# NTSB ANC16LA035: Universal Stinson 108, N9063K, Big Lake, AK, June 26, 2016 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: June 25, 2016, 18:00 local (Jun 26, 2016, 02:00 UTC) - Place: Big Lake, AK - Coordinates: 61.610553, -150.084442 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=61.6106&lon=-150.0844&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) - Highest injury: Minor injuries - Injuries: 2 minor, 1 uninjured - Status: Completed, report October 17, 2017 - Report: Approved by Office Director - NTSB office: Alaska Regional Office - Parties: Federal Aviation Administration - NTSB case key (mKey): 93481 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC16LA035 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/93481/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=93481 - Page: https://openairdocs.org/ntsb/ANC16LA035 ## Probable cause A total loss of engine power during cruise flight for reasons that could not be determined because postaccident examination of the airframe and engine revealed no mechanical malfunctions or failures that would have precluded normal operation. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined (probable cause); cases with it: [Universal Stinson 108, 1 case](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=9230412), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md) - [Object/animal/substance: tree(s)](https://openairdocs.org/ntsb-findings/03022020): Environmental issues › Physical environment · Contributed to outcome; cases with it: [Universal Stinson 108, 1 case](https://openairdocs.org/ntsb-findings/03022020/cases.md?model=9230412), [All aircraft, 933 cases](https://openairdocs.org/ntsb-findings/03022020/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) (defining event); cases with it: [Universal Stinson 108, 2 cases](https://openairdocs.org/ntsb-events/342/sequence.md?model=9230412), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md) - [Enroute-cruise: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341); cases with it: [Universal Stinson 108, 3 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=9230412), [All aircraft, 3,824 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Emergency descent: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Universal Stinson 108, 2 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=9230412), [All aircraft, 10,152 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The private pilot stated that, about 35 minutes into the personal, local flight and while circling a friend's cabin about 550 ft above ground level, the engine began to "sputter," followed by a total loss of engine power. He subsequently made a forced landing in an area of densely populated trees, during which the airplane sustained substantial damage to the wings and fuselage. A postaccident examination of the airframe and engine revealed no mechanical malfunctions or anomalies that would have precluded normal operation. Although the wing fuel tanks had been modified and no Federal Aviation Administration major repair and alteration form nor entry in the airplane's maintenance records were found regarding the modification, no evidence was found indicating that the modification led to the loss of engine power. The reason for the loss of engine power could not be determined. ## Factual narrative On June 25, 2016, about 1800 Alaska daylight time, a Stinson 108 airplane, N9063K, sustained substantial damage during a forced landing, following a loss of engine power near Big Lake, AK. The airplane was registered to and operated by the pilot, as a visual flight rules (VFR) flight under the provisions of 14 Code of Federal Regulations (CFR) Part 91 when the accident occurred. Of the three people on board, the certificated private pilot and one passenger sustained minor injuries and one passenger was uninjured. Visual meteorological conditions prevailed, and no flight plan had been filed. The flight departed Merrill Field Airport (PAMR), Anchorage, Alaska, at about 1725. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on June 25, the pilot stated that the purpose of the flight was to take two family members, who were visiting from out of town, on a sightseeing flight. About 35 minutes into the flight, while circling a friend's cabin at about 550 feet above ground level, the engine began to "sputter" followed by a total loss of engine power. He made a forced landing in an area of densely populated spruce and birch trees. During the forced landing, the airplane sustained substantial damage to wings and fuselage. On October 12, 2016, the NTSB IIC, along with a Federal Aviation Administration (FAA) safety inspector from the Anchorage Flight Standards District Office examined the airframe and engine at the facilities of Alaska Claims Services, Inc., Wasilla, Alaska. The propeller remained attached to the engine crankshaft. Both propeller blades exhibited aft bending with minimal torsional "S" twisting. Examination of the Continental O-470R engine revealed no anomalies, contamination, or evidence of malfunction in any of the engine accessories. The cylinders, pistons, valve train, crankshaft, and other internal components were all without evidence of anomaly or malfunction. The engine was rotated by the propeller. When the engine was rotated, blue spark was observed on the top ignition leads. Examination of the airplane's wing fuel tanks revealed that the tanks had been modified. An additional section had been welded on to the factory fuel tank with lightening holes drilled in the factory end. Each tank was placarded near the filler cap on the exterior of the wing "FUEL 80/87 MINIMUM GRADE 20 GALLONS." The fuel selector inside the cockpit was placarded "18 GAL." No FAA form 337 (major repair and alteration) or logbook entry was located in the airplane's maintenance records for the modification of the fuel system. The examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. The closest weather reporting facility was Wasilla Airport, Wasilla, AK, about 19 miles east of the accident site. At 1756, a weather observation from Wasilla Airport was reporting, in part: wind from 080 degrees at 4 knots;visibility, 10 statute miles; clouds and sky condition, few clouds at 4,600 feet, scattered clouds at 5,500 feet, broken clouds at 7,500 feet; temperature, 66°F; dew point 48 °F; altimeter, 29.89 inHG. After repeated attempts, the pilot did not submit an NTSB Pilot/Operator Accident Report form (NTSB Form 6120.1) as required. ## Aircraft - Registration: [N9063K](https://openairdocs.org/aircraft/N9063K), registered now, S/N 108-2063, built 1947 (OpenAirDocs) - Reported make and model: UNIVERSAL STINSON 108 - Registry model: [Universal Stinson 108](https://openairdocs.org/model/universal-stinson-108) (registry code 9230412) (OpenAirDocs) - Registry engine: [Continental O-470R](https://openairdocs.org/engine/continental-o-470r) (registry code 17071, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 108-2063 - Year built: 1947 - Engines: CONT MOTOR O 470R 230 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Departed: PAMR, Anchorage, AK - Destination: PAMR, Anchorage, AK ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 44; injuries: minor; private; airplane ratings: single-engine land; medical: class 3, with waivers/limitations; seat: left; flight hours: 460 total ## Weather - Conditions: Visual (VMC), Day - Wind: 80° at 4 knots - Visibility: 10 statute miles - Lowest ceiling: 7,500 ft broken - Temperature: 66 °F, dew point 48 °F - Altimeter: 29.88 inHg - Observed at: PAWS, 19 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 20160625021419A](https://openairdocs.org/incident/20160625021419A), Jun 25, 2016: Universal Stinson 108, Phoebe Lake, AK, Destroyed. One pilot and two passengers on board. Pilot was circling in right hand turn at 600 feet. Engine started sputtering, lost power/airspeed and crashed into trees. ## Other investigations on N9063K (1) 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. - [NTSB MIA97LA144](https://openairdocs.org/ntsb/MIA97LA144), Apr 19, 1997: Stinson 108-1 (N9063K), Smithfield, NC, substantial damage. Probable cause: a fracture in the crankshaft, which resulted in a total loss of engine power, a forced landing, and a nose over. ## Docket (2 files) The files NTSB released with the investigation on August 31, 2017, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=93481. 595 KB in all. - Witness Statement (item 1, .PDF, 56 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40455812&FileExtension=.PDF&FileName=Witness%20Statement-Master.PDF - Photos (item 2, .PDF, 3 photos, 539 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40455813&FileExtension=.PDF&FileName=Photos-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.