Page 22 - May 2022

“Starting the 331 is a to- tally different process than starting a PT6.”
1983 was BE-137. All B100s were delivered with 715 SHP (shaft horsepower) TPE331-6-252B engines, all have a maximum gross takeoff weight of 11,800 pounds, with typical cruise speeds of about 250 knots. That speed is 15 to 20 knots faster than the realistic cruise speed of the 100 and A100. Because they have the short wingspan and the rather lowly 4.6 psid maximum differential pressure that is common to all of the 100-series, few B100s spend much time above FL220. Offering the same cabin dimensions of a 200 or 300, yet with significantly less fuel burn and rather good low-altitude speed performance, the B100
has proven to be a popular model among King Air charter operators. Also, it is much more commonly found in the eastern, rather than the western, portions of the U.S. due to its modest single-engine service ceiling.
Some B100s have been converted to the later-designed “Dash 10” version of the 331. These models exhibit increased climb and cruise performance as well as better availability of hot-section component parts. Another popular conversion is the Raisbeck Engineering modification that increases the maximum gross takeoff weight significantly.
As most of you know, the PT6 is a “free turbine” design wherein the Power Turbine (PT) that drives the propeller through the reduction gearbox is totally free and independent from the Compressor Turbine (CT) that drives the compressor. The TPE331, in contrast, is a “fixed shaft” turboprop, wherein all rotating components are fixed together and rotate simultaneously, although not necessarily at the same speed due to reduction gearing. The starter on a PT6 only turns the compressor and does not have to spin the mass of the propeller and gearbox. In contrast, the starter on the 331 must turn everything in the engine. That is why the PT6 gets by with a single battery but the B100 requires two of that same size. It also leads to huge differences in how the engines are started, operated and shutdown.
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20 • KING AIR MAGAZINE
MAY 2022