Following the 8 January Air Midwest Beech 1900D crash in Charlotte, North Carolina, the US Federal Aviation Administration has issued an emergency airworthiness directive (EAD) concerning control rigging and simultaneously announced a review of its average passenger weight assumptions for small commuter aircraft.
The aircraft, with a full payload of 19 passengers and their bags, went out of control just after take-off, having pitched nose-up to a maximum of 52° (Flight International, 14-20 January).
The EAD says: "Recent ground testing and a review of the rigging procedures of the 1900D reveals that the elevator control system could be mis-rigged to restrict elevator travel if current maintenance procedures are not properly followed. It may appear to the crew that they have full elevator control column movement.
"However, the elevator may not have full travel. Such restricted travel may remain undetected until the aircraft is operated in a loading condition that requires full elevator authority to control the pitch."
The National Transportation Safety Board (NTSB) has revealed that, on the nine flights before the accident and after maintenance on 6 January, the aircraft's pitch control position sensor indicated about 10° down when the elevator deflection would have been near zero. The sensor is mounted under the cockpit floor and linked to the control column. Examination of the elevator control system revealed the tension-setting turnbuckle on the "down" cable was near full extension while that on the "up" cable was near full retraction. Typically they would be adjusted to about the same length, the NTSB says.
The FAA says its "weight sampling process" will carry on for 30 days, and its inspectors will carry out checks on about 30% of routes operated by commercial (Part 121) operators flying aircraft with 10- to 19 seats, weighing passengers and their bags to test the present assumption that adults weigh an average 82kg (180lb) and children aged two- to 12 average 36kg, with 9kg for carry-on bags.
Source: Flight International
