The pilot told investigators that while taking off from his private dirt strip near Powell, Wyoming, the Kitfox’s engine began to sputter and lost partial power about halfway down the runway.
He confirmed the boost pump was on and proceeded with the takeoff since there was an irrigation canal at the end of the runway. The airplane would not gain altitude and hit two fences before nosing over and coming to rest inverted in a neighbor’s yard.
The right wing sustained substantial damage during the accident.
A post-accident examination of the Rotax 582 engine revealed that it was equipped with two piston-type carburetors. On the carburetor near the magneto (MAG carburetor), the retaining clip for the jet needle was set to the No. 1 position (most lean). On the carburetor near the gear box/propeller (power takeoff carburetor), the retaining clip for the jet needle was set to the No. 3 position.
The jet needles had four positions in which the retaining clip would seat. The No. 1 position was near the top of the needle and was the leanest setting; the subsequent three positions were equally spaced below the No. 1 position, ending with the No. 4 position at the lowest position. The No. 3 position of the retaining clip for the jet needle was the position set when manufactured, according to the representative of the engine manufacturer.
The Rotax Maintenance Manual specified that, when installing the carburetor, press the needle clip in the same position as recorded. The Maintenance Manual Line for the engine states, “the needle jet and jet needle must only be exchanged by a mechanic with experience on two-stroke engines and in accordance with the Maintenance Manual Heavy.” Furthermore, the Illustrated Parts Catalog for the engine listed the carburetor calibration as needle position 3.
Both carburetor pistons slides were observed to have scoring marks consistent with the carburetors not being synchronized. Additionally, the engine’s maintenance manual lists a rough running engine as being caused by incorrect synchronization of the carburetors.
According to the pilot, he adjusted the carburetor retaining clip to lower the front cylinder temperature that was running high. The adjustment slightly lowered the cylinder temperature and he noticed no performance loss while flying multiple flights in Arizona.
The takeoff on the accident flight was the first one attempted in Wyoming at an elevation of about 4,400 feet.
Probable Cause: The pilot’s adjustment of the carburetor to an incorrect setting, which resulted in partial loss of engine power during takeoff.
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This May 2024 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.
Does that mean that there’s a job in aviation for an old chainsaw mechanic?
Should be. The “modern mechanics” don’t have any greater depth of knowledge than how to read an electronic analyser . Basics are not learned as I have found over my time of teaching engineering
Doesn’t a higher altitude make a richer mixture?
I don’t know how a CV carb [ constant velocity] behaves at altitude ?
This is what happens when those who have only a smattering of knowledge and ignorantly carry out supposed maintenance without double checking OFFICIAL publications. No sympathy warranted here.
I haven’t had a car with a carburetor in fifty years. One would think that by now, carburetor-equipped aircraft would only be in museums.
I realize that some safely operate old airplanes with engines with carburetors all the time, but I am a bit surprised that the manufacturers and insurers have not been incentivized to migrate to fuel injected engines in new designs and as an option for replacing engines at the end of the engines service life.
Don’t show your ignorance: 2 of the most common aircraft engines use carburettors -Lycoming and Continental.
Actually, Mr. Tyler is making a very valid point. I have been read the same observation made on this and other aspects of general aviation for over 30 years now.
The good news is the FAA no longer buys vacuum tubes, I think. But they still have a hankering for morse code and weather reports sent out with 96 baud in mind.
I think you mean 9600 baud, which is pretty slow. There’s nothing wrong with a carburettor – they’ve been used for over 100 years. The problem here was with a guy who didn’t know the difference between knowledge and wisdom.
This was a Rotax 582, 2 stroke engine, which was discontinued in 2021.
It is very sensitive to mixture and high altitude caused a very lean mixture.
Most older GA aircraft still have a carburetor . Newer aircraft use the RSA mechanical fuel injection, similar to the 1963 Corvette Rochester continuous flow system….not electronic.
Replacing an aircraft engine with a different model requires an STC to be developed, which is very expensive.! So, we’re ‘stuck’ with what was certified by the manufacturer.
Seems to me accidents involving fuel induction issues are fuel injection problems, not carbs.
And this case is a neophyte that can’t follow basic instructions.