| Severn | |
|---|---|
 | |
| Prototype (N240). | |
| Role | Maritime patrol flying boat |
| National origin | United Kingdom |
| Manufacturer | S.E. Saunders Ltd. |
| Designer | Harry Knowler |
| First flight | July 1930 |
| Introduction | 1932 |
| Status | Lost 1932 |
| Primary user | Royal Air Force |
| Number built | 1 |
The Saunders Severn was a three-engined biplane flying boat intended for maritime patrol duties. It performed well but was fragile and unreliable. Only one was built.
The Saunders A.7 Severn was the last flying boat designed by S.E. Saunders Ltd before the takeover by A.V. Roe and John Lord late in 1928 that produced the Saunders-Roe, or "Saro", company. Its first flight was two years after this change of ownership and it has been alternatively referred to as the Saunders/Saro Severn, [1] the Saunders-Roe A7 [2] and the Saro A7. [3] It was designed to Air Ministry specification R.4/27 for a maritime patrol aircraft.
It was the second Saunders aircraft to use their patented "corrugated" structure for the hull, first trialled on the Saunders A.14, in which longitudinal external corrugations in the skin replaced internal riveted stringers. Full trials of the A.14, revealing both the strengths and weaknesses of this technique were not made until after the Severn had flown. Like the A.14 the Severn's construction largely avoided doubly curved hull plating, so the planing bottom was strictly V-shaped and the upper hull rather slab sided. The hull was a two-step design with tumble-home sides above the chines. There was a gunner's position in the nose and a side-by-side open cockpit for the pilots ahead of the engines and wing. Behind the cockpit and within a windowed part of the hull were crew positions and accommodation, from which a dorsal gunner's position just aft of the wings could be accessed. There was an isolated rear gunner's position at the extreme rear of the upswept rear fuselage, above the braced tailplane and between the two braced fins. Twin balanced elevators projected beyond the tailplane and the fins carried balanced rudders. Early flight trials showed the Severn to be heavy on rudder control, so separate servo-rudders were soon fixed on struts behind the main rudder surfaces. It was also heavy on elevators, which were increased in area. [4]
The Severn was a three-engined sesquiplane, the lower wing having a span of only 58% of the upper one and about 52% of the chord. This small lower wing was mounted just below the hull decking. Both wings were made of fabric-covered duralumin. The upper wing, which carried the ailerons, was joined at its centreline to the upper edges of the fuselage by a tandem pair of inverted V-struts, the forward one supporting the central engine, which was faired into the underside of the wing. Single vertical struts held the outer engines in similar positions, with single inward-leaning struts at the rear. There were outboard outwardly-splayed interplane struts with the braced stabilising single-stepped floats mounted below. The three 490-hp (365 kW) Bristol Jupiter XI radial engines each had their nine uncowled cylinders forward of the wing leading edge, driving two-bladed propellers. [4]
The Severn first flew in July 1930 and began a test programme with the Marine Aircraft Experimental Establishment (MAEE) at Felixstowe in August. This soon led to a reduction in tailplane area to reduce the Severn's excessive longitudinal stability. That apart, the Severn's handling in the air and on water were found good, as was its performance. It was let down by a long series of faults due to a combination of weight-saving design and a lack of attention to detail, which would have caused unacceptable serviceability problems in Service. Some of the faults were serious, like the failure of the central engine mounting and multiple cracks that appeared in the hull; others, like the breaking of brackets and the loss of wing inspection flaps were less serious but numerous. [4]
To explore the balance between good air and water performance and behaviour versus the expanding fault list, MAEE decided the Severn should go on a proving flight to the Near East. This took the Severn and an accompanying Supermarine Southampton 6,530 miles via Port Sudan and included trials on Lake Timsah. The conclusions were as before: the Severn performed well in the air and on the water, was seaworthy during a storm and returned without corrosion, but suffered from many problems both small and large. The second category included broken ribs and a servo-rudder kingpost and the conclusion was that this was not a practical aircraft for Service use, so no orders followed. Nonetheless, the sole Severn served for about five months with No. 209 Squadron RAF after the end of the MAEE trials before it was lost in the English Channel. [4]
Saro learned from the experience and their next aircraft, the Saro London was considerably more robust. [5]
Data from London 1988, p. 85
General characteristics
Performance
Armament
Related development
Related lists
The Saunders-Roe A.36 Lerwick was a British flying boat built by Saunders-Roe Limited (Saro). It was intended to be used with the Short Sunderland in Royal Air Force Coastal Command but it was a flawed design and only a small number were built. They had a poor service record and a high accident rate; of 21 aircraft, 10 were lost to accidents and one for an unknown reason.
The Saunders Roe A.37 Shrimp was a 1930s British two-seat four-engined experimental flying boat built by Saunders-Roe Limited ("Saro") at Cowes.
The Short R.24/31 was a British twin-engined, high-wing cantilever gull winged monoplane flying-boat designed and built by Short to Air Ministry specification R.24/31 for a "General Purpose Open Sea Patrol Flying Boat". The contract also specified the use of the experimental Rolls-Royce Goshawk engine. The Saunders-Roe London and the Supermarine Stranraer competed successfully for this contract.
The Roe I Triplane was an early aircraft designed and built by A.V. Roe which was the first all-British aircraft to fly..
The Avro Type D was an aircraft built in 1911 by the pioneer British aircraft designer A.V. Roe. Roe had previously built and flown several aircraft at Brooklands, most being tractor layout triplanes. The Type D was his first biplane.
The Supermarine Air Yacht was a British luxury passenger-carrying flying boat. It was designed by Supermarine's chief designer R. J. Mitchell and built in Woolston, Southampton in 1929. It was commissioned by the brewing magnate Ernest Guinness, and was the first British flying yacht built to the order of a private owner. Only one machine was built.
The Saro A.33 was a British prototype flying boat built by Saunders-Roe Limited in response to a British Air Ministry Specification R.2/33 and in competition with the Short Sunderland.
The Saunders Kittiwake was a British amphibian flying-boat built by S. E. Saunders at East Cowes, Isle of Wight.
The Bristol Type 118 was a general-purpose military aircraft, a two-seat biplane built by the Bristol Aeroplane Company in the early 1930s, powered by a Bristol Mercury radial engine and aimed at overseas markets. The Type 120 was a Bristol Pegasus-engined variant entered into an Air Ministry competition and later used for armament tests. Two aircraft were built.
The Saunders A.3 Valkyrie was a large three-engined biplane flying boat with a wooden hull built to an Air Ministry specification. It was not found suitable for production and helped to confirm a preference for metal-hulled flying boats.
The Saunders A.14 was a test aircraft for Saunders' new metal hull construction method, being a Supermarine Southampton fitted with the Saunders' fuselage. The methods tested worked well enough to be used in SARO flying boat production from 1928 to 1938.
The Saunders A.10 was a private venture four-gun fighter. It was a single-seat, single-engined biplane with poor handling, later serving as a gun-testing aircraft.
The Parnall Perch was a single-engined, side-by-side-seat aircraft designed in the UK to meet an Air Ministry specification for a general-purpose trainer. No contract on this specification were awarded and only one Perch was built.
The Parnall Pike was a 2/3-seat biplane reconnaissance aircraft, capable of operating off carrier decks or from water, built to an Air Ministry specification in 1927. Only one was constructed.
The Dyle et Bacalan DB-10 was a heavy night bomber, designed in France and flown in 1926. It was a twin engine, high wing, metal frame monoplane, distinguished by a very thick centre section wing which formed the forward fuselage and housed the engines.
The Zeppelin-Lindau Rs.II was a biplane flying boat, designed by Claudius Dornier and built during 1914–1915 on the German side of Lake Constance. Initially this aircraft was powered by three engines mounted inside the hull driving three pusher propellers via gearboxes and shafts. The later version was powered by four engines in two push-pull nacelles mounted between the wings.
The Caproni Ca.66 was an Italian night bomber designed to reequip the post-World War I Italian Air Force. Only two examples of the four-engined biplane were built.
The SPCA 10 or SPCA Paulhan-Pillard E.5 was a large, all-metal, French reconnaissance and bomber flying boat flown in 1928. Only one was built, and it was lost in a fatal crash during development.
The Caproni Ca.66 and Caproni Ca.67 were Italian night bomber aircraft designed to re-equip the post-World War I Regia Aeronautica.
The Zeppelin-Lindau Gs.I, often known post-WWI as the Dornier Gs.I after its designer Claude Dornier, was a civil flying boat developed immediate post-war from a military prototype. Its passenger cabin seated six. Only one was completed, and that was eventually scuttled to keep it out of Allied hands. Another of the military prototypes was intended to have a bigger, nine seat cabin and other refinements but the Gs.II was incomplete when discovered by Allied inspectors.
