Hernando, FL, USA
N1321
SMITH MINIPLANE DSA-4
The airplane had descended from about 1,600 feet to about 800 feet when the pilot/owner increased the throttle to initiate a climb. The engine began to run roughly, the pilot applied carburetor heat, the engine speed decreased to 2,000 rpm, and the airplane descended. Approximately 10 seconds later, about 500 feet agl, the engine stopped producing power and the propeller stopped. The pilot conducted a forced landing in a wildlife preserve, where the airplane rolled an estimated 40 feet, nosed over, and came to rest inverted. The accident airplane was one in a flight of two. The second airplane orbited the site until emergency services arrived. According to the owner of the second airplane, he too serviced his airplane at the same time and from the same vendor as the accident airplane and experienced no fuel-related problems. Postaccident examination of the airframe and engine revealed no preaccident anomalies that would preclude normal operation. The engine started immediately, accelerated smoothly, and ran continuously without interruption. According to an Federal Aviation Administration carburetor icing probability chart, the atmospheric conditions at the time of the accident were conducive to serious icing at glide power.
On November 27, 2011, about 1640 eastern standard time, an experimental amateur-built Smith Miniplane DSA-4, N1321, was substantially damaged during a forced landing and nose-over following a total loss of engine power near Hernando, Florida. The certificated private pilot/owner was not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight that originated at Marion County Airport (X35), Dunnellon, Florida, about 1630. The flight was destined for Twelve Oaks Airport (5FL7), Hernando, Florida, and was conducted under the provisions of 14 Code of Federal Regulations Part 91. According to the pilot, he departed 5FL7, his home airport, and flew to X35 where he serviced his airplane with 9.0 gallons of fuel. He was on the ground about 20 minutes, and then departed to return to 5FL7. About 10 minutes into the flight, while flying at 800 feet above ground level (agl) over the Potts Preserve Wildlife Management Area (Potts Preserve WMA), the pilot increased throttle in order to climb the airplane. The engine began to run roughly, the pilot applied carburetor heat, the engine speed decreased to 2,000 rpm, and the airplane descended. Approximately 10 seconds later, about 500 feet agl, the engine stopped producing power and the propeller stopped. The pilot completed a forced landing in the Potts Preserve WMA, where the airplane rolled an estimated 40 feet, nosed over, and came to rest inverted. The pilot then exited the airplane uninjured. He reported that a "light stream" of fuel poured from the engine cowling as he exited. The accident airplane was one in a flight of two. In a telephone interview, the pilot of the second airplane said the purpose of the flight was to take "air-to-air" photographs of the accident airplane while in flight, from his own airplane. He said the two airplanes departed X35 together, climbed to about 1,600 feet, and completed taking the desired photographs. The pilot of the second airplane said they were, "descending, going back" to their home airport, 5FL7, when the accident pilot declared over the radio that his airplane's engine was running "rough" and then announced that the engine had "stopped." The second pilot offered remedial-action advice over the radio and turned his airplane back as the accident airplane was below and behind him in the approach to 5FL7. The second airplane orbited the site until emergency services arrived. According to the owner of the second airplane, he too serviced his airplane with fuel at X35 and his airplane experienced no fuel-related problems. The airplane was recovered from the accident site, and secured in a hangar at X35. On December 2, 2011, Federal Aviation Administration (FAA) aviation safety inspectors examined the airplane. A cursory examination of the engine revealed no pre-impact mechanical anomalies. The crankshaft was rotated by hand at the propeller, and continuity was established through the powertrain to the valvetrain and the accessory section. Compression was confirmed on all cylinders using the thumb method, and the magnetos produced spark at all terminal leads. The inspection cover was removed from the crankcase, and a visual inspection inside the engine revealed no anomalies. During inspection of the fuel system, the gascolator bowl was found dislodged partially from its mount, and reinstalled. Continuity of the fuel system was then confirmed with no anomalies noted. On January 10, 2012, the airplane was serviced with fuel, a replacement propeller was installed, and all covers and accessories were reinstalled on the engine that had been removed during the initial post-accident inspection. The pilot/owner initiated an engine start, and the engine started immediately, accelerated smoothly, and ran continuously without interruption. He then conducted a normal engine shutdown. The pilot/owner then initiated a second engine start, and the engine again started immediately and ran continuously without interruption. He then conducted a magneto check, and confirmed engine oil pressure in the normal range, with no anomalies noted. The airplane's most recent annual inspection was completed on May 1, 2011 at 359 total aircraft hours. The pilot/owner held a private pilot certificate with ratings for airplane single engine land and instrument airplane. He was issued an FAA first class medical certificate on October 31, 2011. The pilot reported 2,634 total hours of flight experience, 100 hours of which was in the accident airplane make and model. At 1650, the weather reported at Ocala International Airport (OCF), 14 miles northeast of the accident site included few clouds at 6,000 feet, 10 miles visibility, and winds from 130 degrees at 3 knots. The temperature was 25 degrees C, the dewpoint was 11 degrees C, and the altimeter setting was 30.00 inches of mercury. Review of Advisory Circular 91-51A EFFECT OF ICING ON AIRCRAFT CONTROL AND AIRPLANE DEICE AND ANTI-ICE SYSTEMS states in paragraph 5 DISCUSSION b. " There are two kinds of icing that are significant to aviation: structural icing and induction icing....c. Small aircraft engines commonly employ a carburetor fuel system or a pressure fuel injection system to supply fuel for combustion. Both types of induction systems hold the potential for icing which can cause engine failure. (1) The pilot should be aware that carburetor icing can occur at temperatures between 13 degrees Celsius (C) (20 degrees Fahrenheit (F) and +21C (70F) when there is visible moisture or high humidity. This can occur in the carburetor because vaporization of fuel, combined with the expansion of air as it flows through the carburetor, causes sudden cooling, sometimes by a significant amount within a fraction of a second. Carburetor ice can be detected by a drop in rpm in fixed pitch propeller airplanes and a drop in manifold pressure in constant speed propeller airplanes. In both types, usually there will be a roughness in engine operation. Some engines are equipped with carburetor heat for use in both prevention and removal of ice." According to an FAA carburetor icing probability chart, the atmospheric conditions at the time of the accident were conducive to serious icing at glide power.
The pilot's failure to apply carburetor heat while descending in conditions conducive to carburetor icing, which resulted in carburetor icing and a subsequent total loss of engine power.
Source: NTSB Aviation Accident Database
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