Accident Overview
On August 25, 2009, at about 0956 Alaska daylight time, a Cessna 170B airplane, registration N6073V, sustained substantial damage when it collided with tundra-covered terrain after a loss of control shortly after takeoff from Runway 31 at Lake Hood Airstrip, Anchorage, Alaska. The airplane was operated as a visual flight rules (VFR) personal flight under Title 14 Code of Federal Regulations Part 91. The sole occupant, a private pilot, sustained serious injuries. Visual meteorological conditions prevailed, and no flight plan was filed. The flight was en route to Wasilla Airport, Wasilla, Alaska.
Witness Observations
A pilot preparing to depart behind the accident airplane reported that shortly after the accident airplane became airborne, he observed the right engine access cowling open. The witness stated that at approximately 150 to 200 feet above the runway, the right cowl came loose and violently flapped and twisted straight up and against the nose of the airplane. As the climb continued, the witness’s view was blocked by the wing of his own airplane, and he lost sight of the accident airplane just before the accident.
Other witnesses around Lake Hood Airstrip reported that after takeoff, the accident airplane’s climb shallowed, then it began a steep left turn back to the airstrip, followed by a rapid, nose- and left wing-low descent. The airplane collided with an area of swampy, tundra-covered terrain about 275 yards northwest of the departure end of Runway 31.
Post-Accident Examination
The NTSB investigator-in-charge (IIC) and an FAA airworthiness inspector examined the airplane wreckage on August 25 before recovery. The examination revealed no mechanical anomalies with the airplane, engine, or the engine cowling latch system. The engine access cowlings are hinged at the top by a piano hinge about 28 inches long, allowing each cowling to swing upward for engine inspection. When closed, each cowling is locked in place by two hook-and-lever style latches, one forward and one aft, mounted on the lower portion of each cowling.
Pilot Interview
During a hospital room interview on September 11, the pilot reported that he opened both engine access cowlings as part of his preflight inspection but could not specifically recall latching either side after finishing. He stated that just after takeoff, he saw the right engine access cowling open, and when he started a steep left turn back to the airport, the airplane descended nose down. He next recalled regaining consciousness as rescue crews began to arrive. The pilot added, “I should have climbed higher before returning to the airport.” He indicated that other than the open cowling, there were no preimpact mechanical problems with the airplane. Due to the extent of his injuries, the pilot was unable to complete an NTSB accident report form.