# NTSB ANC10TA080: Aviat A-1B, N20HY, Bettles Field, AK, August 31, 2010 - Type: NTSB accident investigation - Classification: Accident · No injuries · Final report - Date: August 30, 2010, 21:34 local (Aug 31, 2010, 05:34 UTC) - Place: Bettles Field, AK - Coordinates: 67.343887, -151.221115 - Nearby events: https://openairdocs.org/map.md?lat=67.3439&lon=-151.2211&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing: Miscellaneous/other](https://openairdocs.org/ntsb-events/900) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report May 11, 2011 - Report: Approved by Office Director - NTSB office: Alaska Regional Office - Parties: U S Department of the Interior, FAA FSDO-01 - NTSB case key (mKey): 77149 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC10TA080 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/77149/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=77149 - Page: https://openairdocs.org/ntsb/ANC10TA080 ## Probable cause The pilot's selection of an unsuitable off-airport landing site for a precautionary landing. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Runway/land/takeoff/taxi surface](https://openairdocs.org/ntsb-findings/03023000): Environmental issues › Physical environment · Contributed to outcome - [Power plant](https://openairdocs.org/ntsb-findings/01057100): Aircraft › Aircraft power plant · Not specified - [Planning/preparation](https://openairdocs.org/ntsb-findings/02061000): Personnel issues › Task performance · Pilot (probable cause) ## Analysis The pilot reported that during the flight he observed smoke in the cockpit and smelled burning oil. He noted a rise in oil temperature, followed by a decrease in oil pressure, and an unusual vibration in the floorboards, control stick, and rudder. He elected to make a precautionary landing on a sandbar. He reported that on short final to the sandbar, he turned the fuel and electrical systems off, and that the propeller was windmilling. While landing, the left wingtip hit brush and the airplane veered to the left, at which point the right wingtip struck the ground. The airplane then nosed down and the propeller struck the sandbar. A postaccident examination revealed that the engine oil was at a normal level and did not smell burned; no evidence of leaks were found. The engine was removed from the airplane and successfully run on an engine test stand with no mechanical anomalies or leaks noted. An examination of the propeller showed aft bending and torsional twisting, with multiple leading edge gouges and chordwise scratching, consistent with the propeller being under power and striking the ground multiple times during the landing. ## Factual narrative On August 30, 2010, about 2134 Alaska daylight time, an Aviat A-1B airplane, N20HY, sustained substantial damage during a landing on a sandbar, about 35 miles northwest of Bettles Field, Alaska. The airplane was being operated by the U.S. National Park Service as a law enforcement surveillance public use flight, under Title 14, Code of Federal Regulations Part 91. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on September 3, an investigator for the Department of the Interior (DOI) said the pilot related to him that during cruise flight in a remote area, he saw that the engine oil temperature was increasing, and the engine oil pressure was decreasing into the yellow caution area of the pressure gauge. The pilot reported that he selected a sandbar upon which to land. The pilot related that during the landing flare the left wingtip hit some brush causing the airplane to yaw to the left. He reported that the right wing and propeller struck the ground. In a written report to his employer, the pilot reported that during the flight he saw smoke in the cockpit, and smelled hot/burning oil. He also said he saw a rise in engine oil temperature, and a decrease in oil pressure. Based on those observations he elected to make a precautionary landing on a sandbar. He noted that he also felt an uncharacteristic vibration in the stick, rudder, and floorboards. The pilot reported that on short final to the sandbar he turned the fuel and electrical systems off, and indicated the propeller was windmilling. During the landing he said the left wingtip got into the brush, and the airplane veered to the left, with the right wingtip striking the ground. The airplane nosed down, and the propeller struck the sandbar. At the accident site, the DOI investigator said he checked the airplane engine oil level, and the dipstick indicated about 6 quarts. After recovery, sitting on a level ramp, he said the dipstick indicated 6.5 quarts. After removing the cowlings, he said he found a small spot of oil on the exhaust pipe below the engine oil dipstick/filler tube. The engine was removed from the airplane, and on September 10, under the supervision of the NTSB IIC, the engine was started and run on an engine test stand. No mechanical anomalies or leaks were noted, and temperatures and pressures were within normal limits during the test run. An examination of the propeller showed aft bending, torsional twisting, and numerous leading edge gouges and chordwise scratching, consistent with the propeller contacting the ground several times. In their final report provided to the NTSB, the DOI investigator reported that "from the mishap site to the Bettles airport was actually 30.4 miles, which at a cruise speed of 110 mph would take just over 16 minutes. A direct route to Coldfoot was 28 miles and would have taken approximately 15 minutes. An NPS [National Park Service] mentor pilot who flew the route between theaccident site and Bettles stated that since the engine was still operating the pilot could have flown towards Bettles and if the engine failed there were numerous areas of willow and alder trees that could have been used for a forced landing. He also stated there are ample, suitable gravel bars closer to Bettles." ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Miscellaneous/other](https://openairdocs.org/ntsb-events/900) - [Enroute-cruise: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440) - [Landing: Miscellaneous/other](https://openairdocs.org/ntsb-events/900) (defining event) - [Landing: Nose over/nose down](https://openairdocs.org/ntsb-events/096) ## Aircraft - Registration: [N20HY](https://openairdocs.org/aircraft/N20HY), registered now, S/N 2001, built 1998 (OpenAirDocs) - Reported make and model: AVIAT AIRCRAFT INC A-1B - Registry model: [Aviat A-1B](https://openairdocs.org/model/aviat-a-1b) (registry code 2210406) (OpenAirDocs) - Registry engine: [Lycoming 0-360-A1D](https://openairdocs.org/engine/lycoming-0-360-a1d) (registry code 41504, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 2001 - Airframe hours: 1903 - Engines: LYCOMING O-360-A1D 180 horsepower reciprocating - Damage: Substantial damage - Flight: Public aircraft - federal, Public use - Operator: National Park Service, doing business as Gates of the Arctic National Park - Registered owner: United States Department Of Interior - Airworthiness certificate: Standard, Normal - Last inspection: Annual, June 21, 2010 - Departed: PACX, Coldfoot, AK - Destination: PABT, Bettles Field, AK - Flight plan: Company VFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 33; injuries: none; commercial; airplane ratings: single-engine sea, single-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; last flight review March 3, 2010; seat: front; flight hours: 1,600 total, 450 in this make and model, 1,450 as pilot in command, 175 in the last 90 days, 50 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 360° at 2 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 61 °F, dew point 36 °F - Altimeter: 29.77 inHg - Observed at: PABT, 35 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 20100830044439A](https://openairdocs.org/incident/20100830044439A), Aug 30, 2010: Aviat Aircr A-1B, Wiseman, AK, Substantial damage. During cruise flight, pilot smelled smoke/hot engine smell. Pilot decided to make a precautionary landing on a short gravel bar and damaged wing tip and… ## Docket (5 files) The files NTSB released with the investigation on February 4, 2011, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=77149. 1.8 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 572 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40342903&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Pilot Report (item 2, .PDF, 990 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40342908&FileExtension=.PDF&FileName=Pilot%20Report-Redacted.PDF - Engine Run Log (item 3, .PDF, 42 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40342909&FileExtension=.PDF&FileName=Engine%20Run%20Log-Master.PDF - Annotated Photo 1 (item 4, .PDF, 86 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40342929&FileExtension=.PDF&FileName=Annotated%20Photo%201-Master.PDF - Annotated Photo 2 (item 5, .PDF, 80 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40342930&FileExtension=.PDF&FileName=Annotated%20Photo%202-Master.PDF From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date; 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.