N3090U

HISTORY OF FLIGHTOn August 2, 2021, about 1259 eastern standard time, a Cessna 172E, N3090U, was substantially damaged when it was involved in an accident in Waxhaw, North Carolina. The pilot and two passengers received minor injuries. The airplane was being operated as a Title 14 Code of Federal Regulations (CFR) Part 91 instructional flight.

The accident occurred during an aviation youth camp while taking off from runway 4, at JAARS-Townsend Airport (N52), Waxhaw, North Carolina. After rotation, just past the windsock located on the fence of the airport, the airplane became airborne and gained about 50 ft. The pilot maintained best rate of climb speed (80 mph), but the airplane failed to climb. He momentarily decreased the airspeed towards best angle of climb speed (65 mph), to see if the airplane would respond, but it did not, so he returned to the best rate of climb speed. He heard no abnormal sounds from the engine or any decrease in rpm during the takeoff run. Sensing that the airplane would not clear the trees beyond the departure end of the runway, he momentarily reduced power to idle to land on the remaining runway and overrun area. However, to avoid hitting the chain-link fence, he elected to add power and land on a lawn just beyond the airport. After adding enough power to reach the lawn, he reduced power to idle and touched down before the wooded area. On rollout, the airplane traveled towards a gap in the trees. The pilot turned left to avoid the trees, the airplane nosed over and came to rest nose down, leaning against a tree.

The pilot realized that he and the front seat passenger were hanging from their seatbelts, and he was concerned about the fuel that was leaking from the airplane. The rear seat passenger easily egressed and assisted the front seat passenger. The pilot’s pant leg was snagged between his seat and the instrument panel, so he grabbed the fabric and ripped it until he felt he was free, at which point he was able to egress. He then directed some campers away from the accident site, and a few minutes later returned to the airplane, to ensure that the master switch was off. To do so, he pulled the windscreen the rest of the way off the airplane.

According to witnesses, during the takeoff the angle of climb was much less than expected and the airplane never climbed above 10 to 20 ft above the runway. One of the witnesses reported the engine did not sound right. Several of the witnesses reported seeing the airplane bank to the right before they lost sight of it. One stated the airplane pitched down and rolled to the right, then pitched up and rolled to the left before impact. AIRCRAFT INFORMATIONReview of occupant weights and airplane weight and balance records indicated that the airplane was within weight and balance limitations during the takeoff. METEOROLOGICAL INFORMATIONThe recorded weather at Lancaster County Airport-McWhorter Field, located about 11 miles southwest of N52, at 1255, included: calm winds, 10 miles visibility, clear skies, temperature 29° C, dew point 18° C, and an altimeter setting of 30.03 inches of mercury.

Density altitude under these conditions was approximately 2,347 ft above mean sea level. AIRPORT INFORMATIONReview of occupant weights and airplane weight and balance records indicated that the airplane was within weight and balance limitations during the takeoff. WRECKAGE AND IMPACT INFORMATIONOn-Scene Examination

On-scene examination by a Federal Aviation Administration inspector revealed that the airplane touched down off the airport property on a gravel driveway, and a grassy area before an opening in the wooded area and then traveled about 600 ft before it had come to rest leaning against a tree, supported by the right wing (which was leaking fuel) in a nose-down, inverted position.

A debris path that started with the right wingtip led up to the main wreckage. The airplane’s left wingtip was found in a tree. The left horizontal stabilizer and elevator were separated from the fuselage, the aft fuselage was buckled, and small parts from the airplane were spread throughout the debris path, leading up to the main wreckage.

The nose landing gear displayed impact damage, one propeller blade was undamaged, and the other propeller blade was bent aft. The engine mounts were broken, the engine had shifted from its normal mounting position, and the fuel strainer was loose. The flight control cables were broken and parted.

National Transportation Safety Board (NTSB) Examination

Examination of the wreckage by the NTSB did not reveal any preimpact failures or malfunctions that would have precluded normal operation.

Examination of the cockpit revealed that the mixture control was in the full rich position, the throttle was in the full throttle position, and the carburetor heat control knob was not fully closed. Examination of the carburetor heat door also revealed that it was open. ADDITIONAL INFORMATIONDensity Altitude

When aircraft operate in a nonstandard atmosphere, the term density altitude is used for correlating aerodynamic performance in the nonstandard atmosphere.

According to the Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25C), density altitude is the vertical distance above sea level in the standard atmosphere at which a given density is to be found. The density of air has significant effects on the aircraft’s performance because as air becomes less dense, it reduces:

• Power because the engine takes in less air

• Thrust because a propeller is less efficient in thin air

• Lift because the thin air exerts less force on the airfoils

Density altitude is pressure altitude corrected for nonstandard temperature. As the density of the air increases (lower density altitude), aircraft performance increases; conversely as air density decreases (higher density altitude), aircraft performance decreases. A decrease in air density means a high-density altitude; an increase in air density means a lower density altitude. Density altitude is used in calculating aircraft performance because under standard atmospheric conditions, air at each level in the atmosphere not only has a specific density, its pressure altitude and density altitude identify the same level.

The computation of density altitude involves consideration of pressure (pressure altitude) and temperature. Since aircraft performance data at any level is based upon air density under standard day conditions, such performance data apply to air density levels that may not be identical with altimeter indications. Under conditions higher or lower than standard, these levels cannot be determined directly from the altimeter.

Density altitude is determined by first finding pressure altitude, and then correcting this altitude for nonstandard temperature variations. Since density varies directly with pressure and inversely with temperature, a given pressure altitude may exist for a wide range of temperatures by allowing the density to vary. However, a known density occurs for any one temperature and pressure altitude. The density of the air has a pronounced effect on aircraft and engine performance. Regardless of the actual altitude of the aircraft, it will perform as though it were operating at an altitude equal to the existing density altitude.

Air density is affected by changes in altitude, temperature, and humidity. High density altitude refers to thin air, while low density altitude refers to dense air. The conditions that result in a high-density altitude are high elevations, low atmospheric pressures, high temperatures, high humidity, or some combination of these factors. Lower elevations, high atmospheric pressure, low temperatures, and low humidity are more indicative of low-density altitude.

Carburetor Heat

According to the Aviation Maintenance Technician Handbook – Powerplant (FAA-H-8083-32B), carburetor heat is used in aircraft to prevent the formation of ice in the carburetor and carburetor normal flow air is admitted at the lower front nose cowling below the propeller spinner and is passed through an air filter into air ducts leading to the carburetor. A carburetor heat air valve is located below the carburetor for selecting an alternate warm air source (carburetor heat) to prevent carburetor icing. Carburetor icing occurs when the temperature is lowered in the throat of the carburetor and enough moisture is present to freeze and block the flow of air to the engine. The carburetor heat valve admits air from the outside air scoop for normal operation, and it admits warm air from the engine compartment for operation during icing conditions. The carburetor heat is operated by a push-pull control in the flight deck.

The carburetor air ducts consist of a fixed duct riveted to the nose cowling and a flexible duct between the fixed duct and the carburetor air valve housing. The carburetor air ducts normally provide a passage for outside air to the carburetor. Applying carburetor heat to an operating engine decreases the density of the air. Air enters the system through the ram-air intake. The intake opening is in the slipstream, so the air is forced into the induction system giving a ram effect to the incoming airflow. The air passes through the air ducts to the carburetor. The carburetor meters the fuel in proportion to the air and mixes the air with the correct amount of fuel. The throttle plate of the carburetor can be controlled from the flight deck to regulate the flow of air (manifold pressure), and in this way, power output of the engine can be controlled.

Improper or careless use of carburetor heat can be just as dangerous as the most advanced stage of induction system ice. Increasing the temperature of the air causes it to expand and decrease in density. This action reduces the weight of the charge delivered to the cylinder and causes a noticeable loss in power because of decreased volumetric efficiency. If icing is not present when carburetor heat or induction system anti-icing is...