On May 12, 2001, about 1700 Pacific daylight time, a Bell 206B single-engine helicopter, N2102Z, and a Gulfstream Aerospace G-IV transport category twin-turbine airplane, N999GP, collided in a non-movement area of the San Diego International-Lindbergh Field, San Diego, California. The helicopter, N2102Z, was operated under the provisions of 14 CFR Part 91 by the pilot/owner, and sustained substantial damage after one of its main rotor blades struck the Gulfstream's right wingtip and then its own tailboom. The commercial helicopter pilot and three passengers were uninjured. The Gulfstream G-IV airplane, N999GP, operated by GEP Incorporated, LLC, under the provisions of 14 CFR Part 91, sustained minor damage to the right winglet. The airline transport pilot, two flight crewmembers, and six passengers were uninjured. N2102Z was parked and preparing to depart on a personal flight to Montgomery Field, San Diego. N999GP was taxiing to parking under the aid and supervision of line service personnel from Jim's Air Service. N999GP had departed from McCarran International, Las Vegas, Nevada, at 1615. The National Transportation Safety Board investigator-in-charge (IIC) interviewed both flight crews. The pilot of N2102Z stated the purpose of the flight was to pickup a friend at Lindbergh Field and then return to Montgomery Field. He stated that he started the engine and saw N999GP coming down the taxiway. He saw the line service personnel motion for N999GP to continue the taxi between his helicopter and another airplane. One of his passengers stated that the two aircraft were going to hit. The pilot stated that he did not believe that the two aircraft were going to hit each other, then the main rotor blade contacted the winglet of N999GP. The pilot stated that he was not in contact with San Diego ground control because he was not ready to takeoff. The captain of N999GP stated that the purpose of the flight was to pickup a passenger and return to Las Vegas. After landing, ground control cleared N999GP to taxi to Jim's Air. There were no further radio communications with ground control; however, the pilots of N999GP monitored the frequency. The manager of Jim's Air Service indicated the ramp area had been busy all day, and as a result, four line service personnel (wing walkers) were used to assist with the parking. At the time the Gulfstream was taxiing into the facility, one wing walker was assigned to each wing, one wing walker was at the nose of the airplane and the last line service person was assisting with the loading of passengers into the helicopter. The captain of the Gulfstream stated he saw passengers being loaded into the helicopter as they approached the ramp, and the helicopter's main rotor blades were not turning. He then saw the main rotor blades turn about three times. He further reported that because the cockpit was past the helicopter when the main rotor blades struck the winglet he did not see the rotor blade strike, but did hear and feel it. The first officer of the Gulfstream stated he was a little concerned with the wing clearance during the taxi, but that the wing walker on the right side had indicated, with a thumbs up signal, they were clear of the helicopter. He kept looking outside to make sure they were clear, and noted passengers were being loaded into the helicopter, and the main rotor blades were not turning. As the cockpit of the Gulfstream passed by the helicopter he saw the main rotor blades begin to turn and then heard a "thump." The wing walker, who was located on the right side of the G-1V, stated he had been notified that a G-IV had landed and needed wing walkers to help taxi it to parking. As he walked out to the ramp area he noted that N2102Z was empty of people. He waited for N999GP to exit the taxiway and enter the ramp area, with his back to N2102Z. He indicated there was about 20 feet to spare, 10-foot clearance of the wings on each side, and felt this was enough room to safely taxi N999GP between the parked aircraft. He further indicated he was standing about 2 feet in front of N2102Z's main rotor blades, which was positioned parallel with the helicopter's longitudinal axis. The wing walker stated that as the cockpit was passing his position he heard the whine of the helicopter engine starting. He turned around and saw a pilot and passengers seated in the helicopter and the main rotor blades starting to turn. He tried to obtain the attention of the helicopter pilot, but was unable to because the pilot's head was down looking inside the cockpit. He then ducked to get out of the way of flying objects. The wing walker indicated he did not see the pilot and passengers of N2102Z enter the cockpit, nor was there any warning that the helicopter pilot was going to start the engine. The wing walker who was attending to the helicopter passengers stated that after the passengers had boarded, the pilot shut the door. The wing walker also saw there was another line service person standing at the nose of the helicopter. As he was moving away from the helicopter he heard the engine start. He stated he was scared because the main rotor blades were turning and he ducked to get out of the way. He further stated he did not see the pilot of N2102Z clear the area before starting the helicopter. According to the San Diego Regional Officer's Report, the helicopter was parked on the ramp with its nose facing north-northwest. The airplane was taxied to the west of the helicopter with its right wing closest to the helicopter. As the airplane turned through an easterly-to-southerly heading, the rotor blade made contact with the wingtip. According to the officer's report, there was 110 feet between the right side of the helicopter and the nose of an unoccupied, parked airplane, which the G-IV was being directed through. The wingspan of the Gulfstream G-IV is 77 feet 10 inches. The Bell 206B rotor disc radius is 17 feet 10 inches. A review of the Federal Aviation Regulations, the Aeronautical Information Manual, and pertinent advisory circulars revealed no guidance is provided to pilots for ramp operations. All of the right-of-way rules and recommendations are provided for in-flight operations, with the exception of FAA Air Traffic Control Order 7110.65, paragraph 3-7-2, note 2, which states, "movement of aircraft or vehicles on non-movement areas is the responsibility of the pilot, the aircraft operator, or the airport management." The movement of aircraft on a ramp area is the responsibility of the pilots, and the ramp personnel directed to marshal the aircraft. According to ramp personnel, the ramp area did not display any taxiway or parking markings, because of the need to accommodate a wide range of aircraft sizes. There was no designated helicopter operation area on the ramp. The ramp personnel did not discuss the ramp traffic with the pilots.