The pilot of the Aeronca 7DC-CONV described a normal preflight inspection, engine start, run-up, taxi, departure, and climb to about 2,000 feet mean sea level from the airport in Fort Mills, South Carolina.
He initially established a heading toward his planned destination, but because of radio and airplane traffic at the destination airport, he amended his destination, and decided to descend and follow a river toward another airport.
The pilot told investigators that after descending about 1,000 feet, he leveled the airplane, “…applied power and there was no thrust.”
He adjusted the throttle, the mixture, “pulled the carb heat,” and cycled the magnetos without a change in engine speed. The engine continued to run at 1,000 rpm.
The pilot originally selected an open area of fields and golf courses for the forced landing, but decided to land in the river when he determined that the airplane would not reach the open area. The airplane touched down in shallow water, nosed over, and came to rest inverted.
The pilot and his passenger got out of the airplane safely with no injuries.
An examination of the airplane at the site revealed damage to the rudder, wing attachment points, and their associated attachment bolts. During recovery of the airplane, control continuity was established from the flight controls to all flight control surfaces.
The airplane was recovered to a facility and prepared for an engine test run. The impact-damaged propeller was removed, and a propeller of the same make and model was installed. The spark plugs were removed, and water was drained from the cylinders. The plugs were dried, cleared of debris, and reinstalled. The magneto timing was confirmed, and the magnetos were removed, dried, and reinstalled in their as-found positions.
The fuel line that ran between the fuel selector valve and the firewall beneath the instrument panel was fractured due to overstress, so a fuel container was plumbed into the carburetor for the test run.
A fresh battery was installed in the airplane, and the starter was excited using battery power. The engine started with fuel plumbed through the primer port of the carburetor, idled and accelerated smoothly, and ran continuously until the engine was stopped using the mixture control in the cockpit.
While the engine ran, a magneto check and a carburetor heat control check were performed satisfactorily at 1,700 rpm.
The engine was then restarted with fuel supplied through the main fuel supply port, and the tests were repeated satisfactorily. The engine was then accelerated into the “green arc” before it was stopped again using the mixture control.
According to the carburetor icing probability chart contained in FAA Special Airworthiness Information Bulletin (SAIB) CE-09-35, Carburetor Icing Prevention, the atmospheric conditions reported by the pilot at the point of departure and those recorded at a station about 10 miles west of the accident site were conducive to the development of carburetor icing at glide and cruise power.
In both his interview and his written statement, the pilot stated that he applied carburetor heat only after detecting the loss of engine power.
Probable Cause: The pilot’s failure to apply carburetor heat before initiating a descent in conditions conducive to the development of carburetor icing, which resulted in a partial loss of engine power due to carburetor ice.
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This May 2023 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
I found the article wrought with error.
1. How could the cylinders have water in them if the only points of entry remained above the water as the picture associated with this article shows.
2. How could the mag timing be checked first if they were later drained of water?
Poor writing.
I think that the lesson to be learned from this: If you have carb heat that pulls heated air from a “shroud” around an exhaust manifold or similar, use it BEFORE you pull power. Pulling power allows things to cool, so you will not get much warm air to the carb.
If on the other hand you have electric carb heat, maybe you should turn it on BEFORE pulling power, it may take it a bit to heat the carb.
One other lesson or item to try — Primer. If you can get gas into a cyl or two, it might fire and you might be able to get some carb heat to help finish clearing the carb.
BUT keep this in mind: The lower you go, the fewer the options you have as you trade what little bit of altitude you had for airspeed. Altitude gives you options. Sometimes enough that the engine will restart on its own (assuming the prop is windmilling as this one was).
One important lesson taught to me by my instructor while I flew C15x trainers. Get too low, and he’d pull power and say to me: “Lookie your engine just quit what are YOU going to do?”