The Germans responded to Sunderland attacks by fitting some U-boats with one or two 37 mm and twin quad 20 mm flak guns to fire back at their attackers . While Sunderlands could suppress flak to an extent with their nose turret guns , the U-boats guns had superior range , hitting power and accuracy . Attempting to shoot down Allied aircraft did , however , prolong the U-boat 's presence on the surface , which made sinking the vessel easier . Nonetheless , fitting of substantial arrays of anti-aircraft guns temporarily decreased U-boat losses while both Allied aircraft and shipping losses rose . As a countermeasure to the increased defensive armament of the U-boats , the Australians fitted their aircraft in the field with an additional four .303 s in fixed mounts in the nose , allowing the pilot to add fire while diving on the submarine before bomb release . Most aircraft were similarly modified . The addition of single .50 inch ( 12.7 mm ) flexibly mounted M2 Browning machine guns in the beam hatches behind and above the wing trailing edge also became common . The type 's capacity to defend itself was demonstrated in particular by an air battle over the Bay of Biscay on 2 June 1943 , when eight Junkers Ju 88Cs attacked a single Sunderland Mk III of No. 461 Squadron RAAF : '' EJ134 '' , squadron code : " N for Nuts " . The 11 crew , led by F/Lt Colin Walker , were on an anti-submarine patrol , while also watching for any signs of a missing airliner , BOAC Flight 777 . At 1900 hours , the rear gunner saw the Ju 88s , which belonged to '' V.Kampfgeschwader 40 '' and were led by Leutnant Friedrich Maeder . Walker ordered the dumping of the bombs and depth charges , and took the engines to full power . Two Ju 88s made simultaneous passes at '' EJ134 '' from both sides , scoring hits and disabling one engine , while the pilots fought fires and took the Sunderland through corkscrew manoeuvres . On a third pass , the dorsal turret gunner badly damaged or shot down a Ju 88 , although the Sunderland 's rear gunner was knocked unconscious
BOAC Flight 777
BOAC Flight 777
Short Sunderland