Murphy, ID, USA
N4393Z
PIPER PA 18-150
The flight of two airplanes landed at a dirt airstrip for a short break after flying in the area to spot elk. The passenger in the accident airplane recalled that during takeoff, the airplane's nose snapped to the right and then pointed toward the ground. The pilot in the other airplane (which had not yet departed) observed the accident airplane take off and reported that when it was about 150 ft above the ground, the right wing dropped and simultaneously he heard the accident pilot say "whoa" over the radio. The airplane's nose continued to drop, and the airplane impacted the ground in a nose-low, near-vertical attitude. Examination of the airplane revealed that the left aileron control cable was separated from the eye fitting and thimble on the left aileron control cable turnbuckle. Further, the outboard left aileron control cable and the inboard right aileron control cable were improperly crimped. The improper crimping allowed the left aileron cable to pull through the swaged sleeve. As a result, the separation of the cable would have allowed the balance cable to become slack and the pilot would not have been able to control the roll of the airplane. Examination of maintenance records revealed that 20 years before the accident, the left wing was rebuilt and reskinned and the flap and aileron hardware were replaced. The entry did not specifically mention that the control cables were replaced. Additionally, 10 years before the accident, the aileron balance cable and rudder cables were tightened. The airplane received an annual inspection every year, during which no discrepancies were noted with the flight control systems.
HISTORY OF FLIGHTOn November 3, 2017, about 0900 mountain daylight time, a Piper PA-18-150, N4393Z, was substantially damaged when it was involved in an accident near Murphy, Idaho. The pilot was fatally injured, and the passenger was seriously injured. The airplane was operated under the provision of Title 14 Code of Federal Regulations Part 91, as a personal flight. According to a witness, this was a flight of two, that originally departed from Boise, Idaho, about 0730 with the intent of flying over the accident pilot's property to spot for elk. The airplanes flew around the pilot's property for about 1.5 hours, when they had to land due to the passenger getting airsick. Both airplanes landed and were on the ground for about 20 minutes before departing on the accident flight. The witness reported that he watched the accident airplane takeoff, establish a positive rate of climb, and when the airplane was about 150 ft above the ground, he saw the right wing drop with the pilot simultaneously keying the mike and saying "whoa." The airplane's nose continued to drop, and the airplane impacted the ground in a nose-low near vertical attitude. The passenger stated that during the takeoff climb, the airplane's nose "snapped" to the right and was pointed to the ground. He thought that the pilot had added power to fly out of the situation as the engine noise had gotten louder. After the airplane struck the ground, he passed out for a short time. The passenger did not recall hearing the pilot say anything during the takeoff or during the crash sequence. AIRCRAFT INFORMATIONA review of the airplane logbooks revealed an entry dated on April 25, 1997, that indicated that the left wing was rebuilt, which included new spars and all the ribs. The wing was recovered with a polyfiber finish system and Ceconite 101 fabric. The left flap and aileron were replaced with new parts. A logbook entry dated August 3, 2007, indicated that the aileron balance cable and both rudder cables were tightened during the annual inspection. The airplane utilized a system of cables for aileron and flap control. The aileron control system consisted of a single cable assembly (part number 14300-8), which connects to the cockpit control to each aileron; there are two aileron control cables, one for the left and one for the right aileron. A two-segment balance cable connected the left aileron to the right aileron; the segments were connected by a link. Each control and balance cable attached to its respective aileron via a turnbuckle assembly that had two different end terminals. The aileron end of each turnbuckle was a clevis (or fork) terminal, and each cable end was an eye terminal. The eye end of each cable was fabricated and attached to the eye terminal by sliding a sleeve onto the cable, looping the cable around a thimble already installed in the eye terminal hole, inserting the cable end back through the sleeve, and then compressing the sleeve. Sleeve compression (also known as crimping or swaging) is critical to security of the attachment, and proper compression is verified using a manufacturer's go/no-go gauge, which is based on FAA specifications. When sufficiently compressed, the sleeve will fit into a dimension-controlled slot/notch in the gauge. The inboard ends of the two balance cables each terminated in a loop formed by the cable swaged around a thimble, and the cable ends were linked by bolts through these loops and two plates. AIRPORT INFORMATIONA review of the airplane logbooks revealed an entry dated on April 25, 1997, that indicated that the left wing was rebuilt, which included new spars and all the ribs. The wing was recovered with a polyfiber finish system and Ceconite 101 fabric. The left flap and aileron were replaced with new parts. A logbook entry dated August 3, 2007, indicated that the aileron balance cable and both rudder cables were tightened during the annual inspection. The airplane utilized a system of cables for aileron and flap control. The aileron control system consisted of a single cable assembly (part number 14300-8), which connects to the cockpit control to each aileron; there are two aileron control cables, one for the left and one for the right aileron. A two-segment balance cable connected the left aileron to the right aileron; the segments were connected by a link. Each control and balance cable attached to its respective aileron via a turnbuckle assembly that had two different end terminals. The aileron end of each turnbuckle was a clevis (or fork) terminal, and each cable end was an eye terminal. The eye end of each cable was fabricated and attached to the eye terminal by sliding a sleeve onto the cable, looping the cable around a thimble already installed in the eye terminal hole, inserting the cable end back through the sleeve, and then compressing the sleeve. Sleeve compression (also known as crimping or swaging) is critical to security of the attachment, and proper compression is verified using a manufacturer's go/no-go gauge, which is based on FAA specifications. When sufficiently compressed, the sleeve will fit into a dimension-controlled slot/notch in the gauge. The inboard ends of the two balance cables each terminated in a loop formed by the cable swaged around a thimble, and the cable ends were linked by bolts through these loops and two plates. WRECKAGE AND IMPACT INFORMATIONThe airplane came to rest inverted about 1,750 ft from the south end of the airstrip. Both wings remained attached to the fuselage. The wings had uniform leading to trailing edge crush damage. The tail and empennage sections remained connected and attached to the fuselage and sustained minor damage. The right aileron control system was intact and remained attached at its respective connections. No irregularities were noted with any of these components except the crimped sleeve at the inboard eye end; this crimp displayed an irregular pattern, and only two or three required crimps were properly dimensioned. The left aileron control cable was separated from its turnbuckle at the aileron. The left aileron control cable sleeve was not recovered on scene, and the cable displayed a light-colored area where the sleeve would have been. The associated thimble and turnbuckle remained attached to the eye-end of the left aileron turnbuckle. The turnbuckle remained intact with the clevis end properly bolted to the aileron control horn. The lockwire for the turnbuckle was in place and intact. The sleeve at the inboard end of the left aileron control cable had an irregular crimp pattern. The crimp widths were not uniform, overlapped, and were shallow. Guidance from the FAA Advisory Circular 43.13-1B titled Acceptable methods, Techniques, and Practices – Aircraft Inspection and Repair Table 7-6: Cooper Oval Sleeve Data under cable size identified the 1/8-inch cable required a 3 press sleeve to secure the thimble-eye hardware. The inboard right aileron control cable also had an irregular crimp pattern. When the appropriate go/no-go gage was used, the two irregular crimped sleeves did not fit into the designated slot (Oval M), which indicated that the crimp was not acceptable or in an airworthy condition. According to 43.13-1B, the cable system, at each annual or 100-hr inspection, must be inspected for broken wire strands. The cables should be removed periodically for a more in-depth inspection. Except for the left aileron control cable, flight control continuity was established from the tail section to the flight controls and out to both wings. All elements of the aileron balance cable were intact and remained attached at their respective connections. No irregularities were noted with any of the components. No other flight control separations were identified during the examination. The propeller assembly remained attached to the engine. The propeller spinner was crushed. Both propeller blades had S-bending and one blade had chordwise scratches across the full span of the propeller blade. Both propeller blades were bent aft with leading edge gouging and polishing. The engine was manually rotated via the propeller with valve train and mechanical continuity established. Thumb compression was obtained at all cylinders as well as movement of the valves and accessory gears. The magnetos remained attached to their respective mounting pads. Both magnetos were removed and with the use of a drive tool attached to the drive shaft. Spark was produced at each post for both the right and left magnetos. There were no observed preexisting conditions that would have precluded normal operation prior to impact. The carburetor had separated at the venturi. Fuel in the gascolator was blue in color. The carburetor fuel inlet screen had separated from the carburetor but was free of debris. The engine examination revealed no evidence of any mechanical failures or malfunctions that would have precluded normal operation. MEDICAL AND PATHOLOGICAL INFORMATIONThe Owyhee County coroner's office, Marsing, Idaho, performed an autopsy of the pilot. The cause of death was blunt force trauma. The Federal Aviation Administration Forensic Sciences Laboratory conducted toxicological testing on specimens from the pilot. The toxicological testing results were negative for tested drugs, carbon monoxide, and ethanol.
Failure of the left aileron control cable that resulted in a loss of aircraft control during takeoff. Contributing to the accident was inadequate maintenance inspections to the aileron cable connections.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
