ERA25LA127

During a solo cross-country flight, the student pilot initiated a cruise-power descent from about 2,300 ft and about 2300 rpm (about 65% engine power). He reported that, when the airplane was about 1,500 ft, it felt like the engine was “pulled to idle.” He stated that he manipulated the throttle control, but the engine did not respond. He confirmed that the mixture control was set to full rich, the fuel selector was in the Both position, and the primer was locked. He said he then applied carburetor heat, which had “no effect,” then he removed carburetor heat and looked for a place to land the airplane. The student pilot selected a road for a forced landing, and the airplane’s right wing impacted trees about 10 ft above the surface and the airplane continued striking trees after ground contact. The airplane came to rest upright on its nose against trees on the side of a two-lane road. An odor of fuel was present at the site, but the contents of the fuel tanks could not be established due to the airplane’s position. Examination of the airframe and engine found no abnormality that would have prevented normal operation. A serviceable propeller was installed, and an engine start was initiated on a test stand. The engine started immediately, then idled, accelerated, and ran smoothly at full power for several minutes without interruption and no anomaly noted. A magneto check was performed with no anomaly noted, and oil indicated pressures were in the normal range. Engine power was reduced to idle, where the engine ran smoothly without interruption. A magneto grounding check was normal, and a slight rpm rise was heard when the mixture was pulled to idle cutoff. The engine was stopped with the mixture placed at the idle cutoff position. A post-run inspection of the engine revealed no leaks and no abnormality. The atmospheric conditions near the accident site around the time of the accident were conducive to the formation of carburetor icing at glide and cruise power settings. Given the atmospheric conditions and the lack of mechanical anomalies found during postaccident examination and an engine test run, the engine likely lost power due to the accumulation of carburetor icing during the en route descent. Although the student pilot’s subsequent brief (rather than sustained) application of carburetor heat was inconsistent with the emergency procedures for responding to a loss of engine power, this likely did not affect the outcome of the flight. Given the airplane’s low altitude when the student first perceived the engine power anomaly, it is unlikely that carburetor heat applied in response could have cleared the ice and restored engine power in time to prevent the forced landing.

According to the FAA Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25C): It is imperative for a pilot to recognize carburetor ice when it forms during flight to prevent a loss in power, altitude, and/or airspeed. These symptoms may sometimes be accompanied by vibration or engine roughness. Once a power loss is noticed, immediate action should be taken to eliminate ice already formed in the carburetor and to prevent further ice formation. This is accomplished by applying full carburetor heat, which will further reduce engine power and may cause engine roughness as melted ice goes through the engine. These symptoms may last from 30 seconds to several minutes, depending on the severity of the icing. During this period, the pilot must resist the temptation to decrease the carburetor heat usage. Carburetor heat must remain in the full-hot position until normal power returns. The airplane was manufactured in 1980 and was powered by a Lycoming O-360-A4M 180-horsepower engine. Its most recent 100-hour inspection was completed December 13, 2024, at 9,986.0 total aircraft hours. The tachometer showed 10,080.6 total aircraft hours at the accident site. According to the Cessna 172P pilot’s operating handbook (POH), the engine cruise power normal operating range (tachometer green arc) at sea level was defined as 2100 to 2450 rpm. The POH’s amplified normal procedures for Cruise flight stated, in part, the following: Carburetor ice, as evidenced by an unexplained drop in rpm, can be removed by application of full carburetor heat. Upon regaining the original rpm (with heat off), use the minimum amount of heat (by trial and error) to prevent ice from forming. The POH’s Descent checklist stated the following: o Fuel selector valve – Both o Mixture – Adjust for smooth operation (full rich for idle power) o Power – As desired o Carburetor heat – Full heat as required (to prevent carburetor icing) The POH’s Before Landing checklist included the checklist item, “Carburetor heat – on (apply full heat before reducing power).” The amplified normal procedures for Normal Landing contained a note stating, “Carburetor heat should be applied prior to any significant reduction or closing of the throttle.” The POH’s Engine Failure During Flight checklist stated the following: o Airspeed – 65 kts indicated airspeed o Carburetor heat – On o Fuel selector valve – Both o Mixture – Rich o Ignition switch – Both (or start if propeller is stopped) o Primer – In and locked On February 22, 2025, at 1545 eastern standard time, a Cessna 172P, N781FM, was substantially damaged when it was involved in an accident near Mayo, Maryland. The student pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 solo instructional flight. The student pilot reported that he departed Delaware Airpark (33N), Dover, Delaware, at 1512, enroute to Tipton Airport (FME), Odenton, Maryland. ADS-B flight track information showed that the airplanereached the mouth of the Chester River about 2,300 ft when it began a gradual descent in a cruise profile. The airplane crossed the river mouth to the northern tip of Kent Island, where the descent continued. About 1536, the airplane turned and paralleled the Chesapeake Bay Bridge about 1,800 ft as it turned westbound over the Chesapeake Bay. Before it reached the bay’s western shore, the airplane turned southwest and paralleled the shoreline as it entered a gradual descent abeam Hackett Point, Maryland. According to the student pilot, he maintained cruise engine power about 2300 rpm throughout the en route descent to fly below the overlying class B airspace and proceed to a nearby practice area. About 1543, while the airplane was about 1,500 ft, the airplane experienced a sudden total loss of engine power. According to the student pilot, it felt like the engine was “pulled to idle.” The air traffic controller offered an airport 3 miles west of the airplane’s position as a potential forced landing location, but the airplane’s altitude was less than 1,000 ft. The student pilot stated that he manipulated the throttle control, but the engine did not respond. He confirmed that the mixture control was set to full rich, the fuel selector was in the Both position, and the primer was locked. He said he then “pulled the carb heat with no effect and pushed it back in,” then looked for a place to land the airplane. The student pilot selected a road for the forced landing, and the right wing impacted trees about 10 ft above the surface. The airplane continued striking trees after ground contact and came to rest upright against trees off the side of the road. The student pilot egressed the airplane without assistance. According to the FAA Carburetor Icing Probability Chart, the atmospheric conditions reported at the time of the accident were conducive to the formation of carburetor icing at “glide or cruise power.” The student pilot’s flight instructor calculated that 2,300 rpm equated to 65% power in the accident airplane. The student pilot was issued an FAA first-class medical certificate February 29, 2024. He reported 71.8 total hours of flight experience, 46.6 hours of which was in the accident airplane make and model. Initial examination of the at the accident site revealed that the airplane rested upright on its nose and against trees in a drainage swale on the side of a two-lane road. An odor of fuel was present, but the contents of the fuel tanks could not be established due to the airplane’s position. Both wings were substantially damaged. The cockpit, cabin area, empennage, and tail section appeared largely intact. The engine was still attached but displaced from its mounts. The fuel boost pump switch was found in the “on” position. The airplane was photographed and then recovered, first to a local airport, and then to a secure storage facility. During recovery from the airport, flight control continuity was established from the cockpit to allflight control surfaces. Aileron continuity was established from the control yoke to cuts made during initial recovery, and from the cuts to the ailerons. Examination of the engine found no abnormality that would have prevented normal operation. The engine fuel system was intact. The fuel pump remained secured to the accessory housing and was undamaged. There was no damage to primer lines or the carburetor, and the throttle and mixture arms moved freely through their full range of travel. The carburetor air box was partially crushed with the carburetor heat valve seized in the mostly open position. To facilitate an engine test run, the engine controls were disconnected, the damaged propeller was removed, and the engine was removed from the airframe and placed in a test stand. A serviceable propeller was installed, and an engine start was initiated on the test stand. The engine started immediately, then idled, accelerated, and ran smoothly at full power for several minutes without interruption and no anomaly noted. A magneto check was performed with no anomaly noted, and indicated oil pressures were in the normal range. Engine power was reduced to idle, and the engine ran smoothly without interruption and with no anomaly noted. Magneto grounding check was normal, and a slight rpm rise was heard when mixture was pulled to idle-cutoff. The engine was stopped with the mixture placed at the idle-cutoff position. A postrun examination of the engine revealed no leaks and no abnormality.