DONNELLY, ID, USA
N1418U
Cessna 172M
The pilot and two passengers landed on a short grass airstrip that the pilot had never landed on before. He boarded a third passenger, and performed a mental calculation for takeoff performance. He decided to takeoff uphill and into the wind. The airstrip was surrounded by tall trees, and the density altitude was about 6,000 feet. The airplane was at or near its maximum gross takeoff weight. The pilot selected 20 degrees of flaps for the takeoff, and an additional 20 degrees during climbout, despite information to the contrary on the use of flaps published in the airplane's pilot operating handbook (POH). The airplane impacted trees at the end of the runway after the pilot's attempt to abort the takeoff just prior to impact. According to the performance charts found in the POH, the airplane would have been unable to clear the trees under the given conditions. The pilot stated that the engine was unable to produce full power at takeoff. Subsequent testing of the engine did not reveal any preimpact mechanical malfunctions.
On July 19, 1997, about 1900 mountain daylight time, N1418U, a Cessna 172M, operated by the owner/pilot, collided with trees and was substantially damaged during takeoff from the Donnelly Airport in Donnelly, Idaho. The private pilot and his three passengers received minor injuries. Visual meteorological conditions prevailed and a visual flight rules (VFR) flight plan had been filed. The personal flight was destined for Caldwell, Idaho, and was conducted under 14 CFR 91. According a written statement sent to the Safety Board (attached), and interviews with the Valley County Sheriff's Department (report attached), the pilot stated that he departed from Caldwell with two passengers for the purpose of picking up his son who was at the Donnelly Airport. The pilot had never landed or taken off from Donnelly. After a "perfect" landing at the Donnelly Airport, the pilot's son boarded the airplane, and the pilot taxied for takeoff. He stated that he decided to takeoff into the wind, and noticed that the direction of takeoff would be uphill. The pilot stated: Locked down on brakes, put flaps to 20 [degrees] down to leave runway quicker, [added] full power, leaned engine, let off brakes. Left runway at 1,000 [feet]... about 2000 feet engine speed slowed, we started sinking; saw a creek off to the [right] of end of runway, tried to head for it because we could not clear trees in front of us. Put on full flaps, just about the time we hit the small tree off the [right] end of runway. Cut engine throttle after hitting the trees. The pilot told a Federal Aviation Administration (FAA) aviation safety inspector from Boise, Idaho, that he had performed a "mental calculation" and felt that he had enough runway to safely perform a takeoff. The pilot also reported that the takeoff roll was longer than normal, but he did become airborne, and that he felt the engine lose partial power while flying about 40 feet above the ground. The Donnelly Airport (diagram attached), consists of a single grass runway oriented north-south. The field elevation of the airport is 4,860 feet above mean sea level. The runway is 2,500 feet in length and is surrounded by trees. It is recommended to "land [runway] 36 and depart [runway] 18, when wind conditions permit." The runway slopes upward when taking off to the north. The Safety Board took into account the reported weights of each of the occupant, the estimated weight of the baggage, the amount of fuel found in the wreckage, and the most recent recorded empty weight of the airplane. When added, the weight was at or near the airplane's published maximum gross takeoff weight of 2,300 pounds. The pilot reported that the temperature was about 65 degrees F at the time of the accident. This is consistent with the recorded temperature of the Automated Weather Observation Station (AWOS) at McCall, Idaho, located about 10 nautical miles to the north. Using this data, the Safety Board computed that the density altitude of the Donnelly Airport about the time of the accident was about 6,000 feet. According to performance information published in the accident airplane's pilot operating handbook (excerpts attached), the takeoff distance is computed to be 2,938 feet under the following conditions: 1.) maximum gross weight; 2.) 50-foot obstacle; 3.) level, grass runway ; 4.) pressure altitude of 5,000 feet ; 5.) temperature of 68 degrees F. The result of this computation for takeoff distance is 438 feet greater than the total runway length at the Donnelly Airport. According to the airplane's pilot operating handbook, under the normal procedures checklist for short field takeoffs, the checklist states: "1. Wing Flaps - UP." In the "Amplified Procedures" section, under the time of "WING FLAP SETTINGS," the manual states: Normal and short field takeoffs are performed with flaps up. Flap settings greater than 10 [degrees] are not approved for takeoff. Use of 10 [degree] flaps is reserved for takeoff from soft or rough fields. Use of 10 [degrees] flaps allows safe use of approximately 5 KIAS lower takeoff speeds than with flaps up. The lower speeds result in shortening takeoff distance up to approximately 10%. However, this advantage is lost if flaps up speeds are used, or in high altitude takeoffs at maximum weight where climb performance would be marginal with 10 [degrees] flaps. Therefore, use of 10 [degrees] flaps in not recommended for takeoff over an obstacle at high altitude in hot weather. The pilot, age 45, was a certficated private pilot with a rating for airplane single engine land. He reported that he had accumulated a total of 100 hours of flight time, including 30 hours in type. He was employed as a lawyer. According to FAA records, the pilot's Third Class Medical Certificate had expired about nine months prior to the accident. The wreckage was examined at the accident site on July 20, 1997, by an FAA aviation safety inspector from Boise, Idaho. According to the inspector (report attached), the aircraft was located off the north end of the runway in a horse corral. The airplane's left horizontal stabilizer, engine fire wall, nose gear attachment area, tailcone, and right aileron were substantially damaged. Evidence of freshly damaged trees were found to the south of the final resting site of the wreckage. Under the Safety Board's direction, the engine was removed from the airplane and underwent operational testing on September 16, 1997, at an engine repair facility in Caldwell. The test (report attached) was supervised by an FAA inspector. During the testing, the engine was run up to 2,700 revolutions per minute with no anomalies noted. When asked to respond in writing to the question "How Could This Accident Have Been Prevented," on NTSB form 6120.1/2 (attached), the pilot wrote: "Possible greater margin for climb out, so loss of power momentarily would not have had as great an impact. Also, depart over water."
The pilot's failure to perform proper preflight planning for the flight, and his failure to obtain/maintain clearance from trees during takeoff. Factors contributing to the accident include the pilot's delayed remedial action, his improper use of flaps, and high density altitude.
Source: NTSB Aviation Accident Database
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