Plane & Pilot
Tuesday, September 24, 2013

Caravan With Enthusiasm

Blackhawk modifications of Waco, Texas, converts basic caravans to Super Caravans

Blackhawk's Caravan conversion upgrades practically everything forward of the firewall. The stock Pratt & Whitney PT6A-114A is replaced by a PT6A-42A, which increases shaft horsepower from 675 to 850.
A few years ago, Blackhawk certified a major power increase from 675 to 850 shp on the Grand Caravan 208B, a four-foot, stretched version of the original Caravan I. On June 10th of this year, the Waco, Texas, company earned certification of essentially the same conversion on the basic Caravan 208A.

Blackhawk's conversion upgrades practically everything forward of the firewall. The stock Caravan's Pratt & Whitney PT6A-114A turboprop is replaced by a PT6A-42A, increasing shp by 25% from 675 to 850. This is the same engine used in pairs on the popular King Air 200 for years, and it's proven to be one of corporate aviation's most reliable powerplants.

Any airplane that's the beneficiary of a 25% power increase is bound to score better cruise performance, and while that was definitely one of the goals of the power-up, Blackhawk CEO Jim Allmon feels the upgrade has changed the whole personality of the Caravan I.

"When we began working on the conversion," says Allmon, "we were looking primarily at the corporate and utility markets. We spent thousands of man-hours developing the initial upgrade, plus probably 250 hours in flight test. We felt the extra performance would be especially attractive to charter and business operators, companies that have a need for medium-range travel with five to 10 passengers.

"The airplane has proven very popular for that market," Allmon continues, "but we discovered we were overlooking another major group of operators— the skydiving business. We already have several owners who utilize our Grand Caravan conversion for high-jumping from ground level to 16,000 feet or higher, unloading jumpers and being back on the ground in under 20 minutes."

Predictably, the extra horsepower resulted in even better performance on the 208A "little" Caravan than it did on the stretched 208B Grand Caravan. The upgrade itself was very similar. In addition to installing the more powerful -42 engine, the upgraded Caravan features a four-blade wide-chord Hartzell prop, trimmed back from 106 to 100 inches in diameter. This provides slightly better ground clearance (and water clearance on the floatplane), as well as a marginally reduced noise level. The four-blade will be the standard prop on the Caravan conversion, but Blackhawk is continuing testing of a more efficient three-blade.

The conversion also incorporates a pair of stainless-steel Frakes exhaust stacks in place of the single right stack on the standard airplane. The Frakes exhausts are the result of extensive R&D into reducing back pressure in the larger engine. They're also the beneficiary of research into the optimum design and mounting position to avoid noise, vibration, fumes and possible heat waves corrupting image quality on air-to-ground photogrammetry missions. Many Caravans have been pressed into service for aerial photo-mapping work, and the additional stand-off of the Frakes exhausts helps direct the burned gases away from the airplane. A fringe benefit is the reduction of exhaust soot on the nacelle and wing. This is a big benefit for those in the cabin, as well. In the process, the Frakes stacks are streamlined to minimize drag.

Labels: Turbine Singles

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