On October 29, 1998, at 0900 central daylight time, a Grumman American AA-5A single engine airplane, N9956U, owned and operated by the pilot under Title 14 CFR Part 91, sustained substantial damage during a forced landing following a total loss of engine power. The private pilot and one of the passengers received minor injuries and the second passenger sustained serious injuries. Visual meteorological conditions prevailed for the personal cross country flight that departed Greenville, Mississippi, at 0800. A flight plan was not filed. During a telephone interview, conducted by the investigator-in-charge (IIC), the pilot reported that the flight departed Greenville with 3 hours of fuel aboard for the planned one hour flight to Little Rock, Arkansas. During the en route descent approximately 10 miles east of the destination airport, the "engine quit." The propeller continued windmilling. The Little Rock Control Tower provided vectors; however, the airplane landed short of the airport. During the landing flare the airplane stalled, bounced, landed on the main landing gear, and subsequently nosed over. The pilot, who had owned the airplane for 5 years, had flown the airplane 13 hours since the last annual inspection with no discrepancies noted. The local authorities and the FAA inspectors responding to the site reported that the airplane came to rest in a bean field after collapsing the nose gear and right main landing gear. Structural damage occurred to the lower engine cowling and fuselage. The left main gear was found separated from the airplane. The propeller blades were bent aft toward the engine cowling and an engine mount was found separated. The cockpit tachometer reading was 1460.63 hours. The FAA inspector's and the engine manufacturer representative's examination and disassembly of the engine at Clinton, Arkansas, revealed a lack of gear train continuity. Disassembly of the engine accessory case revealed that the crankshaft gear lockplate was not installed and the crankshaft gear retaining bolt had backed out of the crankshaft approximately 1 3/4 turns. The crankshaft gear alignment dowel was fractured. The crankshaft gear did not appear to have been modified according to Airworthiness Directive (AD) 91-14-22 and the Textron Lycoming Service Bulletin (SB) No. 475B. The AD and the SB require the crankshaft gear modification during engine overhaul. See the enclosed report for details of the teardown examination. A review of the maintenance records by the IIC did not reveal that the AD or SB had been accomplished. The tachometer reading at the annual inspection on August 20, 1998, was 1,448.4 hours. The aircraft had flown 852 hours since the last engine overhaul in January 1987 and return to service by a FAA certified mechanic.