ERA14LA004

The pilot reported that, while in the traffic pattern at his home airport practicing touch-and-go landings, the experimental, amateur-built airplane experienced a complete loss of thrust from the propeller. While turning from the crosswind leg of the traffic pattern onto the downwind leg of the traffic pattern, the engine suddenly "overreved." The pilot reduced power and chose to perform an emergency landing. He then tried adding power, but the propeller did not respond and was windmilling. He established best glide speed, but the airplane had developed a high sink rate and was losing altitude rapidly. He then slowed the airplane as it approached a set of powerlines. The airplane clipped one of the powerlines, which nearly severed the left wing. The pilot then "stalled" the airplane and touched down hard. The airplane was substantially damaged during the forced landing. Examination of the engine revealed that a belt-driven propeller speed reduction unit (PSRU) was installed. Further examination revealed that both drive belts from the PSRU were broken into several pieces, and shredded material from the belts was present throughout the engine compartment. Small pieces of rubber were also present on the forward part of the engine, the propeller hub assembly, and the PSRU pulleys' grooves. Examination of the broken belts revealed jagged belt fractures and evidence of overheating, hardening, back cracks, land area wear, and "V" rib wear, all of which is indicative of inadequate belt tension, which can cause the belts to slip as they travel around the pulleys and generate heat buildup. The heat buildup can cause the rubber compounds in the belt to break down and crack and lead to a belt failure. According to maintenance records, the drive belts for the PSRU had been replaced about 20 hours of operation before the accident flight.

According to FAA and maintenance records, the airplane received its special airworthiness certificate on July 3, 2012. The airplane's most recent conditional inspection was completed on September 10, 2013. At the time of the accident, the airplane had accrued 43 total hours of operation. On October 19, 2013, about 1132 eastern daylight time, an experimental amateur built Zenair 701, N538HB, was substantially damaged during a forced landing, after a loss of engine power, in Zephyrhills, Florida. The sport pilot and his pilot rated passenger were uninjured. Visual meteorological conditions prevailed for the local personal flight conducted under the provisions of Title 14 Code of Federal Regulations Part 91, which departed from Zephyrhills Municipal Airport (ZPH), Zephyrhills, Florida. According to the pilot, the purpose of the flight was to complete phase 1testing to show that the experimental amateur built airplane was in compliance with Federal Aviation Administration requirements that required that it be capable of safe flight. After pulling the airplane out of the hangar he asked another pilot to fly with him and monitor the engine instruments and overall performance of the airplane. After a thorough preflight, he agreed to go with him. After taxiing to the runup area for runway 22, the pilot went through the pretakeoff procedure, and checked for other airplanes that may have been taking off or landing. He then radioed his intention to takeoff, and departed. He climbed the airplane to 1,000 feet above mean sea level (msl) and departed the traffic pattern straight out on the runway heading. After a "few" turns, he established straight and level flight at a power setting of 75 percent of rated power, and then proceeded back to ZPH for some "touch and go" landings. After arriving at ZPH, He made a normal approach to runway 22 at 60 knots, and after touching down, applied full power, lifted off, and established a best rate of climb speed of 60 knots which resulted in a 400 feet per minute rate of climb. He then turned onto the crosswind leg of the traffic pattern, and when he reached 500 feet, announced his intention to do another "touch and go" landing over the radio. A pilot of another airplane then transmitted that he was leaving the airport traffic pattern and asked whether the pilot had his airplane in sight. The pilot responded over the radio that he saw him and that he would extend the crosswind leg of the traffic pattern to make sure that they had "good spacing". The pilot then turned onto the downwind leg of the traffic pattern, and the engine suddenly "overreved". The pilot pulled back the throttle, and picked out an "emergency landing spot". He tried adding power but, the "propeller" did not respond. He was now at 700 feet msl, and he did not have much time to make a decision about the spot he was going to land at. He then slowed the airplane to 55 knots and as he approached a set of power transmission lines. As he came into closeproximity with them, he slowed to 45 knots and attempted to pass under the lines. The airplane however clipped one of the lines, nearly severing the left wing at the wing root. He then "stalled" the airplane, and touched down hard. The recorded weather at ZPH, at 1135, included: winds 180 at 5 knots, 10 miles visibility, overcast at 9,500 feet, temperature 28 degrees C, dew point 21 degrees C, and an altimeter setting of 29.98 inches of mercury. According to Federal Aviation Administration (FAA) and pilot records, the pilot held a sport pilot certificate with ratings for airplane single-engine land. He also held a repairman light sport aircraft certificate. The pilot reported that he had accrued 4,800 total hours of flight experience. The PSRU was installed on the engine to provide a 1.6 to 1 reduction in rpm for the 72 inch diameter, 3-blade, Ivo Propeller. According to maintenance records, the drive belts for the PSRU were replaced during the last conditional inspection at 23.3 total hours of operation on September 10, 2013. The pilot estimated that the airplane had accrued another 20 hours of operation since the inspection. Examination of the broken belts revealed jagged belt fractures, as well as evidence of overheating, hardening, back cracks, land area wear, and "V" rib wear. Examination of the airplane revealed that it had been substantially damaged during the forced landing. The nose landing gear had collapsed, the left wing was impact damaged and partially severed from the airplane, the engine firewall was wrinkled, the empennage was damaged, and the aft fuselage was also wrinkled. Examination of the engine revealed that a belt driven propeller speed reduction unit (PSRU) which utilized two "V" ribbed drive belts was installed. Further examination revealed that both drive belts from the PSRU were broken into several pieces, and shredded material from the belts was present throughout the engine compartment, along with small pieces of rubber on the forward part of the engine, the propeller hub assembly, and the grooves on the pulleys of the PSRU.