# NTSB GAA15LA265: Stinson 108, N6066M, Palmer, AK, September 20, 2015 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Limited investigation · Final report - Date: September 20, 2015, 12:10 local (20:10 UTC) - Place: Palmer, AK - Coordinates: 61.413333, -148.571395 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=61.4133&lon=-148.5714&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Defining event: [Approach-VFR pattern final: Loss of control in flight](https://openairdocs.org/ntsb-events/240) - Highest injury: Serious injuries - Injuries: 2 serious - Status: Completed, report June 1, 2016 - Report: Approved by Office Director - NTSB office: General Aviation Accidents - Parties: Anchorage FSDO (FAA) - NTSB case key (mKey): 92008 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=GAA15LA265 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/92008/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=92008 - Page: https://openairdocs.org/ntsb/GAA15LA265 ## Probable cause The pilot's failure to maintain adequate airspeed and his exceedance of the airplane’s critical angle-of-attack during final approach to landing, which resulted in an aerodynamic stall and impact with terrain. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Stinson 108-3, 9 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=9230408), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md) - [Performance/control parameters: angle of attack](https://openairdocs.org/ntsb-findings/01062042): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Stinson 108-3, 3 cases](https://openairdocs.org/ntsb-findings/01062042/cases.md?model=9230408), [All aircraft, 990 cases](https://openairdocs.org/ntsb-findings/01062042/cases.md) - [Performance/control parameters: airspeed](https://openairdocs.org/ntsb-findings/01062010): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Stinson 108-3, 3 cases](https://openairdocs.org/ntsb-findings/01062010/cases.md?model=9230408), [All aircraft, 1,681 cases](https://openairdocs.org/ntsb-findings/01062010/cases.md) - [Engine fuel and control: fuel control/carburetor](https://openairdocs.org/ntsb-findings/01057322): Aircraft › Aircraft power plant · Incorrect use/operation; cases with it: [Stinson 108-3, 1 case](https://openairdocs.org/ntsb-findings/01057322/cases.md?model=9230408), [All aircraft, 195 cases](https://openairdocs.org/ntsb-findings/01057322/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Approach-VFR pattern final: Aerodynamic stall/spin](https://openairdocs.org/ntsb-events/241); cases with it: [Stinson 108-3, 2 cases](https://openairdocs.org/ntsb-events/241/sequence.md?model=9230408), [All aircraft, 1,529 cases](https://openairdocs.org/ntsb-events/241/sequence.md) - [Approach-VFR pattern final: Loss of control in flight](https://openairdocs.org/ntsb-events/240) (defining event); cases with it: [Stinson 108-3, 5 cases](https://openairdocs.org/ntsb-events/240/sequence.md?model=9230408), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) - [Approach-VFR pattern final: Attempted remediation/recovery](https://openairdocs.org/ntsb-events/060); cases with it: [Stinson 108-3, 2 cases](https://openairdocs.org/ntsb-events/060/sequence.md?model=9230408), [All aircraft, 1,422 cases](https://openairdocs.org/ntsb-events/060/sequence.md) - [Approach-VFR pattern final: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Stinson 108-3, 15 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=9230408), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The private pilot was conducting a personal flight and was on final approach to land at a remote backcountry airstrip. The pilot reported that he applied carburetor heat for the approach and that he observed 60 mph (52.1 knots) on the airspeed indicator. He subsequently "pushed the throttle forward, but the engine sound remained constant." According to the pilot-rated passenger, as the pilot began to level the wings to align with the runway, the right wing "instantly…dropped to a 45 degree angle." He then observed the pilot immediately reach for the throttle but saw him inadvertently grab the carburetor heat lever instead. The airplane impacted terrain in a nose-low, right-wing-down attitude and came to rest on a hillside about 100 yards short of the landing area. The airplane sustained substantial damage to both wings and the fuselage. The pilot reported no mechanical malfunctions or failures with the airplane that would have precluded normal operation. It is likely that, during the final approach, the pilot did not maintain adequate airspeed and exceeded the airplane's critical angle-of-attack, which resulted in an aerodynamic stall. Although the pilot attempted to add power to recover from the stall, he inadvertently grabbed the carburetor heat lever instead of the throttle. ## Factual narrative On September 20, 2015, about 1210 Alaska daylight time, a Stinson 108-3 airplane, N6066M, impacted terrain during the final approach to land at a remote airstrip in the Knik Glacier area, about 19 miles south east of Palmer, Alaska. The pilot and pilot-rated passenger both sustained serious injuries. The airplane was registered to a private owner and was operated by the pilot as a 14 Code of Federal Regulations Part 91 personal flight. Day visual meteorological conditions prevailed for the flight, with no flight plan filed. The flight departed from Birchwood Airport (BCV), Birchwood, Alaska about 1140, and flew for 30 minutes prior to the accident. According to the pilot, he reported that the carburetor heat was applied for the landing. On final approach, the pilot remembered that the pilot-rated passenger stated, "Airspeed!" and he observed 60 MPH (52.1 knots) on his airspeed indicator. Subsequently, the pilot stated that he "pushed the throttle forward, but the engine sound remained constant." The pilot reported there were no mechanical malfunctions or failures with the airplane that would have precluded normal operation. According to the pilot-rated passenger who was sitting in the front right seat of the airplane, the pilot entered a 30 degree banked left turn to final, applied one notch of flaps, and stated his touchdown speed would be "55" Miles Per Hour (MPH) (47.8 knots). As the pilot began to level the wings for the final approach, "instantly the right wing dropped to a 45 degree angle." The passenger then observed the pilot immediately reach for the throttle, but saw him grab the carburetor heat lever. The airplane impacted terrain in a nose low, right wing down attitude, and came to rest on a hill side about 100 yards short of the landing area. The airplane sustained substantial damage to both wings and the fuselage. A witness on the ground, who was also a commercial pilot, observed the accident airplane's traffic pattern. The witness stated that the accident airplane was lined up with the runway and then "suddenly the right wing dropped, and the left wing came up" and added, "the airplane fell out of the sky, he just stalled." He also stated that he could hear a "steady low power setting, and never heard the engine get louder" during the approach. The witness was the first person to reach the airplane and observed the throttle quadrant; he stated that "the throttle lever was all the way out and was bent" and he could smell and see fuel leaking from both wings. ADDITIONAL INFORMATION According to 14 Code of Federal Regulations Part 61.56, "no person may act as pilot in command of an aircraft unless, since the beginning of the 24th calendar month before the month in which that pilot acts as pilot in command, that person has accomplished a flight review." The pilot reported that his last flight review was on May 1, 2012. According to the Stinson 108-3 Airplane Flying Manual, Performance Information Section, the stalling speed with flapsfull down is listed as 61.4 MPH (53.4 knots) and with flaps up is 64.5 MPH (56 knots). With a 10 degree angle of bank, the stalling speed listed with flaps full down is 62.0 MPH (53.9 knots) and with flaps up is 65 MPH (56.5 Knots). The Stinson 108-3 manual does not list stalling speeds for partial flap extensions. ## Aircraft - Registration: [N6066M](https://openairdocs.org/aircraft/N6066M), registered now, S/N 108-4066 (OpenAirDocs) - Reported make and model: STINSON 108 (3) - Registry model: [Stinson 108-3](https://openairdocs.org/model/stinson-108-3) (registry code 9230408) (OpenAirDocs) - Registry engine: [Franklin 6A4165 series](https://openairdocs.org/engine/franklin-6a4165-series) (registry code 27025, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 108-4066 - Year built: 1947 - Engines: FRANKLIN 6A4-165-B3 165 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, August 14, 2015 - Departed: BCV, BIRCHWOOD, AK - Destination: None, Palmer, AK - Airport: runway NONE, 1,500 × 30 ft, gravel - Equipment: None ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 60; injuries: serious; private; airplane ratings: single-engine land; medical: class 3, with waivers/limitations; last flight review May 1, 2012; seat: left; restraint: 4-point; flight hours: 406 total, 250 in this make and model, 367 as pilot in command, 14 in the last 90 days, 4 in the last 30 days - Pilot-rated passenger; age 56; injuries: serious; private; airplane ratings: single-engine land; medical: class 3, without waivers/limitations; seat: right; restraint: 4-point; flight hours: 72 total, 0 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: 160° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 46 °F, dew point 34 °F - Altimeter: 29.69 inHg - Observed at: PAAQ, 29 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 20150920016479A](https://openairdocs.org/incident/20150920016479A), Sep 20, 2015: Stinson 108-3, Palmer, AK, Substantial damage. N6066M, a Stinson S108 aircraft, was attempting to land at the "picnic table airstrip," which is located near the base of the knik glacier (approximately… ## Docket (8 files) The files NTSB released with the investigation on March 7, 2016, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=92008. 3.3 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 1.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40437317&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Record of Conversation (Pilot in Command 1) (item 2, .PDF, 53 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40437318&FileExtension=.PDF&FileName=Record%20of%20Conversation%20(Pilot%20in%20Command%201)-Master.PDF - Record of Conversation (Pilot in Command 2) (item 3, .PDF, 52 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40437319&FileExtension=.PDF&FileName=Record%20of%20Conversation%20(Pilot%20in%20Command%202)-Master.PDF - Record of Conversation (Pilot Rated Passenger 1) (item 4, .PDF, 55 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40437320&FileExtension=.PDF&FileName=Record%20of%20Conversation%20(Pilot%20Rated%20Passenger%201)-Master.PDF - Record of Conversation (Pilot Rated Passenger 2) (item 5, .PDF, 53 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40437321&FileExtension=.PDF&FileName=Record%20of%20Conversation%20(Pilot%20Rated%20Passenger%202)-Master.PDF - Record of Conversation (Witness on Ground) (item 6, .PDF, 53 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40437322&FileExtension=.PDF&FileName=Record%20of%20Conversation%20(Witness%20on%20Ground)-Master.PDF - Stinson 108-3 Airplane Flight Manual (item 7, .PDF, 260 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40437323&FileExtension=.PDF&FileName=Stinson%20108-3%20Airplane%20Flight%20Manual-Master.PDF - Photos (Courtesy of FAA and Airplane Owner) (item 8, .PDF, 2 photos, 868 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40437316&FileExtension=.PDF&FileName=Photos%20(Courtesy%20of%20FAA%20and%20Airplane%20Owner)-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.