Plane & Pilot
Tuesday, March 26, 2013

Diesel With A Jet Heart


Cessna introduces a turbo diesel for the popular Skylane


Despite that, climb fuel flow will be almost exactly half of equivalent power on the turbo Lycoming airplane, about 12 gph. Ascending at 85 knots on a near-ISA day, the JT-A showed me a consistent 1,000 fpm all the way to 10,500 feet.

As we cleared the Wichita class C and pointed west toward Kingman, Kansas, for some landings, I leveled, set 90% power and watched speed walk around to cover 155 knots. That's the spec, and it's no surprise that it's very comparable to that of the T182T. Manifold pressure ran about 70 inches for cruise. If I owned a JT-A, I doubt if I'd ever get used to seeing that.

The diesel Skylane feels comfortable at max cruise—fuel burn is down to about 11 gph, the noise level is very civilized at the engine's constant 2,200 rpm and vibration is virtually non-existent. Skylanes have always offered a smooth ride; stable and not skittish in turbulence, and the JT-A only makes a good thing better. Critical altitude is 10,000 feet, and the turbo diesel will still deliver 75% power at the airplane's maximum altitude of 20,000 feet.

At max cruise, the 87-gallon capacity allows for seven hours' endurance plus reserve, enough for easy 1,000 nm legs. If you're one of those rare folks who likes to practice ferry flying, the JT-A will accommodate. Unlike avgas engines, diesels don't care what power setting you use. If the mission demands it and you're into masochism, you can retard the power on the SMA engine to 35% and endure for 14 hours, enough to cover 1,500 nm.

Since the JT-A has no aerodynamic changes, I wouldn't have expected any revisions to stall and slow flight manners, and sure enough, there weren't any. Directly over Kingman, I tried a few 60-degree steep turns, and the airplane had nothing new to tell me. It maintains all the habits of a Skylane.

Wilcox was eager to show me how the big diesel reacted to an in-flight shutdown, so we cooled the engine for a minute or two, then brought the power lever to fuel cut-off. At first, you have no hard indication that you've just lost power. The giveaway comes when you raise the nose and see the rpm begin to decay. The prop will continue to windmill even in a dirty stall, however. To restart, you simply bring the power lever out of the cut-off position to reintroduce fuel and let the computer do the rest. The point is that the electronic control unit simplifies shutdown and startup so much that there's almost nothing you can do wrong, it says here. I, Robot.

Stalls in a variety of configurations were next. The airplane hangs in there until airspeed is practically off the dial. The spec is 41 knots with flaps fully deflected. That means, in theory, you could maintain an approach speed of 50 knots and still preserve 1.2 times Vso.



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