# NTSB WPR10LA034: Aero Commander 690, N690TR, Cedar City, UT, October 21, 2009 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: October 21, 2009, 10:15 local (16:15 UTC) - Place: Cedar City, UT - Coordinates: 37.70111, -113.151664 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=37.7011&lon=-113.1517&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Defining event: [Approach: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report December 13, 2011 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 74975 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR10LA034 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/74975/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=74975 - Page: https://openairdocs.org/ntsb/WPR10LA034 ## Probable cause The failure of the landing gear accumulator/regulator and the installation of the improper priority valve, which precluded the landing gear from extending and locking into place. ## 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 · Failure (probable cause) - [Maintenance/inspections](https://openairdocs.org/ntsb-findings/01010500): Aircraft › Aircraft handling/service · Incorrect service/maintenance (probable cause) ## Analysis Upon arrival over the destination airport during a positioning flight, the pilot attempted to extend the airplane's landing gear. Only the nose gear and the left main landing gear locked in the down position. The pilot reported that he performed the emergency gear extension procedure specified in the airplane's flight manual, but the right main gear did not lock down. The pilot returned to the departure airport and landed. During rollout, the right main landing gear collapsed and the airplane slid off the runway resulting in substantial airframe damage. An examination of the airplane revealed that an accumulator/regulator in the extension system had malfunctioned. In addition, an incorrect priority valve was installed and precluded the gear from locking down. ## Factual narrative HISTORY OF FLIGHT On October 21, 2009, about 1015 mountain daylight time, an Aero Commander 690, N690TR, experienced the collapse of its right main landing gear during landing rollout at the Cedar City Regional Airport (CDC), Cedar City, Utah. The airplane was operated by Kolab Canyon Air Services, LLC, on a positioning flight to pick up passengers in Milford, Utah. Visual meteorological conditions prevailed at the time, and a company flight plan had been filed. The airplane was substantially damaged, and the commercial pilot was not injured. The flight was performed under the provisions of 14 Code of Federal Regulations Part 91, and it originated from CDC about 0709. The pilot reported to the National Transportation Safety Board investigator that he attempted to lower the landing gear on approach to Milford Municipal Airport. The nose gear and the left main landing gear locked in the down position. The right main landing gear did not fully extend. The pilot stated that, although he performed the emergency procedures specified in the airplane's flight manual to remedy the situation, the right landing gear failed to lock down. Thereafter, the pilot flew back to CDC where he landed. During rollout, the right main landing gear collapsed. As the airplane decelerated, it slid off the runway and came to rest in an adjacent dirt area. A subsequent examination of the airplane revealed several bent bulkheads and stringers. TESTS AND RESEARCH The operator reported that it maintained the airplane using the manufacturer's approved inspection program. No anomalies, including preexisting damage, was reported with the landing gear extension system. Following the accident, the airplane's landing gear operating system was examined. Two components associated with the gear extension system were bench tested for functionality. The accumulator/regulator (part number EA1563) and the priority valve (part number 2979-3 (790301-501)) did not meet specifications. Specifically, when the accumulator/regulator was serviced with nitrogen to the specified test pressure, the unit would not pressurize. When the priority valve was pressurized, it operated only below specified limits for its part number. According to the Federal Aviation Administration (FAA) coordinator, the inability of the accumulator/regulator to be pressurized resulted in the landing gear's failure to properly extend. Also, the priority valve that had been installed in the airplane was found to be an incorrect part. Twin Commander's technical service manager reported that the priority valve should have been part number 790301-505. Accordingly, installation of the improper valve "...most likely contributed to the failure of the landing gear to fully extend to the down and locked position." (See the report from Twin Commander and the Higher Planes bench test report, included in the Safety Board’s Document Management System, for additional information.) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Prior to flight: Aircraft maintenance event](https://openairdocs.org/ntsb-events/040) - [Approach: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event) - [Landing-landing roll: Landing gear collapse](https://openairdocs.org/ntsb-events/094) ## Aircraft - Registration: [N690TR](https://openairdocs.org/aircraft/N690TR), registered now, S/N 11034, built 1972 (OpenAirDocs) - Reported make and model: AERO COMMANDER 690 - Registry model: [Aero Commander 690](https://openairdocs.org/model/aero-commander-690) (registry code 0141720) (OpenAirDocs) - Registry engine: [Garrett TPE331-5](https://openairdocs.org/engine/garrett-tpe331-5) (registry code 29041, turbo-prop) (OpenAirDocs) - Category: Airplane - Serial number: 11034 - Airframe hours: 8065 - Engines: Garret TPE 331-5 717 horsepower turbo prop; Garret TPE 331-5 717 horsepower turbo prop - Damage: Substantial damage - Flight: Positioning, Part 91 - Operator: Kolob Canyons Air Services L L C - Registered owner: Career Aviation Sales Inc. - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, May 6, 2009 - Departed: CDC, Cedar City, UT - Flight plan: Company VFR - Airport: CDC, Cedar City Regional, runway 02, 8,653 × 150 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 25; injuries: none; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review April 4, 2009; seat: left; flight hours: 3,045 total, 360 in this make and model, 2,876 as pilot in command, 299 in the last 90 days, 27 in the last 30 days, 5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 10° at 11 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 45 °F, dew point 34 °F - Altimeter: 30.09 inHg - Observed at: CDC ## 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 20091021021399A](https://openairdocs.org/incident/20091021021399A), Oct 21, 2009: Gulstm 690, Cedar City, UT, Substantial damage. On October 21, 2009 N690TR, a twin commander 690, experienced a collapse of the RH main landing gear while attempting to land at Cedar City, UT (cdc). The… ## Docket (2 files) The files NTSB released with the investigation on October 28, 2011, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=74975. 2.1 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 651 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40321534&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - FAA & Twin Commander Reports (item 2, .PDF, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40346329&FileExtension=.PDF&FileName=FAA%20%26%20Twin%20Commander%20Reports-Redacted.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.