On April 2,1999, about 1557 eastern standard time, a Waco YMF-5, N820MM, registered to MD Aero, Inc., operating as a 14 CFR Part 91 personal flight, crashed in a residential area in Boca Raton, Florida, following an engine failure. Visual meteorological conditions prevailed and no flight plan was filed. The airplane received substantial damage, the private-rated pilot sustained serious injuries, and a passenger sustained minor injuries. The flight originated from Fort Lauderdale's Executive Airport (FXE), about 17 minutes before the accident. According to the pilot, the flight was maneuvering at 500 feet agl, about 1/2 mile off the coast northeast of Boca Raton when the engine and cowling began to shake, the engine began to sputter, and the windscreens became covered with oil. He stated that the engine power available was not enough to sustain level flight, so he set up a slow rate of descent and an immediate turn westbound. He declared an emergency with FAA Pompano Control Tower, told them he would try to make an emergency landing at Boca Raton Airport, and was given the unicom frequency for Boca Raton. He switched to the Boca frequency and raised a young woman's voice who said she would get help. He stated he could hear other aircraft in the traffic pattern stating they would yield to the emergency, but he made no further calls. At about 1543, according to FAA Pompano Control Tower personnel, N820MM called that he just departed FXE eastbound and asked for clearance to transit their area along the beach in a south to north direction. At about 1552, he had reached the northern limit of Pompano's airspace and was cleared for a radio frequency change. At about 1554, Pompano tower heard a Mayday call from N820MM, and at about 1555, the pilot said he had an oil leak and would try to land at the Boca Raton Airport. According to a pilot in the traffic pattern at Boca Raton Airport, when N820MM declared his emergency and stated his engine problem, he obtained a visual on the Waco and watched him proceed westbound from a point about 2 miles east of the airport. It became obvious to the pilot that the Waco pilot and passenger did not or could not see the Boca airport, because they flew "..right over the numbers for runway 23 at Boca, but kept on flying westbound". According to the Boca Raton Police Services Department, the pilot advised them that the airplane "..developed engine problems and was trying to make Boca Raton Airport and was unable to see the runway and overshot the airport and crashed in the field." The airplane collided with trees in a residential area and came to rest inverted. According to FAA inspectors, the airplane crashed about 2 miles west of the Boca Raton Airport, within a residential area. Postcrash examination of the Jacobs radial engine by FAA inspectors revealed the power loss was caused by the failure of the No. 7 cylinder holddown studs and the resultant lifting of the cylinder off its seat. Three of a total of 12 holddown studs, located on the aft side of the cylinder, revealed rust on their fractured surfaces. The remaining studs exhibited overload fractures. Piston wear marks on the walls of No. 7 cylinder reveal tilting of the cylinder away from the studs with rusted fracture sites. The power loss and oil leakage were the result of induction piping and oil line connections being stripped when the cylinder started lifting off its seat. Inspectors reported that the only thing holding No. 7 cylinder on the engine was baffling jammed against the cowl. About 140 engine operating hours before the accident, on March 3, 1998, the engine was reinstalled by General Aviation, Inc. of Lansing, Michigan, after a Jacobs Engine, Inc. factory teardown inspection due to a landing nose over incident.