Just at the time that de Havilland were well advanced with Comet 4 production informed industry observers were speculating on it’s successor.
Talk was of a major re-development of the Mk.4 – designated ‘Comet 5’.
This was not in fact pure speculation – there had been discussions within the Company about future projects – including a long-range airliner – but nothing further than that had been done.
In this respect de Havilland had four options – to develop the Mk.4 further generally increasing its size and range; or by starting from scratch and designing a new long range jet airliner in house (now as part of Hawker Siddeley); to collaborate with another manufacturer on a similar project (Boeing was a possibility) or to abandon their tentative plans to produce this class of aircraft at all.
At this time there were several reports in the press claiming the existence of the Comet 5 – and, naturally, associating it with BOAC.
Perhaps fed by Company leaks, the general consensus of opinion was that the aircraft would be based on the Mk.4 but would have a new design of wing, with greater sweep, to give it higher cruising speeds and to incorporate four R.R. Conway engines installed in pods (as per 707).
It was suggested that such a machine would be developed for service in the mid-1960s and that it would be done with the backing of BOAC.
The rest is history.
DH 118 – COMET 5
D.H.118 was a design development based on a previous exercise known as the Comet 5. This design featured four pod-mounted R.R. Conway engines. With a projected cruising speed in excess of 550 m.p.h. and a range of 5,000 miles in still air it could provide a London – New York service – even against the prevailing westerly winds – and still have adequate reserves of fuel. Although the company would not admit it a considerable amount of time was spent on this project. In talks between Aubury Burke and Sir Miles Thomas it was clear that de Havilland had the Corporations full backing for the development of the Comet 5. Sir Miles was very enthusiastic about the project.
The project envisaged retaining all the parts of the Comet 1 and 2 that would have been costly to redesign e.g. control systems, flight deck instrumentation, pressurization system and any equipment that had been thoroughly tried and tested. The fuselage would have a thicker skin and would have been widened by inserting a 9 ins. gusset and it thus would be able to seat five abreast in reasonable comfort. Furnishings such as the galley, toilets, doors and windows would be reused. In addition to pod mounted engines the angle of sweep of the wings would have been greater – and thus give a higher maximum speed. In fact it bore a striking resemblance to what was to become the Boeing 707.
Sad to think that with appropriate backing Comet development could have naturally followed that route. After a heated discussion with the then Minister of Transport – Harold Watkinson – the Minister refused to approve the project. At the hands of the Ministry the project died. In truth the Ministry of Transport did not seriously consider what BOAC really wanted. The new Minister of Transport was determined to make his own decisions and not to be influenced or encumbered by any previous Ministers’ inclinations nor apparently by what his rival at the Ministry of Supply thought logical.
Sir Miles concluded later that he should have fought harder for the Comet 5 for it would have had a profound effect beyond that of meeting the fleet needs of BOAC. As it happened Britain would have saved a considerable amount in Dollar exchange, the world would have see Britain build upon it’s short-held lead in commercial jet transport and the whole country would be given a much needed boost to morale.
It was said that at an early stage in the design of the 707 Boeing were particularly worried about possibility of jet-engine failure and a risk of a turbine break-up causing shrapnel to puncture the pressurised fuselage and, apart from the possible catastrophic consequences of decompression, there was the danger of the flight control systems being severed. Thus Boeing favoured hanging the engines in pods away from the fuselage and away from the control surfaces and operating systems. So it is particularly interesting to note though that De Havilland too looked seriously at this layout. As it happens, with the exception of one minor incident where a carpet got singed (on an Aerolineas Argentinas aeroplane), no Comet suffered failure of the turbines as envisaged by Boeing. Of course jet engine reliability was not as good then as it is today. The Boeing format was very successful and provided the basis for a huge range of profitable variants.
The footnote to this story was that on March 8th 1956 Sir Miles Thomas tended his resignation to the BOAC Board. On the 24th October 1956 BOAC, with government approval, placed a record order for 15 707-436 aircraft. The irony is that the power-plant specified was R.R. Conway 508 17500 lb.st.!!! It seems that for whatever reason the Ministry had wanted the Boeing all along.