Page 12 - Feb 20 TNT

MyGoFlight
the biggest piston engines they could find, selecting the 380 horsepower Lycoming TIO-541. But, too much is asked of the big piston engine on the Duke. Just about any turbocharged pis- ton airplane engine is really an engine that was originally designed for normal aspiration, and the turbocharging makes the engine work harder as aircraft de- signers seek more horsepower. In the Duke, the big turbocharged engine de- veloped a reputation for poor dispatch reliability and expensive maintenance invoices. So, the Duke became known as a really good airplane with really expensive engines.
What’s the best way to fix the piston problem on an otherwise rugged, func- tional and well-built airframe? Bolt on PT6s. That’s what Rocket Engineering figured how to do and created the Royal Turbine Duke.
The PT6-35 engine is installed in the place of the big Lycoming and everything changes. So, how’s the Turbine Duke perform? In short, the change in performance is spectacular.
Advancing the power levers of the Royal Turbine Duke is downright fun. The acceleration is brisk. No, that’s not strong enough language...the accelera- tion is amusement-park-ride spectacular. The Turbine Duke literally leaps for- ward and jumps in the air. At my home airport (KJSO) with a 5,000-foot runway, I can start at one end of the runway, take off, climb and reach nearly 2,000 AGL when I get to the other end of the runway. The angle of climb is greater than my Pitts S2B, an airplane known for ridiculous performance. The rate of climb when using full takeoff power easily tops 3,000 feet per minute and is oftentimes much more in a lesser-loaded Royal Turbine Duke.
Of course, such tremendous climb comes with a steep deck angle. A “nor- mal” climb in a Royal Turbine Duke is completed with higher airspeeds and lower deck angles. But, even so, the Royal Turbine Duke is a remarkable performer that is vastly overpowered.
Reaching the cruise altitudes in the mid-20s is easy and happens very quickly. A Royal Turbine Duke can reach FL250 in less than 10 minutes. Then, that tremendous rotate of climb is converted into forward speed, lots of
forward speed. I regularly see cruise speeds of 290 KTAS, and when the temperatures are right, I can see 300-plus KTAS.
So, with all of this good news, why isn’t the Royal Turbine Duke a hot com- modity on the market? Why have there been relatively few (about 20) conver- sions of the Royal Turbine Duke when there have been over 330 JetPROP conversions? The answer lies in the competition.
If you love efficiency, you probably will not love the Royal Turbine Duke. Basically, the Royal Turbine Duke is the exact same conversion as the popular JetPROP times two. Whereas the Jet- PROP burns 32 gph to obtain 260 KTAS, the Royal Turbine Duke will burn 64 gal- lons to cruise at 290 KTAS. The JetPROP is simply more efficient.
If you are willing to feed a twin, though, efficiency is not your thing. Power and redundancy are your thing. And the Royal Turbine Duke has gobs of excess horsepower. But, there are lots of other airplanes to consider if you like power and want six seats, and there’s even another Beechcraft product to con- sider – the King Air C90.
King Air C90
Admittedly, the C90 is not nearly as sexy, fast or sleek as the Turbine Duke. It won’t climb as quickly, won’t cruise as fast and won’t turn heads on the ramp. It is a ho-hum performer comparatively, but it is a performer that has no gaps in performance. It is not the fastest, but it is reasonably fast. It doesn’t carry the most, but it carries a lot. It doesn’t have the best short field capabilities, but it’ll easily handle most paved runways in the world. That is why the Royal Turbine Duke doesn’t sell as well. The Royal Duke wins in climb rate, cruise speed and short-field performance. But, the C90 beats the Duke in every other cat- egory – and in those categories where the C90 is in second place (climb, cruise and short-field performance), the C90 is no slouch.
If you have four people and bags, want to go 800 nm routinely and you prefer a multi-engine steed, you’ll probably look closely at the Royal Turbine Duke. But, you’ll also look at the King Air C90. And, the C90 will carry more, have a bigger
10 • TWIN & TURBINE / February 2020