N788LLSentman Lee H RV-6 · 2007

On March 20, 2010, about 1145 eastern daylight time, a Piper PA-32R-300, N823AG, and an amateur built Sentman RV-6, N788LL, collided in-flight 3 nautical miles (nm) southeast of the Williston Municipal Airport (X60), in Williston, Florida. The PA-32 was registered to ARO Wing LLC and operated by a private pilot; the RV-6 was registered to and operated by a private pilot. The personal flights were operated under the provisions of 14 Code of Federal Regulations (CFR) Part 91. Visual meteorological conditions prevailed and no flight plans were filed. The pilot and passenger of the PA-32 and the pilot of the RV-6 were killed; both airplanes sustained substantial damage. The PA-32 departed Deland Municipal-Sydney H Taylor Field, Deland, Florida, about 1115 with a planned destination of X60. The RV-6 departed the Ocala International-Jim Taylor Field (OCF), Ocala, Florida, about 1135 with a planned destination of X60.

There were no witnesses to the accident; however several local area residents stated that they heard a loud “bang” and subsequently observed pieces of airplane falling out of the sky.

The NTSB received recorded radar data from the United States Air Force for the time and location of the accident. The data included two targets that exhibited flight paths (speeds and courses) that matched the convergent tracks expected from the two airplanes.

Review of the radar data showed two aircraft approaching the accident site from the southeast. The aircraft that was located further north had a functioning transponder operating on code 1200 and was also reporting Mode C altitude data. According to the airplane records, the PA-32 was equipped with a transponder and for purposes of this report is identified as the "transponder-equipped" aircraft. The aircraft to the south did not have a functioning transponder, was not reporting altitude information, and was detected as a primary (“skin paint”) radar target only. According to its maintenance records, the RV-6 was not equipped with a transponder and for purposes of this report is identified as the “primary-only” aircraft. The primary-only aircraft approached the collision site on a true ground track of approximately 328 degrees. The transponder-equipped aircraft approached the collision sight on a true ground track of approximately 294 degrees.

PA-32 Flight Track

The radar flight track for the transponder-equipped airplane consisted of equidistant radar returns from the southeast to the accident site, located 3 nm southeast of the Williston Airport. About 1138, the PA-32 was about 15 nm from the accident site and about 3 nm east of OCF, where the RV-6 departed.

During the next 7 minutes, radar returns disclosed a gradual descent from 5,200 feet to 1,700 feet mean sea level (msl) at a radar-derived ground speed of about 132 knots. The radar track continued on the same heading until about 2 miles prior to impact, where it made a gradual left turn.

RV-6 Flight Track

The radar flight track for the primary-only airplane began upon takeoff from runway 36 at OCF and ended at the accident site. About 1138, the airplane was airborne and shortly thereafter turned left to a northwesterly heading. The airplane's track nearly paralleled the PA-32 track, until about 4 miles prior to impact, where it began a slow right turn, consistent with the pilot beginning to maneuver to enter the downwind leg of the traffic pattern for runway 23 at Williston Airport.

PA-32 Pilot

The pilot of the PA-32, age 59, held a private pilot certificate with airplane single engine land and instrument airplane ratings, which was last updated on May 27, 2009. He additionally held a second-class airman medical certificate issued January 14, 2010, with a restriction that he shall possess glasses for near and intermediate vision. The pilot’s logbook was not recovered. On his most recent medical certificate he reported his total civilian flight hours as 345.

PA-32 Passenger, Right Front Seat

A review of FAA records indicated that the passenger, the spouse of the pilot, did not hold any FAA certificate and had no FAA record of flight time.

RV-6 Pilot

The pilot of the RV-6, age 73, held a private pilot certificate with an airplane single engine land rating, which was last updated on May 29, 2008, and a third-class medical certificate issued on May 27, 2008. The pilot’s logbook was not recovered for examination. On the pilot’s most recent medical certificate he reported his total civilian flight hours as 231.

The PA-32 was a red and black painted single-engine, low wing airplane, serial number 32-7780066, manufactured in 1976. It was equipped with a Lycoming IO-540 engine. The maintenance logbooks were not located.

The RV-6 was an unpainted low-wing, amateur built experimental airplane, serial number 002, and was manufactured in 2007. It was powered by an XP360 experimental 180-hp engine and equipped with a Hartzell Model 036081AZ, aluminum variable pitch propeller. The airplane’s engine logbooks revealed that it had undergone an annual inspection in October 2009, at a total time in service of 74.3 hours.

A review of recorded data from the OCF Automatic Weather Observing Station (AWOS), elevation 90 feet and located about 16.5 nautical miles southeast of the destination airport, revealed that at 1135, conditions were winds 110 degrees at 4 knots, visibility 10 statute miles, clear of clouds, and altimeter 30.13 inches of mercury.

According to the United States Naval Observatory astronomical data, around the time of the accident, the sun was 50 degrees above the horizon on an azimuth of 135 degrees.

No FAA facility recorded any communications with either of the accident airplanes during the 15-minute period prior to the accident. X60 management reported that the airport does not record communications on the common traffic advisory (UNICOM) frequency, 122.8 MHz. It is unknown if the pilots were in communication with one another.

X60 is managed by the City of Williston and is open to the public. As published in the FAA's "Airport/Facility Directory," the airport's elevation is 76 feet msl. Runway 23 is 6,668 feet long and uses a left-hand pattern. The airport is uncontrolled.

The airplanes' wreckages came to rest with 100 yards of one another and were about 3 nm southeast of the destination airport. The majority of the RV-6 debris was located in a pasture along with the left outboard wing section of the PA-32. The PA-32 fuselage came to rest inverted in a heavily wooded area, on a heading of 204-degrees magnetic; a postimpact fire ignited the forward fuselage section and surrounding terrain, and a postcrash fire consumed a majority of the fuselage and engine. The tail section was located in an adjacent tree, and the mostly complete stabilator assembly was approximately 35 feet away from the main wreckage and out of the burn zone. The RV-6 came to rest upright, in an open field, on a heading of 090-degrees magnetic. The landing gear collapsed, the wings and empennage were deformed, and the engine was partially imbedded into the ground.

The complete examination report is contained in the public docket for this accident.

Examination of the PA-32 revealed that the vertical fin remained attached to the aft fuselage area and was wedged in a tree forward of the main impact site. The aft fuselage was breached with its sidewalls shredded and separated at the rivet lines. It had separated from the center fuselage section at the aft cargo door jamb. The aft cargo door, aft cabin door, forward cabin door, and the forward baggage door were identified and found to be impact and fire damaged.

The right fuselage side walls and flooring at the forward cabin area were destroyed by postimpact ground fire as was the firewall and engine, which was partially attached to the airframe. The cockpit instrument panel and all of the instruments and radios were destroyed by impact forces and the ground fire.

Complete control continuity could not be verified due to impact and post impact fire damage. The rudder stops were in place and no bending or hammering condition was noted. The outboard 7 feet and 8 inches of the left wing, including the aileron, was separated from the inboard wing structure. This section exhibited what appeared to be leading edge prop strike damage that angled through the outboard fuel tank and proceeded through the main spar at an approximate 45-degree angle. The inboard bay section between the fuel tanks was separated from the wing. The remaining 7 feet of wing spar remained attached to the airframe segment and had sustained fire damage.

The left aileron was attached at its inboard and outboard hinge points; the balance weight was present. The aileron skin was torn at an approximate 45-degree angle from the tip proceeding inboard for about 23 inches and from that point to the inboard end. The aileron exhibited a bowed condition. The fiberglass tip was separated at the landing light lens going inboard and aft for 36 inches at a 45-degree angle consistent with a propeller strike. The left flap was separated from the wing, and exhibited post impact ground fire damage at the tip section along with leading edge impact damage with a bending condition along the inboard section to the outboard section.

The right wing was detached from the fuselage wreckage with the inboard thru outboard sections exhibiting impact and post impact fire damage. The last 27 inches of the outboard wing was separated and exhibited aft crush damage with the leading edge skin "accordioned". The inboard and outboard fuel tanks were breached and exhibited post impact fire damage.

The ventral fin was attached to the fuselage by its forward attach plate only. The fin leading edge had a concave condition on its right side leading edge. The lower aft left side skin was breached at its aft spar bottom rivet line. The fin cap and strobe light were in place. The stabilator assembly was separated from the airframe with the aft bulkhead attached. The bulkhead was impact damaged. The top right stabilator skin was dented and creased 36 inches from the root. The outboard leading edge skin was breached at its rivet line.

The RV-6 came to rest on a 090-degree magnetic heading with both propeller blades and the forward portion of the lower engine imbedded into the ground about 6-inches. The right side of the cockpit wall was pushed inward into the cockpit with red and black paint transfer marks visible on the right side of the pilot's glare shield. The cockpit canopy was separated from the cockpit and the Plexiglas was shattered and spread over the debris path; several shards were observed with red paint marks on them. Control cable continuity was established for all of the flight controls. The instrument panel was separated from the cockpit and located about 200 yards south of the main wreckage.

The left wing remained attached and was observed displaced upwards from the outboard leading edge, to the flap attachment. The right wing remained attached and was observed displaced upwards from the outboard leading edge, to the flap attachment.

The right side of the vertical stabilizer and rudder were impact damaged and separated. The separated portion of the vertical stabilizer was matched to the crushed left horizontal stabilizer of the PA-32, which appeared to be consistent with contact.

PA-32 Pilot

The Medical Examiner District 8 in Gainesville, Florida performed an autopsy on the PA-32 pilot. The FAA Civil Aeromedical Institute (CAMI) performed toxicological screenings on the pilot. The toxicological findings were negative for carbon monoxide and cyanide. Trace amounts of Ethanol were detected in blood and muscle samples, with a notation that the source was other than that of ingestion. Diphenhydramine was detected in liver samples and 0.268 (ug/ml, ug/g) was detected in blood samples.

RV-6 Pilot

The Medical Examiner District 8 additionally performed an autopsy on the RV-6 pilot. CAMI performed toxicological screenings on the pilot which were negative for carbon monoxide, cyanide, volatiles and tested drugs.

Airplane Contact Examination

All of the airplanes' wreckage was recovered from the accident site, and an examination for contact signature evidence between the airplanes was accomplished. Evidence was observed of an intrusion by the propeller of the RV-6 into the left wing of the PA-32.

Laceration signatures consistent with propeller blade penetration marks were observed on the upper portion of the PA-32's left wing. The angle of the cut skin was about 44 degrees, as measured from the airplane's longitudinal axis. The propeller blades on the RV-6 contained numerous gouges that were consistent with impact with the PA-32’s wing.

Based upon the orientation of the penetration evidence, the respective collision and convergence angles were calculated.

Collision and Convergence Angles

The collision (impact) angle describes the angle between the airplanes at impact. For example, if one airplane is on a 90 degrees (east) flight track when a collision occurs with an airplane that is on a 360 degrees (north) flight track, the collision angle would be 090 degrees.

Another angle, called the convergence angle, describes the relationship (in degrees left or right) between the airplane's heading and the location of the converging airplane. The convergence angle represents how far left or right the pilot would have to look to see the other airplane. In essence, it is the relative bearing from a forward-looking pilot to the converging airplane.

Radar Data and Calculated Collision and Convergence Angles

The last portion of recorded radar hits of the RV-6 and PA-32 indicated that airplanes were converging on respective true courses of about 328 and 294 degrees. Based upon this radar data, the expected collision angle was calculated to be about 34 degrees (328 - 294 degrees). Also, based on the radar data, the convergence angles were calculated to be 70 degrees right (RV-6) and 76 degrees left (PA-32). A visual diagram is contained in the public docket for this accident.

Measured Collision and Convergence Angles

The collision angle between the airplanes was physically determined by measuring the mass intrusion signature of the RV-6's propeller blade into the left wing of the PA-32. This signature corresponds to a collision angle of about 44 degrees. Based on this measurement and radar derived ground speeds, the RV-6's convergence angle was calculated to be about 66 degrees right and the PA-32's was 70 degrees left.