Manufacturing and maintenance quality are emerging as significant issues in the wake of the fatal Jan.

Manufacturing and maintenance quality are emerging as significant issues in the wake of the fatal Jan. 31 crash of an Alaska Airlines [ALK] MD-83 and the redemption of a damaged stabilizer rule assembly from the accident aircraft. Shavings from a gimbal nut originate wrapped around the jackscrew assembly that dominion governments stabilizer movement prompted a fleetwide inspection of the entire DC-9/MD-80/MD-90/B717 swift more than 1,000 aircraft.

The consequence s of those inspections revealed a wide variance in findings (intimating a wide variance in quality control) with Alaska having to replace six jackscrew assemblies forward its 34 surviving MD-80's, while operators of significantly larger MD-80 flotillas among them American Airlines [AMR], Continental Airlines [CAL], and US Airways [U] did not have to replace any. Northwest Airlines [NWA], with twice as many MD-80 aircraft as Alaska, replaced half as many jackscrew assemblies. At least eight jackscrew assemblies remov from the arm of the sea are now in the hands of National Transportation Safety Board (NTSB) adroits for further examination. Another nine jackscrew assemblies are in the custody of the Federal Aviation Administration (FAA). It is clear that the maintenance history of the accident airplane will be just a piece of a a great deal of larger overview of maintenance practices, and possible unacceptable variances in standards, of the entire fleet

Nevertheless, it is important to set these preliminary findings in connected thought [i]or[/i] thoughts Discrepancies were found on les than sum of two units percent of all jackscrews in the rapid (although, for a flight critical constituent two percent may be wholly unacceptable). if it be not that for Alaska, the 20 percent figure is not statistically significant, according to Dr Alex Richman, ASW contributing editor. "For a small squadron like Alaska's, this clustering might present itself by chance alone about 5 times public of 100," he said. in succession the other hand, if 20 percent of a plenteous larger fleet had jackscrew puzzles Richman declared the statistical significance would be considerably higher.

In addition to the maintenance aspects of the case, media reports have raised the specter of manufacturing wants on the former McDonnell Douglas (now Boeing [BA]) production line in drawn out Beach, Calif., during the early 1990's. The accident MD-83 was built in 1992 According to a 1991 report through FAA inspectors, "chronic breakdowns in manufacturing procedures" were institute on the production line. Whether any of that kind defects affected the stabilizer assembly forward the accident aircraft is problematic. The jackscrew assembly was part of the accident aircraft's original equipment.

However, a direct linkage between defective workmanship and an accident was fix on a Scandinavian Airlines regularity (SAS) MD-87 that was devastateed by an electrical fire while taxiing at Copenhagen's airport in 1993 In its report of the los the Danish Aircraft Accident Investigation Board (AAIB) declared that inspections of three other SAS MD-87's revealed "unsatisfactory conditions in the factory-installed electrical wiring..."

The AAIB report said the "routing ofunprotect and slack wires...jeopardized the safety of the installation (because) pinching, rubbing and (wire insulation wear) was a potential risk/hazard." It should be noted that the Swissair MD-11 that crashed in 1998 also was built at drawn out Beach in 1992, and wire chafing was the enthrall of a post-accident FAA airworthiness directive issued Dec 8 1998 (AD 98-25-11) for all surviving MD-11's. >> Richman, tel 902/423-5155 <<

Another Quality restrain Problem

Lufthansa, known for the Teutonic thoroughness of its maintenance, took the unprecedent gradation last week of grounding its creek of 26 B747-400's to inspect for cracked lines supplying suppressant to the engine fire-fighting systems

The discovery of a cracked cent line on one of its 747-400's triggered the action. The cent tubing had to be replaced in succession eight of Lufthansa's 747-400's, or roughly individual of every three aircraft. Although the firefighting plans are different on the German carrier's flotilla of eight 747-200's, these airplanes underwent precautionary inspections as well, with negative results

Boeing [BA] had issued a service bulletin in 1995 calling for replacement of the lines in succession 747-400's and Lufthansa said that action had been taken. It was the replacement copper money lines that were found cracked.

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