5000 RPM, and has a totalizing counter which measures up to the millions of RPM. The "6C" prefix in the stores reference number indicates that this tachometer was intended as a test instrument, and the "42" in the serial number indicates a manufacturing

as indicated in the small window at the 3:00 position

the drift angle is determined by reading the location of the pointer on the base's scale

color-tabbed sections:

and appears in the design of the 1940-50's GE position indicators

The two auxiliary pointers located behind the main pointer rotate to indicate the maximum negative or positive G's experienced by the aircraft until reset by pushing the knob inward

such as the P-38 Lightning

The operating limits for the aircraft in which it was installed are marked in red & green tape adhered to the outside glass

25 inches diameter by 5 inches deep

and then from 2500-3500 as the pointer continues past the 12 o'clock position and read along the inner scale to the 4 o'clock position

The pointers are marked L and R

but the compensating module has been removed on this compass

this indicator was being used in late models of medium bomber B-26 Marauder