It didn’t take long for the British infantry units equipped with the ‘2 pounder’ (40mm) anti-tank gun in the Western Desert to realize that they were being out-gunned and out-classed by the opposing German and Italian units. Introduced in the 1930s, when the standard tank gun was in the same class (the United States used a 37mm gun), the 40mm gun was fast becoming obsolete. The answer was a new, bigger gun, the Ordnance QF 6-pounder.
This was a much better anti-tank weapon of 57mm bore, and was able to defeat most Axis armour, if the correct tactics were employed. This gun was rushed to North Africa, just in time to make a splendid showing in the highly significant Battle of El Alamein (23rd Oct – 11th November, 1942) which ended in a resounding victory for the British and Commonwealth forces.
Use of the QF 6-pounder spread; the United States Army used the weapon as the 57mm Gun M1, and built over 15,000 (others were built in South Africa and Canada). The Royal Navy found a use for a version on their Fairmile ‘D’ Motor Torpedo Boats and the SGBs, or Steam Gun Boats, of the RN’s Coastal Forces. The RAF were not far behind; the Hawker Hurricane IId had given valiant service in the anti-armour role (2 x Vickers Type ‘S’ 40mm guns) during the North African campaign, but by 1943 was a bit long in the tooth. Initially, it was thought that the De Havilland DH.98 Mosquito, carrying a special version of the 6-pounder complete with an automatic ammunition feed designed by the Molins Company of Peterborough (a firm more used to making cigarette-making machinery) would take on these duties.
In 1943, a standard Mosquito FB.VI, the most-produced fighter-bomber version, was removed from the production line and heavily modified. The space which would have been occupied by the 4 x 20mm British Hispano cannon was now filled with the Molins-modified 6-pounder and its auto feed system containing 25 rounds of HE ammunition with an armour-piercing nose; the big gun was offset from the centreline of the Mosquito by 4º, to accommodate the stock of large shells. The 4 x .303 Browning machineguns above the cannon bay were left in place. The resultant variant of the Mosquito was officially called the FB.XVIII, and made its first flight on the 8th June, 1943. However, it was usually refered to as the ‘Tsetse’, after the vicious biting fly of Africa which carries the parasite for trypanosomiasis, or ‘sleeping sickness’. Singularly appropriate, I think! The prototype aircraft was given the RAF serial ‘HJ732/G’, the ‘G’ signifying that this was an aircraft which was so secret that it was to be kept under armed guard at all times! The ‘Tsetse’ was always a ‘rara avis’ with a grand total of only 18 being built. This was basically due to a dispute between the ‘big gun’ faction in the RAF and the ‘rocket projectile’ enthusiasts. Ultimately, the RP fans won the argument, and the FB.XVIII remained a footnote to the Mosquito story.
Operated in small numbers by No. 248, 254 Squadrons, and a Special Detachment of No. 618 Squadron, as part of the Portreath and Banff Strike Wings, the FB.XVIIIs were sent out in twos and threes as part of mixed strike packages, hunting surface vessels and German naval units amongst the Norwegian fjords, and across the wide waters of the Bay of Biscay. Diving from 5,000ft at a 30º angle, the Tsetse would unleash bursts of 3 or 4 shells at around one a second. The 57mm shell, moving at 2,950ft/sec, would do fearsome damage to any vessel. ‘Up-gunned’ U-Boats were fighting it out on the surface against Coastal Command aircraft at this stage, but stood little chance. The Mossie was carrying 900lbs of extra armour-plate (cabin floor, engines, gun bays, fuel tanks, etc) as well as strengthened flaps and fuselage doors, and sank many vessels. On 25th March, 1944, Flying Officer D. Turner and Flying Officer D. Curtis, along with another Tsetse, sank U-976, a Type VIIC U-Boat, near St. Nazaire, France. In June, U-821 was attacked so hard that her crew abandoned her. It wasn’t all hard work though; on 10th March during a shipping attack by FB.VI and FB.XVIII aircraft, around eight Ju 88 fighters tried to interfere. The FB.VIs shot down two, and one then crossed in front of a Tsetse flown by Squadron Leader Tony Phillips. The pilot of the Ju 88 had what can only be described as a real ‘Oh dear!’ moment when he was hit by a volley of no less than FOUR 57mm shells (one of which neatly removed an engine from the wing). The remains of the Ju 88 – and there cannot have been a lot – fell into the sea!
A full-page advertisement in a wartime issue of ’Flight’, showed a smiling RAF NCO holding a 6-pounder shell in front of an FB.XVIII, over the legend ‘The Flying Field Gun’, but it was not to be. Even a laudatory statement from Air Marshall Sir Sholto Douglas, Commander-in-Chief of RAF Coastal Command, (later Marshal of the Royal Air Force, William Sholto Douglas, 1st Baron Douglas of Kirtleside, GCB, MC, DFC) in the De Havilland company newsletter for May/July 1944, called the ‘Mosquito News Report’, was of no use. The Air Staff turned his request for more FB.XVIIIs down; the ‘rocket establishment’ had won. At the end of the war, the rarest Mosquito type to see squadron service was quietly scrapped. A shame, for it was a potent weapon. The 6-pounder, seen here in front of a Mosquito B.35 at the Royal Air Force Museum, Cosford, is all that remains of a glorious experiment.
If you would wish to see a Mosquito back in UK skies, I would ask you to consider supporting the ‘Peoples Mosquito Trust', a group who are intent on rebuilding a Mosquito to flight status. Links to their website and other links are given below. I would urge you all to visit and join in the fun!