Profile – DH Comet Pt 11

Matters continued to deteriorate when on 2 May 1953, a BOAC Comet G-ALYV was destroyed when it suffered a structural failure after departure from Calcutta. One of the major consequences of this loss was that it put paid to any future Comet operations by an Australian airline. John Watkins, who was TAA’s Director of Engineering for many years, was for some time also connected with BCPA who were interested in the Comet for their Pacific route. During a discussion I had with John Watkins, he made the following observations regarding the Calcutta accident and its bearing on BCPA’s plans.

“Norman Watt was chairman at the time and I said to him that it seemed it was important that we got as much information as we possibly could out of this accident to decide what we should do about it. It was the first serious accident to a Comet. There had been takeoff accidents and minor things, but this was where an aeroplane had disintegrated in mid air and what the cause was nobody knew, as far as we were aware, in Australia. So they sent me up to Calcutta. Now I had been in India previously for about six months with the Air Transport Enquiry Committee and I knew a lot of people in the Administration. I was in a good position to get onto their chief inspector of accidents and get access to all the wreckage that was still there, a lot of it had been taken back to England. I was able to see all the detail photographs of the wreckage as it lay, all the eyewitness reports and I was in a position to check on Dum Dum Aerodrome itself. What the situation had been there, how long the aeroplane had been standing there, what fuelling had been done and so on. It aroused some serious doubts in my mind.

“The aeroplane had taken off, had only been flying for seven minutes I think, it was climbing towards some thunderclouds and it went into a cloud and exploded. It seemed to me that turbulence may have been the prime cause but there was no proof that I could find in the evidence of the look of the pieces on the ground. But obviously there had been fire in the back of the fuselage. I couldn’t get out of my mind the thought that it could have been an internal electric discharge when the aeroplane was struck by lightning. Now everybody says that it can’t happen but we have had plenty of proof that it can happen. You can get a spark discharge inside a metal shell which is not completely in good electric contact everywhere. I discovered that the Comet had taken off with only 200 gallons of hot kerosene in a 1,000 gallon tank under the belly. And kerosene has the opposite characteristic from aviation gasoline in that its under hot conditions when you’re liable to get an explosive mixture of air and kerosene vapour. There had been cases of wings exploding at high level over the Atlantic with a lightning strike with petrol in the tanks.

“Now this was a case where an aeroplane had refuelled from a tank wagon standing the Calcutta sun in mid afternoon. I checked the temperature of kerosene in a tank wagon there myself and it was about 95°F. Pumped into an empty tank in the belly of a Comet, because he needed a little extra fuel, as the weather did not look too good in Delhi which was to be the next stop, and a few minutes later he flew into a thunderstorm and exploded. I could not get out of my mind the possibility that this is what happened. Anyway we will never know. What did happen is that the British investigators came to the conclusion it must have been overload of the tail unit in violent turbulence in this thunderstorm. That may have been so, but if so, I believe that in the break up that fuel did explode because the fire in the rear fuselage wasn’t explained by a tail structural failure. But it would have been if that central tank had burst, it would have come up through the floor. The actual tank in the wreckage was all rounded as if there had been an explosion in it anyway.

“My recommendation to BCPA had to be that we suspend negotiations with de Havilland until there was a clear explanation of what went on with this accident. But before we got a clear explanation of that, two more had crashed in the Mediterranean and the type had been grounded. It took 4½ years to get the Comet back into airline service. Well in the meantime, BCPA had gone out of existence and Qantas had already ordered Boeing 707s, so the first jets that went onto the Pacific were Qantas 707s and not BCPA Comets. It was a disappointment but in the circumstances obviously it was the only thing to do. It has been written that BCPA had ordered six Comets which was quite wrong. We had never been talking about more than two, we were going to start with a fleet of two and we had never ordered them. But we had drawn up a specification for a BCPA Comet 2. This is a print of the BCPA specification that I have messed around with because we had an idea of using the Comet OI) the Perth run for TAA and you will find some TAA seats in it. The Comet was one of the solutions possible for the Perth route. But tAA really wanted something with a shorter range than the Comet and a longer range than the Viscount. ”

It was the two accidents during the early part of 1954 which caused doubts and further serious questions about the Comet. On 1o January 1954 G-ALVP, the first production Comet 1 , took off from Rome for London. While passing through 26,000ft the aircraft broke up and crashed into the Mediterranean 10 miles south of Elba. As a result, all the remaining Comets were grounded while the accident was investigated. No cause was deter mined and the grounding order was lifted during March 1954. However not long after on 8 April 1954, G-ALYY on charter to South African Airways departed from Rome and broke up crashing into the sea near Stromboli. As a result, II Comets were again grounded four days later, following withdrawal of the Certificate of Airworthiness, and production of Comets was halted.

An intensive investigation into the accidents was now undertaken. The scope of the search for the cause of Comet losses, in its breadth and depth, was without parallel in civil aviation. The programme involved in part the ground fatigue testing of Comet 1 s G-ALYR and G-ALVS. The first Canadian Pacific aircraft Comet CF-CUM, which had earlier been converted to Comet 1 standard and sold to BOAC as G-ANAV to replace G-ALYZ, was now used for flight testing. Another Comet 1 G-ALYU was fatigue tested in a water tank at Farnborough. A Royal Navy salvage team recovered the wreckage of G-ALVP from a depth of 600ft near Elba. It was then taken to Farnborough for an exhaustive examination. After a detailed study, the cause of the disasters was identified. A fatigue failure was detected which had started in the cabin near the corner of the window which housed the rear ADF aerial. This had lead to a rupture of the cabin and the loss of the aircraft.

To remedy the problem in the Comet 2s on the production line and in existing Comet 1 s and 1As, a series of modifications were devised. Heavier gauge metal was used in the fuselage pressure shell and all openings were rounded. Fuselage buffeting was reduced by angling the engine jet pipes outwards. The Comet 2s were rebuilt at Chester and the other marks were also modified there.

The receipt of several export orders for the Comet 2 had seen production capacity set up at Hatfield, Chester and with Shorts at Belfast. The first Comet 2 G-AMXA first flew at Hatfield on 27 August 1953. Expectations of the Comet 2’s suitability for non stop North Atlantic operations were not realised as tests have shown its range only permitted flights across the South Atlantic. Of the 18 Comet 2s constructed only 15 were flown. The other three were placed in long-term storage while the parts for three others in production were scrapped. Most of the Comet 2s, after modification for transport use, were delivered to the RAF as either the Comet T. Mk. 2 or C. Mk. 2. Of these, eight were Comet C. 2s modified to allow a 8,000 hour service life, two were Comet T. 2s used as crew trainers and three Comet 2Rs were employed in radar and electronic development roles. Two other Comet 2s became Comet 2Es and were part of the original BOAC order. Of these, G-AXMD was the first to fly after modification during April 1957. Both Comet 2Es were used for RA. 29 Avon engine development roles and radar and radio trials.

Although only one Comet 3 was built, it was an important aircraft in paving the way for the Comet 4. The Comet 3 was announced by de Havilland in 1952 and the Ministry of Supply ordered one prototype. Orders for production versions were received from BOAC, Pan American and Air India for a total of 10 aircraft. Although it did not enter production, its role in ensuring the survival of the Comet programme was vital. Testing of this version continued during the investigations into the problems which were faced by the earlier Comets. The Comet 3 G-ANLO was first flown by John Cunningham and Peter Bugge on 4 May 1954. Powered by the 10,0001b st Rolls-Royce Avon 502, it had a further 15ft 6in fuselage stretch to 111ft 6in, which resulted in a maximum passenger accommodation of 78, and gross weight increase to 145,000lb. Large pinion fuel tanks were fitted to the wings which resulted in an increase of fuel capacity to 8,308 gallons.

During a celebrated round the world tour . in December 1955, . It visited Australia causing immense interest.

Of the departure from Hatfield on 2 December, John Cunningham said, “We planned to leave Hatfield making stops for fuel at Cairo, Bombay, Singapore and Darwin to arrive in Sydney in the middle of the afternoon. We had to leave Hatfield in the small hours of the morning of the day before that. As I drove to Hatfield at 10 minutes past midnight there was a thick fog. It was difficult enough to drive in. It looked rather unlikely that we were going to get off by daylight. In the event of the fog continuing, I was faced with the decision, could I put it off 24 hours? The met. people informed me that it was likely to be just the same 24 hours later and if there was the slightest clearance of a 100 yards or so to enable me to get off I should go out at Hatfield. So at about midday there was a slight clearance, enough to see two lights ahead on the runway and that was sufficient to go off and fly to Cairo, stop the night there and leave the next day. So it all went like clockwork.

“I did have a Qantas pilot who came all the way to England to come out on this flight with me. He was Captain Ian Ralphe and he had never been in a jet aircraft before, because Qantas at that time was flying the Super Constellation. I could see he was rather astonished. His first takeoff was in thick fog when were rushing down the runway and he couldn’t see anything at all and then we burst into what was in fact nice blue sky a short distance off the ground. He remained with me to Sydney. ”

The arrival of the Comet 3 in Sydney on Sunday 4 December 1955 created incredible interest. It created a new speed record covering the 11,585 miles in 24 hours 24 minutes, a significant shaving of the previous 44 hour 28 minute record set in 1953 by a Qantas Constellation. I remember the event well, when as a schoolboy newly arrived from Brisbane only four days before, I had decided that I just had to see the Comet. After a tram ride to Mascot shopping centre I walked to the airport and as I arrived I saw a Pan American World Airways Boeing Stratocruiser belching clouds of smoke as it passed the TAA terminal. If anything, it illustrated the contrast between the airlines’ current equipment and what was soon to be available.

By the time G-ANLO arrived over Mascot, a crowd of 25,000 were there to see it. In an event quite unimaginable today, the crowd even spilled over towards the runway preventing the first landing attempt. The traffic jam of vehicles and pedestrians surrounding the airport took several hours to clear. The only other single aeronautical events at Mascot which even remotely approached the Comet visit in conjuring up such interest were the arrival of the first Boeing 747 and Concorde many years later.

During the period of its visit the Comet also visited Canberra, Melbourne and Perth setting a new Perth/Sydney commercial aircraft record of 4 hours 7 minutes. It left Australia on 13 December on the return flight via the Pacific and North America. The Comet 3 made the first jet airliner crossing of the Pacific and at the end of its flight was also the first to fly around the world. It was later modified to incorporate several Comet 4 features and was re-engined with RA. 29 Avon Mk. 523 engines. Trials incorporating these changes began on 25 February 1957.

The Comet 4 series and the improved versions of it which evolved, was the first Comet which offered a combination of larger passenger accommodation and useful range. However, as good an aircraft as it was, it was the classic case of too little too late. The delay brought about by the Comet grounding and the subsequent investigation was crucial in putting paid to any largescale market penetration by the aircraft. The Comet 4 series, had it been available to the airlines in the mid 1950s, would have undoubtedly sold in considerable numbers. But it was now pitted against the Boeing 707 and Douglas DC-8 for orders and that was formidable competition indeed. Obviously it could not match the capacity, speed or range of its larger competitors but it could offer other attributes such as suitability for shorter, thinner routes and superior hot and high performance which saw it gain several sales.

. The launch order for the Comet 4s was placed by BOAC for 19

Comet 4s for 1959 delivery. Powered by the 10,5001b st RollsRoyce Avon 524, a passenger capacity up to 81, gross weight of 160,000lb and a range of 3,225 miles with a full load, the Comet 4 at last offered the elusive combination that BOAC needed for the North Atlantic routes that earlier Comets had been unable to provide. Apart from the developmental flying for the Comet 4 carried out by the Comet 3, the two Comet 2Es flew with Avon RA. 29 Mk. 524 engines in both the outboard engine positions while retaining RA. 25 Mk. 204 Avons inboard. Engine hours were built up by both Comet 2Es flying simulated services on BOAC routes including the North Atlantic during 1957/58.

The first Comet 4 G-APDA had its maiden flight on 27 April 1958 and joined the other three aircraft in certification trials. During the latter part of 1958, G-APDA demonstrated its capabilities in convincing fashion by completing the then fastest long distance flight ever made by an airliner. It departed from Hong Kong on 14 September two days after the official opening of Kai Tak’s new 7,730ft runway. Making the entire flight in daylight, it covered the 7,925 miles to Hatfield via Bombay and Cairo in 16 hours 16 minutes flying time (18 hours 32 minutes elapsed time). Other records were captured by G-APDA during September including London/Gander flown in 5 hours 47 minutes.

The coveted honour of operating the first jet airliner service across the North Atlantic was given to two BOAC Comet 4s on 4 October 1958 when flights in both directions were simultaneously made by G-APDC from London to New York with G-APDB flying eastwards. If only this could have happened years earlier, the Comet story would have been entirely different. The irony of the event is that the Boeing 707-120 entered service on the same route a few weeks later on 26 October, although the Boeing 707 prototype first flew on 15 July 1954, nearly five years after the Comet’s first flight. The perceived lead of the Comet, which looked so bright after that first flight in 1949, had unfortunately evaporated.

BQAC took delivery of its first Boeing 707-436 on 9 May 1960 and the type was placed into use on the London/New York route on 6 June 1960. This signalled the end of the Comet’s short career on the prestigious North Atlantic route which saw it withdrawn from the blue riband service on 15 October 1960, only just over two years after its introduction into service. The underlying factor in the speedy withdrawal from the route is that although it was capable of operating the service, the Comet was no match for the larger, more economical US jet airliners. With their larger capacity and greater range, they were more attuned to market needs.

The BOAC Comet 4s were then introduced onto more suitable routes to South Africa, the Far East and Australia where they gave several years of reliable service. At various times during this period, BOAC Comets were chartered by other operators including Qantas, Nigeria Airways, Air Ceylon and Air India. The arrangement with Qantas commenced on 1 November 1959 with flights between London and Singapore operated by G-APDE carrying Qantas markings taped over the BOAC fuselage logos. The Qantas Comet charter flights were made to ports on the Kangaroo Route incapable of accepting Qantas’ new Boeing 707s. On arrival at Singapore the passengers were transferred to a Qantas Super Constellation for the remainder of their flight to Sydney.

BOAC Comet operations came to an end when G-APDM passed through Sydney on 23 November 1965 on an Auckland to London service. The Cornet had been the only jet airliner able to operate into Auckland’s confined Whenuapai airport and the type was replaced by Boeing 707s after. Mangere was opened the following day. Considering all the effort which had been expended by de Havilland to perfect the Comet 4 version, its front line service life of about seven years with BOAC was minimal. Unfortunately for the Comet, its departure from service was hastened by the arrival of more suitable equipment.

Other variations of the Comet 4 family were built for other operators. An approach from Capital Airlines during July 1956 for a shorter range, higher capacity Comet 4A in addition to some Comet 4s did not proceed for financial reasons. The proposed 4A version for short/medium range operations at a lower 23,500ft cruise altitude would have had a smaller wing span of 107ft 10in

and a 40 inch fuselage stretch increasing passenger accommodation to 92.

Although the Comet 4A did not go ahead, a British European Airways Corporation approach for a similar short-range/higher density Comet for its routes lead to the Comet 48. It featured a reduced span wing proposed for the 4A, but the fuselage was 6ft 6in longer than the Comet 4, the pinion fuel tanks were removed reducing fuel capacity to 7,890 gallons and the gross weight was 157,960lb. Powerplants were the 10,500Ib st Avon RA. 29 fitted with thrust reversers and sound suppressors. The trusty Comet 3 G-ANLO was modified with a shorter span wing, had thrust reversers installed and first flew in this configuration as a Comet 38 on 21 August 1958. Certification trials of the first Comet 48 G-APMA began during June 1959 and the initial Comet 48 entered BEA service during April 1960. Apart from 14 Comet 48s delivered to BEA, a further four were purchased by Olympic Airways.

The experience gained with the Comet 4 and 48 lead to the final Comet version, the 4C. This Comet combined the lengthened fuselage of the 48 with the full span, high fuel capacity wing of the Comet 4. The initial order from Mexicana for three aircraft was placed after that airline realised that this version would be ideal for operations from Mexico City’s hot and high airport. The first Comet 4C, the initial one for Mexicana, first flew as G-AOVU on 31 October 1959 before it was delivered to Mexicana as XB-NAR. Other 4C orders were received from United Arab Airlines 9, Middle East Airlines 4, Aerolineas Argentinas 1, East African Airlines 3, Sudan Airways 2, a VIP version for King ibn Saud of Saudi Arabia and the RAF which received 5 as the Comet C. Mk. 4. Comet production terminated at Chester during 1964 after a total of 111 Comets of all marks had been delivered. Two unsold Comet 4C airframes were later modified to become the two HS. 801 Nimrod prototypes.

The design of the Nimrod is based on the Comet 4C airframe with substantial structural modifications to enable it to carry all the required equipment for its maritime reconnaissance role. The fuselage length of the shorter Comet 4 was used and fuselage volume increased by blending an additional unpressurised section underneath to accommodate the weapons bay. The expanded nose portion houses the ASV radar scanner. Many additional visible changes arise from projections which contain MAD, ESM and other equipment. The first prototype Nimrod XV148 powered by Rolls-Royce Speys was flown by John Cunningham at Chester on 23 May 1967 and the second prototype XV147 (which had retained its Avons) flew not long after on 31 July. The initial example of 46 MR1, MR2 and R1 production versions first flew on 28 June 1968. Since then, several Nimrods have been further extensively modified for the AEW role. The continued service of the Nimrod well into the next century means that the Comet heritage will exceed a 50 year time frame, an exceptional record to say the least.

Although Comets were withdrawn from use by major operators such as BOAC quite early in their career they were eagerly sought by other airlines. When BOAC had no further use for their Comets, several were chartered to other airlines with the largest batch of six going to Malaysia-Singapore Airlines. Other BOAC Comets were chartered to Mexicana, Middle East Airlines, Aerovias Ecuatorianas and Kuwait Airways. Many subsequent changes of ownership took place in the 1970s with Dan-Air eventually absorbing most of the surviving Comet 4s, 4Bs and 4Cs and having the distinction of becoming the last civil Comet operator.

The contribution of the Comet extended beyond the service it gave to both the airlines and the RAF as it was also employed as a test vehicle for various projects. Typical of the roles it fulfilled saw the versatile Comet 3B G-ANLO join the Royal Aircraft Establishment, Bedford during June 1961 as XP915 where it was used by both the aerodynamics section and Blind Landing Experimental Unit until March 1972. After being used in other non-flying roles, it was transferred by road to Woodford to be used in theNimrod programme. Another example was the Comet 2E G-AMXK, employed as an automatic landing test bed by Smiths Aircraft Instruments Ltd at Hatfield before joining RAE Bedford as XV144 in November 1966 for further development work Forty years after the flight of the first Comet, there are now only two airworthy examples remaining. One of these is XV814, a Comet 4 now based at Farnborough. This aircraft was formerly BOAC’s G-APDF, before ownership passed to the Ministry of Technology in 1970. The other Comet is XS235 ‘Canopus’, a 4C based at Boscombe Down used for navigational systems trials. Other non-flying Comets are preserved at several locations in the UK.

In the four decades that have elapsed since the Comet’s first flight, civil jet transport aircraft have developed steadily. Airframe refinements have been blended with powerplant improvements, further coupled with the progress made in many other fields such as new materials and much more sophisticated avionics. From the Comet’s small payload and short range, we now have a whole spectrum of airlines ranging in size from the quite small to the Boeing 747-400, capable of carrying 400 passengers with ease across the Pacific non-stop. The domestic and international airline fraternity operates a fleet of thousands of jet airliners with reliability, speed and comfort. The valuable lessons learned by the aviation industry as a result of the searching inquiry into the Comet accidents have been of inestimable help in shaping the jet airliner of today. The great shame in all these events is that de Havilland did not reap the rewards that it so justly deserved with its pioneering development of the Comet.