NTSB Factual Report

HISTORY OF FLIGHT

On June 24, 2001, about 1605 eastern daylight time, an experimental Bucker-Jungmann Aero Z-131, N4842, registered to and operated by Air South, Inc., collided with trees then the ground during an aerial tow flight near Rupert, Georgia. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 CFR Part 91 glider tow flight. The airplane was substantially damaged and the private-rated pilot, the sole occupant was fatally injured. The flight was originating at the time of the accident.

According to the pilot of the glider being towed, the accident pilot preflighted the accident airplane which the accident pilot reported to him had 1/4 to 1/3 fuel. The wind was from the west-northwest at 5-10 miles per hour (mph) the flight was using the westerly runway. The glider pilot stated, "we lifted off and David accelerated us to about 90 mph in ground effect. While still in ground effect, I saw David drift over to the left side of the runway and hit the top of a small scrub oak that was about 15ft high and 1000 ft before the end of the runway." The glider pilot also reported that the accident pilot set up a normal climb attitude and about 70 mph to about 250 feet above ground level (agl), and at that point, "...we encountered heavy sink/downdraft, with some turbulence which suddenly dropped us about 100ft. Noting this condition, I released the tow rope from the glider and terminated the tow. At this time, I heard the Bucker's engine running and it sounded strong. I then turned right and David continued to drift and turn slightly left which is also where a line of about 100ft pine trees are located about 1000ft from the end of the runway." The glider pilot also stated, "About 10 seconds later, I saw that David was still in a climb attitude and in sink. I saw him appear to release the rope from the Bucker and then clip the top of the tallest tree. He then seemed to snap roll to the left and into the ground." The glider pilot landed on the airstrip and drove to the accident site where he observed that the pilot was conscious. The pilot was airlifted to a hospital in Macon, Georgia, where he died the next day.

PERSONNEL INFORMATION

The pilot was the holder of a third class medical certificate issued on September 29, 1999, with the limitation, "Holder shall possess glasses that correct for near vision." He was the holder of a private pilot certificate with ratings airplane single engine land and glider aero tow only, issued on April 15, 1978.

Review of copies of his pilot logbooks revealed that he logged a "biennial flight review + tow check out" flight lasting 2.0 hours in the accident airplane on May 16, 2001; the entry was signed off by Thomas U. Muller, the president of the corporation that owned and operated the airplane, who was a certified flight instructor (CFI). Excerpts from his pilot logbook is an attachment to this report.

The CFI who last performed a towing checkout on the accident pilot reported in part, "I last flew with him on 5/16/01 over a period of 2 or more flight hours. These flights included a tow checkout including all ground and flight components of FAR 61.69 including reviewing and demonstrating routine and emergency towing procedures and signals, airspeed limitations, and maximum bank angles. This was done during 3 or more towing flights with David as sole manipulator of the controls." A copy of the statement is an attachment to this report.

AIRCRAFT INFORMATION

FAA records indicate Experimental Operating Limitations (EOL) issued on November 5, 1979, states in part that the airplane was, "...certificated for the purpose of exhibition", and, "This aircraft shall not be operated for glider towing or parachute jumping operations." The records also indicate that the airplane was registered in the name Air South, Inc., on July 12, 1994. Review of a copy of the EOL found in the airplane by the FAA inspector-in-charge (IIC) revealed the copy did not list the limitation that the airplane was not to be operated for glider towing or parachute jumping operations. Copies of the EOL that are on file with the FAA in Oklahoma City, OK, and found in the airplane are attachments to this report. The president of the corporation that owned the airplane reported he did not modify the EOL that was found in the airplane. According to the "Operation Manual" the airplane was, "...designed as a plane for teaching beginners and aerobatics." The manual also states, "For pulling gliders there are hooks on the rear end of the plane which enable an easy fastening of the ropes." A record of conversation with and documents provided by the president of Air South, Inc., are attachments to this report.

Review of 14 CFR Part 21.191(d) pertaining to exhibition revealed, "Exhibiting the aircraft's flight capabilities, performance, or unusual characteristics at air shows, motion picture, television, and similar productions, and the maintenance of exhibition flight proficiency, including (for persons exhibiting aircraft) flying to and from such air shows and productions." A copy of the regulation is an attachment to this report.

METEOROLOGICAL INFORMATION

A METAR weather observation taken at the Middle Georgia Regional Airport, at 1553 local, indicates that the wind was from 040 degrees at 5 knots, the visibility was 10 statute miles, and scattered clouds existed at 6,000 feet. The temperature and dew point were approximately 84 and 62 degrees Fahrenheit, respectively, and the altimeter setting was 30.06 inHg.

The pilot in the glider reported that the temperature was between 80 and 85 degrees, the visibility was greater than 5 miles with no restrictions to visibility, and there was no precipitation. He also reported that the wind was from 320 degrees at 5+ mph with gust to 10+ mph; light to moderate turbulence was also reported.

WRECKAGE AND IMPACT INFORMATION

Examination of the accident site by an FAA inspector revealed that the airplane crashed about 500 yards from the end of the grass runway. Damage to the top of a tree at the end of the runway was noted. The airplane was noted to be upright, with the leading edge of the left wing displaced down. Additionally, the left side of the fuselage was resting on the ground. One wooded propeller blade was noted to be fractured. The tow rope was found in the vicinity of the main wreckage and the tow hook was found in the open position. No discrepancies were noted when performing a check of flight control continuity. All components necessary to sustain flight were attached to the airplane. Approximately 4 ounces of what appeared to be 100 low lead fuel were drained from the fuel line attached to the servo fuel injector. The airplane was recovered and a replacement propeller was installed for an attempted engine run. The engine was started and operated to an estimated 1,000 rpm. The FAA inspector noted that the engine would not accelerate which he attributed to impact damage to the throttle body of the servo fuel injector (servo) which was retained for further examination (see Tests and Research section of this report). Both magnetos operated normally. The fuel inlet screen of the servo and the fuel manifold valve were checked; no obstructions were found. A differential compression test was performed with 80 psi as a standard and each cylinder was 72 psi or greater.

MEDICAL AND PATHOLOGICAL INFORMATION

A postmortem examination of the pilot was performed by Krzysztof Podjaski, M.D., Assistant Medical Examiner, Division of Forensic Sciences, Georgia Bureau of Investigation. The cause of death was listed as "Blunt force trauma of torso and extremities."

Toxicological analysis of specimens of the pilot was performed by the FAA Toxicology and Accident Research Laboratory (CAMI). The results of the analysis were negative for carbon monoxide, cyanide, and ethanol in vitreous fluid. Atropine, and Lidocaine were detected in the blood. Lidocaine was also detected in the kidney.

TESTS AND RESEARCH

Examination of the servo, model number RSA-5AD1, serial number 34044, revealed that the mixture control shaft was bent and the mixture control housing was impact damaged. Bench testing was accomplished with the mixture control forced to the full rich position and with the throttle wide open. At "test point No. 4", the unit flowed 118 pounds-per-hour (pph). The "service flow limits" at that test point are 117 to 132.8 pph. With the throttle and mixture positions the same and "test point No. 3", the unit flowed 49 pph. The "service flow limits" at that test point are 46.8 to 53.3 pph. Bench testing also revealed that the regulator was "staying off the seat." Personnel from the facility where the test was performed state that that would only come in play when reducing the throttle. Full throttle application with the mixture full rich revealed no discrepancies with the regulator. Following bench testing, disassembly of the servo revealed no discrepancies with the diaphragms; minimal internal corrosion was noted. A copy of the service flow limits page is an attachment to this report.

ADDITIONAL INFORMATION

The airplane minus the retained servo fuel injector was released to Thomas Muller, President of Air South, Inc., on November 6, 2001. The servo fuel injector was also released to Thomas Muller, on November 20, 2001.

NTSB Probable Cause

The pilot's failure to maintain adequate airspeed which resulted in a stall.