In the world of corporate turboprops, 300 knots is something of a holy grail. Three hundred knots begins to intrude on jet country. Not many jetprops will manage such speed: the MU2, Cheyenne 400, Commander 1000 and perhaps one or two others.
Adding an STC’d conversion to the mix might seem like cheating, analogous to matching a full-race Porsche 935 against a group of stock 911s. Still, Darwin Conrad of Rocket Engineering (www.rocketengineering.com) in Spokane, Wash., has introduced a turbine-powered 58P Baron, and it does indeed nudge into the 300-knot club.
Conrad calls his modified Baron “the Cougar,” and it’s basically a 58P converted straight across with a pair of 500 shp P&W PT6A-21 turbine engines with fully reversible, four-bladed Hartzell props. The PT6A family of turbines is indisputably the world’s most renowned, with more than 36,000 in service in 170 countries. Included in the bargain are a pair of 200-amp generators and two 24-volt batteries.
The Cougar is the fourth in Conrad’s chain of P&W PT6A conversions. The other three are the Malibu Jetprop (a Piper Malibu/Mirage), the Turbine Air (Beech B36TC) and the Royal Turbine (Beech Duke). The new airplane employs the same engines used on the other three conversions.
Beech built about 500 pressurized Barons between 1976 and 1986, each with a pair of Continental TSIO-520s under the cowls. The 58P was an enthusiastic little twin, capable of an honest 210 to 220 knots, depending on which model you purchased (engine power varied between 310 and 325 hp).
I caught up with Conrad at EAA AirVenture 2009, and arranged to fly the prototype Cougar out of nearby Appleton Airport. This was the one and only flight-test article, and Conrad was halfway through testing for the STC award from the FAA. Conrad hopes to have full approval later this year.
Any time you boost horsepower by more than 50% (in this case, from 310/325 to 500), you can expect some major performance improvements, and that’s exactly what happened to the P-Baron we all knew and loved. Under the Rocket Engineering banner, the plane has undergone a dramatic transformation in personality while retaining the Baron’s gentle handling and endearing disposition.
Externally, there doesn’t appear to be much difference between the two airplanes. As with most PT6A installations, the Pratts are installed backwards in the nacelles. This places the power section at the front of the nacelle, where it can drive the propeller directly, without the need of a long driveshaft. Intake air is admitted through an inlet at the bottom cowl, and the twin exhaust stacks are mounted high on the sides of each engine. Aside from the Pratts, the configuration of the Cougar remains identical to the original Beech model.
Turbine engines always are lighter than piston mills, and the Cougar picks up 150 pounds of useful load per side in the transition from Continental to Pratt & Whitney. On the downside, turbines burn more fuel, and the Cougar adds 36 gallons’ more jet fuel to capacity, bringing the total to 222 gallons (1,487 pounds). Despite the extra fuel, the bottom line is a slight gain in payload, an additional 59 pounds.
As you might imagine, the panel has undergone a major transformation with igniters, fuel pumps, starters and generators mounted by twos down the left side. Engine instruments are modified to turbine standards, but flight instrumentation remains roughly the same. The test airplane sported a payload of 563 pounds with full tanks, three folks plus baggage.
That’s exactly what we had in the airplane for our first of two flights—me in the left front, Conrad at right front and pilot Peggy in the right rear executive bucket. Rear passengers board via a left rear side door that provides easy access to the aft cabin.
Despite the fact that the 58P uses the same fuselage as the 36 Bonanza—only 42 inches wide—it’s surprisingly comfortable. I’ve had the privilege of delivering a trio of 58s across various oceans, and the plane is universally a smooth riding machine: stable, willing and easy to fly.
When you bring the Cougar’s warp core online for takeoff, the airplane responds appropriately, almost as if it’s entering another dimension. Remember, you’re unleashing 1,000 hp to propel only 6,200 pounds of airplane. That’s 6.2 lbs./hp—better than virtually anything in or out of the class. (Even the Extra 330 unlimited aerobatic airplane manages only 7 lbs./hp.)
The Cougar comes off the ground in as little as 800 feet, and climbs as if it’s being shot at. Once the airplane is cleaned up and accelerated to 130 knots, you can expect to see the VSI swing around to 3,500 fpm or better, depending on load. Conrad claims he has been able to launch from the company’s headquarters at Felts Field (at an elevation of about 2,000 feet), near Spokane, and level at 25,000 feet nine minutes later, ATC willing.
According:planeandpilot
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