CEN12LA204

The pilot said he was on a cross-country flight and he noticed that the alternators were producing about 9 volts. He tried to troubleshoot the problem, and he switched the alternators off and on a “number” of times, but he was unable to get them to indicate more than 8 to 9 volts (the pilot used the term "alternator" and "generator" interchangeably in his statement). He said that he heard a “squeal” coming through the headset, and when the right alternator was switched off, the noise would stop. He said that he eventually lost radio communication capability while en route to his destination, and he diverted to an alternate airport. The pilot lowered the landing gear on the downwind leg, and he observed that the nose landing gear was extended by its reflection in the spinner. The landing roll was “normal” until the right main landing gear collapsed, and then the left main landing gear collapsed. A postaccident examination of the landing gear did not disclose any evidence of a mechanical malfunction. The pilot reported that he lost all electrical power due to a loss of one or both alternators. It is likely that the right alternator failed, so when the pilot turned off the right failed alternator, the noise stopped; however, the left alternator could not put out enough voltage to power the radios and other electrical demands. By the time the gear was lowered, there was not enough power to lock the left and right main landing gears in place, so they both collapsed during the landing roll. Had the pilot realized that he had lost electrical power and followed the emergency checklist, he could have verified the locked status of the landing gear and followed the emergency landing gear procedures to extend the gear.

On March 2, 2012, about 1420 central standard time, a Piper PA-30, N373JT, had its main landing gear collapse during landing on runway 36 at the Northwest Regional Airport (52F), near Roanoke, Texas. The private pilot, who was the sole occupant, reported no injuries. The airplane sustained substantial spar damage. The airplane was registered to and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Day visual flight rules (VFR) conditions prevailed for the flight, which did not operate on a VFR flight plan. The flight originated from the Crystal City Municipal Airport, near Crystal City, Texas, about 1300, and was destined for the Denton Municipal Airport (DTO), near Denton, Texas, when it diverted to 52F with electrical system issues. According to a pilot statement, during the flight the alternators were producing approximately nine volts of output. He switched the generators off and on a “number” of times and was unable to get them to get them to indicate more than eight to nine volts. The pilot had intermittent global positioning system operation, heard a “squeal” in his radio. He observed that when the right alternator was switched off, the noise would stop. The pilot eventually lost radio communication capability while en-route to DTO. He diverted to 52F and lowered the landing gear on downwind. The pilot observed that the nose landing gear was extended by its reflection in the spinner. The landing roll out was “normal” until the right main landing gear collapsed. The left main landing gear then collapsed. The pilot’s comments, in part, stated: It is obvious that at least one alternator failed, probably the right one, and the other alternator could not put out enough voltage to carry the radios, GPS, autopilot, lights and other electrical demands and by the time that gear was lowered there was not enough power in the battery to lock the gear in place and/or the gear failed to lock in place. The PA-30 flight manual contained an emergency procedure referencing emergency landing gear extension. As part of the procedure, the pilot is instructed to slow the airplane to an airspeed “not to exceed 100 mph.” The full travel of the extension handle or a green light on the instrument panel indicate the landing gear is extended. An operational note indicated that “reducing power and rocking gear extension handle will aid in manually extending the landing gear.” According to a Federal Aviation Administration inspector, there was no evidence of mechanical malfunctions or failures that would have precluded normal landing gear operation.