The Tellier T.6, also known as the Tellier TC.6 was a French flying boat produced for maritime patrol during World War I.[1] It was a development of the Tellier T.3 with added cannon armament[1] [2] (Hence the C in the TC version of the designation)[3] [4] and a lengthened fuselage.[2] Fifty-five examples served with the French Navy in the Atlantic and Mediterranean[1] [2] from 1917 until the end of the war.[2] After the armistice, some examples served as training aircraft until 1922.
Like the T.2 and T.3 from which it was developed, the T.6 was a two-and-a-half bay, equal-span, un-staggered biplane flying boat.[3] The lower wings were mounted to the top of the fuselage sides, and wire bracing was used between the wings, and between the wings and the fuselage.[3] It had a conventional tail, also braced with wire.[3] Outrigger floats were carried underneath the tips of the lower wings.[3] A single engine was mounted in the interplane gap, driving a pusher propeller.[3]
The T.6's cannon armament consisted of a single 47frac=4NaNfrac=4 Hotchkiss model 1885 naval gun carried on a transverse mount in an open position at the bow.[2] This mounting allowed for the cannon to be depressed up to 55°.[5] The open cockpit for the pilot was aft of this, just in front of the wing cellule.[3]
The hull was covered in plywood, and the wings and tail surfaces in canvas.[3]
The development of the T.6 was a response to a very specific military problem.[3] By 1917, German submarines posed a threat to Allied ships in several parts of the Atlantic and Mediterranean. The small bombs carried by the flying boats deployed against them were only effective with a direct hit, but the bomb sights of the time were not accurate enough to make this likely.[2] Cannon armament seemed to offer a solution to this problem,[2] and in Spring 1917, the Centre d'Aéronautique Maritime de Camaret fitted a Donnet-Denhaut flying boat with a 37frac=2NaNfrac=2 cannon for trials.[5] This aircraft proved underpowered for this use, so the Navy requested Tellier to modify a T.3 to carry an even larger gun.[5]
The 47-mm cannon, its gunner, plus twenty or thirty rounds of ammunition added around 700kg (1,500lb) to the bow, which substantially altered the aircraft's centre of gravity.[2] Tellier compensated for this by adding a 0.87m (02.85feet) stretch to the rear fuselage.[2] [5] The fuselage interior was also reinforced to better withstand the cannon recoil.[5] Even so, the T.6 inherited a weak structure from the T.3,[2] and required further strengthening when the type entered service.[2] [4]
The prototype T.6 was tested at Saint-Raphaël for its air- and seaworthiness and for its ability to fire its cannon in flight.[5] The type was accepted for military service, and the Navy placed an order for 85 T.6s in July 1917, together with an extra 20 T.3s.[5] Total orders eventually reached 110 aircraft,[3] but only 55 were delivered by the armistice.[2] [3]
T.6s served alongside T.3s and other flying boats at Saint-Raphaël, Bayonne, Brest-Camaret, Cherbourg, Lorient, and throughout the Mediterranean, including Africa, Corsica, Italy and Greece.[4] Squadron records of the time generally refer to aircraft by their identification number within the squadron, but since these squadrons operated a mixture of types, it is difficult now to be certain which types of flying boats participated in which actions.[6]
In operational use, the T.6 proved less effective than hoped.[7] The cannon proved difficult to aim, its sights were inadequate, and gunners were not well-enough trained to use the weapon.[7] In February 1918, the Centre d'aviation maritime de Cherbourg recommended that a "bomb-launcher" for 52kg (115lb) bombs be fitted to the T.6s, and that the aircraft take off with only 60% of their normal fuel loads to offset the weight penalty.[7] Such launchers were fitted to newly-built T.6s from August 1918 onwards, but the armament problem had not been resolved by the armistice..[7]
After the war, the cannons were removed from surviving T.6s, and some were used for training until 1922.[4]