- 15 Mar 2019
- Dave Higdon
- Engines - BizAv
How to Plan for Your Jet Engine Overhaul
What’s involved in planning for a business jet or turboprop engine inspection or overhaul, and what are the best practices and the pitfalls along the way? Dave Higdon reviews what you should be doing to plan your next event...
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Dave Higdon
Dave Higdon was a highly respected, NBAA Gold Wing award-winning aviation journalist who covered all...
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What’s involved in planning for an engine inspection or overhaul, and what are the best practices and the pitfalls along the way? Dave Higdon reviews…
The average annual flight times of today’s business jets run between 350-500 hours. On that basis, the owner of a brand-new jet with engines on a 4,000-hour Time Between Overhaul (TBO) cycle can reasonably expect eight-to-11 years flying time before the first overhaul is due.
They’d also be looking at four to 5.5 years before their first Hot-Section Inspection (HSI). That gives the savvy operator plenty of room to be preparing for those two seminal events in a business-turbine engine’s life cycle.
With this in mind we’ll consider the options available to operators who are watching the clock run down on those first TBO/HSI events.
Those options range from grounding the aircraft and acquiring access to a temporary replacement aircraft (supplemental lift), to leasing replacement powerplants in order to keep the company airplane flying while the powerplants undergo their renewal. A qualified overhaul partner is required, as is time-investment in producing adequate documentation and clarifying the costs.
Who Will be Your Engine Overhaul Partner?
The first item on your planning list should be to research and select in advance a vendor who is able to perform the work when the time arrives. That vendor should be capable of coordinating the other elements of the work package, including:
- Engine removal and re-installation;
- Shipping (where required);
- Test runs and acceptance flights.
Ensuring your overhaul partner is fully capable of coordinating the whole project, you’ll have peace of mind that you have a partner who knows the plan and can follow its progress closely.
How to Time Your Overhaul
It’s logical to schedule major engine-maintenance events, whether overhauls or hot-section inspections, for periods of low demand for the aircraft. So, you’ll need to analyze the data available to your flight department to know when those are likely to be. (Many operations follow the same philosophy when they’re establishing the annual inspection – required of all Part 91 operators.)
When a major engine event is due, the ideal would be to schedule it at the same time as the airplane’s annual inspection. This approach assumes you plan to do without the company airplane for the duration of the inspection/overhaul, in which case it may be necessary to arrange supplemental lift.
The benefit of minimizing downtime ranges from reducing your spending on supplemental lift (where necessary) to lowering the cost for loaning replacement powerplants while yours are being overhauled at the maintenance shop.
Whether to Use Supplemental Lift or Loaner Engines…
Deciding which path to follow while your engines are in the shop should be a leading question. If supplemental lift (ad hoc charter, jet card or wet leasing) is the likely route, time is needed to prepare.
In the case of charter and jet cards, advance-planning can often help secure fixed-rate and scheduling benefits while also affording you time to establish that the prospective charter company’s safety standards at least match your own high standards.
Alternatively, planned access to loaner or rental powerplants is an option that’s appealing to many operators investing in hourly engine maintenance cost programs.
Note that the benefits of a professionally managed maintenance program can help ease the load on an operator on every level, depending on the details of the program they’re enrolled with.
Support can vary from a turn-key process that is completely managed by the program provider, to more limited service covering the overhaul or inspection itself, but not the removal and re-installation of the engines, for example.
What About Engine Insurance, Shipping and Re-Installation?
When considering costs of an inspection/overhaul, you’ll need to factor the removal, re-installation, shipping, insurance and the work package itself (which very likely will include replacement parts).
Smart operators begin to plan on their overhaul when they acquire the aircraft.
When costing up the project, the above costs should be detailed in writing between the operator and the entities involved in the upcoming inspection/overhaul, and all vagaries need to be specified, including who pays for the shipping and who is insured for the insurable elements.
Copying Your Documents Protects Against Problems
The process will involve significant paperwork, and care should be taken to ensure continuity of all the required documentation. Generous duplication is recommended. Maintenance shops and hourly maintenance cost program providers recommend copious copying of documents and keeping of the duplicates as well as the originals.
In particular they urge copying of all powerplant-related logs.
The very existence of certified copies can be a real benefit should a document get lost, stolen or be involved in a shipping accident. The existence of the duplicates can also help streamline the process of recreating missing logs in the event they are needed in the future.
Is it Time to Address Other Maintenance Needs?
Given the downtime involved in sending in two engines for overhaul, you may want to look at other maintenance and upgrade needs you've been considering – especially if the engine work is timed to coincide with an annual inspection or other major maintenance event.
So, if you’re thinking of an interior refurbishment, new paint or an avionics upgrade, for example, it’s best to start considering such options a year or more ahead of the TBO due date.
Why Bother With the Acceptance Flight After Overhaul?
Following all the pre-planning leading up to the event, and the additional planning to keep your executives moving during the engine overhaul, one major step remains: The acceptance flight.
Essentially, a detailed test flight following re-installation of the engines should be arranged, and ideally the overhaul vendor will be on hand and involved in that process since there are big bucks involved.
During the acceptance flight you’ll be checking whether the engines make rated power, demonstrate normal operating pressures, temperatures, turbine speeds, lubrication and fuel flow. Once the engines have demonstrated their normalcy, they can formally be returned to service.
Now...Relax – Until the Next Time
If the process worked well and left you satisfied, this will also be a good time to assess the aircraft's future with your operation.
With a pair of freshly overhauled powerplants as well as any other work performed at the same time, it could be an optimal time to have the aircraft valued and to assess its viability as a trade-in or sale.
That aircraft is unlikely to ever be worth more than it is following overhaul and you'll be unlikely to be as prepared to consider such an option as you are now… At least until the next time an overhaul comes around.
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