Wednesday, May 31, 2017

Cessna U206G Stationair, N9420R, Civil Air Patrol: Accident occurred November 15, 2014 at Brackett Field Airport (KPOC), La Verne, Los Angeles County, California

Aviation Accident Final Report - National Transportation Safety Board: https://app.ntsb.gov/pdf

Investigation Docket - National Transportation Safety Board: https://dms.ntsb.gov/pubdms

Aviation Accident Data Summary - National Transportation Safety Board: https://app.ntsb.gov/pdf

Civil Air Patrol: http://registry.faa.gov/N9420R

The National Transportation Safety Board did not travel to the scene of this accident.

Additional Participating Entities:
Federal Aviation Administration; Los Angeles, California

Textron Aviation; Wichita, Kansas

NTSB Identification: WPR15LA042
14 CFR Part 91: General Aviation
Accident occurred Saturday, November 15, 2014 in La Verne, CA
Probable Cause Approval Date: 03/06/2017
Aircraft: CESSNA U206G, registration: N9420R
Injuries: 3 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The private pilot reported that, during landing, he had difficulty controlling the airplane after the nosewheel settled onto the runway. The pilot stated that the airplane initially veered to the left; however, he was able to correct its track. The airplane then veered left a second time, he was unable to regain control, and the airplane subsequently exited the runway surface. During the accident sequence, the right wing struck the ground. 

Postaccident examination of the airplane revealed a deflated nosewheel oleo strut; however, the investigation was unable to determine whether the strut became deflated before or during the accident sequence. The airplane displayed proper nosewheel steering when weight was applied on the nosewheel strut. No further anomalies were noted with the airplane's nosewheel steering, nosewheel assembly, braking system, or tires; thus, the reason for the loss of control could not be determined.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
The pilot's loss of directional control during the landing roll for reasons that could not be determined, because postaccident examination of the nosewheel assembly revealed no anomalies that would have precluded normal operation.

On November 15, 2014, about 1420 Pacific standard time, a Cessna U206G, N9420R, veered off the runway during landing at Brackett Field Airport (POC), La Verne, California. The airplane was registered to and operated by the Civil Air Patrol under the provisions of Title 14 Code of Federal Regulations Part 91. The private pilot and two passengers were not injured. The airplane sustained substantial damage to the right wing during the accident sequence. Visual meteorological conditions prevailed and no flight plan had been filed. The instructional flight departed from San Gabriel Valley Airport, El Monte, California, about 1350.

During a telephone interview with the National Transportation Safety Board (NTSB) investigator-in- charge (IIC), the pilot stated that he had difficulties controlling the airplane after the nose wheel settled onto the runway, during the landing roll. The pilot further stated that the airplane initially veered to the left; however, he was able to initially counteract the deviation and the airplane was then positioned near the right side of the runway. Subsequently, the airplane veered left a second time, and he was unable to prevent it from exiting the runway surface, where the right wing struck the ground. 

The two passengers onboard the airplane stated that the landing was normal and shortly thereafter the pilot lost directional control of the airplane.

Postaccident examination of the airplane with a certified airframe and powerplant mechanic under the supervision of the NTSB IIC, revealed that the right wing was bent upwards about 3 feet from the wing tip. The airplane's braking continuity from the rudder pedals to the brakes was established with no anomalies. Examination of the nose tire, main tires, and braking assemblies revealed no anomalies. The nose gear assembly was examined and the nose oleo strut was observed to be deflated. However, with weight on the nose wheel, provided by lifting up on the airplane's tail, the nose wheel responded appropriately to pedal steering. The investigation was unable to determine if the deflated strut was due to impact damage or a malfunction. No additional mechanical malfunctions or failures were found that would have precluded normal operation.

The airplane's nose wheel steering system links the rudder pedals to the nose wheel. According to the airplane's Pilot's Operating Manual, "when a rudder pedal is depressed a spring-loaded bungee will turn the nose wheel ... approximately 15 degrees each side of center." By applying either left or right brake, the degree of turn can be increased up to 35 degrees each side of center. 

According to the aircraft manufacturer representative, "a steerable nose wheel, mounted in a fork, attached to an air/oil (oleo) shock strut, makes up the nose gear. Nose wheel steering is accomplished through the use of the rudder pedals. A hydraulic fluid-filled shimmy dampener is provided to minimize nose wheel shimmy. The nose wheel steering system links the rudder pedals to the nose wheel steering arm, affording steering control through the use of the rudder pedals and brakes. Torque links keep the lower strut aligned with the nose gear steering system, but permit shock strut action. A properly serviced nose gear oleo will fully extend, when the nose wheel is lifted off the ground. A centering stop log is located on the upper torque link. When the nose gear oleo fully extends, the centering stop lug interfaces with a cutout near the top of the oleo to prevent the nose gear from moving when the rudder pedals are actuated. When the nose gear oleo is compressed the centering stop lug is removed from the cutout allowing the nose tire to move in response to rudder pedal input."

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