Harveysburg, OH, USA
N9588E
AERONCA 11AC
Before departing on an instructional flight with a new student, the flight instructor added 10 gallons of automotive premium 93 octane fuel that contained ethanol to the airplane, which had a supplemental type certificate (STC) to be able to use automotive fuel. The instructor conducted the takeoff and initial climb to 2,500 ft mean sea level (msl). Once established, the instructor let the student handle the flight controls and instructed the student to maintain their heading but to continue to climb to 3,000 ft msl. After practicing some basic flight maneuvers, the instructor had the student fly straight and level about 2,500 ft msl over a lake. While they were roughly over the center of the lake, the engine sustained a “severe loss of power.” The instructor immediately took the controls and established best glide airspeed. He observed the oil temperature and pressure gauges to be normal. The fuel quantity gauge was still indicating full. He worked the throttle in and out but without effect. He then pulled the carburetor heat to on, but the propeller continued to windmill under no power. The lake was surrounded by high, dense trees, so he elected to conduct a forced landing to the water. During landing the airplane nosed over, resulting in substantial damage to the airplane. The instructor and student were uninjured and were able to exit the airplane and walk to shore. The postaccident examination of the airplane and engine did not reveal any evidence of preimpact failures or malfunctions that would have precluded normal operation. A review of a carburetor icing probability chart indicated that meteorological conditions at the time of the accident were conducive to carburetor icing at glide and cruise power. Guidance published by the automotive fuel-use STC holder advised that automotive fuel containing ethanol should not be used in the airplane as, among other things, ethanol can absorb significant amounts of water in flight, and has an affinity for water and can pull moisture from inlet air on humid days to such extent that the engine may malfunction. Furthermore, carburetor icing is likely to occur at higher ambient temperatures, and at lower humidity with automotive fuel than with aviation fuel. The flight instructor did not know that he should not have been using automobile gasoline that contained ethanol. Thus, the evidence in this case indicates that in addition to not using fuel containing ethanol, the flight instructor should have responded to the carburetor icing by applying full carburetor heat immediately, instead of applying it after the engine had stopped producing power, as the carburetor heat system needed hot air from the exhaust manifold while the engine was running to function properly. He also could have recognized the potential for the formation of carburetor ice and preemptively activated it to prevent the formation of carburetor ice. Therefore, it is likely the engine sustained a complete loss of engine power due to the formation of carburetor ice.
On March 16, 2022, about 1556 eastern daylight time, an Aeronca 11AC, N9588E, was substantially damaged when it was involved in an accident near Harveysburg, Ohio. The pilot and passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. According to the instructor, before the flight he met with his new student at his hangar at Warren County Airport / John Lane Field (I68), Lebanon, Ohio. They spoke briefly about what they wanted to accomplish for the instructional flight, mostly aircraft familiarization and basic control coordination skills. They conducted a preflight inspection as part of the instruction given. The airplane had flown twice (about 3.7 hours) just before the accident flight. The instructor added 10 gallons of automotive premium 93 octane fuel that contained ethanol to the airplane, which had a supplemental type certificate (STC) to be able to use automotive fuel. The fuel was screen-filtered through a funnel when added. They also confirmed that the oil level was at the specified 4-quart level, and the instructor showed the student how to sample the fuel and confirmed that there was no water or debris in the sample. All other inspections of the aircraft indicated it was ready for another flight. Once onboard, the instructor had him practice ground handling techniques with rudder and brake usage. After conducting about 10 minutes of ground handling instruction around the ramp, they proceeded to the designated run-up area on the south ramp at I68. Using the “CIGAR” checklist, the instructor conducted the run-up while talking about each letter in the acronym (Controls, Instruments, Gas, Airplane, Run-up) and what they were looking for with each. All checks indicated the aircraft was ready for flight. They then proceeded to runway 19 and departed about 1500. The instructor conducted the takeoff and initial climb to 2,500 ft msl with an east bound turn out. Once established, the instructor let the student handle the flight controls, and asked him to maintain their heading but to continue to climb to 3,000 ft msl. Once they were at 3,000 ft msl, the instructor began to give him instruction in basic flight maneuvers including shallow coordinated turns. After several maneuvers they had descended back to 2,500 ft msl but the instructor determined their altitude to still be safe for their operations. They then flew straight and level so the student could have a short break and observe the surrounding area as they entered the class E airspace around and above Caesars Creek Lake. While they were roughly over the center of the lake the engine sustained a “severe loss of power.” The instructor immediately took the controls while trying to diagnose the problem. He quickly pitched for 55-60 mph, the published best glide speed. He observed the oil temperature and pressure gauges to be normal just before and after the power loss. The fuel quantity gauge was still indicating “F” (Full). He worked the throttle in and out but without effect. He then pulled the carburetor heat to on. The propeller continued to windmill under no power. When the instructor realized the engine “wasn't coming back,” he had to decide where to put the plane down as Caesars Creek Lake was surrounded by a high, dense tree line. He quickly observed that their glidepath would not permit them to fly beyond the tree line in any direction. The instructor thought that they could either land on top of the trees, which was a long way down if the airplane did not stay on top, or he could nose the airplane into the tree line in hopes of tearing the wings off, but not directly impact the fuselage. These options seemed far too risky, with certain catastrophic damage, so he chose to fly as close to the bank as possible without impacting the tree line with their right wingtip. He instructed the student to hold on to the upright steel tubing of the fuselage, to brace himself for the impact with the water, and to expect the plane to flip over upon impact. Then, as they were gliding only a few feet over the water, he held the airplane off the surface until he could bleed off all excessive airspeed gained in the descent. Once they were at a minimum controllable airspeed, inches off the surface, he pulled back on the stick in hopes of dragging the tailwheel through the water to reduce the forward momentum, hoping to reduce the risk of flipping over. However, as soon as the main wheels impacted the water, the airplane nosed over and stopped, resting on the leading edge of the wing, windscreen, propeller, and spinner, and resulting in substantial damage to the airplane. The instructor then directed the student to exit the airplane and get to the lake shore. After they both exited, they waded through waist-high water to shore safely and without injury. The pilot called 911. The dispatcher confirmed their location and rescue arrived about 15 minutes later. An Ohio Department of Natural Resources boat picked them up and transferred them into the care of local medical services. Both the pilot and the student declined further medical aid and the Ohio State Highway Patrol drove them to a marina to be picked up by their own transportation. The postaccident examination of the airplane and engine did not reveal any evidence of preimpact failures or malfunctions that would have precluded normal operation. Examination of Federal Aviation Administration (FAA) records showed that the airplane and engine had an STC for the use of automobile gasoline. When asked, the flight instructor did not know that he should not be using premium automobile gasoline that contained ethanol, and further examination of the airplane revealed that the placards which were required to be installed as part of the STC were not present. According to the STC holder, ethanol should not be used in the airplane, and pilots should revert to 100LL aviation fuel if ethanol-free gasoline cannot be found. The STC holder also advised that: o Ethanol fuels can damage the rubber and aluminum components of an aircraft fuel system. o Ethanol increases the volatility of fuel. o Ethanol can absorb significant amounts of water in flight. o Ethanol may vent off at altitude, reducing both range and octane. The STC holder further advised that ethanol has an affinity for water and can pull moisture from inlet air on humid days to such extent that the engine may malfunction, and allowing gasoline with ethanol to remain in the airplane for extended periods of time has resulted in the need to replace carburetors, hoses, and gaskets. It has also been reported to clean the interior of fuel tanks, leaving the accumulated sludge in the fuel screen. According to Transport Canada TP 10737 (Use of Automotive Gasoline [Mogas] in Aviation), fuels containing alcohol (methanol or ethanol) other than de-icing fluids are not permitted for use in aircraft. Alcohol can attack some seal and fuel system rubbers and plastics, resulting in potentially serious damage. Furthermore, alcohol and water will mix, and ethanol may separate from gasoline. Since it is not required of fuel suppliers to indicate the presence of alcohol in gasoline, it is the responsibility of the pilot to ascertain its presence. It also stated that Mogas is generally higher in volatility than Avgas. Mogas will thus absorb more heat from the mixing air when vaporizing, resulting in ice accumulation at higher ambient temperatures. It goes on to say that “THE LIKELIHOOD OF CARB ICING WHILE FLYING ON MOGAS IS HIGHER”, and advises that, “Although the severity of the carb icing and the methods to deal with it are similar for both Avgas and Mogas, its ONSET is likely to occur at HIGHER AMBIENT TEMPERATURES and at LOWER HUMIDITY with Mogas. In other words, conditions under which a pilot may feel there is only a slight risk for carb icing on Avgas may in fact be ideal for the formation of ice while using more volatile Mogas. This will result in the need to select ‘carb heat on’ in less severe icing conditions and for a longer duration while using Mogas.” Review of a carburetor icing probability chart indicated that meteorological conditions that existed at the time of the accident were conducive to carburetor icing at glide and cruise power. According to FAA Special Airworthiness Information Bulletin CE-09-35 (Carburetor Ice Prevention), pilots should be aware that carburetor icing doesn’t just occur in freezing conditions: it can occur at temperatures well above freezing temperatures when there is visible moisture or high humidity. Icing can occur in the carburetor at temperatures above freezing because vaporization of fuel, combined with the expansion of air as it flows through the carburetor (Venturi effect), 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. The bulletin goes on to say, in part, that there are some steps a pilot can take to prevent, recognize, and respond to carburetor icing. To prevent carburetor icing, the pilot should: o Assure the proper functionality of the carburetor heat during the ground (Before Takeoff) check. o Use carburetor heat on approach and descent when operating at low power settings, or in conditions where carburetor icing is probable. To recognize carburetor icing, the warning signs are: o A drop in rpm in fixed pitch propeller airplanes. o A drop in manifold pressure in constant speed propeller airplanes. o In both types, usually there will be a roughness in engine operation. The pilot should respond to carburetor icing by applying full carburetor heat immediately. The engine may run rough initially for short time while ice melts. The above recommendations are general suggestions. The pilot should consult the airplane flight manual or the pilot's operating handbook for the proper use of carburetor heat.
A complete loss of engine power as a result of carburetor ice due to the flight instructor’s failure to effectively use carburetor heat in conditions conducive to the formation of carburetor ice.
Source: NTSB Aviation Accident Database
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