Page 22 - Nov24

They designed a new engine mount that holds the engine at four instead of three locations, lifts it 4 inches higher and has a new, more efficient ram air recovery design. The larger center section would provide more fuel capacity there to satisfy the bigger, thirstier PT6s used on the 200. Hmm, 170 more shp sitting 25 inches further outboard. Keeping Vmca down was going to be a challenge!
So off to the drawing boards and wind tunnel they go, experimenting with different tail configurations to find the one that would keep Vmca down where they wanted it. The conventional 100 tail wouldn’t hack it, and it was found that at the high angles-of-attack (AOA) associated with Vmca, the position of the horizontal tail was blocking much of the airflow up to the bottom portion of the rudder.
At that time, Beech had an agreement with Hawker that involved flying “green” airplanes from England to Wichita (with a portable avionics package, but no paint, options or interior) and Beech had the exclusive rights to finish them and handle all sales and marketing in North America. Based on their Hawker familiarity, they considered a cruciform tail, in which the horizontal stabilizer is about halfway up the vertical stabilizer. The only T-tailed civilian airplanes at that time were the Boeing 727 and the Learjet (long before the Learjet was “tamed” with Delta Fins and wing improvements),
and both had horrible stall characteristics. It was with reluctance that Beech considered the T-tail, fearing that the dreaded deep stall would follow.
Nevertheless, the computer/slide rule studies, as well as the wind tunnel tests, showed that the T-tail was best in maximizing rudder force. Not only did the new position of the horizontal surface not block the airflow to the rudder at high AOAs, but it also provided an endplate effect that captured the air and prevented it from spilling off the top of the rudder, thereby making the rudder even more effective. In one sentence, the T-tail design was chosen because it maximized rudder effectiveness and kept Vmca at a reasonable value.
The prototype 200, BB-1, first flew in October 1972 and onboard were a stick shaker/pusher and a rudder boost system. It also had no “bullet” on the T-tail and the ailerons and wing tips were identical to the B90/ C90/E90. An airflow interference problem showed up at the vertical/horizontal tail junction and was solved with the bullet. Aileron effectiveness at slow speeds was found to be waning, and hence the wing tip was cut so that the aileron could extend to the very end of the wing. This involved a third hinge point as well as the infamous trailing edge lump. Why the lump? To provide more self-centering tendency when this bigger, balanced aileron was fully deflected.
A side-by-side view of the T-tail on a King Air 300 and the conventional tail on a King AIr 100.
20 • KING AIR MAGAZINE
NOVEMBER 2024