Moline, IL, USA
N118SF
Hawker Beechcraft Corp. 99
The pilot said that during descent he "smelled electrical smoke and saw flames behind the power quadrant." He declared an emergency and removed the fire extinguisher from its holder. In the time it took to do this, the flames were no longer visible and the burning smell was not getting any stronger. The pilot landed at his destination without further incident. An examination revealed that a 10 ohm, 1/2 watt, resistor contacted the ground lug of a silicon controlled rectifier in the flap control circuit. The manufacturer indicated that manufacturing practices require component leads to be covered with a sleeve. The 100 hour inspection listed in the airplane's maintenance manual indicated that the instrument plumbing and wiring should be inspected for "condition, attachment, chafing, etc."
On February 18, 2008, about 2030 central standard time, a Hawker Beechcraft Corp. 99, N118SF, operated by Suburban Air Freight Inc., as a cargo airplane, received minor damage during cruise when an in-flight fire occurred about 30 miles west of the Quad City International Airport (MLI), near Moline, Illinois. Visual meteorological conditions prevailed at the time of the accident. The unscheduled domestic 14 CFR Part 135 cargo flight had a filed and activated an instrument flight rules flight plan. The pilot was uninjured. The flight originated about 1930 from the Eppley Airfield, near Omaha, Nebraska, and was destined for MLI. The pilot said that during the descent to MLI he "smelled electrical smoke and saw flames behind the power quadrant." He declared an emergency and removed the fire extinguisher from its holder. In the time it took to do this, the flames were no longer visible and the burning smell was not getting any stronger. The pilot elected to continue to MLI. A Federal Aviation Administration Inspector examined the airplane. The inspector found that a 10 ohm, 1/2 watt, resistor contacted the ground lug of a silicon controlled rectifier. The components were mounted to a terminal strip located on the aft side of the center pedestal. The components were part of the flap control circuit. The circuit was protected by a five-amp circuit breaker manufactured in 1967. The circuit breaker was checked multiple times to verify what amperage it tripped and the initial test required 17 amps to trip the breaker. The airplane's last inspection was completed on December 28, 2007. The airplane accumulated 14,079 hours of total time at the time of that inspection. The manufacturer indicated that manufacturing practice requires electrical wires and leads of resistors and capacitors to be covered with sleeve insulation. The manufacturer indicated that periodic visual inspections of this wire harness per the Model 99 Maintenance Manual should detect sleeve damage that would allow the 10 ohm, 1/2 watt, resistor to contact the ground lug of a silicon controlled rectifier. The 100 hour inspection listed in the Model 99 Airliner Series Maintenance Manual, Chapter 5-20-00, indicated that the instrument plumbing and wiring should be inspected for "condition, attachment, chafing, etc."
The arcing of the resistor and silicone controlled rectifier in the flap control circuit.
Source: NTSB Aviation Accident Database
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