According to the pilot receiving instruction they departed the airport in Lodi, California, uneventfully and climbed to their cruise altitude, 3,000 feet mean sea level. The pilot receiving instruction donned an instrument instruction tool at 200 feet above ground level.
Once they reached cruise altitude, he reduced power to 2,450 rpm, applied carburetor heat, and leaned the fuel/air mixture to achieve best rpm. He followed the airplane’s cruise checklist, scanned the engine instruments and did not observe any anomalies as each instrument was reporting normal operation.
Approximately five minutes later, he heard a sound that resembled a gun shot, and the propeller stop rotating. The instructor took control of the Cessna 150J and announced “my controls” while the pilot searched for a suitable place to land and attempted to restart the engine. He was unsuccessful.
Although they were surrounded by fields, their options for suitable landing sites were limited due to trees or other obstacles. They were able to glide the airplane to the end of an almond tree field where the airplane hit trees before coming to rest in the field.
Photographs of the airplane taken by local law enforcement showed substantial damage to the wings and empennage.
A post-accident examination of the engine revealed that the top of the engine case was fractured with a hole that extended about seven inches in diameter. Additionally, the lower case had fractured around the circumference of the No. 4 cylinder. Continuity of the throttle and mixture controls was confirmed from the cockpit to their respective arms at the carburetor.
The No. 3 cylinder connecting rod was fractured at the connecting rod shank and was mechanically damaged. The No. 4 cylinder barrel rim was bent outboard towards the crankcase. A borescope inspection of No. 3 cylinder revealed that the connecting rod bushing end was still attached to the piston pin, but the piston ring seal was fractured, and part of a piston ring was exposed. No evidence of oil starvation or thermal damage was observed.
Metallurgical analysis of the No. 3 cylinder connecting rod revealed that the fractured face exhibited crack arrest marks consistent with fatigue cracking. The fatigue crack emanated from the outer surface at one corner of the arm. A portion of the fatigue crack also displayed mechanical damage that destroyed some of the fatigue crack features. However, the origin of the fatigue crack did not exhibit any indications of mechanical damage such as a gouge. The No. 3 cylinder piston contained evidence of heavy combustion deposits at the outer crown. Similar deposits were also observed near the spark plug ports and the intake and exhaust valves.
Post-accident examination of the airplane revealed that the carburetor input fuel line contained a smell that resembled automotive gasoline. The owner stated that he had only used 100 low lead aviation grade gasoline (100LL) in the 60 total flight hours he had accumulated in the airplane since he purchased it. Fuel receipts showed that the pilot purchased 12.3 gallons of 100LL the day before the accident and 17 gallons of 100LL on the day of the accident. According to the owner, the previous owner had implied that he only ever used 100LL during their correspondence. The fuel from the accident site was not tested.
The pilot stated that he regularly used carburetor heat due to a “serious issue with carb ice” as he had that day when he reached cruise altitude. He would have adjusted the carburetor heat until the carburetor heat temperature gauge reached a certain temperature and then leaned the mixture out to achieve best rpm before enrichening the mixture about three full turns.
The previous owner who flew the airplane from the engine’s most recent overhaul had passed away and was not available for a statement.
According to the FAA Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25B), detonation is defined as “an uncontrolled, explosive ignition of the fuel-air mixture within the cylinder’s combustion chamber. It causes excessive temperatures and pressures which, if not corrected, can quickly lead to failure of the piston, cylinder, or valves.”
The section also provides several causes of detonation, including the use of a lower grade fuel than specified by the manufacturer and operating the engine at high power settings with an excessively lean mixture.
According to the PHAK, preignition occurs when “the fuel-air mixture ignites prior to the engine’s normal ignition event. Premature burning is usually caused by a residual hot spot in the combustion chamber, often created by a small carbon deposit on a spark plug, a cracked spark plug insulator, or other damage in the cylinder that causes a part of heat sufficiently to ignite the fuel-air charge. Preignition causes the engine to lose power and produces high operating temperatures. As with detonation, preignition may also cause severe engine damage because the expanding gases exert excessive pressure on the piston while still on its compression stroke.”
It should also be noted that detonation and preignition can occur simultaneously and/or one may be caused by the other.
Probable Cause: A total loss of engine power during cruise flight due to a fatigue crack in the No. 3 cylinder connecting rod shaft resulting from either preignition or detonation, which resulted in a forced landing and impact with terrain.
To download the final report. Click here. This will trigger a PDF download to your device.
This March 2021 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.
Lean mixture does not cause pre ignition it causes high egt’s.
Partial carb heat does not cause carb ice near the Venturi. Carb heat introduces hot hot air into the carb intake.
There’s no individual carb on the #3 cylinder needle and seat could have stuck????
My recommendation is for all aircraft engines to have a jpi 730 engine monitor or better, never run lean of peak to save a penny, never run lean on a run-up to clean a fouled plug, never shock cool your engine, aka performing simulated
engine outs, run your engine at least once a week and run 100LL.
Professional engine builder.
Pilot error whent over red line in a spin. And did not pull power back
The carburetor on number 3 cylinder needle and seat could have malfunction. That would let the cylinder fill with fuel.
That can cause a hydraulic effect in the cylinder breaking rod.
The other possible scenario the destination
could have damaged through heat and blow head gasket then coolant hydraulic
cylinder in automotive applications.
One other thing just impurities in connecting rod when made. Molecular
The Continental engines use a single barrel, updraft carburetor, with manifold pipes to each cylinder.
What is “destination”? Was your comment proofread from the ‘Fortune Cookie Spell Check’ App?
Nevertheless, I would be hesitant to take advice from any mechanic with spelling, grammar and composition issues.
Not to mention, only one of the scenarios you referenced, the possiblity of a manufacturing defect in the connecting rod, could be plausible…..maybe.
The rest is just word salad from a (mis) fortune cookie.
Did the buyer have an FAA certified aircraft mechanic do a complete recertification inspection and a paperwork and flight log review + a tail number history review before purchasing the aircraft? I would before I would risk my life on it. I was an FAA. DER for an Aircraft instrument manufacturer.
Buyer be ware or be dead.
None of all that would have detected any defect inside the engine.
Lycon built the engine, and is one of the most highly regarded aircraft engine builders.
No one addressed the unorthodox use of carb heat. The pilot describes pulling the carb heat control on then leaning the mixture.
Application of carb heat will cause a slight loss of power due to hot (less dense air) entering the combustion chamber. Leaning the now rich mixture will only achieve a mixture constant with flying at a higher altitude with no gain of power. If the pilot would push the carb heat control off, the mixture would now be quite lean and could cause a pre ingnition / detination potential. I’m a bit surprised the flight instructor didn’t catch this.
Partial use of carb heat is an accepted practice, only if the aircraft has a carb temp gauge, which measures the temp at the venturi.
My 1961 Cessna 175B has a carb temp gauge and I have used it to keep the venturi temp out of the ‘yellow’ zone. And then, I do have to lean the mixture and live with a bit less power and airspeed.
I must respectfully disagree with the use of “partial ” use of carb heat. It should only be engaged when carb ice is suspected or when power is about to be reduced. Some engine such as the Continentals are more susceptible to developing carbice due to the position of the carburator where as the Lycoming the carburator is in direct contact to the oil sump which is warm. Partial use of carb heat may cause ice to form just beyond the venturi.
The moisture is still present whether the carb heat is applied or not. It should be fully on or off.
Here’s a section from a C182 POH, that describes using partial carb heat….
” CESSNA MODEL 182Q
SECTION 4
NORMAL PROCEDURES
3. If the airplane is equipped with a carburetor air temperature gauge.
it can be used as a reference in maintaining carburetor air
temperature at or slightly above the top of the yellow arc by
application of carburetor heat. “
Exactly, one must understand that all aircraft are not the same or equipped the same. Too long ago now but, the Twin Beeches that I maintained routinely used partial manifold heat. That was the point of the carb. temp. gauge. Keep the carb at the right temp when the dewpoint was up and those Pratt&Whitneys would rumble all night long.
A connecting rod on my Toyota Tacoma failed at 76,000 miles. I never used carb heat or leaned the mixture on my truck : )
When I first went to a dealer they were very polite and told me connecting rods never fail on Toyotas. They told me that awful, loud bang must have been “ something else “.
I paid the dealership to put in a used replacement engine of unknown mileage. Now at 167,000 miles, and all is still going well.
Buying a used car or airplane is akin to marrying somebody else’s ex-wife: You never really know what it’s prior history is. Sounds like some prior owner/operator ran the engine hard and lean on car gasoline and sowed the seeds of its destruction years ago, then sold it to an unsuspecting sucker and laughed all the way to the bank. Caveat emptor: Let the buyer beware. Ever so true.
Regards/J
The engine was rebuilt by Lycon, a highly rated race engine builder 279 hrs before the rod broke.
[ no ex-wife situation ]
Standard O-200 engines do not detonate. Engines that detonate do not leave deposits in the combustion chamber. Engines that detonate destroy aluminum alloy pistons before they break connecting rods.
I can’t see how operating the engine in ANY manner can cause a connecting rod to break in half.!! This had to be a manufacturing defect or it was damaged during assembly, and took 279 hours to fail.
There are several ways that imprper operation can cause catastrophic engine failure. The use of fuel with a lower octane rating than required, improper leaning of the fuel to air mixture can absolutely lead to this type of failure.
I have more than fifty years flying experience, and an aircraft mechanic, I am 3rd of four generations in the aviation business. I have flown nearly 100 different types of airplanes with more than 5000 hours flying experience.
It could very easily be inferred from the article that the use of a “non-aviation fuel” such as gasoline, is an obvious potential reason for the catastrophic destruction of the engine. Unfortunately, the article is substantially devoid of investigative details and is grossly incorrect on a number of technical items.
In the first place, while detonation does in fact cause a substantial increase in combustion chamber pressure above what would be experienced during a peak EGT/stoichiometric, lean of peak, or excessively rich mixture, it does NOT result in high cylinder head temperatures (CHTs). Rather, though perhaps counterintuitive, it results in depressed CHTs and higher EGTs as a higher quantiity of the heat energy due to the unstable flame front of the burn ends up existing the exhaust port during the exhaust stroke.
Second, detonation does not cause depositing. If anything, it reduces and cleans depositing. The unstable flame front and its associated pressures and chaotic burn pattern, loosen and burn off combustion chamber deposits and often, thought the amount of generally quite small, remove the tiniest amount of metal from the area. A borescope of a cylinder that has undergone even prolonged mild detonation, will appear clean and lightly sandblasted. It does not, “quickly lead to failure of the piston, cylinder, or valves”. If the detonation was extreme, it may cause significant pitting of the piston crown and top of the cylinder, but it will not drive a hole through the crown in short order as would preignition, which itself is an entirely different event and again in the article, is treated as if they are directly related. The cause of one is not often the cause of the other.
Third, devoid of oxygenation additives such as Ethanol, automotive gasoline is almost always *far* healthier for an aviation engine than is 100LL for any compatible Lycoming or Continental engine. This would include just about any engine operating at a compression ratio at or below 8.5:1, with the necessary octane rating to avoid detonation, decreasing, as compression ratio decreases. At the compression ratios a Continental O-200-A engine operates at, which is presumably what the failed engine was given that the aircraft model is a Cessna 150J, non-ethanol 87 octane gasoline would’ve burned all day long without detonation, resulted in a cleaner combustion chamber, cleaner oil, no lead sludge or depositing, and certainly would’ve never caused a connecting rod failure.
Fourth, while there are mixture regimes that are physically more stressful on Lycoming and Continental engines than others, primarily those at or above 60-65% power, and between 40-60 degrees rich of peak EGT, there is no mixture or power condition that would ever result in a failed con rod, piston, or for that matter, ANY item in or directly connected to the combustion chamber. Aside from running into an object or grossly overspeeding the engine, it is all but impossible to cause “catastrophic” engine damage by manipulation of either the black (throttle) or red (mixture) controls.
“improper leaning of the fuel to air mixture can absolutely lead to this type of failure.”
This is not true. If you have technical details to support this, please raise them.
Fifth, I would remind folks that just because the POH says something, does not make it true in perpetuity. Remember, many POH’s say not to lean below 3000 feet. They tell you operating in an oversquare RPM/MP condition will result in excessive engine wear, possibly catastrophic. They will tell you that absolute EGT values should remain between 1300-1500 (degrees F). I could go on. All of the above, are demonstrably incorrect (read: flat out lies).
A POH recommending the use of partial carb heat, is in desperate need of review. As is any implication that the use of automotive gasoline would cause a con rod failure in a Continental O-200, or that it could be caused by anything the pilot or their instructor did with the engine controls available to them. No way, no how.