Accident at Kalaheo, Hawaii, 24 Sept 2004 (N16849)

Accident narrative

On September 24, 2004, about 1642 Hawaiian standard time, a Bell 206B helicopter, registration N16849, impacted mountainous terrain in Kalaheo, Hawaii, on the island of Kauai. The commercial pilot and four passengers were killed, and the helicopter was destroyed by impact forces and a postcrash fire. The nonstop sightseeing air tour was operated by Bali Hai Helicopter Tours, Inc., under visual flight rules (VFR) with no flight plan filed. Instrument meteorological conditions prevailed near the accident site.

### The flight

The pilot, 39, held a commercial pilot certificate for rotorcraft helicopters. A citizen of India, he had retired from the Indian Air Force in 2003 and had accumulated 4,005 total flight hours, including 3,900 hours in turbine-powered helicopters. He was hired by Bali Hai in July 2004, marking his first civilian pilot job and his first experience in Bell 206 helicopters. He had accumulated 120 hours of flight experience in the company’s helicopters by the date of the accident.

The helicopter, manufactured in 1978, was not certificated for instrument flight rules (IFR) operations. It was scheduled to depart Port Allen Airport about 1600 for a 45-minute clockwise sightseeing tour of Kauai, passing locations including Waimea Canyon, the Na Pali Coast, Waialeale Crater, and Manawaipuna Falls.

The flight was conducted under Special Federal Aviation Regulation (SFAR) 71, which established a minimum altitude of 1,500 feet above ground level for Hawaii air tours. Bali Hai held a Federal Aviation Administration (FAA) certificate of waiver allowing its pilots to fly specific transition segments at 1,000 feet and cross certain ridgelines at 500 or 200 feet.

This was the pilot’s eighth and final tour flight of the day. Bali Hai’s practice was to keep the helicopter running with its rotors turning continuously between tours to reduce engine wear. During the 5 to 15 minutes of ground time between flights, the pilot remained in the cockpit while a line service technician added fuel. He did not leave the helicopter for a lunch break. By the time of the accident, the pilot had been on duty for about 8.7 hours and had been at the controls with the rotors turning for at least 7.7 consecutive hours.

### The accident sequence

Digital photographs recovered from a passenger’s camera showed that the weather appeared sunny with good visibility when the helicopter departed. Subsequent images taken during the tour showed low clouds and precipitation near some locations. The National Weather Service had issued an airmen’s meteorological information (AIRMET) advisory for temporary moderate turbulence below 5,000 feet, and the area forecast called for scattered to overcast clouds and moderate rain showers.

Air traffic control radar data showed the helicopter entered the area north of Mount Waialeale about 1635. The helicopter’s transponder transmitted a constant, erroneous altitude of 1,000 feet mean sea level throughout the flight, preventing investigators from determining its actual flight altitudes.

About 1641, the radar track showed the helicopter crossing a 2,000-foot ridge extending east from Kahili Ridge. The helicopter tracked west toward a pass at the top of the ridge, then crossed Kahili Ridge. About 1642, on the west side of the ridge, the helicopter turned north, then made a 180-degree clockwise turn toward the south. It crossed back to the east side of Kahili Ridge in a zigzag pattern before it was lost from radar at 1642:46.

### What the investigation found

The wreckage was located the next day on the east side of Kahili Ridge, about 200 feet below the crest at an elevation of 2,850 feet. It rested on a 75-degree slope covered by thick vegetation, with the main concentration of debris scattered southwest up the steep slope. The top of the cockpit and cabin structure was crushed upward, and the tail boom was deformed downward.

Examination of the airframe, flight controls, and rotor systems revealed no evidence of a precrash mechanical malfunction. The engine’s compressor impeller shroud displayed rotational scoring, and the fuel control unit’s pointer indicated the throttle was full open. The attitude indicator’s internal rotor showed circumferential scoring consistent with rotation at impact. The damage characteristics and debris distribution suggested the helicopter struck the terrain in an extreme nose-high attitude with a high engine-power setting.

A review of Bali Hai’s maintenance records revealed numerous discrepancies, including conflicting airframe and engine total times and a failure to record minor discrepancies or nonrevenue flight hours. However, these record-keeping issues were not found to have contributed to the accident. Toxicology tests on the pilot were negative for carbon monoxide, cyanide, and illegal drugs.

Weather radar data indicated that a line of weather echoes containing rain showers was converging on the ridge near the accident location about the time of the accident, associated with cloud bases lowering below 2,400 feet. The Board noted that the pilot could have deviated east toward the coastline, where weather was clearer and where Bali Hai was authorized to fly transition segments at 1,000 feet. Instead, the pilot chose to fly south along his usual tour route as the advancing line of clouds closed in on the high terrain.

The Board concluded that the pilot’s inexperience with Hawaii weather conditions affected his ability to make appropriate in-flight decisions when faced with deteriorating weather. Experienced local pilots told investigators that Kauai’s rapidly changing visibility and cloud conditions made visual assessment critical. The accident pilot had received no specific training on Kauai weather patterns.

The Board also evaluated the pilot’s workload and physical condition. The pilot had been at the controls for nearly eight hours without scheduled breaks or access to restroom facilities. The Board noted that these conditions increased the risk of dehydration and fatigue, and concluded that the operator’s pilot-scheduling practices, although permitted under Federal aviation regulations, likely had an adverse impact on pilot decision-making and performance.

Encountering instrument meteorological conditions in a helicopter not equipped for IFR flight imposes high perceptual and motor demands. The Board noted that spatial disorientation occurs when visual cues are lost and a pilot relies on misleading vestibular sensations. The Board concluded that the helicopter’s descending spiral flightpath, which became increasingly erratic in the final seconds, was consistent with pilot spatial disorientation resulting from the transition to instrument conditions, high workload, and sustained turns.

The investigation also reviewed the FAA’s oversight. Bali Hai operated under 14 CFR Part 91, which exempted it from the stricter pilot flight time, duty period, and training requirements of Part 135. The Honolulu Flight Standards District Office (FSDO) lacked the staffing to perform direct surveillance of air tour operations. A Geographical Surveillance Unit that had previously monitored tour flights for compliance with minimum altitude and weather restrictions had been disbanded in May 2004 due to staffing shortages. The Board concluded that the FAA had not provided sufficient resources for the FSDO to implement air tour surveillance, which might have detected and corrected risky flying practices.

### Probable cause

The National Transportation Safety Board determines that the probable cause of this accident was the pilot’s decision to continue flight under visual flight rules into an area of turbulent, reduced visibility weather conditions, which resulted in the pilot’s spatial disorientation and loss of control of the helicopter. Contributing to this accident was the pilot’s inexperience in assessing local weather conditions, inadequate Federal Aviation Administration surveillance of Special Federal Aviation Regulation 71 operating restrictions, and the operator’s pilot-scheduling practices that likely had an adverse impact on pilot decision-making and performance.