Accident Briefs: December 2019
NTSB reports on recent aviation accidents.
Note: The reports republished here are from the NTSB and are printed verbatim and in their complete form.
Cessna 172
Rhome, Texas/Injuries: 1 Fatal, 3 Serious
The commercial pilot was taking family members for rides in his airplane; the accident flight was the third flight of the evening. After the second flight, the pilot landed and taxied the airplane back to his property, where three family members boarded the airplane while the engine continued to run. The pilot taxied back to the runway and departed. A pilot-rated witness stated that the takeoff roll was longer than expected, and, once airborne, the airplane pitched "very high" nose-up to about 50 ft above ground level (agl), then the nose came back down. The airplane appeared to accelerate down the runway until it climbed to about 300 ft agl, then made a left turn and descended out of view. The airplane impacted several trees and continued into a field, where it came to rest inverted. Damage to the propeller was consistent with a lack of engine power at the time of impact.
Examination of the airplane revealed evidence of a longstanding pattern of inadequate maintenance, including a rodent's nest in the leading edge of the left wing, a large mud dauber nest on the oil cooler, and cobwebs in the engine compartment. An automotive hydraulic hose was used in place of the main fuel line from the gascolator to the carburetor. The gascolator fuel strainer contained 3 large pieces of organic debris similar to insect cocoons, which were the same size as the hydraulic hose and associated fuel fitting. It is likely that the fuel line was removed for an extended period of time and eventually replaced with the automotive hydraulic hose, during which time the fuel system was exposed, which allowed insects to nest inside; because there were no maintenance records associated with the airplane, it could not be determined when the hose was replaced. During the accident flight, it is likely that the organic material became dislodged and restricted fuel to the carburetor, which subsequently starved the engine of available fuel and resulted in a total loss of engine power.
The autopsy of the pilot revealed evidence of hypertension and coronary artery disease; however, it is unlikely that these conditions contributed to the accident. Toxicological testing indicated that the pilot had been using alcohol before the accident and had levels considered impairing; it is likely that alcohol impaired the pilot's decision making and his ability to operate the airplane. Toxicological testing also revealed evidence that the pilot had used marijuana before the accident; however, it could not be determined if the concentrations would have been impairing or would have affected his performance.
Probable cause(s): The pilot's inadequate maintenance of the airplane, which resulted in a total loss of engine power due to fuel starvation when organic debris restricted available fuel to the carburetor, and the pilot's impairment due to the ingestion of alcohol, which affected his ability to safely operate the airplane following the loss of engine power.
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RV-10
Sun Lakes, Arizona/Injuries: 1 None
The private pilot reported that, during the en route climb, he smelled antifreeze and realized that the engine was overheating. He then reduced power to idle and turned the airplane back toward the departure airport. As the airplane descended, the pilot added power, but the engine did not respond. He decided to land at a nearby closed airport; however, when he realized that the airplane would be unable to reach it, he performed a forced landing to a desert. During the landing roll, the airplane struck several bushes, which resulted in the nosewheel and left main landing gear collapsing and the left wing and fuselage sustaining substantial damage.
The airplane was powered by a modified automobile engine, which was equipped with two alternators and a water pump to circulate the engine coolant. The common drive belt that connected the two alternators and water pump was found detached. In addition, the upper and lower attachment bolts that secured one of the alternators were fractured, and the alternator was partially displaced. Examination of the fracture surfaces of both bolts revealed that they exhibited rachet marks, consistent with fatigue fractures. It is likely that, once the alternator attachment bolts fractured, the common drive belt tension decreased, which resulted in the separation of the belt. The belt separation would have precluded the water pump from operating and led to the engine overheating and eventually losing total power.
Probable cause(s): The fatigue fractures of the upper and lower alternator attachment bolts, which decreased the common drive belt tension and resulted in the subsequent in-flight separation of an alternator drive belt, the overheating of the engine, and the subsequent total loss of engine power.
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LOCKHEED P2V 5F
Pocatello, Idaho/Injuries: 3 None
The company dispatched the accident airplane to a fire as part of an exclusive contract with the United States Forest Service and under the direction of the Bureau of Land Management. During the airplane's climb, the airline transport pilot, who was acting as pilot-in-command, adjusted the trim to reduce nose-down pressure and subsequently observed an uncommanded aft movement of the control yoke and simultaneous increase in the airplane's pitch attitude. The flight crew attempted to regain pitch control by adjusting the trim wheels, but the airplane continued to maintain a pitch-up attitude. Using coordinated inputs, the flight crew was able to land the airplane without incident.
A postlanding examination revealed that the variable camber, or varicam, was damaged during the event. This secondary control surface is directly connected to the elevators and provides a primary structural load path for all elevator loads; thus, any damage to the varicam was considered substantial.
Postaccident examination revealed that maintenance personnel had failed to secure the drive stop coupling bolts with lockwire and that one of the bolts had backed out of its bolt hole. Because the varicam likely did not display any deformation before takeoff, as it would have been inspected after the previous flight, the bolt likely backed out sometime during the takeoff. When the flight crew adjusted the varicam trim during the initial climb, the absence of this bolt prevented a section of the drive shaft from rotating, allowing only a portion of the varicam to move. This resulted in the deformation of the left side varicam and subsequent upward deflection of the left elevator, which is hinged to the varicam. The resulting feedback in the cockpit was an uncommanded aft movement of the control yoke, which placed the airplane in a pitch-up attitude that could not be corrected by flight control inputs from the cockpit.
The mechanic responsible for installing the lockwire was under stress due to family issues at the time of the varicam was last serviced. The company's task cards indicated that the mechanic failed to lockwire the drive stop coupling bolts to the drive stop, despite noting that the work had been completed by stamping the card with his designation. This omission should have been detected by either the facility's lead mechanic or the quality assurance (QA) inspector through the required inspection item (RII) process. However, the lead mechanic seldom oversaw inspections and most likely did not attempt to review this mechanic's work and others' work, as the investigation revealed 7 additional RII oversights. Further, the QA inspector, whose main duty was to review any work that had been stamped RII by the lead mechanic, failed to notice that the critical flight control areas had not been annotated as RIIs. Although the company retrains its RII staff biennially, the QA inspector did not appear to understand his role in the RII process, as he was reported to have given approvals without verifying if the work qualified as an RII. While the mechanic failed to secure the drive stop Page 2 of 3 WPR17LA180 coupling with lockwire, the lead mechanic and the QA inspector's lack of oversight contributed to the omission that ultimately resulted in the varicam failure.
Probable cause(s): Maintenance personnel's failure to secure hardware, which resulted in an uncommanded upward deflection of the left elevator and aft movement of the control yoke and inhibited the flight crew from adjusting the airplane's pitch attitude in flight. Contributing to the accident was the lack of maintenance oversight, which should have identified the unsecured hardware before flight.
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RV6A
Santa Paula, California/Injuries: 2 Fatal
The private pilot and pilot-rated passenger were conducting a daytime visual flight rules crosscountry personal flight and neared their intended destination airport. Witnesses observed the airplane on the left downwind leg of the airport traffic pattern with no airplanes ahead of it. As the airplane neared an area where a turn from downwind to base would normally be performed, the pilot initiated a steep left turn; it then entered a spin and descended into the ground. Shortly after impact, a postcrash fire ensued, which destroyed the airplane. An examination of the airframe, engine, and related systems revealed no evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation.
Investigators were unable to determine how much fuel was on board the airplane at the time of the accident. Regardless of the fuel quantity, weight and balance calculations at various fuel loads placed the center of gravity within the manufacturer's limits. It is likely that, while maneuvering in the airport traffic pattern, the pilot exceeded the airplane's critical angle of attack, which resulted in an aerodynamic stall at an altitude too low to recover.
Although the investigation could not determine who was manipulating the controls at the time of the accident, and given the pilot rated passenger's lack of recent flight experience, it is likely that the owner of the airplane was manipulating the controls at the time of the accident and was ultimately responsible for maintaining flight control of the airplane.
Probable cause(s): The pilot's exceedance of the airplane's critical angle of attack while maneuvering in the airport traffic pattern, which resulted in an aerodynamic stall and subsequent spin.
Note: The reports republished here are from the NTSB and are printed verbatim and in their complete form.

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