N23806

HISTORY OF FLIGHT

On July 3, 1996, about 0250 eastern daylight time a Beech 58, N23806, registered to a private individual, operated by the ISO Aero Service, Inc., crashed into a corn field northeast of the Kinston Regional Jetport at Stallings Field, Kinston, North Carolina. Weather conditions at the accident site area are unknown and an IFR flight plan was filed for the 14 CFR Part 91 positioning flight. The airplane was substantially damaged and the commercial-rated pilot, the sole occupant sustained minor injuries. The flight originated at 0217 from the Raleigh-Durham International Airport, Raleigh, North Carolina.

Before departure the pilot twice phoned the Raleigh Durham Automated Flight Service Station (AFSS), the first call was for a flight to Kinston with a 0200 departure and to file an IFR flight plan. The second call made 14 minutes later, was to obtain an outlook weather briefing for the same flight with a 0600 departure. The pilot stated that before the flight departed she was experiencing fatigue and thought about remaining in Raleigh, but elected to continue. She further stated that after starting the engines, she started the heater which remained on for the takeoff for the 67 nautical mile flight.

About 10 minutes after takeoff while in contact with the Seymour Johnson Approach Control, the pilot was advised that the Seymour Johnson Air Force Base (SJAFB) weather was IFR with a broken ceiling at 300 feet and to expect the localizer approach to runway 23. After being advised of the ceiling and visibility at the SJAFB she requested clearance for the VOR approach to runway 23. She further stated that when the flight was about 1/2 way to the destination she felt like returning to Raleigh due to fatigue but elected to continue. The flight was vectored to fly heading 100 degrees but on the reply, the pilot interjected "left" then the heading. The controller then advised the pilot to turn right to a heading of 100 degrees and the pilot then correctly read back the heading and direction of the turn. The pilot again read back an incorrect direction of a turn twice while being vectored for the VOR approach to runway 23. The controller cleared the flight for the VOR approach and advised the pilot to contact the Raleigh AFSS after landing. There was no further radio contact with the controller after the pilot acknowledged the instruction. The pilot reportedly turned off the heater about 5 minutes before beginning the VOR approach.

The pilot stated that she fell asleep shortly after extending the landing gear and was awakened after descending through trees and just before impact with the ground. The airplane then spun around and came to rest upright. A fire which was started after the airplane came to rest burned the pilot on her arms and face. The pilot walked from the wreckage to a house and later advised emergency management personnel that she fell asleep during the approach.

PERSONNEL INFORMATION

The pilot stated that she was not scheduled to fly scheduled flights on July 2nd and she had a maximum of 6 hours sleep when she awoke at 0630 that morning. She arrived at the Kinston Airport at 0800 and flew another company airplane to another airport for maintenance arriving there about 0840 on July 2nd. She remained at the facility, did not sleep, and about 1700 she received a phone call from her company. She was asked if she would fly a different company airplane to Peoria, Illinois, to pick up cargo and deliver it to the Raleigh-Durham International Airport, Raleigh, North Carolina. She stated yes and the accident airplane was flown to her location by another company pilot. The flight to Peoria was uneventful and arrived about 2200. The flight remained on the ground about 30 minutes and the flight departed for Raleigh landing uneventfully where the cargo was offloaded. She did not operate the heater on either flights to Peoria, Illinois, or from there to Raleigh, North Carolina. She also stated that she hand flew the airplane on all flights and encountered thunderstorms on both flights to and from Illinois.

On July 1st, the pilot worked in the office from 0800 to 1700 hours at the operator's facility, but flight/duty records provided by the operator indicated that she was off duty. On June 30th she worked a duty day of 6 hours from 1030 to 1630 but she was not sure what time she woke up that day or what time she went to bed the night before. On June 29th, she worked a duty day of 6 hours from 0930 to 1530 and was again not sure what time she woke or what time she went to bed the night before. On June 28th, she worked a duty day of 1 hour starting at 0630 and she reported awaking no later than 0600 and was not sure of the time she went to bed the night before.

AIRCRAFT INFORMATION

Review of the aircraft logbook revealed that the heater was last inspected as required by airworthiness directive (AD 82-07-03) on July 13, 1995, at a heater Hobbs time of 663 hours. The AD for the installed heater requires in part periodic inspections at intervals not to exceed 100 heater-hours time-in-service or 24 months, whichever occurs first. The heater Hobbs indicated post accident 753.9.

METEOROLOGICAL INFORMATION

Weather information at the Kinston Airport at the time of the accident was not available. A weather observation taken at 0255 from the Seymour Johnson Air Force Base which was located about 18 nautical miles and 275 degrees from the crash site indicated that a broken ceiling existed at 300 feet and the visibility was 4 miles. Review of the instrument approach procedure indicates that the minimum descent altitude is 352 feet above ground level or 440 feet mean sea level.

COMMUNICATIONS

The pilot was in contact with the Seymour Johnson AFB Radar Approach Control (RAPCON) facility and a transcript is an attachment to this report.

WRECKAGE AND IMPACT INFORMATION

Examination of the accident site was performed by an FAA inspector who reported that the left engine was separated and the left wing was separated just outboard of the engine nacelle. Fire damage to the right wing was noted. The airplane was found upright in a corn field and the landing gear had been determined to be extended and the flaps retracted at the impact. The cabin air vent was in the "on" position and the heater was in the "off" position. The FAA inspector stated that the airplane crashed in line with the extended centerline of the runway and the crash site was located about 1.5 nautical miles from the runway threshold. The exhaust pipe of the heater was determined to be properly installed with no blockage noted and the heater and associated components were removed for further testing. See the Tests and Research Section of this report.

MEDICAL AND PATHOLOGICAL

On the morning after the accident, the FAA inspector who performed the on-scene examination of the wreckage called the laboratory at the hospital where the pilot was initially taken and verbally requested that a test be performed to determine the presence in the blood of carbon monoxide. The FAA inspector visited the hospital that evening and again requested that carbon monoxide testing be performed. The hospital laboratory did not test for carbon monoxide and the sample was not retained for testing. The pilot did not report any strange odors nor did she report experiencing a headache during or after operating the heater during the accident flight segment. She did report experiencing nausea, feeling sick to her stomach, blurred vision, and confusion when the controller advised her that the flight was observed on radar to be left of course when the CDI was beginning to center.

TESTS AND RESEARCH

Testing of the combustion tube assembly was initially performed twice at the operator's facility under the control of the FAA inspector who performed the on-scene examination. The first and second tests revealed that the pressure in the combustion chamber dropped below 1.0 psig at 45.83 and 45.01 seconds respectively. The heater maintenance and overhaul manual indicates that after 45 seconds the pressure in the combustion chamber must exceed 1.0 psig. If the pressure drops below 1.0 psig before 45 seconds, that indicates a leak is present either in the combustion chamber or around the seals. Leakage was noted around the gasket and attach screw of the valve assembly. The heater assembly was then sent to the manufacturer's facility for further examination.

Examination of the heater assembly revealed that the outer shroud exhibited impact damage and the fuel inlet tube was bent. Additionally, the combustion tube outer jacket assembly and combustion tube exhibited impact damage. Pressure decay tests of the combustion tube assembly revealed that the pressure decreased consistently from the test 6.0 psig to 0 psig in about 10 seconds with an average of 8 seconds. The combustion tube was pressurized and a soap and water solution was brushed over the combustion tube. Again a leak which was previously noted occurred at the fuel feed retaining screws and at the sealant material between the fuel feed and the nozzle holder. Also, a leak was noted at two of the three crossover tubes which provide an escape path for the exhaust from the combustion chamber. There was no visible evidence of burn through, cracks, or holes in the combustion chamber, or the liner which covers the combustion chamber or of the outer shroud. Further testing of the combustion air blower/motor, ventilation blower/motor, ignition system, fuel solenoid valve and spray nozzle, combustion air pressure differential switch, or the overheat switch revealed no evidence of preimpact failure or malfunction. A discrepancy to the overheat switch was noted but the switch was operational. Further examination of the crossover tubes with a 10 power magnifying glass revealed no evidence of cracks or holes. Zyglow te...