Incident Details
During a winter flight, passengers reported cold air entering from the left side of the passenger cabin. After landing, the pilot examined the area and discovered a small gap under the emergency exit window that allowed air to enter from outside. He opened the window, examined the rubber seal (which was intact, though he could not determine if it was compressed or thinner than normal), then closed and latched it, inspecting the latch with a flashlight to confirm it was latched.
Pilot Actions
Planning to fly back to his home airport in similar winter conditions, the pilot took several rolled-up paper towels and placed them between the trim and the window to block cold air, and applied a strip of blue painters tape to the outside of the lower window portion for additional sealing. On a clear day, he decided to fly the airplane once around the traffic pattern before fueling for the return flight. After takeoff, while on the downwind leg at 800 feet, he heard a "whoosh" behind his seat. Instead of landing to check, he looked for traffic, engaged the autopilot in heading and altitude mode, and reached behind to shut and latch the window, which had opened 2 to 3 inches. Moments later, after returning to his normal seated position, he heard a loud "pop" and found the window now fully open. Fearing it might detach and strike the tail, he reached back again to pull the window down. The pilot believed he inadvertently disengaged the autopilot during this maneuver; when he looked forward, he saw the airplane approaching the ground.
Aftermath
The pilot banked left and right to determine his location and spot obstacles, raised the nose, and added power to climb. He then noticed powerlines slightly higher than his altitude directly ahead. To avoid a possible stall close to the ground, he lowered the nose and "put" the airplane on the ground. Approaching the edge of a field bordered by trees, he aimed the nose between trees. The airplane struck the trees, and a fire ensued, resulting in substantial damage to the airframe. An inspection by a Federal Aviation Administration inspector revealed that the paper towels the pilot inserted in the gap between the window and the airframe were interfering with the window's latching mechanism.