Tips on Scheduling Engine Overhauls & Inspections

The difference between an aircraft overhaul and an inspection is essentially related to scale. An aircraft inspection is usually conducted on-wing and can be done on site with limited maintenance, ensuring the engine is at optimal operational condition, while an overhaul is a larger, much more time-consuming operation.

The aircraft engine inspection could involve the use of torches, mirrors and similar, relatively simple equipment to inspect various areas of the engine, such as fan blades or wiring. It is also likely to involve the use of a borescope, a camera on a cable that can be “manoeuvred through various parts of the engine to ensure the core parts are in proper condition”, Stewart D’Leon, Director, Environmental and Technical Operations at the National Business Aviation Association (NBAA), explains.

By comparison, an overhaul must take place at certain intervals, as determined by the engine manufacturer and outlined in the engine maintenance manual, says Robert Burda, engine product line specialist manager at Jet Support Services, Inc (JSSI), a provider of maintenance support and financial services to Business Aviation.

Overhauls are the most detailed inspections that take place on an engine, encompassing the inspection of individual engine components against the allowable criteria set forth by the OEM. The allowable criteria in areas like cracks, burns and missing material are minimal at this inspection.

“The reason for this is that the next overhaul inspection interval for this engine model could be thousands of hours into the future,” Burda says. “If these components were not repaired or replaced at the current overhaul, it could cause serviceability issues with the engine during continued operation.”

JSSI provides a range of engine maintenance event management services, working with both clients and MRO facilities. Burda notes that the cost and time involved in an overhaul will depend on the engine make and model, and said that material availability and MRO slots need to be planned well in advance to reduce aircraft downtime.

“If your operation doesn’t allow for the aircraft to be down, you’ll need to plan for lease engines to be installed to keep the aircraft in service during this maintenance,” he advises. “This could take more than 90 days.”

Regardless of whether an aircraft operates on a hard-time engine program or an on-condition maintenance program, “an overhaul-level inspection will not be avoidable forever”, Burda warns. It’s therefore important to understand the costs associated with these inspections; JSSI offers an hourly cost maintenance program (HCMP) with the aim of offering budget stability, he highlights.

Pay Now or Pay Later

Elliott Aviation provides maintenance, avionics, paint, interior, engine and accessory work across its four MRO facilities. In regards to engines, its focus is primarily line maintenance services, and it works with outside vendors to deliver the majority of overhaul and heavier inspections, says Mike Saathoff, the company’s Director of Sales Operations & Engine and Accessory Sales.

Saathoff said that at times of economic pressure – as was recently experienced due to Covid-19 – “there’s been a tendency for people to want to complete the minimum to be compliant to keep their aircraft in the air”.

He warns that operators should be sure to follow manufacturer recommendations, “because doing the minimum can push upcoming maintenance to be more expensive and cause longer downtimes”.

Operators should also be aware that capacity will be strained due to industry-wide staffing shortages, he adds. “Getting aircraft in [to the maintenance shop close to the event] may be a lot tougher than customers planned for, so expect to see input dates further out than they usually are.”

Be Proactive as Overhaul Approaches – Especially Today

Business jet operators should ensure they work with companies that are “experienced in your engine model and can provide guidance and communication throughout the maintenance event”, says Burda. “Working with the MRO facility to plan material in advance could be a proactive way to reduce aircraft downtime and the need for lease engine installation.”

Operators also need to be prepared for possible overhaul-level inspections pending the results of lower-level inspections, Burda says. “This can come at an inopportune time in the aircraft schedule if the potential inspection results are not fully understood and accounted for in advance.”

The supply chain issues experienced in aerospace and other industries in recent months should also be a focus for business jet operators, says D’Leon, highlighting that a lot of parts manufacturers are having trouble keeping up with demand. This means that operators must order any necessary parts well in advance, potentially affecting the timescale and structure of their inspection and overhaul work. Otherwise, a potential discrepancy or issue could cause downtime for the aircraft, unless it is in a flyable condition.

“In many cases, it won’t be,” D’Leon adds. “You need to be aware before you start your inspection that you could end up exceeding the timeframe you had scheduled, ultimately not returning the aircraft to service in the time you had planned.”

Stacy Hollis works for Duncan Aviation as an Engine Service Sales Representative. Duncan Aviation is a provider of a range of engine overhaul and repair services for several different OEMs and engine models.

Hollis says that business jet owners and operators should be aware that “currently in today's market everyone is experiencing manpower shortages, rental engine shortages, engine parts shortages and things of that nature” that are extending in-shop turn times.

Where it was once possible to schedule engine and airframe events just a few weeks ahead, it’s now a case of “the more lead time, the better”. For major overhauls, he recommends scheduling several months in advance. “Some airframe events need to be scheduled six months to a year in advance to secure hangar slots.”

Partly, this is because business jets are being used more heavily, Hollis suggests, meaning “these events are coming up quicker than they used to”. He has seen a number of situations over the past six months or so where customers “have reached the engine event interval, and they haven’t done any pre-planning”.

According to Hollis, this goes beyond financial considerations, impacting the ability to even place an aircraft into a facility and get the work done.

The message is clear. “It really comes down to scheduling months and months in advance.” Today, owners and operators facing near-term overhauls and inspections should be anticipating them, understanding the scope of work (both actual and potential), and putting in place as many plans as possible to ensure today’s industry-wide challenges don’t cause problems when their aircraft’s maintenance event comes due.

More information from:
Duncan Aviation: www.duncanaviation.aero
Elliott Aviation: www.elliottaviation.com
Jet Support Services Inc: www.jetsupport.com
NBAA: www.nbaa.org

Read More About: Engine Maintenance