LAX00LA036

The pilot was attempting a short field landing and allowed the airspeed to dissipate too soon. The airplane entered a stall/mush condition and landed hard. The force of the landing bent the engine mounts and broke the wings. The pilot reported that he had not experienced any mechanical problems with the aircraft. The airplane was equipped with vortex generators on the wings and vertical stabilizer, which, according to the STC developer, reduces the stall, approach and Vmca airspeeds by at least 10 knots. The various reference speed reductions were never approved for inclusion as a supplement to the Pilot's Operating Handbook (POH). The STC developer said that pilots were supposed to use the original speeds and limitations in the POH. The pilot said he was using an approach speed derived from a sales brochure from the STC maker. The pilot stated that the accident could have been prevented by maintaining 'greater speed.'

On November 18, 1999, at 1640 hours Pacific standard time, a Beech 95-B55, N550RT, landed hard and bounced several times before running off the end of the runway at the Petaluma Municipal Airport, Petaluma, California. The airplane, owned and operated by the pilot, sustained substantial damage. The commercial pilot and passenger were not injured. The local area personal flight, conducted under the provisions of 14 CFR Part 91, had originated at the Santa Rosa, California, airport, at 1615, and was en route to Petaluma. Visual meteorological conditions prevailed and no flight plan was filed.

The pilot reported that he was attempting to perform a short field landing to runway 11. He stated that he allowed the airspeed to dissipate too soon and the airplane dropped to the runway and bounced twice before he was able to recover. The stall-warning indicator had not enunciated. The propeller blades and engine mounts were bent and the wings had separated from the fuselage.

The pilot reported that he had not experienced any mechanical problems with the aircraft prior to the accident. He stated that the accident could have been prevented by maintaining "greater speed."

A Federal Aviation Administration (FAA) inspector from the Oakland Flight Standards District Office inspected the aircraft after the accident. He tested the stall indicator warning system and reported that it functioned normally.

The aircraft was equipped with vortex generators. The supplemental type certificate (STC) and the micro vortex generator kit installation manual were reviewed. The kit consisted of 106 vortex generators mounted on the wings, just aft of the boot line and on both sides of the rudder, plus two strakes on the outside of the engine nacelles. The manufacturer reported that the vortex generators had been shown "to substantially reduce stall speeds and Vmca, and to improve stall characteristics." However, they further stated that no flight manual supplement was developed for this specific STC (#SA5789NM), therefore, the original speeds, limitations, and performance data listed in the pilot's operating handbook (POH) were to be used in order to provide an increased margin of safety.

The pilot reported that he used the vortex generator manufacturer's (reduced) speeds he obtained from a sales brochure as his reference airspeeds during the approach, instead of the airspeeds indicated in the POH.