Yearly Condition Inspection on Corvair Engine


Get a look at the logbook entry below; This isn’t a joke, it is for real, it was ‘signed’ by an alleged aircraft mechanic six weeks ago in the Chicago area. It was done as a condition of sale for a Corvair powered aircraft which was sold as “Airworthy” and “Inspected” for a new owner who trusted the seller and his mechanic. It is complete bull shit, this doesnt constitute an airworthiness inspection nor a valid log book entry. This is no small matter, log book entries are subject to federal laws.


I earned my A&P license at Embry-Riddle Aeronautical University a generation ago. Our classes on documentation were taught by Professor Robert Routh, a retired NTSB administrative law judge. I am well versed in valid inspections and their documentation. Many homebuilders mistakenly believe that the FAA is somehow lenient on enforcement with homebuilts. I will grant they can appear arbitrary, but when they get focused on a case, they run it just as if it were an airliner. My FAA office is Orlando, and in our area, such an entry if discovered would be grounds for revocation of the mechanics license. That may not even be possible here, because I suspect the name and number are made up.


As a homebuilder working on your own plane, you don’t have to be concerned about what the jackasses are doing. You are going to finish your own plane, get the repairman certificate for it, and then you are going to do all your own inspections. You will be independent of what others. The Corvair, sets you apart from other homebuilders, because for 28 years I have been teaching builders how to be skilled builder-operators, not just the person who bought something. Your willingness to learn, and our demonstrated commitment to builder education is the perfect alloy to free you from putting your life in the hands of clowns.


Condition Inspection


Yes, this is a real log book. Who cleans a $1.50 spark plug?  Why was the timing not set? Where is the oil change? Where is the test run? This is what you get when an uninformed person wants to make a quick buck and a seller wants to imply something is airworthy. Your life is too important to trust it to such people.


What is this inspection?


Experimental aircraft don’t get Annual inspections like Certified planes. Instead they get a Condition inspection, which, if an intelligent person with respect for human life is conducting it, is done to at leastthe same standard as an annual on a certified plane.  If you took a Cessna 150 and the average homebuilt and just kept flying them with no further inspections, the homebuilt would break first. No homebuilt has the production numbers nor the refining of a 150, far less having been certified, built by professionals and maintained by them. For this reason, homebuilts need better and more frequent inspections than certified aircraft, but of course they rarely get them. Set yourself apart from the lazy herd, be determined to never have anything in your plane break that you could have found with an inspection. An issue caught on an inspection is an in flight emergency or a tragic disaster prevented. 


Who can do this inspection?

This inspection is required by the FAA for the plane to be airworthy.  To do the inspection the person conducting it must have been the builder of recordandhold a repairman certificate for that specific plane.  Alternatively, an A&P mechanic can also conduct the inspection.


Below, I’m going to list all the steps that I consider a minimum to conduct an effective and valid Condition inspection on a Corvair Engine. These are gathered from my writing. There is nothing new here. As evidence read this:  Critical Understanding #12 – Yearly Condition Inspection 


Now, two Comments:

A)   No one can conduct an inspection without documented standards they are checking the plane against, period. For example, an A&P can’t verify the timing on a Corvair if he doesn’t know what it is supposed to be. So no one would do that right? Guess again, I have seen more than 200 logbook entries for Condition inspections done by A&P mechanics that make no reference to ever checking the timing. These were all done for second owners of planes, people who bought a Corvair powered plane, and had no idea that the timing was ever to be checked. In the last 15 years, I have never had a single A&P ever call me and ask what he was to check on a Condition inspection on a Corvair. This means that almost all of the inspections were useless exercises that made people feel “Safe” when they were not.

B)    I have seen dozens of homebuilders who never followed up their airworthiness inspection with getting a repairman’s certificate for their plane. An inspection done by a builder without this is not valid, and if there is an accident in the plane, don’t expect the insurance company to pay nor the Feds to be nice either. Think this doesn’t happen? Guess again. I have personally looked at the books of a Lycoming powered homebuilt that had 9 consecutive non-valid inspections because the builder didn’t have a repairman’s certificate. But wait, it gets better: Because he was an airline pilot, he deceptively wrote “A+P” after his inspections to look like A&P. When I called him on this he explained that he was just writing the abbreviation for Airline Transport Pilot, ATP, and then he has the real BS line of saying “The ATP is really the superior rating to the A&P”. Before jumping to conclusion that no one ‘normal’ would do this, know that the guy is a retired flag rank officer and he flew more than 50 Young Eagles in a plane with fraudulent documentation.  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.  Flying a uninspected plane is something that people try to justify all the time. Just don’t be one of them.




Below, I’m going to list 11 steps that I consider a minimum to conduct an effective and valid Condition inspection on a Corvair Engine. These are gathered from my writing. There is nothing new here.


One)Get a copy of FAR-43 and read appendix D, it lists the minimum of items to be done to a power plant on an annual inspection. Your Corvair will need everyone of these done. The logbook entry when complete will specifically state that “This engine has been inspected in accordance with the scope and detail of appendix D”(


Two)Conduct an up to date information search to make sure your engine is up to current standards. All valid inspections require the inspector to reference the source of his technical data. If someone wants to claim on their insurance form the have an engine to “WW standards”, they have to reference my most current manual, (2014) and the technical updates I publish like the critical understanding series.  This means that the plane will have Denso Plugs, it will not have Chinese rockers, it will have a 5th bearing, etc. You can’t pass an annual inspection on a Cessna ignoring all the AD’s published in the last 10 years, and no logical person is going to argue that a Corvair engine that reflects none of the advancements we have made in the last decade is really as safe as reasonably possible.  The Log book should specifically state the date of the manual being followed and that all Corvair Service Bulletins have been addressed.


Three) Run up test. This is done to verify that the engine is running correctly. The full static rpm is to be noted, on each ignition, along with the OAT. The idle setting, and the drop with carb heat applied. The mixture, if equipped is to be tested. All engine instrumentation is to be checked for function. Any deviations from accepted levels or function are to be corrected.  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.


Four) Open the cowling completely, 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. Inspect the inside of the cap, the rotor and the wires. visible  wear is not acceptable. Oil leaks on the engine are not considered acceptable and are to be corrected as detected Carefully inspect balancer for any type of degradation of the elastomer. None is acceptable.

This is a good time to Check the prop. Re-torque the propeller to manufacturers specs. and enter this number in the logs, along with the next required interval for torque.


Five) Fluids and filters: The oil and filter must be changed, no matter how recently it was. The old filter must be cut open and inspected, and the element saved for later comparison. Any increase in the amount of metal compared to a previous element is reason for further inspection. Log Book to reflect, brand, type and quantity of oil.  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.


Six)Spark plugs, Denso only. While we used AC-R44F plugs for many years, We switched over to Denso plugs , both regular and iridium. We have several heat ranges we use with different displacements and compression ratios. They are the easiest, quickest, lowest cost way to add a much greater margin of safety against detonation to your engine. There is no reason why, years after we tested these plugs, that builders should not be using them, yet perhaps half the flying planes still have AC or some other brand plug in them. For the people who say “But AC’s worked fine, I’m still going to use them”  consider that before laparoscopic surgery, people s gall bladders were removed with surgery that was close to a midlevel broad sword wound. If you needed the operation, how would you feel if the doctor said “we are going old-school, it works fine.”


Seven)Compression test: Learn more here: Compression and Detonation Testing, #2 . 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.


Eight)Timing set with light on both ignitions Critical Understanding #4, ANY loss of RPM is Detonation.   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.


Nine)Two minute test Critical Understanding #6, The “Two Minute Test”   Write the OAT, DA, CHT, RPM and oil temp and pressure in the logs


Ten) One person test flight Critical Understanding #7, The Most Qualified Pilot, ALONE.


Eleven) Log book entry. Date and sign the logs with the final 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.

10 Responses to Yearly Condition Inspection on Corvair Engine

  1. Sarah Ashmore says:

    Not that I am endorsing their practices but I think some of those items that got mentioned are probably just a matter of the A&P not really knowing what to do since it was not an engine type they understood thus falling back to what they do know. Cleaning the plugs and reusing them is a common practice for aircraft given their cost so that would account for not just installing new ones even though that is common in automotive maintenance. Not checking or setting the timing would indicate that they did not know what to do since there were no magnetos so they did nothing. I guess none of them do any work on their own cars.

    • Sarah,
      Good points. At the root of it, we as graduates of “Riddle-Diddle Kite School” had it drilled into our heads that aviators don’t accept work they are not trained nor qualified to do. Evidently this guy missed that lesson.

  2. Guy Bowen says:

    It is possible that the A&P has never seen an automotive timing light…much less own one! Crank triggers, coil packs, and computers have nothing to set in many cases. They call this progress…adding a layer of abstraction to prevent meddlesome humans for messing with perfect engineering. Of course the downside to all of this is causes all of the kids these days to wonder what that funny-looking round coil pack at the back of an older engine is all about. It takes patience and intellect to swim through the connections within abstractions to achieve understanding.

  3. David Swann says:

    Hi William,

    I appreciate you putting all this info in one place, it makes it easy to use and I think more likely it will be used. I glad you are back too. I think that series of understandings will be prominent in my POH.

    David Swann

  4. Joe Pringle says:

    This type of tutoring is exactly why I chose to build a Corvair. I have read and re-read this site for several years and have built and run an engine. I am only just beginning to finally grasp some of these concepts. Thank you William for continuing to lay this information out in such a practical and forthright manner. It will probably save me from making a stupid mistake someday. I don’t know what I don’t know (unknown unknowns as Rumsfeld you put it).

    • Joe,
      You are a sharp crayon, a very accomplished guy who has obviously learned a lot in life. In all fairness, I think you have been learning all along. If the you of today could meet the you of your first day looking at building an engine, you would have a strong appreciation for how far you have come.

  5. Bob Lester says:

    Hey! Aren’t even car guys supposed to replace rotor and cap as a matched set. Sounds to me he’s a crappy car mechanic too. Your friend Bob Lester

  6. Andrew Elliott says:

    While I no longer have my Corvair-powered 601, here is the engine group from the condition inspection checklist in the POH. As WW notes, the plugs are outdated, but the rest is good.

    ENGINE GROUP (Corvair Engine)
    1. Warm up engine, check for fuel and oil leaks _______
    2. Perform cylinder compression checks (set TDC before removing plug!) _______
    #1 ________ #2 ________ #3 ________ #4 ________ #5 ________ #6 ________
    3. Check distributor cap and rotor condition, and check timing _______
    4. Drain and replace engine oil with 5 qts Rotella T 15W-40 or equivalent _______
    5. Replace oil filter with K&N filter HP-1008 or equivalent _______
    6. Check fuel filter element, replace if necessary _______
    7. Check spark plugs. Replace worn plugs with AC R44F gapped @0.038” _______
    8. Inspect L & R exhaust manifolds _______
    9. Inspect motor mount and fuselage attachment bolts _______
    10. Inspect urethane engine mount bushings _______
    11. Inspect condition, security &proper operation of throttle & mixture controls _______
    12. Drain carburetor, clean strainer and float bowl _______
    13. Inspect inlet airbox for leaks and cracks _______
    14. Clean and service inlet air filter _______
    15. Inspect cowling for damage and loose rivets _______
    16. Inspect firewall for damage and check pass-through seals _______
    17. Inspect cabin heat box for cracks or other damage _______
    18. Check starter and alternator mounts for security and damage _______
    19. Check condition of all fuel lines and connections _______
    20. Check condition and security of grounding strap _______
    21. Inspect all wiring for condition, security, damage, etc _______
    22. Run engine and check:
    a. No oil or fuel leaks _______
    b. Operation of fuel safety switch _______
    c. Operation on primary and alternate ignitions _______
    d. Operation on primary and alternate fuel pumps _______
    e. Operation on left and right tanks _______
    f. Idle RPM ~700 _______
    g. Static RPM at least 2700 _______
    h. All engine instrumentation operating correctly _______

  7. Marshall says:

    Well stated -! I find it amazing at times the things I see and hear with regard to inspections and airworthiness. Years ago when in training I was going over documentation to rent an aircraft from a FLIGHT SCHOOL, and upon finding it out of annual (and 100hour) by two days addressed the owner. He actually said- “ just get a cup of coffee, I’ll have a mechanic look at it and sign it off, be back in 30 minutes and you will be good to go”

  8. Gary Ray says:

    Twelve) – Update Pilot Operating Handbook. Things change. I still need to add William’s Critical Understanding series along with the full text so it contains the current specifications, limits and the reasoning behind them.

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