Tuesday, July 1, 2003
Mechanics Under Fire
At two days of National Transportation Safety Board hearings on the Air Midwest Flight 5481 crash January 28, 2003, mechanics who worked on the ill-fated Beech 1900D were grilled about their actions during the airplane's final detailed inspection.
NTSB hearings are unpleasant, and it was clear at the Air Midwest hearing that party members had big problems, for example, with the use of contract mechanics, the way that on-the-job training was provided and required inspection items were signed off, and the way mechanics interpreted the Beech 1900 maintenance manual.
Oddly, only one witness was asked to testify about possible weight and balance problems with the flight, an FAA inspector. The remainder of the witnesses were asked strictly about maintenance issues, this despite the fact that the NTSB investigation has shown that the Beech 1900D was almost surely hundreds of pounds over maximum takeoff weight and that the center of gravity was well aft of the aft limit. An NTSB official told me that despite the apparent misrigging of the 1900's elevators, the airplane could have flown if the center of gravity were closer to the center of its range.
An area of focus was the Beech 1900 maintenance manual. The Air Midwest Detailed 6 inspection calls for checking cable tensions on the elevators. These were checked and found to be low, so an adjustment was made. The maintenance manual provided no specific procedure for tensioning elevator cables. The only procedure, found in 27-30-02, is to rig the entire elevator system.
What the mechanics did was comply with what they felt were applicable sections of the 1900 maintenance manual elevator rigging procedure. At the hearing, questioners called this "skipping steps," but the mechanics involved testified that that was the way it had always been done and they saw no reason to go through an entire rigging procedure just to adjust cable tensions. Nevertheless, they did sign off the work as having complied with 27-30-02, which means they were signing for having completed all the steps in the rigging procedure.
Another issue is that the mechanic doing the work had not been trained on the rigging procedure. Therefore, by regulation, he needed training before he could sign off the work. At the facility that did the work for Air Midwest, Raytheon Aerospace in Huntington, West Virginia, the inspector on duty that night provided the on-the-job training to the mechanic. But after receiving the training, the mechanic signed off for the work he had accomplished during training. Then the inspector who had trained the mechanic inspected then signed off the required inspection items. This brought up questions about whether this was a violation of the Part 121 rule on an inspector not being allowed to sign off required inspection items on which he or she performed maintenance.
It is too early to speculate about the exact cause of this crash, but NTSB data shows that the pilots had only about 30 to 40 percent of the normal forward elevator travel with the control wheel fully forward. The mechanics testified that they performed the tensioning procedures according to what they felt were applicable portions of the Beech 1900 maintenance manual, including using rigging pins and a travel board.
There was criticism of the Beech 1900 maintenance manual and its lack of a specific cable tensioning procedure. But none of the mechanics complained directly to Raytheon Aircraft, the airplane's manufacturer (which owns 20 percent of Raytheon Aerospace), about the manual. Instead, the mechanics said they normally would check with their supervisor if there was a problem interpreting a manual.
So far, this tragic crash has raised more questions that it has delivered answers. These include: Should operators (airlines in this case) provide inspection oversight for the companies that do their maintenance, instead of relying on inspectors employed by the maintenance company? Should mechanics receive more than just on-the-job training for new tasks? Should an inspector be permitted to give on-the-job training and not be permitted to sign off required inspection items for which he or she has just provided training? Should the FAA maintenance inspectors who monitor an airline be located near where heavy maintenance is done instead of at the airline's headquarters?
Unfortunately, like most accidents, this one will generate some NTSB recommendations to the FAA, a few changes in procedures, lawsuits and secret settlements, and bad memories. But I would be surprised if there were any substantial changes.