NTSB CAROL · Event
Event CEN11LA357
Registry · N6850B
FAA Aircraft Registry record.
Make / Model
CESSNA T210M
Engine
CONT MOTOR TSIO-520 SER (300 hp)
Seats / Engines
6 seats · 1 engine
Last airworthiness date
19780812
ADS-B equipped
Yes — Mode-S A91824
Registrant of record
JENNINGS DONALD J
Source: FAA Aircraft Registry (releasable master file).
Aircraft involved
Probable cause & findings
Failure of the landing gear to fully extend due to a failed o-ring in the nose gear actuator piston and a broken seal in the emergency landing gear extension system.
Factual narrative
On May 21, 2011, at 1025 mountain daylight time, N6850B, a Cessna T210M, was substantially damaged during a gear up landing at Pueblo Memorial Airport (PUB), Pueblo, Colorado. The commercial pilot was not injured. The airplane was registered to and operated by the pilot. Visual meteorological conditions prevailed and no flight plan was filed for the personal flight conducted under 14 Code of Federal Regulations Part 91. According to the pilot, he departed Pueblo to conduct air work in the local area. After a normal take off, when the landing gear was retracted, he heard a "very unusual sound" that continued until the gear cycle was complete. He also noticed an amber gear warning light. The pilot leveled off at 7,500 feet and began to troubleshoot the problem by referencing the emergency procedures in the Pilot Operating Handbook (POH), which included two attempts to manually extend the gear. The pilot then checked the hydraulic fluid reservoir and it was empty. He then advised the tower of his situation and they suggested that he place a quart of engine oil in the hydraulic fluid reservoir and re-attempt a gear extension. The pilot added the oil and made another attempt to manually extend the landing gear, but to no avail. The pilot then flew by the control tower and tower personnel told him no gear was visible. The pilot said he then made a no-gear landing as directed by the POH on Runway 26R. According to the Pueblo Airport Operations Incident/Accident Report, the pilot landed with the nose gear down and locked and the main landing gear not down and locked. The airplane landed approximately 1,000 feet from the runway threshold. Upon touchdown, the nose gear remained extended and the main landing gear retracted. The airplane skidded on the belly and the tail before it came to rest approximately 400 feet east of taxiway A10. There was no fire. A Federal Aviation Administration (FAA) inspector performed an examination of the airplane and reported that the left horizontal stabilizer was substantially damaged. According to a representative of the repair facility that fixed the airplane, an o-ring in the nose gear actuator piston had failed. In addition, a seal in the emergency extension system had also failed. Once the failed o-ring and seal were replaced, the landing gear functioned normally. The pilot heard an unusual sound as he retracted the landing gear after takeoff and the amber gear warning light was illuminated. The pilot referenced the emergency procedures and made two unsuccessful attempts to manually extend the gear. After engaging the autopilot, the pilot then checked the hydraulic reservoir in the cockpit and it was empty. At the advice of an air traffic controller, the pilot added a quart of engine oil in the hydraulic reservoir and attempted another manual gear extension. The pilot was still unable to extend the gear. The pilot made a low pass by the control tower and a controller informed him that no landing gear were visible. The pilot then made a gear-up landing as directed by the Pilot Operating Handbook; however, according to airport personnel, the pilot landed with the nose gear down and the main landing gear retracted. The airplane skidded on its belly and the left horizontal stabilizer was damaged. According to a representative of the repair facility that fixed the airplane, an o-ring in the nose gear actuator piston had failed. In addition, a seal in the emergency extension system had also failed. Once the failed o-ring and seal were replaced, the landing gear functioned normally. Source: NTSB Aviation Accident Database Retrieved: 2026-02-12
NTSB Findings
Hierarchical cause / factor breakdown from the FAA bulk avdata database. Each finding tagged C (Cause) or F (Factor).
- C Aircraft-Aircraft systems-Landing gear system-Landing gear actuator-Failure - C
Verbatim from NTSB's published report. Source file
NTSB_2011_CEN11LA357.txt.
Findings + structured fields enriched from FAA avall.mdb.
Full investigation docket on
data.ntsb.gov ↗.
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Related research
What the literature says.
Academic papers and agency reports matching this event's aircraft type or causal vocabulary (autopilot). Sourced from NASA NTRS, NTSB Safety Studies, FAA CAMI, AOPA Air Safety Institute, Embry-Riddle Scholarly Commons, arXiv, and the Semantic Scholar academic graph.
- arXiv 2025 · arXiv preprint
ROSflight 2.0: Lean ROS 2-Based Autopilot for Unmanned Aerial Vehicles
ROSflight is a lean, open-source autopilot ecosystem for unmanned aerial vehicles (UAVs). Designed by researchers for researchers, it is built to lower the barrier to entry to UAV research and acceler…
- arXiv 2025 · arXiv preprint
ROSplane 2.0: A Fixed-Wing Autopilot for Research
Unmanned aerial vehicle (UAV) research requires the integration of cutting-edge technology into existing autopilot frameworks.
- arXiv 2024 · arXiv preprint
A Data-Driven Autopilot for Fixed-Wing Aircraft Based on Model Predictive Control
Autopilots for fixed-wing aircraft are typically designed based on linearized aerodynamic models consisting of stability and control derivatives obtained from wind-tunnel testing.
- arXiv 2022 · arXiv preprint
Experimental Flight Testing of a Fault-Tolerant Adaptive Autopilot for Fixed-Wing Aircraft
This paper presents an adaptive autopilot for fixed-wing aircraft and compares its performance with a fixed-gain autopilot.
- arXiv 2021 · arXiv preprint
An Adaptive Digital Autopilot for Fixed-Wing Aircraft with Actuator Faults
This paper develops an adaptive digital autopilot for a fixed-wing aircraft and compares its performance with a fixed-gain autopilot.
- arXiv 2020 · arXiv preprint
Reinforcement Learning for Robust Missile Autopilot Design
Designing missiles' autopilot controllers has been a complex task, given the extensive flight envelope and the nonlinear flight dynamics.
Browse the full corpus — academia portal ↗