On May 4, 1999, about 1432 central daylight time, a Cessna 172N, N739EW, registered to Flymasters, Inc., collided with a unmarked telephone line shortly after takeoff from T-Top Airfield Airport, Eagleville, Tennessee. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 CFR Part 91 instructional flight. The airplane was substantially damaged and the certified flight instructor (CFI) and student were not injured. The flight originated about 1 minute earlier. The CFI stated that the flight departed from runway 19 at the Smyrna Airport, Smyrna, Tennessee, then proceeded to the Nashville International Airport, Nashville, Tennessee, where the student performed one touch-and-go landing on runway 20C. The flight then proceeded direct to T-Top Airfield Airport, where the student entered the traffic pattern to land on runway 01. During the midfield downwind leg, the CFI reduced the throttle to idle to simulate a loss of engine power. The student landed the airplane about midpoint on the 3,000-foot grass runway, and performed a go-around. The simulated loss of engine power was performed two more times, the first power loss simulation occurring abeam the numbers and the second power loss simulation occurred at a 45 degree angle to the runway. During the 3rd simulation, the airplane was landed again 1/2 way down the runway. The student raised the flap selector handle to retract the flaps, pushed in carburetor heat, and applied power without delay. While climbing out at an airspeed greater than the published best angle of climb (Vx), the CFI observed trees that were ahead, but did not notice an unmarked phone line that was lower than marked power lines. The airplane collided with the unmarked phone line then impacted the ground. Both exited the airplane unaided. The CFI further reported that there was no engine, airframe, or system preimpact failure or malfunction, and that he had permission to fly into that private airstrip and had previously flown into there 8-10 times. Examination of the accident site by the FAA airworthiness inspector revealed that the left wing of the airplane collided with an unmarked phone line about 25 feet above ground level (agl). The phone line was located beneath two power lines, one of which was marked with a ball. The power lines were not damaged. After the contact with the phone line the airplane flew approximately 66 feet where the right wing collided with a tree about 10 feet agl; separating 8-10 feet of the right wing. The airplane continued and came to rest 135 feet beyond the tree impact on a heading of 270 degrees. The flap actuator was examined and found to be extended approximately 5 degrees; the flap circuit breaker was not popped. Weather observations taken from the Shelbyville Airport 12 minutes before and 8 minutes after the accident, indicates that the wind was from 180 at 12 knots and 190 at 11 knots respectively. The Shelbyville Airport is located 12.1 nautical miles and 125 degrees from the accident airstrip. Weather observations taken 8 minutes after the accident from Ellington Airport (KLUG), Maury County Airport (KMRC), and Murfreesboro Municipal Airport (KMBT), indicates that the wind was from 160 degrees at 9 knots with gusts to 14 knots, 150 degrees at 12 knots with gusts to 18 knots, and 190 degrees at 11 knots with gusts to 15 knots, respectively. The KLUG airport is located 13.6 nautical miles and 213 degrees from the accident site. The KMRC airport is located 27.8 nautical miles and 250 degrees from the accident site. The KMBT airport is located 17.0 nautical miles and 044 degrees from the accident site.