SonexBuilders.net

Looked at GPC and Sonex recommended breakin procedures and they are quite different. I am prone to go with the min ground run before flight that Sonex recommends but I also like the thought of a little more time before the first flight. Any thoughts on this from AeroVee drivers?

I'm curious - what does Great Plains recommend for their engines?

Please do not misconstrue "minimal ground running" with little to no ground running. The FAA requires 1 hour of ground running before they will allow your Air Worthiness Certificate to be issued. That one hour will easily be consumed if you PRECISELY follow all of the steps in the Aerovee manual AND the AeroInjector manual. You will have to go through the steps to set up and adjust the mixture and the idle speed on your AeroInjector. This includes making sure your EGTs are in the proper range at full throttle and have the appropriate rise in temperature at lean peak. This will take multiple attempts. You will need to ensure you NEVER exceed the maximum temperature for your CHTs, this means short high power ground runs with the cowling on and letting the engine cool between runs. You will have to go through the steps to set your timing, This will also take multiple attempts. Make sure you follow every step in the two manuals and clearly understand each step and what that step is trying to accomplish. Do not skip any step or instruction. If you pay attention to the details in the two manuals and have verified proper operation you will then have an engine that is ready for first flight.

Avoiding "excessive" ground running means that you should not just run the engine for the sake of running it. Each ground run should have a specific purpose and be carried out without overheating the CHTs. Your CHTs will rise very quickly to redline on a new engine at full throttle on the ground and it makes checking the proper EGT temperature range a challenge. So, you need a specific plan for each ground run. In addition, excessive ground running can prevent the piston rings from properly breaking in.

On my first flight, I did not have my mixture adjusted properly. I did not fully understand the range of EGT temperature required at full throttle. As a result my EGT and CHT were both at redline right after takeoff so I had to land immediately. My timing was also off so I had to adjust that after the second flight. On a later flight I incorrectly richened my mixture needle excessively and had to abort my takeoff when the engine bogged down and lost power 50 feet in the air. It scared the hell out of me. Fortunately I was on a 6,000 foot runway and was able to land straight ahead. The lesson: read and re read and fully understand what the manuals are telling you.

YOUR SAFETY FIRST

If you precisely follow the manuals and verify everything is working correctly you will have an enjoyable and memorable first flight.

Thanks,

Jake

Make it a little rich when tuning on the ground. Many (myself included) found out we were too lean on the first flight and had quick climbing egt and Chts. Way better to have to pull the mixture out a bit because you are too rich than to be too lean and have no other options but to quickly get it back on the ground before frying your heads.

Keith
#554

Had my aerovee rebuilt by Great Plains. this is what they told me. Run engine at 2500 rpms for 5 minutes and shut down. Repeat 6 times with letting engine completely cool down between runs. John

Great post Jake!

SonexN76ET wrote:The FAA requires 1 hour of ground running before they will allow your Air Worthiness Certificate to be issued.

Someone PMed me stating that the 1 hour of ground running statement might be incorrect. I don't know the regs and I don't have time to search and verify at the moment so if anyone can point to that regulation it would help out. Thanks

Check this out:

This is the EAA's DAR checklist referencing the requirement for an hour of engine run time.

https://www.eaa.org/en/eaa/aviation-communities-and-interests/homebuilt-aircraft-and-homebuilt-aircraft-kits/resources-for-while-youre-building/registering-articles/amateur-built-aircraft-certification-inspection-guide

Paragraph D

I am not going to argue with any outhouse lawyers on the nuances of this. Take it up with the EAA or your DAR. I am only quoting EAA.

Jake

The "one hour" requirement was never regulatory. It was a policy that existed for some time. However, a review of the current certification documents - FAA Order 8130.2H and AC 20-27G - shows no such statement of policy. Some inspectors and DARs who have been around a long time may still feel that it is a "requirement". Talk to your DAR or inspector before hand to make sure that you are all on the same page.