Gary –

 

I also got my IO550N from a Cirrus that had a prop strike. It sounds like your troubleshooting has been pretty thorough. The only other engine items I can think of are your spark plug wires and ignition switch. You might try switching to L mag only or R mag only in flight to see if there’s any change in roughness.

 

Another possibility is that the engine (or one of your control cables) is contacting some part of the cowl and transmitting vibration to the airframe. The engine moves around quite a bit due to air loads, g-forces, and torque. Also, the vibration isolators compress over time causing the engine to sag. Look for scrape or rub marks inside your upper and lower cowlings. I had to trim/bend my engine baffling in a couple of places. After trimming I put blue painter’s tape in the inside of the cowl in the suspect areas. Any contact puts a tear in the tape which is easy to spot.

 

Other possibilities – recheck the torque on your motor mount to firewall bolts and consider getting your prop dynamically balanced.

 

To get help from the experts, go to www.savvyanalysis.com. If you have a digital engine monitor you can upload your flight logs for free and see all your engine data nicely graphed. Their Savvy Analysis Pro service will look at your engine data and provide expert analysis. The cost is $129/year (I haven’t tried it myself).

 

Best of luck,

 

Gentlemen,

I received the following email from Gary Pennington near Tucson, AZ (pennington@q.com): 

 

Hello Bob

Thanks for responding. 

I built a Lancair ES. Airworthiness Certificate issued on Jan. 29, 2012. The engine is a Continental IO 550N out of a Cirrus SR22 that had a prop strike at 350 hours. It was removed from the Cirrus by a shop in Ohio.

They supposedly tore it down, magna fluxed it, installed a new crank kit with bearings, rings, honed the cylinders and did a valve job. I did not visually inspect the work so I am taking their word for it.

Anyway, the engine ran fine for about 100 hours and then developed a slight roughness. I removed the mags and disassembled them. The internal parts looked like they had 5000 hours on them. I installed new parts, reinstalled and timed them to the engine. It ran better but not perfect, so, I removed them again and sent them to Aircraft Magneto Service in Washington State. They did a nice job. Afterwards, it ran great for about 200 hours, then the roughness returned but this time a little different. On takeoff, it developed full power, (2700 rpm), and was smooth, but when squaring at 25 and 2500, the roughness began. Now, it is slightly rough at idle too.

 

I have tested for vacuum leaks. None found. I installed new Tempest plugs. No change. I removed the intake runners and fuel injectors, cleaned and inspected them. No change. I calibrated the fuel injection system three times. No change. I removed the mags and disassembled them and installed new points. No change. I removed the valve covers, rotated the prop and inspected the rockers and springs. All good. I flushed the fuel system. No change. I did another compression test. All good. I'm just bewildered.

 

When I fly on longer trips, I fly between 10000 and 12000, set MAP at 20", RPM at 2200 and lean ROP.

 

If you have any ideas or suggestions, I would love it.

 

Thanks again Bob

Gary Pennington

520-850-7527

If anyone has any ideas on this, would you please post them back to the LML AND directly to Gary, at the email address above?  We’re trying to also recruit him to the LML and LOBO…seems he’s never heard of us.

Thanks,
Bob