Waypoints: Why your next engine may be a turboprop

September 1, 2010

Tom HainesDateline: 1990—Citing the product liability crisis in aviation and related dearth of piston-aircraft manufacturing, aircraft manufacturers consol-

idate product lines and focus on the more lucrative business jet market. Turboprops, despite the recent success of the Cessna Caravan, are projected to be the next market segment eviscerated. The King Air design is, after all, more than 25 years old.

Dateline: 2000—Citing the impending influx of new, “inexpensive” very light jets, aircraft manufacturers are phasing out their plans for turboprops, despite the recent success of the single-engine turboprops, Socata TBM 700 and Pilatus PC12. The King Air design is, after all, more than 35 years old.

Dateline: 2010—With apologies to the writer of The Graduate screenplay. “I have just one word for you…turboprops.”

Industry wags have been predicting the demise of the turboprop for the past couple of decades and yet turboprops continue to make inroads and progress.

Hawker Beechcraft has invested heavily in the King Air line for the last decade and the result is improved performance and breathtaking new panels across the King Air 90, 200, and 350 lines. The new 350 interior now features noise suppression and sophisticated cabin electronics that rival those in the highest-end business jets. The TBM 850, which replaced the 700 a few years ago, delivers well more than 310 knots cruise on about 60 gallons per hour. Its sporty handling and chiseled good looks make it a strong seller in the single-engine market. Meanwhile, “sporty” does not describe the Pilatus PC12. There, words like “rugged” and “utility” come to mind—as well as comfort in a King Air 200-size cabin.Piper entered the fray in the early 2000s with the single-engine Meridian. The entry-level Meridian has carved out its own niche at the bottom of the single-engine, pressurized turboprop market. The unpressurized Caravan soldiers on as one of Cessna’s top sellers. Kodiak, from Quest Aircraft, is a new single-engine, unpressurized turboprop that is making inroads in the backcountry market. Viking Air, meanwhile, recently announced that it began producing new turboprop versions of the venerable de Havilland Twin Otter.

The Viking announcement seems like the beginning of a tidal wave of turboprop announcements. Cirrus co-founder Alan Klapmeier surprised the world in late July with the announcement that he has joined forces with Farnborough Aircraft and other partners to form Kestrel Aircraft, which plans to certify the prototype single-engine, pressurized Kestrel model that Farnborough introduced several years ago. Plans call for the Kestrel to be larger and faster than the TBM 850, but smaller than the PC12. Rumors say Cessna is considering a pressurized single-engine turboprop. Hawker Beechcraft has been overly coy about supposed plans for a single-engine turboprop. Sometimes they doth protest too much.

So what gives? With efficient, new lightweight turbofans available—and proven now on the Mustang and Embraer Phenom designs, for example—why seemingly go backward in technology to a turboprop? The turboprop is a step backward at least from an overall efficiency and simplicity standpoint. Turboprop and turbofan engines are nearly identical at the core. While the fan engine simply leverages air flow and exhaust to create thrust, a turboprop requires an expensive and heavy propeller, governor, and gearbox, among other accoutrements, to create locomotion. Those developing single-engine jets said that they went the jet route because the engines are simpler—and about as cheap—by the time you add the necessary gear for a turboprop and jets give superior performance at high altitudes.

Join the fun

Tom Haines will host “Buying Your First Airplane” at AOPA Aviation Summit on Thursday, November 11. He will also be a featured speaker and will co-host a “Dine Around” event on Thursday. See the website for more information.

The reasons for turboprops are many. Most significant is runway performance. Turboprops beat jets every time because of the quick response time of the propeller on spool up and the prop wash over the wing and flight control surfaces, which improve takeoff performance. Similarly, upon landing the prop wash keeps the surfaces energized, allowing more control at lower airspeeds and reverse propeller thrust dramatically improves stopping. Adding thrust reversers to jets is expensive and heavy. An often-overlooked reason that pilots continue to buy turboprops is because of insurance and training requirements. Moving up to a jet demands a significant insurance premium and training investment, much greater than for a turboprop.

Rolls-Royce is developing a 500-shaft-horsepower engine that will be an appropriate size for many four- to six-seat singles, potentially opening up a whole new market of small turboprops—none of which have to worry about whether there is lead in their fuel.

The demise of the turboprop? Not any time soon.

Thomas B. Haines has served as editor in chief since 1994. E-mail the author at thomas.haines@aopa.org. Follow on Twitter: tomhaines29.