A New Single Engine Speed Champ | Flying Magazine

A New Single Engine Speed Champ

Mooney's Acclaim may very well be the fastest piston-single on the block.

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The new Mooney Acclaim cuts a sharp image in flight, aided by a distinctive paint scheme.

Like just about everybody else, I first saw the Mooney Acclaim on the opening day at this year's Sun 'n Fun Fly-In, when Mooney unveiled it before a standing-room only crowd of aviation journalists and interested show-goers. The particular airplane that Mooney unveiled, N312TN, cut a striking figure on thegreen grass that sunny Florida morning, the airplane decked out dramatically in red and black with the image of an eagle, its wing extended in flight, cleverly worked into the scheme.

But it wasn't until Mooney CEO Gretchen Jahn, who'd just flown in nonstop from Texas, started talking numbers that people sat up and took notice. And the figure that got everyone's attention was for the high cruise speed-236 knots-which Jahn claimed to have achieved on the nonstop flight into Lakeland.

The 236 figure came as a bit of a surprise even to Mooney. Preliminary specifications only called for a 230-knot cruise, but on the trip out to Florida the true airspeed figures on the Garmin G1000 primary flight display were telling a faster tale, and a new story line was born. The Acclaim wasn't just going to be faster than any Mooney. It was going to be faster than any other piston-powered airplane in production. Or so it seemed.

The other contender to the fastest piston throne is the Columbia 400, another turbocharged airplane, though one significantly different in design from the Acclaim. With fixed-gear and composite construction, the Columbia 400 makes use of 310 horses, compared to the Acclaim's 280, to deliver its best cruise speed number, 235 knots. As is the case with the Acclaim, that kind of speed comes only at great heights, 25,000 feet, an altitude that few pilots are likely to fly on a regular basis in a nonpressurized airplane.

It's a common notion that the powerplant drives an airplane's design. In the case of the Acclaim, it's fair to say that the new powerplant, the Continental TSIO-550-G, is the Acclaim's design. The new engine allows the tried-and-true Mooney airframe to accelerate to the highest true airspeed ever for a production Mooney.

With the addition of the Continental engine, the Acclaim gets 10 more horsepower than the turbocharged Bravo, 280 compared with 270. The Acclaim replaces the Bravo in the Mooney lineup. The extra horsepower, combined with the new cowling, allow the Acclaim a gain of 15 knots over the Bravo (which also has a ceiling of 25,000 feet). And extra speed, as the jet crowd knows, means extra range. More on that in a bit.

The Acclaim is slightly different externally from other Mooneys, but the airframe basics from the firewall back remain the same.

The wingtips have what Mooney calls "mini-fins," slightly turned up wingtips, but if you're thinking that the aerodynamic advantage of such small tips has to be negligible, I'd have to agree. On the other hand, you've got to like the aesthetic boost they give the familiar design. Somehow this Mooney does look faster than its forebears. One change that's a lot more than cosmetic is a brand new cowling. The new cowl provides air cooling to the heavy-breathing TSIO-550 and eliminates the need for the cowl flaps that came on the Lycoming TSIO-540-powered Bravo. The new cowling features a pair of big annular inlets that channel the airflow to a center-located inlet that feeds the air to the engine compartment. The new air cooling scheme seems to be working well, which is always a major concern with turbocharged engines, which often run hot.

The Acclaim's new TSIO-550-G is derated to 280 hp, achieved by limiting manifold pressure. Mooney refers to the engine as being turbonormalized, but the distinction between turbonormalizing and turbocharging, if meaningful at all, is a subtle one. A widely accepted version of the term means that the turbo controller maintains the manifold pressure at standard sea level pressure, or 29.92 inches. But the Acclaim's engine is limited to 33.5 inches of manifold pressure, so a more accurate description might be just to say that the engine is turbocharged and features an automatic wastegate to keep the pilot from overboosting the engine.

At the risk of stating the obvious, the goal behind turbocharging is to allow the airplane to continue to develop maximum power as it climbs into less dense air. Normally aspirated piston engines can develop full-rated cruise power only up to a certain altitude, typically around 8,000 feet, or less, if air temperatures are warm. Once the normally aspirated engine gets much higher than that, power drops off and the airplane simply won't fly as fast. In contrast, the Acclaim's engine produces maximum rated power to around 20,000 feet.

It's also important to note that the Acclaim's recommended cruise power is 94 percent of the takeoff maximum of 280 hp, possible because the engine is normally capable of producing 310 horsepower as it does in the Columbia 400. The 94 percent power setting gives the Acclaim its full 280 horsepower, without pushing the engine any harder than a 310-hp rated version of the TSIO-550 when it's putting out 90 percent of its full-rated power.

Of course, there are downsides, and a turbocharged engine will add weight, run hotter and use more fuel. The last is largely a result of the engine being able to produce more power at higher altitudes, which requires more fuel. If they want their expensive engine to last, pilots will need to pay careful attention to the mixture control, though the task on the Acclaim is easier thanks to the lean assist feature on the G1000. That said, the Acclaim kept its cool nicely on our flight, and the company says that thanks to the new cowl and balanced fuel flow nozzles, standard on this engine, the powerplant at 25,000 feet can operate at 425 degrees CHT with a spread of just 15 degrees between the hottest and coolest cylinders.

Once certified, the airplane, like its stablemates, will feature the Garmin G1000 flat-panel avionics system, along with optional 130-gallon fuel capacity, TKS anti-icing-Mooney plans to get flight into known icing approval for the Acclaim-air conditioning and XM Weather and XM Radio. As is typical for preproduction flight-test airplanes, the Acclaim I flew for this report lacked all of those features, except for the G1000.

One of the most highly anticipated additions on the Acclaim will be the Garmin GFC 700 integrated autopilot, and anticipation might be the order of the day, as both Garmin and Mooney have signaled that the autopilot might not be certified in time for first deliveries. Richard Collins reports on the new autopilot in the Columbia 400 on page 86, and I had the chance to fly it in Garmin's Skylane a few months ago. In terms of capabilities, performance and features, it is the best autopilot that has ever been available for a light airplane. In part that's because it's the same autopilot as Garmin is making for all its G1000 airplanes, including the Cessna Mustang and Embraer Phenom 100 light jets, so the performance has to be good.

From the inside, the Acclaim looks much like other current Mooneys. The interior is stylish and comfortable, with its leather seats and leather-wrapped yokes. The new G1000 panel is clean and elegant. There are no mechanical primary or backup engine instruments, and the system makes use of dual-redundant batteries and alternators to power the two G1000 displays and the three backup flight instruments-they're third in line after the two redundant G1000 displays. In fact, the mechanical backups are placed so far over to the right that flying solely by reference to them would be quite a feat, though that's not likely to be an issue.

On my flight out of Kerrville, there were just the two of us, Mooney company pilot Paul Arrimbide and me. The airplane was full of fuel. We asked for and got FL 250, not something I ask for, or get, every day.

The takeoff roll was short, and as I do with Mooneys in general, I over-rotated a bit and then had to push forward. Arrimbide tells me that the feel of the Acclaim nose is a bit heavier than other Mooneys. It's more like a 182, he said. He's apparently more sensitive to such nuances than I am; I'd bet he hasn't flown a 182 in a while. The nose heaviness seemed subtle to me.

The airplane, N312TN, flown for this report is one of two preproduction examples undergoing flight testing towards FAA certification, scheduled for later this year. The Acclaim comes standard with the Garmin G1000 avionics system, including XM Weather and XM Radio, the S-Tec 55X two-axis autopilot with altitude capture and altitude hold and GPS roll steering, the Garmin GTX 330 Mode-S transponder with traffic services, and speed brakes. Because it is a test article, N312TN was not outfitted with the optional TKS anti-ice weeping wing system or with air conditioning, though just about every Acclaim ordered so far has one or both of those options selected. All specifications are from the manufacturer. Some figures are preliminary, pending certification.

On climb-out, we dialed in direct to Junction VOR on the G1000, made the turn and continued the climb. The initial rate of climb was around 1,300 fpm, but unlike most other piston powered singles I've flown, the Acclaim just kept right on climbing at that rate, or close to it. At 12,000 we put on the masks-the Acclaim has built-in oxygen-and at 18,000 feet we switched over to 29.92 on the altimeters, again something I'm not used to doing in a piston single. We were able to maintain 1,000 fpm on the VSI through and slightly beyond 20,000 feet. Even for the next 5,000 feet, we were able to climb at 800 fpm until we reached the airplane's ceiling of 25,000 feet. Total time from liftoff at Kerrville (including maneuvering) to 25,000 feet was around 25 minutes.

So, how fast is the Acclaim? Well, once we leveled off, we waited for things to stabilize, which took a little while. Once things were stable, the G1000-isn't it nice not to have to do the math any more?-was flickering back and forth between 234 and 235 knots. That's fast, as fast as the Columbia 400's top advertised mark, but not faster. But still, 235 knots in a piston single? Well, that's pretty darned impressive, and Mooney pilots have reportedly done a little better than that. The fuel burn was about 20 gph, though Arrimbide says that the fuel flows will probably decrease a bit as the installation is tweaked.

After making our turn back southbound at Junction VOR (the northern limit of Mooney's approved test range), we were cleared for the descent back down to 7,000 feet, a whopping 18,000 feet to lose. The speed brakes help, but Acclaim pilots will have to be careful to keep their descents shallow enough to protect their passengers' ears, which means pre-planning is important. One of the main benefits of a pressurized airplane is that even when you're descending at a high rate, the cabin descent rate is much more passenger friendly.

On our way down we leveled off at 20,000 feet, where our true airspeed was 225 knots at 22 gallons an hour. We stopped again at 10,000 feet, where we were truing out at a still impressive 208 knots at 22 gph. In fact, the Acclaim's performance at 10,000 feet is more impressive to me than its numbers at 25,000 feet. Ten thousand is a non-oxygen altitude that many pilots will actually use in a nonpressurized airplane when there's not mountainous terrain to top. At 208 knots, you can cover a lot of ground without burning a lot of fuel in the climb and without having to don the masks.

Speaking of range, the Acclaim is going to have a lot of it, though exactly how much will depend on how much the airplane weighs once it's certified and on how much optional fuel capacity the owner decides to add, 102 gallons or 130 gallons. Figuring an empty weight of 2,350 pounds, about 100 pounds more than the normally aspirated Ovation2-and that figure doesn't include air conditioning or anti-ice-the 102-gallon-capacity airplane will have enough full-fuel payload for a couple of svelte pilots and light bags. The 130-gallon airplane will be able to carry a single FAA-standard 170-pound pilot and about 100 pounds of bags. Of course, you can always leave fuel out, and it's likely that owners with the higher capacity tanks will get used to doing just that.

There's not a lot to say about the Acclaim's handling characteristics, mostly because they're so similar to other Mooneys, which is to say, the airplane handles beautifully. The biggest difference, as Arrimbide pointed out, is that the nose feels slightly heavier. Otherwise, even at higher altitudes it handles like a Mooney, solid and smooth. And it's good in bumpy air, too, the wing loading of 20 pounds per square foot helping to weather the ups and downs of turbulence nicely.

Approaching back to Kerrville, I slowed the airplane down and set up on a long final for Runway 12. It's important to remember that even though the Acclaim is a 235-knot airplane at altitude, it still wants to approach at 80-85 knots. In fact, keeping the airplane slow enough is key to making consistent landings. I bounced mine just a little bit.

Acclaim pilots will have to be sure that they have enough practice landing, as this new model is so fast and can go so far, in many cases they'll be flying right past airports they formerly would have landed at for fuel. Mooney is taking orders for the Acclaim, for which it expects to earn FAA approval and to make first deliveries before the end of the year. For more details about the airplane, visit www.mooney.com.

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