# NTSB IAD04LA029: Cessna 421B, N421KS, Portland, ME, July 2, 2004 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: July 2, 2004, 19:36 local (23:36 UTC) - Place: Portland, ME - Coordinates: 43.64611, -70.308609 - Nearby events: https://openairdocs.org/map.md?lat=43.6461&lon=-70.3086&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report December 3, 2004 - Report: Approved by Office Director - Parties: FAA/FSDO - NTSB case key (mKey): 59582 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=IAD04LA029 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/59582/pdf - Page: https://openairdocs.org/ntsb/IAD04LA029 ## Probable cause Failure of the right main landing gear down-lock mechanism resulting in the collapse of the right main landing gear. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Gear collapsed, landing - roll - landing gear,gear locking mechanism - failure (cause) ## Analysis Line personnel reported to the pilot that while the airplane had been parked on the ramp, heavy wind and rain "hydroplaned" the airplane across the ramp about 25 feet. After takeoff, the pilot retracted the landing gear and noticed an unfamiliar "clunking" noise during the retraction cycle. During the approach to the destination airport, he extended the landing gear and noted all three of the landing gear down and locked indicator lights were green. Sometime during the rollout he heard the "clunk" noise again, and the right wing began to settle lower than normal. The airplane then began to veer to the right and came to rest in the grass on the right side of runway. Examination of the right main landing gear revealed that two components of the down-lock mechanism had broken. The parts were submitted to the Safety Board Materials Laboratory. Metallurgical examination of the mating fractures revealed features typical of overstress separation. The fractures contained no evidence of fatigue. ## Factual narrative On July 2, 2004, about 1936 eastern daylight time, a Cessna 421B, N421KS, was substantially damaged while landing at Portland International Jetport (PWM), Portland, Maine. The certificated private pilot and passenger were not injured. Visual meteorological conditions prevailed, and the airplane was operating on an instrument flight rules flight plan. The personal flight, which departed Groton-New London Airport (GON), Groton, Connecticut, at 1730, was conducted under 14 CFR Part 91. According to a written statement submitted by the pilot, prior to his departure from Groton, the airplane was involved in "thunderstorm activity" while parked on the ramp. Line personnel reported to him that heavy wind and rain "hydroplaned" the airplane across the ramp about 25 feet. Prior to departing Groton Airport, the pilot performed a preflight examination of the airplane and found no abnormalities. After takeoff, the pilot retracted the landing gear and noticed an unfamiliar "clunking" noise during the retraction cycle. The climb, cruise, and decent portions of the flight were all uneventful. During the approach to Portland Jetport, he extended the landing gear and noted all three of the landing gear down and locked indicator lights were green. The airplane touched down on the main landing gear, and as the airplane decelerated, it touched down softly on the nose wheel. Sometime thereafter, the pilot heard the "clunk" noise again, and the right wing began to "settle down lower than normal." The airplane then began to veer to the right side of the runway and came to rest in the grass on the right side of runway 29. Examination of the right main landing gear revealed that the upper right landing gear trunnion ear and the attaching drag brace end ear had broken. The parts were submitted to the Safety Board Materials Laboratory. Metallurgical examination of the mating fractures revealed features typical of overstress separation. The fractures contained no evidence of fatigue. The weather reported at Groton, on the day of the accident at 1649, included winds from 190 degrees at 7 knots gusting to 33 knots, and 3/4 statute miles visibility in heavy rain. ## Aircraft - Registration: [N421KS](https://openairdocs.org/aircraft/N421KS), registered now, S/N 421B0507, built 1973 (OpenAirDocs) - Reported make and model: Cessna 421B - Registry model: [Cessna 421B](https://openairdocs.org/model/cessna-421b) (registry code 2076014) (OpenAirDocs) - Registry engine: [Continental GTSIO-520-C](https://openairdocs.org/engine/continental-gtsio-520-c) (registry code 17035, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 421B-0507 - Airframe hours: 4310.1 - Engines: Teledyne Continental GTSIO-520-H 375 horsepower reciprocating; Teledyne Continental GTSIO-520-H 375 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, June 20, 2004, 8.5 hours before - Departed: GON, Groton, CT - Destination: PWM, Portland, ME - Flight plan: IFR - Airport: PWM, Portland International Jetport, runway 29, 6,800 × 150 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 57; injuries: none; private; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 3, valid medical--w/ waivers/lim; last flight review May 28, 2003; seat: left; flight hours: 4,312 total, 294 in this make and model, 46 in the last 90 days, 9 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 50° at 3 knots - Visibility: 6 statute miles - Lowest ceiling: none - Temperature: 68 °F, dew point 63 °F - Altimeter: 29.90 inHg - Observed at: PWM ## 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 20040702012529A](https://openairdocs.org/incident/20040702012529A), Jul 2, 2004: Cessna 421B, Portland, ME, Substantial damage. (-23) Pilot stated that he was cleared for harbor visual approach to runway 29 at pwm. Pilot stated he had normal approach and touchdown with full flaps, three… 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.