# NTSB DEN01FA056: Beech V35B, N4637M, Green River, UT, February 26, 2001 - Type: NTSB accident investigation - Classification: Accident · Fatal · Field investigation · Final report - Date: February 26, 2001, 14:29 local (21:29 UTC) - Place: Green River, UT - Coordinates: 39.122776, -109.857498 - Nearby events: https://openairdocs.org/map.md?lat=39.1228&lon=-109.8575&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Fatal - Injuries: 1 fatal - Status: Completed, report July 25, 2002 - Report: Approved by Office Director - Parties: Teledyne Continental Motors, Raytheon Aircraft Company - NTSB case key (mKey): 51825 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN01FA056 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/51825/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=51825 - Page: https://openairdocs.org/ntsb/DEN01FA056 ## Probable cause the pilot's failure to maintain aircraft control as a result of incapacitation (from hypoxia) due to the in-flight decision to fly at altitudes where oxygen is required, without oxygen available. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of control - in flight, cruise - incapacitation(anoxia/hypoxia), pilot in command (cause) - in-flight planning/decision - improper, pilot in command (cause) - aircraft control - not maintained, pilot in command (cause) - stall/spin - inadvertent, pilot in command - In flight collision with terrain/water, descent - uncontrolled - terrain condition - mountainous/hilly ## Analysis The pilot had been skiing in the Rocky Mountains (elevation 8,900 feet) for a week. He departed in his non-pressurized single-engine airplane and climbed up to 21,600 feet; he had no supplemental oxygen onboard. Approximately 1 hour 45 minutes into the flight, the airplane reached a maximum altitude of 22,100 feet before entering a rapid descent. The airplane impacted mountainous terrain in an uncontrolled spin. Examination of the airplane and engine revealed no evidence of any pre-impact discrepancies. The Emergency Locator Transmitter (ELT) functioned properly, and the airplane was located by the Civil Air Patrol the following day. ## Factual narrative HISTORY OF FLIGHT On February 26, 2001, at 1429 mountain standard time, a Beech V35B, N4637M, was destroyed following impact with terrain during cruise near Green River, Utah. The non-instrument rated private pilot, the sole occupant in the airplane, was fatally injured. The airplane was being operated by the pilot under Title 14 CFR Part 91. The cross-country personal flight originated from Gunnison, Colorado, approximately 1 hour 45 minutes before the accident. Visual meteorological conditionts prevailed for the takeoff; however, the meterological conditions at the accident site are unknown. The pilot had not filed a flight plan; however, family members said the pilot was en route to Fresno, California. The pilot arrived in Gunnison, Colorado, on February 18, 2001, to ski at Crested Butte Ski Resort (elevation 8,900 feet). Airport personnel said the airplane was hangared for the next eight nights, and the main fuel tanks were topped off with 17.9 gallons of 100LL on the morning of the accident. They said that the pilot studied the weather and flight planned for over an hour. One airport employee said that the pilot had been to Gunnison before, and appeared alert and confident about his flight. According to FAA Air Route Traffic Control Center (ARTCC) radar data, the airplane was first identified at 1302:13, at 15,800 feet approximately 18 nautical miles (nm) west of Gunnison. The data indicates that the airplane tracked westbound and continued to climb to 20,600 feet at 1358:02. At 1413:04, the airplane performed a left 270 degree turn and leveled off at 21,600 feet on a north bound heading. The airplane's track veered west and then north; at 1427:09, the airplane reached a maximum altitude to 22,100 feet. Approximately 50 seconds later, at 1428:35, the radar data indicates the airplane was at 14,100 feet. Family members reported to Federal Aviation Administration (FAA) authorities that the pilot had not reached his destination. The pilot was not using any FAA services at the time of the accident. An Emergency Locator Transmitter (ELT) signal was received by U.S. Air Force tracking satellites. The Civil Air Patrol located the downed aircraft on February 27. PERSONNEL INFORMATION The pilot took his last FAA medical exam on June 20, 2000, and at that time he reported that he had 2,030 hours of flight experience. A small notebook found at the accident site suggested that the pilot had accumulated a total of 2,150 hours at the time of the accident. The notebook further indicated that he had flown 15 hours during the previous 90 days and 120 hours during the previous 12 months. FAA records indicate that the pilot received his private pilot certificate on July 2, 1981; he did not have an instrument rating. The pilot successfully completed his last FAA flight review on April 10, 1999. No documentation was found to indicate that the pilot had received hypoxia recognition training in an atmospheric chamber. AIRCRAFT INFORMATION The airplane was a single engine, propeller-driven, four seat airplane, which was manufactured by Beech Aircraft Company, in 1978. It was powered by a Teledyne Continental IO-550-B43B, six cylinder, reciprocating, horizontally opposed, direct drive, air cooled, fuel injected engine, which had a maximum takeoff rating of 300 horsepower at sea level. The last annual inspection was performed in Woodland, California, on April 7, 2000. At the time of the accident, the aircraft maintenance records and engine tachometer suggest that the airframe had accumulated approximately 2,473 flight hours. The airplane's engine was modified by a D'Shannon Supplemental Type Certificate (STC), #SA2200SW, which increased the power by 15 HP. A service ceiling is not published for the airplane before or after the engine modification. All performance charts provided for this airplane stop at 16,000 feet. The airplane's cabin was not pressurized, nor were there any personal supplemental oxygen systems found in the airplane. The airplane was equipped with an autopilot (Century one wing leveler), and was also equipped with long range fuel tanks (40 gallon capacity in each wing -- 37 usable per side). METEOROLOGICAL INFORMATION At 1456, the weather conditions at Grand Junction, Colorado (elevation 4,858 feet), 080 degrees 58 nautical miles (nm) from the accident site, were as follows: wind 350 degrees at 4 knots; visibility 10 sm; cloud condition overcast 5,000 feet; temperature 41 degrees Fahrenheit; dew point 30 degrees Fahrenheit; altimeter setting 30.05 inches of mercury. At 1453, the weather conditions at Moab, Utah, airport (elevation 4,553 feet), 150 degrees 25 nm from the accident site, were as follows: wind variable at 3 knots; visibility 10 sm; cloud condition scattered 1,800 feet and overcast 4,200 feet; light rain; temperature 37 degrees Fahrenheit; dew point 36 degrees Fahrenheit; altimeter setting 30.04 inches of mercury. At 1350, the weather conditions at Green River, Utah (elevation 4,225 feet), 200 degrees 20 nm from the accident site, were as follows: wind 180 degrees at 3 knots; visibility 25 sm; cloud condition overcast 6,000 feet; temperature 45 degrees Fahrenheit; dew point 32 degrees Fahrenheit. The National Weather Service reported the wind aloft (14,000 feet agl), over Grand Junction, Colorado, at 1600 was 215 degrees at 27 knots. The top of the moisture layer was reported to be about 20,000 feet msl. A rancher, who was in the vicinity of the impact site, said that "snow fell hard from 1000, to the time I left, around 1500." He also said that visibility was never greater than 50 to 100 feet. WRECKAGE AND IMPACT INFORMATION The airplane was found (N30 degrees, 7.36'; W109 degrees, 51.44'; elevation 6,672 feet) in a very rugged mountainous area called the Book Ends. The terrain was 50 percent covered with brush and cedar trees (maximum height of 20 feet). The airplane's propeller was found in a 1.5 foot deep crater, approximately 3 feet northeast of the engine. The airplane's longitudinal axis came to rest on a 090 degree orientation. A small bush next to the 1.5 foot deep crater had three distinctive slash cuts in it, which slope downwards approximately 20 degrees. All of the airplane's major components were accounted for at the accident site. The left wing remained attached to the carry-through spar, and the entire leading edge was compressed aft in an accordion like fashion. The right wing was destroyed and the outer 3 feet was found wrapped around a 8 to 10 inch diameter juniper tree. Both fuel tanks were hydraulically ruptured. The landing gear was retracted, and the wing flaps were up. The flight control surfaces were all identified, but flight control continuity to the cockpit could not be determined due to impact damage. The engine was displaced aft almost to the wing carry through spar; the instrument panel and firewall were wrapped around the rear of the engine. The fuselage and empennage were bent over the right wing. The engine was examined after the airplane was recovered from the accident site. The oil sump, induction tubing and the exhaust system were crushed and broken. The crankshaft could not be rotated; visual inspection of the crankshaft and camshaft through the bottom of the engine did not identify any separations or abnormalities. The nose section of the case was severely cracked in the area of the alternator mount. The right cylinders received considerable damage. The propeller spinner was crushed around the hub assembly, and all three propeller blades were displaced aft. All the blades exhibited leading edge polishing and slight "S" binding No preimpact engine or airframe anomalies, which might have affected the airplane's performance, were identified. There was no evidence of preimpact or postimpact fire. MEDICAL AND PATHOLOGICAL INFORMATION The State of Utah's Department of Health, ## Aircraft - Registration: [N4637M](https://openairdocs.org/deregistered/N4637M-2013-08-21), registration cancelled 2013-08-21, S/N D-10147, built 1978 (OpenAirDocs) - Reported make and model: Beech V35B - Registry model: [Beech V35B](https://openairdocs.org/model/beech-v35b) (registry code 1151548) (OpenAirDocs) - Registry engine: [Continental IO-520 series](https://openairdocs.org/engine/continental-io-520-series) (registry code 17032, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: D-10147 - Airframe hours: 2473 - Engines: Continental IO-550-B 300 horsepower reciprocating - Damage: Destroyed - Flight: Personal, Part 91 - Registered owner: Fred G. Poppe - Airworthiness certificate: Standard, Normal - Last inspection: Annual, April 7, 2000, 115 hours before - Departed: GUC, Gunnison, CO - Destination: FAT, Fresno, CA ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 56; injuries: fatal; private; airplane ratings: single-engine land; medical: class 3, with waivers/limitations; last flight review April 10, 1999; seat: left; toxicology performed; flight hours: 2,150 total, 15 in the last 90 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 180° at 3 knots - Visibility: 10 statute miles - Lowest ceiling: 6,000 ft overcast - Temperature: 45 °F, dew point 32 °F - Altimeter: 30.04 inHg - Observed at: U34, 20 nm away ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20010226004049A](https://openairdocs.org/incident/20010226004049A), Feb 26, 2001: Beech V35B, Green River, UT, Destroyed, 1 fatal. (-23) Pilot departed gunnison, Colorado at 1930 UTC, enroute to fresno, California. Aircraft did not arrive, ELT signal received and civil air patrol found… ## Docket (18 files) The files NTSB released with the investigation on July 3, 2002, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=51825. 11.3 MB in all. - Meteorology Group Chairman Factual Report (item 1, .PDF, 4.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40161612&FileExtension=.PDF&FileName=Meteorology%20Group%20Chairman%20Factual%20Report-Master.PDF - Witness Statements (item 2, .PDF, 61 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40161614&FileExtension=.PDF&FileName=Witness%20Statements-Master.PDF - Maps or Charts of Accident Area, Wreckage Diagrams (item 3, .PDF, 1.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40161616&FileExtension=.PDF&FileName=Maps%20or%20Charts%20of%20Accident%20Area,%20Wreckage%20Diagrams-Master.PDF - Weather Reports and Records (item 4, .PDF, 445 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40161618&FileExtension=.PDF&FileName=Weather%20Reports%20and%20Records-Master.PDF - Other Pertinent Forms and Reports (item 5, .PDF, 1.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40386699&FileExtension=.PDF&FileName=Other%20Pertinent%20Forms%20and%20Reports-Redacted.PDF - Statement of Party Representatives to NTSB Investigation (item 6, .PDF, 60 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40386706&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 7, .PDF, 39 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40386703&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Redacted.PDF - Toxicological Report (item 8, .PDF, 52 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40386709&FileExtension=.PDF&FileName=Toxicological%20Report-Redacted.PDF - Photo 1 - The empennage and fuselage of N4637M. (item 9, .PDF, 300 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40161628&FileExtension=.PDF&FileName=Photo%201%20-%20The%20empennage%20and%20fuselage%20of%20N4637M.-Master.PDF - Photo 2 - The right wing tip of N4637M. (item 10, .PDF, 205 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40161629&FileExtension=.PDF&FileName=Photo%202%20-%20The%20right%20wing%20tip%20of%20N4637M.-Master.PDF - Photo 3 - Looking from left wing tip to fuselage of N4637M. (item 11, .PDF, 369 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40161630&FileExtension=.PDF&FileName=Photo%203%20-%20Looking%20from%20left%20wing%20tip%20to%20fuselage%20of%20N4637M.-Master.PDF - Photo 4 - The main fuselage with slashed bush. (item 12, .PDF, 327 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40161631&FileExtension=.PDF&FileName=Photo%204%20-%20The%20main%20fuselage%20with%20slashed%20bush.-Master.PDF - Photo 5 - The bush with slash marks. (item 13, .PDF, 319 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40161632&FileExtension=.PDF&FileName=Photo%205%20-%20The%20bush%20with%20slash%20marks.-Master.PDF - Photo 6 - The bottom slash marks of the bush. (item 14, .PDF, 261 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40161633&FileExtension=.PDF&FileName=Photo%206%20-%20The%20bottom%20slash%20marks%20of%20the%20bush.-Master.PDF - Photo 7 - The left wing with aft accordian compression and hydraulic fuel tank deformation. (item 15, .PDF, 386 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40161634&FileExtension=.PDF&FileName=Photo%207%20-%20The%20left%20wing%20with%20aft%20accordian%20compression%20and%20hydraulic%20fuel%20tank%20deformation.-Master.PDF - Photo 8 - The 3-bladed propeller to N4637M. (item 16, .PDF, 252 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40161635&FileExtension=.PDF&FileName=Photo%208%20-%20The%203-bladed%20propeller%20to%20N4637M.-Master.PDF - Photo 9 - The propeller blade marked "B" with leading edge polishing and chordwise striations. (item 17, .PDF, 188 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40161637&FileExtension=.PDF&FileName=Photo%209%20-%20The%20propeller%20blade%20marked%20%22B%22%20with%20leading%20edge%20polishing%20and%20chordwise%20striations.-Master.PDF - Photo 10 - The engine to N4637M. (item 18, .PDF, 219 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40161638&FileExtension=.PDF&FileName=Photo%2010%20-%20The%20engine%20to%20N4637M.-Master.PDF From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.