N521HB

HISTORY OF FLIGHTOn February 19, 2022, about 1834 Pacific standard time, a McDonnell Douglas Helicopter 500N (520N), N521HB, was substantially damaged when it was involved in an accident in Newport Beach, California. The pilot sustained minor injuries and the TFO was fatally injured. The helicopter was operated as a public aircraft flight by the Huntington Beach Police Department (HBPD).

The helicopter departed its home base, Huntington Beach Police Department Heliport (CL65), at 1800, and for the next 30 minutes flew a routine patrol along the coast of Huntington Beach, inland to Costa Mesa, and then south to Newport Beach.

The pilot reported that as they were about to depart the Newport Beach area, they received a transmission over the primary police radio channel that there was a fight taking place just south of their location. The pilot stated that he redirected the helicopter toward the area and began a right orbit between 500-600 ft above ground level (agl) while the TFO (who was seated in the right seat) turned on the infrared camera and began searching the ground. The TFO spotted a group fighting, and the pilot began to maneuver the helicopter in a tighter orbit while the TFO relayed his observations over the police radio channel.

Ground patrol officers arrived on the scene, and the pilot continued the orbits about 500 ft above ground level, while simultaneously viewing the activity through his monitor, and maneuvering the helicopter so the TFO could continue to observe the altercation. The pilot stated that he watched as ground patrol officers got out of their car and approached the group, who by this time had mostly dispersed. He was concerned that one person was about to start fighting with an officer, and he slowed the helicopter to about 50 knots (kts) indicated airspeed to keep the camera aimed at the scene longer, so that they would not lose sight of it behind a building.

The pilot stated that, suddenly, the helicopter yawed aggressively to the right, and he immediately applied full left foot pedal and forward cyclic to arrest the rotation, but there was no response. He then applied right pedal to see if the pedals had malfunctioned, and observing no change, he reverted to full left pedal. He continued to apply corrective control inputs, but the helicopter did not respond and began to progress into a spinning descent. (see Figure 1.) The TFO transmitted over the police radio channel, “We’re having some mechanical issues right now”, followed by, “we’re going down, we’re going down”.

Figure 1 – Final flight path segment

The pilot stated that the rotation became more aggressive, and he began to modulate the throttle, collective, and cyclic controls to try to arrest the rotation rate. He stated that his efforts appeared to be partially effective, as the helicopter appeared to respond; however, because it was dark, he had no horizon or accurate external visual reference as the ground approached. The engine continued to operate, and he chose not to perform an autorotation because the area was heavily populated. He then had a sense that impact was imminent, so he pulled the collective control in an effort to bleed off airspeed.

The helicopter hit the water hard on the TFO’s side in a downward right rotation. The pilot recalled a sudden smash and saw water and glass coming toward him as the canopy shattered. He felt the rotor blades hitting the water, everything then stopped, and within a few seconds he was submerged.

The spinning sequence was captured by security cameras and multiple witness cell phone cameras. Review of the footage indicated that the sound of the helicopter’s engine and rotor system was present until water impact, and the helicopter was not emitting any smoke. As the helicopter descended, its pitch attitude violently oscillated between about 30° nose down and almost full nose down as the gyrations progressed.

None of the cameras captured the transition from the orbit maneuver to the spin, but one security camera captured the helicopter on its final orbit. The helicopter moved behind a building and out of view and was already spinning when it came back into view. The sound of the engine and rotor system could be heard throughout, with no sounds indicative of a mechanical failure. PERSONNEL INFORMATIONThe pilot was hired by HBPD in 2005. His initial duties included that as a TFO, and over the next few years he began flight training, eventually attaining a commercial pilot certificate. At the time of the accident, he was the second most experienced pilot at HPBD, with about 3,700 flight hours of flight experience as pilot-in-command of the MD500N. He typically flew between 12 to 20 hours per month, with half of his flights performed at night.

The day of the accident was the pilot’s first day of a three-day shift; he had spent the preceding days off in Spokane, Washington. He started his day by waking up at 0400, having gone to bed about 2100 the night before. He then flew down to Long Beach, California, via connecting commercial flights, arriving at 1230. He reported for work at 1500, and his duty was to end at 0330. He reported that he was able to get some sleep on the commercial flights.

HBPD did not have any policies in place for crew rest requirements prior to reporting for duty. AIRCRAFT INFORMATIONThe helicopter was owned by the City of Huntington Beach and was providing law enforcement air support under a contract service agreement for the City of Newport Beach.

The helicopter was designated as a 500N, but marketed as the 520N. It was a no tail rotor (NOTAR) design, which utilized a variable thruster and ducted fan system for anti-torque control rather than a traditional tail rotor. It was configured with dual flight controls with the right (TFO side) foot pedals removed. It had been equipped for law enforcement and included an external “Nightsun” searchlight, and a “WESCAM MX-10” gimbled imaging system, processed by an AeroComputers digital mapping system. METEOROLOGICAL INFORMATIONA High-Resolution Rapid Refresh (HRRR) model sounding was created for 1800 and 1900 for the accident location at varying altitudes. The 1800 data indicated that at an elevation of 313 ft msl, wind was from 281° at 14 kts, and at 1900 286° at 11 kts.

Sunset occurred at 1740, with dusk at 1805. The moon was below the horizon and rose at 2054. AIRPORT INFORMATIONThe helicopter was owned by the City of Huntington Beach and was providing law enforcement air support under a contract service agreement for the City of Newport Beach.

The helicopter was designated as a 500N, but marketed as the 520N. It was a no tail rotor (NOTAR) design, which utilized a variable thruster and ducted fan system for anti-torque control rather than a traditional tail rotor. It was configured with dual flight controls with the right (TFO side) foot pedals removed. It had been equipped for law enforcement and included an external “Nightsun” searchlight, and a “WESCAM MX-10” gimbled imaging system, processed by an AeroComputers digital mapping system. WRECKAGE AND IMPACT INFORMATIONThe helicopter came to rest on the seabed, submerged in saltwater about 45 ft from a beach within Newport Bay.

The fuselage was largely intact, with the landing skids and tailboom still attached. The stinger remained attached to the tail and had been displaced to the left. The cabin was intact, and the windscreen on both the pilot and copilot sides had broken out, leaving only the frame.

The main rotor drive assembly was still attached to the mast. Two rotor blades had separated from the rotor head and were recovered in the vicinity of the initial water impact, and the remaining three blades remained attached to the rotor head. The blades all exhibited varying degrees of aft bending, trailing edge buckling, and split skins at their trailing edges.

Examination of the flight control systems did not reveal any failures that would have precluded normal operation. The cyclic and collective controls were continuous from both the pilot and copilot's controls to the swash plate assembly.

The anti-torque blade drive system was still connected to the main transmission, and control continuity was confirmed from the pilot's anti-torque pedals through to the rotating cone and left vertical stabilizer bell crank. Pitch change of the anti-torque fan blades corresponded to movement of the foot pedals. The interior of the ducted tail boom was clear of debris and no damage was observed. The rotating diffuser cone sustained slight bending damage consistent with impact, but was intact. The stationary thruster was attached, and all thruster vanes were in place. The duct control assembly was intact and functional, and the anti-torque system appeared to have been correctly rigged.

The horizontal and vertical stabilizer assembly mounts had broken from the tail boom and the assembly remained connected by electrical cables and control linkages. First responders pulled the helicopter with a rope by the tail immediately following the accident to assist crew recovery. ADDITIONAL INFORMATIONFlight Training

HBPD provided annual recurrency training to their flight crews at either their facility in Huntington Beach, or at the factory facilities of MD Helicopters. The recurrency training for the pilot was completed 17 days before the accident. However, because HBPD was in the process of transitioning its fleet to the conventional tailrotor 500 series, “difference training” was performed, in an MD530F at MD in Mesa, Arizona.

The “Normal Operations” segment of the MD syllabus included a section devoted to “Low Speed Maneuvering”. According to MD, this part of the syllabus includes “loss of tail rotor effectiveness (LTE)” training in tail rotor helicopters and “unanticipated right yaw” training in NOTAR helicopters. According to MD, the 500N series helicopter is more susceptible to encountering unanticipated right yaw at higher speeds than the 530F helicopter, but with...