Greenville, ME, USA
N9932V
CESSNA 172M
On the morning of the accident, the airplane was observed circling at low altitude in a left turn about 1 mile southwest of the departure airport with the pilot visibly waving at people on the ground. During the third and last circle, the airplane pitched nose up, decelerated, then pitched nose down steeply and descended toward the ground. The airplane then rotated to the left with its nose still pointed down, turned about 180 degrees from its original direction of travel, then disappeared from view. Moments later the sound of an impact was heard. Postaccident examination of the airplane and engine did not reveal any evidence of preimpact malfunctions or failures that would have precluded normal operation. Toxicological testing of the pilot revealed the presence of carbon monoxide in his blood; however, the carbon monoxide level was consistent with a heavy smoking habit. Tetrahydrocannabinol (THC) (marijuana) was also detected in his lungs but not in his blood, and THC corboxylic acid was detected in his urine, liver, and lungs. However, the THC findings were consistent with a remote usage of marijuana (that is, not immediately before flight), and the absence of THC in his blood indicated that the pilot was likely not impaired. Download of a portable GPS discovered in the wreckage confirmed the witness' observations of the airplane’s flightpath and that the pilot was maneuvering at low altitude (less than 500 feet above ground level) when the airplane decelerated below its aerodynamic stall speed and entered a spin. Review of manufacturer's published data indicated that altitude loss during a stall recovery could be as much as 250 feet, and 1,000 feet of altitude loss for a one-turn spin and recovery could be expected.
HISTORY OF FLIGHT On September 17, 2011, about 0813 eastern daylight time, a Cessna 172M, N9932V, was substantially damaged when it impacted terrain following a loss of control while maneuvering near Greenville, Maine. The certificated private pilot was fatally injured. Visual meteorological conditions prevailed, and no flight plan was filed, for the local personal flight conducted under 14 Code of Federal Regulations (CFR) Part 91, that departed Greenville Municipal Airport (3B1), Greenville, Maine. On the evening before the accident, the pilot had a conversation with a friend. During the conversation his friend advised him that he had bought some property near the airport and would be clearing away some of the vegetation on the following day. The pilot advised him that he would fly out in the morning and visit him. According to witnesses, on the morning of the accident, the airplane was observed circling at low altitude in a left hand turn about 1 mile southwest of (3B1), with the pilot visibly waving at people on the ground. During the third and last circle, the airplane was observed to pitch nose up, decelerate, then pitch nose down steeply and descend towards the ground. The airplane then rotated to the left with its nose still pointed down, turned approximately 180 degrees from its original direction of travel, then disappeared from view. Moments later the sound of an impact was heard. PERSONNEL INFORMATION According to Federal Aviation Administration (FAA) records, the pilot held a private pilot certificate with a rating for airplane single-engine land. He had been involved in a previous accident which had occurred on October 20, 2007(NTSB accident number NYC08CA017) when he struck several tree tops while performing touch and go landings at night and then landed hard on the runway substantially damaging the Cessna 152 which he had been flying. His most recent FAA third-class medical certificate was issued on May 17, 2011. According to pilot records, he had accrued 2,310.7 total hours of flight experience. AIRCRAFT INFORMATION The accident aircraft was a four-seat, single-engine, strut braced, high-wing airplane of conventional metal construction. It was equipped with non-retractable tricycle landing gear and was powered by a carbureted, 150 horsepower, Lycoming O-320-E2D, 4-cylinder, air cooled engine. It was certificated in the normal and utility category and was equipped for operations in instrument meteorological conditions. It was equipped with a stall warning system and its instrument panel was designed around the basic "T" configuration. The attitude indicator and directional indicator were located immediately in front of the pilot, and were arranged vertically with the attitude indicator on top. The airspeed indicator and altimeter were located to the left and right of the attitude indicator, respectively. A turn and bank indicator was also installed and was mounted to the left of the directional indicator. According to FAA and maintenance records, the airplane was manufactured in 1974. The airplane’s most recent annual inspection was completed on March 30, 2011. At the time of the accident, the airplane had accrued 6499 total hours of operation. METEOROLOGICAL INFORMATION The recorded weather at 3B1, at 0756, included: variable winds at 4 knots, temperature 8 degrees C, dew point 3 degrees C, and an altimeter setting of 30.35 inches of mercury. Visibility and sky conditions were missing from the automated report however witnesses reported no obstructions to visibility at the time of the accident. WRECKAGE AND IMPACT INFORMATION Examination of the accident site and wreckage revealed no evidence of any preimpact failure or malfunction of the airplane or engine. During the impact sequence the airplane came into contact with several trees about 20 feet above ground level before impacting in an approximate 35 degree nose down attitude in a heavily wooded area. Examination of the accident site revealed that a 15 foot wide and 45 foot long wreckage path existed, which began at the first tree strike and was oriented on a magnetic heading of 225 degrees. Examination of the wreckage revealed that all of the major components of the airplane were present. The fuselage, exhibited multiple areas of crush and compression damage. The right wing had separated from its mounting location and was fragmented into two sections and the left wing was folded back at an approximate 45 degree angle. Both fuel caps were closed. Control continuity was established for all of the flight controls to the breaks in the cables which made up the system, and which exhibited evidence of tensile overload. The wing flaps were up. The throttle control was 3/4 open, and the mixture control was full rich. The cabin doors latching assemblies were in the closed and locked position. Examination of the propeller and engine revealed evidence of a broken prop tip, s-bending, and leading edge gouging on one blade, and chordwise scratching on the other. Drive train continuity was confirmed throughout the engine and thumb compression was evident on all cylinders. Oil was present in the rocker boxes. The spark plugs appeared normal and were light gray in color. Both magnetos would produce spark at all towers. The carburetor fuel strainer was clean and free of debris. The main discharge nozzle appeared normal, and the float assembly was functional. The needle valve was functional, and fuel was present in the float bowl. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy was performed on the pilot by the Office of the Chief Medical Examiner, State of Maine. Cause of death was multiple blunt force trauma. Toxicological testing of the pilot was conducted at the FAA Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma. The pilot's forensic toxicology report revealed: " >> 12 (%) CARBON MONOXIDE detected in Blood >> 14.46 (ug/ml, ug/g) Acetaminophen detected in Urine >> Cotinine detected in Urine >> Cotinine detected in Blood >> Ibuprofen detected in Urine >> Nicotine detected in Urine >> Nicotine detected in Blood >> 1.0809 (ug/ml, ug/g) Tetrahydrocannabinol (Marihuana) detected in Lung >> Tetrahydrocannabinol (Marihuana) NOT detected in Blood >> 0.0125 (ug/ml, ug/g) Tetrahydrocannabinol Carboxylic Acid (Marihuana) detected in Urine >> 0.0094 (ug/ml, ug/g) Tetrahydrocannabinol Carboxylic Acid (Marihuana) detected in Liver >> Tetrahydrocannabinol Carboxylic Acid (Marihuana) detected in Lung >> Tetrahydrocannabinol Carboxylic Acid (Marihuana) NOT detected in Blood" TESTS AND RESEARCH During the wreckage examination, the remains of a Garmin GPSMAP 496 portable global positioning system (GPS) navigation receiver was discovered in the wreckage. Download of the unit by the NTSB's recorders laboratory revealed that data from the accident flight had been captured and stored by the unit. Review of the data revealed that the flight path correlated to the witness descriptions of the event and just prior to the accident and at 08:12:44 the airplane was at a GPS altitude of 1,661 feet and a groundspeed of 62 miles per hour (MPH). Two seconds later, at 08:12:46, the airplane was at a GPS altitude of 1,522 feet (452 feet above ground level) and had decelerated to 51 MPH. According to the Cessna 172M Owner's Manual; stall speed, power off, at 2,300 pounds (maximum gross weight) with an aft center of gravity was 57 mph. Comparison of the recorded data with published data for a similar model airplane revealed that altitude loss during stall recovery could be as much as 250 feet and at least a 1,000 feet of altitude loss should be allowed for a one-turn spin and recovery. Uncoordinated Flight According to the pilot's flight instructor, the pilot would sometimes fly in an uncoordinated manner especially during steep turns where the ball in the instrument mounted turn and bank indicator (turn coordinator) would sometimes be "1/2 ball out", indicating that the airplane was slipping (in a sideslip) or skidding (yawing). Airspeed Control According to Cessna's Pilot Safety and Warning Supplements, flying other than published airspeeds could put the pilot and airplane in an unsafe situation. The airspeeds published in the airplane's operating handbook had been tested and proven to help prevent unusual situations. The document also advised that the pilot should be familiar with the stall characteristics of the airplane when stalled from a normal 1G stall and advised that any airplane can be stalled at any speed. Stall Warning System The airplane was equipped with a stall warning system. An aural warning was provided by a pneumatic type stall warning system. The system consisted of an inlet in the leading edge of the left wing, an air-operated horn near the upper left corner of the windshield, and associated plumbing. As the airplane would approach a stall, the low pressure on the upper surface of the wing would move forward around the leading edge of the wings. This low pressure would create a differential pressure in the stall warning system, which would draw air through the warning horn, and would result in an audible warning between 5 to 10 miles per hour above the stall in all configurations. Stalls and Stall Recovery According to the FAA, a stall occurs when smooth airflow over the airplane's wing is disrupted, and the lift degenerates rapidly. This is caused when the wing exceeds its critical angle of attack (AOA). This can occur at any airspeed, in any attitude, with any power setting. If recovery from a stall is not achieved in a timely and appropriate manner by reducing the AOA, a secondary stall/and or spin may result. All spins are preceded by a stall on at least part of the wing. The key factor in recovering from a stall is regaining positive control of the aircraft by reducing the AOA. At first indication of a stall the airplane AOA must be decreased to allow the wings to regain lift. The next step in recovering from a stall is to smoothly apply maximum allowable power to increase airspeed and to minimize the loss of altitude. Spins According to the FAA, a spin may be defined as an aggravated stall that results in what is termed "autorotation" wherein the airplane follows a downward corkscrew path. As the airplane rotates around a vertical axis the rising wing is less stalled than the descending wing creating a rolling, yawing, and pitching motion. The airplane is basically being forced down by gravity, rolling, yawing, and pitching in a spiral path. The spin is caused when the airplane’s wing exceeds its critical angle of attack (stall) with a sideslip or yaw acting on the airplane at, or beyond, the actual stall. During this uncoordinated maneuver, a pilot may not be aware that a critical angle of attack has been exceeded until the airplane yaws out of control toward the lowering wing. If stall recovery is not initiated immediately, the airplane may enter a spin. If this stall occurs while the airplane is in a slipping or skidding turn, this can result in a spin entry and rotation in the direction that the rudder is being applied, regardless of which wingtip is raised. According to the Cessna 172M Owner's Manual, the stall characteristics of the airplane were conventional and the airplane was inherently resistant to spins. To perform an intentional clean entry into a spin for training or practice, the airplane would need to be decelerated at a faster rate than is used for stalls. Then just as the stall occurred, full up elevator, full rudder in the desired spin direction, and momentary full engine power would need to be applied. As the airplane would begin to enter the spin, power would need to be reduced to idle and full pro-spin elevator and rudder deflections would need to be maintained, and the application of ailerons in the direction of the spin would also help to obtain a clean spin entry. During extended spins of two to three turns or more, the spin would tend to change into a spiral, particularly to the right. This would be accompanied by an increase in airspeed and gravity loads on the airplane. If this occurred the manual cautioned that recovery should be accomplished quickly by leveling the wings and recovering from the resulting dive. The manual also advised that to recover from an intentional or inadvertent spin, to: 1. Retard the throttle to the idle position. 2. Apply full rudder opposite the direction of rotation. 3. After one-fourth turn, move the control wheel forward of neutral in a brisk motion. 4. As the rotation stops, neutralize the rudder, and make a smooth recovery from the resulting dive. ADDITIONAL INFORMATION According to the NTSB aircraft accident data, while a higher proportion of weather accidents are fatal, more fatal accidents occur in maneuvering flight than any other pilot-related category. Some of the accident maneuvers (such as turns in the airport traffic pattern) were necessary but poorly executed. Others were risky activities like buzzing attempts, low-altitude night flights, or attempted aerobatics by untrained pilots and/or in unapproved aircraft. Most were initiated at low altitudes, giving the pilots little time or room to respond if anything went wrong. More than half began with stalls or other losses of aircraft control at altitudes too low to allow recovery indicating that these accidents were indicative of poor judgment, than lack of knowledge or skill. Three-quarters of these accidents were fatal.
The pilot's failure to maintain adequate airspeed while manuevering at low altitude, which resulted in an aerodynamic stall/spin and subsequent impact with terrain.
Source: NTSB Aviation Accident Database
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