On April 26, 2001, at 0830 mountain daylight time, a Piper PA-39, N8984Y, was substantially damaged during a forced landing after take-off from Fort Collins Downtown Airport (3V5), Fort Collins, Colorado. The commercial pilot and his passenger received serious injuries. Visual meteorological conditions prevailed. No flight plan was filed for this positioning flight being operated under Title 14 CFR Part 91. The flight was originating at the time of the accident with an intended destination of Iowa City, Iowa. According to the pilot, when they arrived in Fort Collins on April 24, he had the aircraft fuel tanks topped off. The Fort Collins Downtown Airport daily fuel record sheet for April 24, 2001, indicated that, N8984Y, received 61.8 gallons of 100 low lead fuel. In the Pilot/Operator Aircraft Accident Report ( NTSB Form 6120.1/2), the pilot stated that take-off was normal, the airplane rotated at 95 mph, and accelerated to 110 mph. During the initial climb, at approximately 150 feet above ground level (agl), the left engine lost power and "quit." The pilot attempted to restart the left engine, but before he could, the right engine lost power and "quit." The pilot made a forced landing in a open field just north of the runway. The airplane struck the ground, slid over a berm and across two railroad tracks, impacted a ditch, struck a power pole, spun 90 degrees to the left, and came to rest on a city street. Witness statements obtained by the Larimer County Sheriff's Office stated that the airplane "appeared to have just taken off" and was flying "extremely low" when it hit the ground, slid across the railroad tracks and came to a stop on the road. According to a Colorado State Patrol Trooper, who arrived at the scene at 0838, emergency personnel were removing the pilot and passenger from the aircraft and preparing to transport them to the hospital. The trooper later interviewed the pilot and passenger at the hospital. The pilot told the trooper that his "right engine" lost power and that he went through "emergency operations," but could not gain altitude. The pilot told the trooper that he could not remember any more since he had hit his head during the crash. The passenger told the trooper that he thought the airplane lost power in the "right engine." On May 9, 2001, a manufacturer's representative from Piper Aircraft examined the airplane and stated that the airplane was properly configured for takeoff. Control continuity was verified to the empennage surfaces. Flap position was not determined. Both fuel selectors were in the "Main" position and "Cross feed" was not selected. Some contamination was found in the fuel filters, but no blockage was noted. The landing gear was in the retracted position. The engine cowl flaps were closed. An examination of the left engine compartment found that the alternate air door was stuck in the open position, corrosion was present on the actuating cable and the cable was broken. Examination of the right engine compartment found that the alternate air door had separated from its pivoting mechanism and stuck in the fuel servo air inlet. No other indications of preimpact anomaly to the fuselage, airframe or flight surfaces were noted. A manufacturer's representative from Textron Lycoming examined the airplane's engines and identified that the left engine exhibited no external damage other than impact damage to the propeller blades. All of the spark plugs were intact and of proper gap. The ignition wires were all attached and a spark was noted at all leads during rotation. Fuel was found in the fuel lines, engine driven fuel pump, fuel servo and nozzles. The fuel inlet screen was clean. An indication of 7 quarts of oil was noted on the dipstick/gauge. The induction system's alternate air valve door control cable end was broken off the cable. The alternate air valve was stuck in the full open/on, (non-filtered air) position. No anomalies were noted on the left engine that would have precluded its operation. The right engine exhibited impact damage to the propeller blades and a hole in the oil sump, allowing all of the oil to drain out of the engine. All of the spark plugs were intact and of proper gap. The ignition wires were all attached and a spark was noted at all leads during rotation. Fuel was found in the fuel lines, engine driven fuel pump, fuel servo and nozzles. The fuel inlet screen was clean. An indication of 0 quarts of oil was noted on the dipstick/gauge. The induction system's alternate air valve door was separated from its mounting rivets and was lodged in the alternate air box, completely covering the inlet on the fuel injector servo. No other anomalies were noted on the right engine that would have precluded its operation. An examination of the remaining fuel in the airplane, and the fuel in the refueling truck, provided no evidence of fuel contamination. Six other aircraft were serviced and refueled the same day with no reported problems. The manufacturer's representative from Textron Lycoming collected a sample of an unknown substance/debris found in the left main fuel tank gascolator, and sent it to SEM-EDAX for spectra-analysis. SEM-EDAX analyzed the substance/debris and identified it as silica sand. Weather at the time of the accident, obtained from Fort Collins/Loveland Airport, located approximately 8 nautical miles at 170 degrees from the accident site was, wind, light and variable; visibility, 10 statute miles; temperature, 9 degrees Celsius; dew point, 3 degrees Celsius, altimeter setting, 30.18. The Fort Collins/Loveland Airport elevation is 5,016 feet mean sea level (msl). The calculated density altitude for Fort Collins/Loveland Airport was 5,244 feet msl. The wreckage was released to Beegles Aircraft Service on May 29, 2001.