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Blackburn B.20

1940 WORLD WAR 2 X-PLANE

Blackburn B. 20 Stories

The UK's vast coastline and free access to the surrounding waters made it a priority for its military to deploy a capable flying fleet in the post/pre-WWII era. As technology allows, these platforms have gradually become more advanced and have become a key component of maritime operations involving the Royal Navy (RN) and Royal Air Force (RAF).

As World War II began in September 1939, the fleet proved vital to the reach of both services, helping to avoid defeat and, in turn, help secure the eventual victory in 1945.

Before the war in 1936, the RAF developed a new specification for compact reconnaissance flying boat aircraft based on the R. 1/36 specification. Airships provide two very important qualities in their design: they provide excellent water range and excellent dwell time.

In addition, the model has built-in capabilities to land and take off on water without having to prepare for disengagement. The only requirement revealed by authorities is a minimum speed of 230 mph.

The two companies brought two very similar designs: Saunders-Roe offered their "A. 36" and Blackburn offered their "B. 20".

Blackburn's product is particularly notable because it features a retractable pontoon assembly built as part of a boat-like fuselage that can be maneuvered during landing or takeoff and then "tucked" into the air for travel, keeping air kinetic efficiency.

This unique mechanical system solves a problem that was soon discovered - protecting the engine from salty sea spray while driving along the water. Prior to this period in aviation history, the problem was solved by simply mounting the engine on the upper wing assembly of the biplane.

The move to monoplanes as the new aircraft standard now means the engines are close to the ground, or in this case, the water. One option is to make a deep fuselage/fuselage to lift the engine, but this reduces aerodynamic efficiency by creating additional drag.

So Blackburn B.20 is an interesting answer to this challenge, trying to solve it with a more complex but possibly more practical arrangement - keeping the monoplane wing and actively influencing the fuselage itself during flight (according to required) instead.

The result is an aircraft more like a seaplane or seaplane than an actual airship. The boat-shaped fuselage sits under the fuselage as usual, but only unfolds when needed, and outboard pontoons are used to stabilize the plane on the water (and fold up when not in use). The wing main aircraft is mounted high on the upper side of the fuselage, and the engines are mounted on each wing panel near the wing root.

A heavy flight deck overlooks the nose in a traditional fashion, allowing the pilot to clearly see the engines mounted on the leading edges of the wings on either side of the cockpit. The fuselage tapers to the rear, and the empennage contains a rounded vertical fin and deep horizontal planes.

The design of the aircraft is credited to John Douglas Rennie, and the prototype first flew on March 26, 1940. However, in April, extreme aileron flutter forced the crew to parachute (three were killed in action) and the aircraft was declared a total loss.

With only a few test flights with this aircraft to test the validity of the retractable fuselage idea, it is clear that the RAF authorities have seen enough of the project to (when) confirm their interest in the B. 20 commitments so that no additional development work is required).

By design, the B.20 was powered by 2 Rolls-Royce Vulture X 24-cylinder engines, each with 1,720 hp, which were used to drive the three-bladed propellers in a traditional "pull-rod" fashion. Performance includes a top speed of 305 mph and a range of up to 1,500 miles. Dimensions are 69.7 feet long, 82 feet wingspan, and 25 feet tall. The MTOW is rated at 35,000 lbs. Weapons are defensive in nature and consist of cannons and machine guns, including two powered turrets.

The operations team consists of six people.

In the end, Saunders-Roe's offer A.36 "Lerwick" became the more successful of the two offers, but even this design was not an absolute success, with only 21 examples being obtained. Royal Air Force (and a few are used by the Royal Canadian Air Force (RCAF)).

The series did poorly in actual war service and was very accident prone (in fact, ten of them were lost this way). With its opening in 1940, the line had to be decommissioned in 1942.

The Blackburn B. 40 was designed as an improved version of the B. 20 with larger dimensions, which was covered in the 1940 R. 13/40 specification. In September 1941, the RAF ordered a pair of B.40 prototypes for development, but upon review the model was deemed neither worthy of additional work nor funding, leading to its peaceful demise in December of that year.

The aircraft will carry 2 x Bristol Centaurus air-cooled radial piston engines and a mix of cannon and machine gun weapons for defense. Dimensions include a 98-foot wingspan and 52,000-pound MTOW. Short Sunderland eventually found its way into service (detailed elsewhere on this site).