Saturday, April 15, 2017

Luscombe 8A, N25100: Accident occurred October 24, 2015 at Ernest A. Love Field Airport (KPRC), Prescott, Yavapai County, Arizona

Aviation Accident Final Report - National Transportation Safety Board:

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

Additional Participating Entity:
Federal Aviation Administration / Flight Standards District Office; Scottsdale, Arizona 

Docket And Docket Items - National Transportation Safety Board:

Aviation Accident Factual Report -  National Transportation Safety Board:

NTSB Identification: WPR16LA017
14 CFR Part 91: General Aviation
Accident occurred Saturday, October 24, 2015 in Prescott, AZ
Probable Cause Approval Date: 05/23/2017
Aircraft: LUSCOMBE 8A, registration: N25100
Injuries: 2 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 commercial pilot of the tailwheel-equipped airplane stated that, upon touching down in a three-point attitude, the airplane veered left. The pilot attempted to correct with rudder, but the airplane continued left and ground looped. Examination revealed that the tailwheel had rotated 180°, leaving its control chains crossed over one another. Under this condition, the tailwheel direction of movement would be opposite that commanded by the pilot. Further examination revealed that the tailwheel steering arms were bent upward, allowing the wheel to rotate past its travel stops and into the reversed condition. It is likely that, as the pilot initially lost control and the airplane began to ground loop, the wheel passed beyond its travel limits, causing the controls to become reversed, which made recovery unlikely.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
The pilot's failure to maintain directional control during landing, and his inability to recover due to a malfunction of the tailwheel.

On October 24, 2015, about 1510 mountain standard time, a Luscombe 8A, N25100, experienced a loss of directional control during the landing roll, and ground looped at the Ernest A. Love Field Airport, Prescott, Arizona. The pilot, who owned the airplane, was operating the airplane under the provisions of 14 Code of Federal Regulations Part 91. The certified flight instructor and his passenger were not injured; the airplane sustained substantial damage. The personal cross-country flight departed from Gallup Municipal Airport, Gallup, New Mexico, about 1245 with a planned destination of Prescott. Visual meteorological conditions prevailed and a company flight plan had been filed.

In a written report, the pilot stated that as he entered the vicinity of the destination airport, he maneuvered the airplane for a straight-in approach to runway 21L. The approach was slightly higher than his normal glide slope, and the pilot configured the airplane into a left slip in an effort to lose altitude. After becoming established, he maintained a left crab angle to compensate for an approximate 7 kt left crosswind. He configured the airplane for a three-point landing and touched down on the centerline. The airplane continued the landing roll until decelerating to about 15 mph at which point it began to veer to the left. The pilot input full rudder control to try to counteract the veer, but despite his attempts, the airplane ground looped.

During the accident sequence, the airplane incurred substantial damage to the wing. The pilot opined that the loss of control was precipitated by a tail wheel malfunction. According to Federal Aviation Administration (FAA) records, the pilot purchased the airplane on the day of the accident; he reported having amassed about 200 hours of flight time in the same make and model.

The Luscombe 8A was equipped with a Scott 3-24B tailwheel (now Scott 2000), with a steerable six-inch rubber tire with full-swivel capability. The rudder control horns were connected via chains to the assembly, which uses spring pressure to hold a set of steering arms into machined flats on the wheel fork. As the wheel pivots to its travel limit, it comes into contact with a stop on the fork bracket, which releases the assembly, allowing the wheel to castor freely. According to the Scott 3-24B Handbook, "The tail wheel assemblies provide directional control throughout full rudder travel of the aircraft while the tailwheel is in contact with the ground. The assemblies will automatically full-swivel only well after the maximum point of air rudder control is reached in either direction…The tailwheel steering and release mechanism is so designed that 65-degrees of tailwheel turn (or travel) is provided either right or left from neutral steering position before the mechanism begins to release."

The airplane came to rest on the edge of the runway with the right landing gear collapsed and folded under the fuselage. The tailwheel steering chains remained affixed to their respective rudder horns as well as their respective steering arms mounted on the tailwheel body. However, the tailwheel had rotated over 180-degrees and was canted to the left leaving the chains crossed over one another. Additionally, the steering arms appeared bent upwards. A complete report with accompanying photographs are attached to the public docket for this accident.

An FAA certified airframe and powerplant mechanic examined the tailwheel. He stated the examination revealed that the tailwheel was turned around 180-degrees from its normal configuration. The right steering arm was bent upwards, and he observed that it was able to clear over the stop, allowing the steering head to continue to the reversed position, rather than unlock to caster freely. Under this condition, the tailwheel direction of movement would be opposite that commanded by the pilot, rather than free-castering as designed. He additionally noted that the leaf spring assembly was loose, allowing a possible shudder to develop. Following the examination, he repaired the assembly, and the steering arms were reconfigured to their correct straight position, enabling them to contact the stops and release the wheel to freely caster with the steering chains remaining on their respective side.

1 comment:

Dan Lawler said...

I was the pilot. I disagree with the NTSB conclusion: "It is likely that, as the pilot initially lost control and the airplane began to ground loop..."

The pilot did not initially lose control. No loss of control was experienced prior to the issue of the tailwheel steering in the reversed direction.