Sunday, February 1, 2004
An Unusual Seneca II
Piper’s trusty twin was just a starting point for this revitalized PA-34 modification
With a total of 440 hp out front, 4,750 pounds of airplane to lift and 208 square feet of wing to do it with, the Seneca II is an enthusiastic climber. When lightly loaded, the airplane will deliver almost 1,800 fpm at VY. Pile in the pounds to gross and you’ll see more like 1,400 fpm. With turbos as standard equipment, climb holds up well at high altitude, too. Count on seeing 1,000 fpm or more through at least 14,000 feet.
Despite the extra horsepower and the benefit of turbocharging, single-engine performance isn’t quite so impressive. The book says single-engine climb is only 240 fpm, and that’s assuming you’re doing everything right. At least, you can take some consolation in the fact that the Seneca II’s dirty stall speed (62 knots) and VMC (66 knots) are so close, you may be hard-pressed to demonstrate VMC, especially in view of the fact that the right engine turns left, helping to balance the torque of the left engine. Senecas have always been too much airplane for the training role, anyway, and the diminished effect of VMC is a bonus.
Piper intended the Seneca to fly like a Cherokee with a hormone injection, and that pretty much describes the way Bass’s airplane feels in flight. Despite the fact that Senecas are twins, they try not to act like it. Run the throttles and props together, turn on the synchrophaser and you could fairly easily mistake a Seneca for a heavily loaded Saratoga with oodles more power.
Senecas are almost universally gentle to a fault, slow in roll and relatively heavy in pitch, but that’s desirable in a twin. Bob Hoover could probably do a great roll-and-loop routine, but he probably wouldn’t enjoy it. The type is almost universally stable and predictable in all flight modes. Like their derivative Cherokee Six design, they can run out of elevator at forward CG positions and tend to land flat if you’re not clever enough to keep the trim moving and leave the last notch of flaps up with only two up front and a heavy fuel load.
Flying at gross on virtually every flight, Bass typically sees a very consistent 181 to 182 knots at 75 percent settings, operating at 13,000 feet or less. Fuel flow on Bass’s updated II runs 29 gph total at 75 percent, 23.5 gph on those rare occasions when he uses 65 percent. “I know some pilots feel max cruise is a waste,” Bass comments, “but I always cruise at 75 percent, as fast as I can. Everyone’s entitled to do their own thing, but for me, it seems a little silly to buy an airplane capable of good speed and fly it slow.”
One hundred eighty knots isn’t that big a number, but you have to remember the basic Seneca is a very draggy airplane, though Bass’s example is cleaner than stock, with probably 10 knots more speed. The airplane has what is essentially a fat, Hershey-bar wing and few state-of-the-art aerodynamic tricks. Even if you climb on up to 20,000 feet or more, you’ll add only about 15 to 20 knots to true airspeed.
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Labels: Piston Twins