# NTSB ERA21LA021: Beech 99, N499CZ, Waterville, ME, October 14, 2020 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: October 14, 2020, 08:20 local (12:20 UTC) - Place: Waterville, ME - Coordinates: 44.531471, -69.676932 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=44.5315&lon=-69.6769&mi=10 - Phase of flight: [Taxi](https://openairdocs.org/ntsb-phases/250) (OpenAirDocs' grouping) - Defining event: [Taxi-from runway: Landing gear collapse](https://openairdocs.org/ntsb-events/094) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Eastern Region Aviation - Parties: Textron Aviation, FAA/FSDO - NTSB case key (mKey): 102152 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA21LA021 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/102152/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=102152 - Page: https://openairdocs.org/ntsb/ERA21LA021 ## Probable cause A failure of the right main landing gear drag leg support fitting and angle bracket as a result of multiple areas of fatigue cracking. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Landing gear system: main landing gear attach sec](https://openairdocs.org/ntsb-findings/01023211): Aircraft › Aircraft systems · Fatigue/wear/corrosion (probable cause); cases with it: [Beech 99A, 1 case](https://openairdocs.org/ntsb-findings/01023211/cases.md?model=1154003), [All aircraft, 66 cases](https://openairdocs.org/ntsb-findings/01023211/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Taxi-from runway: Landing gear collapse](https://openairdocs.org/ntsb-events/094) (defining event); cases with it: [Beech 99A, 2 cases](https://openairdocs.org/ntsb-events/094/sequence.md?model=1154003), [All aircraft, 1,787 cases](https://openairdocs.org/ntsb-events/094/sequence.md) ## Analysis While taxiing to the ramp, the airplane’s right main landing gear collapsed, resulting in substantial damage to the right wing. Examination of the right main landing gear drag leg support fitting and angle bracket revealed several areas of fatigue cracking with multiple origins. The attach angle bracket fracture exhibited features consistent with fatigue. The reason for the crack initiation could not be determined. A review of the maintenance procedures performed on the right main landing gear 8 days prior to the accident found that they instructed the mechanic to add grease to the drag leg fitting. The procedures did not specify to examine the landing gear for fatigue cracking or anomalies; therefore, it is unlikely that the mechanic would have looked in the area of the cracked main landing gear drag leg support fitting and angle bracket. Furthermore, there was no nondestructive testing procedures for examining the main landing gear drag brace, so it’s unlikely an inspection would have detected the multiple areas of fatigue cracking. ## Factual narrative On October 14, 2020, about 0820 eastern daylight time, a Beechcraft 99, N499CZ, was substantially damaged when it was involved in an accident at Waterville Robert LaFleur Airport (WVL), Waterville, Maine. The commercial pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 135 cargo flight. According to the pilot, the landing at WVL was not “firm or hard” and during the landing roll, he used reverse thrust and minimal braking to slow the airplane to a “standard taxi speed.” As he initiated a right turn to exit the runway onto the taxiway, the airplane’s right main landing gear collapsed, resulting in substantial damage to the right wing. An examination of the airplane by the Federal Aviation Administration (FAA) inspector who responded to the site revealed the drag leg of the right main landing gear was fractured. According to FAA airworthiness records, the airplane was manufactured in 1969. It was maintained with an approved aircraft inspection program. The airplane’s most recent inspection was completed on October 6, 2020, at an airframe time of 39,544.45 hours. At that time, the right main landing gear was lubricated in accordance with the operator’s approved aircraft inspection program. The guidance instructed the mechanic to add grease to the drag leg fitting. It did not instruct the mechanic to examine the landing gear for fatigue cracking or anomalies. An overhaul of the right main landing gear drag brace was performed every 7,500 flight cycles or 120 months. The most recent overhaul was performed on March 23, 2017, at an airframe total time of 38,485.5 hours. There were no nondestructive testing inspection procedures for the main landing gear drag braces prior to the accident. The National Transportation Safety Board Materials Laboratory examined the right drag leg support fitting and right main landing gear attach angle bracket. Examination of the right drag leg support fitting revealed the presence of several areas of pre-existing progressive fractures originating at the outer surface of the part with radial marks emanating inward, visible curved crack arrest marks, and microscopic striations consistent with fatigue. The largest fatigue crack originated at an external radius feature where parallel gouges and periodic depressions were observed on the adjacent surface. The smaller fatigue cracks originated at internal radii and features resembling ratchet marks were observed at each location, consistent with multiple initiation sites. The attach angle bracket fracture exhibited features consistent with fatigue emanating from the nut plate side and the opposite drag leg support fitting interface side. ## Aircraft - Registration: [N499CZ](https://openairdocs.org/aircraft/N499CZ), registered now, S/N U-81, built 1969 (OpenAirDocs) - Reported make and model: BEECH 99 (A) - Registry model: [Beech 99A](https://openairdocs.org/model/beech-99a) (registry code 1154003) (OpenAirDocs) - Registry engine: [Pratt & Whitney PT6A series](https://openairdocs.org/engine/pratt-whitney-pt6a-series) (registry code 52032, turbo-prop) (OpenAirDocs) - Category: Airplane - Serial number: U-81 - Year built: 1969 - Airframe hours: 39544.45 - Engines: Pratt & Whitney Canada PT6A-28 680 horsepower turbo prop; Pratt & Whitney Canada PT6A-28 680 horsepower turbo prop - Damage: Substantial damage - Flight: Part 135 - Operator: Freight Runners - Registered owner: N499cz LLC - Airworthiness certificate: Standard, Normal - Last inspection: AAIP, October 6, 2020 - Departed: MHT, Manchester, NH - Destination: Same as departure - Flight plan: IFR - Airport: WVL, Waterville Robert LaFleur Airport, runway 23, 5,500 × 100 ft, asphalt - Equipment: Electronic multifunction display, Electronic primary flight display, Onboard weather, Stall warning system, ADS-B, Auto-pilot, Electronic flight bag or handheld device ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 28; injuries: none; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, with waivers/limitations; last flight review September 18, 2020; seat: left; restraint: 4-point; flight hours: 1,656 total, 577 in this make and model, 1,081 as pilot in command, 144 in the last 90 days, 30 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 330° at 3 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 50 °F, dew point 48 °F - Altimeter: 29.72 inHg - Observed at: KWVL - METAR: KWVL 141156Z AUTO 33003KT 10SM CLR 10/09 A2972 RMK AO2 SLP093 60002 70224 T01000089 10100 20083 51015 ## 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 20201014016389A](https://openairdocs.org/incident/20201014016389A), Oct 14, 2020: Beech 99A, Waterville, ME, Substantial damage. Landing on runway 23 at wvl (Waterville, Maine), the aircraft touched down and on the rollout to the turn onto the taxiway, the right main landing gear… ## Docket (8 files) The files NTSB released with the investigation on September 30, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=102152. 24.7 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 2.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13818659&FileExtension=pdf&FileName=LA021%206120_Redacted-Rel.pdf - Most recent maintenance work cards (item 2, PDF, 23 pages, 4.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14277546&FileExtension=pdf&FileName=Most%20Recent%20Maintenance%20N499CZ%20Work%20Cards_Redacted-Rel.pdf - Memorandum for record - director of maintenance (item 3, PDF, 1 page, 199 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14487037&FileExtension=pdf&FileName=Memorandum%20Of%20Record%20Color%20DOM%20Email-Rel.pdf - Right main landing gear overhaul maintenance (item 4, PDF, 1 page, 846 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14487603&FileExtension=pdf&FileName=N499CZ%20RH%20Gear_Redacted-Rel.pdf - Maintenance program excerpts - right main landing gear (item 5, PDF, 6 pages, 651 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14487213&FileExtension=pdf&FileName=Excerpts%20from%20AAIP-Rel.pdf - 22-005 Materials lab factual report (ERA21LA021) (item 6, PDF, 12 pages, 12 photos, 14.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13571568&FileExtension=pdf&FileName=22-005%20Materials%20Lab%20Factual%20Report%20(ERA21LA021)-Rel.pdf - Investigative photographs (item 7, PDF, 5 pages, 5 photos, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13819921&FileExtension=pdf&FileName=Photo%20Array%20LA021-Rel.pdf - Statement of party representatives to NTSB investigation (item 8, PDF, 9 pages, 289 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14469426&FileExtension=pdf&FileName=LA021%20Signed%20Party%20Form_Redacted-Rel.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.