# NTSB MIA02LA089: Cessna 421C, N237SM, Tampa, FL, April 25, 2002 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: April 25, 2002, 17:45 local (21:45 UTC) - Place: Tampa, FL - Coordinates: 28.008888, -82.349441 - Nearby events: https://openairdocs.org/map.md?lat=28.0089&lon=-82.3494&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report September 30, 2003 - Report: Approved by Office Director - Parties: Cessna, FAA - NTSB case key (mKey): 54580 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=MIA02LA089 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/54580/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=54580 - Page: https://openairdocs.org/ntsb/MIA02LA089 ## Probable cause the fracture of the landing gear upper barrel due to fatigue cracking, caused by improper machining after the barrel was assembled during the manufacturing process, resulting in damage to the airplane. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, landing - aborted - landing gear - material defect, manufacturer (cause) - landing gear,main gear - fatigue (cause) - landing gear,main gear - fractured (cause) - Gear collapsed, landing - flare/touchdown ## Analysis According to the pilot's statement, after a landing and upon touchdown, he said he "…observed an abnormal touchdown...and knew there was a mechanical problem." He aborted the landing, cycled the gear twice, and noted the gear unsafe light had remained illuminated. He then returned to the departure airport, for further assessment of the landing gear situation by the tower personnel. The tower personal confirmed there was damage to the left main gear, He then proceeded to burn off about 1 1/2 hours of fuel before attempting a landing. The pilot landed on the grass next to the paved runway, touching down on the nose and right main landing gears. Examination of the landing gear revealed that the upper barrel (p/n 5141002-11) fractured as result of fatigue cracking, above a brazed-on collar, as a result of improper machining after the barrel was assembled during the manufacturing process. ## Factual narrative On April 25, 2002, about 1745 eastern daylight time, a Cessna 421C, N237SM, operated and registered to MBA Graphics of Tampa, struck the ground after landing with the left main gear retracted at Vandenberg Airport, Tampa, Florida. Visual meteorological conditions prevailed at the time. No flight plan was filed for the 14 CFR Part 91 personal flight. The airplane was substantially damaged. The commercial-rated pilot reported no injuries. The flight had departed from the same airport about 1445, en route to Plant City, Florida. According to the pilot's statement, after a landing and upon touchdown at Plant City, he said he "…observed an abnormal touchdown...and knew there was a mechanical problem." After noticing the mechanical problem, he aborted the landing, cycled the gear twice, and noted that the gear unsafe light remained illuminated. He then proceeded to his departure airport, for further assessment of the landing gear situation by the tower personnel. The tower personal confirmed there was damage to the left main gear, he then proceeded to burn off about 1 1/2 hours of fuel before attempting a landing. The pilot landed on the grass next to the paved runway, touching down on the nose and right main landing gears. The airplane settled on the left wing, turned left onto the paved runway and came to rest 180 degrees opposite the direction of touchdown. Examination of the landing gear after the accident revealed that the upper barrel (p/n 5141002-11) fractured during the landing attempt at Plant City. The fractured upper barrel assembly was examined at Cessna's Material and Process Engineering's Laboratory. The purpose of the examination was to determine the cause of the main landing gear (MLG) fracture. Based on the observations made during the examination of the fractured MLG barrel, and according to Cessna's factual report, the following conclusions were reached: 1.) The upper barrel broke at a location coinciding with the position of the collar, "approximately 3-9/16 inches below the trunnion." 2.) "Pre-existing cracking was present on the trunnion barrel at two separate locations approximately 180 degrees apart," along the outer diameter of the barrel. "Fatigue cracks had propagated through approximately 75 to 80 percent of the wall thickness of the barrel." 3.) The crack origins coincided with "...a transition in barrel wall thickness. Machining marks were present on the radius of the transition in wall thickness." 4.) The dimensions of the barrel "were according" to the engineering drawing with the exception of the location of "...the brazed-on collar, where the outer barrel diameter was smaller than specified." Sectioning of the barrel through the fracture surface showed the presence of a "groove machined" into the barrel immediately above the collar. 5.) Smaller than specified barrel diameter and the presence of machining marks on the machined radius "…could have contributed to the cause of cracking." The surface roughness at the radius was 140-160 µ-in (micro-inches), which "exceeded" the engineering drawing requirement of 125 µ-in. 6.) The barrel chemical composition and hardness "were according" to the engineering drawing. The thickness of the braze metal between the barrel and the collar "met the requirements" for a Class I or Class II copper braze joint per CSMP009 as well as the requirements of CES2044 which is listed on the engineering drawing. A review of the Cessna report by the NTSB's Materials Laboratory revealed that the Cessna factual report contained an adequate factual description of the fracture, dimensional measurements, and other features associated with the fracture of the upper barrel. ## Aircraft - Registration: [N237SM](https://openairdocs.org/aircraft/N237SM), registered now, S/N 421C0237, built 1976 (OpenAirDocs) - Reported make and model: Cessna 421C - Registry model: [Cessna 421C](https://openairdocs.org/model/cessna-421c) (registry code 2076016) (OpenAirDocs) - Registry engine: [Continental GTSI0-520-F-K](https://openairdocs.org/engine/continental-gtsi0-520-f-k) (registry code 17031, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 421C-0237 - Airframe hours: 3670.5 - Engines: Continental GTSIO-520L 375 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: MBA Graphics Inc - Airworthiness certificate: Standard, Normal - Last inspection: Annual, October 29, 2001, 40 hours before - Departed: VDF, Tampa, FL - Destination: PCM, PLANT CITY, FL - Airport: VDF, Vandenberg, runway 23, 5,000 × 100 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 26; injuries: none; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, valid medical--no waivers/lim.; last flight review April 18, 2002; seat: left; flight hours: 2,500 total, 40 in this make and model, 2,390 as pilot in command, 200 in the last 90 days, 65 in the last 30 days, 8 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 0° at 0 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 86 °F, dew point 70 °F - Altimeter: 30.04 inHg - Observed at: VDF ## 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 20020425007599A](https://openairdocs.org/incident/20020425007599A), Apr 25, 2002: Cessna 421C, Tampa, FL, No damage. (.19) On April 25, 2002, about 1740 eastern daylight time, a Cessna 421C, N237SM, registered to mba graphics of Tampa, struck the ground after landing with the… ## Docket (4 files) The files NTSB released with the investigation on July 16, 2003, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=54580. 2.3 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 324 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40433831&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Cessna Notes (item 2, .PDF, 34 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40181508&FileExtension=.PDF&FileName=Cessna%20Notes-Master.PDF - Statement of Party Representatives to NTSB Investigation (item 3, .PDF, 322 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40433832&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.PDF - Cessna report on MLG upper barrel (item 4, .PDF, 14 photos, 1.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40183583&FileExtension=.PDF&FileName=Cessna%20report%20on%20MLG%20upper%20barrel-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.