Honeywell Powered Cessna Caravan

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It may be hard not to think of "Pratt & Whitney PT-6" when one thinks of the remarkably successful "Cessna Caravan," but Alaskan aircraft mod shop Aero Twin hopes that in time it can change that perception with its 850 Caravan conversion, which it expects to have STC'd around the time that you read this.

The modification replaces the PT-6 on the Caravan with the Honeywell TPE331-12JR-701S, a 1,060-shp engine derated to 850 shp for the 850 Caravan. The TPE331-12JR, which was originally designed for the CASA 212 turboprop twin, has been in service on that airplane for eight years. Also included are a new, lightweight cowling, a four-blade reversing Hartzell propeller (in place of the three-blader on the original), and a gross weight increase of 360 pounds from the Cessna POH.

According to Aero Twin, the TPE331 option will give the Caravan improved payload-range, lower fuel burn, lower operating costs and improved anti-ice performance. Honeywell also claims that the TPE331 conversion will greatly improve performance for Caravans on floats, cutting water takeoff times in half, from 28 seconds to around 14 seconds. A starting system developed by Aero Twin and Kelley Aerospace for the 850 Caravan greatly improves the engine's cantankerous starting habits, says Aero Twin.

For the best bang for the buck, the company recommends that operators make the engine swap on the second overhaul, a more extensive one than the first. With a TBO of either 5,000 hours or 7,000 hours (depending on operator authorizations), the TPE331 will have as much as double the TBO of the PT-6 on the Caravan, and attractive ongoing maintenance programs from Honeywell can decrease the costs of regular maintenance, as well. The ballpark cost of the conversion is $675,000, though actual costs will likely be lower, as customers will be able to sell their used PT-6 parts (core, prop, etc …). Aero Twin estimates that, if performed at the PT-6's first overhaul increment, the cost of the conversion would be about $350,000. Moreover, the lower fuel costs of the Honeywell engine will pay dividends, as well.

Honeywell estimates that there are 1,200 Caravan 208 and 208Bs in service. Aero Twin is scheduling STCs, and it says that interest in the program is strong, especially among float operators, and that slots are filling up fast. For more information, visit www.850caravan.com.