|Object Type:||Signal/Data Processor|
|Object Name:||Air Mileage Unit|
|Manufacturer:||Kelvin & Hughes|
|Year of Manufacture:||circa 1951|
|Location:||Main Object Store|
Air Mileage Unit Mk.4A.
Ref. No. 6B/554
Kelvin & Hughes Ltd.
Serial No. 3265/51
Ref. No. 6B/2577
STI. Inst. 194
In the Air Mileage Unit air pressure from the pitot head is directly balanced against an artificial pressure produced by a motor-driven fan, so that the average speed of the motor provides either the true airspeed at any height within reason, or, if required, the, true air mileage. This is a Mk4 AMU and was fitted to the Canberra and located in the port wheel well. The air mileage is fed into a Position Indicator, placed directly in front of the navigator via a flexible drive, and the latitude and longitude can be derived and displayed on a pair of counters. These counters are periodically re-set manually when definite visual or other fixes are obtained, so that the result at any particular moment is accurate enough for normal navigational purposes. Accuracy was not up to modern GPS standards.