ERA09LA477

Failure of the propeller speed reduction gearbox for undetermined reasons. Contributing to the accident was the pilot’s decision to disregard the manufacturer's mandate to replace the gearbox, the manufacturer's failure to provide owners with technical substantiation for the replacement, and the pilot's decision to overfly several suitable off-field landing sites in an attempt to glide to a distant airport.

The owner/pilot reported that, at an altitude of about 4,000 feet in his experimental amateur-built airplane equipped with a non-certificated propeller speed reduction unit (PSRU) gearbox, he heard a loud "bang." Although the engine continued to run normally and the pilot could control the engine rpm, the pilot determined that he was no longer obtaining thrust from the propeller. In his attempt to glide to an airport about 13 miles from the failure location, the pilot overflew multiple fields and sections of roadway that were suitable for an off-field landing. The airplane struck trees 3 miles short of the intended airport, and the pilot was seriously injured. Postaccident examination revealed that the PSRU gearbox had failed catastrophically, with the result that the engine was unable to transmit power to the propeller. Investigation revealed that the accident PSRU gearbox was the manufacturer's first generation version, referred to as "Gen-I." At the time of the accident, third-generation "Gen-III" gearboxes were current, and the manufacturer had previously determined and notified owners that replacement with the Gen-III version was mandatory. The pilot was aware of the manufacturer's mandate regarding the gearbox replacement, but based on cost and time-in-service reasons, he decided not to replace his Gen-I gearbox. While the gearbox manufacturer "mandated" that owners replace their previous model gearboxes, and his published information clearly stated that he had safety concerns about the previous model gearboxes, he was actually unable to force them to replace the gearboxes. Since the manufacturer did not provide the gearbox owners with substantiating data such as failure rates, time in service, or a catalog of failure events, gearbox owners could have concluded that the manufacturer's mandate was motivated by economic, instead of safety, reasons.

HISTORY OF FLIGHT On August 23, 2009, about 1305 central daylight time, an experimental, amateur-built Vollenweider/Hurst Van's RV-9A, N362TS, was substantially damaged during a forced landing near Marianna Municipal Airport (MAI), Marianna, Florida. The certificated private pilot/owner was seriously injured. The flight was operated under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight. According to the pilot, he based the airplane at Tri-County Airport (1J0), Bonifay, Florida. The pilot departed 1J0, with no particular destination in mind, and was in a "cruise-climb" passing through an altitude of about 3,500 feet when he heard a "bang." Although the engine continued to run normally, and the pilot could control the engine rpm, he determined that he was no longer obtaining thrust from the propeller, and that he could not control the propeller rpm. When the airplane was approximately 10 miles west of MAI, the pilot reported on the airport's common traffic advisory frequency (CTAF) that he was having engine problems, and that he intended to make a straight in approach for landing on runway 8. He did not switch his transponder code from 1200 to alert air traffic facilities to his problem. When the airplane was approximately 5 miles west of MAI, the pilot realized that he would not be able to reach the airport, and advised an attendant at MAI that he was going to make an off-airport landing. The airplane struck trees, and came to rest in a swamp approximately 3 miles west of MAI. The MAI attendant notified the operators of an emergency medical services helicopter that was stationed at MAI about the accident, and the operators initiated an airborne search for the accident airplane. They located the airplane about 1 hour after the accident, but due to the terrain conditions, the helicopter was unable to land at the accident site. The helicopter personnel then directed law enforcement personnel on foot to the accident site. When the law enforcement personnel reached the airplane, the pilot was still in the airplane, and he told them that he had no feeling below his waist. A military emergency medical services helicopter from the U.S. Army facility at Ft. Rucker, Alabama was summoned, and the pilot was subsequently evacuated via a basket lowered from the military helicopter. PERSONNEL INFORMATION According to Federal Aviation Administration (FAA) information, the pilot, age 65, held a private pilot certificate with a rating for airplane single engine land, and an experimental aircraft repairman certificate for the accident airplane. His most recent FAA third-class medical certificate was issued in July 2007 with restrictions for corrective lenses for near and distant vision. AIRCRAFT INFORMATION According to FAA records, the RV-9A airplane was issued its airworthiness certificate in 2005, when it was owned by the pilot and a co-owner. The airplane was a two-place, all-metal, low-wing design with tricycle-configuration landing gear, and was equipped with an "Eggenfellner 2.5 S" engine, which was a modified Subaru automobile engine. The engine was a four-cylinder liquid-cooled model, with a belt-driven supercharger, and a wastegate that was both manually and automatically controllable. A non-certificated propeller speed reduction unit (PSRU) gearbox was used to drive the propeller at a speed slower than the engine speed. Like the engine, the PSRU was marketed and sold by the Eggenfellner Aviation. The propeller assembly consisted of a Quinti-Avio brand hub, and three electrically-controlled, variable-pitch Warp Drive brand blades. METEOROLOGICAL INFORMATION The 1253 weather observation at MAI included wind from 280 degrees at 9 knots, 10 miles visibility, few clouds at 4,800 feet, scattered clouds at 6,000 feet, temperature 28 degrees C, dew point 16 degrees C, and an altimeter setting of 29.95 inches of mercury. AIRPORT INFORMATION MAI was equipped with two paved runways, 8/26 and 18/36. Each measured 4,895 feet by 100 feet, and the airport elevation was 109 feet above mean sea level. There was no air traffic control tower at the airport. The radio communications equipment at MAI had no provisions for recording the communications between the station and aircraft on the CTAF frequency. WRECKAGE AND IMPACT INFORMATION According to information provided by the FAA inspector who responded to the scene, the accident site was a heavily wooded, swampy area. The inspector stated that the tree damage indicated that the airplane struck the forest canopy approximately 60 feet above the ground, and then traversed only a very short horizontal distance before it descended nearly vertically to the ground. The airplane remained essentially in one piece, and the FAA inspector reported that all debris was located within about 15 feet of the airplane. The airplane sustained crush damage in the aft direction to the left wing and right horizontal stabilizer, and crush damage in the up and aft directions to the cowl, engine, and nose and main landing gear. In addition, the fuselage was fractured across the top, and down both sides, just aft of the cockpit. The engine remained attached to its mount at all attach points, and the hub and PSRU remained attached to the engine. All three composite propeller blades were fracture-separated from the hub. Two blades were separated at the hub, and one was fractured approximately 18 inches from the hub. The propeller and hub assembly was able to be rotated freely by hand, with no discernible resistance from the PSRU or the engine. There was no fire. A handheld Garmin GPSMap 296 global positioning system (GPS) unit was recovered from the wreckage, and retained by the National Transportation Safety Board (NTSB) for data download. ADDITIONAL INFORMATION Airplane Glide Performance A representative of the airplane kit manufacturer (Vans) stated that due to the variability of airplane/engine/propeller combinations, as well as individual variations in airplane and component configurations, the kit manufacturer did not provide kit builders with a template for an RV-9A pilots operating handbook (POH). The kit manufacturer also did not provide kit builders with information regarding glide performance, such as best glide speed, or nominal glide ratio. Review of exemplar RV-9A POHs found on the internet indicated that while some included glide performance information, the information appeared inconsistent, even within each POH. For example, the "Emergency Procedures" section of one POH listed a "maximum glide" speed of 80 knots, but the glide performance chart in the same POH cited an airspeed of 75 knots. A non-profit educational organization known as the Comparative Aircraft Flight Efficiency (CAFE) Foundation conducted flight tests, and produced corresponding aircraft performance reports, for a number of amateur-built airplanes. According to the CAFE website, the tests and reports were sponsored and funded by the Experimental Aircraft Association (EAA). The CAFE report for the RV-9A listed a power-off minimum sink rate of 664 feet per minute (fpm) for the conditions tested, which included an airspeed of approximately 82 mph (71 knots). The report cited a best glide ratio of 12 to 1, which was achieved at an airspeed of 95 mph (82 knots). GPS-Derived Flight Data The pilot's handheld Garmin GPSMap 296 global positioning system unit was sent to the NTSB recorders laboratory, and data from the accident flight was successfully downloaded. The takeoff roll to the south from 1J0 began about 1251, followed by a climbing gradual turn to the east. About 1258, the GPS-derived ground speed and altitude data both indicated decreases, and subsequent GPS data indicated that the airplane continued to descend and decelerate, which was consistent with a loss of propeller thrust.