ERA23FA370 · Ercoupe 415 C

The pilot owned the airplane and was flying it on a local flight with a passenger interested in buying it. About 2 to 3 minutes elapsed between engine startup and the application of takeoff power, which included the time spent taxiing for departure. A witness reported hearing the engine misfiring while the airplane was taxiing but stated that the engine sounded normal during the subsequent takeoff roll. The airplane departed and, after becoming airborne, it entered what a witness described as a “very shallow” climb before it disappeared from the witness’s view.

The passenger reported that the flight lasted about 3 to 5 minutes. He recalled feeling that the airplane “fell a little bit” and that the pilot said there was a wind gust and pulled back on the control yoke. The passenger recalled thinking that the airplane was too close to the tops of nearby trees. The next thing he recalled was waking up on the ground unable to move his legs; the passenger had not fastened the lap belt because he was unaware that the airplane was equipped with restraints.

Postaccident examination of the engine and its systems, including operational testing of the magnetos and spark plugs, revealed no evidence of preimpact failure or malfunction. However, the tachometer needle was trapped about 1,600 rpm, suggesting reduced engine power at the time of impact.

Although a witness reported that the engine sounded like it was misfiring when the airplane was taxiing for takeoff, there were no engine valvetrain issues were noted during the postaccident engine examination. Further, the passenger reported that he did not detect any change in engine sound between the application of takeoff power and the accident. Thus, it is unlikely that a stuck exhaust valve condition (which could result in misfiring) occurred after takeoff.

Although the carburetor bowl contained minimal fuel, the carburetor was impact-separated from the engine, and it is possible that some fuel could have leaked from the carburetor before the wreckage was recovered and the carburetor examined. The primer was found unlocked and partially extended; however, it could not be determined whether that condition existed before departure. Had the primer been unlocked during the entire flight, it was likely that the engine would have been operating with an excessively rich fuel to air ratio that would have been detectable by sooty spark plugs; a condition that was not evident during the postaccident engine examination.

The temperature and dew point at the time of the flight were conducive to the formation of “serious icing at glide [idle] power,” and evidence from the pilot’s cellular phone suggests that the pilot could have been aware of those conditions, having called the airport weather information number about 17 minutes before the accident. However, according to the passenger, the pilot did not perform an engine run-up or check or apply carburetor heat before takeoff. Thus, it is likely that, during taxiing operations, which are typically performed at low engine power settings, the carburetor accumulated ice. For an airplane equipped with a fixed-pitch propeller, carburetor ice formation results in reduced engine power.

Examination of the airplane found the carburetor heat control partially extended, which is indicative that the pilot likely recognized the partial loss of engine power and applied carburetor heat in flight; however, it could not be determined at what point in the flight the application of carburetor heat may have occurred. Regardless, it can take from about 30 seconds to several minutes for carburetor heat to melt an ice accumulation and fully restore engine power.

Based on the passenger’s report that the airplane felt like it “fell,” his observation that the pilot responded to the sink rate by pulling back on the control yoke, and the crush damage observed on the nose and wings of the airplane, it is likely that the pilot, while maneuvering the airplane over the residential area, failed to maintain the proper airspeed, which resulted in the exceedance of the airplane’s critical angle of attack and the airplane entering an aerodynamic stall or mush condition.

Further, although the fuel load at the start of the flight could not be determined, based on the reported weights of the pilot and passenger, any usable fuel amount greater than about 1.9 gallons would result in the airplane being over maximum gross weight.

At the time of the accident, the pilot did not possess current FAA medical certification or BasicMed qualifications. The pilot had medical conditions including seizure disorder and severe heart disease that placed him at increased risk for an impairing or incapacitating medical event. Although such an event may not leave reliable autopsy evidence if it occurs just before death, there was no autopsy evidence that such an event occurred, and the surviving passenger’s account did not indicate pilot incapacitation. The pilot’s hemoglobin A1c (HbA1c) indicated marginal long-term control of his diabetes. Based on his high urine glucose, his blood sugar may have been elevated at the time of the accident. Based on his vitreous glucose and his witnessed behavior, it is unlikely that he was experiencing major metabolic disturbance related to high blood sugar at the time of the crash. It also is unlikely that he was experiencing severe low blood sugar at the time of the accident. Diabetes symptoms such as fatigue and blurry vision cannot be excluded based on available medical evidence. The pilot’s medical conditions (including cardiovascular disease and possibly the condition being treated with citalopram) and use of medication (including levetiracetam) also were associated with increased risk of impaired cognitive and psychomotor performance. However, the extent to which the pilot’s medical conditions and their related treatment may have been significant is not clear from the available medical evidence and accident circumstances. Overall, the pilot was at increased medical risk of impairment, but there is no specific evidence that a medical factor contributed to the accident.

Verbatim NTSB analysis and probable cause from the NTSB dataset