On August 23, 1995, approximately 1022 mountain daylight time, a North American T-28A, N9640C, experienced an inflight fire west of Rexburg, Idaho. The airplane was subsequently destroyed, and its private pilot/owner and safety pilot were seriously injured in the forced landing in a field 2 miles west of Rexburg. The flight was to be a local 14 CFR 91 flight out of Rexburg. Visual meteorological conditions existed and no flight plan had been filed. The pilot-in-command reported that during climbout from Rexburg between 2,000 and 3,000 feet above ground level, he began to smell smoke and turned eastward back toward the airport. He stated: "By the time I was going east the cockpit was full of smoke." He opened the canopy approximately six inches to get rid of the smoke, at which point "the smoke was replaced by fire both inside and outside. Then there was an explosion....the top right cowling was blown off. We had shut off the electrical [and] fuel by this time. I had been burned on my face and hands...." He stated that the fire was along the right side of the airplane. He dove the airplane toward "the only open field" for a forced landing; his report stated: "We [could] see ditches and [a] dike, but there were no other options." The pilot then performed a gear-up forced landing into the field. His report stated that during the landing, "the tail skid and prop were all that was touching the ground for the first 135 feet. We then impacted a ditch which put us back in the air[;] we hit nose first[,] tore the engine off and flipped[,] sliding backwards...." The safety pilot, who was riding in the rear seat, did not return a statement to the investigator. Three witnesses who observed the airplane from vantage points on the ground 3 1/2 to 5 miles west of the airport reported hearing one or more "explosions", "sputters" or "backfires." Two stated that they observed the airplane turn to an easterly heading and the third observed the airplane heading east. All three observed the airplane on fire. Two reported the flame as bright yellow, 2 to 3 feet long and coming out of the right side of the engine compartment, trailing gray smoke. The third witness saw fire coming from "the front of the airplane" but stated "as quickly as the fire [occurred], it was extinguished." Two witnesses saw a piece come off the airplane. One witness later recovered this piece, a section of the right side cowling approximately 3 feet square. The witness found the piece on August 28, approximately 3 miles west of the forced landing site. Photographs provided to the investigator-in-charge showed fire damage to the cowling section, sooting on the right side empennage, blackening of the right side of the fuselage in the area immediately aft of the engine cowling, and sooting on the right wing root leading edge. An airframe and powerplant mechanic from Idaho Falls, Idaho, performed a post-accident engine examination for the NTSB investigator-in-charge on August 30, 1995. His report stated: "Found loose fuel fitting on Stromberg Carb - this fitting has a hose connected to it, and Y's to two lines that [connect] to the accelerator jets...." An aviation safety consultant from Accident Investigation & Research Company of Wentzville, Missouri, performed a post- accident examination of the aircraft wreckage at the facilities of the Teton West Construction Company of Rexburg, Idaho, on October 20, 1995. He reported the following from his examination: "The canopy is hydraulically operated from the normal hydraulic system which is energized by an engine driven hydraulic pump. The canopy also incorporates an emergency opening accumulator...for opening the canopy in the event of a hydraulic failure....The emergency accumulator had not been pressurized for this use. The rear seat passenger stated that the canopy would not fully open with the normal system but that he was able to push the canopy rearward with very little resistance using his hands against the leading edge." "The FAA found a small fuel line with a loose fitting....That fuel fitting...was not a fitting from which fuel would normally flow except during engine start. Further, the size of the fitting was such that it was too small to accommodate [sic] for the...volume of material burning in this fire. Examination of the hydraulic lines indicated that several hydraulic lines had burned off...." "The main hydraulic line, which attaches directly to the engine driven hydraulic pump, has a suspicious failure for approximately fifty percent of [its] diameter. This failure appears to be of fatigue origin....there is some brinnelling in the fatigue portion...." "The type of hydraulic fluid, required for this aircraft, (MIL-H- 5605A) is flammable. However, it would not ignite without another significant heat source....the burn pattern was primarily exterior to the engine in the areas adjacent to the exhaust pipes. There was very little fire damage within the engine accessory section itself." "The hydraulic reservoir...was empty during my investigation. It has a capacity of 4.25 gallons."