Twin Falls, ID, USA
N2088G
DOUGLAS AD-4N
The non-instrument-rated pilot was on a cross-country flight when the airplane impacted terrain. According to limited radar data, after departure the flight proceeded northwest and climbed to 6,500 feet mean sea level (msl). Only segments of the flight were visible due to the low altitude range of the radar. The flight track continued northeast to its last target at an altitude of 7,900 feet msl and about 0.25 mile from the accident site. Terrain elevation at the accident site was about 6,600 feet msl. A postaccident examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. Ground scar analysis, impact signatures, and wreckage fragmentation patterns indicated that the airplane impacted terrain in a steep, nose-down attitude with high forward velocity. Analysis of available weather information indicated that conditions likely produced restricted visibility in the area at the time of the accident. The restricted visibility conditions would have been conducive to the development of spatial disorientation.
HISTORY OF FLIGHT On March 8, 2011, about 1628 mountain standard time, a Douglas AD-4N, N2088G, owned and operated by the pilot, impacted terrain in the Sawtooth National Forest. The accident site was located about 30 miles south-southeast of Joslin Field-Magic Valley Regional Airport (TWF), Twin Falls, Idaho. The airplane was substantially damaged by impact forces and a postimpact fire. The private pilot and passenger were fatally injured. About the time of the accident, visual meteorological conditions prevailed at TWF. The personal flight was performed under the provisions of 14 Code of Federal Regulations Part 91, and no flight plan was filed. The flight originated from the Wendover Airport (ENV), Wendover, Utah, about 1550. There were no witnesses to the accident. When the airplane failed to arrive at its destination, concerned family and friends reported it overdue. Local authorities, including the Civil Air Patrol (CAP), initiated search and rescue operations. The airplane was subsequently located about 6,500 feet mean sea level (msl). The approximate global positioning system (GPS) coordinates of the primary wreckage were 42 degrees 00.72 minutes north latitude and 114 degrees 18.67 minutes west longitude. A radar track was recorded the day of the accident and shows about a 30-minute flight beginning near ENV and ending about .25 mile from the accident site. PERSONNEL INFORMATION A review of Federal Aviation Administration (FAA) airman records revealed that the 55-year-old pilot held a private pilot certificate for single-engine land airplane. The pilot held a third-class airman medical certificate issued June 5, 2010, with the limitation that he must have available glasses for near vision. No personal flight records were located for the pilot. The National Transportation Safety Board (NTSB) investigator-in-charge (IIC) obtained the aeronautical experience listed in this report from a review of the FAA airmen medical records on file in the Airman and Medical Records Center located in Oklahoma City, Oklahoma. The pilot reported on his medical application dated June 5, 2012, a total time of 1,826 hours with 10 hours logged in the last 6 months. RADAR INFORMATION The IIC reviewed recorded radar data from the CAP. A radar track shows about a 30-minute flight beginning near ENV and ending about .25 mile from the accident site. The secondary 1200 Visual Flight Rules (VFR) beacon code at a mode C radar data track is incomplete and only shows segments of the flight. The first target reported an altitude of 6,100 feet msl west of the ENV. About 7 minutes later the radar track continues to the northwest direction and climbs to an altitude of 6,500 feet msl. The second half of the radar track has a northeasterly course. The last target was at an altitude of 7,900 feet msl and about .25 of a mile from the accident site. Terrain elevation at the accident site is about 6,600 feet msl. AIRCRAFT INFORMATION The airplane was a Douglas AD-4N, A-1 Skyraider, serial number 126935. A review of the last FAA Application for Airworthiness Certificate revealed that the airplane had a total airframe time of 2,440 hours. The airplane’s logbooks were not obtained during the investigation. According to the FAA, the airplane held an airworthiness certificate in the experimental, exhibition racing category. The engine was a Wright R-3350-26WD, serial number C590665, a twin row, supercharged, air-cooled, radial engine with 18 cylinders and produced about 2,500 horsepower. The last inspection of the engine was performed on March, 1, 2011, with about 311 hours since its most recent major overhaul. METEOROLOGICAL INFORMATION In an NTSB Weather Study, a United States Bureau of Land Management Remote Automated Weather System (RAWS), station BULI1, had recorded weather information during the time of the accident. The location of the station was about 9 statute miles to the west-northwest of the accident site at an elevation of the about 5,700 feet msl. The station indicated relative humidity had been increasing hours prior and up to the time of the accident. Temperatures around the time of the accident were near freezing and the dew point was about minus 1.7 degrees Celsius. Wind direction was about 192 degrees and wind speed was at 5.2 knots gusting to 9.5 knots. The closest aviation weather observation station was located at TFW, which was about 30-statute miles north-northwest of the accident site. The elevation of the weather observation station is 4,154 feet (msl). An aviation routine weather report (METAR) for TFW was recorded at 1639 MST. It reported: wind from 190 degrees at 14 knots; visibility 10 miles; skies had scattered clouds at 3,900 feet above ground level (agl), ceiling broken at 6,000 feet agl; temperature 3 degrees C; dew point 1 degrees C; altimeter 30.10 inches of mercury. In the remarks of the METAR; station with precipitation discriminator, rain began at 1616 MST, snow ended at 1616 MST, trace hourly precipitation. At 1630, satellite imagery indicated that cloudy skies were present in the area of the accident site. For further information refer to the NTSB Weather Study, which is located in the docket for this accident. COMMUNICATION The Federal Aviation Administration (FAA) coordinator reported that no air traffic control facility reported communications with N2088G during the afternoon of March 8. WRECKAGE AND IMPACT INFORMATION According to the wreckage recovery personnel, the accident site was located in a small grove of 30-foot-high trees; the ground surrounding the accident site was covered in snow. The first identified point of contact (FIPC) was small broken trees. The left wing tip was found a few feet uphill from the FIPC. About 15 feet further uphill from the FIPC was a trench of disturbed dirt, about 40 feet in length and about 4 feet in depth. Paralleling and adjacent to the trench on the right side was the left wing. The right wing was further uphill near a second trench. The second trench of disturbed dirt was about 20 feet in length and about 2 feet in depth. Two propeller blades were found in the debris path about 70 feet from the FIPC. The engine, fuselage, and cabin area were found about 90 feet uphill from the FIPC. The fuselage had postimpact fire damage. Two additional propeller blades were located further in line with the debris path, with the furthest one observed about 322 feet from the FIPC. The debris path was oriented on a 30-degree uphill slope. MEDICAL AND PATHOLOGICAL INFORMATION The Twin Falls County Coroner’s Office completed an autopsy on the pilot. The cause of death was determined to be blunt force trauma due to an aircraft accident. Samples were submitted to the Federal Aviation Administration Civil Aeromedical Medical Institute, Oklahoma City, where they performed toxicological testing of specimens of the pilot. The report contained the following findings for tested drugs: dihydrocodeine detected in liver and lung; 42.9 (ug/ml, ug/g) fentanyl detected in the liver and 41 (ug/ml, ug/g) fentanyl detected in the lung; 0.368 (ug/ml, ug/g) Hydrocodone detected in liver and 0.234 (ug/ml, ug/g) Hydrocodone detected in lung; 0.24 (ug/ml, ug/g) Methamphetamine detected in the liver and 0.159 (ug/ml, ug/g) Methamphetamine detected in the lung; and rosuvastatin detected in the liver and lung. The Dihydrocodeine and hydrocodone found during the testing are medications used for pain relief, severe breathlessness, and often used to treat coughs. L-Methamphetamine is the active ingredient used in some over-the-counter nasal decongestants. TESTS AND RESEARCH The FAA was present during a follow-up engine examination of the engine. According to the FAA, no internal mechanical failures of the engine and no anomalies that would prevent the engine from operating could be identified. ADDITIONAL INFORMATION Spatial Disorientation The FAA's Advisory Circular 60-4A states in part, "The attitude of an aircraft is generally determined by reference to the natural horizon or other visual references with the surface. Spatial disorientation to a pilot means simply the inability to tell which way is "up." Surface references and the natural horizon may at times become obscured, although visibility may be above flight rule minimums. Lack of natural horizon or such reference is common at night, and especially at night in extremely sparsely populated areas, or in low visibility conditions. The disoriented pilot may place the aircraft in a dangerous attitude."
The non-instrument-rated pilot’s encounter with localized instrument meteorological conditions, which resulted in spatial disorientation and a loss of airplane control.
Source: NTSB Aviation Accident Database
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