On December 22, 1996, at 1810 eastern standard time, a Douglas DC-8-63, N827AX, operated by ABX Air Inc. (Airborne Express) impacted mountainous terrain in the vicinity of Narrows, Virginia, while on a post-modification functional evaluation flight. The three flightcrew members and three maintenance/avionics technicians on board were fatally injured. The airplane was destroyed by the impact and a postcrash fire. The functional evaluation flight, which originated from Piedmont Triad International Airport, Greensboro, North Carolina, was conducted on an instrument flight rules flight plan and operated under Title 14 Code of Federal Regulations Part 91.
The National Transportation Safety Board determines that the probable causes of this accident were the inappropriate control inputs applied by the flying pilot during a stall recovery attempt, the failure of the nonflying pilot-in-command to recognize, address, and correct these inappropriate control inputs, and the failure of ABX to establish a formal functional evaluation flight program that included adequate program guidelines, requirements and pilot training for performance of these flights. Contributing to the causes of the accident were the inoperative stick shaker stall warning system and the ABX DC-8 flight training simulator's inadequate fidelity in reproducing the airplane's stall characteristics.
Safety issues discussed in this report include airplane stall recovery procedures for functional evaluation flights, stall warning systems, fidelity of the ABX DC-8 flight training simulator, guidelines and limitations for conducting functional evaluation flights, and Federal Aviation Administration surveillance of air carrier functional evaluation flight programs. Recommendations concerning these issues were made to the Federal Aviation Administration.
As a result of the investigation of this accident, the National Transportation Safety Board makes the following recommendations:
To the Federal Aviation Administration:
Require Douglas Aircraft Company to review and amend the stall warning test procedures in the DC-8 maintenance manual and maintenance planning document to include regular calibration and functional checks of the complete stall warning system. (A-97-46)
Evaluate the data available on the stall characteristics of airplanes used in air carrier service and, if appropriate, require the manufacturers and operators of flight simulators used in air carrier pilot training to improve the fidelity of these simulators in reproducing the stall characteristics of the airplanes they represent to the maximum extent that is practical; then add training in recovery from stalls with pitch attitudes at or below the horizon to the special events training programs of air carriers. (A-97-47)
Ensure that ABX explicitly incorporates the revised functional evaluation flight stall recovery procedure (that was agreed upon in 1991 by ABX and the FAA), or an equivalent procedure, in its DC-8 functional evaluation flight program. (A-97-48)
Develop an advisory circular that provides guidance to air carriers on the appropriate conditions, limitations and tolerances for the performance of functional evaluation flights and the specific maneuvers performed during these flights, including approaches to stall. (A-97-49)
Identify the set of operations conducted by air carriers that require special consideration, including functional evaluation flights and other nonroutine operations that have similar needs for training and operational guidance; then amend air carrier operations specifications to include appropriate guidelines and limitations for these nonroutine operations and amend Subpart N of Title 14 Code of Federal Regulations Part 121 to require air carriers to establish appropriate flightcrew training and qualification requirements in their training manuals. (A-97-50)
Undertake an appropriate level of surveillance of the functional evaluation flight programs of all air carriers, following implementation of the Board's suggested changes to functional evaluation flight and other nonroutine operations. (A-97-51)
Modify the operating and airworthiness regulations of Title 14 Code of Federal Regulations or issue appropriate guidance material to clarify airworthiness and operational procedural requirements for conducting functional evaluation flights in transport-category aircraft. (A-97-52)
In addition, the Safety Board reiterates Safety Recommendation A-96-94 to the FAA:
Require that all transport-category aircraft present pilots with angle of attack information in a visual format, and that all air carriers train their pilots to use the information to obtain maximum possible climb performance.