On January 8, 1994, at 1415 Alaska daylight time, a wheel equipped Cessna 150 airplane, N16037, registered to Bret Anderson and operated by the Anchorage Flying Club of Anchorage, Alaska, experienced a power failure while practicing a simulated engine out procedure. The instructional flight, operating under 14 CFR Part 91, departed Merrill Field, Anchorage, for a local flight. A company flight plan was in effect and visual meteorological conditions prevailed. The Commercially Certificated Instructor Pilot and the Student Pilot were not injured and the airplane was substantially damaged. According to the Instructor Pilot during a telephone interview on January 8, 1994, the Student Pilot was given a simulated forced landing, the first simulated forced landing of the flight. The Instructor applied carburetor heat and reduced the throttle to 1000 RPM. The Student Pilot entered the traffic pattern at the Big Lake Airport intending to land to the east. During this initial interview the Instructor stated that the glide was going to be short of the airport so the Student applied power smoothly and the engine stopped producing power. The Instructor took control of the airplane and completed a forced landing. After touchdown a berm sheared the nose gear off and the airplane nosed over. The airplane landed in a marsh/frozen area on Fish Creek and nosed over. During a subsequent interview on May 19, 1994, the Instructor stated that during the turn from downwind to base, she cleared the engine by applying throttle and increasing the engine RPM into the green arc and then reducing the RPM to 1200 RPM. She stated the Student was not aware of the process of "clearing the engine." The Instructor stated, she knew the glide was going to be short of the runway but allowed the student to continue. At approximately 500 feet she instructed the student to go around. The Student applied power smoothly and the engine did not respond. The Instructor took control of the airplane and reduced the throttle but not to the closed position and then smoothly applied the throttle again. They did not attempt to use the primer to restart the engine. According to a Service Bulletin from Continental Motors Corporation, M50-7, dated October 25, 1950, "...The acceleration problem seems to be most frequently encountered in outside air temperatures of 32 degrees F. and below. When temperatures in this range are encountered, the pilot must use precaution in opening the throttle in flight after the engine has once been idled. If the throttle is opened suddenly and rapidly, transition from the idle system of the carburetor to the power system is so rapid that the engine is temporarily starved of fuel which might cause possible engine stoppage. However, we found in our tests that in every case where engine stoppage resulted for this reason, the engine could be restarted by one of the following procedures. 1. Return the throttle to the closed position and then open it slowly. 2. Leave the throttle in the wide open position and operate the primer for one or two strokes. Our data further indicates that in two minutes after the throttle is closed, with carburetor heat "ON", the carburetor air temperature can drop as much as 72 degrees. This makes it obvious that in extended glides with closed throttle, power should be applied momentarily at frequent intervals in order to supply some heat to the carburetor air heater...." The Instructor pilot was not aware of the existence of this Service Bulletin at the time of the accident. The airplane and engine were examined on January 21, 1994, and the engine was test run. The engine was operated for 20 minutes at 1700 RPM after it was warmed up. The carburetor heat was checked and a 100 RPM drop was notice. There were no mechanical malfunctions noted during the test and examination. During an interview with the Student Pilot, he stated they were in a descent and at 2700 feet MSL the instructor initiated a simulated forced landing by pulling carburetor heat on and reducing the throttle to the idle position. The student pilot selected the surface of a frozen lake but the Instructor told the student to use the airport directly beneath the airplane. The Student entered a wide traffic pattern and was turning a long final when he realized that he would not be able to reach the airport. He told the Instructor and she did not respond. The Student then applied throttle smoothly and the engine did not respond. He alerted the Instructor and she did not take any action. The Student again stated that they would not make the airport and he then made a turn towards a clearing. The Instructor then took control of the airplane and they completed a forced landing. The Student was not able to describe what the Instructor had done with the throttle prior to landing. The Student stated that he did not clear the engine and that the Instructor did not clear the engine and that she did not instruct him to make a go around at any time. He further stated that at the time of the accident he was not informed of any method or requirement to clear the engine during extended engine idle flight conditions. The Student stated that his previous instructor taught him to push the carburetor heat off once he turned onto final approach. He was not able to recall if he pushed the carburetor heat off during this flight but felt it was a distinct possibility. According to Advisory Circular 61-21A, it states "During all simulated forced landings, the instructor should control the throttle, ensure that the engine is kept warm and cleared, and advance the throttle when the simulated forced landing approach is ended. When the throttle is reopened by the instructor after the termination of the approach, no doubt should exist in the student's mind as to who has control of the airplane." Further review of AC 61-21A shows no procedure listed to instruct a pilot in the proper method of "clearing" an engine. A review of the Continental Aircraft Engine Operator's manual for the O-200 series A & C engines states, "If a long glide is made, apply power at short intervals to clear the cylinders and retain engine temperatures in the event that instant power is required." The Continental Aircraft Engine Operator's manual was not available to the Instructor or Student.