N482TJ

On July 23, 2023, about 1420 eastern daylight time, a Bell 206-L4 helicopter, N482TJ, sustained substantial damage during an accident near Caldwell, Ohio. The commercial pilot sustained serious injuries. The helicopter was operated by Sky Aviation Corporation under the provisions of Title 14 Code of Federal Regulations Part 133.

The helicopter had been housed at Cambridge Municipal Airport, Cambridge, Ohio. A ground crewmember stated that he and the accident pilot arrived at the airport about 0710 on the day of the accident. The pilot conducted a preflight examination, and the ground crewmember took fuel samples from the helicopter fuel tank and the trailer-based fuel tank that would be used to refuel the helicopter that day. The ground crewmember reported that all the samples he took were “clean, clear, and bright.”

The helicopter and trailer were positioned at an off-airport landing zone, referred to as LZ2, so that the pilot could conduct external load cargo drop operations from that location and the ground crew could assist the pilot from the trailer. The pilot reported that the external load operations, which were occurring on a “catch up” day resulting from helicopter maintenance-related delays, began between 0800 and 0900. According to the operator, the pilot completed eight cargo drops during the morning operations and refueled the helicopter (via “hot fueling”) as needed from the trailer-based fuel tank. The ground crew observed nothing unusual during those flights.

About 1215, the pilot returned to LZ2 and shut down the helicopter. Afterward, a ground crewmember refueled the helicopter with 335 pounds of fuel and spoke with the pilot about how the helicopter had been operating; the crewmember reported that, according to the pilot, “there were no issues” with the helicopter. Also, the pilot reported that, while the helicopter was shut down, he checked all fluid levels, and “everything seemed normal.” The pilot noted that, even though the helicopter had a known oil leak, the oil level at the time was not low.

The helicopter departed from LZ2 about 1330. According to a cargo loading document that the operator provided, the purpose of the afternoon flights was to make eight additional external load drops. The eight bags to be dropped were attached to the eight release hooks on the helicopter’s external load carrier. The eight bags weighed a total of 1,070 pounds. The cargo was released via a button on the cyclic control stick. When actuated, the cargo hook opened and released the respective bag. The helicopter was also equipped with an emergency cargo release that, when pressed, would release the long line and the external load carrier; it was found in the closed position. The maximum cargo hook capacity was 2,000 pounds.

Flight track data indicated that the pilot maneuvered the helicopter southeast of LZ2 for about 45 minutes. The pilot completed one cargo load drop involving a bag that weighed 130 pounds, resulting in a helicopter external load weight of 940 pounds after the drop. The pilot then maneuvered toward the next drop zone. The flight track showed that the helicopter circled over the area of the accident site before descending through trees in a near-vertical (straight-down) path and impacting terrain. Figure 1 shows the helicopter’s path over the drop zones and the locations of LZ2 and the accident site.

Figure 1. Flight track (red line), drop zones (green dots), and location of main wreckage at accident site. Note: The drop zones from the morning flights are number 1 through 8. The drop zones for the afternoon flights are labeled on the right side of the figure.

The pilot did not remember whether he dropped the second bag (which also weighed 130 pounds). The pilot also did not remember the helicopter’s descent and impact with terrain, and he did not recall any unusual helicopter sounds or annunciations during the flight or issues related to the weather. The ground crew did not witness the accident.

The cockpit was substantially damaged by impact forces. The tailboom separated just aft of the intercoastal support and was located a few feet away from the fuselage. Both horizontal stabilizers remained attached to the tailboom.

The cyclic and collective on the pilot (right) side had fractured at the base, but each showed corresponding movement to the right and center servo actuators, respectively. Control tube continuity was observed to all three servo actuators. The left side anti-torque pedals were recovered, and directional control continuity was observed from the tailboom to the cockpit. Continuity was also established from the control tube in the tailboom to the tail rotor blades. No preimpact anomalies were observed with the main rotor drive and tail rotor drive systems.

The long line used for external load operations was found partially wrapped around the main rotor mast, as shown in figure 2, and partially tangled in trees surrounding the main wreckage. The cargo hook (attached to the underside of the fuselage) was found closed with the long-line hook attached. The emergency hook release was also found closed. The cargo hook was tested, and when actuated the hook opened and the long line separated from the helicopter. The long line was measured and found to be 122 ft in length. The line exhibited tearing and abrasions about 14 ft below the point where it was connected with the cargo hook, consistent with where it had been wrapped around the main rotor mast. The eight cargo hooks on the external load carrier were found closed, and the cargo load to be dropped at the second drop zone was located about 20 to 30 ft from the main wreckage.

Figure 2. Long line wrapped around the helicopter main rotor driveshaft at the accident site. (Source: FAA)

The engine was found in its installed position. The engine was mostly undamaged, with only the left front mount leg bent, the left rear mount leg broken, and the left discharge tube dented. All engine external lines were secure. A pneumatic leak check detected no leaks. The engine N1 (gas producer) system turned freely and was continuous from the impeller to the starter generator and first-stage turbine wheel. The engine N2 (power turbine) system rotated and was connected to the powertrain. The compressor was removed and disassembled. Rub marks were observed between the impeller and impeller shroud, which was consistent with engine operation during the accident sequence. The engine oil filter was clean, and the oil was normal in appearance and smell.

Both main rotor blades exhibited significant fragmentation. The main rotor hub remained attached to the rotor mast and the root ends of the main rotor blades remained attached to the hub with fractures immediately outboard of the main rotor grip plates. Both blades also exhibited multiple indications of leading-edge impact-related damage, and the trailing edge on both blades was split open along the entire length of the blades. The inboard and outboard trim tabs for both main rotor blades were located at the accident site, but portions of each blade tip were not located.

Both tail rotor blades remained in their installed position and exhibited no significant deformation or fragmentation. The oil in the tail rotor gearbox was normal in appearance and smell. Overall, no mechanical anomalies of the helicopter were found that would have precluded normal operation.

The NTSB conducted an aircraft performance study to reconstruct the helicopter’s flight path and ground track, and determine, if possible, the events/factors that initiated the helicopter’s vertical descent and terrain impact. The estimated helicopter weight at the time of the accident was about 4,126 lbs. The performance data published in the helicopter’s Rotorcraft Flight Manual indicated that the accident helicopter had adequate hover out-of-ground-effect performance available for the load configuration and environmental conditions, assuming a skid height of 40 feet and gross weight of 4,550 lbs or less.