Critical Understanding #12 – Yearly Condition Inspection 


I am skipping over #10 and #11, but I will go back and cover them later. Be aware that I may expand this slightly in the next week also. If I do, I will put a revision date in the title.



Above, my original copy of AC43.13 1A /2A from my training at Embry Riddle. In front of it is a logbook from a 1940 Taylorcraft BL-65, NC-24373. Even though a lot of people claim there was no private flying in the US during the war, nor gas for planes, the previous page shows the plane was purchased in southern California  on 3-28-45, and was obviously being flown a lot that week, even though Hitler was still alive and the battle of Iwo Jima was being fought.  You can correct a lot of myths with logs. Note the 3-30 entry saying “Engine running hot as hell”


Homebuilts don’t get traditional Annual inspections, they get a condition inspection. Certified airplanes used for hire also get the same inspection on 100 hr intervals, but since you can’t rent out a homebuilt, it dosent apply.  But the ‘scope and detail’ which is specified in appendix D:


Is a beginning point of all of these inspections, and from it  you should develop a personal inspection checklist.


Some important points:

Just because you own or even built your plane, doesn’t mean you can inspect it. You need a repairman’s certificate for your specific plane to inspect it or you need an A&P mechanic. If a guy the second owner of s a Flybaby,  but he built one before and had a repairman’s certificate  for that Flybaby, it doesn’t count, because the certificate is for a specific plane, not the type. Several years ago I looked at a plane that had 8 years of entries in the logs that said “A+P” looked official, but it turned out the builder and owner had never gotten a repairman’s certificate for the plane, and what he was doing was deceptively writing AtP or Airline Transport Pilot (which he was) in the logs. If anyone thinks they could dance around that detail when you meet the Feds, they are delusional. Have an accident in that plane and the FAA, would charge the pilot with falsifying federal records, his insurance wouldn’t be valid, and he would he personally liable for civil action. Good thing the plane was only used to fly about 50 young eagles. Flying a uninspected plane is something that people try to justify all the time. Just don’t be one of them.


As far as your Corvair goes, these things need to be on your list:


Perform a full visual inspection for leaks and cracked or broken parts paying particular attention to wiring chafing and any exhaust leaks. Wash the engine and dry it. Re-inspect it clean. This process should take at least one hour without interruption. Oil leaks on the engine are not considered acceptable and are to be corrected as detected.


Change the oil and filter, Oil must have more than 800 PPM Zinc Phosphate


Cut the filter open and keep a sample of the element in a plastic bag to compare.


Change the plugs. If your plane has R-44F’s in it, go to Denso W20FP-U’s or better yet Denso IWF20’s While 44F’s have worked for decades, these are an important improvement.


Inspect the inside of the cap, the rotor and the wires. visible  wear is not acceptable.


Charge and Load test the battery. replace it if it fails or retire it if it is more than 5 years old. NEVER put a trickle charger on an AGM battery like an Odyssey.


Perform a DIFFERENTIAL compression test. Note the compressions for each cylinder, and where the leaks are. Instead of 60/80 being minimum, make 68/80 minimum. anything less than 72/80 requires another inspection in 5 hours.


Carefully check the full function of all engine controls.


Carefully check the integrity  of all engine instrumentation sensors and systems.


Clean or replace air filter, and note this in logs. Bracket brand air filter elements must be replaced at inspection, no matter how many hours they were used.


Replace all fuel filters, drain and clean all sumps, including the carb float bowl.


Carefully inspect balancer for any type of degradation of the elastomer. None is acceptable.


Set the timing on BOTH, A and B ignitions, at full static rpm. Note the timing and rpm in the logs for each ignition. Make sure the RPM drop on the back up ignition is within limits.


Verify , with a voltmeter, that the charging system is functioning to capacity. Note in the logs RPM required for the charging system to register 13.0 volts


Re-torque the propeller to manufacturers specs. and enter this number in the logs, along with the next required interval for torque.


Perform a “Two Minute Test” Write the OAT, DA, CHT, RPM and oil temp and pressure in the logs


Date and sign the logs with the statement “I , xxxx xxxxx swear that I have inspected this engine, entered the data in the logs and declare this engine to be airworthy” put down your repairman’s certificate number or your A&P license number.


NOTE: If the plane’s insurance specifies the engine is being operated  “In accordance with William Wynne guidelines” as some insurance does, this means the insurance will not be valid if the compression numbers in in the logs say “130 -125-….” indicating an automotive tester was used or if they find the motor to have NGK or Bosh plugs. Your plane, your choice, do as you wish, just answer for yourself what is to be gained by doing it differently, and what the potential cost is.



About William Wynne
I have been continuously building, testing and flying Corvair engines since 1989. Information, parts and components that we developed and tested are now flying on several hundred Corvair powered aircraft. I earned a Bachelor of Science in Professional Aeronautics and an A&P license from Embry-Riddle Aeronautical University, and have a proven 20 year track record of effectively teaching homebuilders how to create and fly their own Corvair powered planes. Much of this is chronicled at and in more than 50 magazine articles.

11 Responses to Critical Understanding #12 – Yearly Condition Inspection 

  1. Brent Mayo says:

    William is the engine compression test checked cold or hot? Thanks

  2. Ray Klein says:

    William, I am interested in the why of no trickle charge on AGM batteries. You seem firm on this.

  3. Hi William,

    I have used both Autollite 275 (briefly) and AC R44F. I have had excellent service with the AC plugs but I trust your recommendation to upgrade to Denso. I noted some time ago that your recommended part number was IWF16-5359 and here you give IWF20-5359. Noted earlier in the article “Critical Understanding #4” you also list IWF22-5359 as a suitable plug.

    Of course this is the heat range number. Most charts give the IWF16-5359 as a direct cross for the R44F plugs I’m currently using. Perhaps you have a particular recommendation for a a 3.0 in a Cleanex runnning mostly 100LL with occasional splashes of Ethanol Free 93 Octane.

    Any help greatly appreciated!

    Dale Williams
    N319WF @ 6J2
    Myunn – “daughter of Cleanex”
    120 HP – 3.0 Corvair
    Tail Wheel – Center Stick
    Signature Finish 2200 Paint Job
    138.2 hours / Status – Flying

    • The 16’s are nearly the same as 44’s, but testing has shown virtually every Corvair can tolerate running one step cooler. On a perfect installation it is not needed, but it provides an additional margin against detonation with no down side. If your 3.0 engine has 110 heads, you can even look at 22’s. The Densos have platted threads that are far less likely to strip a head thread or seize onto an insert.

  4. Gordon Turner says:

    Hi William.

    You say time BOTH A and B ignitions. There is something I don’t understand then. Since they are both in the same distributor, aren’t their timings locked together? I will try to find the specific directions for setting the timing.

    Cheers, Gordon

  5. John Steere says:

    William, Thanks for these Critical Understanding posts. They are very helpful.
    Will you be writing one about the initial test run and engine break-in procedures for those of us who can’t do it at a college? I expect to run my engine for the first time (on my Panther) within two months. I want to be sure I do it the best way, and learn as much as possible during the process.
    John Steere

  6. dewayne clardy says:

    While installing my jug I broke the end of one of fins on the top side of the lower jug it doesnt appear to be in the cylinder wall. IS there limitations on cylinder fin damge, or should this be replaced or is it possible to take to a welder have him braze( or tig weld it back )

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: