CEN25LA401 · CubCrafters CCK-2000 EX

Shortly into the local area flight with the experimental amateur-built airplane, the pilot noticed a flicker on the avionics display, but a low voltage warning never appeared. The pilot then looked at the engine monitoring display which indicated the alternator was not charging, and it showed 12.8 volts direct current (VDC) on the main battery. The pilot immediately started a climbing turn back to the departure airport. After reaching about 4,000 ft, he tried several methods to get the alternator working including cycling both the field and the main alternator circuit breakers several times. He checked the voltage for the ignition backup battery, which read 12.8 VDC. Since he had about a 15-minute flight back to the departure airport, he decided to save the ignition backup battery and run off the main battery until he received a low voltage warning. The airplane was on final approach when a low voltage warning appeared on the display. The pilot switched over to the ignition backup battery and watched as the voltage dropped from 12.8 VDC down to 0 VDC, and the engine sustained a total loss of engine power. The pilot reported that the ignition backup battery only lasted about one or two minutes before the voltage dropped to 0 VDC. While on short final, about 300 ft agl, the pilot performed a forced landing near trees and a grass field. The airplane came to rest nose down in the trees and sustained substantial damage to both wings and the wing struts. Postaccident engine examination revealed a fractured ring terminal for the 12-volt alternator. It is likely that the ring terminal fractured from vibrations while the engine was operating. It is also likely that there was too much tension and not enough relief on the wire that the ring terminal was connected during the installation to the alternator. The airplane’s engine was built to use a dual electronic ignition system that operated from the airplane’s electrical system, which included the main battery, the alternator to maintain the main battery’s charge, and the ignition backup battery. Once the ring terminal fractured, the ignition system relied completely on the main battery as the source of ignition power. Once the main battery power was depleted and the ignition backup battery power was depleted, the ignition system could not operate, and the engine sustained a total loss of power due to the lack of ignition. The airplane did not accumulate enough time to require its first annual inspection for the airframe and the engine. According to the airplane maintenance manual, the ignition backup battery is to be changed at each annual inspection. The pilot expressed concern that with the ignition backup battery that came with the kit, as it may take a builder some time to complete the building of the airplane, and that could easily go over a one-year timeline for example. The pilot would not have been able to detect the fractured ring terminal without removing the engine cowl, which is not normally part of the pilot’s preflight inspection.

Verbatim NTSB analysis and probable cause from the NTSB dataset