Fallout From This Accident Has Already Led to New FAA Procedures

The NTSB has issued an updated report on the January 8 crash of a Beech 1900, at Charlotte (NC):

The National Transportation Safety Board has released the following updated information on its investigation of the crash of Air Midwest flight 5481 (d.b.a. US Airways Express) a Beech 1900 (N233YV). The plane, carrying 2 crewmembers and 19 passengers, crashed shortly after takeoff on January 8, 2003, from Charlotte-Douglas International Airport, Charlotte, North Carolina. The following is a summary of factual information of investigative activities released thus far. Impact forces and fire destroyed the aircraft; there were no survivors. 

Flight Data Recorder

The FDR is a solid state recorder that provides 22 parameters of data. The data indicate that after maintenance to the aircraft on January 6, 2003, nine flights occurred before the accident flight. Information from the load manifests for flights before and after the maintenance have been obtained.

The FDR data show approximately a 10-degree down shift, as measured by the pitch control position sensor, on all flights after the maintenance including the accident flight. For the airplane to cruise at altitude, as it did on the nine flights after the maintenance, the elevator would have had to be near zero, but the pitch control position sensor indicated about 10 degrees down. Regarding the accident flight, pitch control position movement was recorded during the rotation for takeoff. A full-nose-down pitch control indication was recorded during the climb, and movement in the nose-up direction was recorded during the descent to the ground.

Investigators found that the sensor that indicates pitch control position was installed when the airplane was built. The sensor is mounted underneath the cockpit floor and is linked to the control column with a fixed control rod. In addition, a sensor to indicate elevator trim position was retrofitted on the airplane in February 2001. That sensor is located in the
wing box and measures movement of the elevator trim tab cable. Both sensors and connecting linkages have been recovered and preliminary examination does not reveal evidence of a jam.

Cockpit Voice Recorder

The CVR provides 30 minutes of audio information. All conversations regarding the airplane's ground operation, taxi, takeoff roll, and accident sequence were recorded. A discussion between the pilots regarding aircraft loading was captured.   A transcript of the recording will be released at a later date. 

Operations Group

The Operation Group determined that the accident crew flew this airplane on 6 of the 9 flights since the January 6, 2003 maintenance. Interviews of the other flight crews who had flown the accident aircraft following the maintenance were conducted. The pilots indicated no problems with the flight controls. Also, interviews were conducted with the gate and ramp agents who worked the accident airplane, and witnesses to the accident, and flight crews who had flown with the accident captain and accident first officer.

Systems Group

The Systems Group has retained from the wreckage the elevator control system cables, elevator control rods, bell cranks, and elevator counter balance weights. Examination of the elevator control cables revealed that the turnbuckle on the "down" elevator cable was offset to nearly full extension and the turnbuckle on the "up" elevator cable was near the fully retracted position, a difference of 1.8 inches. The turnbuckles are used to set cable tension and are typically adjusted to about the same length. 

The Systems Group, along with the Maintenance Records Group and a representative from the FDR Group, completed several ground tests in Wichita, Kansas, last week. The ground tests included a series of control column sweeps to collect data on the movement of the elevator. Various cable tensions and turnbuckle lengths were used during tests. Investigators are reviewing the results.

Other Activities

The Structures Group retained the cargo hooks from the wreckage to look for identifiable witness marks that will help determine if the hooks were attached at the time of the crash. The Powerplants Group plans to begin the teardown of the engines this week.  The inspection of the propellers is tentatively scheduled for next month. The aircraft Performance Group is gathering information for use in its engineering simulation of the accident flight and previous flights.

FMI: www.ntsb.gov/ntsb/brief.asp?ev_id=20030110X00049&key=1