# NTSB SEA07LA055: Cessna 421, N4584L, Pocatello, ID, January 30, 2007 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: January 30, 2007, 13:50 local (20:50 UTC) - Place: Pocatello, ID - Coordinates: 43.123611, -112.453887 - Nearby events: https://openairdocs.org/map.md?lat=43.1236&lon=-112.4539&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report May 29, 2007 - Report: Approved by Office Director - Parties: Salt Lake FSDO - NTSB case key (mKey): 65218 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA07LA055 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/65218/pdf - Page: https://openairdocs.org/ntsb/SEA07LA055 ## Probable cause The separation of the bolt that attaches the elevator trim tab actuator rod to the elevator trim tab horn, resulting in violent flutter of the elevator, and eventually to the separation of the inboard half of the right elevator. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, climb - to cruise - flight control,elevator tab - disconnected (cause) - flight control,elevator - flutter (cause) - flight control,elevator - separation (cause) ## Analysis During the climb to cruise altitude, the bolt that holds the elevator trim tab actuator rod to the trim tab horn came loose from its retaining nut and separated from the aircraft. This led to severe airframe vibration, and eventually to violent elevator flutter. As a result of the flutter, the inboard half of the right elevator separated from the airframe. By reducing power on the right engine, and adding power on the left engine, the pilot was able to crab the aircraft, reduce the airflow over the right stabilizer/elevator, and ultimately execute an emergency full-stop landing. ## Factual narrative On January 30, 2007, approximately 1350 mountain standard time, a Cessna 421, N4584L, experienced the in-flight separation of the inboard half of the right elevator while en route from Idaho Falls, Idaho, to American Falls, Idaho. The commercial pilot, who was the sole occupant, was not injured. The 14 CFR Part 91 aircraft repositioning ferry flight, which had been airborne for about 10 minutes, was being operated in visual meteorological conditions. The aircraft is owned and operated by Bully Dog Technologies of Aberdeen, Idaho. No flight plan had been filed. According to the pilot, while he was climbing through 9,400 feet for 10,500 feet, he heard a very large thud that he could feel through the control yoke. The event moved the control yoke back and forth, and although the pilot was not sure what had happened, he later said that it felt as if something had "...struck the elevator very hard." At that point, the pilot reduced power and headed toward the Blackfoot Airport. Although there initially seemed to be no significant aerodynamic effect, after about 60 seconds a very strong shudder/vibration began to occur, and the aircraft began a dive to the left. The pilot then reduced power further to maintain control. He then looked over his right shoulder, and was able to see the right stabilizer/elevator "fluttering violently." He then further reduced the power on the right engine, and added power to the left engine, which effectively crabbed the aircraft to the right and reduced the airflow over the right stabilizer/elevator. After taking the aforementioned remedial action, the aircraft stopped shaking/vibrating, and the pilot turned toward Pocatello Regional Airport in order to make use of its longer/wider runway. The pilot was eventually able to execute an emergency landing at Pocatello. After exiting the aircraft, the pilot discovered that the inboard one-half of the right elevator had departed the airframe while in flight. A post-accident inspection by an FAA Airworthiness Inspector found that the bolt that connects the elevator trim tab actuator rod to the elevator trim tab horn was missing, and neither the actuator rod end nor the tab horn had failed. There was no evidence of a bird impact, and the pilot had not seen a bird at the time the event was initiated. In both his written statement, and during a post-accident telephone interview, the pilot stated that he had manually adjusted the elevator trim a number of times prior to the initiation of the sequence of events, and that not only did the system work correctly, but that he had felt no looseness, roughness, or vibration in the system. He further stated that because this was an FAA -approved ferry flight, he had performed an extensive preflight prior to departure, to include the flight controls and their actuation systems. He said that during this inspection he confirmed that there were no nuts or bolts missing from the flight control actuation system. ## Aircraft - Registration: [N4584L](https://openairdocs.org/deregistered/N4584L-2015-05-15), registration cancelled 2015-05-15, S/N 421-0184, built 1968 (OpenAirDocs) - Reported make and model: Cessna 421 - Registry model: [Cessna 421](https://openairdocs.org/model/cessna-421) (registry code 2076010) (OpenAirDocs) - Registry engine: [Continental GTSIO-520-C](https://openairdocs.org/engine/continental-gtsio-520-c) (registry code 17035, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 421-0184 - Airframe hours: 4381 - Engines: Continental GTSIO-520-H 375 horsepower reciprocating - Damage: Substantial damage - Flight: Ferry, Part 91 - Registered owner: Bully Dog Technologies - Airworthiness certificate: Standard, Normal - Last inspection: Annual, September 1, 2006 - Departed: KIDA, Idaho Falls, ID - Destination: KU01, American Falls, ID ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 67; injuries: none; flight instructor, commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review February 1, 2006; seat: left; flight hours: 6,058 total, 2 in this make and model, 5,624 as pilot in command, 84 in the last 90 days, 28 in the last 30 days, 4 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Visibility: 25 statute miles - Lowest ceiling: none - Temperature: 30 °F ## 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 20070130000909A](https://openairdocs.org/incident/20070130000909A), Jan 30, 2007: Cessna 421, Pocatello, ID, Substantial damage. (-23) Ida to U01, climbing through 9400' MSL to 10500' MSL, pilot heard a bang, experienced flight control flutter and controllability issues. Pilot declared… ## Other investigations on N4584L (1) 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 FTW79FRG25](https://openairdocs.org/ntsb/FTW79FRG25), Apr 9, 1979: Cessna 421 (N4584L), Lakeway, TX, 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.