Page 20 - March 2022

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Why Do the Ailerons Have a “Lump”?
by Tom Clements
As the picture above shows, the ailerons on the King Air 200- and 300-series models include a pronounced lump on their trailing edges. The official name for the lump is “Trailing Edge Bulge” but, to me, they are simply “lumps.” The ailerons on other King Air models don’t have the lump. Presenting the reason why the 200- and 300-series have it and the other models do not is the purpose of this month’s article.
Longer aileron with lump.
The balanced ailerons that first appeared on the B90 made a huge improvement in roll authority and overall aircraft handling. Although the models 90 and A90 handled well, they feel “truck-like” when compared to the B90 and later King Air models. It feels like the newer airplanes have power steering and the handling qualities went from “OK” to “Wow!” The 100-series and F90-series reverted to the shorter wingtip extension and therefore have the same wingspan as the 90 and A90. However, the balanced aileron was now installed and the handling quality remained excellent.
Have you learned yet that the wing on a Bonanza and on a King Air not only have the same NACA Airfoil shape but they are the exact same size?! For as long as most of
The straight 65-90 King Air, as well as the A90 models, have ailerons that are hinged at their leading edges. Beginning with the B90 model in 1968, a wingtip extension was added. This longer wing needed more aileron authority and Beech addressed this need by building an aileron with more chord. Also, the hinge point was relocated. Instead of the hinge being fully
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forward at the leading edge, it was now moved back slightly. To be more accurate, the hinge actually stayed in the same place but the aileron’s extra chord was installed in front of the hinge. With this design, as the trailing edge of the aileron goes down, the leading edge goes up. This type of control service is referred to as being “balanced” and less force is required to rotate the control wheel.
MARCH 2022