N4995G

History of the Flight

On January 28, 1994, about 0737 hours Pacific standard time, a Sikorsky S58-JT, N4995G, crashed on a high-rise building during an external load operation at San Jose, California. The helicopter was being operated as a visual flight rules (VFR) local flight under Title 14 CFR Part 133 when the accident occurred. The helicopter, registered to and operated by Air One Helicopters Inc., San Jose, California, was destroyed by impact and postimpact fire. The certificated airline transport pilot, the sole occupant, received fatal injuries. Visual meteorological conditions prevailed. The flight originated at the San Jose International Airport about 0722 hours.

The operator reported that the helicopter was being utilized to remove a large cooling tower fan from the top of a 13-floor building located in the business district of the city. The pilot contacted the ground controller at the San Jose Air Traffic Control Tower (ATCT) at 0720:18 hours and requested permission to taxi for takeoff. At 0722:05 hours, the aircraft was cleared for departure by the local controller and at 0724:08 hours, the pilot reported as "on station". The building is located about 1 1/2 miles southeast of the airport.

A three-man ground crew from the helicopter operator and an air conditioning company were assigned to the operation. A helicopter company employee, a member of the ground crew, reported that the helicopter was originally going to land in the west parking lot of the building to attach a 100-foot Kevlar lifting cable to the belly of the aircraft; however, the landing area was restricted by numerous light poles. The crew member attached the cable to the helicopter while it was at a hover over the top of the building. The crew disassembled a portion of the cooling tower and the helicopter successfully removed a large fan to the ground level parking lot. The helicopter then deposited a 1,800-pound steam cleaning machine on the roof, adjacent to the tower.

The crew on the building unhooked the machine from the lifting cable and was preparing to unhook the cable from the helicopter. As the helicopter was at a 100-foot hover above the building, the crew heard the engine sounds decrease and observed the main rotor blades begin to slow. The helicopter then descended vertically onto the top of a two-level central core penthouse building that housed elevator, boiler, and air-conditioning machinery. After contacting the penthouse roof, the helicopter began to roll onto its right side.

The main rotor blades contacted the building parapet wall and separated near the inboard ends of the blades. A postcrash fire erupted and the crew attempted to fight the fire with hand extinguishers. The crew indicated that during the impact the vertical tail section of the fuselage separated. After the helicopter came to rest, the main rotor blade roots still attached to the mast were still turning and they could hear the engines still spooling down and then stop completely. The crew was not injured and no persons on the ground level were injured. At 0737:12 hours, a pilot reported the fire on the roof of the building to the San Jose ATCT.

A Federal Aviation Administration (FAA) operations inspector, San Jose Flight Standards District Office (FSDO), was observing the lifting operation from the ground-level west parking lot to monitor the flight's compliance with a 14 CFR Part 133 external load plan. He reported that the helicopter was facing toward the west while hovering above the roof and heard the sound of the engine(s) spooling down. The helicopter nose pitched down about 5 degrees and descended vertically without any fuselage yaw. The main rotor blades began slowing down and the helicopter descended out of view. Portions of the main rotor blades fell away from the roof top into the parking lot. The inspector observed smoke and fire about 5 seconds after the crash.

Numerous ground witnesses also reported hearing the engine sounds decrease and the main rotor blades slowing down. The initial fire started as a small flame near the cabin area that quickly spread, engulfing the helicopter. The witnesses reported seeing extremely bright sparks emanating from the fire.

The accident occurred during the hours of daylight at attitude 37 degrees, 20.91 minutes north and longitude 121 degrees 54.08 minutes west.

Other Damage

The building received impact and fire damage to the penthouse building and exterior of the roof area. In addition, several upper floors of the building received water damage.

Crew Information

The pilot held an airline transport pilot certificate with a rotorcraft helicopter rating, and type ratings in Bell 206 and Sikorsky S58 aircraft. He held commercial pilot privileges with a single-engine land rating. In addition, the pilot held a flight instructor certificate with a rotorcraft helicopter rating. He also held a mechanics certificate with airframe and powerplant ratings. The most recent second-class medical certificate was issued to the pilot on August 19, 1993, and contained no limitations.

No personal flight records were located for the pilot and the aeronautical experience listed on page 6 of this report was obtained from a review of the airmen FAA records on file in the Airman and Medical Records Center located in Oklahoma City. In addition, information was obtained from a review of records maintained by the operator.

According to the information entered on the pilot's application for medical certificate dated August 19, 1994, his total aeronautical experience consisted of 7,000 hours. The operator reported that the pilot had accrued 6,200 hours in helicopters and 1,500 hours in the accident aircraft make and model. In the preceding 90 and 30 days prior to the accident, the report lists a total of 43 and 19 hours, respectively, flown. The operator provided an undated letter from the San Jose FSDO indicating that the pilot was qualified as serve as pilot-in-command in external load operations.

The chief pilot reported that the pilot received annual recurrent training, including a check ride, for 14 CFR Part 135 operations. The company does not conduct (nor is one required under Part 133) ground or flight training in external load operations. Since external loads are constantly being conducted, the accident pilot was routinely observed by ground personnel including the chief pilot. The ground crew indicated that no mission briefing was conducted prior to the accident flight.

Aircraft Information

The accident aircraft is equipped with twin Pratt and Whitney PT-6T engines that provide independent power to a combining gearbox. The gearbox drives a single output shaft connected to an angle gearbox, which provides power input to the main rotor transmission. The aircraft is certified as a single-engine helicopter.

The recording hour meter in the aircraft was destroyed. Prior to departure on the accident flight, the aircraft maintenance log sheet indicated that the helicopter had accumulated a total time in service of 8,523.8 flight hours. The helicopter was utilized almost exclusively for external load operations and was maintained according to the manufacturers' inspection program. Examination of the maintenance records revealed that the most recent Phase III inspection was accomplished on August 8, 1993, 47.4 hours before the accident. The left engine had accrued a total time in service of 6,456 hours of operation. The maintenance records note that a major overhaul was accomplished on February 5, 1980, 2,927.5 hours of operation before the accident.

The right engine had accrued a total time in service of 5,661.7 hours of operation. The engine was overhauled on September 10, 1984, 2,206.7 hours before the accident.

The combining gearbox had accrued a total time in service of 5,747.6 hours of operation. The gearbox was overhauled on November 21, 1983, 2,778.1 hours before the accident.

Examination of the maintenance and flight department records revealed no unresolved maintenance discrepancies against the aircraft prior to departure.

The aircraft fuel system consists of a forward and aft tank. The forward tank is partitioned into six cells. The aft tank consists of two interconnected tanks partitioned into three cells each. The left engine is supplied by the forward tank and the right engine from the aft. Each engine has an engine-driven fuel pump and an electrical boost pump. The fuel supply to each engine is controlled by an electrical shut-off valve. Both engines may receive fuel from either the forward or aft fuel tank by opening an electrically operated cross-feed valve. The aircraft is equipped with low fuel pressure and low fuel quantity caution annunciator lights, one for each engine. A low fuel quantity annunciator activates when 120 pounds, plus or minus 30 pounds, remain in their respective tank. The unusable fuel in the forward tank is 3.5 gallons and 6.0 gallons in the aft tank (a total of 63.7 pounds).

The operator reported that on January 26, 1993, the accident aircraft returned from an external load flight. Upon landing, the chief pilot who conducted the flight reported that the fuel gauges indicated 200 pounds of total fuel with 100 pounds each in the forward and aft tanks. No fuel was added following the flight. On January 27, 1993, the pilot of the accident aircraft flew .2 hours on an external load flight. There was no indication on the company fuel log that any fuel was added before or after that flight. On January 28, 1993, the pilot added 30 gallons (201 pounds) of fuel before the accident flight.

According to the operator, the helicopter normally operates with a basic fuel load of 200 pounds in each tank. The aircraft has an average fuel burn of 100 gallons (670 pounds) per hour.

National Transportation Safety Board investigators calculated the fuel on board at the time of the accident. Using an average weight of 6.7 po...