AARON KARP / WASHINGTON DC
Maintenance and loading problems were the primary factors in the 8 January crash of an Air Midwest Raytheon Beech 1900D in Charlotte, North Carolina. At last week's public hearing, US National Transportation Safety Board investigators focused on maintenance performed the night before the accident, which occurred just after take-off, killing all 21 people on board.
Air Midwest contracts out its 1900D maintenance work to Raytheon Aerospace, which uses temporary contract mechanics. Overnight maintenance was performed on the aircraft by Raytheon at Huntington, West Virginia.
Mechanics determined the aircraft's elevator pitch-control cable tension was out of specification and adjusted the cable turnbuckles. George States, Raytheon inspector in charge, instructed a contract mechanic undergoing on-the-job training how to perform the task and later approved the work.
"We didn't bypass steps to do the cable tensions," says States. "Tensioning the cables is pretty straightforward for a licensed mechanic." But NTSB lead investigator Lorenda Ward says: "Examination of the pitch-control system components [recovered from the accident aircraft] indicated that the pitch-control cable turnbuckles had been adjusted to an abnormal position."
This made the aircraft more difficult for pilots to handle, say investigators. "The control column was rigged further forward than normal while the elevators remained at neutral," says Ward. "From this position, the control column can be moved only slightly more forward before hitting its stop, thus its range of motion is severely limited."
Pitch control problems were complicated by the aircraft's heavy weight at take-off, says Ward. "If the aircraft is loaded so that the CG [centre-of-gravity] is forward of the forward CG limit, available pitch control may not be sufficient."
Under Air Midwest's new weight and balance programme, it "would have had to offload a combination of passengers, bags or fuel to bring the weight and balance [of the accident aircraft] into the [now] approved envelope", says Ward (Flight International, 13-19 May).
Source: Flight International
