History of Flight
On 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.
As the flight was about to depart the Newport Beach area, the crew received a transmission over the primary police radio channel that a fight was taking place just south of their location. The pilot redirected the helicopter toward the area and began a right orbit between 500-600 ft above ground level (agl) while the TFO turned on the infrared camera and began searching the ground. The TFO spotted a group fighting, and the pilot maneuvered the helicopter in a tighter orbit while the TFO relayed his observations.
Ground patrol officers arrived on the scene, and the pilot continued orbiting about 500 ft agl, simultaneously viewing the activity through his monitor, and maneuvering so the TFO could continue to observe. The pilot watched as ground officers approached the group, which had mostly dispersed. Concerned that a person was about to fight with an officer, he slowed the helicopter to about 50 knots indicated airspeed to keep the camera aimed at the scene.
Suddenly, the helicopter yawed aggressively to the right. The pilot immediately applied full left foot pedal and forward cyclic but there was no response. He then applied right pedal to test the pedals, then reverted to full left pedal. Continued corrective inputs did not stop the rotation and the helicopter began a spinning descent. The TFO transmitted over the police radio, “We’re having some mechanical issues right now,” followed by “we’re going down, we’re going down.”
The pilot modulated throttle, collective, and cyclic to try to arrest the rotation. Efforts appeared partially effective, but with no horizon or external reference due to darkness, impact was imminent. He pulled collective to bleed off airspeed. The helicopter hit the water hard on the TFO’s side while rotating. The canopy shattered, and the pilot became submerged.
Security and witness cameras captured the spinning descent. Footage showed the engine sound until impact, no smoke, and violent pitch oscillations. The transition to spin was not captured, but one camera showed the helicopter already spinning when it reappeared from behind a building.
Personnel Information
The pilot was hired by HBPD in 2005, initially as a TFO, later attaining a commercial pilot certificate. At the time, he was the second most experienced pilot at HBPD, with about 3,700 flight hours as pilot-in-command of the MD500N. He typically flew 12 to 20 hours per month, half at night.
The day of the accident was the first of a three-day shift. He had been off in Spokane, Washington. He woke at 0400, flew commercial to Long Beach, arriving at 1230, and reported for work at 1500. His duty was to end at 0330. He slept on the flights. HBPD had no policies for crew rest before duty.
Aircraft Information
The helicopter was owned by the City of Huntington Beach and provided law enforcement air support under a contract for the City of Newport Beach. It was a 500N (marketed as 520N) with a NOTAR design, using a variable thruster and ducted fan for anti-torque. It had dual controls with right foot pedals removed, and was equipped with a Nightsun searchlight and WESCAM MX-10 imaging system.
Meteorological Information
A HRRR model sounding for 1800 and 1900 at the accident location indicated winds at 313 ft msl from 281° at 14 kts (1800) and 286° at 11 kts (1900). Sunset was at 1740, dusk at 1805. The moon was below the horizon until 2054.
Wreckage and Impact Information
The helicopter came to rest on the seabed, 45 ft from a beach in Newport Bay, submerged in saltwater. The fuselage was largely intact with landing skids and tailboom attached. The stinger was displaced left. Cabin windscreens were broken out.
Two main rotor blades separated from the rotor head and were recovered near initial water impact; three remained attached. Blades showed aft bending, trailing edge buckling, and split skins.
Examination of flight controls found no pre-impact failures. Cyclic and collective continuity was confirmed. The anti-torque blade drive system was connected, control continuity from pedals to rotating cone and bell crank was verified. The ducted tail boom was clear, and the rotating diffuser cone had slight bending impact damage. The thruster and vanes were intact. The Y-SAS actuator was found extended to nearly full right travel limit.
Additional Information
Flight Training
HBPD provided annual recurrency training. The pilot completed training 17 days before the accident, but due to fleet transition, difference training was done in an MD530F. The MD syllabus for 500N includes unanticipated right yaw training. The pilot last performed low-speed maneuvering in the 500N in 2015; his last night emergency training was in May 2018.
The MD600N RFM gives guidance on unanticipated right yaw: it can occur at low altitude and airspeed when a pilot is distracted; left sideslip or winds from left can cause right yaw. Prompt left pedal and cyclic inputs can stop it. The MD500N RFM does not specifically address unanticipated right yaw.
FAA Advisory Circular 90-95 states that high-power, low-airspeed maneuvers with left crosswind or tailwind can cause unanticipated right yaw, with greater susceptibility in right turns.
Flight Recorders
ADS-B and GPS data showed the helicopter slowed to 15-23 kts ground speed, corresponding to 3-12 kts calibrated. It then pointed south, moved west, and began a right spin at about 130° per second, which continued until impact.
Medical and Pathological Information
Autopsy determined the TFO's cause of death as drowning, with no significant injuries noted besides chest abrasions and rib/sternum fractures consistent with resuscitation. Toxicology was negative for drugs or alcohol.
Survival Aspects
Both crew wore flight suits, dual-visor helmets, inflatable life preserver/tactical vests, and emergency breathing systems. Night vision goggles were stowed. After impact, the pilot held the collective, cleared his air bottle mouthpiece, released his harness, and egressed by pushing off the collective. He disconnected his helmet cord and surfaced. He called for the TFO but did not get a response. Witnesses pulled him to a boat, and he urged them to find the TFO.
A witness dived in using the pilot's air bottle but initially found a tactical bag. After the pilot indicated the wrong side, he tried again but could not find the door. First responders arrived and pulled the helicopter closer to shore. A diver found the TFO halfway out of the front left door window, seat harness unbuckled, helmet cord disconnected. He appeared uninjured, but his leg was stuck. After freeing him, they recovered him.
The TFO's inflatable vest had not deployed; the air bottle's valve was open and bottle empty. Both seat belts were unlatched. The canopy and lower windows had shattered.
Both crew had completed shallow water egress training (SWET) on January 27, 2020, which included emergency breathing device use.
Tests and Research
Flight demonstrations in a factory 520N showed that once unanticipated right yaw began, prompt left pedal and forward cyclic could arrest it; aft cyclic increased yaw rate. Recovery depended on external visual references.
The Y-SAS system enhances directional stability. At slow airspeed with large right pedal, the thruster provides dominant yaw control. The Y-SAS actuator was found near full right travel limit.
Post-accident examination of Y-SAS components revealed saltwater corrosion. The actuator chattered and did not respond during functional test. An inductor in the circuit board had a longitudinal crack with brown deposits, not coated like other components.
1991 flight tests of the NOTAR design showed Y-SAS hard-overs did not degrade handling; hard-overs below 40 kts had little effect.
Probable Cause
Not stated in source.