Tuesday, May 20, 2008
Mooney Acclaim Type S: Still The Fastest!
If speed is your thing, The Acclaim Type S may be at the peak of the production pyramid
|To accelerate the Acclaim Type S, Mooney took the advice of LoPresti Speed Merchants and faired in the nosegear door, creating a smoother passage for air. The aircraft features a three-blade, constant-speed Hartzell propeller (bottom) and tricycle-retractable landing gear (above, middle). It also has a 43.5-inch-wide front cabin, spacious enough for two large pilots, and a sophisticated Garmin G1000 dual flat-screen avionics suite.|
Mooneys weren’t automatically born to such speed. The Texas company’s original Acclaim was a notably quick airplane, but Columbia Aircraft used to claim that its Columbia 400 was a knot or two quicker. Accordingly, Mooney launched into a speedup campaign to raise the ante and reassert its claim as fastest airplane. Cessna (which purchased the Columbia 350/400 assets and type certificates when Columbia went bankrupt last year) no longer fuels the competition. Cessna now claims the 400 as simply the fastest, fixed-gear, production piston single, with a top speed of 235 knots. Mooney suggests a top speed of 242 knots, and no one disputes the claim.
Top speeds are pretty worthless numbers, as hardly anyone is dumb enough to flog an engine at continuous max power unless they’re turning the pylons, even if the engine is rated for it (as is the Mooney’s). The Acclaim Type S spec is 237 knots at 75%, and I’ll take 239 as a close approximation of that any day.
Such brevity isn’t possible without plenty of horses out front. The Acclaim Type S features a Continental TSIO-550-G, considerably derated on the fastest Mooney, but pushed to as much as 350 hp in other applications. Mooney claims the engine is turbonormalized, which might suggest a manifold pressure red-line of 30 inches. Instead, twin Kelly Aerospace blowers provide the big Continental with a limit of 33.5 inches all the way to the critical altitude of 25,000 feet.
However you choose to define “turbonormalized,” power is copious and may be limited only by the size of the airplane’s vertical stabilizer. A former president of Mooney suggested that it was unlikely the airplane’s comparatively small tail could accept a 310 hp engine, like the one mounted on the Cessna 400 or Cirrus SR22-G3. (Obviously, any major aerodynamic change, such as a larger vertical stabilizer, would require a completely new—and very expensive—flight-test regimen for certification.)
Of course, pure power installed in any airplane is rarely an end in itself unless the airplane is named Rare Bear. [For more about Rare Bear and the Reno Air Races, read “Days Of Thunder” in Pilot Journal March/April 2008.] Power can introduce all kinds of expensive problems—higher fuel burn, a more forward CG, reduced range, lower payload—and doesn’t come close to generating a proportional, offsetting benefit. (The formula suggests that the speedup is roughly equivalent to the cube root of the power increase.) Given enough power, you could probably blast the Queen Mary into orbit, but power has never been Mooney’s overriding philosophy.
The most efficient answer may be a combination of power and improved aerodynamics, and Mooneys have always offered more than their share of slick designs, a tough task with a predominately all-metal airplane that’s, by definition, more difficult to mold and shape than composites.
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