Time To End Unnecessary Borescope Inspections, Bizjet Experts Argue

An overabundance of caution may be scuppering some business aircraft sales and even, on occasion, leading to aircraft being grounded, according to a series of speakers during the Corporate Jet Investor conference held here in February. The problem arises when the buyer’s need for reassurance prompts detailed investigations using a borescope in the hot sections of the engine—which would usually take place during long-term scheduled maintenance checks—to be carried out during a pre-purchase inspection (PPI). Often this results in issues being found that would not have caused airworthiness issues or triggered remediation until the next major check.

“If you’re on an engine program, you run the risk of the seller being exposed to some serious financial [expense],” Zach Ungerleider, Honeywell’s MSP (maintenance and service plans) sales manager for eastern north America and the Asia-Pacific region, told a panel session during the conference.

“For example,” he continued, “if someone goes into an MSP-covered engine, and they go into the core with a borescope, you cannot unsee what you just saw. So, you run into a situation where the aircraft is rendered AOG [aircraft on ground] during the pre-buy, and if there are no rental engines available because they’re all on-wing serving other customers, then that aircraft may not leave the ground for another six months.”

The issue—which, speakers suggested, is happening with increasing frequency—appears to be a function of the complicated interactions between the PPI process, the scheduled maintenance cycle, the engine OEM’s maintenance programs, and well-intentioned advice being given to both buyer and seller.

Frustratingly, for all concerned in a transaction, sector staffers argue that these situations should never arise when an engine is on a program.

“It doesn’t make any sense to do a borescope [inspection] when you’re on an engine program,” said Steve Varsano, founder of The Jet Business, a London-based aircraft broker. “If anything is wrong it’s going to be taken care of anyway by the insurance program, and to go and look for a problem when no problem is obvious in any of the power indicators, any of the engine indicators, things like that ... Why go look for trouble?

“The negatives are, of course, if you open it up you can actually do damage just going into the engine that wasn’t even there before,” he continued. “You’re asking for trouble. The problem is, if the whole industry doesn’t get on the same platform and agree that we don’t need to do borescopes when the engines are on programs, then you’re going to look bad to your client if the lawyer or the other side argues against it.”

One example cited during the discussion—described as “one of the horror stories” by Delray Dobbins, global sales director for Engine Assurance Program, an independent provider of engine maintenance programs focused on supporting older powerplants—involved a sale where the seller allowed the buyer to do borescope inspections of the whole engine.

“Engines were rejected, no rentals available, now they can’t market the aircraft,” he said. “The findings [from the inspection] weren’t covered [by the engine OEM’s program] because there was no cause to go find them. Plane’s down for 10 months, and the exposure to the seller was probably upwards of $1 million.”

Borescope inspections will inevitably show some evidence of deterioration—degradation to fan blades from FOD (foreign object damage); corrosion—that a visual inspection will not pick up. This does not mean the engine is no longer airworthy, panelists argued: nor should buyers assume that such wear-and-tear needs to be rectified before purchase.

“Our LMM [line maintenance manual] will basically return an aircraft to service if a visual inspection does not reject a fan blade for FOD damage,” Ungerleider said. “If you can return the airplane to service per the LMM with a visual, there’s really no reason to go into the core of the engine on a fact-finding mission. We issue that guidance, and it’s based on the actual line maintenance manual of the engine.”

The reasons why borescope inspections are requested are easy enough to understand. A buyer will be reluctant to spend millions on an aircraft without carrying out a full series of checks. The seller, aware of the risk of grounding a perfectly functional airplane simply by looking for imperfections that do not affect airworthiness, will be reluctant to agree. When the buyer is told the seller does not want to have the borescope inspection carried out, the buyer may conclude that the seller is attempting to hide a known fault.

The solution, panelists argued, is a mindset change throughout the industry—one that reflects modern engine-monitoring capabilities. The practice of carrying out borescope inspections on hot sections during airplane sales dates from the 1980s and 1990s, Dobbins suggested, when detailed engine health-monitoring data were not available.

“What the buyer really should be focused on is the engine health data,” he said. “The engine health data gives you a hundred times more confidence of the health of the engine than just putting a borescope in the hot section.”

Just as important, he argued, is that buyers have realistic expectations. Citing transaction documents he has seen in recent years, which required engines to be “within all manufacturers’ specifications and tolerances,” Dobbins called for changes to be made to legal boilerplate.

“You’re not going to put a borescope on a 5,000-hr. engine and find that hot section 100% within tolerances,” he said. “If a buyer wants something 100% within tolerances, he needs to go and buy a new aircraft.”