One o'them annuals...

Chip Sylverne

Chip Sylverne

Final Approach
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Quit with the negative waves, man.
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Cherokee with Lyc 0-320. 525 SMOH and Penn Yan 160 conversion. Three of four jugs have cracks in the exhaust flanges, and the 1-2 exh.stack is cracked. Replaced the remaining jug earlier in the year. Don't know if one of the pards is leaning too aggressively , or maybe stress cracks from vibration.
Maybe it's time for a CHT monitor and a dynamic prop balance. This cyl replacement crap is getting spendy...
 
smigaldi said:
Just out of curiosity what brand were the cylinders?

The old classic cast ECIs that I had were recalled for this issue.
Click to expand...

There's a new AD on the ECI Titans, but it's for cracking at the head-to-barrel interface, not the exhaust flanges.
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/list/2009-26-12?OpenDocument

Lycoming says you can do anything you like with the mixture on a normally aspirated engine as long as it's at 75% power or lower. I don't think leaning would do it. I would think shock cooling is more likely (some don't think there's such a thing, but the older Lyc cylinders would crack from the exhaust port to the lower sparkplug hole if cooled too quickly, and Lycoming still warns against it), or perhaps the exhaust riser attachment hardware was overtorqued. Vibration maybe could do it. Really late mag timing will put a lot more flame into the stacks, too, and get things far too hot.

Make sure the baffling around the exhaust ports is as it should be. If it's eaten away it won't properly duct air against the metal.

Dan
 
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Dan Thomas said:
There's a new AD on the ECI Titans, but it's for cracking at the head-to-barrel interface, not the exhaust flanges.
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/list/2009-26-12?OpenDocument
Click to expand...
Yeah I know about that one. I was bruned twice by ECI cylinder ADs. After two top overhauls in 3 years I changed brands. It has been less than a year with the Lycomings.

Dan Thomas said:
Lycoming says you can do anything you like with the mixture on a normally aspirated engine as long as it's at 75% power or lower. I don't think leaning would do it. I would think shock cooling is more likely (some don't think there's such a thing, but the older Lyc cylinders would crack from the exhaust port to the lower sparkplug hole if cooled too quickly, and Lycoming still warns against it), or perhaps the exhaust riser attachment hardware was overtorqued. Vibration maybe could do it. Really late mag timing will put a lot more flame into the stacks, too, and get things far too hot.

Dan
Click to expand...
Interesting.
 
Chip Sylverne said:
Cherokee with Lyc 0-320. 525 SMOH and Penn Yan 160 conversion. Three of four jugs have cracks in the exhaust flanges, and the 1-2 exh.stack is cracked. Replaced the remaining jug earlier in the year. Don't know if one of the pards is leaning too aggressively , or maybe stress cracks from vibration.
Maybe it's time for a CHT monitor and a dynamic prop balance. This cyl replacement crap is getting spendy...
Click to expand...

We had this exact same problem (cracks starting at the exhaust ports) on some Superior cylinders on an O-360-A4M (Archer). Replaced all four cylinders at 1620 SMOH. Theory the A&P's had was vibration - They replaced a cracked starter too.
 
flyingcheesehead said:
We had this exact same problem (cracks starting at the exhaust ports) on some Superior cylinders on an O-360-A4M (Archer). Replaced all four cylinders at 1620 SMOH. Theory the A&P's had was vibration - They replaced a cracked starter too.
Click to expand...

How did you handle the vibration issue?
 
A few years ago, I had the prop on my PA28-180 sent out for overhaul and then the next annual had the Lord mounts replaced.

The engine was never too bad before, but it certainly is smoother now.


Chip Sylverne said:
How did you handle the vibration issue?
Click to expand...
 
Chip Sylverne said:
How did you handle the vibration issue?
Click to expand...

Haven't. Need to get a specialist to see if it's the prop or the crank out of balance. I don't think it's the prop. :frown2: But, the cylinders were replaced and the engine will probably go past TBO anyway...
 
Chip Sylverne said:
How did you handle the vibration issue?
Click to expand...

I'll offer an answer even though I'm not Kent.

The vibration on the Dakota at any setting other than range of max to ~ 2400 was so bad that the needles would be jumping on the instrument panel. I thought it'd destroy the instruments in short order.

The prop was slinging oil and it had been 1,200 since overhaul (its a 600 hour prop). Off to the prop shop for overhaul. Had the prop dynamically balanced after installation. Result was smoooooth operation through the entire operating range.

Prop shops and shops that work on helos should be able to dynamically balance the prop. I suspect it's hit-n-miss on other shops having the equipment since it's $$$$$ for a Chadwick (SP?).

Should be ~6 hours or less shop time for the work. The quotes I got included a flat rate from the prop shop and an hourly rate with a minimum of 3 hours just to setup for the balance from an A&P.

In the end it's money well spent in my book. As always YMWV.
 
Clark1961 said:
I'll offer an answer even though I'm not Kent.

The vibration on the Dakota at any setting other than range of max to ~ 2400 was so bad that the needles would be jumping on the instrument panel. I thought it'd destroy the instruments in short order.

The prop was slinging oil and it had been 1,200 since overhaul (its a 600 hour prop). Off to the prop shop for overhaul. Had the prop dynamically balanced after installation. Result was smoooooth operation through the entire operating range.

Prop shops and shops that work on helos should be able to dynamically balance the prop. I suspect it's hit-n-miss on other shops having the equipment since it's $$$$$ for a Chadwick (SP?).

Should be ~6 hours or less shop time for the work. The quotes I got included a flat rate from the prop shop and an hourly rate with a minimum of 3 hours just to setup for the balance from an A&P.

In the end it's money well spent in my book. As always YMWV.
Click to expand...

Thanks. I've read good things about dynamic balance, but it's always good to hear about personal experience. Our shop has the equipment and experience to do the job, but they want to wait for 25 hours and the first oil change to do it so the new cyls will be broken in. Probably cyl overheating concerns from the required static runups to get the balance right. Seems a little over cautious to me, as I would rather have the balance right from the start. I mean, how many runups is it going to take to get a fixed pitch prop balanced? But that's their policy. We'll just have to do a lot of flying for the first couple of weeks.:D
 
FWIW, when doing a Dynamic Balance on a propeller you are not actually balancing the prop but the associated hardware, spinner and backplate. I use to do these using an Aces 2020 ProBalancer.

On Lycoming you can place the balance weights on the flywheel/starter ring. On Continental engines you have to drill a hole into the backplate of the spinner and place the weight there.

Make sure the prop and spinner are "indexed" so if removed for maintenance they can be placed back on in the right position.
 
Rotor&Wing said:
FWIW, when doing a Dynamic Balance on a propeller you are not actually balancing the prop but the associated hardware, spinner and backplate. I use to do these using an Aces 2020 ProBalancer.

On Lycoming you can place the balance weights on the flywheel/starter ring. On Continental engines you have to drill a hole into the backplate of the spinner and place the weight there.

Make sure the prop and spinner are "indexed" so if removed for maintenance they can be placed back on in the right position.
Click to expand...
I have a lycoming engine and when I had the prop dynamically balanced they used the spinner backplate to place the weight.
 
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