History of Flight
On May 11, 2012, at approximately 1630 central daylight time, a Cessna 401 airplane, registration N9DM, collided with terrain near Chanute, Kansas. A post-crash fire ensued. The commercial pilot and three passengers were fatally injured; one passenger was seriously injured. The airplane was substantially damaged. The airplane was registered to DRDJ Sales and operated by the pilot under 14 CFR Part 91 as a personal flight. Visual meteorological conditions prevailed, and the flight operated on an instrument flight rules plan. The cross-country flight departed Richard Lloyd Jones Jr. Airport (RVS), Tulsa, Oklahoma, at approximately 1545, with a destination of Council Bluffs Municipal Airport (CBF), Council Bluffs, Iowa.
The survivor of the accident provided a written statement. She reported that when the pilot turned on the heater, a terrible smell was detected. The pilot told the passengers that the smell was normal for some heaters. When the pilot turned the heater off, dark black smoke began to enter the airplane, making it difficult to see. In an attempt to extinguish the fire, they poured water bottles into the vents, which had no effect. The pilot quickly descended. During the emergency landing, the pilot attempted to pull up, but the wing tip hit the ground first. The passenger thought the airplane rolled as it hit the ground. Another passenger assisted her in egressing from the airplane, but that survivor later succumbed to his injuries.
Pilot Information
The pilot, age 23, held a commercial pilot certificate with airplane single-engine land, multi-engine land, and instrument airplane ratings. On June 28, 2011, a first-class medical certificate was issued with the restriction "not valid for night flying or by color signal control." At the time of the medical certificate application, he reported accumulating 600 total hours, with 50 logged in the preceding six months. On June 27, 2010, he had applied for his commercial pilot certificate and reported 392.8 hours of total time. The pilot's logbook was not located during the investigation.
Aircraft Information
The multi-engine airplane, N9DM, serial number 401-0123, was manufactured in 1967. It was powered by two turbocharged, fuel-injected, 300-horsepower TSIO-520-E engines, each driving a metal three-blade propeller. According to the airplane's logbooks, the last annual inspection was accomplished on January 15, 2012, at a Hobbs time of 2,455.5 hours. This inspection included the remark "heater is inop[erative]." A sales advertisement dated January 8, 2012, listed the airframe's total time as 4,819 hours. Including time the pilot flew for insurance requirements, the airframe had accumulated at least 4,831 hours.
Meteorological Information
At 1652, an automated weather reporting facility at Chanute-Martin Johnson Airport (KCNU), 6 nautical miles east of the accident site, reported wind from 180 degrees at 4 knots, visibility 10 miles, a broken ceiling at 11,000 feet, temperature 21 degrees Celsius, dew point 15 degrees Celsius, and barometric pressure 30.07 inches of mercury.
Communications
The pilot was under radar and radio contact with Kansas City Air Route Traffic Control Center (ARTCC). At 1606, he reported the airplane was level at 10,000 feet. The pilot requested and was approved to proceed direct to CBF. At 1624, he requested a descent from 10,000 to 8,000 feet to "get out of the clouds and turbulence," which was approved. ARTCC then issued a frequency change, which was acknowledged by the pilot. The pilot did not make radio contact with the next controller, and no further communications occurred. No distress calls were heard by ARTCC controllers or other pilots.
Wreckage and Impact Information
The accident site was in a line of trees between a grass field and a corn field. The debris path was aligned along a 277-degree magnetic heading. The first impact point was a narrow ground scar consistent with a wing tip strike, near which was a portion of the right wing tip. About 88 feet down the wreckage path, two ground scars of varying lengths were found. No other ground scars led to the main wreckage. The main wreckage came to rest in a tree line about 162 feet from the initial impact scar, in an upright position facing east. A post-crash fire had consumed a majority of the fuselage. All flight control surfaces were accounted for.
The left wing remained attached to the fuselage but was torn and fragmented just outboard of the engine nacelle. The left engine separated from the nacelle and was located behind the left wing. The right wing remained attached, crushed rearward and folded along its length, with the outboard portion bent upward and twisted rearward. The right engine separated from its nacelle and was located 105 feet west of the main wreckage. The vertical stabilizer was torn and twisted; the rudder was separated but remained attached via control cables. The vertical stabilizer and elevator had separated and were beneath the tail portion. Flight control continuity was established to all controls. The flaps were set to 15 degrees, and the landing gear was retracted. Portions of acrylic glass from the forward wind screens were found east of the wreckage, with soot on the cabin side surface. Cockpit gauges were impact and thermally damaged. Both fuel selector valves were found in the OFF position.
The left propeller had separated from the hub and was found near the right wing; all three blades were relatively straight, with one bent rearward near mid-span, and all had soil and debris on tips. The right propeller remained attached to the hub; all three blades displayed leading-edge polishing and tip damage, with specific bends described for each blade.
Medical and Pathological Information
An autopsy performed on the pilot, authorized by the Wilson County Coroner's Office, determined the cause of death as thermal injuries. No indication of physical or toxicological impairment was found. Forensic toxicology detected 12% carbon monoxide in the pilot's blood; no cyanide, ethanol, or other tested substances were detected.
Tests and Research
Both engines were shipped to Continental Motors Inc. for examination and engine runs. Each engine started and produced rated horsepower, with no preimpact anomalies detected.
The airplane was equipped with a South Wind 8259GL-1 combustion heater, serial number 388, last overhauled on February 11, 1994. Logbooks recorded its installation on October 17, 1996, with a heater Hobbs time of 126.4 hours and Airworthiness Directive (AD) 81-09-09 accomplished. No additional entries for heater Hobbs time or AD compliance were found. On January 6, 2011, an annual inspection mistakenly identified the heater as a Janitrol and listed it as inoperative. A work order dated February 9, 2011, described troubleshooting that found no electrical power to the fuel safety valve due to a stuck airflow switch, which was cleaned and the heater then operated normally. No logbook entry returned the heater to service, and no evidence of a pressure decay test was found. The heater Hobbs was destroyed in the accident.
For insurance purposes, the pilot was required to fly with a certificated flight instructor (CFI) for at least 12 hours. The CFI recalled that during a flight on April 25, 2012, the heater's overheat light illuminated shortly after activation; the heater shut down, and no smoke or fumes were detected. They continued, and at the destination, the CFI demonstrated how to reset the circuit breaker. The return flight was made without the heater. The CFI did not know further about the heater. The pilot's father (a retired airline pilot) had flown with the pilot on May 6, 2012, and did not recall any placard on the heater or mention of problems. Fire damage prevented evaluation of placards.
Cessna's Model 401 Owner's Manual states that when the overheat warning light illuminates, the heater overheat switch has actuated and the air temperature in the heater has exceeded 325°F. The heater turns off and cannot be restarted until the overheat switch (located in the right forward nose compartment) is reset. Prior to reset, the heater should be thoroughly checked.
No record of work on the accident airplane after the overheat light illumination was found. Neither repair shop at the airplane's home airfield performed work, and the fixed base operator did not recall any work in the days before the accident.
Cessna's service manual lists causes of "heater trips over heat switch" as a defective overheat switch or insufficient vent air/defective duct limit switch, with corrective actions to replace the switch or increase air rate.
Heater Examination
The heater was examined at Cessna Aircraft Company. It displayed thermal damage signatures. When the igniter housing assembly was removed, thermal damage was noted to the ignition unit and spark plug, the latter showing heavy sooting. The heater's shroud was removed, and the duct limit switch was found to be misaligned; discoloration on the switch surface suggested misalignment prior to heat discoloration. The combustion chamber interior was heavily sooted and contained several large pieces of carbon deposits and debris. The heater was reassembled and sealed using a general sealant. A pressure decay test was unsuccessful; using a soap-and-water mixture and pressurization, at least four leaks were found in the combustion chamber: three on welded joints and one around the igniter tip.
Compliance with Airworthiness Directive 81-09-09
After compliance with AD 81-09-09, the heater is required to be inspected every 250 hours of use and overhauled every 1,000 hours, with no calendar time limits. If the inspection is not completed or the heater is inoperative, the AD provides no guidance to disable the heater. In contrast, a similar heater's AD requires visual inspection every 100 hours or 1 year and includes steps to disable the heater if it fails inspection or as an alternative compliance.