History of Flight
On July 16, 2022, about 1920 mountain daylight time, a Bell UH-1H, registration N911SZ, was substantially damaged when it impacted terrain near Chapelle, New Mexico. The pilot, two tactical flight observers, and a rescue specialist sustained fatal injuries. The helicopter was operated as a public aircraft flight under Title 41 United States Code.
The helicopter had completed several firefighting missions for the New Mexico Forestry Division, refueled at Las Vegas Municipal Airport (LVS), and departed about 1838. It flew to the dip site and staging area, operated at the firefighting location, then returned to the staging area to pick up the remaining crew for the return flight to Double Eagle II Airport (AEG), Albuquerque. About 1915, the helicopter departed westbound. Automatic dependent surveillance-broadcast (ADS-B) data at 1920 showed the helicopter level at 500-600 ft above ground level, 133 knots groundspeed, about 0.5 mile east of the accident site. Onboard data recorded a descent beginning at 1920:01, reaching 5,433 feet per minute descent and 102 knots by 1920:13. Two witnesses observing the sunset from a ridge 0.5 mile east reported the helicopter flew past westbound, then rapidly descended without turning, followed by a large dust plume on impact.
Personnel Information
A pilot previously in the unit stated that the accident pilot had completed annual flight training at HeliStream, including autorotation training. His last annual training was flown in a Eurocopter AS350; a review of flight records indicated he had not recently conducted emergency flight training in a UH-1.
Aircraft Information
The helicopter was a Bell UH-1H with a two-bladed main rotor and two-bladed tail rotor, powered by an Ozark Aeroworks engine. The Bernalillo County Sheriff’s Department purchased it from the US Army on March 11, 1999, and it was registered as a government aircraft on March 9, 2000.
Meteorological Information
Around the accident time, the sun’s elevation was about 6.4° and azimuth about 291°.
Wreckage and Impact Information
The wreckage was located in high southwestern desert terrain with scrub juniper bushes. The initial impact was identified by disturbed ground in the shape of the helicopter tail and fuselage. The tailboom was crushed and the tail skid “stinger” bent upward, consistent with very hard ground contact. The tail boom separated from the main fuselage, both located about 122 ft west of initial impact. The main rotor was about 40 ft left of the main wreckage, with the main rotor mast fractured below the hub. One main rotor blade was minimally damaged; the other was fractured at the spar. Rotor drive and flight control continuity was confirmed, and no anomalies were observed in hydraulic or fuel systems. A minimal amount of foreign debris (primarily dirt) was found in the engine intake, compressor, and turbine sections. The N1 tachometer-generator was clean but would not rotate. The starter-generator drive shaft and input (zerol) gear were both fractured. The magnetic chip plug in the N1 accessory gearbox had a large quantity of metallic chips. Multiple metallic fragments were found in bearing compartment oil return lines; supply lines were clean. Two helical-cut gear teeth similar to zerol gear teeth were found in the oil, both exhibiting expected wear patterns. Metallurgical examination of the zerol gear revealed multiple fatigue fractures and gouging on both flanks and lands of the gear teeth. The gear failed in fatigue from a crack that formed 90° to the original, progressing across the gear. No material anomalies were observed that would result in crack initiation.
Additional Information
On September 12, 2021, an engine chip event was documented. A precautionary landing occurred after an engine chip light; a small piece of ferrous metal was found on the magnetic chip plug. Corrective actions included draining and flushing the system and cleaning filter elements. No further chip lights were reported, but no laboratory analysis of the chip was obtained. The helicopter flew about 17 hours between the chip event and the accident. Oil sampling showed increasing iron content over time. The main generator was removed on March 22, 2017, for weight reduction, and an “inop” sticker was placed on the voltmeter. Bell safety personnel noted the configuration had not been evaluated for adverse effects on component life. US Army records indicated no similar zerol gear failures, and the gear was not a tracked part. Performance calculations estimated density altitude at 9,059 ft and indicated airspeed of 100-110 knots based on winds.
Medical and Pathological Information
An autopsy of the pilot determined the cause of death as blunt force injuries. Toxicology testing was negative for all screened drugs and alcohol.