NYC95TA190

The police helicopter, along with ground units, was in pursuit of a suspect traveling on a dirt bike. The pursuit proceeded eastbound into a park and according to the pilot, he tried to fly ahead of the suspect. The pilot reported that he descended and turned south. He then decided to regain altitude, at which time, he heard or felt a vibration or thud; the next thing he remembers is being on the ground inverted. An observer aboard the helicopter reported the pilot, in a unsuccessful attempt to get ahead of the suspect, descended to about treetop height, leveled the helicopter, and then began to climb. He felt a vibration rumble through the helicopter followed by ground impact. Examination of the accident site revealed the helicopter came to rest on its left side with a separated 4 feet section of tailboom section located about 125 feet away. Examination of the aircraft did not disclose evidence of mechanical malfunction of the main rotor, tail rotor, drive system, flight controls, fuselage or engine. The engine was tested and operated at 3150 rpm for about 20 minutes at 25 inches of manifold pressure. Examination of the tailboom fracture surface revealed evidence of overstress and no evidence of pre-existing cracking was noted.

On August 12, 1995 about 1904 eastern daylight time, N7511E, a Schweizer 269C helicopter, an aerial patrol flight, operated by the Baltimore Police Department, collided with the ground at Baltimore, Maryland. Visual meteorological conditions existed. The pilot and observer received minor injuries. The helicopter was substantially damage. The flight originated at Martin State Airport, Baltimore, Maryland at 1800 hours eastern daylight time. The flight was operated under 14 CFR Part 91.

The pilot reported that he was following a suspect on a dirt bike who was being pursued by police ground vehicles. According to the pilot, he was flying eastbound along Baker Avenue and then over Easter Brook Park. He attempted to fly ahead of the suspect, so he descended and turned south over the park. He then decided to regain altitude at which time he heard or felt a vibration or thud; the next thing he remembers was being on the ground and inverted.

The observer reported, "the pilot and I were following a dirt bike wanted for hit and run of a Baltimore city police vehicle. The dirt bike was traveling east on Baker Street to Moreland Avenue. To avoid being apprehended by patrol units, the dirt bike entered Easterwood Park from Baker Street and Moreland Avenue traveling in a southeasterly direction. The pilot attempted to reposition the aircraft just ahead of the dirt bike so the operator could see us and possibly change his direction back toward the patrol units. The pilot descended approximately tree top level over the park. Being unsuccessful in getting ahead of the dirt bike the pilot leveled out the aircraft and began, in my perception to climb. At this time, I felt a vibration rumble through the aircraft. The next thing I remember is being on the ground hanging over the pilot in my seat."

Several witnesses saw the helicopter before it collided with the ground. One witness reported she heard the helicopter fly over the park at treetop level , heard a popping noise, and then saw it descend to the ground. She indicated the tailboom separated inflight.

A second witness reported he saw the helicopter come over the field at from the northwest and on an angle. A motorcycle was going across the field and the helicopter was over it before it impacted the ground. According to the witness, the engine made a pop sound when it first came across the field. He said the engine like the pilot was racing the motor.

A third witness reported he first heard normal motor sounds, but also heard what sounded like a loud pop, like a backfire. It was like a stutter , as if it were trying to fire back up.

A fourth witness reported that the helicopter was 75 to 100 feet above tree level . The helicopter entered a left bank , he heard a sputtering sound, then the helicopter slid into the ground.

A fifth witness reported the helicopter was about 50 feet high, when the the helicopter appeared to be attempting to turn left, but the nose when right . The helicopter subsequently impacted the ground.

The helicopter came rest on its left side and was oriented to the northeast. The helicopter was generally intact except for about 4 feet of tail boom section which was 125 feet southwest of the main wreckage. The main rotor remained attached to the hub.

The helicopter was transported to Martin State Airport where the airframe was examined under the supervision of the FAA. Examination of the airframe did not disclose evidence of mechanical malfunction of the main rotor, tail rotor, drive system, flight controls, or fuselage (see attached report).

The engine was sent to Lycoming Engine, at Williamsport, Pennsylvania to conduct an operational test under the supervision of the FAA. The engine was started and operated at 3150 rpm for approximately 20 minutes at 25 inches of manifold pressure (see attached report).

The separated tailboom section was examined at the NTSB Materials Laboratory, Washington, D.C. (see attached report). According the NTSB Metalurgist Factual Report, "the forward end of the boom was separated through the attachment holes for the saddle fitting. Visual examination revealed that the fracture in this area was on a slant (45 degrees) plane and was typical of an overstress separation. No evidence of fatigue cracking or other type of preexisting cracking was noted.