WPR17FA108 · Piper PA 30

According to the surviving passenger, he, the pilot, and pilot-rated passenger departed on a cross-country flight over water; the pilot shut down the right engine to demonstrate how to restart an engine during flight. The pilot was unable to restart the engine using the starter due to a lack of electrical power. He then made several attempts to air start the engine by gaining altitude and diving the airplane down to use airflow to assist in rotating the engine. After two unsuccessful attempts, the pilot decided to descend to a lower altitude, fly to a remote airstrip, and use the handheld battery booster located in the baggage compartment after landing to start the engine. As the airplane approached the airstrip, the pilot made a low-level pass to check the condition of the runway surface. A witness saw the airplane at treetop level. As it reached the end of the airstrip, it dropped in altitude, banked to the right, and impacted the shoreline in a right-wing down, nose-down attitude.

Instead of deciding to perform a low-level pass to an airstrip with one inoperable engine, the pilot should have handled the inoperative engine as a critical situation that necessitated landing the airplane immediately with minimal maneuvering. It is likely that, after the low-level pass, the pilot attempted to turn the airplane to maneuver for the runway and failed to adequately maintain sufficient airspeed or compensate for the asymmetrical thrust when he turned toward the inoperative engine which led to an aerodynamic stall and a loss of control.

The examination of the wreckage revealed that, according to the positions of the landing gear, flaps, and their controls, the airplane had insufficient electrical power during flight.

A friend who flew with the pilot on the day before the accident recalled that the pilot had installed a battery that had insufficient electrical power. The pilot then parked his motor vehicle near the airplane, plugged in the airplane's jumper cables, and successfully jumpstarted both engines from the vehicle's battery to continue that day's flight. It is likely that the battery was not replaced before the accident flight.

The postaccident examination also found that the left engine alternator belt was not attached to the alternator, and no belt was recovered within the confines of the engine cowling. The alternator drive pulley was damaged and had a residue, indicating that the belt had not been attached to the left engine alternator for some time. Thus, the left alternator was not operational.

The right engine alternator drive shaft rotated freely by hand, but the drive belt remained stationary with the crankshaft. The alternator drive belt was loose and excessively worn on the pulley contact area. The right engine inlet cowling section had rubber filings in the forward right interior surface. Rubber filings were also found on the back side of the starter ring gear and surrounding areas. The rubber filings were likely due to the loose fit of the belt on the pulley during engine operation. Given this evidence, the right engine alternator was probably intermittent with a loose belt.

The airframe maintenance logbook indicated that the last annual inspection was accomplished 2 years and 9 months before the accident. The engine maintenance logbooks were not located; thus, it could not be determined when maintenance personnel last inspected the engine. Due to a modification to the cowling, it did not permit a visual examination of the front side of the engine and the alternator belts during a preflight walk-around inspection unless the upper cowling was removed. It is likely that the pilot was not aware that the alternators were inoperative and that the airplane was operating on battery power when he shut down the right engine in flight.

Verbatim NTSB analysis and probable cause from the NTSB dataset