RAF Height and Airspeed Computor Mk II

A handheld circular aluminium bodied height and airspeed computor (sic) is made from three concentric, decreasing diameter calibrated discs laid on top of each other and secured by a central split pin. There are two additional quarter discs with screw adjusters for setting temperature and ground pressure. The instrument features rotating metal discs used to set the ground barometric pressure, temperature, indicated height and airspeed and were used in conjunction with 'I. C. A. N. ' isothermic calibrated altimeters to calculate speed, time and distance travelled. Manufactured by the quality instrument makers Henry Hughes and Sons, London it is marked with serial number 9095/39, indicating a production date of 1939. The back of the instrument also carryie a crisp Air Ministry property mark.

A similar Mk I dead-reckoning flight computer dating from 1940 is illustrated on page 113 of Mick Prodger's excellent 'Luftwaffe V RAF Flight Equipment' reference book, where he confirms these instruments were most commonly carried by pilots of single engine fighter aircraft, so like the Luftwaffe DR2 flight computer we have also just listed, this could well have served in the Battle of Britain. The Hurricane had a canvas pouch fitted on the starboard side of the cockpit to hold it securely in place, so it was always to hand when needed (see final photograph attached). The instrument remains in very good original condition and would appear to be in good working order, with signs of just light service use. Measures 5.75" diameter (14.5 cm).