Overhaul vs. Upgrade Evaluation Guide

Trying to decide whether to overhaul or upgrade your aircraft’s aging PT6A turboprop engine?

The best choice depends on a combination of factors, including your budget, your aircraft’s mission, your expectations for your King Air’s performance and, of course, the age of the engines.

The Age of Your Engines

For older engines, it may be simple economics. If you have a PT6A-20, -21, -28, -135, -41 or -42 engine model, the cost to overhaul and incorporate service bulletins and low cycle fatigue (LCF) components may not be that far off from upgrading to the new engine. Plus, upgrading reduces your maintenance costs. Not only does the engine include the manufacturer’s latest design and technology, which improves engine reliability, the engines shouldn’t require a shop visit for service bulletins, hot section inspection or overhaul for several years. Also, upgrading to new engines comes with a more comprehensive warranty. In short, if you look at the cost difference of brand new technology versus overhauling an engine model that was certified 30 to 35 years ago, it would likely be in your best interest to choose the new hardware. However, for a newer engine it may be more cost-efficient to go with the overhaul, especially if the engine is pretty clean, has been maintained well and doesn’t require a lot of expensive LCF components.

Weigh Your Expectations

Economics aside, what are your expectations for the aircraft’s performance and handling? Are you a CEO who needs faster speeds to quickly reach clients for frequent face-to-face meetings? Are you operating a charter service? Do you simply want more speed? The new engines offer increased horsepower or thermodynamic ratings, which translate into enhanced aircraft performance. With a better climb rate, you’ll burn less fuel. Improved takeoff performance and higher cruise speeds will get you where you need to go faster. If you operate longer haul segments, upgraded engines reduce the cycle time from point A to B and help you generate more revenue. The extra horsepower also adds an element of safety if you’re limping in on one engine. How much power or speed you can gain depends on the type of King Air. Some older King Air 90-series and King Air 200-series aircraft can certainly get performance improvements of 20, 25 or 30-plus knots. If you go from a PT6A-41 to a PT6A-52, you’re still flying at 850 horsepower, but you get a lot more torque at the higher altitude. With the PT6A-41 engine on the King Air 200, you start to lose torque at around 15,000 feet. With a PT6A-42, you start to lose torque at around 20,000 feet. With the PT6A-52, you don’t lose that torque. You’re up against the barber pole and you can nearly go up to the service ceiling well over 30,000 feet before you start to see the torque drop off. If you’re looking to tune your King Air 200 or B200 to get the most performance so that you can fly at 300-plus knots, that definitely requires upgrading your engines. All that power and performance comes from relatively new technology that has evolved over the last 10 to 20 years. For the King Air 90-series, the PT6A-135A engines have an enhanced compressor that provides more airflow. More cooling air through the hot section allows the engine to produce more power, and also run cooler.

On the King Air 200, a PT6A-42 upgrade also gains an enhanced compressor that allows the engine performance to be maintained to higher altitudes than with the stock PT6A-41 engine. Operators who upgrade to PT6A-52 engines reap the benefits of a PT6A-60A gas generator, which is on a King Air 300/350, but derated to 850 shaft horsepower. It features a much larger compressor with better airflow, and an upgraded hot section as well.

Plan Ahead

Before making a commitment, do some short- and long-term planning. Think about how you intend to use the aircraft over the next five, 10 and 15 years. Will you be selling your King Air in the near future or holding onto it?

Look for a service center with employees who are knowledgeable and experienced with PT6 engines. They’ll be able to give you good, objective advice about your options and provide better maintenance and installation capabilities than someone who is accustomed to working on other types of powerplants.

If you do decide to upgrade, you’ll have an enhanced warranty and worry-free operation for up to ten years before having to invest in a major maintenance event. If you’re selling soon, you may also want to consider the upgrade. It could help differentiate your King Air from its peers, boost resale value and give buyers peace of mind about the maintenance. Whether you choose to overhaul your existing engines or install new hardware, start considering your options at least one year in advance. Don’t start a few months before your overhaul comes due - it probably won’t leave you enough time to make the best decision. Plus, if you decide to go with upgraded engines, availability may be an issue. Factory lead times for new engines can be up to six months. Scheduling into a shop takes time, as well. Once the overhaul process starts, it takes about 30 to 45 days to complete.

Ask the Right Questions

How do you choose the right service center to perform the overhaul or new engine installation? Look for representatives who are knowledgeable and experienced with PT6 engines. They’ll be able to give you good, objective advice about your options and provide better maintenance and installation capabilities than someone who is accustomed to working on other types of powerplants. Be sure that the center you choose offers ongoing PT6 troubleshooting, service and support. That way, if anything happens with that powerplant, you know that they have someone who will answer your questions and provide field service, parts and troubleshooting support whenever you need it. Fortunately, you don’t have to decide on an overhaul or an upgrade immediately. Request estimates for both options. Maybe the estimate will show the engine is cleaner than you expected and you can easily extend its useful life with an overhaul. Or, perhaps you’ll find that the improved aircraft performance is worth the price of new engines. Either way, ask a lot of questions and talk with your sales representative about your expectations and how you plan to use the aircraft. Again, the key is to start early so you have plenty of time to decide.

About the Author

Kevin Perris holds a degree in Aerospace Engineering and is currently the Director of Engine Upgrade Programs at StandardAero. In this position, he is responsible for the company’s PT6 engine upgrade program, including new product research and development (Supplemental Type Certificates). He led a team in the development of new engine upgrades for the King Air 200 and B200 aircraft.