Indications of a cracked cylinder, to pilot

LongRoadBob

LongRoadBob

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Have found out the airplane I will be flying now is a Cessna 172SP with Lycoming engine.
That the history of this particular aircraft was pretty stable up until sometime early 2017 when there have been two (or more) incidents of cracked cylinders.

First time was early 2017, two cylinders had developed cracks. They caught it, did a compression check and had the engine repaired.

Then (definitely once more but I think maybe two more times, It wasn't clear to me) again towards the end of 2017 was another (believe it was different) cylinder found to have cracks.

Then also in beginning of 2018, yet again.

This was brought up in a club meeting. The clubs' leaders have tried to find out what the reason for this sudden rash of this problem. They believe that there has been no difference in flying, use of the plane. They are less sure if something changed at where the repairs are being carried out.

One thing struck me, he mentioned I think the last time that the pilot never heard anything, but folk on the ground at the airport reported the engine sounding "strange". I wish I had thought to ask him "strange how?".

Anyone here experience cracked cylinder and any particular noise that may be apparent when this happens?
Also, I would expect "partial loss of power", but would that show up only on full throttle? Otherwise would someone just notice it in climb rate, or even know that with the throttle "just so" you expect around X rpm?

What signs, how do they manifest with cracked cylinders?
 
So was it total of 4 cracked cylinders? Were those the previous ones or did a new one "re-crack"?
Has someone in the club recently started doing power-off 180s right after a slow hot climbout into the pattern? :)

And I would expect you'd see a change in numbers on the engine monitor. Since I am no engine expert, I won't post a guess here, I'd rather wait for an engine expert to provide facts.
 
It would take a BIG crack to produce any change in sound. And it would result in noticeable power loss.

These engines are tough, yet there have been plenty of airworthiness directives against aftermarket cylinders, including cylinders for this engine, that are prone to cracking. Perhaps a thorough AD review is in order for that airplane.
 
When a cylinder cracks, it will produce a whistle or a hissing sound, when it gets bad enough it will start to skip and then a vibration starts. After it gets bad enough it will shake the whole aircraft then pilots can't help but feel it.
 
Wouldn't the EGTs differ from the planes normal baseline trend?
 
Many cracks are located only by exhaust stains where they shouldn't be. Or by putting the cylinder under pressure and soaping the head and upper barrel. More gases get past the rings than through some cracks.
 
@LongRoadBob also just be cautious about believing that nobody's abusing it... not saying the folks are wrong, but sometimes renters are just pricks and do things to rentals that they just plain shouldn't when nobody is looking.

But as others have said, there's a lot of cylinders out there that are problematic from bad manufacturing and changes in the industry that happened a while ago, and then kinda got fixed... kinda... so there's that, too...

Impossible for any of the actual experts here (Charlie from Zephyr stops by once in a while) to give any real advice on it without seeing the logs and where they came from.
 
BigBadLou said:
So was it total of 4 cracked cylinders? Were those the previous ones or did a new one "re-crack"?
Has someone in the club recently started doing power-off 180s right after a slow hot climbout into the pattern? :)

And I would expect you'd see a change in numbers on the engine monitor. Since I am no engine expert, I won't post a guess here, I'd rather wait for an engine expert to provide facts.
Click to expand...

I didn't get the details, they weren't presented completely. Thanks all for the information.
 
every preflight look for the white magic dust with a good light and mirror .once you find it once you will know what you are looking for!
 
455 Bravo Uniform said:
Can you elaborate?
Click to expand...

b02dfc7210650389c6559c3d433e599a.jpg




Sent from my iPhone using Tapatalk
 
Is it a G1000 equipped aircraft? If it is, pull the data log card from the top spot of the MFD.
If it has an engine monitor, it might log as well.
I bet the data would show some hints as to what is really going on.
 
What am I looking for in that picture?
 
Most of the cracked cylinder are found during overhaul of the cylinder. When the carbon deposits are cleaned away the crack is exposed.
 
Cracks on a FI cylinder will produce the blue fuel stains. Cracks in other areas will produce a dirty oil deposit or exhaust (yellow/red) deposits.

If cracks are suspected one could spray the cylinder down with soapy water and look for bubbles while the cylinder is pressurized during a differential pressure check.
 
Thanks I thought I was looking for something white.
 
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