Excitement today

[Seth]

Larry-

 

Glad you are safe.  It must have felt terrible taxing your sick bird back to the hanger knowing something was really bad.  So glad you didn't get airborne.

 

I had two cylinders crack on my 100 hours after overhaul the same way - on a takeoff roll.  Aborted the takeoff and thank goodness I did.  One cylinder was clearly cracked, and the other had zero compression.  The OH shop however stood behind their work and replaced the cylinders and cut me a deal to replace the others in the lot as I didn't trust them.  So, unfortunately, TOP OH at 100 hours SMOH, but it's been running fine since.  A TOP had been performed 300 hours before I purchased the plane but it was making metal so we conducted an overhaul.  We had the cylinders overhauled as opposed to new - my mistake - I didn't know that they cylinders put on during the previous TOP were overhauled.  I thought I had been told they were new and it was my fault for not verifying.  You learn as you make mistakes I guess.

 

So new cylinders the last few years and a strong running engine with extreme minimal oil burn.

 

Good luck with your repair and hope she's flying again soon.  If you have a hanger, talk with your MSC about having the repairs done in your hanger (if you are close) as opposed to a shop your don't trust with the work.

 

-Seth

[larryb]

I really don't know the history of the 3 other cylinders. The plane is an 84. In 97 it had a gear up and major overhaul. Nothing in the logs about what happened to the cylinders at overhaul. In 2004, at 323 SMOH all 4 cylinders had work. Log entry: "Reinstalled 3 cylinders after repair, and installed 1 used overhauled cylinder." I have the yellow tags from that work, 3 cylinders have sequential SN's. There is 1 SN not in sequence. The failed cylinder is one of the 3 sequential SN's. Next, in 2008 at 588 SMOH cylinder #3 was removed and repaired again. This is the cylinder that failed. In 2012, at 825 SMOH I bought the plane. At the last annual, 1132 SMOH the compressions were 74 72 74 74. It failed 15 hours later.

 

Larry

[FloridaMan]

A friend of mine owns a flight school. He said he had a report that there was a loud BANG on a flight in a 172. They returned to the field, fired it up and things seemed fine. Upon exiting the plane, there was a puddle of oil on the ground; pulling the cowl revealed a separated head. He said the amazing thing was that they could not tell the issue in flight. 

[larryb]

Followup: With the assistance of my msc and a local mechanic on my field, 15 days after the failure the plane is back in the air. The first week was spent ordering and receiving parts. The second week was putting it all back together and getting more parts. The last part was a new pushrod to get the dry tappet clearance in spec. You don't know you need that part until everything else is back together. The list of new parts includes new cylinder assembly, fuel injector line, ignition harness, intake tube, rocker cover, pushrod, and various clamps and hardware. By the time I was done with shipping and tax total parts cost comes to just under $5,000.

 

The first flight was the 3 hour break-in flight per Lycoming manual. CHT was a bit higher than the rest only until shortly after takeoff. Then the CHT fell in-line with the rest. #3 has always been my first to peak, and still is. After the break-in flight #3 runs cooler than the rest. So far so good.

 

Larry

[Marauder]

How high was the pucker factor on the take-off roll?

[aaronk25]

I bet a lot of pucker factor....interesting about your cht drop....I always thought the cylinder walls and rings break-in about 10 mins

[jetdriven]

I really don't know the history of the 3 other cylinders. The plane is an 84. In 97 it had a gear up and major overhaul. Nothing in the logs about what happened to the cylinders at overhaul. In 2004, at 323 SMOH all 4 cylinders had work. Log entry: "Reinstalled 3 cylinders after repair, and installed 1 used overhauled cylinder." I have the yellow tags from that work, 3 cylinders have sequential SN's. There is 1 SN not in sequence. The failed cylinder is one of the 3 sequential SN's. Next, in 2008 at 588 SMOH cylinder #3 was removed and repaired again. This is the cylinder that failed. In 2012, at 825 SMOH I bought the plane. At the last annual, 1132 SMOH the compressions were 74 72 74 74. It failed 15 hours later.

 

Larry

I think the traditional compression leak down test works well for finding valve problems but it may not show a cracked head because the crack may be below the rings. A BDC compression test will find it, however. Can you look at the wear pattern in the old cylinder and see if the ring travel area extends into the head past the crack?

[Shadrach]

Byron is right on. I have seen these a couple of times. One was a 252 with overhauled cylinders en route from San Juan PR to FLL. After I told him how safe the trip was he had a cylinder separation failure in the vicinity of GTK. He landed safely with no damage to the plane but a bill for $50K to replace the engine at GTK. I told him he was better off ditching the plane near the beach and collecting the total loss from the insurance. Insurances do not cover engine malfunction.I always ask for factory new cylinders at engine overhaul. Metal fatigue combined with cylinder honing weakens the cylinder. Is a receipt for cylinder separation.José

How does honing weaken a cylinder? The inside of the sleeve gets honed. How does that affect the barrel? I've honed a few air cooled cylinders, but the only aircraft jug was from an O200. I held the cylinder between my knees (certainly never got hot) and honed it with a hand drill at low speed.

[Mooney6902V]

Looks like good heat distribution on the exhaust valve.