Air Ministry Inclinometer Reference 6A/389
Officially called a ' Fore-and-Aft Level, Type B' these were first described in the 1934 edition of AP1275. The type 'B' variant superseded the Type 'A' which was used on RNAS aircraft during the 1914-18 war. This updated version was significantly lighter and was used in a variety of RAF aircraft of the 1930's, including the DH82 Tiger Moth, Bristol Bulldog, Gloucester Gladiator and many more. It remained in service until the more sophisticated blind flying instruments panels were introduced which included an Artificial Horizon. This example is in really crisp original condition with a white oblong dial graduated clearly from zero in the centre indicating flat and level flight. It then caries a scale going up to 20 degrees in a climb and 20 degrees in a dive so effectively the instrument gave a visual indication of the angle of the aircraft through the air and effectively worked in the same way as a spirit level, but in the vertical plane. The 'A' version of instrument originally contained a red dye but this was found prone to fading so was uprated with a black dye on later models. The dye is still present in this example and whilst we can't warrant its accuracy it seems to work as was intended back in the 1930's. It is made from what looks like Bakelite and is fully stamped with REF. No. 6A/389, a Kings Crown, A.M. and a serial number 145752. On the reverse of the dial is an ink manufacturers or inspectors stamp ; we are unsure who made this example but the main makers were either Short & Maison or Reid & Sigrist Ltd. The dial measures 5.5" (14 cm).These instruments are becoming increasingly difficult to find now so grab the opportunity whilst it is available. It is the first one of the kind we have had in for a considerable time and when it is gone it is gone!