Engine Overhaul: Seek Expert Advice…

Any mistaken assumptions by an aircraft owner about an overhaul can add even more cost to an already-expensive process. But what do owners need to understand before the overhaul begins? Chris Kjelgaard considers the impact of improper storge, the quirks of ‘Sunshine’ parts, and the importance of expert advice…

Chris Kjelgaard  |  12th July 2022
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Chris Kjelgaard
Chris Kjelgaard

Chris Kjelgaard has been an aviation journalist for more than 40 years and has written on multiple topics...

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MRO worker undertaking a borescope inspection of private jet engine


Following on from his article ‘Engine Overhaul: What you Need to Understand’, we'll review some additional items aircraft owners and would-be buyers must understand ahead of an overhaul or other maintenance event…

According to Sean Lynch, Program Coordinator for Engine Assurance Program (EAP), when aircraft engines are not covered by pre-paid maintenance plans and decisions need to be made regarding purchasing those aircraft or sending their engines for maintenance, owners avail themselves of the expertise of an experienced technical inspector or A&P mechanic who is highly familiar with the engine type involved.

StandardAero reckons that owners will get the same level of expert advice from high-quality engine maintenance providers when the owners contract them for the engine work required.

“It really depends on how comfortable the owner or buyer is with making those decisions,” suggests Joe Capra, Senior Commercial Director, Pratt & Whitney Turbofans for StandardAero Business Aviation. “We recommend they find a qualified service provider that can answer their questions and is an organization they can trust.

“Reputable, OEM-authorized shops are designated by the OEMs and are FAA-approved to do this, meaning that the owner/buyer’s aircraft will not only meet our high regulatory standards, but also the OEM requirements for service.”

Today’s overheated used aircraft market is contributing to owner misunderstandings regarding engine maintenance costs — even more so given that supply-chain issues are affecting the prompt availability of parts, and the resulting cost of obtaining them quickly.

“The market is dynamic, and parts have become 20-30 percent more expensive in the last six months,” says Lynch, noting that the issue is affecting the prices of a variety of parts produced by different engine manufacturers for different engine types.

How ‘Sunshine Parts’ & Improper Storage Impact Maintenance Costs

Replacement of LLPs during unscheduled maintenance is a particularly onerous burden for aircraft owners. A single turbine blade can costs as much as $3,500, and when there are 72 of them on a single high-pressure turbine blade stage, the cost of replacing that stage and its turbine disk can run to $300k or more, Lynch highlights.

This type of eventuality raises another issue for aircraft owners — that of ‘sunshine parts’, LLPs and other parts which Lynch says may well be functioning completely normally and within operational parameters in an engine, but which airworthiness authorities require to be inspected for wear and tear every time the engine is opened up for unscheduled maintenance.

Should the mechanics working on the engine find any wear at all in any sunshine parts, airworthiness regulations require that they be replaced immediately with unworn parts — even if the replaced parts are still working and “are not the driving cause of the unscheduled maintenance event”, notes Capra.

This can have a major effect on engine maintenance costs and overhaul decisions. “They can be difficult to predict,” Capra says. Wear in sunshine parts is “largely dependent on total time since the last major maintenance event, the total run time, and operating environment. All are factors that can create engine wear”.

Improper preservation of the engines on stored aircraft is an important issue which can create huge cost and maintenance headaches for unwary, or naïve, aircraft buyers, adds Lynch.

The engines of stored aircraft are supposed to be run once a month, so the engines remain within the technical and regulatory condition requirements imposed by the maintenance manual. Engines not run for 60 days are subject to additional engine maintenance protocols.

A key requirement for anyone storing an aircraft over longer periods is to remove all oil from its engines. This is to ensure that any water entering the engine, for whatever reason, cannot bead up on the engine’s main bearing, Lynch explains. Should all oil not be removed from the stored engine and water beading occurs, this can cause corrosion in the main bearing.

Thus, any engine in long-term storage which contains oil must undergo a maintenance bearing inspection before the engine can be operated. Effectively this means the engine must be disassembled and undergo a full overhaul, Lynch says.

If you’re buying a stored aircraft, “your best protection is to be on a fully covered engine program,” says Lynch. “Or else you should fully understand what program you’re on and deduct the value of what it doesn’t cover from the purchase price” for the aircraft.

“If it’s not on an engine program, when you’re buying the aircraft you need a really expert mechanic who knows the engine and an expert technical inspector.”

Thus, any engines that are no longer being run on a monthly basis, and have not adhered to a long-term preservation requirement, must undergo a comprehensive bearing inspection before the engine can be operated. Effectively, this means the engine must undergo a full disassembly — which could turn into an overhaul, he says.

If you’re buying a stored aircraft, “your best protection is to be on a fully covered engine program,” says Lynch. “Or else you should fully understand what program you’re on and deduct the value of what it doesn’t cover from the purchase price” for the aircraft.

“If it’s not on an engine program, when you’re buying the aircraft, you need an expert mechanic who knows the engine, and an expert technical inspector.”

In Summary...

The best way for aircraft owners and buyers to avoid making mistakes regarding the scheduling, downtime and costs of engine overhauls is to “start planning major maintenance early”, Capra summarizes. “Three to six months in advance of required maintenance is recommended. Engine leasing, parts availability, and lead times should be considered.

“Also, seek direct consultation from engine repair and overhaul providers to help establish a budget,” he concludes. “The sooner operators speak with a technical expert, the more informed they will be regarding their options in handling their maintenance events.”

More information from
Engine Assurance Program: www.eap.aero
StandardAero: https://standardaero.com

Did you miss Part 1 of this article? Find Engine Overhaul: What you Need to Understand on AvBuyer.

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