oil breather blocked on Lycoming

[EK380]

Hi Group,

I recently had an abrupt engine failure at about 200ft in a single engine, O-235 powered homebuilt aircraft... managed to land it on the concrete with no serious damage.

For the last week, I've been looking fo the cause of the engine failure, have given the Carburator an overhaul. Fuel was selected on a tank containing 40L, and all engine controls are free.
First thoughts was some kind of dirt in the fuel, but nothing was found.Tanks were drained beforehand.


Just today, I might have been closer to finding a reason for the failure.... my "oil breather" line was totally blocked (99% blocked.... due to a wrong setup of a small container to collect the oil, which made it's first flight when the failure happened).

Can any mechanic comment on the above.... ever heard of an engine dying from a blocked oil breather line? The lower spark plugs were full of oil after the incident... Upper ones were dry. My sparkplugs are NOT crosswired, one magneto for the upper the other for the lower ones.

The way the engine stopped, was a sudden stop, with no serious vibrations before that. Just like engine stoppage after fuel starvation.

I was able to start the engine again about 1hr after the mishap. Engine is now running normal.


All comment more than welcome, especially if someone can explain me why an engine can stop with the breather blocked... I would rather expect heavy oil leakage etc... Would a sudden engine stoppage be possible?

Of course I would like to find the reason of the failure, before bringing her back in the air....


Regards

[A and C]

It sounds like carb ice to me , what was the temp and dew point on the day in question ?.

A blocked oil breather is unlikely to result in this type of stoppage , if the breather is blocked it usualy results in high oil consumption. You do have a breather problem but I dont think that this stopped the engine.

I think that a fuel flow rate check is required with the aircraft in the climb attitude and a check of the fuel tank vents.

[EK380]

Hi A and C,


Thanks for your advice.... Carbu ice can be more or less excluded since the engine failure was abrupt, not gradual power loss as with carbu ice. As well it was very dry and +20C.

I agree that the oil breather scenario, seems hard to believe,... that's why I ask it here.

The fuel flow has been checked, as well as the Carburator.


Hope to receive some more feedback from others as well....,


Thanks

[A and C]

Some of the worst carb ice I have had has been on hot days this is because the volume of water in the air is much higher on a hot day.

Check the temp / dew point spilt and if it was less than 5C then suspect carb ice.
I have long been of the opinion that carb ice is also a function of the air intake shape as the C152 will ice more than the PA38 both have the Lycoming O-235 but the C152 will ice more quickly than the PA38.
Last year one of my C152's had the engine stop in much the same way as you discribe above , we checked the engine over and could find nothining wrong I am sure that it was ice but can't prove it however I will try to find the WX reports from the day in question and see if this matches your inccident.