Tuesday, June 1, 2004
Congratulations, Columbia 400
Faster than a speeding bullet, able to leap tall mountains in a single bound, look, up in the flight levels, it’s the 230-plus-knot certified Lancair single!
I asked Lancair VP of engineering Tom Bowen about similarities between the homebuilt Lancair IV and the certified Columbia 400, and Bowen simply laughed. “Despite the deliberate family resemblance, there really are very few design similarities between the two airplanes,” explains Bowen. “Lance Neibauer [Lancair founder] obviously learned a lot from the Lancair IV design and incorporated those lessons in the 300, 350 and 400, but the certified airplanes are very different in almost all respects besides the obvious one of fixed gear.”
Bowen says that the company did consider using the Lancair IV’s 350-hp engine on the Columbia 400, but the tradeoffs wouldn’t have been worth it. “More horsepower can create as many problems as it solves. It has dramatic effects on the airplane’s structural analysis, landing gear, tail configuration, power-on stall characteristics, fuel burn and, therefore, capacity, payload, etc.,” reveals Bowen. “The problem is that max continuous cruise power on the TSIO-550 is 263 hp, no matter what the takeoff rating. We could’ve realized better climb from the higher power, but the 400’s climb is already excellent, and certification requirements would’ve made [the higher horsepower] a poor choice. As it is, the engine is rated for a maximum 85% of 310 hp rather than 75% of 350 hp.”
Turbos on the Columbia 400 are by AiResearch, and twin intercoolers reduce the temperature of induction air for more efficient fuel burn. Critical altitude is 25,000 feet, same as the airplane’s max operating height, so you’ll actually need to throttle back to maintain 75% at FL250.
The three-blade, semi-scimitar, Hartzell prop is larger than that used on the 300/350 and utilizes an airfoil developed specifically for high-altitude application. The dual intercoolers demanded extra space under the cowling and, accordingly, the prop is mounted on a longer hub that pushed the spinner forward, refairing the cowling and adding to the fuselage length.
To handle the extra power at high altitude, the Columbia 400 incorporates a larger rudder in both chord and span, along with a ventral fin beneath the empennage. “We needed a slightly larger, more effective tail because the turbocharged engine develops much more horsepower at higher altitude where the air is thinner and a given control deflection provides less response,” explains Bowen. “The anti-spin ventral fin is three feet long and four inches high at the leading edge. In combination with the big tail, it pops the airplane out of any spin almost instantly.”
“The elevator is modified, as well,” continues Bowen, “with a slightly different horizontal stabilizer. Unlike the Columbia 300 and 350 that were certified as spin-resistant, the Columbia 400 has been approved as spin-recoverable, a more stringent certification class that demanded a much larger matrix of spin tests.” Bowen emphasizes, however, that the Columbia 400 won’t be approved for deliberate spins in the skies.
“On normally aspirated airplanes, power-on spin entries become more benign as you climb higher because you’re losing power and slipstream,” says Bowen. “With a turbo, you’re making the same horsepower and generating the same slipstream at high altitude. For that reason, we redesigned the 350’s single-piece elevator to a two-piece unit on the 400 for more control. The two-piece elevator also enjoys more deflection for better control at high altitude and in the landing flare.”
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Labels: Piston Singles