All About PT6 Borescope Inspections

Want to know a secret? You’re not buying an airplane, you’re buying engines!

Want to know a secret? You’re not buying an airplane, you’re buying engines!

The reality for most legacy turboprop aircraft is that the value of the engines is more than 80% of the aircrafts total value!

Even on later model aircraft, the engines represent a huge portion of the aircraft’s value and represent the greatest financial exposure to the prospective buyer.

From the perspective of an acquisition agent who specializes in jets and PT6 powered turboprops, I always cringe when I hear someone say things like “it had a fresh inspection” or the “engines were just borescoped”, actually I don’t just cringe at the second one I become physically ill.

There are only two reasons an engine was just borescoped, one is it was done as part of a normal maintenance event, the other is for prebuy purposes. The first isn’t in any way a substitute for a pre-purchase borescope inspection. The second is even worse, it is very likely that the results of the borescope are why the airplane was purchased by the person who paid for the last borescope.

There is a lot more to properly inspecting an aircraft prior to purchasing it. The borescope inspection of the engines I one of the most critical steps in the process. It is also a step that needs to be taken very early in the process, I’ll explain more and really get into the details later in this article, but should you choose to read no further, remember that a mistake at this point in an aircraft purchase could cost hundreds of thousands of dollars!

What is a borescope? A borescope is an optical device with a long flexible shaft and an eyepiece or camera at one end. There are two kinds of borescopes used for inspecting engines, for our purposes we’re only interested in a borescope with camera.

Are all borescopes created equal?

Always remember, pictures or it didn’t happen! This is important and you’ll find out why later.

When we get into the details of having engines borescoped you will find that like anything else technical, there are a lot of opinions and ideas. There can be a great deal of interpretation in regard to results, but for the purpose of this discussion we’re not going to address that. 

Here’s the first thing you need to know, a borescope can’t see everything, there are some potential issues that can’t be discovered by a borescope. We rely heavily on borescoping engines to uncover potential issues and expensive repairs, but there are some issues that cannot be detected with a scope. Blade length is one that comes immediately to mind, but there are others that include but are not limited to things that you simply cannot see with a borescope.

A technician who is very experienced may see some things others might miss, this happens. It happened to us earlier this year, we decided to pay to have Standard Aero do the borescope on an airplane that was a trade in to Textron. We could have saved some money by accepting the previous inspection, but that would have been a $200,000 mistake!

Spend a few thousand extra dollars and have a Pratt shop like Standard Aero do your borescopes. It’s the second best investment you’ll make when buying an airplane. 

Points to consider when it comes to borescoping engines:

  1. You need to have the right to borescope the engines as part of your inspection clearly specified in your letter of intent and / or purchase agreement. It is an invasive inspection that can result in the owner of the airplane having a large repair bill, it’s good to have something in writing that memorializes the agreement between parties.
  2. On certain occasions you may be buying an airplane with engines that are under warranty or on an engine program, such as JSSI or ESP Gold, it is extremely important that you have permission in advance to do the borescope inspection, doing the inspection without the provider’s advance knowledge can and in most cases will void the warranty or program.  

Why does the who matter?

The most economical way to have engine(s) borescoped is to have it done by the shop doing the prebuy, however that is NOT what we recommend. The reasons are two-fold:

  1. The first is that if we uncover an engine problem, it may be a big problem. In fact, it may be an insurmountable problem for the seller. It is not unheard of to find engine hot section repairs in a larger PT6 such as the -60A that cost well into six figures! If there is a big problem, we want to discover it before we’ve spent money moving the airplane and before we have given the shop a non-refundable deposit for the pre-purchase inspection.

    There is also a chance that what we find may be covered under an insurance claim, that’s fine but we want to get that process started as early as possible so that we do not delay the process and closing.

  2. The second and biggest reason that we want to use an engine shop to borescope the engines before we move the airplane is that they are more likely to find any potential issues and should they blatantly miss something they are actually in a position to do something about it!

Remember pictures or it didn’t happen?

If the tech was having a bad day and forgot to take that extra step, his omission will be revealed by the pictures, if something gets missed I want to be able to go back to a reputable engine overhaul facility and ask that they help make it right. The reality is that the shop doing the prebuy can correct something they miss, but if they miss an engine problem, they’d have to pay someone else to correct it. Thankfully, this has not happened to us, but I have seen it happen and it ended in court.

Our process isn’t the only way to buy an airplane, but we have perfected it over the years and our focus is solely on buying airplanes, so we’ve learned a thing or two along the way. The most important takeaway is that when you buy a PT6 powered aircraft, you must borescope the engines!  We believe that the best time is during the initial inspection and we believe that it is best to have this done by a Pratt and Whitney Designated Overhaul Facility (DOF) this has proven time and again to be an excellent investment and has saved our clients hundreds of thousands of dollars. Our preferred vendor for overhauls, hot section inspections, repairs and borescope inspections is Standard Aero (formally Vector Aerospace) if you have any questions or just need an extremely qualified tech to accomplish a prebuy borescope email and as always, I’m here to answer any questions you might have about acquiring turbine aircraft! 


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