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Engine Borescope Inspections Without Cause

October 2015

I'd like to start a discussion about a subject that keeps coming up day after day in the engine world. Is conducting a borescope inspection without cause a good or bad idea?  

There are times when the use of a borescope is called out in the applicable maintenance manual for the engine, and there are times when the use of a borescope is requested outside of the maintenance manual recommendations. This is what we refer to as cause.

There are only two conditions where the use of a borescope is appropriate...

  • Maintenance manual periodic inspection requirement (typically 'on condition' engines), and
  • When a cause has been determined due to a performance issue or possibly FOD event, such as a bird strike or contaminated runway conditions.

There is an Old-School philosophy believed by many that anytime an aircraft is bought or sold, it's mandatory to bring out the borescope and have at it. I’m here to tell you, it is not mandatory.

In fact, pursuing this course of action can result in serious implications to the aircraft owner’s warranty, either factory or after-market.

The engine maintenance programs, OEMs and Aftermarket, do not have limitless resources and will do whatever they need to reduce their exposure on high-cost events.

The issue arises when you insert the borescope into the heart of the engine without cause, as described above. If, during this inspection, there should happen to be findings that drive the engine to a shop level visit, the manufacturer’s program, such as ESP, MSP, Corp Care, is within its rights to pro-rate the affected parts by the actual time in service, as opposed to the amount of time the part should have stayed in the engine until normal scheduled access.

Depending upon when this happens in the normal inspection cycle of the engine, the owner’s program can be significantly impacted and charges for engines thought to be covered can be incurred.

The idea here is to keep the engines in service and not interrupt the normal cycle of scheduled events, i.e. shop visits, which are costly and take a long time to complete. This can be especially true given today's supply chain issues which seem to be pervasive across all engine OEMs.

Unless you've had a bad experience where an engine ingested something, like a tree or a duck or maybe all of the sudden a Trend Alert appears saying something has changed in the gas path, you have no cause to inject a borescope into the engine.

What Does This Mean?

This means a pre-purchase evaluation is NOT the time to pull out the old borescope. The timing is considered without Cause and will get you into a bunch of liability issues.

I understand the motivation. Aircraft buyers want to make sure they are not inheriting a pre-existing condition with the engines that are not covered by the factory warranty program or after-market program.

But the fact is you must get permission from OEM and after-market provider, like JSSI, before any borescope inspection is carried out without cause. They might even request being present to witness the findings. If the parties are not at least notified of the pending borescope inspection, they can refuse to support any of the findings, should there be any.

So, what is the solution?

To ensure the buyer is not inheriting a pre-existing condition that is not covered by an engine program, we suggest a FOD Evaluation, or Limited Use Borescope Inspection.

During this evaluation the engine inlet, fan hub and fan blades, fan by-pass stator, compressor inlet stator, and first stage LPC are inspected for any evidence of impact damage.

If all of these component parts pass inspection without any defects noted, you can be 99.9% guaranteed the engine has not suffered any ingestion of FOD, which is not covered by any program and falls back to insurance incident coverage.

Depending upon the engine application, a borescope may not be necessary to evaluate the first stage LPC. We use this at our discretion to satisfy the requirement, and it is not considered to be invasive.

With this evaluation you have satisfied the potential buyer, and the seller is not exposed to a potentially serious reduction in coverage.

For Engines Not On Program

For engines NOT on any program and completely out of manufacturer’s warranty, a fully invasive borescope inspection can be conducted with little worry of ramifications.

Just make sure BOTH parties (buyer and seller) are in agreement. Because if trouble turns up and the owner is handed a bill, the buyer may back out, and the one holding the borescope is also implicated in the findings.

This is touchy business; no one wants to be left holding the bag if things go horribly wrong.

My Advice

If the engines are on a program and running fine with no evidence of FOD damage, press on with the sale. Keep the engines on program, and if anything goes wrong with them, the program has to fix them.