HISTORY OF FLIGHT: On May 16, 1993, about 0235 hours Pacific daylight time, a Piper PA 28 161, N26075, collided with trees during a go around near Grass Valley, California. The airplane was destroyed during the impact sequence and by the post impact fire. The certificated private pilot and one passenger received serious injuries and the two remaining passengers received fatal injuries. The airplane was rented by the pilot from the operator, Navajo Aviation, Concord, California, for the personal flight. The flight departed Tracy, California, about 0145 hours and was destined for Georgetown, California. Visual meteorological conditions prevailed and a flight plan was not filed. In his written statement and his oral statement provided to a Deputy from the Nevada County, California, Sheriff's Department, the pilot said he and his three passengers departed Tracy about 0145 hours May 16, 1993. The pilot said he and his passengers, all of whom were family members, intended to fly to Georgetown for a weekend camping trip. In his written statement, the pilot said that while enroute from Tracy to Georgetown, "I became disoriented." He said his last known checkpoint was west of Placerville (California) Airport. He reported that as he approached what he thought was Georgetown, he activated the pilot controlled runway lights at the airport. He said that he noted that the runway direction was not correct for Georgetown. He reported that he rechecked his position using the airplane's navigational equipment. He stated: "I proceeded to Nevada County Airport thinking it was Georgetown." The pilot again stated that the runway alignment "seemed wrong." The pilot said that he decided to land so that he could reevaluate the accuracy of his navigation log. During the landing descent, the pilot said he examined his aeronautical sectional chart and realized he was at Nevada County Airport. He said he decided to continue his landing. He said that on "late final approach, I noted that I was too high." He also said he noted that his pilot's guide indicated the runway at Nevada County Airport was not flat. He said he decided to abort the landing and perform a go around. The pilot said he increased to full power and he could not get a positive rate of climb. He said he pointed the nose of the airplane down to gain airspeed. He said he was concerned about losing additional altitude. He said he thought he got "one notch" of flaps out during the go around. He said that after clearing the airport "I turned left to avoid rising terrain. Shortly after (the) turn, plane still would not climb and crashed into trees." The airplane collided with trees and caught on fire about 3/4 mile northeast of the eastern end of the Nevada County Airport. The pilot and one passenger were removed from the immediate vicinity of the burning airplane by witnesses who were located near the accident site in their respective houses. The intended destination of the flight, Georgetown, is about twenty five nautical miles south of the accident site. The accident location is about thirty nine degrees and 12 minutes north latitude and one hundred and twenty degrees and 59 minutes west longitude. CREW INFORMATION: The pilot reported he had a total of about 172 hours of aeronautical experience at the time of the accident. He also told the Deputy from the Nevada County Sheriff's Office that he flew about once a week. A review of the pilot's records indicated he was current for the flight in accordance with applicable Federal Aviation Regulations. AIRCRAFT INFORMATION: The airplane's maintenance records and logbooks were obtained from the operator. A review of the records and logbooks did not reveal any unresolved maintenance discrepancies documented against the aircraft prior to departure the day of the accident. The last annual inspection was performed on the airplane on April 22, 1993. At the completion of the inspection, the airplane had accumulated a total time of 6,860 hours. The operator estimated that the airplane had a total time of 6,900 hours and had been flown for 40 hours since its last annual inspection. METEOROLOGICAL INFORMATION: The closest weather observation and reporting facility to the accident site is at Beale Air Force Base, which is located about 27 nautical miles southwest of the accident site. A weather observation was taken at Beale Air Force Base at 0155 hours. That observation, in part, was: "visual meteorological conditions; scattered clouds at 20,000 feet above ground level; no reported ceiling; visibility 10.0 statute miles; temperature 61 degrees fahrenheit; dewpoint 55 degrees fahrenheit; altimeter setting 29.87 inches of mercury; and calm winds." The pilot reported the light condition as "dark night." WRECKAGE AND IMPACT INFORMATION: The accident site is located about 3/4 mile northeast of the eastern end of the Nevada County Airport in Grass Valley. The accident site is in a forested residential area. The trees in the vicinity of the accident measure about 75 feet in height. The first noted airplane debris and damaged trees were located about 450 feet from the main wreckage on a magnetic bearing of about 160 degrees. Pieces of airplane skin; portions of red plexiglass; and broken tree tops were found at that location. The main wreckage, consisting of the fuselage, portions of both wings, and the engine were located about 450 feet from the first noted point of impact on a magnetic bearing of about 340 degrees. The main wreckage was found on top of a downed tree. The tree measured 42 feet from its root to its broken top. The top of the tree had slash marks and was "cut" about half way through its diameter. The main wreckage had fire damage. The fire consumed the fuselage and most of the airplane's skin. Portions of the right wing were not consumed by the fire. The area surrounding the main wreckage, including the downed tree, had fire damage. The airplane's horizontal stabilator was located in a tree about 40 feet above the ground about 50 feet from the main wreckage on a magnetic bearing of about 340 degrees. The airplane's nosegear was located about 180 feet from the main wreckage on a magnetic bearing of about 150 degrees. Pieces of clear plexiglass were located between the main wreckage and the nosegear. Control continuity for the airframe could not be established due to damage. The airplane's manual flap handle was located. The handle position was in the flaps fully retracted position. The engine was examined on site. All eight spark plugs were removed and visually examined. All spark plugs electrodes were dry and visually appeared to be worn when compared to the "Champion Check A Plug" chart. The carburetor lower housing was consumed by fire. The throttle lever was in the full position and the mixture was in the full rich position. The air box was consumed by fire. Valve and gear train continuity was established during partial hand crankshaft rotation. Gear train continuity was observed by the movement on the tachometer drive. All four valve covers were removed and all components were found to be intact. Lubrication was present. Both propeller blades had aft bending and "s" twists. Both propeller blades had leading edge damage. MEDICAL AND PATHOLOGICAL INFORMATION: An autopsy was performed on the two fatally injured passengers in Nevada City, California, by Dr. Joseph T. Tripoli, M. D., Pathologist for Nevada County on May 17, 1993. The cause of death for both passengers as listed on the report of autopsy was "Complications of Conflagration." During the interview conducted by a Deputy from the Nevada County Sheriff's Office at the hospital, the pilot said he was taking medication for high blood pressure. The pilot said he was taking "Tenormin" and "HCL STZT." A verbal interview was conducted with Dr. Steve Veronneau, M. D., FAA Civil Aeromedical Institute concerning the pilot's medications. Dr. Veronneau said the medications would not prevent an airman from obtaining a Class II or a Class III medical certificate. A toxicological examination was performed on blood samples from the pilot at the Sierra Nevada Memorial Hospital in Nevada City. Negative results were reported for all screened drugs and volatiles. ADDITIONAL INFORMATION: The airplane wreckage was released to Mr. Ken Steiner, representing the owner, on May 17, 1993.