Biplanes to Monoplanes

 

The years following the Great War were lean times for warplane manufacturers. Of 56 distinct Bristol designs only 18 reached flying prototypes and only 2 entered production. One unsuccessful plane was the Badminton, for which Russell did the wing stress calculations, and specially designed for the 1926 King’s Cup air race, He was gravely concerned when the plane crashed a month before the race killing the pilot. It turned out that the uprated engine had seized solid.

 

The Bagshot of 1925 was an attempt at a monoplane fighter but it did not perform well. Russell was sent up with the test pilot and he observed quite alarming twisting of the wings. (The two wings of biplanes could be strutted and stayed to form a rigid ‘box’ with high torsional stiffness) After inconclusive consultations with various academics Russell realised that the bending and torsional stresses could be calculated independently. He was later granted a patent on a single spar wing design using these principles.

 

There was to be another successful biplane fighter from Bristol in the Bulldog (1928). Russell did the stress calculations for the wings and was an interested observer of the loading tests that proved the validity of the calculations. A near complete plane was suspended upside down and the wings were progressively loaded with 1600 bags of lead shot each weighing 16 lbs. In total 440 Bulldogs were built including exports to many countries including Japan.

 

In the early 1930s a new sheet material became available. This was Alclad, a sandwich of thin layers of aluminium (for corrosion resistance) over a layer of duralumin (for strength). Covering a wing frame with this material gave a smooth surface and also increased the torsional stiffness.

 

Now the company built the handsome Type 133 monoplane fighter of 1934. This plane could fly at 250 mph and was 25 mph faster than any serving fighter or prototype around. With all tests satisfactorily completed the plane looked like a winner, but the day before official trials it was destroyed in a bizarre accident due to pilot error. Contracts were placed for its slow rival the Gloster Gladiator – another biplane. The future looked bleak for Bristol.

 

Planes for World War II

Lord Rothermere ordered an aeroplane with the highest possible speed, a crew of two, and cabin space for six passengers. Earlier plans for a small airliner were dusted off, and soon Lord Rothermere had a twin engine monoplane Type 142 (1934) that could fly at more than 300 mph. He named it Britain First and used his newspapers to boast that his new plane could fly 50 mph faster than the very latest RAF fighters.

 

With a minimum of effort and a great deal of foresight the Type 142 was transformed into a bomber the Type 142m Blenheim (1936). The wings were raised from the low position to mid fuselage to make room for a bomb cell with 1000 lb bomb capacity. The Air Ministry placed orders for 718. Russell was made head of the Technical Office responsible for stressing, structures development and tests, aerodynamics and weight estimation. Derivatives from the Blenheim using higher wing loadings, increased engine power, higher payloads, gun turrets, radar etc. included,

 

• Bolingbroke (1937) – Coastal reconnaissance for the Royal Canadian Air Force

• Beaufort (1938) – Tactical reconnaissance and torpedo carrier

• Beaufighter (1939) – Multi-role fighter/bomber

• Buckingham (1940) – Bomber

• Brigand (1944) – Torpedo carrier
   

Blenheims were made in Canada, Beauforts in Australia, and large numbers of Beaufighters were rolled out at Bristol and various shadow factories. The Buckingham was the fastest fully armed day bomber (330mph) of its time, but when the Americans entered the war they took over day bombing, and Buckingham production tailed off. In the midst of hostilities Bristol was left without any new design work.

 

The best that came the company’s way was a Design Study Contract for a bomber capable of carrying an 80,000 lb. bomb load to Berlin at as high a cruising speed as possible. For ten years the company had been designing medium sized twin-engine monoplanes. Russell learnt all he could about streamlining and aerodynamics, so that drag could be minimised in the big bomber. To provide sufficient power eight 2,500 HP Centaurus engines were required. Arranged in pairs driving contra-rotating propellers they could all be housed within a wing, with a span of 230 feet and area of 5,000 square feet, again minimising surface drag. Russell became Chief Designer and soon the opportunity came to redesign the bomber as an airliner.

 

Post War Planes

The Brabazon

 

The Government had set up a committee under the chairmanship of Lord Brabazon to determine post war policy for civil airliners. In February 1944 a contract was placed with Bristol for detailed design of a luxury airliner for British Overseas Airways Corporation (BOAC). Russell was appointed Chief Engineer and assumed full responsibility for the Brabazon. Original development work was required on vibration testing, ac electrics, hydraulically powered flying controls etc. The prototype, with Centaurus engines, flew in 1949

 

Unfortunately another new technology was overtaking the project – jet engines. De Havilands were developing the Comet with pure turbine engines, and Vickers were developing the Viscount with turbo prop engines. BOAC wanted Bristol Proteus turbo prop engines in the next prototype Brabazon.. By 1950 it was obvious that the Proteus was not sufficiently developed to do the job and the Brabazon project faded into history.

 

There were other more successful ventures at this time. The Directors instructed Russell to produce a modest ‘aerial truck’ and the result was the twin-engine high wing Bristol Freighter that first flew in December 1945. The plane and its passenger version Wayfarer sold in reasonable numbers to small operators all over the world. They are well remembered for their car ferry operations.

As Chief Engineer Russell was also responsible for a recently acquired helicopter company, that manufactured single and twin rotor machines, and for another engineering group within the company that manufactured guided missiles, with ram jet engines. The Bristol Ferranti Bloodhound was used by the Royal Navy, the RAF and was also adopted in Sweden and Australia.

 

The Britannia

 

In 1947 Bristol won a design competition for ’An airliner to required to carry thirty six passengers on routes to South Africa, Australia and the Far East.’ The number of passengers (36) had been set by the capacity of the standard BOAC airport bus! Russell redesigned the plane for sixty eight passengers. Two years on BOAC wanted Proteus turbo prop engines in this plane as well. The wing area and span of the Britannia was increased, for greater altitude and speed and seating was raised to 96 without altering the fuselage.

 

The first prototype flew in August 1952 using the substandard Proteus engines. Little more was achieved until December 1953 when the second prototype flew with the much improved Proteus III engines designed by Stanley Hooker. Unfortunately an engine exploded on a demonstration flight in February 1954 and with fire risk in mind, the pilot ditched the plane in the mud of the Severn. The fault was failure of the reduction gearing of the engine, and the solution was to change from straight to helical toothed gears.

Worse was to follow for the Britannia project, and for the British aircraft industry in general. The De Haviland Comet was the first jet engine airliner in the world but it was grounded after three crashes in quick succession, the last in April 1954, all due to metal fatigue. A water tank fatigue test became mandatory for all British airliners and the Britannia was probably the most thoroughly tested plane ever at the time. There was further delay when icing problems in the engines nacelles were encountered in of all places the Tropics! A solution to BOAC’s satisfaction took another year.

 

Britannia finally entered service in 1957 – 3 years late. It was a fine aeroplane, but bigger pure jet airliners were now just around the corner and the plane became a stopgap for major airlines. Ninety Britannias were built in Bristol including twenty for RAF Transport Command and some exports. A long range version of the plane could carry 96 passengers, non stop from London to New York, fulfilling the dream of the original Brabazon. Another 87 variants of the plane were built under licence in Canada for military and civil use.

 

Last years of Bristol Aeroplane Company

 

The Brabazon and Britannia stories illustrate a weakness of the civil aviation industry in the United Kingdom in the post war years. Russell pointed out that the National carriers BOAC and BEA ‘had unwisely been granted the privilege of bespoke tailoring their aircraft requirements, heedless of international sales potential.’ None of the manufacturers were reaping the benefits of long production runs.

 

After the very successful Vickers Viscount, BEA ordered a new turboprop plane the Vanguard at very high cost, instead of a modest modification of Britannia. Bristol had a three engine design (Type 200), the very first of this configuration, but BEA bought De Haviland Tridents, whilst the rest of the world bought Boeing 727. The Boeing 707 was sold world wide, but BOAC bought the Vickers VC10. Bristol was losing out all round and reorganisation of the industry was inevitable.

 

Russell took the opportunity in these lean times to learn about supersonic flight. Bristol built two stainless steel research planes (Type188) designed for Mach 3, but limited in trials to Mach 1.8 by underpowered engines. From the Royal Aircraft Establishment at Farnborough, Russell also learned of a ‘breathtaking novelty’ for supersonic flight – a narrow delta wing with a sharp leading edge. With immediate separation at the nose, the airflow rolls up into a strong vortex over the wing. Contrary to all existing streamline theory there was no aerodynamic penalty with this vortex. The configuration also reduced stall to such an extent that landing flaps were un-necessary.

 

American manufacturers were considering Mach 3 planes but Bristol settled on Mach 2.2. This was the maximum speed for which the surface temperature rise would not be excessive using the latest aluminium alloys. The Bristol design study of 1959 and the revision (Type 223) of 1960 for a transatlantic airliner had a narrow delta wing, a variable geometry cockpit and engines in nacelles under the wings. Concorde as built looks remarkably like these studies. But reorganisation came first.