# NTSB SEA06LA004: Beech G35, N4647D, Longview, WA, October 7, 2005 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: October 7, 2005, 14:00 local (21:00 UTC) - Place: Longview, WA - Coordinates: 46.163055, -122.948608 - Nearby events: https://openairdocs.org/map.md?lat=46.1631&lon=-122.9486&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report April 25, 2006 - Report: Approved by Office Director - Parties: FAA FSDO - NTSB case key (mKey): 62764 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA06LA004 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/62764/pdf - Page: https://openairdocs.org/ntsb/SEA06LA004 ## Probable cause Ruddervator flutter which resulted in the buckling of the empennage. The reason for the ruddervator flutter was undetermined. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, maneuvering - flight control,ruddervator - flutter (cause) - empennage - buckled (cause) ## Analysis The pilot was descending from 9,500 feet for weather, and while maneuvering around a cloud cell at 8,000 feet the airplane began to vibrate. He reduced power and rate of descent, and continued to his destination. After a normal landing, he discovered the "serious wrinkling" between the fuselage and the empennage. Postaccident evaluation of the airplane found no pre-existing cracking in the engine mounts; engine vibration analysis results were within limits. Ruddervator balance tests were also within limits. Radar data indicated that the airplane's maximum ground-track speed was 185 knots, or 213 mph. When this was corrected for altitude and winds aloft, the Investigator In Charge determined that the airplane's indicated airspeed should have been approximately 190 mph when it was descending through 8,000 feet. The airplane's Pilot's Operating Handbook (POH) states that this speed is in the airspeed indicator's yellow arc, or between 176 and 202 mph. The POH further states that maximum structural cruising speed (Vno) is 176 mph, and remarks, "Do not exceed this speed except in smooth air and then only with caution." ## Factual narrative On October 7, 2005, at approximately 1400 Pacific daylight time, a Beech G35, N4647D, was substantially damaged when it experienced an in-flight airframe vibration during a descent near Longview, Washington. The non-instrument rated private pilot, the sole occupant in the airplane, was not injured. The pilot/owner was operating the airplane under Title 14 CFR Part 91. Visual meteorological conditions prevailed for the personal, cross-country flight that originated from Oak Harbor, Washington, at approximately 1255. The pilot was flying on a VFR flight plan to Eugene, Oregon; he landed at 1508. The pilot said that he climbed to 9,500 feet, and was flying above clouds which gave him better visibility and radar contact. He said that he was approaching another band of clouds at his altitude and decided to descend through a "large break in the clouds." The pilot said there was no turbulence and it appeared to be a stable air mass below the clouds. He said that during his wings-level descent to the east, he reduced power to maneuver around a cloud cell. While descending through 8,000 feet at about 180 mph, he said that the airplane began to shake all over; there was no loss of flight control. The pilot said that he reduced power and rate of descent. The shaking stopped, and he continued his flight to Eugene. He said that after a normal landing, he discovered the "serious wrinkling" between the fuselage and the empennage. Postaccident evaluation of the airplane found no pre-existing cracking in the engine mounts; engine vibration analysis results were within limits. Ruddervator balance tests were also within limits. Radar data indicated that the airplane's maximum ground-track speed was 185 knots, or 213 mph. When this was corrected for altitude and winds aloft, the Investigator In Charge determined that the airplane's indicated airspeed should have been approximately 190 mph when it was descending through 8,000 feet. The airplane's Pilot's Operating Handbook (POH) states that this speed is in the airspeed indicator's yellow arc, or between 176 and 202 mph. The POH further states that maximum structural cruising speed (Vno) is 176 mph, and remarks, "Do not exceed this speed except in smooth air and then only with caution." ## Aircraft - Registration: [N4647D](https://openairdocs.org/aircraft/N4647D), registered now, S/N D-4803, built 1956 (OpenAirDocs) - Reported make and model: Beech G35 - Registry model: [Beech G35](https://openairdocs.org/model/beech-g35) (registry code 1151516) (OpenAirDocs) - Registry engine: [Continental E225 series](https://openairdocs.org/engine/continental-e225-series) (registry code 17015, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: D-4803 - Engines: Continental E225-8 260 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: John I. Cosman II - Airworthiness certificate: Standard, Normal - Departed: 76S, Oak Harbor, WA - Destination: EUG, Eugene, OR - Flight plan: VFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 61; injuries: none; private; airplane ratings: single-engine land; medical: class 3, with waivers/limitations; last flight review March 1, 2005; seat: left; flight hours: 379 total, 222 in this make and model, 338 as pilot in command, 23 in the last 90 days, 3 in the last 30 days, 3 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 280° at 4 knots - Visibility: 10 statute miles - Lowest ceiling: 3,500 ft overcast - Temperature: 59 °F, dew point 52 °F - Altimeter: 29.95 inHg - Observed at: KLS, 40 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 20051007025929A](https://openairdocs.org/incident/20051007025929A), Oct 7, 2005: Beech G35, Eugene, OR, Substantial damage. (-23) The pilot [privacy data omitted] states he was descending at 180MPH into portland, Oregon (pdx) airspace at 8000' AGL when he experienced a sudden and… ## Other investigations on N4647D (2) 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 SEA02LA116](https://openairdocs.org/ntsb/SEA02LA116), Jun 21, 2002: Beech G35 (N4647D), Yakima, WA, substantial damage. Probable cause: Empennage flutter which resulted in structural damage during descent for landing. Turbulence was a factor. - [NTSB CHI74FEP18](https://openairdocs.org/ntsb/CHI74FEP18), Oct 6, 1973: Beech V35G (N4647D), Manitowish W, WI, substantial damage 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.