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Aviation History
1989
1989 - 0334.PDF
Boeing backs new FAA checks by John Bailey in Seattle and Julian Moxon in Washington D.C. Boeing has denied that the latest US Airworthiness Direc tive (AD) concerning its aircraft is an indictment of its quality control, and stressed the part it played in drawing up the regu lation. The AD is unprecedented in covering a major manu facturer's entire airliner output over an extended period. It calls for examination within 25 days of the fire/overheat detection and suppression systems for the engines and cargo holds of all models delivered since Decem ber 1980: 741 aircraft are affected—472 737s, 33 747s, 123 757s, and 113 767s. Check ing takes 2-4 hours. Two days after the AD was announced, new cases of engine fire-suppression system cross- wiring were found. These affected four Boeing 737-300s in Australia. Three Australian Airlines aircraft and one from Ansett were involved. The carriers found the faults during checks prompted by the British Midland Airways 737 crash. The Australian Civil Aviation Authority says: "If the pilot had ever needed to extinguish fires in both engines at the same time, then the extinguisher in the second engine would have applied only half its extinguish- ant to the second fire". The Authority ordered similar checks on all Boeing types oper ated in Australia, which are to be completed within 25 days. This involves 27 737s, 26 747s, and 25 767s. The US instruction was issued after four more aircraft were found to have wiring faults. They were: crossed elec trical wiring on a 757 system which warns of engine over heating and low pressure in the fire extinguisher bottle, "which would indicate overheat in the wrong engine"; reversed wiring on a 757 extinguisher, "which would cause discharge to the wrong engine"; an incomplete circuit to a 757 extinguisher bottle, "which would prevent discharge of the extinguishant"; and reversed wiring on a 737-300 extinguisher "which would cause discharge to the wrong engine". The FAA does not mention the carriers involved, but Flight understands that they include Delta, Royal Air Maroc, and Royal Brunei. The AD is the fourth this year involving crossed-wire checks on Boeing aircraft. The first, on January 11, required checks for potential crossed wiring in the engine fire detection and vibration monitoring system on 737-300, BMA 737 crash: wiring by Kieran Daly British investigators are now almost certain that crossed wiring played no part in the British Midland Airways (BMA) 737-400 crash near East Midlands Airport. Although wiring checks were ordered after the acci dent, the UK authorities never said they had actually found a fault, and Flight has learned that the theory is now largely discounted. If confirmed, the news will be a relief to Boeing. Boeing's manager at the Renton plant, Jim Johnson, says: "We have not had any official input, but we have heard several unofficial reports that they have seen enough of the wiring and they have not fount any discrep ancies in the wiring". Flight also understands that the port General Electric/ Snecma CFM56-3C1 engine was found to have severe fan blade damage, and that the investigators are uncertain of the cause. Pieces of blades were found on the approach to East Midlands, and contamination of the engine by foreign objects or ice is being considered. BMA flatly denies rumours that the engine had a history of excessive vibration. However, 737 crews are known not to think highly of the new flat- panel electronic engine vibration instruments in the cockpit, and view readings of up to 4 on a scale of 0-5 with scep ticism. It is still uncertain why the crew shut down the starboard engine. Flight understands it is and -400s. Two days later, another called for crossed-wire checks on the 757 cargo-bay fire protection system, and a third, on January 19, ordered similar checks on Boeing 767 fire protection systems. The latest instruction covers aircraft which have not been found with crossed wiring; notably the 747 range. The FAA says: "We are trying to be somewhat anticipatory to get ahead of the situation. It is more efficient for everyone to get these things done in one comprehensive AD." Boeing says that unaffected models Boeing 767's under construction at the company's Everett works, Seattle m W.sJ L Is i TIHHI lltfeM^S include the 737-100, 747SP, 747-100, some 747-200s, and new 747-400s. Jim Johnson, vice-president and general manager of Boeing's Renton division, which assembles the narrow- bodied 737 and 757, tells Flight that the latest AD was initiated jointly by Boeing and the FAA. Johnson says: "In our discussion with the FAA about the incidents which were reported, we said that our manufacturing procedures in our factories and our design procedures were common enough across our fleet of aero planes that it was prudent to examine other aeroplanes. "So we said that, instead of a piecemeal examination, let's write an AD that addresses the whole issue. We actually wrote the instruction for the AD because the regulatory agencies do not have that experience; all of the examination has to be done in concert with our main tenance manuals at periodic checks, he adds." Johnson says that Boeing has changed its procedures follow ing the latest faults. He says: "We were doing electrical continuity checks on the 757 cargo-compartment fire sup pression systems in the factory, but installing the extinguisher bottles out on the flight line. We were doing this for a perfectly valid reason, which was that the bottles are fully charged and we did not want them rattling around inside the aeroplane during the assembly process, but now we have decided that 4 FLIGHT INTERNATIONAL, 11 February 1989
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