Poughkeepsie, NY, USA
N5136L
Piper PA-28-180
With the outside air temperature approximately 12 degrees Fahrenheit and the dew point approximately -8 degrees Fahrenheit, the pilot departed for closed traffic. He turned final about 0.5 mile from the runway, and was a "little" higher than anticipated." He reduced throttle, and the airplane intercepted the glide path about 350 feet from the end of the runway. He then added throttle to maintain his descent angle, but engine power did not increase. He waited a couple of seconds, and added more throttle. Still power did not increase, so he added a "substantial" amount of throttle, and started to flare the airplane. The engine responded, but before the pilot could arrest the descent rate, the airplane touched down short of the runway. Examination of the engine and carburetor revealed no preimpact failures or malfunctions. Research has shown that when engine power is reduced to idle, the engine cools rapidly, and vaporization of fuel is less complete, which can slow engine response times, or cause a complete loss of engine power. Sudden throttle movements can aggravate this situation, and the pilot should try to keep the engine warm during glides by frequently opening the throttle.
On January 18, 2003, about 1210 eastern standard time, a Piper PA-28-180, N5136L, was substantially damaged while landing at the Dutchess County Airport (POU), Poughkeepsie, New York. The certificated private pilot and passenger were not injured. Visual meteorological conditions prevailed for the personal local flight that departed about 1205. A flight plan was not filed, and the flight was conducted under 14 CFR Part 91. According to the pilot, he applied preheat to the engine, and went back to the pilot's lounge to check weather. He then went back out and preflighted the airplane. He checked all three fuels sumps several times and each fuel sample was absent of contaminates. He checked both fuel vents, and did not identify any visual obstructions. He completed the preflight, removed the preheat, which had been warming the engine for more than 45 minutes, and boarded the airplane. The engine started on the first attempt, and the pilot waited until the engine oil temperature was in the "green," before taxing to runway 24 for left closed traffic. The pilot completed the runup checks, noted no anomalies, and then taxied onto the runway. He advanced the throttle, the engine responded, and the airplane became airborne where expected. The pilot added that climb performance was a little better than normal, which he contributed to the cold weather. After completing crosswind, downwind, and base, the pilot turned final about 0.5 mile from the runway. On final, the airplane was a "little" higher than the pilot wanted, so he reduced throttle, and the airplane intercepted the glide path about 350 feet from the end of the runway. He then increased the throttle to maintain his descent angle, but engine power did not increase. He waited a couple of seconds, and added more throttle. Still power did not increase, so he added a "substantial" amount of throttle, and started to flare the airplane. The engine responded, but before the pilot could arrest the descent rate, the airplane touched down about 20 feet short of the runway on snow-covered ground. He applied aft yoke, but within a few seconds, the nose wheel collapsed, and the airplane slid to a stop on the runway. According to a Federal Aviation Administration (FAA) inspector, several engine mounts were broken consistent with overload, and the engine firewall was substantially damaged. The inspector was able to confirmed engine control continuity. He also observed no visible signs of fluid loss, nor did he identify any preimpact malfunctions with the engine. In addition, on March 14, 2003, an examination of the carburetor revealed it was adjusted to manufacturer specifications, and no preimpact failures or malfunctions were identified. The FAA Pilot's Handbook of Aeronautical Knowledge stated: "Whenever the throttle is closed during flight, the engine cools rapidly and vaporization of fuel is less complete. The airflow through the carburetor system under such conditions may not be of sufficient volume to assure a uniform mixture of fuel and air. Consequently, the engine may cease to operate because the mixture is too lean or too rich. Suddenly opening or closing the throttle could aggravate this condition, and the engine may cough once or twice, sputter, and stop. Three precautions should be taken to prevent the engine from stopping while idling. First, make sure that the ground idling speed is properly adjusted. Second, do not open or close the throttle abruptly. Third, keep the engine warm during glides by frequently opening the throttle for a few seconds." In addition, according to a FAA carburetor icing probability chart, atmospheric conditions were not conducive for carburetor icing at the time of the accident. A weather observation taken at the airport about 17 minutes after the accident recorded the wind as calm, visibility 10 miles, sky clear, temperature 12 degrees Fahrenheit, dew point -8 degrees Fahrenheit, and an altimeter setting of 30.13 inches of mercury.
The pilot's failure to maintain an adequate amount of engine power while maneuvering to land, which produced delayed engine response times. A facture in the accident was the cold day.
Source: NTSB Aviation Accident Database
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