A McDonnell Douglas DC-9-32 was in the initial climb out of Greensboro/High Point-Piedmont Triad International Airport (North Carolina, USA) and was heading for Atlanta-William B. Hartsfield International Airport, on this day in the year 2000, (Georga, USA). On board the 30-year-old aircraft, a crew of five and 58 passengers for the short (500 km / 270 nm) flight.
The forward fuselage after the aircraft was tripped for parts
(Source baaa-acro.com © J.R. Covington, Jr)
The crew noticed the smell of smoke in the fligthdeck and immediately donned their oxygen mask and smoke goggles. ATC was contacted and an emergency was declared, an immediate return to the field was requested and granted. Smoke was also seen in the forward cabin. Although the dense smoke was hindering the visual cues for the flight crew, a safe landing was made a short while after declaring the emergency. An emergency evacuation was initiated as soon as the aircraft came to a stop. All occupants evacuated the aircraft. although several (light) injuries were sustained;
three crew members
The National Transportation Safety Board was alerted, and an investigation was launched. Examination of the airplane revealed severe smoke and heat damage around the electric power center (EPC) and within the cockpit. Removal of the forward and aft EPC panels revealed heavy sooting, melted wire insulation, visibly broken wires, and localized heat damage. The lowest point of the fire damage on the cabin (aft) side of the EPC was in the upper compartment where it was noted that the aluminium stanchion brace that runs the length of that compartment was destroyed along with the AC bus feeder wires and numerous other airplane wiring bundles. No fire damage was noted in the lower aft compartment. The lowest point of the fire damage was on the cockpit side of the EPC, behind the lower right access panel where the AC ground service tie relay and the right and left heat exchanger cooling fan relays were located. The location of the fire damage is consistent with it being the point of origin for the fire.
The aft fuselage after the aircraft was tripped for parts (Source baaa-acro.com © J.R. Covington, Jr)
Visual examination and disassembly of the relays revealed numerous repairs that did not conform to manufacturers' production standards. For example, the baseplate and coil assembly time-delay circuit were attached with four slotted screws that exhibited mechanical damage and that did not have the typical coating of sealant, some of the diodes on the time-delay circuit board appeared to be different from those used by the manufacturer during production, nonstandard shims were installed between the relay housing and the stationary contact, and nonstandard, pre-drilled two-hole washers were found installed below the contact carrier assembly.
The National Transportation Safety Board (NTSB) determines the probable cause(s) of this accident to be: A phase-to-phase arc in the left heat exchanger cooling fan relay, which ignited the Page 2 of 8 DCA00MA079 surrounding wire insulation and other combustible materials within the electrical power center panel. Contributing to the left heat exchanger fan relay malfunction was the unauthorized repair that was not to the manufacturer's standards and the circuit breakers' failure to recognize an arc fault.
The aircraft in its flying days (Source baaa-acro.com © Joerg A. Dittmer)
The aircraft damage was so extensive it was written off as damaged beyond repair. It was stripped for parts. The full NTSB report (on which this blog is based) is available for the readers' reference by clicking on the .pdf file below.