- 17 Feb 2020
- Dave Higdon
- Aircraft MRO
How to Understand Typical Maintenance Regimes
Bohlke’s Sam Black tells Chris Kjelgaard why owners and operators of business aircraft need to have a firm understanding of the impact and implications of maintenance, whether scheduled or unscheduled.
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Chris Kjelgaard
Chris Kjelgaard has been an aviation journalist for more than 40 years and has written on multiple topics...
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For any owner/operator of a business aircraft—and for anyone contemplating purchasing a business aircraft for corporate or private use—the need to understand the maintenance program for the airframe and engines is one of the most important requirements in choosing the right aircraft for the mission, and operating it as efficiently as possible.
“When you’re operating a turbine aircraft, you need people with experience of both the operating and maintenance side of the aircraft, for safety of operation, and the cost of operation,” says Sam Black, vice president, Bohlke International Airways—a long-standing BizAv-focused company.
“Maintenance is a significant part of the [overall operating] cost.” Bohlke, established 60 years ago, is based at Henry E. Rohlsen Airport on St. Croix in the US Virgin Islands and is now in its third generation of Bohlke-family management. Currently led by William ‘Billy’ Bohlke, it has a deep understanding of business aircraft maintenance.
Not only does it operate the longest-established FBO in the Caribbean region, Bohlke operates a diverse fleet of business jets and turboprops on FAR Part 145 charter flights (including many medevac and transplant-organ-transport flights throughout North and Central America and the Caribbean, in association with partner AeroMD).
Bohlke owns various business aircraft and manages and operates aircraft for their owners, while also operating a Part 145 licensed repair station called Tradewinds Flight Center, licensed to perform MRO on a variety of common business jet and turboprop types and PT6A turboprop engines.
For any new owner or operator of a business aircraft, “there’s a very steep learning curve” in gaining the knowledge and skills necessary to maintain it properly, says Black.
“There are many pot-holes along the way, so you’ll need someone who’s experienced.” If you’re not experienced yourself, make sure you go out and find somebody who is.
Two Types of Aircraft Maintenance: Scheduled
Typically, business aircraft are maintained under one or other of two types of maintenance regime, notes Black.
Scheduled inspections specified by manufacturers recommended maintenance programs are largely required at specified intervals measured either in the number of flight-cycles the aircraft accumulates following its last inspection or at fixed calendar dates.
For instance, King Air 200s require a phased inspection (often taking 2-3 weeks to perform) after every 250 hours of flight time, depending on the number of hours the aircraft has already flown and how much it’s utilized. (Older, high-cycle aircraft and those flown intensively may require more frequent inspections).
Similarly, the Gulfstream G100 has a high-utilization program which requires a major ‘C’ check every 1,000 flight hours.
However, various business jet and turboprop types can be maintained under progressive maintenance programs.
These allow the operator to split performance of the maintenance tasks required under what would otherwise be a 2-3- week downtime annually for an entire phased inspection, Black explains.
Splitting the inspection into smaller tasks over time gives the operator the flexibility to have one or more maintenance tasks performed on the aircraft any time it’s not required for flying.
That effectively allows maintenance to be performed progressively on the aircraft throughout the year, minimizing (or eliminating) any annual scheduled downtime required.
This practice is now common in maintaining many types of business aircraft, and potential buyers of business aircraft may find it useful to find out if the aircraft they’re contemplating offers a progressive maintenance program, whereby periods of mandatory annual downtime can be avoided or minimized, according to Black.
“Part of the purchasing decision is understanding the maintenance cycle of the airplane and ensuring it fits within the mission profile of what the owner wants to do,” he says.
That said, most aircraft types are still required to have a major phased inspection at certain intervals.
For example, Dassault Falcon 900s require an annual phased inspection (an ‘A’ check or ‘B’ check) every 12 months, and major ‘C’ checks every six years, according to Black. Major checks can take anywhere from 6-8 weeks to perform, depending on the size and complexity of your aircraft.
The frequency of inspection intervals required for a given aircraft type is dictated by the OEM.
But Black cautions would-be buyers and operators need to be aware that different versions of a given aircraft type will have substantially different maintenance programs owing to differing instrumentation, engine-performance, fuel-tankage and other operational characteristics and features.
Two Types of Aircraft Maintenance: Unscheduled
During their flying careers all aircraft will also require unscheduled maintenance, commonly known as line maintenance—which is often performed overnight, either at the aircraft’s base or at the airport it’s visiting.
Line maintenance ranges from minor tasks (such as replacing lightbulbs in aircraft cabins), to topping up hydraulic fluid, to potentially more major tasks (like repairing or replacing avionics equipment). It can also include performing minor or major engine repairs—the latter often following a bird-strike or ingestion of foreign object debris.
Unscheduled maintenance eventualities often lead business aircraft owners into considering their risk-management strategies.
One of the more major decisions can center on whether to acquire an older aircraft or to purchase a newer one (which in many cases would come with more warranty programs and offer more warranty options, according to Black).
A related consideration is whether to subscribe to an hourly maintenance program or to pay for maintenance as and when it’s required and incurred. Maintenance costs can typically be averaged out over a long period of time, so while a given airframe maintenance event may cost $80,000 to $100,000, its cost can be averaged out over 4,000 flight hours.
Some owners prefer the certainty of having an hourly maintenance program in place which covers and pre-pays almost all maintenance eventualities as they arise and makes the costs predictable.
“If you own and operate an aircraft, you need to be in the mindset that it is not unusual for maintenance events to occur unexpectedly, and that you have to have funds available to pay for them,” Black highlights, illustrating why hourly maintenance programs are popular today.
This is particularly true for engine maintenance, which is usually much more expensive than airframe maintenance, according to Black.
The cost of a given overhaul can vary massively from the previous one if the engine’s life-limited parts (LLPs) are nearing life expiry and need replacing. Any turbomachinery damage is typically also very expensive to repair.
As a result, “it is very common for you to see an aircraft on the market with an [hourly] engine maintenance program [tied to it] but not an airframe program,” notes Black.
“Really the biggest decision point for somebody buying a jet is that [for engine maintenance], do they want to pay hourly or pay at the time” the maintenance is performed?
In reality, as business aircraft age and become obsolete, or replacement parts for them become difficult to find, their engines represent more and more of the overall residual value of the aircraft—as long as the engines have plenty of operating-life “green time” before their next scheduled major overhaul and replacement of LLPs.
“At that point, owners tend to self-insure and deal with the maintenance [cost] as it arises,” argues Black.
But any buyers interested in, say, a Cessna Citation for $300,000 must be very aware that the value almost certainly reflects an aircraft with worn-out engines that would need significant investment to restore to full-life or even-part-life operating condition.
Caveat emptor!
More information from https://bohlke.com
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