Air Ministry 'Bigsworth' Chart Board 6B/270

Universally known as 'The Bigsworth chart board', the design dates from around 1918, to aid in the safe use of charts for aerial navigation. It consisted of a wooden board upon which a navigational chart could be placed and held in place by brass retaining clips. The board was square and was available in two sizes, 14 inches or 17 inches with this example being in the larger size, corresponding to 43 cm x 43 cm. The design was conceived by Air Commodore Arthur Wellesley Bigsworth CMG, DSO & Bar, AFC (27 March 1885 – 24 February 1961) who anecdotally is believed to be the aviator who the literary hero 'Biggles' was based on!

These plotting boards were particularly useful in pre and early WWII aircraft, where space was limited and which did not carry a proper Navigators position ; to illustrate this see final photograph attached of a similar board in use in a Blenheim light bomber circa 1939/40, circa the Battle of France. It consisted of pivoted double parallel linking arm that could be adjusted up and down the side of the board and mounted on its other end was a protractor which could be positioned over any point on the chart. The Bigsworth chart board became one of the most convenient aids for plotting and determining courses and finding position and was produced in substantial quantities. It remained in service well into WWII when it was still providing a portable and self-contained navigation station in aeroplanes in which adequate facilities for the Navigator/Observer were still lacking. It continued in use in training aircraft such as the Anson into the early post war years. It was also issued to and used by Fleet Air Arm aircrew in WWII.

Our example remains in above the average issued condition with signs of light service use. To the left edge is a strip of hardwood attached by three brass hinges; we are not entirely clear of the application intended but is is something we have seen before and this may have been to mount the board in a semi fixed position in the navigators position. To the reverse it carries clear stamped nomenclature with a Kings Crown, A. M. property mark (for Air Ministry) and stores reference nos 6B/270, 6B being the code for 'Aircraft Navigation Equipment, Accessories & Spares'. It was manufactured by P. A. C. Ltd. and the serial number confirms it was made in 1940. Below is scratched 'T. W. ', we assume to be the initials of the wartime custodian. The reverse side also carries an oblong green canvas pouch, designed to hold the all important Navigator's pencils. All navigation equipment was closely guarded and cared for by their owners, as the lives of the entire crew depended on his accurate navigation. These instruments are becoming increasingly rare and those that do turn up are mainly the more common 6B/137 version. This would make a great addition to a specialist or general RAF collection and is the first we have been fortunate to obtain for some time and when it is gone it is gone. The flight chart shown is for illustrative purposes only and is not included in the sale. Similar could be supplied at extra cost if required to complete the display.