ERA17CA068 · Beech A36 UNDESIGNAT

Passengers reported that, during a winter flight, cold air was entering the airplane from the left side of the passenger cabin. Afterward, the pilot examined the area and discovered that there was a small gap under the emergency exit window that was allowing air to enter the cabin from outside the airplane. He opened the window and examined the rubber seal, which was intact. However, he could not tell if it was compressed or thinner than normal. He then closed and latched the window and inspected the latch with a flashlight to make sure it was latched. Because he was going to fly back to his home airport in similar winter conditions on the next flight, he took several rolled-up paper towels and placed them between the trim and the window to try and keep the cold air out and placed a strip of blue painter's tape on the outside of the lower portion of the window to further reduce the entry of cold air. He decided to fly the airplane once around the traffic pattern before fueling up for his return flight. After takeoff and while on the downwind leg of the traffic pattern at 800 ft, he suddenly heard a "whoosh" behind his seat. Instead of landing and checking to see what happened, he checked for other traffic, turned on the autopilot, in heading and altitude mode, then reached around behind him to shut and latch the window, which had opened 2 to 3 inches. Seconds later, after turning back around to his normal seated position, he heard a loud "pop" and turned around and saw that the window had opened completely. Given that he was afraid it would come off the airplane and strike the tail, he reached back again and pulled the window down. The pilot reported that he must have "bumped" the autopilot off while he was doing this, because when he looked forward to check for traffic, he noticed that the airplane was approaching the ground. He then banked left and right to determine his location and spot any obstacles, raised the nose, and added power to climb. He then noticed that there were power lines slightly higher than his altitude directly in front of him, and rather than risk a possible stall close to the ground by pulling back suddenly, he lowered the nose and "put" the airplane on the ground. The airplane then struck trees, and a fire ensued, which resulted in substantial damage to the airframe. Examination of the emergency exit window 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.

Verbatim NTSB analysis and probable cause from the NTSB dataset