BIG BEAR CITY, CA, USA
N8742N
PIPER PA-28-140
ABOUT 300 FEET INTO THE INITIAL CLIMB, THE PILOT NOTED THE ENGINE RPM HAD DECREASED AND THE RATE OF CLIMB WAS ZERO. HE INITIATED A LEFT TURN BACK TOWARD THE RUNWAY, BUT NOTED HE WAS LOSING BOTH AIRSPEED AND ALTITUDE. HE LOWERED ONE NOTCH OF FLAPS TO MAINTAIN ALTITUDE, BUT THE AIRPLANE CONTINUED TO DESCEND. WITH AIRSPEED STILL DECREASING, THE AIRPLANE COLLIDED WITH TERRAIN SHORT OF THE RUNWAY. THE ESTIMATED DENSITY WAS 8,700 FEET. ACCORDING TO THE MANUFACTURER, MAXIMUM POWER AVAILABLE AT THAT DENSITY ALTITUDE WOULD HAVE BEEN BETWEEN 65 AND 70 PERCENT, OR NO MORE THAN 2,315 RPM AT CRUISE. NO DISCREPANCIES WERE NOTED DURING AN EXAMINATION OF THE AIRPLANE AND A POST-ACCIDENT RUNUP OF THE ENGINE.
On July 15, 1995, at 1235 hours Pacific daylight time, a Piper PA-28-140, N8742N, crashed during a forced landing at Big Bear City, California. The aircraft was destroyed and neither the airline transport pilot nor his passenger were injured. The aircraft was operated by Paradise Aviation and rented to the pilot for a personal flight when the accident occurred. The flight originated from Corona, California, at 1030 on the day of the accident. The flight departed Big Bear Airport at 1225 under visual meteorological conditions without filing a flight plan. In a telephone interview, the pilot reported that prior to departure he performed an engine run-up and magneto check. He also leaned the engine and made a static check, obtaining 2,625 rpm prior to takeoff on runway 08. After takeoff, the pilot initiated a shallow 80 mph climb until he reached 300-400 feet agl. Upon reaching the eastern shore of the lake he felt the aircraft decelerate. He then noticed that the engine had decreased to 2,400 rpm and the aircraft was no longer climbing. He checked his throttle for the full open position and the magnetos for the both position. Engine oil pressure and oil temperature indicators were both in the green range. He said he did not apply carburetor heat at any time. The aircraft continued to lose both airspeed and altitude as it approached the western shore. The pilot lowered 20 degrees of flaps in an effort to maintain altitude, but noted his vertical speed indicator (vsi) was now reading a 150 to 200 feet per minute (fpm) rate of descent. He decided against applying carburetor heat because he did not want to give up any more engine performance. Shortly thereafter, the pilot concluded that he did not have sufficient power or altitude to reach the runway and began to look for a suitable forced landing area. With his airspeed decreasing below 60 mph, the aircraft collided with brush and terrain about 30 to 40 yards short of an open area. The pilot was uncertain of the last rpm reading, but said he thought it was about 2,200 rpm. The pilot reported briefly encountering light to moderate precipitation after takeoff. The pilot reported that he weighed 190 pounds and his passenger was about 270 pounds. He said that the fuel was at the tabs on both tanks when he departed Corona. He estimated the flight time to Big Bear as 0.8 hour. He did not refuel before departing and estimated 30 gallons of fuel remained for the return flight. The airport manager at the Big Bear airport computed density altitude (DA) based on the hourly automatic weather observing system (AWOS) reports. He had computed a DA of 8,900 feet at 1200 hours, and 8,400 feet at 1300 hours local time. He estimated that DA was 8,700 feet at the time of the accident. A postcrash review of the aircraft and engine log books did not identify any discrepancies. The engine was examined after the aircraft was recovered. A thumb compression check was performed on all cylinders by a hand rotation of the propeller. The valve covers were removed and mechanical continuity was established by a hand rotation of the crankshaft and a visual confirmation of valve action. Residual oil under the valve covers did not appear burned or gummy. The top No. 1 and 3 spark plugs were dry and light gray in color. The No. 3 and 4 plugs were oil soaked. None of the electrodes appeared worn. The electrode gapping in all four plugs were consistent. The timing of each magneto was verified through hand rotation of the propeller. The left magneto sparked at 24 degrees, while the right magneto sparked at 23 degrees. A replacement propeller of the same make and model was installed and the engine was started, accelerated, and run. A magneto check was performed at 2,000 rpm with a 100 rpm drop obtained on both. During the run, fuel pressure registered 7 psi and oil pressure fluctuated between 65 and 70 psi. A static run-up produced 2,200 rpm at full throttle, which was within the prescribed performance range of 2,150 to 2,425 rpm. The propeller manufacturer and aircraft manufacturer both stated that the maximum limit on a static run-up is 2,425 rpm with no tolerance allowed. After the engine run was completed, the carburetor was disassembled and the venturi and floats inspected. The one piece venturi was in place and unobstructed. The metal floats were set at approximately .219 inches. The fuel screen was clean and unobstructed. A final compression check performed on all four cylinders revealed 73 psi on the No. 1, 72 psi on the No. 2, 74 psi on the No. 3, and 74 psi on the No. 4 cylinder. The manufacturer reported that the expected ground roll under the conditions reported by the pilot would have been over 30 percent greater at Big Bear City than he had experienced during his previous take off at Corona. The manufacturer concurred that the aircraft performance as reported by the pilot (rotation at 70 mph, acceleration to 80 mph for the initial climb with a 250 fpm rate of climb) was within the expected performance range for the density altitude conditions. The manufacturer estimated that the maximum power available at a density altitude of 8,700 feet would be between 65 and 70 percent, or no more than 2,315 rpm indicated at cruise. The manufacturer pointed out that power available and the rate of climb will continue to decrease as the aircraft continued to climb. As a result, attempts to maintain the rate of climb would result in a lower indicated airspeed and a greater power requirement than was available. The manufacturer also stated that the addition of 20 degrees flaps under the conditions described by the pilot did increase the coefficient of lift, but was more than offset by increased drag. Without additional power available the to overcome the increased drag coefficient, the deployment of 20 degrees flaps would result in a descent.
THE PILOT'S IMPROPER PLANNING/DECISION AND FAILURE TO OBTAIN OR MAINTAIN ADEQUATE AIRSPEED DURING TAKEOFF. A FACTOR RELATING TO THE ACCIDENT WAS: THE HIGH DENSITY ALTITUDE.
Source: NTSB Aviation Accident Database
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