N299AV

On March 12, 2024, at 0805 mountain daylight time, Raytheon Aircraft Company B200 King Air, N299AV, was substantially damaged when it was involved in an accident in Billings, Montana. The pilot-in-command and safety pilot were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 repositioning flight.

The pilot-in-command stated that he flew the airplane for 5.8 hours the day before the accident. On the morning of the accident, he planned for a short, 17-minute trip to pick up passengers at 0800 in Colstrip, Montana. The pilot recalled that he did not feel hurried and had plenty of time.

When asked numerous times to explain the start-up procedures, he stated that he started the left engine first and waited about 7-8 seconds for N1 to stabilize before he brought the condition lever up to high idle (about 52%). He recalled that he then positioned the three-setting switch down to change from “starter to generator.” He verified that both volt meters indicated loads below 50% and then started the right engine with a cross-generator start. After start, he verified that the battery indicated 23 volts. He could not provide specifics of the positions of the “Ignition and Engine Start” switches or the generator switches, but stated that it was a normal start. He did not perform an engine run-up, as it is not part of his procedures.

After departure from Billings, he received a "RA Fail" message followed by "PT Fail" amber light on the primary and multi-function displays and the electrical panels began to shut down. The pilot and safety pilot both recognized the airplane had a total loss of electrical power.

As the airplane was descending and heading back to the airport, the safety pilot was searching for an electrical failure checklist. They could not find such a checklist and the safety pilot started reading out the checklist for manually extending the landing gear. The air traffic control tower controller cleared the pilot to land by using a green light. The pilot opted to enter the airport traffic pattern on an extended base leg and land on runway 28R. He pulled the landing gear circuit breaker on the base leg and unstowed the emergency landing extension bar. After pumping it for about 30 pumps (he estimated about a minute), he turned the airplane from the base leg to final approach and felt pressure on the handle. Both pilots observed the landing gear extended from looking outside the windows but were unable to verify the landing gear were in the down and locked position because there was no electrical power to illuminate the landing gear lights.

With the flaps retracted, the airplane touched down on the runway 28R. The pilot stated that the main landing gear buckled, followed by the nose gear. The propellers contacted the runway as the belly slid across the surface, damaging both engines.

When asked if he reset the generators while in flight, the pilot could not remember. Additionally, when asked to describe the switch that he would use to perform a generator reset, he stated they were the silver switches (without a gang-bar) that are pressed down to reset the generators. He further stated that switches under the gang-bar were only used for starting the engines.

Investigators reviewed the Federal Aviation Administration (FAA) provided Automatic Dependent Surveillance-Broadcast (ADS-B) data for the accident flight (see Figure 1 below). The data disclosed that the airplane departed from runway 28R about 0742 and made a gradual, right-climbing turn to the east. The track ended about 0747.

Figure 1: Accident flight path

The mechanic who recovered the airplane from the runway stated that following the accident, he was able to illuminate the panel lights (normal brightness), “which was an indication that the hot bus was powered.” He disconnected the battery and the airplane was not touched until the investigation team performed the post-accident examination.

The battery and left and right generator switches were located under a gang-bar, which consisted of a thin piece of aluminum attached to a piano hinge that covered three red toggle-switches. A manufacturer’s representative stated that the purpose of the bar is to turn all three switches off at the same time by pressing down on the piece of metal (see Figure 2 below). According to the Pilot’s Operating Handbook, to turn on or reset the generators, the red switches must be held upward in the spring-loaded “RESET” position for a minimum of one second, then released to the “ON” position. Starter power to each individual starter/generator is provided from the main bus through a starter relay. The start cycle is controlled by a three-position switch for each engine. The starter/generator drives the compressor section of the engine through the accessory gearing. The starter circuit has priority over the generator circuit, so that the generator will not operate until the starter switch is turned off.

Post-accident examination of the airplane revealed that the master battery switch was in the “OFF” position while both generator switches were in the “ON” position. The starter switches were “OFF.”

Figure 2: Switches in the cockpit (showing battery, generators, and ignition)

The caution-advisory annunciator panel was documented without power applied. The L DC GEN light was removed and found to have a small white piece of debris in between the light housing and the metal rack. The debris was consistent in shape and color with that of a piece of thin wire casing with a single strand of wire embedded within it. Removal of the lights revealed that one had its filament broken and the other filament condition could not be determined. The housing was reinserted with the debris removed. The R DC GEN light was removed, and the lights were found to have the filaments broken.

The battery was then connected to the airplane and the battery switch was placed in the “on” Position. The annunciator panel test switch was activated revealing that the lights on the warning annunciator panel illuminated; the caution-advisory annunciation panel revealed that all the lights illuminated with the exception of the left and right generator lights (L DC GEN and R DC GEN). When the left light was reset, the light was dimly illuminated, consistent with one bulb not working (see Figure 3 below). Another light was removed and placed into the receptacle for the left and right generator lights. When the annunciator panel was tested again, the generator lights illuminated.

Figure 3: Cautionary-Advisory annunciation panel

The 28-volt Concord lead acid main battery was found disconnected from the power supply. Using a multimeter, the battery had a voltage reading of 24 volts. The battery was capacity tested by applying an electrical load of 42-amps, and the battery voltage dropped to 22.2 volts after 30 seconds; to 21.3 volts after 6 minutes; and it failed at 19.99 volts after 8 minutes 12 seconds. The mechanic testing the battery stated normal batteries would be between 23.8 to 24.2 volts after 30 seconds.

While the airplane was placed on jacks, investigators cycled the landing gear both manually and electrically and found the landing gear extension systems to function normally. To manually extend the landing gear, it took about 70-80 pumps on the emergency handle (about 1-1.5 minutes) before the landing gear extended to a locked position.