The more things change, the more they stay the same. We have all heard that saying before, but it can certainly be true when it comes to engine maintenance inspections and overhauls.

AvBuyer  |  01st January 2011
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The AvBuyer editorial team includes Matt Harris and Rebecca Applegarth who contribute to a number of...

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Engine Overhaul:
Plane Sense on Engines Preparation is the key.

The more things change, the more they stay the same. We have all heard that saying before, but it can certainly be true when it comes to engine maintenance inspections and overhauls.

Every few years, aircraft engines require major inspections, and even though maintenance managers may have been through this process several times over the lifetime of the aircraft, the dynamics seem to change and create more challenges to preparing for an overhaul with minimal downtime. Preparation is the key and remains the bedrock of a successful engine overhaul.

As a result of the latest economic meltdown, some engine shops may be out of business, or have been purchased by other companies. This could create unexpected scheduling challenges, with potential cut backs in customer support personnel and limited capacity potentially hindering the process.

Certain rental engine types can also be in short supply, thereby increasing downtime for the aircraft, and making you rather unpopular with the boss when you have to explain these delays. To streamline the maintenance process, hourly engine cost maintenance programs are available to manage major engine inspections and overhauls for you and minimize many of the risks associated with these events. The companies that offer these programs have relationships with the engine manufacturers and maintenance providers, and are familiar with the different problems that occur. Moreover, they know how to prevent them. They can take the engine from start to finish, stopping many of the problems that can occur before they even become a problem to the operator.

The extra benefit of the hourly cost maintenance programs is that their programs are designed to cover the normal major engine event costs and help reduce financial repercussions caused by an unexpected catastrophic failure.

If you enjoy the benefit of an engine maintenance program, many of the following will either come automatically, or with a high degree of assistance. If your engines do not have the benefit of an hourly cost maintenance program, however, then you will need to undertake many of the same things these programs do for you; planning for major engine inspections early, and in detail. Below is a summary of the preparatory process for your next major engine inspection event, along with some pointers on how to complete it with minimal surprises.

Some engines need to have the planning done earlier than others. An event on a CFE-738 installed on a Falcon 2000, for example, requires more planning than an event on a TFE-731 installed on a Falcon 20.

A CFE-738 operator needs to understand that there are fewer rental engines, fewer shops that can do the work, longer shop times required, fewer replacement parts and fewer repair methods that have been developed.

The above issues occur on all makes and models of today’s aircraft engines so it is important to know your engine, and the advance planning it will require.

Another good practice is to know when your event is coming due, not only in hours but also in calendar days. The actual lead-time required to start planning for a major engine event or overhaul will depend on the engine make and model.

The selection of a shop is usually one of the most difficult parts of planning an engine maintenance event. For some engine models there might be a limited selection of authorized shops to choose from, and for other models there may be so many options that it is hard to decide which one to choose.

Always try to keep in mind that it is not only the name on the building that dictates if a shop is the best choice, but also the employees that are your direct contacts, working on your engine. It is always best to research each shop and obtain references from other operators. Don’t just ask about the quality of service and typical turn time, but also the communication policies within the company. Lack of effective communication can be the cause of delays and may end up costing you as much money, if not more, than any other aspect of the process.

Make sure you obtain, and use current research about the different engine shops. From year-to-year, a shop may have improved or declined in its ability and quality. To use outdated work history, rumors and opinions to determine which shop to contract could cause you to make a wrong and costly decision.

Scheduling major engine events in conjunction with an airframe event can save you the time the aircraft cannot be flown by performing the engine removals during the airframe event. If the major engine event takes less time than the airframe event, you may even save the extra cost of installing and removing of rental engines.

The availability of rental engines must be one of the primary concerns when planning a major engine event. The search for rental engines can have at least four different results, each of them affecting the schedule.

First: The rentals are available. This is obviously the best result you can ask for.

Second: An inadequate number of rental engines are available. You need two rental engines, and the shop only has one. Consequently, you are forced to plan for staggered engine removals requiring more down-time to perform the engine removals and swap each engine to the opposite side (also requiring significant paperwork hassle).

Third: The vendor has the rental engines, but they are not available exactly when you want them, creating the scheduling problem of not being able to get the work done on the engines when you would prefer. Now you have to align the schedule with rental engine availability. (The engine rentals are almost always provided when promised, but when they fail to show up it can be an unpleasant experience).

Fourth: There are no rental engines available anywhere near the date that you need them. This problem is caused by the limited pool of rental engines and is currently a challenge with some specific models.

You are advised to find out if your engines are one of the models with limited rental pools long before you have a major engine event due. These engine models require even more advanced planning for major engine events.

Make sure you research the status of your engines. Having a logbook review performed by an experienced engine technician up to six months prior to your expected engine event due date is a very good idea. There is not much you can do about failed components and repairs found during the major event inspection, but you can plan for the expected problems.

Knowing when your Life Limited Components (LLC) are required to be changed is also important, so look into your cycle’s per hour ratio early in the planning stages. If you have an LLC that is low on cycles, be sure to perform the calculations to assure when the unit must be removed. If that LLC has enough cycles to make the next major inspection then there is no need to have it replaced and cause any extra expense.

It is critical to verify that, if you are leaving an LLC in place until the next event, it has the required cycles remaining. There is nothing worse than having an LLC run out of cycles that requires an extra engine entry.

If you do have LLC that must be replaced, consider using continued time parts if they are available rather than new parts. Making an early decision on an LLC allows for replacement units to be found and positioned for installation during the major engine event, reducing the time the engine is in the shop.

LLC planning and pre-positioning is one of the best ways to lower your costs and engine time in the shop.

Deciding which Service Bulletins (SB) to p
erform during a major engine event could be compared to deciding on what medical procedure to have done. Some SB’s can keep the engine alive, others make it live longer, and some just add to the event costs! Make sure you look closely at Service Bulletins and always get a second opinion before you have them performed.

Even with all the changes in our industry in the last few years, all of the vital steps to prepare for a successful engine overhaul event remain the same. The Boy Scouts’ motto is “Be Prepared”. When it comes to engine overhauls, this should be the mantra of maintenance professionals throughout the industry.

Read More About: MRO


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