# NTSB ANC11LA027: Piper PA-32-301, N81052, Cold Bay, AK, April 15, 2011 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: April 14, 2011, 17:55 local (Apr 15, 2011, 01:55 UTC) - Place: Cold Bay, AK - Location: 55.1858° N, 162.7211° W: Placed by OpenAirDocs: center of Cold Bay, AK, within about 6 miles (OpenAirDocs) - NTSB coordinates: 55.733333, -162.983337, outside the stated state - Nearby events: https://openairdocs.org/map.md?lat=55.1858&lon=-162.7211&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Turbulence encounter](https://openairdocs.org/ntsb-events/360) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report August 22, 2011 - Report: Approved by Office Director - NTSB office: Alaska Regional Office - Parties: FAA FSDO-03 - NTSB case key (mKey): 78932 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC11LA027 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/78932/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=78932 - Page: https://openairdocs.org/ntsb/ANC11LA027 ## Probable cause An in-flight encounter with unforecast turbulence, which resulted in structural damage to the stabilator. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Empennage structure: spars/ribs (horizontal stab)](https://openairdocs.org/ntsb-findings/01035511): Aircraft › Aircraft structures · Damaged/degraded - [Turbulence: clear air turbulence](https://openairdocs.org/ntsb-findings/03032015): Environmental issues › Conditions/weather/phenomena · Effect on equipment (probable cause) ## Analysis The pilot reported that while descending toward his destination, the airplane encountered severe turbulence of short duration. After the turbulence passed, he made an uneventful landing at his destination airport. A postaccident examination of the airplane discovered substantial damage to the stabilator. The wind at the destination airport was reported as 310 degrees at 9 knots, the area forecast valid at the time of the turbulence encounter forecast no significant turbulence, and there were no pilot reports of turbulence. The pilot indicated that prior to the severe turbulence; there had been no significant turbulence during the flight. An examination of the stabilator showed that the right half was bent downward 5 to 10 degrees outboard of the fuselage attachments. No evidence of fatigue or corrosion was found. ## Factual narrative On April 14, 2011, about 1755 Alaska daylight time, a Piper PA-32 airplane, N81052, sustained substantial damage during an encounter with turbulence in cruise flight, about 13 miles west of Cold Bay, Alaska. The airplane was operated by Peninsula Airways, Inc., Anchorage Alaska, as a visual flight rules (VFR) cargo flight under 14 Code of Federal Regulations, Part 135. The solo airline transport pilot was not injured. Visual meteorological conditions prevailed, and company flight following procedures were in effect. The flight departed False Pass, Alaska, about 1745. In a written statement to the National Transportation Safety Board (NTSB) dated April 29, the pilot wrote that while descending toward his destination, the airplane encountered severe up and down drafts. During the encounter, the pilot hit his head on the sun visor, even though his seatbelt and shoulder harness were snug and secure. Afterward, he continued to his destination, and landed without incident. The wind at the destination airport at the time of the accident was reported as 300 degrees at 9 knots, the area forecast valid for the time of the accident, forecast no significant turbulence during the reporting period, and there were no pilot reports of turbulence in the area. The pilot said there were no preaccident mechanical problems with the airplane. A postaccident examination discovered substantial damage to the stabilator. An examination of the stabilator by the NTSB investigator-in-charge showed that the right half of the stabilator was bent downward 5-10 degrees outboard of the fuselage attachments. The bottom skins adjacent to the bend were wrinkled. The skins were removed, and revealed downward bending of the stabilator main spar. No signs of fatigue or corrosion were found. ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Turbulence encounter](https://openairdocs.org/ntsb-events/360) (defining event) ## Aircraft - Registration: [N81052](https://openairdocs.org/aircraft/N81052), registered now, S/N 32-8206023, built 1982 (OpenAirDocs) - Reported make and model: PIPER PA-32-301 - Registry model: [Piper PA-32-301](https://openairdocs.org/model/piper-pa-32-301) (registry code 7103207) (OpenAirDocs) - Registry engine: [Lycoming IO-540 series](https://openairdocs.org/engine/lycoming-io-540-series) (registry code 41530, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 32-8206023 - Airframe hours: 14089 - Engines: LYCOMING IO-540 SER 300 horsepower reciprocating - Damage: Substantial damage - Flight: Part 135 - Operator: Peninsula Airways Inc, doing business as PenAir - Registered owner: Peninsula Airways Inc - Airworthiness certificate: Standard, Normal - Last inspection: AAIP, March 17, 2011 - Departed: PAKF, False Pass, AK - Destination: PACD, Cold Bay, AK - Flight plan: Company VFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 58; injuries: none; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review June 23, 2010; seat: left; flight hours: 9,561 total, 4,038 in this make and model, 96 in the last 90 days, 27 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 310° at 9 knots - Visibility: 10 statute miles - Lowest ceiling: 3,000 ft broken - Temperature: 28 °F, dew point 18 °F - Altimeter: 29.97 inHg - Observed at: PACD, 13 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 20110414008799A](https://openairdocs.org/incident/20110414008799A), Apr 14, 2011: Piper PA-32-301, Cold Bay, AK, Substantial damage. The aircraft experienced severe turbulence in the Cold Bay area that caused damage to the horizontal stabilizer. ## Docket (1 files) The files NTSB released with the investigation on June 24, 2011, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=78932. 694 KB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 694 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40349521&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.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.