Anchorage, AK, USA
N6073V
CESSNA 170B
The private pilot was departing on a Title 14, CFR Part 91, personal flight. Witnesses reported that shortly after it became airborne, the right engine access cowling opened, and the airplane began a steep left turn back to the airport. As the airplane’s left bank increased, it descended nose first into tundra-covered terrain. The pilot said he could not specifically recall latching the cowling after preflighting the airplane, and that he should have climbed the airplane higher before returning to the airport. Examination of the airplane did not disclose any preimpact mechanical malfunction. Given the lack of mechanical deficiencies with the airplane's engine or flight controls, in conjunction with the witness and the pilot’s statement, it is likely the pilot failed to properly latch the engine access cowling before takeoff, then failed to adequately maintain control of the airplane while returning to the airport after the cowling opened.
On August 25, 2009, about 0956 Alaska daylight time, a Cessna 170B airplane, N6073V, received substantial damage when it collided with tundra-covered terrain following a loss of control shortly after takeoff from Runway 31 at the Lake Hood Airstrip, Anchorage, Alaska. The airplane was being operated as a visual flight rules (VFR) personal flight under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91, when the accident occurred. 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 the Wasilla Airport, Wasilla, Alaska. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on August 25, a pilot that was preparing to depart behind the accident airplane said that shortly after it became airborne, he saw the right engine access cowling open. In a written statement to the NTSB, the witness reported: “I saw the Cessna 170B climbing out from Runway 31 and 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.” The witness said that as the accident airplane’s climb continued, the wing of his airplane blocked his view, and he lost sight of it just before the accident. Other witnesses from around the Lake Hood Airstrip reported to the NTSB IIC that just after takeoff, the accident airplane’s climb shallowed, then it began a steep left turn back to the airstrip, which was 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. The NTSB IIC, and a Federal Aviation Administration (FAA) airworthiness inspector, Anchorage Flight Standards District Office, traveled to the accident site on August 25 to inspect the airplane wreckage before recovery. An 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, which measures about 28 inches long, allowing each cowling to swing upward for inspection of the engine. When the engine access cowlings are closed, each is locked in place by two hook and lever style latches, one forward, and one aft, mounted on the lower portion of each cowling. During a hospital room interview with the NTSB IIC on September 11, the pilot reported that he opened both engine access cowlings as part of his preflight inspection, but he could not specifically recall latching either side once he finished. He added 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 said that the next thing he recalls is regaining consciousness as rescue crews began to arrive on scene. Additionally, he stated, in part: “I should have climbed higher before returning to the airport.” The pilot said that other than the open engine access cowling, there were no preimpact mechanical problems with the airplane. Due to the pilot’s extensive injuries sustained in the accident, he was unable to complete an NTSB accident report form.
The pilot’s decision to make an abrupt and steep low altitude turn just after takeoff, while attempting to return to his departure airport, resulting in an aerodynamic stall and loss of aircraft control. Contributing to the accident was the pilot’s failure to ensure that the airplane’s engine access cowling was properly latched before takeoff.
Source: NTSB Aviation Accident Database
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