History of Flight
On November 12, 2016, about 1640 mountain standard time, a Piper PA-28-235 airplane, registration N9398W, struck a berm during a forced landing following a loss of engine power near Taylor, Arizona. The privately owned airplane was operated by the pilot under 14 CFR Part 91 as an instructional flight. Visual meteorological conditions prevailed, and no flight plan was filed. The local flight originated from Taylor about 1600.
The flight instructor reported an uneventful preflight. The wing tip fuel tanks were both half full, and the main left and right wing tanks contained 18 and 20 gallons of fuel, respectively. About 40 minutes after takeoff, after completing a series of training maneuvers, the instructor decided to demonstrate an emergency descent. He asked the student to look for an appropriate simulated landing spot and pitched the nose slightly down, configuring for best glide descent speed at about 8,000 ft (1,700 ft agl). After descending about 500 ft, the instructor sensed something wrong; he lifted his headset and heard a quiet engine. He pushed the throttle forward, but the manifold pressure gauge remained static and the engine did not respond. He turned on the electric fuel pump, switched the fuel selector from left to right tank, and set the mixture to full rich, with no change. He then moved the throttle back and forth several times with no response. With insufficient altitude for further troubleshooting, he began looking for an emergency landing site.
On final approach, he secured the airplane by shutting off the fuel selector valve. As they got closer to the ground, he saw a berm and fence obstructing the landing area. Unable to deviate, the airplane struck the berm during the ground roll, bounced back into the air, and landed hard. The airplane sustained substantial damage to the aft fuselage and right side of the stabilator.
Aircraft Information
The last maintenance event was an annual inspection on September 17, 2015, 7.1 flight hours before the accident. The airplane was powered by a normally aspirated O-540-B4B5 engine, originally manufactured by Lycoming and overhauled in 2002 with components from Superior Air Parts, after which it was branded as a "Millennium Engine." At the time of the accident, the engine had accrued 1,135.6 flight hours since overhaul.
Additional Information
The temperature and dew point values in the area at the time of the accident were not conducive to the formation of carburetor ice.
Tests and Research
The airplane was equipped with a JP Instruments EDM-700 series engine monitor, configured to record exhaust gas temperature (EGT), cylinder head temperature (CHT), and oil temperature. The recorded data spanned 34 minutes. Initially, the data showed variations and rises in EGT and CHT consistent with taxi and takeoff. The values then averaged about 1,275°F and 325°F, respectively, until 29 minutes into the recording, when both began to drop simultaneously. By the end of the recording, average CHT had reached about 225°F. During that period, EGT dropped to 1,000°F, then intermittently increased to about 1,225°F for about 20 seconds, after which it dropped to the last recorded temperature of 200°F. Oil temperature remained at about 200°F throughout the flight.
Post-accident examination by the NTSB investigator-in-charge revealed: the belly-mounted fuel selector/strainer was full of fuel; no water was detected. The fuel selector moved freely through all positions with well-defined detents. A peripheral examination of the engine and fuel supply system found no anomalies. The engine sustained minimal damage, with the propeller blades bent aft about midspan. All engine controls were continuous from their control arms to the cabin and moved smoothly through their full range. The inlet air filter and induction lines were free of obstruction despite impact damage; the oil sump contained about 9 quarts of oil. The top spark plugs (massive-electrode, Tempest) had electrodes mechanically intact, coated in black soot, and showed normal wear signatures per the Champion Spark Plugs AV-27 chart. The crankshaft turned freely by hand with thumb compression on all cylinders.
The propeller was replaced with an undamaged unit, and an engine test run was performed using fuel recovered from the accident airplane. The engine started on the fourth cranking attempt and maintained a smooth idle at about 750 rpm. As it warmed, fuel and oil pressures stayed within green arcs. A magneto check showed a 75 rpm drop on each side; a propeller check showed appropriate rpm drop. The engine was operated throughout its full speed range for 10 additional minutes, including multiple throttle chops and rapid accelerations simulating the accident scenario; it responded appropriately with no hesitation or speed fluctuations. After shutdown, top spark plugs exhibited grey coloration. The carburetor and engine-driven fuel pump were examined, with no anomalies noted.
Probable Cause
Not stated in the source.