Timothy Ferrell is Senior Director of Engine Services for JSSI where he manages a global team of... Read More
Understanding the intricate details of maintaining the engines powering business jets today is complex, to say the least, notes JSSI’s Timothy Ferrell. Following are five key areas to help minimize avoidable downtime and expense…
There are so many important details to engine maintenance that, if ignored, even the savviest maintenance professional can be sent down a road filled with delays and added costs.
The following five tips are suggestions that should help you navigate the turbine engine maintenance process more efficiently…
1. Plan Ahead
Proper planning for any major aircraft maintenance event is crucial for staying on budget and making sure the work is done in a timely manner. For most turbine engine overhauls, preparation should start 6-12 months in advance. For some larger engines, however, planning should begin no less than 14 months in advance to avoid problems relating to the coordination of engine shop slots and rental engine availability.
JSSI works with customers on a rolling 2-year maintenance forecast. When managing the scheduled maintenance for a fleet of business jets in such a way, the need to plan ahead intensifies. Securing slot times at a facility for an overhaul that accommodates an owner’s schedule and coincides with rental engine availability, can be a challenge. Thus, starting the process at least six (or more) months in advance is important.
I have worked with operators that have waited until the engines are almost out of time before starting the overhaul planning process. The task of finding shop availability and rental engines on short notice can get ugly, quickly. And the hope of continuing to fly the aircraft without interruption gets replaced with delays and possible grounding because of the lack of forward planning.
2. Pre-Sourcing Materials/Supply Chain
Knowing what life-limited components require replacement at the time of the hot section inspection or overhaul will be invaluable because it allows for pre-sourcing of material that will save time and money.
It’s critical to define the list of Service Bulletins to be covered during the visit, not only for cost estimates but also to allow the facility to pre-order the materials needed to perform these tasks.
In certain circumstances, there could be a supply issue for a particular part, so securing a supplier for high demand materials is crucial. The maintenance facility can assist with this process by performing a logbook review in advance of the engine induction, which brings me to the second half of this tip, logbooks…
…and Accurate Logbooks
Unorganized and incomplete logbooks can create processing delays for the maintenance facility. It takes significantly more time to research the life-limited component and service bulletin status when the historical service records are not tidy.
Believe it or not, engines and many accessories are sometimes overhauled or replaced when they still have several hundred hours of time remaining on them. This can come from errors in flight log entries that lead to errors in maintenance records and maintenance tracking programs. Proper documentation that matches what is installed on the engine is essential to avoid any unpleasant surprises.
3. Rental Engines – The Devil’s in the Detail
Rental engine availability can be another big challenge, especially with newer, larger business jets that have limited engine inventory. And there are other details to attend to before the rental engine is ready to fly.
Prior to receiving the engine, there needs to be a bailment agreement, as well as proof of hull insurance and listing the lessor as a beneficiary on the hull policy for the time the engine is installed on the aircraft. This can take much longer than expected, especially when companies’ legal departments get involved.
The lessor usually expects the underwriter policy to have up to $50m in liability. A rental engine deposit may also be required and is usually 50% to 100% of what the expected charges will be during the term. Shipping an engine also requires insurance, whether it’s your engine or the rental engine. It should not be assumed that the facility or the lessor has it covered.
If the engines being overhauled are enrolled onto a maintenance program, many of these details may be included in the services provided, or they may be available as an added option to the program contract.
4. Desalination and Sulphidation
There are good reasons that engine manufacturers have desalination and compressor wash recommendations with detailed procedures in their maintenance manuals. Figure A indicates the four stages of sulphidation that can occur to CT blades. The desalination process is a prevention technique that can result in limited discrepancy parts when the scheduled overhaul is conducted.
Most washes with water-only are considered ‘desalination’ washes and are recommended for engines with minor sulphidation problems or those not operating in an environment where sulphidation can be extreme. Operating an aircraft within 150 miles of a coastline, will increase the risk for sulphidation and may require more frequent washes with a soap mixture.
Periodic borescope inspections may help evaluate the effectiveness of an engine washing program. All of these recommendations can be found in the applicable maintenance manual and are important to minimizing additional expense during the next scheduled event.
5. Scrap Material Approval/Losing Your Place
Once your scheduled maintenance event is underway, the shop facility will request a site visit to review all the rejected parts and material. As mentioned above, these shops run on a tight schedule, so the scrap material reviews must happen in a timely manner to assure the production line is moving and on schedule.
If your designated technician cannot be at the shop when requested, then most likely you will lose your place and have to go to the end of the line. This could mean a two-week delay or more, depending on the shop and engine type.
All of the above tips are important, but there are many more that can improve maintenance efficiency beyond the scope of this article. For example, a few years ago I probably would have replaced one of the above tips with engine preservation protocol. When the economy collapsed, it drove many owners to park their aircraft without the proper OEM recommended preservation process.
Today, we rarely see this happening because not only have OEMs reinforced the importance of preservation, but our industry has improved and most owners are flying more and utilizing their aircraft as the business tool they purchased them to be.