Air Force, McDonnell Say C-17 Test ‘Unclear’

The Air Force and McDonnell Douglas on Monday attempted to put the best face on the possible failure of the C-17 cargo jet to pass a key test of the maximum structural loads the plane would encounter in flight.

If the aircraft in fact failed the test last Friday, it would add to an already long list of technical and cost problems that have hindered the Long Beach-based program. The Pentagon is evaluating whether to cut back or kill the $44-billion program.

The left wing of the plane buckled at 145% of its maximum load, short of the 150% requirement. At the moment it broke, the wing was being bent upward 12 feet, 1 inch with powerful hydraulic jacks.

But Air Force and company officials said Monday that the wing may have passed the test because it appeared that the damage occurred to a part of the wing near the tip that had reached the 150% load requirement.

A carefully worded statement by the Air Force said it was “unclear” whether the wing meets the contract requirement.

“We know it was close,” McDonnell spokesman Larry McCracken said.

If the Air Force elects to pass the wing, it is likely to trigger more controversy. Rep. John Conyers (D-Mich.), a critic of the C-17, and his staff immediately condemned the suggestion that the aircraft passed the test.

The Air Force said it has appointed a team of experts to study the matter and issue a report in one month. The team is the same one the Air Force convened last year when the C-17 failed the first strength test. In that case, the wing broke at 128% of its design limit.

The latest test was conducted after McDonnell redesigned the wing and installed about 840 pounds of additional metal for strength. The advent of computerized aircraft design has enabled engineers to more precisely determine flight loads and has made this kind of failure unusual in the aircraft industry.