Food For Thought

Alert reader Lee Gaillard offered a few thoughts on our recent coverage of aging jetliner inspections (see ASW, Dec. 16, 2002) and on fuel tank inerting (see ASW, Dec. 23, 2002): On older jet inspections: "Perhaps the term "fatigue cracking/corrosion" should be used instead of just fatigue...

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Alert reader Lee Gaillard offered a few thoughts on our recent coverage of aging jetliner inspections (see ASW, Dec. 16, 2002) and on fuel tank inerting (see ASW, Dec. 23, 2002):

On older jet inspections:

"Perhaps the term "fatigue cracking/corrosion" should be used instead of just fatigue cracking. They are inextricably linked. Once there is any crack, internal metallic surfaces are exposed to 1) oxidation, 2) moisture, 3) other pollutant gases...and corrosion begins and accelerates. Even aluminum alloys oxidize (emphasis in original).

"I suggest inspection times be cut in half on all repaired structures. Any repaired structure has been subjected to the stresses that required repair in the first place, and repair process itself introduces new avenues of failure/fatigue in that something usually gets bent, drilled, etc., as part of the repair process. And sometimes those repairs are improperly done: see Boeing 747 repair to aft pressure bulkhead of Japanese airliner following tailstrike - with faulty repair resulting in decompression, loss of aircraft control, and loss of 500+ lives.

"Regarding the inspections mandated by the FAA: how about not having either airline or manufacturer do the inspections - fox in chicken coop. Instead, the FAA could set up its own inspection centers, similar to state auto inspections. Eliminates conflict of interest, places responsibility squarely on the FAA."

On inerting:

"Why all the fancy nitrogen extraction systems? How about just tanks of pure compressed nitrogen or argon (used commercially to inert welding systems for titanium, etc.) whose release is triggered automatically as fuel is drained out and tank pressure drops? The conceptual 160-lb. system offers a 12% oxygen concentration in the tank vs. 20% in straight air. Not much of a benefit! And even the 2000-lb. system would save weight because carrying extra fuel to cover the pumps would no longer be necessary."