8th of August 2000, Arc and Smoke, Blog #750
- V2Aviation
- 4 days ago
- 3 min read
A McDonnell Douglas DC-9-32 was in the initial climb after departing Greensboro/High Point-Piedmont Triad International Airport, North Carolina, USA, bound for Atlanta-William B. Hartsfield International Airport, Georgia, USA, on this day in 2000. On board the 30-year-old aircraft were a crew of five and 58 passengers for the short 500 km (270 nm) flight.
The crew noticed the smell of smoke in the flight deck and immediately donned their oxygen masks and smoke goggles. ATC was contacted, and an emergency was declared. An immediate return to the airport was requested and granted.
Smoke was also observed in the forward cabin. Although the dense smoke severely restricted the flight crew's visibility, a safe landing was made shortly after the emergency was declared. An emergency evacuation was initiated as soon as the aircraft came to a stop, and all occupants successfully evacuated the aircraft. Several people sustained minor injuries, including:
Three crew members
Ten passengers
The National Transportation Safety Board (NTSB) was alerted, and an investigation was launched.
Examination of the aircraft revealed severe smoke and heat damage around the electrical 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. It was noted that the aluminium stanchion brace running the length of the compartment had been destroyed, along with the AC bus feeder wires and numerous other aircraft wiring bundles. No fire damage was found in the lower aft compartment.
On the cockpit side of the EPC, the lowest point of the fire damage was behind the lower-right access panel, where the AC ground-service tie relay and the right- and left-hand heat-exchanger cooling-fan relays were located. The location of the fire damage was consistent with this area being the point of origin of the fire.
Visual examination and disassembly of the relays revealed numerous repairs that did not conform to the manufacturer's production standards.
For example, the baseplate and coil assembly time-delay circuit were attached with four slotted screws that showed mechanical damage and 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 had been installed between the relay housing and the stationary contact, and nonstandard, pre-drilled two-hole washers were found beneath the contact carrier assembly.
The National Transportation Safety Board (NTSB) determined the probable cause of the accident to be:
A phase-to-phase arc in the left heat-exchanger cooling-fan relay, which ignited the surrounding wire insulation and other combustible materials within the electrical power center panel.
Contributing to the malfunction of the left heat-exchanger fan relay was an unauthorized repair that did not meet the manufacturer's standards, as well as the failure of the circuit breakers to recognize an arc fault.
The aircraft sustained such extensive damage that it was written off as damaged beyond repair. It was subsequently stripped for parts.
The full NTSB report, on which this blog is based, is available for readers' reference by clicking on the PDF file below.
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