# NTSB CEN20LA185: Cessna 501, N501KM, Houston, TX, May 20, 2020 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: May 19, 2020, 19:30 local (May 20, 2020, 00:30 UTC) - Place: Houston, TX - Coordinates: 29.6459, -95.2769 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=29.6459&lon=-95.2769&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing-flare/touchdown: 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: Central Region - Parties: FAA FSDO - NTSB case key (mKey): 101313 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN20LA185 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/101313/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=101313 - Page: https://openairdocs.org/ntsb/CEN20LA185 ## Probable cause The malfunction of the left main landing gear down lock, which resulted in a gear collapse upon landing. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Landing gear system: landing gear actuator](https://openairdocs.org/ntsb-findings/01023233): Aircraft › Aircraft systems · Malfunction (probable cause); cases with it: [Cessna 501, 1 case](https://openairdocs.org/ntsb-findings/01023233/cases.md?model=2076603), [All aircraft, 54 cases](https://openairdocs.org/ntsb-findings/01023233/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Landing-flare/touchdown: Landing gear collapse](https://openairdocs.org/ntsb-events/094) (defining event); cases with it: [Cessna 501, 1 case](https://openairdocs.org/ntsb-events/094/sequence.md?model=2076603), [All aircraft, 1,787 cases](https://openairdocs.org/ntsb-events/094/sequence.md) ## Analysis On final approach to his destination airport, the pilot lowered the landing gear for a full stop landing. He received two of three green landing gear down position indicator lights. The left main landing gear light was not illuminated, and a warning horn sounded. The pilot recycled the landing gear and received the same result. The pilot queried the tower and another airplane to confirm that his landing gear were extended, and both told the pilot that they saw all three gear extended. Consistent with airplane manufacturer guidance, the pilot then performed maneuvers to generate lateral G-force on the landing gear in an attempt to get a gear locked indication on the left main gear, which was not successful. Upon landing, the left main landing gear collapsed, and the airplane veered off the runway, resulting in substantial damage to the left wing and underbelly of the airplane. Examination of the airplane’s landing gear system revealed the internal down lock mechanism of the left main landing gear actuator malfunctioned. The cockpit gear position indicator lights functioned normally. There were no recent logbook entries concerning anomalies with the left main landing gear. ## Factual narrative On May 19, 2020, about 1930 central daylight time, a Cessna 501, N501KM, sustained substantial damage when it was involved in an accident at Houston Hobby Airport (HOU), Houston, Texas. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. While on final approach to HOU, the pilot lowered the landing gear and received two of three green landing gear position indicator lights. The left main landing gear light was not illuminated, and a warning horn sounded. The pilot recycled the landing gear with the same result. He reported the situation to HOU tower and asked if they could visually see whether all the airplane’s landing gear were down. The tower reported that all gear appeared down, as did the pilot of a commercial airliner who was taxiing on the airport. As per the pilot operating handbook, the pilot initiated an aggressive bank right, followed abruptly by a left bank to generate sufficient lateral G-forces on the landing gear in an attempt to get a gear locked indication on the left main gear. This attempt did not work. Upon landing, left main landing gear collapsed, the airplane veered left and came to a stop in a grassy area adjacent to runway resulting in structural damage to the left wing and underbelly of the airplane. The pilot exited the airplane and airport emergency services responded. Recovery personnel manually lifted and locked the left main landing gear down, and the airplane was towed to a hangar facility. The pilot reported that he decided to land because the left main landing gear indicator light had malfunctioned in years past, and it was found that the light had malfunctioned rather than the landing gear. The landing gear was examined under the supervision of a Federal Aviation Administration (FAA) airworthiness inspector. Utilizing ground hydraulic and electrical power, the landing gear was cycled about 30 times with various hydraulic pressures. Both the nose landing gear and right main landing gear functioned normally. The cockpit landing gear position lights (nose, left main, and right main) functioned normally. The left landing gear actuator never locked in the down position under any hydraulic pressure setting. The only way to attain a locked down left main landing gear was to manually push the gear outward to the down and locked position. When the landing gear was pushed into the locked position, the left main landing gear down indicator light illuminated green. Evaluation of the left main landing gear actuator revealed that its internal down-lock mechanism was not functioning. According to the certified repair facility, the actuator is a component that is normally replaced at interval (37,000 cycles) or as needed. The FAA inspector reported that the aircraft logbook showed the left main actuator was original to the airplane and was last inspected on July 6, 2017, at 5,287 cycles. The logbook did not show any recent entries concerning anomalies with theleft main landing gear. ## Aircraft - Registration: [N501KM](https://openairdocs.org/deregistered/N501KM-2020-12-09), registration cancelled 2020-12-09, S/N 501-0101, built 1979 (OpenAirDocs) - Reported make and model: Cessna 501 (No Series) - Registry model: [Cessna 501](https://openairdocs.org/model/cessna-501) (registry code 2076603) (OpenAirDocs) - Registry engine: [Pratt & Whitney Canada JT15D-1A](https://openairdocs.org/engine/pratt-whitney-canada-jt15d-1a) (registry code 52110, turbo-fan) (OpenAirDocs) - Category: Airplane - Serial number: 501-0101 - Year built: 1979 - Airframe hours: 5585 - Engines: Pratt & Whitney JT15D-1A 2200 lbs thrust turbo fan; Pratt & Whitney JT15D-1A 2200 lbs thrust turbo fan - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: AAIP, December 16, 2019, 104 hours before - Departed: GNV, Gainesville, FL - Destination: HOU, Houston, TX - Flight plan: IFR - Airport: HOU, William P Hobby, runway 13R, 7,599 × 150 ft, asphalt - Equipment: Electronic multifunction display, ADS-B, Angle of attack indicator, Auto-pilot ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 71; injuries: none; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review October 18, 2019; seat: left; restraint: lap only; flight hours: 4,107 total, 1,324 in this make and model, 4,107 as pilot in command, 25 in the last 90 days, 10 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 200° at 11 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 86 °F, dew point 70 °F - Altimeter: 29.76 inHg - Observed at: HOU ## 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 20200519006259A](https://openairdocs.org/incident/20200519006259A), May 19, 2020: Cessna 501, Houston, TX, Substantial damage. Main landing gear selected down at or about 3 mile final, indicator revealed unsafe gear, controller and swa crew reported to PIC, gear down, the PIC elected… ## Docket (3 files) The files NTSB released with the investigation on June 24, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=101313. 4.7 MB in all. - NTSB form 6120 pilot operator report CEN20LA185 (item 1, PDF, 9 pages, 3.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14000731&FileExtension=pdf&FileName=NTSB%20Form%206120%20Pilot%20Operator%20Report%20CEN20LA185_Redacted-Rel.pdf - Memorandum for the record landing gear examination findings CEN20LA185 (item 2, PDF, 1 page, 119 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14001224&FileExtension=pdf&FileName=Memorandum%20for%20the%20Record%20Landing%20Gear%20Examination%20Findings%20CEN20LA185_Redacted-Rel.pdf - Photo array CEN20LA185 (item 3, PDF, 2 pages, 680 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14000626&FileExtension=pdf&FileName=Photo%20Array%20CEN20LA185-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.