What happened
On July 23, 2009, at approximately 2226 EDT, a Robinson R44 helicopter, registration N7189W, crashed near Boonsboro, Maryland, while in cruise flight. The aircraft was traveling from Hagerstown Regional Airport (HGR) to Frederick Municipal Airport (FDK) for a business flight under Part 91 regulations.
Earlier that evening, the pilot had conducted several short passenger rides at HGR. Although the pilot and passengers initially boarded the helicopter for the return trip to FDK, they returned to the terminal due to deteriorating weather. The pilot contacted an employee near FDK twice to inquire about conditions; the employee reported severe thunderstorms, fog, and lightning, and even offered to drive the occupants to their destination by car. The pilot declined the offers, opting to wait for the weather to improve.
The helicopter departed HGR at approximately 2215. During the flight, the aircraft flew over Interstate 70 near the top of South Mountain. Witnesses observed the helicopter flying parallel to the interstate before it appeared to enter low clouds and turn around. The aircraft then struck an unmarked, steel guy-wire that extended perpendicularly over the highway. The impact caused the helicopter to crash and burst into flames. The accident resulted in 4 fatal injuries.
The investigation
Investigators examined the wreckage and found that the helicopter struck a 70-foot-high guy-wire, subsequently damaging 34.5 and 12-kilovolt power lines. The aircraft left a ground scar in the center median and came to rest on its left side. A post-crash fire consumed the cabin, much of the main rotor gearbox housing, and all drive belts.
Mechanical analysis of the Robinson R44 revealed:
- The main rotor blades exhibited impact damage, with one blade missing its tip.
- One main rotor pitch change link was disconnected, and the upper swash plate connection was fractured.
- The engine, a Lycoming O-540-F1B5, remained contained in its compartment; examinations of the magnetos, spark plugs, and carburetor showed no evidence of pre-impact malfunction.
- The fuel was found to be light blue and free of visible contamination or water.
- No evidence of pre-impact mechanical failure was found in the airframe, engine, or drive systems.
Radar data showed the aircraft was flying at approximately 1,100 feet MSL. During the final two minutes of flight, the terrain elevation rose from 600 feet to nearly 1,200 feet MSL. The aircraft's ground speed decreased from 57 knots to 25 knots during the final 20 seconds of the flight.