FTW94FA274

The pilot of a medical evacuation helicopter was maneuvering the helicopter to land on the airport ramp to pick up a patient from the awaiting ambulance. In order to avoid overflying trees, a hangar, and an untied airplane, the pilot executed a steep approach at low airspeed while side slipping the helicopter to maintain alignment on a track of 175 degrees. When the pilot began to adjust the collective to arrest his rate of descent, and slow his rate of closure, the RPM dropped and the aircraft made an unusual noise accompanied with airframe shuttering. The pilot reduced collective pitch and lowered the nose in an attempt to execute a running landing to a grass area adjacent to the intended landing area. The helicopter landed hard and bounced twice. The left landing gear crosstube collapsed when the helicopter contacted the shoulder of the taxiway. A post-impact fire started within 2 minutes, consuming the top of the cabin. The winds at the time of the accident were from 310 degrees at 15 knots, gusting to 20. Examination of the helicopter and engines did not disclose any mechanical anomalies.

History of flight

On August 19, 1994, at 1520 central daylight time, a Bell 230 helicopter, N230EM, was substantially damaged during a loss of control while landing at the Albert Lea Municipal Airport, near Albert Lea, Minnesota. The airline transport rated pilot and his three medical technicians were not injured. Visual meteorological conditions prevailed for the positioning flight.

The helicopter, owned by Omniflight of Dallas, Texas, and operated by the Mayo Medical Center of Rochester, Minnesota, was dispatched from Rochester to Albert Lea, Minnesota, to pick up and transport a patient.

According to the pilot, he was executing a steep approach at a slower than normal airspeed to avoid obstacles below his flight path. His intended point of landing was on the congested airport ramp where an ambulance awaited his arrival.

The pilot further stated that he configured the aircraft on a left slip to maintain his alignment over the taxiway on a track of 175 degrees. The helicopter was 50 to 60 feet AGL, at an estimated airspeed of 25 to 30 knots, when he began to adjust the collective to arrest the rate of descent, and slow the rate of closure. He noticed an RPM drop, and an unusual noise accompanied by an airframe shutter.

The pilot added that he reduced collective pitch and lowered the nose in an attempt to execute a running landing to a grassy area west of the intended landing area on the ramp.

Witnesses at the site stated that the helicopter touched down hard and bounced. During the ground slide the landing gear skid caught the shoulder of the taxiway resulting in a loss of control. The cross tubes for the left landing gear skid assembly collapsed and the main and tail rotor blades impacted the ground.

According to the AWOS at the airport, the winds at the time of the accident were reported from 310 degrees at 15 knots, gusting to 20 knots.

Personnel information

The pilot was a certificated A&P mechanic. The pilot and the three medical technicians on board the helicopter were able to egress from the helicopter on their own.

Aircraft information

Weight and balance calculations were performed using figures provided by the operator. The helicopter was found to be within limits. A review of the airframe and engine records by Federal Aviation Administration (FAA) inspectors, did not reveal any anomalies or uncorrected maintenance defects prior to the flight.

Wreckage and impact information

The helicopter contacted the ground on a measured heading of 180 degrees as evidenced by the ground scars made by the skid tubes. The wreckage came to rest on the taxiway on a measured heading of 245 degrees, approximately 19 feet beyond the edge of the taxiway. The total ground run from the initial point of touchdown to the resting place of the main wreckage was measured at 93 feet. Imprints corresponding to the left skid cross tube were found at the edge of the taxiway. Slash marks and paint transfers were found on the asphalt taxiway matching the size and shape of the tip of the main rotor blades.

Both engines remained attached to the airframe, while the main transmission and the main rotor mast were partially separated. No evidence of mast bumping was found. The tailboom was found separated from the aircraft. Evidence of tail rotor rotation were found on the drive shaft and drive shaft tunnel cover. Both tail rotor blades exhibited leading edge damage.

Continuity was established to the flight controls and the tail rotor system. See wreckage diagram for details of the flight and ground path of the helicopter, as well as wreckage distribution pattern.

Fire

A post-impact fire consumed the top of the cockpit and cabin areas, but did not penetrate or distort the cabin or cockpit areas of the helicopter. According to witnesses on the ground, the fire started on the right side of the helicopter, within 2 minutes after the aircraft came to a stop on the taxiway. The on-board engine fire suppression system was not activated. No evidence of pre-impact fire was found during the investigation.

Test and research

A wreckage layout and examination was accomplished. Both engines were removed from the wreckage and transported to the engine manufacturer's facility for examination and teardown. The aircraft fuel system was examined and tested to verify the integrity of the suction fuel feed system for both engines. The helicopter's on-board vibration monitoring system was removed to determined if the equipment had recorded any unusual vibrations prior to the accident; however, none was detected. Examination of the helicopter and engines did not disclose any mechanical anomalies that would have prevented normal operations.

Additional data

The wreckage was released to the owner's representative upon completion of the investigation.