IAD02LA020

While in cruise flight, with the combustion heater turned on, the pilot heard an explosion. Smoke then entered the cabin, followed by a loss of electrical power. The pilot diverted and landed without incident. Examination of the airplane revealed that the combustion heater exhibited heat and fire damage. The fuel pump supply line that ran between the fuel pump and the heater was found cracked at the fuel pump housing inlet, and was loose. The fractured surfaces appeared dull, and displayed carbon build-up. Examination of the airplane's logbooks revealed that on December 1, 1993, the combustion heater had been removed, rebuilt, and then re-installed, at a total airplane time of 3,932.2 hours. Additionally, there were no logged entries which indicated that the 20-year old Airworthiness Directive that was issued to "prevent a hazardous condition caused by deterioration on the combustion heater", for this particular model heater had been complied with. The airplane underwent an annual inspection in September 2001, at a total airplane time of 5,213.5 hours. At the time of the accident, the airplane had accrued a total of 5,231.9 hours.

On December 17, 2001, at 1850 eastern standard time, a Cessna 401A, N4062Q, was substantially damaged from an in-flight fire during cruise flight, near Martinsburg, West Virginia. The certificated airline transport pilot and passenger were not injured. Night visual meteorological conditions prevailed for the flight that originated at Chester County G. O. Carlson Airport (40N), Coatesville, Pennsylvania, destined for the Tri-State/Milton J. Ferguson Airport (HTS), Huntington, West Virginia. An instrument flight rules flight plan was filed for the personal flight conducted under 14 CFR Part 91.

According to a Federal Aviation Administration (FAA) inspector, the airplane was at 6,000 feet with the combustion heater on, when the pilot heard a loud explosion. Smoke then entered the cabin, followed by a complete electrical failure.

The pilot did not declare an emergency and landed without incident at the Eastern West Virginia Regional/Shepard Airport, Martinsburg, West Virginia.

Two FAA inspectors performed an examination of the airplane. According to an inspector, soot was observed along the left and right side of the forward fuselage. Examination of the interior section of the nose compartment revealed that skin panels, electrical wiring, and the Stewart-Warner model 8259 combustion heater exhibited heat and fire damage. Additionally, the bulkhead and floorboards were buckled.

The inspector also reported that the fuel pump supply line that ran between the fuel pump and the combustion heater was cracked where it entered the fuel pump housing. The line was also loose, but did not exhibit heat or fire damage. The fractured surfaces appeared dull, and displayed some carbon build-up.

The combustion heater's Hobbs meter was destroyed by fire, and the heater's total time could not be verified.

The airplane underwent an annual inspection in September 2001, at a total airplane time of 5,213.5 hours. At the time of the accident, the airplane had a total time of 5,231.9 hours.

Airworthiness Directive (AD) 81-09-09, amended May 8, 1981, was issued to "prevent a hazardous condition caused by deterioration on the combustion heater", on Stewart-Warner 8240, 8253, 8259, and 8472 model series heaters.

The AD stated that for "combustion heaters having 250 hours or more time in service after the effective date of this AD, conduct a 250 hour inspection in accordance with the manufacturer's service manual within the next 50 hours of combustion heater operation, unless already accomplished within the last 200 hours of heater time, and thereafter at intervals not to exceed 250 hours of combustion heater operation."

Along with the above inspection, a general inspection of the combustion heater installation must also be accomplished and include the following:

"Check all fuel lines for security at joints and shrouds, correcting those showing evidence of looseness or leakage."

The AD also stated:

"...combustion heaters having 1,000 hours or more time in service after the effective date of this AD, overhaul the combustion heater in accordance with the manufacturer's service manual within the next 50 hours of combustion heater operation, unless already accomplished within the last 950 hours of heater time, and thereafter at intervals not to exceed 1,000 hours of combustion heater operation."

Additionally, the AD stated that if the owner/operator could not document combustion heater operative time, the airplane time must be used.

An FAA inspector examined the maintenance logbooks and associated records provided by the owner. According to the inspector, on December 1, 1993, the Stewart-Warner combustion heater, model series 8259, was removed, rebuilt, and then re-installed, at a total airplane time of 3,932.2 hours. The examination also revealed that there were no logged entries which specifically indicated that AD 81-09-09 had been complied with.

In a telephone conversation, the owner stated that he purchased the airplane in July, 1998. He was not familiar with the maintenance procedures involving the Stewart-Warner combustion heater or AD 81-09-09. The owner said that he did not know how much time had accumulated on the heater.

The pilot reported a total of 20,000 flight hours; 15,000 hours in multi-engine airplanes, of which 150 hours were in make and model.

Weather at Eastern West Virginia Regional/Shepard Airport, Martinsburg, West Virginia, at 1853, was wind from 290 degrees at 8 knots, visibility 10 statute miles, ceiling overcast 4,300 feet, temperature 44 degrees F, dewpoint 33 degrees F, and altimeter setting 29.81 inches Hg.