N5967A

According to the pilot's written statement, they were taking off on runway 27. He setup for a soft field takeoff with 10 degrees of flaps. He noted liftoff was about 50 percent down the runway and he attempted to climb out at the best angle of climb airspeed (60 mph). The pilot said he realized that the climb angle was not going to clear the trees at the end of the runway. He estimated the tree heights to be about 100-120 feet. The pilot reported that he looked for the lowest trees to clear, which were to the southwest side of the runway. The airplane hit a small pine tree head-on and then landed between two larger trees. He noted the wind condition as blowing from the west-southwest about 7 to 10 knots.

The pilot reported that he and another adult were seated in the front, and two children were seated in the back. They had been at Lake Wenatchee camping for a couple of days.

A review of the FAA's Airport Facility Directory revealed limited information about the airport. However, an Internet search on http://www.airnav.com and the Washington State Department of Transportation Aviation Division http://www.wsdot.wa.gov/aviation/Airports/LakeWenatchee.htm yielded the following information about the airport:

Runway length and width: 2,473 feet by 100 feet

Runway condition: turf, in poor condition, ROUGH

Gradient: 0.5 percent

Obstructions: 16 feet road, 104 feet right of centerline

Trees surround the airport and are in close proximity to both the approach and departure ends of the runway.

The airplane was a 1956 Cessna 172, with a O-300 Teledyne Continental Motors 145-horsepower engine installed. According to the Cessna Owner's Manual, the procedure for a short field takeoff is:

Wing flaps 10 degrees (first notch)

Apply full throttle and raise nose wheel clear of ground with elevator control backpressure

Takeoff in a tail low attitude

Level off momentarily to accelerate to a safe airspeed

Retract flaps slowly as soon as reasonable altitude is obtained

In the Operating Details section under TAKEOFF, the owner's manual states that the use of 10 degrees of flaps will shorten the ground run by about 10 percent; however, that advantage is lost in the climb to a 50-foot obstacle.

A Cessna representative calculated performance figures using the following information:

Takeoff gross weight: 2,020 lbs

Temperature: 65 degrees Fahrenheit

Airport Elevation: 1,939 feet

Takeoff flaps: 0 degrees

Zero Wind

Grass Field

The distance to clear a 50-foot obstacle would have been 1,909 feet with a ground roll of 839 feet. Advisory Circular (AC) 61-84B titled Role of Preflight Preparation contains information on takeoff procedures for runways with various surface compositions, slopes, and degrees of roughness. With a 1-percent upslope takeoff, additional drag and rolling friction can result in a 20 percent increase in the takeoff distance. The distance calculated to clear a 50-foot obstacle from a 0.5-percent upslope would be about 2,100 feet with a ground roll of 923 feet.

AC 61-84B also informs the pilot that the retarding effect on the takeoff run that water, snow/slush, sand, gravel, mud, or long grass on a runway will have is difficult to predict, and is critical to the success of a takeoff.

A Federal Aviation Administration (FAA) inspector responded to the accident site. He estimated the tree height to be about 70 feet. Runway 27 was upsloping and into rising terrain. The camping gear located in the aft baggage compartment of the airplane was weighed and totaled 115 pounds. An FAA inspector interviewed the pilot; who stated he needed 2,000 feet of takeoff distance to clear a 50-foot obstacle.