Plane & Pilot
Tuesday, May 22, 2012

Improving On A Good Thing

The venerable Cessna P210N enjoys a welcome improvement

CESSNA P210N. Larry Vitatoe's Centurion conversion uses a factory-new Continental IO-550P engine with the 520's stock turbocharger, and adds dual intercoolers and a larger alternator.
Just as airplanes such as the straight-tail Beech Bonanza and Piper Super Cub have become pre-eminent in their respective classes, the Cessna 210 has enjoyed a similar reputation as an aviation icon.

Like the models above, the Centurion has hundreds of devotees who love their airplanes and wouldn't think of flying anything less. In the Centurion's case, the pressurized P210N was one of Cessna's most popular models, with over 800 sold in only five years. Like power windows, power steering, power seats and power brakes in a car, pressurization is one of those conveniences that's hard to live without, once you've adjusted to living with.

The total unquestionably would have been greater except for the airplane's short production life and some not-so-niggling problems on the early models. The P210 had the distinction of being the first successful pressurized single. Mooney offered the five-seat M22 Mustang in the late '60s, but the airplane was overweight, often ran hot and was perhaps too far ahead of its time. Mooney discontinued the Mustang after building only 36 M22s during a short, four-year production run. All 36 Mustangs were sold at a loss, and that undoubtedly contributed to Mooney's 1969 bankruptcy.

The first P210N was introduced as a 1978 model and also suffered an abbreviated life, eight years, though not necessarily because of its operational shortcomings. In 1985, Cessna president Russ Meyer ordered all piston models discontinued until congress could pass a reasonable statute of liability repose.

Though the P210's concept was outstanding, the execution was flawed. It seems there's always a, "Yeah, but…," waiting in the wings. Like every design, even aviation's most popular models have their share of flaws. The original P210Ns had some significant engine and system problems. Two of the early airplanes crashed, and the NTSB attributed both accidents to detonation from super-lean mixtures. The high temperatures associated with attempting to run the 210s at book-mixture settings caused extremely high CHTs that resulted in premature cylinder failure and exhaust cracks.

The FAA mandated extra-rich mixtures, about 21 gph at max cruise, and that resulted in higher fuel burns and lower performance. In May 1981, Cessna introduced a new turbo that was supposed to solve the problem but didn't. Instead, it reduced performance even more, forcing pilots to fly at lower altitudes and lower true airspeeds.

Cessna finally found a partial answer in late 1981 with a new induction system that utilized a larger intake scoop and redesigned air plenum. This added seven inches of manifold pressure, solved some of the P210N's problems, but not enough.


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