History of Flight
On May 29, at approximately 1101 eastern daylight time, a Sikorsky S-76A helicopter, registered as N176SH, was destroyed by a post-impact fire after its tail rotor struck a tower while departing from the heliport (MI97) on top of Spectrum Health Hospital in Grand Rapids, Michigan. The flight, which departed Gerald R. Ford International Airport (GRR) at 1041, was operated under 14 Code of Federal Regulations Part 91 and was conducted as a Federal Aviation Administration (FAA) Part 135 check, including an annual Sikorsky proficiency check and a 6-month helicopter instrument proficiency check.
The crew, consisting of an airline transport pilot and an FAA inspector, flew the FAA-approved GPS point-in-space approach to a termination point south of the hospital before landing on the north spot of the helipad. Before takeoff, the pilots discussed construction cranes operating on the north side of the hospital. The pilot reported lifting the helicopter straight up; at about 40 feet, he heard a "pop," and the helicopter began to yaw right and vibrate. Despite adding left pedal, the right yaw rate increased rapidly. The pilot attempted to land back on the pad, but the main rotor blades struck a 32-foot-high brick structure east of the helipad, causing the helicopter to fall straight down onto the hospital roof.
The FAA inspector, seated in the left seat, described a normal vertical takeoff to about 40–50 feet. He heard a "pop" and saw the pilot moving the cyclic; the helicopter turned right, descended, and the main rotor blades hit the building. Both pilots exited through the copilot's chin bubble and took shelter behind a heating duct until firefighters arrived. A fire started during the initial impact and soon consumed the helicopter.
A hospital nurse witnessed the helicopter lift off and fly backward toward the brick structure, observing the tail rotor hit a tower. Another witness, from a seventh-floor window across the street, reported that the tail rotor clipped a radio tower about mid-span and immediately disintegrated. A security video from the hospital showed the helicopter landing, then lifting off and flying backward toward the brick structure while the nose pointed northwest. The shadow of the tail rotor appeared to strike an object on one of the towers, after which the tail rotor shattered and the helicopter yawed right. The video captured the main rotor blades impacting the brick structure but did not record the final impact on the roof. A camera mounted on one of the towers exhibited impact marks and carbon fibers lodged in a crevice.
Personnel Information
The pilot, age 61, held an airline transport pilot certificate with single-engine and multi-engine airplane and helicopter ratings, along with instrument ratings. He had approximately 7,260 total flight hours, including about 6,760 hours in helicopters. He had flown about 25.8 hours in the accident make and model in the preceding 90 days and held a second-class medical certificate issued March 18, 2008.
The FAA inspector, age 57, also held an airline transport pilot certificate with corresponding ratings and instrument privileges. He had about 7,000 total flight hours, with about 1,200 hours in helicopters. His second-class medical certificate was issued January 24, 2008.
Aircraft Information
The Sikorsky S-76A (serial number 760260), manufactured in 1984, was powered by two Allison 250-C30S engines. Aero Med purchased the helicopter in 1997 and configured it for emergency medical services. It was equipped with dual electronic flight information systems and dual digital automatic flight control systems, and was certified for instrument flight rules. Maintenance was conducted per an FAA-approved aircraft inspection program, and records indicated the helicopter was airworthy at the time of the flight. The helicopter had logged 5,195.4 hours and 19,153 cycles. The reported takeoff gross weight was 9,762 pounds, with a center of gravity of 200.3 inches, both within limits.
Meteorological Information
At 1053, the surface weather observation at GRR, about 8 nautical miles south of the accident site, reported calm winds, visibility 10 miles, a broken ceiling at 22,000 feet, temperature 18°C, dew point -7°C, and altimeter 30.25 inHg.
Heliport Information
The heliport atop the 10-story hospital consisted of two landing pads oriented north and south at an elevation of 880 feet. Directly east of the pads was a 32-foot-high elevator penthouse topped with a windsock on a 14-foot pole, a large triangular lattice truss antenna extending about 40 feet higher, a small Doppler radome, and other antennas. A TV camera was attached about mid-point on the 40-foot antenna. Several large construction cranes were located within a few hundred feet of the helipad; the three closest were west, northwest, and north of the pad and extended less than about 50 feet above it.
Wreckage and Impact
The helicopter was largely consumed by fire, with remnants of the left side cockpit and cabin doors, a portion of the lower tail cone and vertical pylon, and all three landing gear in the down position. The transmission, engines, tail rotor drive shafts, intermediate gearbox, and input and center sections of the tail rotor gearbox remained in place. The outer housing of the tail rotor gearbox with the tail rotor hub attached was found on the helipad about 12 feet from the vertical pylon. All four main rotor blades were broken into several segments from impact with the penthouse; blade fragments were found north and northwest of the site. Outboard tail rotor blade fragments were scattered but could not be matched due to fire damage. The post-crash fire destroyed most of the flight control system, though stainless steel tail rotor control cables were intact aft of a break at about Station 300, consistent with overload from ground impact. The engines showed no leading-edge damage to compressor impellers or visible casing damage; turbine modules appeared undamaged externally, but fuel control units were fire-damaged.
Tests and Research
An accident investigation officer from the Grand Rapids Police Department provided a report based on laser measurements and analysis of the security video. The analysis indicated the helicopter traveled a straight-line distance of about 61 feet at an angle of about 41 degrees relative to the pad as it moved backward to where the tail rotor impacted the camera on the tower. The time from takeoff to impact was about 11.37 seconds. According to the U.S. Naval Observatory, at the time of the accident, the sun's azimuth was 109.7 degrees and elevation 50.6 degrees. The video showed the helicopter lifting off, yawing left on a heading of about 315 degrees while climbing; the shadow on the pad remained nearly stationary, indicating rearward climb nearly parallel to the sun incidence line of about 51 degrees.
Additional Information
In September 2008, Aero Med implemented an enhanced safety management system program. The heliport (MI97) at Spectrum Health Hospital was closed until both helipads were enlarged and enhanced fire suppression systems were installed. The 40-foot antenna and Doppler antenna were relocated, and other antennas and the windsock were moved to the east side of the penthouse.