Fitchburg, MA, USA
N4041J
CESSNA 150G
On the day of the accident, the student pilot conducted a touch-and-go landing and then entered the traffic pattern to perform another one. While on the downwind leg of the traffic pattern, the engine began to run roughly, so the student applied carburetor heat and kept it on until touchdown. During climb after the second touch-and-go landing, the engine began running roughly again. Subsequently, the flight instructor took control of the airplane, lowered the angle-of-attack, and reapplied carburetor heat. According to the flight instructor, the engine subsequently ran more roughly, so he immediately placed the carburetor heat to “off.” He stated that, although the engine then ran less roughly, it still ran roughly. The flight instructor decided that there was not sufficient remaining runway to “land.” He was not sure how much power the engine was producing or if he could maintain level flight. He stated that he thought about turning back but decided against it. He said that the airplane was low and slow, so he decided to continue straight ahead. He tried to keep the airplane flying and was successful for about 15 to 20 seconds, but then he observed a warehouse ahead and banked to the right to avoid it. The airplane then settled and struck trees, substantially damaging the airplane and seriously injuring the student pilot. Examination of the airplane and engine revealed no evidence of any preimpact mechanical failure or malfunction that would have precluded normal operation. However, a postaccident review of weather data and a carburetor icing probability chart also revealed that, at the time of the accident, the ambient temperature and dew point favored serious icing. Industry and Federal Aviation Administration guidance advised pilots to be aware of the warning signs of carburetor ice, including loss of rpm (with a fixed-pitch propeller) and rough running (both of which occurred before the accident), and advised that the pilot should respond to these warning signs by immediately applying full carburetor heat, and that the engine may initially run roughly for a short time while the ice melts. Therefore, the flight instructor should not have turned off the carburetor heat when the engine was still running roughly after he turned it on.
HISTORY OF FLIGHT On January 11, 2012, at 1000 eastern standard time, a Cessna 150G, N4041J, operated by TENLE Aviation, was substantially damaged during an impact with terrain following a loss of engine power during initial climb near Fitchburg Municipal Airport (FIT), Fitchburg, Massachusetts. The certificated flight instructor received minor injuries and the student pilot was seriously injured. Visual meteorological conditions prevailed, and no flight plan was filed for the instructional flight conducted under Title 14 Code of Federal Regulations (CFR) Part 91. According to the flight instructor, he and the student met up that morning at Minute Man Air Field (6B6), Stow, Massachusetts, for the instructional flight in the accident airplane. During preflight, the student pilot noticed that the power cord for the engine preheat was in the oil service door but was not plugged in. The outside air temperature at the time was -01 degree Celsius and the engine was cold. He then plugged in the preheater and continued preparing the airplane for the flight lesson. There was frost on the windows, which the student pilot cleaned off. The wings and horizontal stabilizer did not however have any frost on them, as they had been covered. About 30 minutes later they disconnected the preheater, then got into the airplane and attempted to start it, but it did not start and it took them 4 or 5 attempts with increasing operation of the primer before the engine started. They next taxied to runway 3, and did the pretakeoff checks. During the runup both the magneto check and carburetor heat check were normal and both checks resulted in an rpm drop that was within limits. They then departed for FIT. After arriving at FIT the student pilot did a touch and go landing, and then entered the traffic pattern to perform another one. Then while on the downwind leg the engine began to run rough so he had the student apply carburetor heat. Then during the climb after the second touch and go landing, the engine began to run rough. The flight instructor took control of the airplane, lowered the angle of attack, and applied carburetor heat by pulling out the carburetor heat knob. The engine "immediately ran rougher" and the flight instructor pushed in the carburetor heat knob. The engine then ran "less rough" but still ran rough. The flight instructor then looked over the nose and observed that he had a minimal amount of runway left and that a tractor was also off the end of the runway. He decided that there was not enough runway to land. He was not sure how much power the engine was producing or if he could maintain level flight. He thought about turning back but decided against it. He felt that he was "low and slow' and decided to continue straight ahead. He tried to keep the airplane flying and was successful for about 15 to 20 seconds but then he observed a warehouse ahead of them and banked to the right to avoid it. The airplane then settled and struck trees. According to the student pilot, he arrived early for his lesson to conduct preflight activities. He indicated that it was a cold morning and had looked at the Aviation Digital Data Service (ADDS) for weather information. He removed and stowed the wing covers and conducted a walk around inspection. When checking the oil level he noted that the engine pre-heat cord had come unplugged overnight. He reconnected the power cord and completed his preflight. No other issues were noted by him. He indicated that cold weather starting procedures were utilized, which included priming and pulling the propeller through by hand. It took several attempts to start the engine. The engine was warmed up for several minutes prior to conducting the magneto checks. It was noted that the engine revolutions per minute (RPM) dropped 75 to 100 RPM when each magneto was checked, and when carburetor heat was applied, a 100 RPM drop was noted. They departed 6B6 at approximately 0900 and headed West toward FIT. They approached FIT on a 45 degree downwind for Runway 32 for their first planned Touch and Go. As they turned onto the downwind leg, he noted that the engine briefly exhibited a hesitation. He applied the Carburetor Heat at that point, and kept it on until touchdown. After conducting a second Touch and Go he noted that after takeoff, the RPM was slowly dropping and the engine was rough. He stated that their altitude at the time was 100 feet above mean sea level (msl). The flight instructor then took the controls from him and applied carburetor heat, which made the engine roughness worse. The flight instructor "immediately" placed the Carburetor Heat to “Off” and pumped the throttle several times in an attempt to get the engine to smooth out. The student pilot then began looking for a place that they could attempt a landing and pointed out the dirt parking lot directly ahead of them, and then they banked to avoid a warehouse, and landed on some trees before settling to the ground. According to a witness, the airplane was observed at low altitude not much higher than the surrounding buildings. The engine was sputtering and also was much quieter than other airplanes that he had observed. Just prior to impact, the aircraft smoothly banked to the right and disappeared from his view. According to another witness who also observed the airplane, he heard the engine "sputtering", and "popping", and from his vantage point, he observed that it was in a nose high attitude, swaying from side to side, and "coming down fast" just prior to him hearing the sound of the airplane impacting the trees. PERSONNEL INFORMATION According to Federal Aviation Administration (FAA) and pilot records, the flight instructor held a commercial pilot certificate with ratings for airplane single-engine land, airplane multi-engine land and instrument airplane. He also held a flight instructor certificate with ratings for airplane single, airplane multi, and instrument airplane. His most recent FAA second-class medical certificate was issued on November 22, 2011. He reported 1,391 total hours of flight experience with 131 total hours in the accident airplane make and model. According to FAA and pilot records, the student pilot had accrued approximately 20 total hours of flight experience in the accident airplane. His most recent FAA third-class medical certificate was issued on June 17, 2010. AIRCRAFT INFORMATION The accident airplane was a two place, strut braced, high wing airplane of conventional metal construction. It was designed for flight training, air touring, and personal use. It was equipped with tricycle landing gear and powered by an air cooled, 100 horsepower, Continental O-200-A, engine, driving a fixed pitch propeller. According to the flight instructor, since his purchase of the airplane in August of 2011, he had a number of maintenance issues related to navigation, communication, the vacuum system, and the engine starter. He also advised that he had recent trouble with the carburetor heat sticking, and that the engine had been overhauled shortly before he had purchased the airplane. The student pilot stated that had not noted any major maintenance issues. He had added oil as needed during preflights. He indicated that early in his flight training, he was noting water in fuel sump samples that he took as part of his preflight activities. The flight instructor subsequently had the overwing fuel cap seals replaced which rectified the problem. He also stated that a radio had been missing from the panel for awhile, the attitude indicator at times was unresponsive, the vacuum system indicated low at times, and the left and right fuel tank quantity gauges did not indicate the fuel quantity that was visually observed in the fuel tanks. According to FAA and maintenance records, the airplane was manufactured in 1966. The airplane’s most recent annual inspection was completed on August 11, 2011. At the time of the inspection; the engine had accrued 105 hours of operation since major overhaul and the airplane had accrued 4,725.3 total hours of operation. On November 4, 2011, the carburetor airbox, valve shaft, and bearings, were replaced along with installation of a new carburetor heat cable. METEOROLOGICAL INFORMATION The recorded weather at FIT, at 0952, about 8 minutes prior to the accident, included: calm winds, 10 miles visibility, overcast clouds at 10,000 feet, temperature 0 degrees C, dew point - 04 degrees C, and an altimeter setting of 30.12 inches of mercury. The relative humidity was 72%. AIRPORT INFORMATION Fitchburg Municipal Airport was uncontrolled and had two runways configured in a 2/20 and 14/32 configuration. Runway 32 was asphalt, in good condition. It was marked with non-precision runway markings and total length was 4510 feet long and 100 feet wide. Obstructions existed off the departure end of 32 in the form of 50 foot high trees, 600 feet from the runway, 125 feet right of centerline, which took an 8:1 slope to clear. FLIGHT RECORDERS The airplane was not equipped with a flight recorder nor was it required to be under the CFRs. The student however had a Contour Nflightcam onboard which was capable of recording video and contained a built-in global positioning system (GPS) which was capable of recording speed, elevation, and distance. Examination of data captured from the accident flight revealed that no video or audio was recorded. However, the video did come on after the airplane struck trees and came to rest. According to the captured GPS data, the airplane touched down in the first 1/3rd of the runway at approximately 09:57:51. Then after passing midfield, the airplane became airborne once again and accelerated until reaching a peak recorded GPS altitude of 500 feet and a peak recorded groundspeed of approximately 56 knots. Shortly thereafter, the airplane began to decelerate and descend, and at 09:59:51 had decelerated to a ground speed of approximately 40 knots. Impact with the trees and ground occurred at approximately 10:00:03, and the airplane came to rest approximately 2,379 feet off the departure end of Runway 32. WRECKAGE AND IMPACT INFORMATION Examination of the accident site revealed that the aircraft came to rest in an upright position in a dirt parking lot, partially entangled in a hedgerow and trees. Further examination revealed that the airplane had impacted a number of approximately 20 foot high trees during the accident sequence, starting approximately 50 feet to the south of the accident site. No evidence of propeller strikes on the trees was discovered. Examination of the wreckage revealed no evidence of any preimpact failures or malfunctions of the airplane. The left and right wings had remained attached to their mounts but the empennage had been torn from the fuselage at a 45 degree angle to aircraft right, just aft of the passenger cabin rear bulkhead. All control cables and electrical harnesses contained in the empennage were intact, and the control cables all had continuity to their respective control surfaces. The left and right main landing gear assemblies were intact and the tires were in contact with the ground. The nose strut was folded under to the rear and was trapped under the cowling and fuselage. The engine mount tubing exhibited bending and breaking adjacent to the nose strut mounting point. The nose wheel assembly was located several feet aft of the right wingtip. The nose wheel axle, yoke and wheel collars were also located in the same general area. All tires were noted to be intact and holding pressure. Examination of the left wing revealed extensive structural damage to the outboard 4 to 5 feet of the wing consistent with striking the trees and hedgerow. The left trailing edge flap was positioned at approximately 5 degrees down. It exhibited heavy damage along the inboard 2 Ft of the trailing edge. Accordion buckling was noted at the same location. Fuel was noted to be intermittently dripping from the left wing fuel tank vent. When the aircraft was lifted to horizontal and placed on cribbing, the dripping stopped. A sample was taken from the fuel tank sump point. It was noted to be clear blue fluid consistent with 100LL aviation fuel. No sediment, water or other contaminants were noted. Examination of the right wing revealed that it had sustained impact damage to the leading edge starting at the lift strut and terminating near the wingtip. The wingtip exhibited a slight downward bend when viewed from the outboard end. The right aileron was free to travel on its hinges and did not exhibit continuity to either control yoke. There were multiple dents and wrinkles along the full length its trailing edge. The right wing flap was noted to be intact and was in the full up position. A sample was taken from the fuel tank sump point. It was noted to be clear blue fluid consistent with 100LL aviation fuel. No sediment, water or other contaminants were noted. Examination of the empennage indicated that the rudder was in the full right position and had only superficial damage to the lower edge and plastic upper fairing. The left horizontal stabilizer exhibited crush damage along the entire length of its leading edge. The right horizontal stabilizer as well as the left and right elevator had only superficial damage. Both elevators were free to move on their hinges and continuity was established to the break in the empennage at the aft cabin bulkhead. Examination of the cockpit revealed that the fuel selector was in the “OFF” detent position. The Fitchburg Fire Department Battalion Chief stated that the CFI had placed the selector to off at his request. Both cabin doors were found to be jammed in the full open position. Both sets of seat belts were noted to be intact. The left half of the forward windscreen was broken out and was discovered 10 Ft forward of the wreckage. It was noted that there was an opening in the instrument panel below the VHF/COMM which appears to be an opening mounting point for a second radio. A digital Contour NFlightCam, equipped with GPS, was located on the ground adjacent to the broken section of windscreen. Cockpit controls were noted to be in the following positions: • Ignition – OFF, Key missing • Master Switch – OFF • Throttle – 7/8 open • Mixture – Full Rich • Carburetor Heat – OFF • Navigation Lights – ON • Rotating Beacon – ON • Wing Flaps – Toggle switch found in Neutral position. • Elevator Trim – on the Takeoff Bug (Neutral). When actuated through their full range of motion, the left and right control yokes showed continuity with the elevator. Continuity with the ailerons could not be physically established however, visual examination of the aileron cables revealed that they had failed in tensile overload, and continuity could be established visually from the ailerons to the breaks in the cables, and from the breaks to the control wheels. Both sets of rudder pedals were found in the neutral position. Continuity with the rudder was confirmed. Propeller and Engine Examination Examination of the propeller and engine did not reveal any evidence of any preimpact mechanical malfunctions or anomalies. The propeller spinner and backing plate were intact. The cowling was found with superficial damage on the lower half, consistent with impact. One propeller blade had gouges and scratches on the outboard 10 inches of the leading edge at a 45 degree angle to the edge. The outboard 12 inches of the blade were smoothly folded forward without twisting. A slight leading edge twist was noted at the very tip. Chordwise scratching and mud splatter consistent with dragging on the ground were present at the bend. The other propeller blade was found folded forward at a 90 degree angle with “S” bending along the outboard 26 inches of the blade. Impact damage was noted at multiple places along this section of the blade, and chordwise mud splatter was evident on the rear of the blade. A small section on the tip leading edge was torn away. The oil level was found at the 6 Quart mark on the dipstick. The oil was clean and no visible signs of contamination were noted. All external engine components were intact, and the starter was no
A partial loss of engine power due to the formation of carburetor ice and the flight instructor's improper application of carburetor heat.
Source: NTSB Aviation Accident Database
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