"COMET HISTORY - PART 2" .... continued from above
The RCAF also purchased 2 COMET 1A aircraft (# 5301 and # 5302) .... the very first military order for the type. The first aircraft was delivered on March 18th 1953. These aircraft operated Air Transport Command service roles with # 412 SQDN RCAF.
After the 1954 COMET disasters both aircraft were returned to De HAVILLAND and structurally reinforced .... redesignated COMET 1XB aircraft. Once modified these aircraft were conspicuous by their oval shaped cabin windows.
Both aircraft were also additionally upgraded with DH Ghost 50 MK 4 turbojet engines rated at 5,500 lbs thrust each and which enabled recertification for a MGW of 117,000 lbs. After a long period of storage at Hatfield, these aircraft rejoined # 412 SQDN RCAF during September 1957, the last of which (# 5302) remained in service until its retirement on October 3rd 1964. RCAF # 5301 was used for spares recovery for # 5302 and was eventually scrapped during 1965. Its nose section was presented to the NATIONAL AVIATION MUSEUM, at Rocliffe, Ottawa, Canada and where it remain in storage today. RCAF # 5302 was sold to Eldon ARMSTRONG as an executive transport (re-registered CF-SVR) and based at Mount Hope, Hamilton, as a VIP transport and prior to being sold to B.DALLAS AAEROMOTIVE during 1968. It was eventually re-registered N373S, but, never flew again, was finally scrapped at Miami during 1975.
The 5 remaining AIR FRANCE and UAT COMET 1A aircraft were all withdrawn from service during April 1954 and returned to DE HAVILLAND. 2 of these aircraft were upgraded to COMET 1XB standard during 1957 then used for flight testing and developmental work by the MOS. F-BGNY was first re-registered G-AOJU, then XM829 during Decca Dectra trials with the A&AEE during 1958, It was later dismantled and used by the Stansted Airport RFS from 1964. The worlds last remaining example of a COMET 1A (G-APAS ex F-BGNZ) has since been preserved for public display at the COSFORD AEROSPACE MUSEUM. Both remaining ex UAT COMET 1A's (F-BGSA, and F-BGSB) were eventually scrapped during 1961.
The production of COMET 1 & 1A aircraft was undertaken by DE HAVILLAND at its Hatfield facility, whilst COMET 2 aircraft were produced at Cheshire. During the early 1950's DE HAVILLAND also negotiated additional COMET production space at the SHORTS BROHERS facilities in Belfast, Northern Ireland. With a lead of some 5 years over ts competitors and the world impressed by performance of this new form of civil air transport, the future of both DE HAVILLAND and the COMET seemed assured. The new jetliner was regarded internationally as "a feather in the cap for the British aviation industry". Suddenly the aircrafts spectacular worldwide success and Great Britain's enormous technological lead were placed in jeopardy when, on the morning of January 10th 1954, a BOAC COMET 1 (G-ALYP), en route between Rome and London, mysteriously exploded near the island of Elba whilst climbing through 27,000 FT, and with the loss of all 35 POB. As a result of this accident BOAC voluntarily grounded its entire COMET fleet for thorough engineering inspections. On the basis of "speculation only" a number of modifications were incorporated into each aircraft .... among which included reinforced shields between both the engines and fuel tanks, improved smoke and fire detection equipment, and greater safegauards against the accumulation of hydrogen. Confidence restored after this inexplicable tragedy, BOAC COMET 1 services were resumed on March 23rd 1954. Then on the evening of April 8th 1954 BOAC COMET 1 (G-ALYY .... on lease to SOUTH AFRICAN AIRWAYS) similarly exploded, near Naples, whilst climbing to cruising altitude during the Rome/Cairo sector of its scheduled service to Johannesburg and with the loss of all 21 POB. At parliamentary insistence the COMET 1 COA was immediately withdrawn, and developmental work on most future COMET models suspended, until the cause of the calamities could be positively ascertained. In the words of the late Sir Winston CHURCHILL ..."the cost of solving the COMET mystery must be reckoned neither in money nor manpower". Early speculation suggested sabotage, but, the Royal Navy's recovery of a significant proportion of the G-ALYP wreckage from the seabed over following months, and its thorough analysis, pathologist reports on the bodies recovered from both accidents, and later water tank testing of a COMET 1 fuselage (G-ALYU) by RAE scientists .... the cause of both disasters was eventually determined to have been the result of "metal fatigue and consequential explosive decompression". In the history of civil aviation, no commercial aircraft had ever previously operated at such great altitudes as those routine flown by COMET aircraft. Despite the most thorough flight testing program that could, at the time, be conceived, the aircraft had entered service with an unknown fatal design flaw. Forensic analysis proved (in the case of G-ALYP) that riveting around at least 1 of the aircrafts 2 square upper fuselage ADF window cut-outs had resulted in manufacturing defects which propagated minute cracking. These cracks advanced, progressively, throughout the aircrafts service life, as a result of the natural stresses imposed upon any aircraft structure through constant/repetitive pressurization cycles required to condition the cabin for greater PAX comfort during high altitude flight. This cracking had remained undetected despite regular mandatory maintenance and service checks on each aircraft and developed into a serious weakness, eventually compromising the aircrafts fuselage strength .... to the point where it was unable to withstand the typical loadings inflicted upon it during normal operating conditions. The fuselage then failed .... bursting catastrophically .... and resulting in complete destruction of the aircraft and all POB within less than 3,000 cycles. To what extent, if any, inflight turbulence might have precipitated the actual fatigue failure of both aircraft is a matter open to conjecture. No structural wreckage from G-ALYY was ever recovered due to the ocean depth where this aircraft was lost, but, post mortem results on bodies recovered from this accident confirmed the demise of this aircraft too had undoubtably originated from the same cause as which had afflicted G-ALYP. Post crash dry land testing of a COMET 1 airframe by the RAE scientists at Farborough, and further extensive flight testing by the RAF Experimental Flying Corp, also determined that stress concentration in the corners of the aircrafts squared/rectangular cabin window cut outs was in fact some 75% greater than De Havilland engineers had calculated. A subsequent court of enquiry into both disasters concluded that culpability could not be apportioned to anyone due to the pioneering nature of the COMET project. Whilst all due caution had been exercised throughout each stage of the aircrafts development, aerospace technology (of the time) had simply extended too far, and too rapidly, into (what was then) the unknown.
As a direct result of the 1954 COMET 1 disasters, suspension of the types operating certificate, and temporary closure of the production line, DE HAVILLAND lost the enormous technological lead it had gained over competitors. The great US aircraft manufacturers all benefited from the lessons learned from the COMET disasters and prospered accordingly as BOEING, COBVAIR/GENERARL DYNAMICS, DOUGLAS, SUD ESTE AVIATION, and even TUPOLEV began to vie for a slice of the potentially lucrative world market for civil jetliners .... which was first demonstrated by the British aircraft industry. Whilst the future of the COMET program was debated within Great Britain, valuable export orders for COMET aircraft intended for BCPA, JAL, LAV, NATIONAL AIRLINES, PANAIR DO BRASIL, PAN AMERICAN WORLD AIRWAYS were all cancelled. France's SUD EST AVIATION eventually acquired rights, from DE HAVILLAND, to use the entire forward fuselage section of the COMET in order to form the nose of its CARAVELLE jetliner which first flew on May 27th 1955.
COMET 1 & 1A aircraft were also known to suffer little margin for error during T/O and landing. This resulted in a number serious accidents occurring to BOAC, CPA, and UAT aircraft during the types early operational service. Whilst first attributed to "Pilot "Error" (over rotation), closer analysis of these accidents later proved that the wing design of early COMET models was particularly succeptable to suffering reduced lift when subjected to a high AOA .... and which also deprived the engines of vital airflow .... and power .... resulting in aircraft failing to accelerate to T/O speed and not then achieving sufficient lift to become completely airborne as a consequence of what was diagnosed as the ground stall phenomenon. Both COMET 1 & 1A aircraft were also criticized, by some crews, for their lack of "feel" and the over-responsiveness of their power controls. This particular failing was reasoned to have been one of a number of contributory factors involved with the loss of BOAC COMET 1, G-ALYV, near Calcutta with the loss of all 43 POB on May 2nd 1953 .... on what was ironically the first anniversary of the COMET's entry to service. These issues prompted aerodynamic and technical improvements being incorporated into later COMET models.
A single COMET aircraft (G-ALYT) was ordered by the MOS and built to upgraded specifications using heavier/more durable aluminum alloys .... designated COMET 2X .... to become the prototype COMET 2 which first flew on February 16th 1952. This aircraft also featured a 3 ft fuselage stretch, larger engine inlets, and increased fuel capacity for greater range. It was first used to flight test RR Avon 502 turbojet engines with greater thrust and improved fuel economy. The oval cabin window design later incorporated into COMET 4 was also first tested on this aircraft. Between 1953 and 1956 G-ALYT was also used by BOAC for route proving and for which it supported the airlines definitive period livery. In June 1956 the aircraft was returned to the MOS then used to test engine thrust reverser systems and successive versions of the RR Avon turbojet engines which were later incorporated into the COMET 4. This aircraft was eventually retired to RAF Halton on May 28th 1959 (re-registered 7610M) where it was used as a ground trainer until 1967 when it was eventually scrapped.
The definitive COMET 2 first flew on August 27th 1953 (G-AMXA) and was used by BOAC for route proving, further RR Avon powerplant testing, and general performance analysis. It was first demonstrated publicly at the 1953 Farnborough Air Show.
This aircraft also featured a resdesigned drooped wing leading edge along with each of the modifications first trialed on the COMET 2X. The COMET 2 initially featured the same flawed square PAX cabin window design of preceding COMET 1 & 1A models, but, as a result of forensic findings from the 1954 crash investigations, all COMET 2's produced were later reinforced structurally .... guaranteeing a service life of some 8,000 cycles. Production of some 36 COMET 2 aircraft had originally originally planned for BOAC but only 16 aircraft were ever completed prior to the types COA being withdrawn and suspension of production. Once modified these aircraft eventually became the first of the type to enter service with RR Avon turbojet engines. All COMET 2 aircraft had a fuselage length of 96.1 ft, a wingspan of 115 ft (with increased area), and were powered by RR Avon MK-117 and MK-118 turbojet engines rated at 7,300 lbs thrust each, These aircraft were certified for a MTOW of 120,000 lbs, and had capacity for up 48 PAX, and a range of some 2,535 miles. No COMET 2's ever entered revenue airline service. 2 other aircraft (G-AMXD, and G-AMXK) .... redesignated COMET 2E .... participated in further DE HAVILLAND performance testing between 1954 and 1957 (fitted with 2 RR AVON 524 turbojet engines rated at 10,500 lbs thrust each in the aircrafts outboard # 1 and # 4 positions, and 2 RR AVON 504 turbojet engines rated at 7,300 lbs thrust each in the inboard # 2 and # 3 positions) in support of both the French CARAVELLE and later COMET development, and which included trans-Atlantic route proving and familiarization on behalf of BOAC during May 1958 .... in advance of COMET 4 services. Both of these aircraft supported the definitive BOAC period livery. G-AMXD was transferred to the A&AEE for short range Decca X navigation trials from June 1958. This aircraft then entered service with the RAE (re-registered XN453) during February 1959 and was rebuilt as a radar, navigation, and communications laboratory and operated until its withdrawal from service on April 27th 1973. It was dismantled during 1977 and and used as an RFS trainer at Farnborough. G-AMXK was eventually acquired by the MOS during January 1960. Between February 1960 and October 1965 this aircraft was used by SMITHS INSTRUMENTS to test the performance of early flight control systems. In November 1966 it joined BLEU at Bedford (re-registered XV144) and was used to evaluate HUD equipment and also participated in early reduced visibility/blind landing experiments. Returning to RAE Farnborough during May 1971, this aircraft was eventually used for spares recovery and ground apprentice training, prior to being scrapped during 1975.
All COMET 2 aircraft produced were eventually pressed into RAF service following completion of their structural upgrading and stringent airframe testing .... redesignated C2, C2R (early unpressurized aircraft later used as Elint/Ferret Platforms), and CT2 (initial crew training aircraft later upgraded to C2 standard). These aircraft served AIR TRANSPORT COMMAND and other RAF divisions. The RAF's first C2 joined # 216 SQDN on June 7th 1956 (XK670). The COMET 2 remained in RAF service until April 1st 1967. 8 C2 aircraft later underwent floor strengthening for military air freight operations and were eventually recertified for a MTOW of 127,000 lbs but with capacity reduced to 44 PAX.
Beyond the setbacks which befell DE HAVILLAND and its original COMET design during the mid 1950's, and despite some calls for complete abandonment of the project following the disasters, the COMET was successfully re-engineered and later relaunched as COMET 4, 4B, and 4C aircraft of varying specifications and superior performance .... but .... that's all another story
Mark C
AKL/NZ
