Colorado Aviation Accidents & Incidents

On September 8, 2002, approximately 0930 mountain daylight time, an Adler SA-1 gyroplane, N551SA, registered to and operated by the pilot, was destroyed when it impacted terrain and burned near Mead, Colorado. The private pilot was fatally injured. Day visual meteorological conditions prevailed, and no flight plan had been filed for the personal flight being conducted under Title 14 CFR Part 91. The local flight originated approximately 0900 from the Jefferson County (Jeffco) Airport, Broomfield, Colorado.

Two witnesses told a sheriff's deputy that the gyroplane sounded as if it was "struggling." Two other witnesses submitted written statements. One witness said that he "could tell the aircraft was having mechanical problems." The gyroplane dropped about 1,000 feet, "lost a wing" and began to "spin and tumble out of control." Another witness said he heard the engine either "miss or stall slightly," and also saw "a rotor or a wing" come off in flight. All four witnesses saw smoke as the gyroplane impacted terrain and immediately caught fire.

According to the deputy's report, a rotor blade was found about 150 feet north of the point of impact, and other debris was strewn to the southwest. The impact site was circular in shape, approximately 5 to 6 meters (16 to 20 feet) in diameter. The accident occurred 0.25-mile south of (Weld) county road 32 and 0.25-mile west of county road 13, at a location of 40 degrees, 12'48.30" north latitude, and 104 degrees, 57'02.80" west longitude.

The co-builder of the accident gyroplane --- a physician and a close friend of the pilot --- contacted three gyroplane experts: the designer of the SA-1 Dominator and President of Rotor Flight Dynamics; a gyroplane aerodynamist; and the designer of another gyroplane. They examined the wreckage and compiled both a factual and analytical report. The following is based on the factual portion of the report.

The separated rotor blade was bowed upward and had fractured about 2 feet from the tip. The fracture was consistent with positive overload. There was orange paint and primer transfer marks on the top and upper leading edge (the tail and nose cones were painted orange). The attached rotor blade was also bent upward. The propeller blades exhibited no strike marks. The rotor head and hub bar were intact. The hub bar, normally bent 2.5 degrees upward, was found bent approximately 10 degrees upward. The roll pillow blocks bore evidence of hammering and were mushroomed. The pitch stops were similarly damaged.

The analytical portion of the report noted the necessity of maintaining blade loading at all times in order to maintain main rotor blade rotation. The fractured main rotor blade was "a purely upward bending moment which could only have occurred if the blade rpm had dramatically slowed…If totally unloaded, the blade rpm can deteriorate as fast as 120 rpm/sec." Normal rotor blade rpm is 320 to 400 rpm. If rotor blade rpm were allowed to drop and the velocity of air moving