On March 14, 2009, about 1020 eastern daylight time, an amateur-built Long-EZ, N770EZ, was substantially damaged during a ground fire before takeoff from Manassas Regional Airport (HEF), Manassas, Virginia. The certificated airline transport pilot was not injured. Visual meteorological conditions prevailed, and a visual flight rules air defense identification zone flight plan was filed for the flight. The personal flight, destined for Venango Regional Airport (FKL), Franklin, Pennsylvania, was conducted under the provisions of 14 Code of Federal Regulations Part 91. According to the pilot's written statement and a subsequent interview, during the pre-takeoff engine run-up, he experienced engine roughness upon switching to the right magneto, and attempted to resolve the issue by increasing engine rpm to 2,200 and leaning the fuel mixture. He further stated that the engine ran smoothly on either magneto at 1,700 rpm, but when the rpm was increased to 2,200 and only the right magneto was used, engine roughness occurred. The pilot initially elected to abort the flight, but after he taxied to his hangar tested the magnetos again, and noted no abnormalities. He then decided to taxi the airplane back to the run-up area. As the airplane approached the run-up area, the air traffic controller informed the pilot that his engine was on fire. In response, the pilot shut down the engine, turned off the fuel selector and the electrical master switch, and exited the airplane. Personnel from the local fixed base operator arrived shortly thereafter, and suppressed the fire with a dry chemical extinguishing agent. The local off-airport fire department arrived shortly thereafter, and extinguished the fire with water. The airplane sustained substantial damage to the engine, and portions of the wing that were in close proximity to the engine. According to Federal Aviation Administration (FAA) records, the pilot held an airline transport pilot certificate with ratings for airplane single engine land and multiengine land, and a flight instructor certificate with ratings for airplane single engine, airplane multiengine, and instrument airplane. The pilot had accumulated 3,939 total hours of flight experience, and 187 hours in the accident airplane make and model. His most recent FAA second-class medical certificate was issued on February 15, 2008, with the limitation "must wear corrective lenses." The airplane's most recent condition inspection was completed on December 29, 2008. As of that date, the airplane had accumulated 1,092 total hours of operation. According to the pilot, the accident flight was to be the second one since the condition inspection, and the airplane had accumulated only about 1 flight hour since the inspection. The airplane was of a fiberglass construction and equipped with a Lycoming O-235-C2C engine installed as a pusher configuration. The airplane was examined by a National Transportation Safety Board fire expert on March 18, 2009.The fire damage was limited to the right side of the engine compartment, particularly the forward portion of the compartment. The upper engine cowlings exhibited fire damage and the lower cowling exhibited thermal damage. Portions of the right wing root contained areas where the resin had burned away, so that only the glass fiber remained. There was heavy soot residue over most of the engine surfaces, and thermal damage to many of the engine accessories. The majority of the damage was limited to the right forward side of the engine, just above the exhaust manifold. The oil lines were located in this area, and their fire sleeves were charred. The insulation on the electrical wiring in this area had melted away, and no evidence of arcing was observed. Fuel lines located above the fire-damaged area of the engine compartment were melted through. No obvious pre-fire failures were found during the visual examination. The 0955 weather observation at HEF included calm winds, 7 statute miles visibility, few clouds at 1,000 feet, temperature 3 degrees Celsius (C), dewpoint 0 degrees C, and altimeter setting of 30.35 inches of mercury.