History of Flight
On August 17, 2014, about 1105 central daylight time, a Cessna 172N, registration N734YW, sustained substantial damage when it hit trees and terrain after a partial loss of engine power during the initial climb from Natchitoches Regional Airport (IER), Natchitoches, Louisiana. The pilot received serious injuries, and the sport pilot rated passenger was fatally injured. The airplane was operated by Cane River Aviation, Inc. under 14 CFR Part 91 as a personal flight. Visual meteorological conditions prevailed, and the flight operated without a flight plan. The airplane departed IER about 1102 on a local flight.
The pilot reported a normal preflight and engine run-up. During takeoff, rotation occurred at about 70 knots, and the climb was normal. At about 300 feet above ground level, the engine suddenly lost power and shook violently. The pilot selected a soybean field about 135 degrees to his left for an emergency landing. The airplane overflew the 4,600-foot-long field and impacted a line of trees at the end.
Security cameras located about 0.4 miles east of the departure end of runway 17 recorded the accident. The airplane was seen climbing to 300–400 feet agl, then leveling off with black smoke trailing. It turned left while trailing smoke, then continued turning left to about 030 degrees heading. No black smoke was visible in later footage, but the airplane lost altitude for about 1 nm before impacting a tree line. No S-turns or side slips were observed. The accident site was about 0.65 nm from the approach end of runway 25 on a 290-degree bearing.
Personnel Information
The 80-year-old pilot held a private pilot certificate with a single-engine land rating and reported 1,991 total flight hours, with 1,632 hours in make and model. He held a third-class medical certificate issued April 16, 2013, with the limitation: Must wear corrective lenses.
The 82-year-old sport pilot rated passenger's last FAA medical exam was on September 20, 2005. At that time, he reported 60 total flight hours and 0 hours in the previous six months. His FAA medical certificate expired on September 30, 2007.
Aircraft Information
The airplane was a single-engine Cessna 172N, serial number 17269230, manufactured in 1977. It was equipped with a Lycoming 160-horsepower O-320-H2AD engine, serial number L-3942-76. The last annual maintenance inspection was conducted on December 13, 2013, with total airframe time 2,408.2 hours and engine time 940.2 hours since the last overhaul, which was performed on May 26, 1990—over 24 years before the accident. Lycoming recommends overhaul by the 12th year if hourly limits are not reached. The engine had accumulated 958.1 hours since overhaul.
Lycoming Mandatory Service Bulletin 412B, issued March 10, 1978, addressed security of intake and exhaust valve rocker arm retaining studs and valve train operation. The serial numbers in the bulletin did not include the accident engine's serial number. FAA Airworthiness Directive 77-20-07, issued August 31, 1978, addressed loose rocker arm retaining studs and hydraulic tappet failure; the accident engine's serial number was not listed. Lycoming Service Bulletin 240T, issued May 25, 2006, mandated replacement of rocker arms and fulcrums during overhaul for certain engine models.
Meteorological Information
At 1035, the surface weather observation at IER was: wind 250 degrees at 6 knots; visibility 10 miles; scattered clouds at 2,600 feet and 3,300 feet; temperature 31°C; dew point 24°C; altimeter 30.02 inches of mercury.
Wreckage and Impact Information
The airplane struck the top branches of a 50-foot willow tree and impacted terrain in a bean field. The initial impact point was about 150 feet from the tree on a heading of 320 degrees. The tree cut was consistent with a 45-degree left wing low attitude. The left wing's red navigation lens was found before the initial impact point. The main wreckage came to rest about 15 feet from the initial impact on a heading of 120 degrees.
The front section, including the instrument panel, partially separated forward of the wing strut attach points. The hour meter indicated 2,339.3 hours; the tachometer indicated 2,426.1 hours. The engine and propeller had minimal impact damage. The propeller remained attached and was bent slightly aft; both blades were straight with no leading edge damage or chordwise scratching. The spinner was crushed and deflected upward. The nose gear separated; main gear remained intact.
Both wings remained intact. The left wing leading edge had aft crushing along its entire span. The right wing had leading edge crush damage on its outboard section. Ailerons and flaps remained attached; flaps were in the up position. The flap handle, indicator, and actuator were also up. Left and right fuel tanks were intact with caps secure. The empennage was largely intact; vertical stabilizer and rudder had minimal damage. Left and right horizontal stabilizers exhibited aft crushing and leading edge damage. Flight control cable continuity was confirmed.
The left front seat was latched in the fourth hole from the front; its seat belt was unlatched, shoulder harness attached. The right front seat was separated from the seat tracks and outside the aircraft; its seat belt and shoulder harness were attached.
The engine was removed and examined. When the No. 1 cylinder rocker box cover was removed, the exhaust valve rotator cap was found loose. The exhaust valve rocker retaining stud was backed out of the cylinder head threads by about five threads (approx. 1/4 inch), and the rocker and pushrod were loose. Clearance between the rocker and valve stem prevented the exhaust valve from opening during engine rotation.
The engine was rotated by the propeller; crankshaft continuity to rear gears was confirmed. Valve train continuity was confirmed for all valves except the No. 1 cylinder exhaust valve. Compression and suction were observed from all cylinders. Borescope inspection of cylinder interiors showed no damage.
The No. 1 cylinder was removed; no damage to the piston or cylinder interior was noted. The exhaust valve rocker retaining stud was removed using finger pressure only. No damage to stud threads or corresponding cylinder head threads was found. Two shims were on the stud; the lower shim was undamaged, but the upper shim had an elongated hole and one side was bent upward and distorted. The fulcrum exhibited wear. The stud had no oversized markings. Numerous letters and numbers, including L and T, were stamped on the cylinder head in the milled channel between the rocker arm retaining studs. Fretting damage was noted on the cylinder head near the exhaust valve rocker attachment.
Medical and Pathological Information
No toxicological report was associated with the accident pilot.
Tests and Research
The exhaust valve rocker retaining stud was sent to the NTSB Materials Laboratory. Examination revealed an amber-colored, semi-soft solid deposit on the threads, consistent with carbohydrates such as starch or dextrin. No evidence of thread locker was found, and no thread damage was present aside from the deposit.