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Aviation History
1960
1960 - 0219.PDF
FLIGHT, 12 February 1960 219 AIR COMMERCE Comet Reliability THE BOAC engineering department claims that "there hasbeen less trouble keeping the Comet fleet serviceable thanwith any other new type which the corporation was the firstto operate." No restriction of any kind affecting performance was imposed during the first year of operation, according to informa-tion released by the manufacturers. The table below lists the 19 worst cases of recurrent trouble which have been the subjectof modification action. The term recurrent is, say de Havilland, strictly interpreted as meaning more than once: for example,the nosewheel steering bracket failure (item 1) occurred only twice and remedial action was under way before the second failure.There have been no recurrent failures in the tail unit or in the hydraulic power or flight controls. Regarding the latter, thesecondary control system has been put into operation on only two occasions, whilst the reserve control system has not yet beenused. During the first 12 months of Comet operation no aircraft was ever taken out of service for modification, such work alwaysbeing absorbed during the routine maintenance cycle. So far as the engines were concerned, there were ten cases of"airborne ingestion." Four of these involved ice from the front washroom, a trouble which is being put right; one, involving twoengines, was caused by trees; and the others were caused mainly by birds. The following data on unscheduled Rolls-Royce AvonRA.29 removals from BOAC's Comet 4s, published by de Havilland, cover the 12 months since services began inOctober 1958: Ingestion while airborne, 10; ingestion from runways, 2; Continued overleaf) Structure [or System Moin Division 1. Fuselage 2. Wing 3. Electrical System 4. Air Conditioning and Pressurization 5. Undercarriage 6. Instrumentation 7. Fuel System 8. Fire Protection 9. De-icing 10. Galley and Water System Component Giving Recurrent Trouble Windscreen Panels Nose-wheel Undercarriage Front Spar Half-rings Fuel Leaks Flap Torque link bolts Split Flaps Alternator Alternator Fuel System Actuator Altitude Selector Cold Air Unit Brakes Tyres Fuel Contents Indicator Fuel Flowmeter Refuelling Pipe Coupling Fire Warning System Non-return Valves Water Servicing Valves Nature of Trouble Various defects including fusing of gold film layer* and delamination Steering jack attachment bracket lugs fractured Cracking of rings at spar boom attach- ments Leaks mainly on leading edge, caused by effect of de-icing hot air on the sealant Bent when maladjusted Damaged by water spray when landing on flooded runwaysf Power failure caused by extreme tropical rain increasing water content of cool- ing air above acceptable maximum Earth fault on rotor Corrosion because of ingress of moisture caused by differential pressures Control of rates of cabin altitude change not to desirable standard Bearing failures Undue wear Adverse effects of condensation§ Incorrect integrating action Unable to accept shock pressure Various Instability caused breakage in two cases preventing complete shutting off of system in one wing§ Freezing caused some delays during tran- Action Taken (a) Modification to bus-bar feeding gold film to eliminate hotspots (b) Further manufacturing improvements in hand. Manufacturer's tests and panels in service have already demonstrated improved per- formance Bracket strengthened Modification of design and bolting technique, to obviate possibility of built-in stresses Different type of sealant substituted to withstand the de-icing air temperatures Bolts strengthened and centralized Flaps strengthened to withstand this type of damage. Behaviour of modified flaps is under observation Shroud fitted over brush gear and slip rings. Tests have shown satis- factory operation Modification of rotor windings Modification to introduce corrosion-resistant materials and breather. Tests have demonstrated satisfactory behaviour under representative aircraft conditions. Modification embodiment proceeds Modification and refinement, introducing variable rate-of-change con- trol, has achieved improved performance Service trials with modified units continue, with satisfactory results so far Forced air cooling being introduced to reduce consequent temperatures of tyres and hydraulic fluid. Brakes now satisfactory Maxaret mountings revised to ensure adequate spin-up on touch-down Modifications introduced to seat connections and tank units to minimize Modification action taken on transmitter and indicator Modification to all couplings prevents disconnection Minor modification to components and installation to avoid Firewire fouls and relay overheating New type valve introduced which on manufacturer's tests has demon- strated an improved performance Modification action re-positioned valves to warmer areas. Has cut delays by 90 per cent * Gold film layers between windscreen laminations are an innovation and defects which have occurred may be regarded as an extension of the complete developmentof the component, t Recent occurrence. § Recent occurrences. N.B. This record covers the period November^1958 to October 1959. WEST INDIES TEST MATCH ! A TEAM of five Ministry of Aviation officials will represent thei l *• British side in the forthcoming talks with the Americans in t Barbados to review the 1946 Bermuda agreement relating to air| services between UK and US territories. The background to this [ meeting, which will start on February 24 (and which mav last\ about ten days), was discussed in Flight for January 1—"From ! Bermuda to Barbados." I The MoA team will be led by Mrs Alison Munro, and it willcomprise A. V. Davies (recently concerned with the Brazilian discussions). D. E. J. Dowler, D. N. Miller, and E. I. R.McGregor, UK civil air attache in Washington. Representatives ot BOAC will be in attendance (since the conflicts to be resolvedonmarily concern them), and no doubt the West Indies Federa- tion s interests will be represented also. QUICK REPAIR JOB THE BOAC Comet 4 which made a wheels-up landing at RomeA on December 23, G-APDL, is now back in service. A BOAC w°™nS Party, assisted by a team of de Havilland service and Production engineers, repaired the damage at Rome in 45 days-no mean achievement, and a tribute to the crash-landing charac- teristics of the buried-jet Comet which should have impressed theunderwriters. The cause of the accident, which involved no casualties, is understood to have been attributed to crew error.The damage was mainly to the centre section and stub wings, and to a lesser extent to the fuselage. The undercarriage doorsand the engine cowling doors had to be renewed, and one pod tank and the inboard flaps were replaced. All the engines werechanged, the originals being removed for inspection for possible shock-loading damage. POTENT POTEZ , i FOR several years the French Societe Henry Potez has made noaircraft of its own design (apart from the prototype Potez 75). But, as already reported, the company now hope to stage a come-back with a very attractive light transport designated Potez 840. Looking rather like a hotted-up Heron, the 8-40 will providepressurized accommodation for from 16 to 24 passengers and will be powered by four Turbomeca Astazou turboprops each ratedat 436 h.p. and driving Ratier-Figeac propellers. A one-sixth- scale powered model will go into a tunnel this summer, and thefirst prototype is to fly at the end of December. The following specification has just become available: — Span, 63ft 7in; length, 50ft lin; height, 17ft; wine area, 377 sq ft;basic operating weight, 8,8001b; gross weight, 16,7601b; fuel capacity, 352 Imp gal; take-off run, 1,150 to 1,380ft; runway length (CAR4b),1,770 to 2,100ft; initial climb, 2,040ft/min (l,260ft/min with one engine out); mean cruising speed, 311 m.p.h.; range, 311 to 932 miles.
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