Ekalaka, MT, USA
N85WT
Cessna 310N
The instrument-rated private pilot was on a cross-country flight in instrument meteorological conditions. About 40 minutes after departure the pilot reported to air traffic control (ATC) that he was encountering icing conditions at his cruise altitude of 13,000 feet and requested a lower altitude. The pilot was cleared to descend to 11,000 feet. The pilot continued to encounter icing conditions and was cleared to descend to lower altitudes. About 15 minutes after the pilot's initial report of icing conditions, he transmitted "headed towards the runway" followed by "...going down...troubles with engine." No additional communication from the accident pilot was received. The wreckage was located later that day in an open field about 2 miles west of a private airstrip. Post accident examination of the airframe and engine revealed no evidence of mechanical malfunction or anomaly. Ground scars and wreckage signatures were consistent with a stall/mush into the terrain. Weather forecasts and pilot reports for the pilot's intended route of flight indicated icing and widespread instrument meteorological conditions. The pilot received a weather briefing prior to the flight; however, it was limited by his request to wind, temperature aloft forecasts and METAR observations for his route of flight. FAA Advisory Circular 91-51A states, in part, "The most hazardous aspect of structural icing is its aerodynamic effects. Ice can alter the shape of an airfoil. This can cause control problems, change the angle of attack at which the aircraft stalls, and cause the aircraft to stall at a significantly higher airspeed..." The AC additionally states "Flight into known or potential icing situations without thorough knowledge of icing and its effects and appropriate training and experience in use of deice and anti-ice systems should be avoided." According to the manufacturer, the airplane was not certified or equipped for flight into known icing conditions. It is probable that the airplane was unable to maintain an adequate airspeed during the descent for landing and stalled short of the runway.
HISTORY OF FLIGHT On October 7, 2007, about 1148 mountain daylight time, a Cessna 310N, N85WT, collided with terrain approximately 15 miles south of Ekalaka, Montana. The private pilot, who was the owner and operator of the airplane, and the one passenger aboard were killed. The airplane sustained substantial damage. The airplane was operated as an instrument flight rules (IFR) cross-country flight under the provisions of Title 14, Code of Federal Regulations (CFR) Part 91. The flight departed Bozeman, Montana, (BZN) at 1002 with an intended destination of Dells Airport (DLL), Baraboo, Wisconsin. Instrument meteorological conditions prevailed for portions of the flight; however, visual meteorological conditions prevailed at the accident site. An instrument flight plan was in effect for the flight. Air traffic control (ATC) information obtained from the Federal Aviation Administration (FAA) indicated that the airplane was at a cruise altitude of 13,000 feet mean sea level (msl). At 1130, the pilot reported to ATC that he was encountering "light icing." At 1134 the pilot requested a lower altitude, stating "...I think we might take lower when possible." ATC cleared the flight to descend from 13,000 feet to 12,000 feet msl. At 1137, the pilot again requested a lower altitude and was cleared to 11,000 feet. At 1145 the pilot reported that he was encountering icing conditions stating "... I think I'm going to be going down but trying to stay on course." At 1146, ATC received a radio transmission believed to be from the pilot stating "problems" followed by "..five whiskey tango we seem to have recovered." At 1147, the pilot stated "five whiskey tango...melting." This was the last direct communication between the accident airplane and ATC, however, additional radio transmissions from the accident airplane/pilot were received by the flight crew of a nearby airplane, Northwest Airlines Flight 437, and relayed to ATC. At 1147 the Northwest Airlines flight crew relayed to ATC that the pilot of the accident airplane stated he was "headed towards the runway" followed by "...going down troubles with engine." No additional communication from the accident pilot was received or recorded. About 1151 the Carter County Sheriff's Office received reports of a downed airplane in the area of the Laird Ranch Airport, Ekalaka. The wreckage was located 15 minutes later about 2 miles west of the airport. PERSONNEL INFORMATION The pilot, age 55, held a private pilot certificate with airplane single-engine land, multi-engine land and instrument airplane ratings. The pilot's most recent second-class medical certificate was issued on April 25, 2007, and contained a limitation that the holder must wear corrective lenses. On the pilot's latest FAA Application for Airman Medical Certificate (Form 8500-8), dated April 25, 2007, the pilot listed 600 hours total flight time and 50 hours total flight time in the 6 months preceding the medical. FAA records indicated that on December 12, 2006, after two previous failed attempts, the pilot successfully passed his instrument check ride and was issued an instrument rating. The records indicated that the pilot's total flight experience prior to the check ride was 502 hours. On February 20, 2007, the pilot successfully passed a multi engine check ride and was issued an airplane multi engine land rating with instrument privileges. AIRCRAFT INFORMATION The twin engine Cessna 310N, serial number 310N-0106, was manufactured in 1968, and was certified in the normal category. The airplane was equipped with two Continental IO-470 engines rated at 260 horsepower each. The airplane was not equipped with wing deice or anti-ice systems. The airplane's fuel system consisted of four fuel tanks; two 50-gallon main tip tanks and two 20-gallon inboard auxiliary tanks. All four tanks were "topped" before the pilot departed from Bozeman. Review of copies of maintenance logbook records showed an annual inspection of the airframe, engine and propeller was completed on July 27, 2007, at a recorded tachometer reading of 4,472.7 hours. FAA Records indicated that the pilot purchased the airplane in January of 2007. METEOROLOGICAL INFORMATION The closest weather observation facility to the accident site was Baker Municipal Airport (KBHK), Baker, Montana, located approximately 43 nautical miles (nm) north-east of the accident site at an elevation of 2,975 feet msl. The airport is equipped with an Automated Surface Observing System (ASOS). The following observation report was issued surrounding the period of the accident: At 1153, the weather observation was, in part, wind from 240 degrees at 7 knots, visibility 10 statute miles, ceiling overcast at 9,500 feet, temperature 7 degrees C, dew point 3 degrees C, altimeter 30.07 inches of Hg. Airman's Meteorological Information (AIRMET) for icing (ZULU) was issued for areas of Montana at 0845. It warned of moderate icing conditions along the pilot's route of flight and flight level and was valid during the timeframe of the accident. Salt Lake Center (ZSLC) received two pilot weather reports (PIREP) for icing conditions in the vicinity of the accident. At 1130 a pilot reported light rime ice 40 miles southeast of Miles City at 13,000 feet; at 1211 a pilot reported moderate rime ice 120 miles east of Miles City at 10,000 feet. According to Computer Science Corporation (CSC) Direct User Access Terminal System (DUATS) records, the pilot obtained weather information for his intended route of flight and filed an IFR flight plan from BZN to DLL and a second flight plan from DLL to Martin State Airport (MTN) Baltimore, Maryland. The weather information obtained by the pilot was limited to wind and temperature aloft forecasts and METAR observations for his route of flight. DUATS user records obtained from Computer Science Corporation revealed that the pilot filed two flight plans and obtained weather information for the same route of flight on October 6. An employee at a Fixed Base Operator (FBO) in Bozeman, where the accident airplane was parked, stated the pilot of the accident airplane arrived at the airport on October 6. He reported that the pilot intended to depart Bozeman that day; however, cancelled the flight due to concerns about weather conditions. WRECKAGE AND IMPACT INFORMATION All of the airplane's major components were found at the main wreckage site. The wreckage debris field encompassed an area approximately 200 feet in length along a magnetic heading of 235-degrees. The measured elevation at the main wreckage was about 3,736 feet mean sea level (msl). The first identified point of contact with terrain was a series of ground scars located at the northeast end of the debris field. The ground scars were parallel to the debris path and matched the geometry of the engine nacelles and propellers. The main wreckage came to rest on a heading of 335 degrees and was located in the confines of a large burn area at the southwest end of the debris path. The airplane impacted terrain and came to rest upright on its fuselage and wings. Fire and impact forces destroyed the cabin, cockpit and instrument panel. The wings and empennage remained attached to the fuselage, and the engines remained attached to the wings. The left and right main fuel tanks (tip tanks) were ruptured and extensive impact and fire related damage was noted. The landing gear was in the retracted position. All flight control aerodynamic surfaces remained attached to their respective airframe components. Flight control cable continuity was established throughout the airframe and no anomalies were noted. The flaps were extended. According to the Cessna representative, drive sprocket and chain measurements indicated the flaps were in a 15-degree (down) position. The outboard section of the left wing, approximately 4-feet, was separated and folded back on top of the inboard section of the wing. The inboard section of the wing remained attached to the fuselage. The inboard auxiliary fuel tank (left) was intact and no fuel was noted. Impact and fire related damage was noted to the wing and breached wing tip fuel tank. The right wing was in place and remained attached to the fuselage. Impact and fire related damage was noted to the wing and breached wing tip fuel tank. The inboard auxiliary fuel tank (right) was intact and trace amounts of fuel were noted. Both left and right fuel selector handles, and associated fuel valves were found in the "Auxiliary Tank" position. Both engines remained attached to their respective firewalls and associated engine mounts. The left propeller remained attached to the crankshaft and the spinner was intact. All three propeller blades were in place and remained attached to the hub assembly at a low pitch angle. The propeller blades displayed chordwise scratches and minor leading edge damage. The number one blade (found at the 12 o'clock position) was unremarkable with the exception of minor chordwise scratches on the blade tip. The number two blade was bent aft and twisted at mid span. Leading edge damage was displayed. The number three blade was bent aft at the blade root. It displayed spanwise scratches and chordwise polishing. The right propeller remained attached to the crankshaft and the spinner was intact. All three propeller blades were in place and remained attached to the hub assembly at a low pitch angle. The number one blade (found at the 12 o'clock position) was bent aft and minor chord wise scratches were noted. The number two blade was bent aft and twisted. Chordwise scratches and leading edge damage was noted. The number three blade was bent aft. Spanwise scratches and chordwise polishing was noted. Onsite examination of the airframe and flight control system components revealed no evidence of preimpact mechanical malfunction. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy was performed on the pilot on October 5, 2007. According to the autopsy report, the pilot's cause of death was attributed to "Blunt traumatic chest injuries." The FAA's Civil Aeromedical Institute (CAMI) conducted a toxicological examination on October 31, 2007. The results were negative for alcohol or drugs. TESTS AND RESEARCH On November 14-15, 2007, both engines were examined at a hangar facility in Belgrade, Montana, under the direction of an NTSB investigator. The examination revealed no evidence of preimpact mechanical malfunction. ADDITIONAL DATA FAA Advisory Circular 91-51A states, in part, "The most hazardous aspect of structural icing is its aerodynamic effects. Ice can alter the shape of an airfoil. This can cause control problems, change the angle of attack at which the aircraft stalls, and cause the aircraft to stall at a significantly higher airspeed. Ice can reduce the amount of lift that an airfoil will produce and increase drag several fold. Additionally, ice can partially block or limit control surfaces which will limit or make control movements ineffective. Also, if the extra weight caused by ice accumulation is too great, the aircraft may not be able to become airborne and, if in flight, the aircraft may not be able to maintain altitude." Additionally, the Advisory Circular states "Flight into known or potential icing situations without thorough knowledge of icing and its effects and appropriate training and experience in use of deice and anti-ice systems should be avoided." According to the manufacturer, the airplane was not certified or equipped for flight into known icing conditions.
The pilot's improper in-flight planning/decision, his continued flight into adverse weather (icing conditions), and failure to maintain an adequate airspeed during the emergency descent for landing. Contributing to the accident were the forecast icing conditions.
Source: NTSB Aviation Accident Database
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