Analogue Air Position Indicator in RAF aircraft

[zenstar1974]

Greetings All,
I am looking for a list of RAF WWII aircraft that used the Analogue Air Position Indicator for lat/long navigation. Does anyone know where I can find this info? Here is a link to a pix of the item and a description:

Analogue Air Position Indicator

Augustus Muir also tells the remarkable story of how Alfred Rose responded to an unexpected request from the Air Ministry, the result of which was that, in a new ‘dispersed’ factory in the village of Saxilby the site for which was found, buildings erected, machinery put in, electricity, water supplies and drainage laid on and roads built, all within little more than 30 weeks – a new navigation instrument,an air position indicator that allowed navigators to read off their positioning degrees and minutes, described as “the most efficient type then in use”, was produced.

This unit is from UK wartime aircraft, and computed an aircraft's latitude and longitude using an entirely mechanical (analogue) process, involving integration, sines and cosines. The current speed and direction were fed in on servo-motors on the right of this photograph. The speed was split mechanically into sine and cosine components for latitude and longitude changes, and integrated to give the current position. The longitude calculation also needed an inverse "cosine" component (longitude changes more quickly nearer the poles proportional to the cosine of the latitude). The mechanical process would, of course, have failed near the north or south poles.



Any info would be greatly appreciated. Thanks.

[Airframes]

Ah Ha! Now I know which instrument you asked me about! Sorry, I must have had brain fade!
The API was certainly fitted to the Lancaster and Halifax, and as far as I know, the Sunderland. I'm not 100% sure, but it was probably also used in RAF Liberators as well as other long range aircraft. In it's various Marks, the API was still used for quite some time after WW2 and, as mentioned in my last reply, the RAF Museum might be able to provide further information.
Cheers,
Terry.

[zenstar1974]

You're the best, Terry! Thanks so much!