On August 2, 2001, about 1520 eastern daylight time, a Cessna 172N, N3467E, registered to Aviation Atlanta, Inc, collided with trees during an aborted landing at Covington Municipal Airport, Covington, Georgia, while on a 14 CFR Part 91 instructional flight. Visual meteorological conditions prevailed at the time and no flight plan was filed. The airplane received substantial damage and the commercial-rated flight instructor and private-rated dual student received minor injuries. The flight originated from Atlanta, Georgia, the same day, about 1417. The flight instructor stated that after takeoff, they performed several commercial maneuvers and then diverted to Covington Municipal Airport to perform landings. They performed two full-stop landings. They took off on runway 10, and while turning crosswind, she applied carburetor heat and reduced engine power to idle. She then instructed the dual student to land on runway 28. When they aligned with the runway it appeared they were slightly high on the glide path to land in the first one third of the runway. She instructed the dual student to slow slightly to increase the rate of descent. After touchdown, they both applied the brakes and it appeared they would not stop before reaching the end of the runway, and the tires were skidding. The instructor took control of the airplane and began a short field takeoff. She believes that when they realized they might contact the trees at the departure end of the runway, the dual student may have fully deflected the control wheel to the left. They contacted the trees in a descending left bank and came to rest in the trees. The instructor stated they had no mechanical difficulties with the airplane. The dual student stated that while on final approach for the simulated engine out landing, they were above the desired approach path and at 75 knots airspeed. The instructor directed her to pitch up to reduce the airspeed in order to increase the sink rate. The airplane gained altitude, slowed down, and then started to descend, while moving further down the runway. It was clear to her that they were very far down the runway, a distance that had eliminated the possibility of a go-around. They were very close to landing, if not already landed. It was clear that they would be able to land safely and finish the roll out in the grass. At this point, the instructor took control of the airplane and initiated a go-around. She told the instructor to just go into the grass. The instructor continued the takeoff attempt. The stall warning horn was sounding during the climbout due to the low airspeed and the pitch up trim condition. She began to release the pitch up trim. She then put her hands back on the control wheel to help pull up. They then contacted the trees. The NTSB examined the airplane after recovery. The carburetor heat was found on. The airframe fuel lines were unobstructed. A fuel supply was connected to the engine, which was still mounted on the airplane, and the engine was started and operated to full power with no evidence of failure or malfunction. The engine magneto drop was about 50 rpm for each magneto. Maximum rpm obtained during the test run was 2,000 rpm. When carburetor heat was applied at full power, the engine dropped to 1,900 rpm. The normal static full power for the engine is about 2,200 rpm. The low full power rpm obtained during the test run was attributed to the fact that the engine test run was performed with the accident propeller, which had received bending damage during the accident.