And it's also a great thing for just tooling around down low, because the Thielert sips at the fuel, burning only around 6 gph at 75 percent power, compared with between 8 and around 10, respectively, for the R and SP model Skyhawks. This fact has generated a great deal of interest from fleet operators, because the prospect of collectively lowering fuel consumption and, hence, costs is an appealing prospect to flight schools and other volume buyers.
While it's called the "turbodiesel" model, Cessna chose not to certify it to burn diesel fuel, even though the engine in other applications is certified to use a certain grade of diesel fuel. But the lack of availability of that fuel in North America along with the ever-changing spec of automotive diesel here in the States convinced Cessna that the safer route would be to stick with old reliable jet-A, which is available worldwide and will be for decades.
One big goal for Cessna in certifying the TD was to avoid airframe-related changes that would require additional flight testing, and bear in mind that jet fuel weighs almost a pound more per gallon than 100LL.
To keep weights consistent between models, Cessna chose to limit the amount of fuel in the two wing tanks compared to the other Skyhawks. This makes it sound as though the TD customer is getting an airplane with less range, but not so. Because the Thielert engine burns less fuel, the TD's range/endurance envelope is actually very close to that of its gas-powered Skyhawk siblings.
One big concern is that aircraft fuelers will accidentally put 100LL in the TD's tanks, but Cessna has taken a number of steps to ensure that this doesn't happen. In addition to the hard-to-miss placards, the tanks are keyed (specially shaped, that is) so that only jet-A-and not 100LL-nozzles will fit. On top of that, there's a spring-loaded door that you need to press down on with the jet-A nozzle in order to get fuel into the airplane. So even if a boneheadedly persistent fueler opened the cap and tried to run fuel from an ill-fitting nozzle into the tank, the door to potential disaster would be closed.
I mentioned that the Skyhawk TD was easy to fly-well, as easy as any airplane is-but I definitely don't mean to imply that it's not a capable airplane, and in terms of avionics, it's remarkably so. The G1000 panel is integrated with the remarkable GFC 700 autopilot, which does a fabulous job of flying the airplane. This is, I should point out, the same autopilot that's in the Citation Mustang. (Remember if you will, that the first 172s entered production only a few years after electrical systems were standard fare in light airplanes.)
I won't give you much of a flight report on the 172TD, other than to say that it flies very much like any Skyhawk, smoothly, predictably, with a light and pleasing touch. Nothing about that equation changes with the TD.
I asked John Doman, head of Cessna's propeller aircraft sales, if prospective training organization customers were worried about how easy it might be to teach its clients how to fly the single power lever Skyhawk. He admitted that while there had been some questions, it wasn't a major concern, and he imagined that students would get add-on instruction on using conventional mixture and prop controls. The situation, he suggested, is a lot like what has happened with the move to PFDs, with add-on training offered to tell pilots about the bad-old days of steam gauges.
Back to the cockpit: As Dale and I climbed the Skyhawk up toward 10,000 feet to crunch the numbers, the most striking figure on the display was the percentage of power setting, which stayed at or very near 100 percent up through that altitude. Now, the Skyhawk is still no speed demon, nor is it meant to be. But the extra performance you get at altitude is a definite bonus.
The climb performance we saw was just as I guessed it would be, adequate down low and very respectable as we climbed. On our climb from Pawnee's 1,378 msl elevation up to 7,000 feet, we averaged right around 600 fpm on an almost exactly standard temperature day.
In cruise, the same trend held true. The TD did well at 5,000 feet and 100 percent power, with a cruise speed of 125 knots true on a respectable 8.5 gph, and at that same altitude at 75 percent power, it trued out at 112 knots on a miserly 5.8 gph. At 10,000 feet, an altitude where I would fly the airplane on many cross-country trips, the TD clocked a true airspeed of 130 knots at 100 percent power (well, 99 percent) and on 7.8 gallons of jet-A an hour. Pulling the power back to 75 percent power, we still saw 122 knots true on just 5.8 gph. The fuel savings at any altitude are impressive, and the increased performance at altitude was easy to see.
