On December 26, 2007, about 1558 Alaska standard time, a Piper PA-22-150 airplane, N7637D, sustained substantial damage during a forced landing following a reported loss of engine power while on approach to the Bradley Sky-Ranch Airport, North Pole, Alaska. The certificated flight instructor and the student pilot/airplane owner were not injured. The airplane was being operated as a visual flight rules (VFR) instructional flight under Title 14, CFR Part 91 when the accident occurred. Visual meteorological conditions prevailed at the time of the accident, and a VFR flight plan was in effect. The flight originated at the Fairbanks International Airport, Fairbanks, Alaska, about 1542. During a telephone conversation with the National Transportation Safety Board investigator-in-charge on January 29, the flight instructor reported that while on approach to runway 33, an unlighted, snow-covered gravel runway, he instructed the student pilot to go-around when he realized that the airplane was not lined up with the runway. He said that the student pilot followed his verbal command by immediately applying full engine throttle, but the engine did not respond. The instructor said that he then took control of the airplane, confirmed that the throttle was maximum, then pulled aft on the control yoke to cushion the landing on the snow-covered terrain. He said that when the main and nose wheels touched deep snow, the airplane decelerated rapidly, and the nose landing gear collapsed. The airplane sustained substantial damage to the fuselage and wings. The accident occurred during the hours of sunset, which began at 1444. Civil twilight for North Pole ended at 1608, or 10 minutes after the accident occurred. A Federal Aviation Administration (FAA) airworthiness inspector from the Fairbanks Flight Standards District Office (FSDO) responded to the accident scene shortly after the accident, and examined the airplane prior to recovery efforts. The inspector reported that during his inspection of the airplane, he noticed a placard on the airplane's instrument panel, mounted just above the engine throttle that said: "2 second delay, advance throttle slowly." In the flight instructor's written statement to the NTSB he noted that either carburetor icing, or an incorrect fuel mixture adjustment may have contributed to the loss of engine power. After the airplane was recovered from the accident site, the FAA inspector reported that throughout his postaccident inspection of the airplane he discovered a number of maintenance deficiencies, but found none that would have accounted for the loss of engine power. The closest weather observation facility is Fairbanks, which is 12 miles west of the accident site. On December 26, 2007, at 1553, an Aviation Routine Weather Report (METAR) was reporting, in part: Wind, 040 degrees at 4 knots; Visibility, 10 miles; ceiling, 4,100 feet broken; temperature, 0 degrees F; dew point, minus 8 degrees F; altimeter, 29.93 inHg.