October 2020

14 Buckden Roundabout October 2020 RAF Gransden Lodge RAF Gransden Lodge, by Richard Storey, Secretary, Buckden Local History Society Part 1 – Special Duties Located all around Buckden are the remains of old and some current RAF airfields and I ’ m sure volumes can be written on the activities and memories of them all. When I retired I chose RAF Gransden Lodge purely at random to research as a possi- ble talk for the Buckden Local History Society. Unfortunately, Covid - 19 has prevented my visiting the museums and libraries so I am using books and local knowledge for this article. Just inside the south - western border of the old Huntingdon- shire boundary is located RAF Gransden Lodge. The common naming convention has always been to call an RAF station after its nearest village or town. RAF Gransden Lodge, however, was named after a farm – not the one currently standing but one just north of the airfield, now demolished. Built in 1942 and designed originally as a satellite to RAF Tempsford, it was well tucked away in the countryside and ideal for undertaking “ special duties ”. RAF Tempsford was already home to a number of special duty units, and on 8 April 1942 Number 1418 Flight, with its Vickers Wellingtons, was relocated from RAF Tempsford to RAF Grans- den Lodge. Number 1418 Flight was not a bomber Unit but the development Unit for the Gee radio navigation aid, and the role of the Unit was to develop operational techniques so Gee could be used throughout the RAF ’ s bomber force. Up till now the accuracy of RAF bombing crews was woefully below the standard needed for the precision bombing of targets in occu- pied Eastern Europe and the “ top brass ” was desperate for solutions. Gee was originally designed as a blind - landing aid but its range was considerably longer than expected and its use as a naviga- tion aid was quickly recognised. Gee had the potential to pro- duce a fix with accuracy in the order of a few hundred yards at ranges up to about 350 miles (560 km). Three ground stations, a primary and 2 secondaries, of known positions were required to obtain a fix. By plotting the time differences between the receiver and the stations on a special parabolic chart the navi- gator could determine his position. As trials progressed news of its accuracy was reported up the chain of command and soon senior RAF officers came to visit and be taken on demonstration flights. A few days later all this was repeated for representatives from the US and Australian air forces. Later, the accuracy of bombing was improved by the use of Gee H. The aircraft was flown along one ‘ position line ’ and when they intercepted the correct line from a secondary ground station the bomb was dropped. Number 1418 Flight was busy working with other equipment too. In May 1942 work started with another navigation aid, the Air Position Indicator, or API. The API was essentially an ana- logue computer, which having been fed a set of initial coordi- nates, would use the aircraft ’ s airspeed and heading infor- mation to calculate its latitude and longitude. The API only provided an air position to which the wind found by the naviga- tor or the met wind had to be applied to give the aircraft ’ s po- sition over the ground. Number 1418’ s contribution to the war effort was recognised early and by the end of June 1942 it had an increase to its es- tablishment and 2 Handley Page Halifax 4 - engined bombers to add to its fleet of Wellington bombers. Later that month Num- ber 1418 Flight was visited by Sir Henry Tizard, a member of the Air Council and advisor to the Minister of Aircraft Produc- tion. Tizard was a long standing champion on the use of radar and was highly influential on the development of the Chain Home early - warning radar that was so crucial in the Battle of Britain. Tizard ’ s visit was therefore very important, which had further consequences for RAF Gransden Lodge. In July 1942 another independent Unit with its 9 Wellington Bombers came to RAF Gransden Lodge, Number 1474 Flight - an off - shoot from 109 Squadron based at RAF Stradishall. Much like Number 1418 Flight, 1474 Flight was not a bomber Unit; however, this Unit was to undertake the highly secretive role of radar intelligence gathering. Little was actually record- ed of the actual activities but in his book on the story of RAF Gransden Lodge, Chris Sullivan quotes a letter from one of the founder members of Number 1474 Flight, which describes what their job would have entailed. Aircraft from the Flight would join other aircraft from the main bomber force on oper- ational sorties and position themselves in the areas of the high- est radar activity. Using special receivers, operators would scan the spectrum and record essential radar parameters such as frequency, pulse repetition frequencies and signal strength. This valuable information was then used to determine enemy capability and to assist the development of defensive aids and active jammers. Gee Navigation Chart from 1963 Continued overleaf