Chances are good that if you’re managing a fleet of airplanes of any size, you have at least one person on standby who handles maintenance on those aircraft. It could even be you who takes on the role of maintenance worker, delivering checks and routine work to the aircraft to keep it working properly. Whether it’s you or a handful of others, the simple truth is that sometimes you may need to look beyond your staff and trust the team at a professional overhaul facility. Knowing when it’s time to get some additional help is important. Continue reading Knowing When It Is Time To Look Beyond Your Maintenance Staff
One of the most important requirements in owning an aircraft is understanding aircraft engine maintenance, so an aircraft engine overhaul may be necessary to keep an engine running like new. An overhaul consists of removing, disassembling, cleaning, inspecting and repairing an aircraft engine. Costs can run high with the extensiveness of an aircraft engine overhaul, thus it is important to know what to consider before choosing an overhaul company.
Aircraft engine overhaul is always required – this is one of the most important things to remember. Based on the Time between Overhaul (TBO), every aircraft engine must be removed, dismantled, checked and repaired as necessary. The engine, after being reassembled, is reinstalled in order to remain in service. For most engines, the TBO is 1,800 to 2,000 hours, which means many years between overhauls for a plane not flown often.
Asking an aircraft engine overhaul facility whether the work will be outsourced or done on-site is advised. A company that outsources the overhaul, even if it is a segment of the work, loses quality control over service completion. Therefore, be sure the facility you choose performs the work in-house.
Costs of an engine overhaul should be quoted based on the type of aircraft serviced and the time passed since the last overhaul. Price can also vary on which series of overhaul the customer requests. Facilities should not offer a “one-size-fits-all” price for aircraft engine overhauls.
The time for completing an aircraft engine overhaul depends on the type of aircraft and the series of overhaul requested. On average, an aircraft engine overhaul can take between two and three weeks, depending on the engine’s status and any approval delays from the customer for additional repairs.
When choosing a facility to perform an aircraft engine overhaul, it is important to look at what the price actually includes. A good facility should be able to give you a rough estimate of the time needed, inform you if outsourcing is required, and give you a cost estimate based on the type of aircraft and the series of overhaul desired. For more information on aircraft engine overhaul, join our online community on Facebook, Twitter and YouTube.
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As a final installment in our series of posts intended to demystify the aircraft engine overhaul process, we at Covington Aircraft want to detail the differences between using new and overhauled parts in an engine overhaul, so that you can make the best and most informed decision possible when TBO time comes around again.
When you’re looking to get an engine overhaul, a key point to remember is that the FAA does not require that all parts need to be replaced with brand new OEM equipment. While it is an accepted practice to replace parts such as pistons, rings, bushings, seals and gaskets, it’s also an accepted practice to reuse internal steel parts like connecting rods, the crankshaft, pushrods, gears and drive shafts, among others.
Testing and replacement
Even if they are reused, all non-new parts are carefully inspected and checked for cracks or defects via non-destructive testing techniques like Magnaflux and dye-penetrant tests. If a part fails to meet specified dimensional limits—either new limits or service limits, depending on the type of overhaul you’ve requested—it will be immediately rejected and replaced, regardless of the owner’s preference on the matter. The downside of this replacement is that some components come in matched sets, which means that a damaged single Planet gear may require the replacement of all Planet gears.
To overhaul or not to overhaul your parts?
When getting an engine overhaul, it can be difficult to decide if you should overhaul your existing cylinders or just replace them with new ones. New cylinders, if available, cost more than overhauling the cylinders you’ve already got. If your existing cylinders don’t have much wear, then it’s probably perfectly acceptable to get them overhauled and reinstalled. Remember that an overhauled cylinder still gets a new cylinder barrel choke and cylinder barrel honed finish, and the guides and seats are refurbished or replaced.
If you’re interested in further information on aircraft engine overhauls for turbine or radial engines, please let us know. We welcome questions and e-mails, and always strive to provide the best service possible to all our customers.
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Covington Aircraft has now been in business since 1979. Over the last 30 plus years, we have seen some Agricultural Aircraft owners who were riskier than even the most daring stunt pilots. How so? Well, they try, much like those who push the oil change on their vehicle, to put off as long as possible the overhaul of their engine. We focus on what to look for and Time Between Overhaul in this post.
The Ag industry often overlooks FAA Part 91/137 (Agricultural Operations) regarding recommendations for TBO, or Time Between Overhaul. TBO is overhauling an engine at the manufacturers recommended times. Often, Ag industry pilots are under the mistaken impression that PT6A engines don’t need these recommended overhauls, when this couldn’t be further from the truth.
SB 14503 (-67AG)
Pratt Service Bulletins governing TBO for this engine indicate that the first stage power turbine blades should be replaced at 12,000 hours, while second stage power turbine blades should be replaced at 5,000 hours. Compressor Turbine Blades with certain part numbers must be replaced at 6,000 hours. Main-line rotor bearings #1 and 4 as well as the first stage planet gear set’s sun gear should be replaced at 12,000 hours time. Considering these low hours, it stands to reason that the PT6A will not fly forever if the recommendations are not followed.
PT6A-34AG SB 1303
The 5000 Hour Check, which involves removing the disc from the hot section, removing blades from the disc, cleaning and conducting non-destructive testing, is recommended for the first time at 5,000 hours and at 3,000 hour intervals after that. This inspection also requires comparison of the actual length of the blade but they cannot be cracked. Cracked turbine blades or those stretched beyond limits could be devastating to an aircraft.
These two simple recommendations indicate that PT6A engines do not last forever. Failure to follow these recommendations could result in engine failure. In addition, Pratt & Whitney places significant importance on maintenance recommendations when honoring warranty repairs. Therefore, it is important that owners educate themselves on service bulletins and overhaul recommendations to avoid catastrophe.
If it has been too long of a TBO for you or you have general maintenance, sales, or overhaul questions, make sure you visit the Covington Aircraft website! Happy Flying!
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It’s not too often these days that you run across a company that still runs its overhaul maintenance business as it did when it started way back in the early 1970’s. Times have changed, but Covington Aircraft remains true to its core values when providing aviation engine service.
Covington Aircraft maintains a firm commitment to quality service and trust to both the corporate and agricultural aircraft markets throughout the world.