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a grin. I’ve departed in a Turbine Duke on a 5,000-foot runway and been at traffic pattern altitude before I got to the end of the runway – more grinning.
Why Would Anyone Not Move to a Turbine?
If you’ve got the coin and mission to make the transi- tion to a turbine, you’ll assuredly become a better overall pilot with added skills and new experiences to draw from. But there are also some really good reasons to stay in the piston world and almost all of them have to do with money.
First, a turbine is definitely going to cost you more cash to acquire. A large piston engine will cost about $100,000 to purchase, and a new conversion to a turbine will cost about $600,000. So, there’s a half-million-dollar delta to consider. I’ve found this to be about accurate for any con- verted airplane (JetPROP, Silver Eagle, Turbine Bonanza, etc.). A comparably equipped JetPROP from the same year as a Mirage will cost you about a $500,000 more. A single engine from-the-factory turbine (M500/M600, TBM, PC12, etc.) could cost you far more than an STC-converted turbine airplane. So, getting into a turbine will cost you at least a half-million more than a piston airplane, potentially more.
But, some turbines don’t cost all that much more to oper- ate. A Mirage and JetPROP can be operated for about the same cost per mile. The turbine will burn more fuel, but jet fuel costs less per gallon, and the turbine goes faster. An oil change will happen every 25 to 35 hours in a piston, but a turbine has an oil change every 800 hours. The turbine will cost more per hour to fly, but it gets a lot more done in that hour. I rarely hear from people who moved into the turbine world who are unaware of the normal operating expenses. It’s the abnormal expenses that cause a turbine pilot to cuss. I call it “turbine stupid” when a pilot makes a mistake in a turbine then gets to pay “turbine stupid tax.”
The classic case is a hot start. Every turbine has temperature limits, and when those limits are exceeded during the start sequence, it is called a “hot start.” The good news is that a hot start is almost entirely pre- dictable and preventable. No person should ever start an engine while being distracted or without proper training. A few seconds of distraction in a turbine can cost you dearly. Your turbine CFI will teach you how to avoid a hot start, but if you ignore those teachings, you’ll get to write a check.
When a hot start occurs, the engine will get a hot section inspection (HSI). A HSI is when the hot section is removed from an engine and sent to an engine shop. For this pleasure alone, you’ll pay about $15,000. Then, the engine shop will remove (and sacrifice) two blades from the compressor turbine, cutting them into pieces to look at the metal under a magnification. If the blades are heat damaged, all of the compres- sor turbine blades will be replaced. And
there are about 43 compressor blades in a small PT6 engine. Each one costs about $2,000. That’s about $86,000 for those doing mental math. But, the financial fun is not over yet. If the compressor turbine blades are heat damaged, they’ll sacrifice two blades from the power turbine and look at them under magnification. If they are heat damaged, all the blades on the first stage power turbine are replaced at another $2,000 each. And then, on some turbines, there’s a second stage power turbine with even more blades. The bottom line is that a hot start can easily cost $200,000 before combustion liners, stators, and other parts of the engine are considered.
But, the stupidity doesn’t stop there. A foreign object damage (FOD) event is when an object (ice, pebble, other debris) goes into the intake of the turbine. The compressor turns over 35,000 rpm in most turbines, and any debris will cause huge issues to the compressor. We can see the first stage compressor with a mirror or borescope, but if there’s damage to the first stage compressor blades, there’s almost always damage to every other stage in the engine. Damage to the first stage compressor that is not “blendable” (think sand down or smooth out) will result in the engine coming off the airplane and being sent to an engine shop. The costs of a FOD event are super-hard to predict, but none of the numbers are small. Sometimes a FOD event is covered by insurance, but sometimes not. Read your policy carefully. Most every turbine has an “ice door” or an inlet particle separator (IPS), and most are controlled by the pilot. Woe to the pilot who forgets to turn on the ice protec- tion when entering icing conditions, lands the airplane on a contaminated surface without the ice door ON, or who uses excessive reverse/beta frequently. A single hunk of ice slung from the prop can FOD an engine completely.
Then there’s the borescope. Every 400 hours you’ll want to conduct a fuel nozzle flow inspection. This is a super
May 2022 / TWIN & TURBINE • 13