by: Stephen T. Lawson [ ]
The War office in June 1917 had decided to increase the RFC from 108 squadrons to 200 squadrons, with most of these being bombing squadrons. At the end of June 1917, the Air Board ordered 700 DH.4 machines to equip the new bombing squadrons. In July 1917, a proposal was made to the Air Board by the Technical Air Controller to severely modify the DH.4 which would increase it airspeed to 112 mph @ 10000 ft. and increase the range. This proposal became the DH.9 which rectified the problem of crew communication and the pilot's fear of being the meat in the sandwich being between the engine and fuel tank on the DH.4 in the event of a crash. But this was not the end for the DH 4 and the following details why.
230hp Siddeley Puma have development roots in the 230-hp B.H.P. (Beardmore-Halford-Pullinger) engine. Derivative design concepts with almost no interchangeable parts. The different engines are the result of design teams from different manufacturers. The Puma suffered from the aluminum being too porous. 90% of the castings were rejected rate at one point. It also had problems with burned-out exhaust valves. And it's manufacturing was plagued with production problems. The redesigned Siddeley Puma was promised at 300 hp. As the engine progressed in the production processes, it was de-rated graded 230hp.
The Air Board awarded a contract to the Siddeley-Deasy Car Company for 2000 B.H.P. 230 hp engines. Siddeley-Deasy engineers proceeded to redesign the engine with a promise of 300 hp. Additional orders were placed for the Puma engine. The problem with the Puma engine was the engineers had made major changes in the engine and influenced by the Hispano-Suiza design made the block and head of aluminum castings, with a steel cylinder liner that was screwed into the cast block. The casting were porous and rejects amounted to as much as 90%, which resulted in delayed deliveries. In the end the promise of 300hp fell well short of the mark and produced 230 hp.
The order for the 700 DH.4 airframes was changed to DH.9 machines with the poor performance of the Siddeley Puma being installed in the production DH.9 aircraft, the resultant performance of the DH.9 was less than the DH.4 (which it was to replace). Huge orders had been placed for the Siddeley Puma and the DH.9 machines. To resolve this problem, Airco designed a new aircraft, the DH.9a powered with the 375hp Rolls-Royce Eagle VIII or the 400hp Liberty. The DH.9a were issued to the RAF bombing squadrons near war's end. It had the speed, bomb capacity and range the RFC was looking for in June 1917. The DH.9 program was a disaster! Those responsible were Siddeley-Deasy for the engine, the Air Board for committing the engine and aircraft industry to mass production of a good aircraft with a lousy engine which failed to meet the claimed performance. To quote general Trenchard, ". . .The DH.9 was a good airplane spoiled by a bad engine. . ." The re-engined DH.4 was placed back into production.
Markngs are provided for three Westland built aircraft:
I. DH 4 N6416, F Sqn 62 wing RNAS, Imbros Spring 1918.
II. DH 4 N6416, F Sqn 62 wing RNAS, Imbros Summer 1918.
III. DH4 D1773, 224th RAF Mudros, Spring 1918.
One further note here. Roden does give you a paper template for the sunburst design for the fuselage of N6416.
The decals appear to be quality and are thin and glossy. The printing is sharp and the roundel centres are separate to ensure correct line-up. Sadly the register for the blue rings on their white background is a tad off on my sheet - it's a shame these couldn't have been separate too.
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