# NTSB NYC99LA139: Aero Commander 500S, N33PG, Windsor Locks, CT, June 12, 1999 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: June 12, 1999, 13:35 local (17:35 UTC) - Place: Windsor Locks, CT - Location: 41.9390° N, 72.6843° W: Placed by OpenAirDocs at BRADLEY INTL (BDL), within about a mile (OpenAirDocs) - Nearby events: https://openairdocs.org/map.md?lat=41.9390&lon=-72.6843&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report June 22, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 46595 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=NYC99LA139 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/46595/pdf - Page: https://openairdocs.org/ntsb/NYC99LA139 ## Probable cause Hydraulic system contamination which prevented normal landing gear extension. A factor was the misjudged landing flare by the flying pilot. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, approach - hydraulic system - contamination (cause) - landing gear,gear locking mechanism - disabled - Hard landing, landing - flare/touchdown - flare - misjudged, copilot/second pilot (contributing factor) ## Analysis The pilot in command was flying the airplane with a safety pilot onboard. After multiple approaches, when the landing gear was extended, only the nose landing gear extended. Unable to extend the main landing gear, the pilot in command requested that the second pilot perform the gear up landing, because of his greater experience. The propellers were feathered prior to touchdown, and the airplane touched down hard, crushing the lower aft fuselage. Examination of the hydraulic system revealed contamination in the system. According to the mechanic who worked on the airplane, '...the contamination caused the main gear uplock cylinder not to release and allow the gear to extend....' The airplane is not equipped with an alternate gear extension system, therefore, if the hydraulic uplock valve cannot be released, the main gear cannot be extended. ## Factual narrative On June 12, 1999, at 1335 eastern daylight time, an Aero Commander 500S, N33PG, was substantially damaged while landing at the Bradley International Airport (BDL), Windsor Locks, Connecticut. The two certificated airline transport pilots were not injured. Visual meteorological conditions prevailed for the proficiency flight. No flight plan had been filed for the flight that was conducted under 14 CFR Part 91. The purpose of the flight was pilot proficiency. The pilot-in-command (PIC) and airplane owner occupied the left seat, while the second pilot (safety pilot) occupied the right seat. The PIC reported that the flight originated from Westchester County Airport (HPN), White Plains, New York, and was planned to terminate there. During one of the approaches the landing gear selector was placed in the down position, and the nose landing gear extended; however, the main landing gear failed to extend. The pilots elected to retract the landing gear and diverted to BDL due to its better weather. At the request of the PIC, the runway was foamed for the landing. The safety pilot stated: "...Prior to being cleared for the approach, I asked the owner if he wanted to make the landing. He said he felt that I had more experience and asked that I do it...." The safety pilot further stated: "...At approximately 1130 EDT we were cleared, and I made the approach at a slightly lower airspeed than I normally would, and touched down on the foam in a slightly nose-high attitude. The aircraft came to rest straight ahead, right side up...." An inspector from the Federal Aviation Administration (FAA) reported that both engines had been shut down and the propellers feathered when the airplane was on short final. He interviewed witnesses who reported that the airplane appeared to drop in from about 50 feet. Examination of the airplane revealed that the lower aft fuselage was crushed upward. The crushing was visible on the lower 1/2 of the aft fuselage. Examination of the landing gear extension sequence revealed that during landing gear retraction, the air in the emergency extension air cylinder was compressed, and the landing gear was held retracted by the uplocks. Normal landing gear extension ported hydraulic pressure to remove the uplocks, after which the landing gear is extended by the pressure in the emergency air cylinder. If the uplocks cannot be removed with hydraulic pressure, there is no alternate method of landing gear extension. After the accident, the airplane hydraulic system was examined and found to be full of fluid. The airplane was placed on jacks and hydraulic power applied. The landing gear, which had been previously extended, was retracted with no problems noted. The landing gear selector was then placed in the down position, and the nose landing gear extended; however, the main landing gear failed to extend. Examination of the landing gear wing flap control valve found contamination in the system. According to a letter from the FAA, the technician who examined the airplane reported, "...the contamination caused the main gear uplock cylinder not to release and allow the gear to extend...." ## Aircraft - Registration: [N33PG](https://openairdocs.org/aircraft/N33PG), registered now, S/N 1782-5 (OpenAirDocs) - Reported make and model: Aero Commander 500S - Registry model: [Aero Commander 500 S](https://openairdocs.org/model/aero-commander-500-s) (registry code 0141107) (OpenAirDocs) - Registry engine: [Lycoming TI0-540 series](https://openairdocs.org/engine/lycoming-ti0-540-series) (registry code 41533, turbo-prop) (OpenAirDocs) - Category: Airplane - Serial number: 1782-5 - Airframe hours: 5157 - Engines: Lycoming IO-540 290 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Registered owner: John L. Finlayson - Airworthiness certificate: Standard, Utility - Last inspection: Annual, June 30, 1999, 6 hours before - Departed: HPN, WHITE PLAINS, NY - Destination: BDL - Airport: BDL, Bradley Intl Airport, runway 33, 6,846 × 150 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 70; commercial, airline transport, flight instructor; airplane ratings: single-engine sea, single-engine land, multi-engine land; instrument ratings: airplane; medical: class 3, valid medical--w/ waivers/lim; seat: left; flight hours: 3,900 total, 2,800 in this make and model, 3,000 as pilot in command, 30 in the last 90 days, 25 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 130° at 7 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 81 °F, dew point 63 °F - Altimeter: 30.00 inHg - Observed at: BDL ## 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 19990612022039A](https://openairdocs.org/incident/19990612022039A), Jun 12, 1999: Gulstm 500S, Windsor Locks, CT, Substantial damage. On June 12, 1999, about 1330 eastern daylight time, an aero commander 500S, N33PG, was substantially damaged while landing at the Bradley International Airport… 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.