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Aviation History
1960
1960 - 0697.PDF
LIGHT, 20 May 1960 697 are tall tails from Boeing, for Varig, Lufthansa, OAC and Western. By contrast the PanAm tcraft in the background is unmodified. First >ree in the line are all Rolls-Royce Conway- jwered 707-420s; BOACs aircraft here is temporarily Boeing-registered N5091K AIR COMMERCE £18M ELECTRA PROGRAMME T AST week the Lockheed Aircraft Corporation issued a statement*-> attributing the two Electra mid-air disintegrations* to "unpre- dictable and abnormal flutter." In both cases a wing broke off afterfluttering at three cycles a second. J. F. McBrearty, assistant general manager of Lockheed's Cali-fornia division, says: — "In our opinion the accidents resulted from dynamic coupling at highspeed of oscillatory movements of the outboard power pack nacelle and the wing. All our tests and calculations substantiate the conviction thatsome element of damage existed in the powerpack nacelle area of both Electras prior to their accidents. This damage by itself could not havecaused destruction, but the combination of broken or weakened elements plus the external forces intensified by high speed built up the forces tothe breaking point. Modifications are under way which will preclude the possibility of such a coupling of forces . . . All tests and supportingcalculations show that the low_ speeds at which Electras are now flying will prevent a repetition of this phenomena, and all chance of a recur-rence of dynamic coupling at higher unrestricted speeds will be eliminated under the modification programme." Some 250 Lockheed engineers and technicians worked virtuallyday and night on what the manufacturer describes as "one of the most profound engineering problems that has confronted our com-pany in three decades." A model of the wing, power units and nacelle structure was built and tested in the Lockheed wind tunnel.It displayed normal stability at all speeds and against external disturbances, including gusts, while the structure was undamaged.The stiffness and bending strength of the combined nacelle and power unit were then gradually reduced, permitting an excessivemovement up and down as well as sideways, to simulate the effect of structural damage "such as might result from an abnormallyhard landing." Under such conditions a point was finally reached in which the weakened model began to oscillate and becomeunstable. The movement continued and set up similar oscillation of the wing. Lockheed say that in an Electra without a damagedpart in the power unit and nacelle area oscillations would damp out or disappear but when the structure was damaged they would * September 1959, Braniff Electra near Buffalo, Texas: 23 passengersand six crew killed; March 1960, Northwest Electra near Tell City, Indiana: 56 passengers and six crew killed. continue unchecked. "In the case of the two accidents theyincreased by combining or coupling." Design change proposals along with other modifications "notconnected with the accident but normal product improvements" are shortly to be submitted to the FAA; after Agency approvalthey can be carried out in the field to the 145 Electras now in service. This work could begin in July. Summing up the Electra investigation for the record, it wasevident from early wreckage analysis of the two mid-air dis- integrations that wing failure had been a primary cause. Immedi-ately after the second accident the FAA imposed a speed limitation of 275kt i.a.s. at cruising height; on March 26 thiswas further reduced to 225kt—an 80-100kt penalty. US Electra operators concerned (Eastern, American, Braniff, Northwest,Western, National, Pacific, Southwest) are reported to have suffered, in varying degree, loss of business. The Lockheed investigation, which has been reminiscent inscale and intensity of the Comet 1 investigation in 1954, involved air tests of the prototype which was flown "very close to thedesign limits." Lockheed test pilots and engineers flew the air- craft into areas of extreme turbulence over the California moun-tains, putting the aircraft through high g manoeuvres at various weights and speeds. In addition, a Northwest Electra with aboutthe same flight time as the aircraft that crashed on March 17 (reportedly less than lOOhr) was thoroughly inspected. Alsoparticipating in the programme were Allison, Aeroproducts and, in addition to the FAA, the NASA. The cost of the investigationis reported to be about $25 million (nearly £9 million). That figure was given on April 19; on May 12 Robert Gross, Lockheed's chair-man, estimated that the cost of the modification programme would not exceed $25 million—i.e., about the same amount again, a totalequivalent to about £18m. These heavy costs will presumably be borne by the manufac-turers, and they are in addition to the expensive engine tilt-up programme found necessary a year ago to eliminate severe vibra-tion. The cost of those modifications is not certain; but when added to the recent costs it is probable that Lockheed are still someway from breaking even on the Electra programme. HONG KONG FOR NORTHWEST TT now appears probable that Northwest Airlines- will be grantedA their long-sought demands, hitherto always firmly resisted by the British Government, for an extension of their US - Tokyoservice to Hong Kong. A report from Washington says that the British delegation "is believed to have conceded this in principle."At the same time, the State Department is reported to have been asked to "defer to a later date" TWA's request for beyond-rightsfrom London—another highly controversial point at issue since 1956 between the civil aviation authorities of the two countries. Meanwhile negotiations are said to be continuing on Eagle'srequest for rights between the Bahamas and Palm Beach and Fort Lauderdale. This airline's Viscounts already connect Nassau withMiami; but, due to the vigorous resistance of the US carrier Mackey, it has so far been unable to link the Bahamas with theother two Florida resorts. The difficulty here is partly one of getting the Americans to agree to "double designation," sinceEagle's British competitor Bahamas Airways already serves the points concerned. Another agreement in principle is reported to be that BWIAare to be designated as the carrier to run non-stop services between New York and Jamaica, rights now enjoyed by PanAm. THE BILL IN THE LORDS SECOND skimming rather than second reading might be a fairway to describe the consideration given by the House of Lords to the Civil Aviation (Licensing) Bill last week. The best featureof the lhr 20min debate was the summary of the main points and purpose of the new legislation by the Paymaster General, LordMills. As a concise account of Britain's proposed new civil aviation legislation it can be highly recommended.Unfortunately, subsequent speakers offered no fresh thoughts of any depth: one noble lord, a Labour Government Minister ofCivil Aviation a decade ago, did not "quite see the point that the Air Transport Licensing Board should have the general duty offurthering the development of British aviation"; he thought this was the duty of the Ministry. He also thought that "jet-sustainedwingless vehicles" which would be "driven along the road when necessary and taken up into the air when necessary," would "altercompletely the whole situation so far as air transport is concerned." He also complained about the lack of air ferry services betweenWales and Ireland, and the neglect of Rhoose Airport. But few specific criticisms of the Bill were offered, and it was a pity thatLord Terrington, because he is chairman of the ATAC, could not contribute. The Bill will now be considered in committee.
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