# NTSB ANC13LA026: Isaak Paul G Isaak Super CUB, N130Z, Sterling, AK, February 28, 2013 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Limited investigation · Final report - Date: February 28, 2013, 15:10 local (19:10 UTC) - Place: Sterling, AK - Coordinates: 60.551109, -150.790283 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=60.5511&lon=-150.7903&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-low-alt flying: Loss of control in flight](https://openairdocs.org/ntsb-events/240) - Highest injury: Serious injuries - Injuries: 2 serious - Status: Completed, report December 11, 2013 - Report: Approved by Office Director - NTSB office: Alaska Regional Office - Parties: Federal Aviation Administration - NTSB case key (mKey): 86349 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC13LA026 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/86349/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=86349 - Page: https://openairdocs.org/ntsb/ANC13LA026 ## Probable cause The pilot’s failure to maintain adequate airspeed while maneuvering at low altitude, which resulted in an aerodynamic stall. ## 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: [Isaak Paul G ISAAK SUPER CUB, 1 case](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=05611UG), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md) - [Performance/control parameters: airspeed](https://openairdocs.org/ntsb-findings/01062010): Aircraft › Aircraft oper/perf/capability · Not attained/maintained; cases with it: [Isaak Paul G ISAAK SUPER CUB, 1 case](https://openairdocs.org/ntsb-findings/01062010/cases.md?model=05611UG), [All aircraft, 1,681 cases](https://openairdocs.org/ntsb-findings/01062010/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering-low-alt flying: Loss of control in flight](https://openairdocs.org/ntsb-events/240) (defining event); cases with it: [Isaak Paul G ISAAK SUPER CUB, 1 case](https://openairdocs.org/ntsb-events/240/sequence.md?model=05611UG), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) - [Maneuvering-low-alt flying: Aerodynamic stall/spin](https://openairdocs.org/ntsb-events/241); cases with it: [Isaak Paul G ISAAK SUPER CUB, 1 case](https://openairdocs.org/ntsb-events/241/sequence.md?model=05611UG), [All aircraft, 1,529 cases](https://openairdocs.org/ntsb-events/241/sequence.md) - [Maneuvering-low-alt flying: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Isaak Paul G ISAAK SUPER CUB, 1 case](https://openairdocs.org/ntsb-events/470/sequence.md?model=05611UG), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis A witness familiar with the accident airplane stated that the pilot would typically make a low pass after a flight to let friends or family members know he was back. Due to injuries sustained in the accident, the pilot was unable to remember anything about the accident. According to the passenger, the pilot was making a second low pass over friends just before the accident. Witnesses reported seeing the airplane flying very slowly, about 300 feet above the ground, with the engine at a low power setting. The airplane’s right wing dipped and it subsequently entered a near vertical spiraling descent, collided with a tree and came to rest in a snow bank. The airplane sustained substantial damage to the wings, lift struts, and fuselage. No evidence of any preimpact mechanical anomaly was discovered during the postaccident examination of the airplane and engine. Given the lack of evidence of any mechanical problems, the passenger and witness’s account of the accident, along with the airplane’s near vertical descent, it is likely that the pilot inadvertently stalled the airplane at low altitude and was unable to recover. ## Factual narrative On February 28, 2013, about 1510 Alaska standard time, a ski-equipped, experimental/homebuilt Isaak Super Cub airplane, N130Z, sustained substantial damage when it collided with terrain following an in-flight loss of control, about 2 miles northwest of Sterling, Alaska. The airplane was being operated by the pilot as a visual flight rules (VFR) personal flight, under 14 Code of Federal Regulations, Part 91, when the accident occurred. The certificated private pilot and passenger sustained serious injuries. Visual meteorological conditions prevailed, and no flight plan was filed. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge on February 29, a witness who was familiar with the accident airplane stated that, typically when the pilot retuned from a flight, he would make a low pass to let friends or family members know he was back. During the accident flight, the witness stated that the engine seemed to be running smoothly, although the engine was operating at low power setting. He said that the airplane was flying very slowly, approximately 300 feet above ground level, and then it “appeared to drop out of the sky.” The airplane entered a nose down, near vertical spiraling descent to the right, collided with a tree, and came to rest in a snow bank adjacent to a house. The witness added that during the vertical descent, the engine rpm increased significantly, which continued until impact. On February 29, 2013, a Federal Aviation Administration (FAA) airworthiness inspector from the Anchorage Flight Standards District Office, traveled to the accident site, and examined the airplane. The inspector reported that his examination revealed no preaccident mechanical anomalies that would have precluded normal operation. Due to injuries sustained in the accident, the passenger was unable to be interviewed until after his recovery. During a telephone conversation with NTSB, IIC on April 19 the passenger seated in the rear seat stated that the purpose of the flight was to go look at a moose kill, and spot for coyotes in the area. The flight departed a remote frozen snow-covered lake near his house. Upon their return they spotted some friends, and made a low pass at approximately 200 feet above the ground. They had come around for a second pass, flaps were set at one notch, and the airplane was running smoothly, when the right wing dipped, and the airplane rolled over impacting the ground. The airplane sustained substantial damage to the wings and fuselage. Due to injuries sustained in the accident, the pilot was unable to be interviewed until after his recovery. During a telephone conversation with the NTSB IIC on April 19, 2013, the pilot reported that he was unable to remember anything about the accident. The pilot did not submit an NTSB Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1). ## Aircraft - Registration: [N130Z](https://openairdocs.org/aircraft/N130Z), registered now, S/N 01, built 2001 (OpenAirDocs) - Reported make and model: ISAAK PAUL G ISAAK SUPER CUB - Registry model: [Isaak Paul G ISAAK SUPER CUB](https://openairdocs.org/model/isaak-paul-g-isaak-super-cub) (registry code 05611UG) (OpenAirDocs) - Registry engine: [Lycoming O&VO-360 series](https://openairdocs.org/engine/lycoming-o-vo-360-series) (registry code 41514, reciprocating) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: 01 - Engines: LYCOMING O&VO-360 SER 180 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Special, Experimental (Special) - Departed: Sterling, AK ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 36; injuries: serious; private; airplane ratings: single-engine land; medical: class 3, unknown; seat: front ## Weather - Conditions: Visual (VMC), Day - Wind: 10° at 8 knots - Visibility: 10 statute miles - Lowest ceiling: 7,500 ft broken - Temperature: 32 °F, dew point 27 °F - Altimeter: 29.34 inHg - Observed at: PAEN, 15 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 20130228003219A](https://openairdocs.org/incident/20130228003219A), Feb 28, 2013: Isaak Paul G ISAAK SUPER CUB, Soldotna, AK, Substantial damage. Aircraft had recently received an annual condition inspection and flew 30 minutes on the day of the accident on conventional type landing gear. The pilot and… ## Docket (1 files) The files NTSB released with the investigation on September 28, 2013, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=86349. 50 KB in all. - Record of Conversation (item 1, .PDF, 50 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40399680&FileExtension=.PDF&FileName=Record%20of%20Conversation-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.