History of Flight
On December 1, 2012, about 1420 central standard time, a Bell 47G-2 helicopter, registration N3755Z, collided with trees and impacted terrain near Walkerville, Michigan. The commercial pilot sustained fatal injuries, and the passenger sustained serious injuries. The helicopter was substantially damaged. The aircraft was owned and operated by a private individual under 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed, and the flight operated without a flight plan. The flight originated from private property at an undetermined time. According to information from local law enforcement and Federal Aviation Administration inspectors, the helicopter was traveling at a low altitude when the passenger heard a loud noise. The helicopter then descended and struck trees and a marsh.
Personnel Information
The pilot, aged 49, held a commercial helicopter pilot certificate. On May 2, 2000, the pilot was issued an unrestricted second-class medical certificate. On the medical application, the pilot reported 4,000 hours of total flight time. The pilot's logbook was not available for review during the investigation, and the date of the pilot's most recent flight review is unknown.
Aircraft Information
The single-engine, low-skid, full-bubble-canopy, three-seat helicopter, serial number 1698, was manufactured in 1957. It was powered by a 200-horsepower Lycoming VO-435-A1 engine. The aircraft's logbooks were not available for review, and the date of its last annual inspection is unknown.
Meteorological Information
At 1414, an automated weather reporting facility at Fremont Municipal Airport, located 17 nautical miles south-southeast of the accident location, reported wind from 110 degrees at 7 knots, visibility 4 miles in haze, ceiling broken at 1,000 feet and broken at 1,600 feet, temperature 43 degrees Fahrenheit, dew point 37 degrees Fahrenheit, and barometric pressure 30.03 inches of mercury.
Wreckage and Impact Information
The wreckage was located in a wooded marsh in the Manistee National Forest, also known as Tanner's Swamp. Trees within approximately one rotor disk circumference of the helicopter exhibited blade strikes. The helicopter came to rest on its left side. All parts were accounted for at the accident site, and the helicopter was recovered and transported to a hangar for examination. Inspectors from the Federal Aviation Administration and representatives from Scott's Bell 47 attended the examination. The main rotor blades were fractured a few feet from the rotor mast, with corresponding impact damage to the leading edges. The flight controls were fractured in several locations but exhibited no preimpact malfunctions. Several engine cooling fan blades had leading-edge damage consistent with the fan being driven at impact. Engine control continuity was established from the controls to the carburetor throttle shaft. The main fuel strainer and carburetor fuel inlet finger screen contained an unmeasured amount of fuel.
Medical and Pathological Information
An autopsy conducted on the pilot by Spectrum Health, Grand Rapids, Michigan, determined the cause of death as blunt force injuries of the chest and abdomen. The manner of death was ruled an accident. Forensic toxicology performed on specimens from the pilot by the FAA Bioaeronautical Sciences Research Laboratory tested negative for carbon monoxide, ethanol, and drugs.
Additional Information
Scott's Bell 47 representatives provided information regarding Bell 47 flight characteristics. They noted that a characteristic of the Bell 47 is a best power-to-airspeed combination encountered in level flight at 45 miles per hour indicated airspeed (IAS). This characteristic is often demonstrated in flight training and can be validated: in level flight at 45 MPH IAS, increasing or decreasing airspeed by cyclic input alone results in loss of altitude. Therefore, pilots must be mindful of airspeed and power when maneuvering at low level and reduced airspeed. Since 45 MPH is the best power/airspeed combination and also the target airspeed for best autorotational descent, it is considered the best and safest airspeed for low-level observation and reconnaissance flight. When turning downwind from stabilized flight into wind at 45 MPH IAS, if no control input is made, the turn into downwind will result in reduced airspeed, and the aircraft will tend to settle. This settling tendency is avoided by coordinated management of increased power and airspeed control to maintain altitude.