NTSB Factual Report

On January 23, 2004, at 0953 Pacific standard time, an experimental Cox Thorpe T-18, N64EC, rolled over and impacted terrain while on final approach to the Compton/Woodley Airport, Compton, California. The pilot/owner was operating the airplane under the provisions of 14 CFR Part 91. The private pilot, the sole occupant, sustained fatal injuries; the airplane sustained substantial damage. The personal local flight departed Compton about 0915. Visual meteorological conditions prevailed, and no flight plan had been filed.

A Federal Aviation Administration (FAA) inspector examined the airplane at the accident site and talked to witnesses. A witness, who was also a student pilot, reported seeing the Thorpe execute several practice touch-and-go takeoffs and landings before the accident. The witness looked down runway 25R, and observed the Thorpe on final approach in a landing configuration beginning to flare. A Long Beach Police Department EC-130 helicopter was above the airplane and descending directly in front of it. The Thorpe made an abrupt turn to the right, which the witness thought was an attempt to execute a go-around. The Thorpe flipped inverted and impacted terrain.

Another witness, a certified flight instructor, was flying a Robinson R-22 helicopter in the traffic pattern for runway 25L. He stated that he heard the Thorpe pilot make a radio transmission stating his intentions to land on runway 25R. He then heard a radio transmission from the EC-130 pilot, stating that he was 2 miles east of the airport and intending to execute a straight-in approach runway 25R. The witness obtained visual contact with the Thorpe and opted to complete a 360-degree turn in an effort to gain greater separation. The Thorpe made another radio transmission stating that he was landing on runway 25R.

The witness further stated that after completing his turn, he observed the EC-130 arrive at runway 25R first, with the Thorpe directly below. He noted that the EC-130 and Thorpe were about 100 feet apart, about 8 feet above ground level. He made a radio transmission calling for both pilots to "watch out." Several seconds later, he saw the Thorpe attempt a right turn to avoid the EC-130. While turning, the Thorpe appeared to stall and invert, crashing into the terrain.

During a telephone interview with a National Transportation Safety Board investigator, the EC-130 pilot stated that due to the heavy traffic at Long Beach Airport, he opted to fly over to Compton airport to practice autorotations. Just south of the 91 freeway, he tuned in the radio to the Compton common frequency. He announced that he was on a 2-mile final approach for runway 25R. As he continued on final approach, he noticed an R-22 helicopter in the traffic pattern, where it appeared to be on the downwind for 25L. He announced that he was 1 mile out from runway 25R and intending to execute an autorotation, landing on the runway numbers. Just past the numbers he configured the helicopter into a flare/hover for about 30 seconds, and then maneuvered the helicopter down the runway. At the end of the runway he performed a pedal turn and observed an airplane inverted off the side of the runway, which he thought had crashed while on landing. He further stated that he never saw or heard the Thorpe. He made the approach about 500 feet above ground level.

FAA inspectors examined the wreckage at the accident site, and established control continuity. They estimated that the Thorpe's wing flaps were in the extended position of 30 degrees.

Federal Aviation Regulations state that "when two or more aircraft are approaching an airport for the purpose of landing, the aircraft at the lower altitude has the right of way, but it shall not take advantage of this rule to cut in front of another which is on final approach to land, or to overtake that aircraft." (14 CFR 91.113)

In the FAA Rotorcraft Flying Handbook (FAA-H-8083-21) it states that at multiple use uncontrolled airports, helicopters must try to "avoid the flow of fixed wing traffic."

A review of FAA Advisory Circular (AC) 90-23F, Wake Turbulence, revealed: "A hovering helicopter generates a downwash from its main rotor(s) similar to the "prop wash" of a conventional aircraft. However, in forward flight, this energy is transformed into a pair of strong, high-speed trailing vortices similar to wing-tip vortices of larger fixed-wing aircraft. Pilots should avoid helicopter vortices since helicopter forward flight airspeeds are often very low which generate exceptionally strong wake turbulence." The AC further stated that pilots should avoid operations within distances of three times the rotor diameter of a hovering helicopter.

NTSB Probable Cause

both pilots' failure to see and avoid one another that resulted in the airplane's encounter with downwash induced wake vortices from the helicopter, and the airplane pilot's subsequent loss of control.