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4 Answers

Cracks/holes in aircraft surface: Airworthiness

Asked by: 3282 views FAA Regulations, Flight Instructor, General Aviation, Private Pilot

Throughout my training, I had generally been taught that finding small cracks on the surface (Such as a fairing or cowling) was okay so long as the crack had been stop drilled and did not seem to pose an immediate threat for greater damage. 

However, today, while preflighting a Cessna 172, I found about a 1 inch hole in the cowling (Was more than just a crack) and noticed that there was at least one other spot on the other side of the cowling where another hole was beginning to form. I hadn't ever seen this before, so I wanted to get another opinion. 

I called the owner about it and he told me that this was a relatively normal occurrence and he would have someone fix it soon, but that it did not render the airplane at all unairworthy. He explained that the air directed by the baffling under the cowling can cause these holes to form from the inside. I asked another very experienced instructor I saw on the field and he seemed to agree that it was no hazard. 

That being said, this stirred up some questions in my head: 

  1. If an FAA inspector came out onto the ramp at that moment, in theory, how would I explain to them that the airplane was airworthy despite the holes?
  2. I can almost guarantee most DPEs or FAA inspectors would not find this airworthy for a checkride. What would their logic be as to why this aircraft is NOT airworthy? 
  3. What, specifically, is classified as structural damage? (From my understanding, this would not be classified as structural damage, but it got me thinking what the exact definition of structural damage would be?) 
  4. An FAA inspector once mentioned to me that an airplane should be in the general condition in left the factory in if it is considered to be airworthy. Is there a place in the FARs or anywhere else that it says this? I know an airplane should be in compliance with its type certification. Is this where it comes form?

I appreciate ANY insight into ANY of these questions and any other opinions on the subject. I am always looking to expand my knowledge, especially in the area of airworthiness and I know there are different opinions out there, so I'd like to open myself to as many points of views on this as I can. Thanks! 

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4 Answers



  1. KDS on Jun 19, 2018

    Look at Number 29 in this thread:

    https://forums.jetcareers.com/threads/738-flap-question.260376/page-2#post-2783369

    It’s airworthy. But, it worries people so much that the mechanics had to write that note on it.

    As a rule of thumb, if something doesn’t look right to you but you aren’t sure, ask a mechanic about it. If you trust the mechanic, believe him or her. If you don’t trust the mechanic, don’t bother asking that one.

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  2. KDS on Jun 19, 2018

    Also look at the first post in the thread.

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  3. SDAZskies on Jun 19, 2018

    Hey thanks for the reply. That’s an interesting situation on the thread you linked. I think I agree with your stance. After I thought about it some more, I have come up with the following:

    Any crack/hole/defect on the airplane initially renders it unairworthy (Because the airplane is no longer in the condition it was certificated under) UNLESS you, as the PIC, have a valid reason to believe that it does not pose a hazard to safety and does not hinder the aircraft’s ability to perform as required. This is where the grey area begins… But I’m thinking that as long as you can give a good explanation and back up your stance, it’s okay.

    I actually think that in your example with the “We know about this”, the airplane might still technically not be airworthy because the pilot wouldn’t have received a statement that the damage is not a hazard. The only way I think it would be okay is if the pilots KNEW that was an intentional repair. But otherwise, all the note says is “We know about this”, but it does not say it’s okay to fly.

    Of course, I’m assuming the crew knew about it in this case and could confidently make the airworthiness determination; but hypothetically if an FO walked around and didn’t know what that was, I’d still say he or she would have to go talk to someone about it to determine that it’s indeed an intentional repair. I don’t think the “We know about this” would be enough.

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  4. Best Answer


    KDS on Jun 19, 2018

    One other point. The inspector who told you that an airplane should be in the general condition it was in when it left the factor was speaking in very general terms. To be airworthy, an aircraft has to meet its type certificate and any supplemental type certificates (STC’s), have all required airworthiness directives (AD’s) applied, and comply with regulatory requirements (e.g. 91.203, 91.205, etc.).

    Just as an example, the propeller on a Cessna 172 does not have to be as it was when it left the factory. I don’t remember the exact numbers, but the type certificate says something like the propeller must have a diameter between 72.5 and 71.0 inches. When it comes out of the factory, it has a propeller that is close to the upper limit. Over time, mechanics file down the propeller tips. It’s no longer as it left the factory, but as long as it falls within the limits of the type certificate, that doesn’t make it unairworthy.

    The aircraft can also be modified from its original configuration through an STC. Here is one example:

    http://www.airplanetest.com/dc3.htm

    The subject of airworthiness is very complex and largely misunderstood. However, there isn’t a single regulation anywhere that says if you’re uncomfortable with something and you can’t exactly explain why that you have to fly the aircraft.

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