# NTSB CHI94LA125: Cessna T210-M, N732YK, Pomona, MO, March 31, 1994 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: March 31, 1994, 17:15 local (23:15 UTC) - Place: Pomona, MO - Coordinates: 36.859802, -91.909782 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=36.8598&lon=-91.9098&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 3 uninjured - Status: Completed, report January 25, 1995 - Report: Approved by Office Director - NTSB case key (mKey): 9500 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI94LA125 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/9500/pdf - Page: https://openairdocs.org/ntsb/CHI94LA125 ## Probable cause The seperation of the landing gear door actuator, resulting in total loss of hydraulic fluid. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Gear not extended, approach - gear extension - not possible, pilot in command - hydraulic system,fitting - separation (cause) - fluid,hydraulic - loss,total (contributing factor) - On ground/water encounter with terrain/water, landing - roll - directional control - not possible (contributing factor) ## Analysis WHILE LOWERING THE WHEELS FOR LANDING, THE LEFT MAIN LANDING GEAR DOOR ACTUATOR PISTON SEPERATED FROM ITS CYLINDER, RESULTING IN A TOTAL LOSS OF HYDRAULIC FLUID. THE LEFT MAIN AND NOSE WHEEL LOCKED DOWN, AND THE RIGHT WHEEL REMAINED IN A TRAILING POSITION. AFTER FLYING FOR 2 MORE HOURS ATTEMPTING VARIOUS METHODS OF LOCKING THE RIGHT MAIN WHEEL DOWN, THE PILOT ELECTED TO LAND. DURING ROLLOUT, THE AIRPLANE DEPARTED THE RUNWAY AND SUSTAINED SUBSTANTIAL DAMAGE. THE SNAP RING WHICH RETAINS THE ROD END IN THE HYDRAULIC CYLINDER WAS INTACT BUT HAD SEPARATED FROM ITS RETENTION GROOVE. NO DAMAGE WAS APPARENT TO THE SNAP RING GROOVE. THE HYDRAULIC CYLINDER WAS REASSEMBLED AND ACTUATION TESTS WERE NORMAL WITH NO LEAKS. THERE WAS NO RECORD OF MAINTENANCE PERFORMED ON THE ACTUATOR WITHIN THE LAST 8 YEARS. LABORATORY INSPECTION REVEALED THAT THE GROOVE AND CYLINDER WERE MACHINED ACCORDING TO SPECIFICATIONS. THERE WAS A SLIGHT DEFORMATION OF THE GROOVE LIP, BUT IT COULD NOT BE DETERMINED TO BE PRE-EXISTING. ## Factual narrative On March 31, 1994, at 1715 hours central standard time, a Cessna 210, N732YK, operated by E. Beaver of McKinney, Texas, made an emergency landing with one main landing gear retracted at West Plains Municipal Airport, Missouri. The instrument rated commercial pilot and two passengers were not injured. Visual meteorological conditions existed at the time of the accident, winds were three knots, and no flight plan was filed. The flight operated under 14 CFR Part 91, and originated from Addison, Texas, at 1308 hours central standard time. Upon entry to the landing pattern at West Plains, the pilot observed unsafe landing gear indications. Visual inspection indicated that the right main wheel was not down and locked. The pilot orbited for two hours, obtained radio communications with a manufacturers representative, and attempted several methods to lock the wheels down, with no success. During troubleshooting, the hydraulic fluid reservoir was refilled with onboard engine oil, requiring 1 3/4 quarts. When landing gear extension was attempted, black fluid was observed venting overboard by ground personnel. The pilot landed with only the left and nose wheel locked down. On final approach, the engine was shut down. During landing the right wing contacted the ground and the aircraft departed the runway, damaging the propeller, right wing and right horizontal stabilizer. The last annual inspection was conducted September 1, 1993. No record of maintenance on the landing gear actuator system was noted since 1986. The airplane was recently purchased by the pilot/owner and had accumulated 7 hours under this ownership. The previous owner was Addison Aircraft Sales of Addison, Texas, who owned the airplane for a period of 3 months. Previous of Addison Aircraft Sales owning the airplane, it had a single owner since 1981. All maintenance was performed by the same individual. The last maintenance on the system was a left gear door replacement in 1990 due to structural door cracks. Post accident inspection revealed the Landing Gear Door Actuating Cylinder Piston (p/n 1281031-1) had seperated from the actuator cylinder (p/n 1281010-2F) during the landing gear extension cycle, allowing all hydraulic fluid to be pumped overboard. The snap ring (MS 16625-1068) which retains the piston within the cylinder was found attached but seperated from its retention groove. The assembly (p/n 1281028-1) was reassembled, and several retraction cycle tests were conducted. All cycles were successful with no leakage noted. Metallurgical examination of the actuator and snap ring revealed permanent deformation of the snap ring, and damage on the outboard lip of the snap ring groove. It could not be determined if these deformations were pre-existing or a result of the actuator seperation. The following machining dimensions (inches) were specified measured Inside Diameter (ID) of cylinder: .688-.690 .687-.688 Depth (radius)of snap ring groove: .020-.023 .020-.022 Diameter of snap ring groove: .730-.734 .727-.733 Width of snap ring groove: .039-.042 .035-.041 Distance from end of cylinder to edge of groove: .158-.161 .1566 Inside radius of groove closest to cylinder opening: .005R max .0032-.0039 ADDITIONAL INFORMATION The airplane was repaired and placed back into service. During the repairs, STC #SA5934SW for removal of the Landing Gear Doors and Actuator System was complied with. ## Aircraft - Registration: [N732YK](https://openairdocs.org/aircraft/N732YK), registered now, S/N 21061879, built 1977 (OpenAirDocs) - Reported make and model: CESSNA T210-M - Registry model: [Cessna T210M](https://openairdocs.org/model/cessna-t210m) (registry code 2073451) (OpenAirDocs) - Registry engine: [Continental TSIO-520 series](https://openairdocs.org/engine/continental-tsio-520-series) (registry code 17040, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 21061879 - Airframe hours: 2540 - Engines: CONTINENTAL TSIO-520-R 310 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: Eddie W. Beaver - Airworthiness certificate: Standard, Normal - Last inspection: Annual, September 1, 1993, 58 hours before - Departed: ADS, ADDISON, TX - Airport: UNO, West Plains Municipal, runway 18, 4,902 × 75 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 47; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 1,252 total, 7 in this make and model, 971 as pilot in command, 64 in the last 90 days, 23 in the last 30 days, 4 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 160° at 3 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 63 °F, dew point 25 °F - Altimeter: 30.00 inHg - Observed at: FLP, 45 nm away ## 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 19940331007289A](https://openairdocs.org/incident/19940331007289A), Mar 31, 1994: Cessna T210M, West Plains, MO, Substantial damage. Extending gear door acuator piston separated loosing hydraulic fluid. Landing r main folded. Cyl snap ring came out ## Other investigations on N732YK (1) 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. - [NTSB CEN09CA123](https://openairdocs.org/ntsb/CEN09CA123), Dec 31, 2008: Cessna T210M (N732YK), Fort Collins, CO, substantial damage. Probable cause: A total loss of engine power due to fuel starvation as a result of the pilot's failure to select the fullest tank before landing. 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.