LEAVENWORTH, WA, USA
N3645A
PIPER PA-22-135
THE PILOT INITIATED A TAKEOFF FROM A ROUGH TURF AIRSTRIP THAT WAS 2400' IN LENGTH. THE RUNWAY HAD AREAS OF SOFT DIRT INTERSPERSED WITH AREAS OF GRASS THAT RANGED FROM 1 TO 8 INCHES IN HEIGHT. DURING TAKEOFF, THE AIRCRAFT COLLIDED WITH TREES NEAR THE DEPARTURE END OF THE RUNWAY. THE TREES WERE ABOUT 75' TALL; IMPACT OCCURRED ABOUT 50' ABOVE THE GROUND. CALCULATIONS SHOWED THAT THE DENSITY ALTITUDE WAS ABOUT 4700', AND THAT WITH THE PREVAILING CONDITIONS, ABOUT 2213' TO 2616' OF RUNWAY WOULD HAVE BEEN NEEDED FOR THE TAKEOFF GROUND RUN.
HISTORY OF FLIGHT On July 9, 1994, approximately 1320 Pacific daylight time (PDT), a Piper PA-22-135, N3645A, impacted trees off the departure end of runway 27 while attempting a takeoff from Lake Wenatchee State Airport, Leavenworth, Washington. The private pilot and her two passengers received fatal injuries, and the aircraft was destroyed. The personal pleasure flight, which was operating in visual meteorological conditions, was in the process of departing for Harvey Field, Snohomish, Washington. No flight plan had been filed, and there was no report of an ELT activation. According to FAA records, an individual called the Seattle Automated Flight Service Station at 1007 PDT on the day of the accident requesting a standard briefing for a flight from Sierra 43 (Harvey Field) to WA-32 (Lake Wenatchee State Airport). The individual who requested the briefing said that it was for a flight in N3645A, and that they expected to depart Harvey Field about 1100 PDT. No one reported seeing the aircraft depart Harvey Field or land at Wenatchee State Airport, but a couple who were camping near the airstrip reported talking to the occupants of the aircraft shortly after noon. These witnesses said that the people from the aircraft stated that they had landed at Wenatchee State about noon, were planning to have a picnic, and then return to Harvey Field. No other witnesses were found who had either talked to the aircraft's occupants or saw the aircraft attempt to takeoff. At 1322 a Forest Service lookout station reported a small column of smoke coming from the west end of the airstrip. In less than five minutes a Chelan County Deputy was on the scene, and reported that the fire had spread to a 100 foot diameter. According to the deputy, only after the fire was contained and the smoke began to clear did he and the fire fighters realize that an aircraft was in the center of the burned area. WRECKAGE AND IMPACT INFORMATION The aircraft came to rest about 300 feet past the departure end of runway 27. It was found laying on its right side, about 75 feet inside the edge of the coniferous forest which borders the entire airstrip. Two trees on the very edge of the forest had a number of impact marks about 50 feet above the ground. These trees were about 75 feet in height. The magnetic heading from these trees to the aircraft wreckage was 220 degrees. Two small pieces of plexiglass were found below the trees where the initial impact took place. A radio antenna was found about 11 feet from the initial impact, and a sheet metal wing tank cover was located about 30 feet down-track from the antenna. The remainder of the airframe came to rest against the base of a tree. There were no ground impact scars between the point of initial impact and the point where the aircraft came to rest. The right wing was folded back parallel to the fuselage, and the fuselage was laying on top of the wing. The right main gear was folded aft and out, and the left main gear was in its normal position. The nose gear strut was intact, but bent aft. All three tires, the cloth airframe covering, and all wooden components were consumed by the fire. Both wing lift struts were still attached to the fuselage longerons, and to both front and rear wing spar attach brackets. The rudder and elevator flight controls showed mechanical continuity, and the ailerons showed continuity from the flight control surface to a point where the cables entered the cabin. One blade of the propeller showed clear chordwise scarring along most of its span in an area near the leading edge of its front surface. It also showed chordwise scarring across the outer two- thirds of its aft surface. This same blade had a couple of small indentations on its leading edge, and was bent in a continuous backward arc from its root to its tip. The other blade showed a small amount of leading edge scarring, but did not have any significant chorwise scarring. This blade was bent aft about 30 degrees from its root to a point about eight inches from the tip. The last eight inches were bent aft another 30 degrees. The propeller was able to be freely turned, and mechanical continuity was established through the power drive train to the accessory section. All push rods, rockers, and valves responded to the rotation of the camshaft, and there was no evidence of any engine malfunction. METEOROLOGICAL INFORMATION During the morning weather briefing the pilot of N3645A was advised that Wenatchee Airport, which is located about 32 miles east of the accident site, was currently reporting 79 degrees, with wind out of the south at 17 knots. The forecast that was given for Wenatchee included clear conditions all day, with afternoon winds predicted to be out of the northwest at 15 gusting to 30 knots. The surface observation taken at Wenatchee, 32 miles east of the accident site, at 1355 PDT showed clear below 12,000 feet, visibility 10 miles, temperature 89 degrees, dew point 32 degrees, winds 300 degrees at 12 knots, gusting to sixteen, and an altimeter of 29.87. At the time of the accident, a ranger station about three miles from the airport reported a temperature of 80 degrees, and winds out of the west at about five knots. AERODROME INFORMATION Wenatchee State Airport is a 2,400 foot long turf airstrip located at an elevation of 1,936 feet mean sea level (MSL), and is managed by the Washington State Department of Transportation. It is surrounded by coniferous trees, and is noted in the Pilot's Guide to Washington Airports as being rough, and soft when wet. The same guide has a warning to pilots to use caution because of possible high density altitude, and another caution to "Use at own risk." At the time of the accident the runway was dry, and rough, with areas of soft dirt interspersed with areas of dry grass, which ranged from one to eight inches in height. PERFORMANCE DATA During the investigation takeoff performance calculations were made using the Piper Pacer PA-22 Owners' Handbook, an interpolated barometric pressure, occupant weights from drivers licenses, and the Aircraft Accident Investigation Utility for Windows (WINVEST) computer program from Macswain Enterprises. The following data was used for input into the calculations: a total occupant weight, including clothing and picnic lunch, of 450 pounds; an aircraft empty weight of 1060 pounds; a fuel weight of 60 pounds (based upon the minimum amount of fuel needed for the flight to return to Harvey field); an altimeter setting of 29.17 inches (based upon the MSL altitude difference between the known altimeter setting at Wenatchee); a temperature of 80 degrees Fahrenheit; no wind (based upon the extent to which the surrounding trees blocks the wind from the runway surface); and a PA-22 published 1,220 foot takeoff ground run at gross weight under standard conditions at sea level. The WINVEST density altitude (DA) calculation determined the DA to be 4,701 feet. This DA was used for two separate Operations From Unimproved Strips calculations. One calculation assumed a rough field or short grass (less than four inches high), and the other assumed long grass (greater than four inches high). The short grass calculation showed a required ground run to lift-off distance of 2,213 feet, and the long grass calculation showed a required distance of 2,616 feet (see attached WINVEST calculations). ADDITIONAL INFORMATION A forensic toxicology was performed on the pilot by the FAA Toxicology and Accident Research Laboratory. Results indicated 12.000 % carboxyhemoglobin and 0.830 (ug/ml) cyanide detected in the blood. No ethanol or screened drugs were detected in the urine. An autopsy was performed on the pilot by Dr. Gerald A. Rappe, the Chelan County Coroner, and the cause of death was determined to be due to the fire that resulted from the crash. The manner of death was listed as accidental. The aircraft was released to Christine P. Straker, the registered owner, on July 7, 1994 at the sight of the accident. The removal of the wreckage was arranged by family members of the registered owner.
THE PILOT'S INADEQUATE PREFLIGHT PLANNING/PREPARATION. FACTORS RELATED TO THE ACCIDENT WERE: HIGH DENSITY ALTITUDE, THE RUNWAY CONDITION (WITH AREAS OF SOFT OR UNEVEN TERRAIN AND TALL GRASS), AND OBSTRUCTIONS (TREES) NEAR THE DEPARTURE END OF THE RUNWAY.
Source: NTSB Aviation Accident Database
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