787 lightning protection
Dominic Gates at The Seattle Times had a long story Sunday (Feb. 8, 2009) about the Federal Aviation Administration relaxing rules on lightning strikes as too stringent and which the new composite Boeing 787 cannot meet.
The rules, adopted following the in-flight destruction of TWA Flight 800, a Boeing 747 (which crashed for reasons other than originating with a lightning strike), could not be met by other manufacturers, either, according to the Gates story. What we find eyebrow-raising is that the FAA proposes changing the rules to permitting only one system for lightning protection, abandoning the decades-long concept of redundancy for safety.
You have to read the Gates story for the details and why the FAA thinks this move is OK in the case of the 787.
But we’ll point out that there is a recent example of an aircraft design without a second back-up system leading to a fatal crash: Alaska Airlines Flight 261, when the McDonnell Douglas MD-83 lost control, inverted and crashed into the Pacific Ocean when the vertical tail’s jackscrew failed. This system controls the horizontal stablizer on the top of the T tail. Alaska, with approval of the FAA and Boeing (which by then had acquired McDonnell Douglas), changed suppliers for the grease and the maintenance interval for the jackscrew. This proved a mistake; the new grease wasn’t as durable as the old. Then the grease wore out, the jackscrew failed and because there wasn’t a second system, the flight crew lost control of the airplane. Everyone was killed in the ensuing crash.
Lightning strike protection has been a vexing issue for Boeing for several years. Gates wrote this story about Boeing’s challenges in 2006. In that story, and the one Sunday, fasteners play a key role in the concerns that lightning could ultimately result in igniting fuel in the tanks. As readers know, fasteners have been particularly troublesome for Boeing on the 787, for a variety of reasons unrelated to this issue. In 2007, former CBS anchorman Dan Rather, in his new job as anchor of start-up cable channel HDNet, touched on the lightning strike issue in a larger report about the safety of composite airplanes. The report was widely met with derision because Rather had recently left CBS under a cloud of credibility issues and he relied on a former 46-year Boeing employee who had been fired for the foundation of his report. We had this report at the time.
There is, of course, no benefit to Boeing to engage in shortcuts or crimp on safety. But we have to admit we’re concerned about having only one system and not redundant systems for lightning strike protection. The need for back-up systems was amply illustrated with the US Airways Hudson River landing. When both engines were damaged and essentially lost power–only a small amount of thrust remained after the bird strike, investigators now know–the RAT, or Ram Air Turbine, kicked in to provide power for vital controls. Back-up systems have been at the core of aviation safety. The FAA’s proposal to do away with them for the 787 is worrisome.
Update, February 11: Boeing provided a response to this entry, which we have posted in the comment section on its behalf. Please be sure and read Boeing’s comment.