Frakes stacks solve soot problem

 - May 16, 2011, 9:20 PM

Owners and operators of Hawker Beechcraft King Airs enjoy the solid reliable performance offered by the venerable turboprops, but there is one King Air characteristic that probably isn’t appreciated, their propensity to turn nacelles brown with exhaust stains. Long-time EBACE exhibitor Frakes Aviation (Stand 434) has a solution: aerodynamically optimized retrofit exhaust stacks that route turbine tinges away, leaving nacelles clean and shiny.

Frakes Aviation has been manufacturing King Air exhaust stacks for more than 40 years, and its products are available for most King Air models, from the 100 through 300 series. Basically, any King Air powered by a Pratt & Whitney Canada PT6-20A engine or higher can use Frakes exhaust stacks, according to Joe Frakes, who founded the company with his father. The exhaust stacks are manufactured under FAA-approved parts manufacturer approval regulations and installed under an FAA supplemental type certificate, and they are also EASA-approved.

“About 1,300 King Airs are flying with our stacks,” Frakes said. The company also makes exhaust stacks for OEMs, including for Quest for the PT6-powered Kodiak and kit manufacturers Epic Aircraft and Lancair, and aftermarket PT6 modification companies such as Rocket Engineering, StandardAero and Blackhawk Modifications. “We have a fair number of development projects going on,” he said.

Stainless Steel

The Frakes exhaust stacks are made of stainless steel, which is easier to work with than the Inconel used by Hawker Beechcraft, according to the company. Stainless steel is also easier to polish, and most customers opt for the polished stacks. The company also offers exhaust stacks in a matte finish produced by glass bead blasting.

The warranty period for Frakes King Air stacks is seven years, with no flight-hour limitations. If the operator is based in the U.S., the company prefers to have stacks sent back to its facility in Cleburne, Texas, for repair or replacement if unrepairable. For operators outside the U.S., Frakes will evaluate the condition of the stack using digital photos then authorize a local repair or replacement. During 2010, the company didn’t have to replace any stacks under warranty, and during 2009, only one stack had to be replaced. “We don’t see a lot of repairs,” Frakes said.

Frakes is careful not to reveal the secret sauce that helps his exhaust stacks avoid depositing soot on nacelles and airframes. “Most operators of King Airs say we reduce stains by about 90 percent,” he said. One customer was washing the airplane every day after flying for two to three hours, but after installing the Frakes stacks, shifted to washing the airplane once a week. And this wasn’t to remove soot but accumulated bugs, according to Frakes.

“It’s aerodynamics,” he said, “trade secrets. It’s understanding what’s happening with the large picture of the airframe interface with the exhaust. We have many years of experience, lots of observation, and we work with a number of different aircraft. We’re fortunate to have a fairly extensive follow-up with aircraft that are local that we see frequently. On the King Air 200, even after [the stacks were] certified, we tried another five or six configurations and we couldn’t improve over what we were already shipping. In most cases [the other configurations] had degradation of performance and cleanliness.”

While Europe is a smaller market for Frakes Aviation’s exhaust stacks, it is worth marketing to European King Air operators, especially the maintenance shops that install the company’s products, he explained. Frakes Aviation has been a consistent exhibitor at EBACE every year since 2003 and has also branched into shows in Australia, Brazil and Singapore and made visits to South Africa. “We are trying to work the export markets, Frakes concluded. “A lot of it is built on long-term relationships.”

Comments

David Rose's picture

Hi - the stacks on my Lancair are looking a little ratty - what is the cost of a set for the Lancair lV PT with a PT6-27/28
Thanks
David

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