Tuesday, May 22, 2012
Improving On A Good Thing
The venerable Cessna P210N enjoys a welcome improvement
I flew the second delivery with Dr. Ray Landes on board, owner of a T210 that was in Vitatoe Aviation's shop for the upgrade. Landes wanted some firsthand practice with the engine, and he monitored power throughout our short, two-day, 1,900 nm trip. Landes kept careful watch on cylinder head temps and EGTs, and he maintained the former at a maximum 380 degrees and the latter under 1,550 degrees. If either temperature began to climb above acceptable parameters, standard procedure was to lean the engine slightly to reduce the heat, or in the worst case, to open the cowl flaps a notch.
That's exactly the opposite of the philosophy most pilots have embraced for years, and it takes a little attitude adjustment to wrap your head around the updated technique. If you run 50 degrees rich of peak and temperatures are too high, you richen up the mixture to bring them down. Running lean of peak, you do exactly the opposite.
Contrary to what you may be thinking, this is far from a new technique. A guy named Lindbergh used it on his solo, 1927, Atlantic crossing from New York to Paris, and later taught the technique to American P-38 pilots in the South Pacific during WWII. (This may have contributed to the long-range, P-38 mission that resulted in the death of Japanese admiral Isoroku Yamamoto at Bougainville, Solomon Islands, in April 1943.)
More recently, George Braly and Tim Roehl of General Aviation Modifications in Oklahoma championed lean-of-peak operation, primarily on Continental IO/TSIO-550 engines. Despite the evidence that lean of peak works, Braly and Roehl have been fighting an uphill battle to popularize the leaning method, and they've finally gained pilot acceptance in the industry.
Ray Landes and I launched, hoping to climb into the lower flight levels and see what the airplane could do. The smoothness of the IO-550 was immediately obvious, and lean-of-peak operation proved almost idiot-proof.
The trip turned out to be anticlimactic because of headwinds as high as 70 knots and thunderstorms over the Rockies and Sierra Nevada. We delivered the airplane two days later to Reid-Hillview Airport in San Jose, recording a max cruise of 190 knots TAS at a low 14,000 feet on the final leg from Long Beach to San Jose. Larry Vitatoe has seen 212 knots above 20,000 feet, and I believe it. That's about the same performance claimed for the redesigned 325 hp Cessna P210R.
Page 3 of 3