# NTSB SEA98LA091: Stephens Vortex, N9261N, Chinook, MT, June 9, 1998 - Type: NTSB accident investigation - Classification: Accident · Fatal · Limited investigation · Final report - Date: June 9, 1998, 05:45 local (11:45 UTC) - Place: Chinook, MT - Coordinates: 48.470901, -109.210594 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=48.4709&lon=-109.2106&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Fatal - Injuries: 1 fatal - Status: Completed, report February 11, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 42794 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA98LA091 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/42794/pdf - Page: https://openairdocs.org/ntsb/SEA98LA091 ## Probable cause The pilot's failure to maintain aircraft control for an undetermined reason. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of control - in flight, climb - aircraft control - not maintained, pilot in command (cause) - reason for occurrence undetermined (cause) - Altitude deviation,uncontrolled, descent - uncontrolled - In flight collision with terrain/water, descent - uncontrolled ## Analysis The private pilot, who was the builder of the gyroplane, had logged about 21 hours of flight time in gyroplanes, but did not have a gyroplane rating. A witness observed the gyroplane's departure and climb-out from the airport. When the gyroplane was approximately 400-500 feet AGL, the witness observed the nose pitch down slightly, then rapidly upward about 40 degrees, then down rapidly about 40 degrees below horizontal then back up as before. The witness said the gyroplane then seemed to fall nearly vertically downward to the ground, and speculated that there was some sort of catastrophic failure to the aircraft. FAA inspectors, however, found no evidence of inflight breakup, or a main rotor blade strike of the empennage. ## Factual narrative On June 9, 1998, approximately 0545 mountain daylight time, an amateur-built Stephens Vortex gyroplane, N9261N, was destroyed when it collided with terrain in an uncontrolled descent shortly after departure from the Chinook, Montana, airport. The private pilot, who was the owner and the sole occupant of the aircraft, was fatally injured. Visual meteorological conditions prevailed at the time of the accident. The aircraft burned after impact. There was no ELT on board the aircraft. The gyroplane had recently been issued a special airworthiness certificate. The private pilot, who was the builder of the gyroplane, had logged about 21 hours of flight time in gyroplanes, but did not have a gyroplane rating. A witness, who was flying in an airplane at the time of the accident, observed the gyroplane's departure from the airport, taking off from runway 08. He stated that the gyroplane "climbed on the runway heading to about 300 feet and made a left 90 degree turn. He flew about 1/2 mile to the north then made a 90 degree turn to the right and flew east about 1/2 mile. At that point, he was approximately 400-500 feet AGL [above ground level]. Suddenly the nose pitched down slightly, then rapidly upward about 40 degrees, then down rapidly about 40 degrees below horizontal then back up as before. He then seemed to fall nearly vertically downward to the ground. The aircraft looked as if it was being jerked around, falling like a leaf. Due to the fact I was in my aircraft at the time, I could not hear the engine. Having been around aviation all of my life, it appeared there was some sort of catastrophic failure to the aircraft." Statements were provided to the Safety Board concerning a main rotor blade repair that had been completed prior to this flight. FAA inspectors found no evidence of inflight breakup, or a main rotor blade strike of the empennage, and no evidence of a failed main rotor blade repair. ## Aircraft - Registration: [N9261N](https://openairdocs.org/deregistered/N9261N-1999-05-05), registration cancelled 1999-05-05, S/N 1 (OpenAirDocs) - Reported make and model: STEPHENS VORTEX - Registry model: [Stephens H James SPORTCOPTER VORTEX](https://openairdocs.org/model/stephens-h-james-sportcopter-vortex) (registry code 05630D4) (OpenAirDocs) - Category: Gyroplane, amateur-built - Serial number: 001 - Engines: Rotax 582 65 horsepower reciprocating - Damage: Destroyed - Fire: On-Ground - Flight: Personal, Part 91 - Registered owner: Howard J. Stephens - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Annual, May 5, 1998 - Departed: S71 ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 70; private; airplane ratings: single-engine land; medical: class 3, valid medical--w/ waivers/lim; seat: front; toxicology performed; flight hours: 2,322 total, 21 in this make and model, 7 in the last 90 days ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 36 °F, dew point 34 °F - Altimeter: 29.00 inHg - Observed at: KHV ## 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 19980609025689A](https://openairdocs.org/incident/19980609025689A), Jun 9, 1998: Chinook, MT, Destroyed, 1 fatal. (.4)The private pilot, who was the builder of the gyroplane, had logged about 21 hours of flight time in gyroplanes, but did not have a gyroplane rating. A… 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.