The Saro A.27 London was one of the last generation of large biplane flying planes to serve in the RAF, operating alongside the Supermarine Stranraer in Coastal Command in the years immediately before the Second World War.
The London was designed by Henry Knowler in response to Air Ministry specification R.24/31, which called for a twin engined general purpose and coastal patrol aircraft. It was a sesquiplane (with two wings of unequal length). The two engines were attached to the bottom of the longer upper, wing, which also contained the four 137-gallon fuel tanks and the ailerons. The wings were fabric covered, built around a duralumin structure, while the hull was built from duralumin coated in Alclad. Extra fuel could be carried in tanks on the deck of the main fuselage. The fuselage itself was built with straight-line frames and a corrugated metal shell (this slightly increased drag but made the aircraft easier to build). The London was the last Saunders-Roe aircraft to use this system, which was not suited for the higher speeds required of later aircraft. A combined bow mooring and gunnery position was in the bow. Next came a two-man side-by-side covered pilot’s cockpit with dual controls. Behind that was a wardroom with two bunks and the navigation station, then the crew cabin with the engineers panel and wireless post, then the dorsal gun position, then storage space capable of holding a spare propeller, a dinghy and maintenance platforms. A gangway led from this storage area to the rear gunner’s position. All three gun positions carried a single Lewis gun on a Scarff mount.
The prototype, powered by two 820hp Bristol Pegasus IIIMS radial engines, was complete by March 1934. It passed its service trials with flying colours, and in March 1935 the Air Ministry placed an order for seven Mk Is. The first of these was tested at Felixstow between June 1936 and February 1937 (after the London had entered service).
The London entered service with No.201 Squadron in April 1936, replacing the squadron’s Supermarine Southamptons. Eventually seven squadrons in Coastal Command would receive the London, but it had a short service life. Only three squadrons (Nos.201, 202 and 240) were still equipped with the London at the start of the Second World War. Nos.201 and 240 squadrons used their aircraft for patrols around the coast of Scotland and out towards Norway, while No.202 took its Londons to Gibraltar. The London was vulnerable to attack by just about any German aircraft it might encounter, and was withdrawn during 1940 and 1941. The London gained a reputation for being reliable and rugged, but it was already obsolescent by the time it entered service.
Seven London Is were ordered in March 1935. They were similar to the prototype, but had modified wing floats, a four bladed propeller and circular engine cowlings. Some sources state than ten Mk Is and 20 Mk IIs were delivered, but as the Mk Is were quickly modified to Mk II standard the important number is the total figure of thirty.
The Mk II was powered by the more powerful 1,000hp Pegasus X engine. Twenty three Mk IIs were delivered between 1937 and May 1938, while the surviving Mk Is were brought up to the new standard.
Engine: Bristol Pegasus X
Wing span: 80ft
Length: 56ft 9in
Height: 18ft 9in
Empty weight: 12,800lb
Loaded weight: 18,400lb
Maximum speed: 155mph
Service ceiling: 19,900ft
Maximum Range: 1,100 miles
Armament: one 0.303in Lewis gun in the nose, dorsal and tail positions
Bomb load: 2,000lb of bombs or depth charges