pour être honnête , a part la période low/cost charter en DC10 pour UTA je ne connaissais Aéromaritime que pour l'exploitation des fameux Guppy d' Airbus Industrie.... et je ne savais pas ce que son passé ''était dans'' UTA dont ce fut une composante.
revenons donc au
Comet 1, cet avion mal né qui a accumulé sur les 22 exemplaires produits beaucoup de malheurs, rupture en vol de cellule (le ''fameux'' hublot ) et souci de profondeur destructrice. Sur les 6 accidents seul celui d' UAT Dakar - l'avion n'étant pas en cause, cette fois - n'entraina pas de pertes humaines...
Après le 6ème accident, affectant pour la troisième fois un appareil BOAC volant pour SAA, l'interdiction du Comet 1 fut décidée par les autorités anglaises et l'avion cloué au sol...
plus qu'un long discours, un bref résumé du début de carrière difficile de l'avion se trouve sur les fiches françaises (très zen) et anglaises de Wikipedia
http://fr.wikipedia.org/wiki/De_Havilland_Comet et
http://en.wikipedia.org/wiki/De_Havilland_Comet
quote wikipedia, donc : Early accidents and incidents
On 26 October 1952, a BOAC flight departing from Ciampino airport near Rome failed to become airborne and ran into rough ground at the end of the runway. Two passengers sustained only minor injuries, but the aircraft was a total loss.
The following March, a new Canadian Pacific Airlines Comet 1A (CF-CUN), being delivered to Australia, also failed to become airborne on takeoff from Karachi, Pakistan. The aircraft plunged into a dry drainage canal and collided with an embankment, killing all five crew and six passengers on board, the first-ever fatal crash of a jet airliner. Both of these accidents were originally attributed to pilot error: over-rotation had led to a loss of lift from the leading edge of the plane's wing. However, it was later determined that the wing profile led to a loss of lift at high angle of attack, and the engine inlets suffered from a lack of pressure recovery in these conditions as well. The wing leading edge was re-profiled, and a wing fence was added to control spanwise flow. A fictionalised investigation into these take-off accidents is a subject of the 1959 novel Cone of Silence by David Beaty, a former BOAC captain. Cone of Silence was made into a film in 1960, and Beaty also recounted the story of the Comet's take-off accidents in a chapter of his 1984 non-fiction work Strange Encounters: Mysteries of the Air.
The next fatal accident involving passengers was on 2 May 1953, when a BOAC Comet 1 (G-ALYV) crashed in a severe tropical storm six minutes after taking off from Calcutta/Dum Dum (now Netaji Subhash Chandra Bose International Airport), India,[1 killing all 43 on board. The crash was attributed to structural failure of the airframe. The break-up began with a stabiliser and may have been exacerbated by over-manipulation of the fully powered flight controls. The Comet 1 and 1A have been criticised for a lack of "feel" in their controls.[ However test pilot John Cunningham contended that "it flew extremely smoothly and responded to the controls in the best way De Havilland aircraft usually did"
Rome's Ciampino airport, the site of the first Comet hull loss, was again the origin of more disastrous Comet flights just over a year later. On 10 January 1954, 20 minutes after taking off from Ciampino, Comet G-ALYP ("Yoke Peter"), BOAC Flight 781, broke up in flight and crashed into the Mediterranean off the Italian island of Elba, with the loss of all 35 on board. There was no obvious reason for the crash, and the fleet was grounded while the Abell Committee met to determine potential causes of the crash. The committee focused on six potential problems: control flutter (which had led to the loss of the de Havilland Swallow), structural failure due to high loads or metal fatigue of the wing structure, failure of the powered flight controls, failure of the window panels leading to explosive decompression, or fire and other engine problems. The committee concluded fire was the most likely cause of the problem, and a number of changes were made to the aircraft to protect the engines and wings from damage which might lead to another fire.[12]
During this investigation, the Royal Navy conducted recovery operations, including the first use of underwater television cameras. The first wreckage was discovered on 12 January and the search continued until August, by which time 70 % of the main structure, 80 % of the power section, and 50 % of the equipment had been recovered. The forensic reconstruction effort was only lately underway when the Abell Committee reported their findings. On 4 April, Lord Brabazon wrote to the Minister of Transport, "Although no definite reason for the accident has been established, modifications are being embodied to cover every possibility that imagination has suggested as a likely cause of the disaster. When these modifications are completed and have been satisfactorily flight tested, the Board sees no reason why passenger services should not be resumed." Comet flights resumed on 23 March 1954.
Then on 8 April 1954, Comet G-ALYY ("Yoke Yoke"), on charter to South African Airways, was on a leg from Rome to Cairo (of a longer flight from London to Johannesburg), when it crashed in the waters near Naples. The fleet was immediately grounded once again and a large investigation board was formed under the direction of the Royal Aircraft Establishment (RAE). Winston Churchill tasked the Royal Navy with helping to locate and retrieve the wreckage so that the cause of the accident could be found.
Engineers subjected an identical airframe, G-ALYU ("Yoke Uncle"), to repeated re-pressurisation and over-pressurisation and after 3,057 flight cycles (1,221 actual and 1,836 simulated), Yoke Uncle failed due to metal fatigue near the front port-side escape hatch.[13] Investigators began considering fatigue as the most likely cause of both accidents and initiated further research into measurable strain on the skin. Stress around the window corners was found to be much higher than expected, "probably over 40,000 psi," and stresses on the skin were generally more than previously expected or tested. This was due to stress concentration, a consequence of the window's square shape.
The problem was exacerbated by the punch rivet construction technique employed. The windows had been engineered to be glued and riveted, but had been punch riveted only. Unlike drill riveting, the imperfect nature of the hole created by punch riveting may cause the start of fatigue cracks around the rivet.
The principal investigator concluded, "In the light of known properties of the aluminium alloy D.T.D. 546 or 746 of which the skin was made and in accordance with the advice I received from my Assessors, I accept the conclusion of RAE that this is a sufficient explanation of the failure of the cabin skin of Yoke Uncle by fatigue after a small number, namely, 3,060 cycles of pressurisation."[14]
Before the Elba accident, G-ALYP had made 1,290 pressurised flights and at the time of the Naples accident, and G-ALYY had made 900 pressurised flights. Walker said he was not surprised by this, noting that the difference was about 3 to 1 and previous experience with metal fatigue suggested a total range of 9 to 1 between experiment and outcome in the field could result in failure. Thus, if the tank test result was "typical," aircraft failures could be expected at anywhere from 1000 to 9000 cycles. By then, the RAE had reconstructed about ⅔ of G-ALYP at Farnborough and found fatigue crack growth from a rivet hole at the low-drag fiberglass forward "window" around the Automatic Direction Finder, which had caused a catastrophic breakup of the aircraft in high altitude flight.
The square windows of the Comet 1 were redesigned as oval for the Comet 2, which first flew in 1953. The skin sheeting was thickened slightly. The remaining Comet 1s and 1As were either scrapped or modified with oval window rip-stop doublers and a program to produce a Comet 2 with more powerful Avons was delayed. All production Comet 2s were modified to alleviate the fatigue problems and most of these served with the RAF as the Comet C2. The Comet did not resume commercial airline service until 1958, when the much-improved Comet 4 was introduced and became the first jet airliner to enter transatlantic service. The Comet nose section was also used on the Sud Aviation Caravelle. As is often the case in aeronautical engineering, other aircraft manufacturers learned from and profited by de Havilland's hard-learned lessons.[15] According to John Cunningham, representatives from American manufacturers such as Boeing and Douglas "admitted that if it hadn't been for our problems, it would have happened to one of them".[6]
comme dans l'histoire du Comet, qui ne vola plus de 1954 a 1958, nous allons faire une pause et revenir avec le Comet 4, avion qui a volé jusqu'en 1997 et continue, sous sa livrée militaire ''Nimrod'' d operer aujourd hui aux couleurs de la RAF
