Page 22 - Volume 15 Number 5

ASK THE EXPERT
Rudder Boost History and Usage
Isometimes get questions along the lines of “Why doesn’t my King Air have the rudder boost system?” Many pilots flying an E90 or C90 receive a demo flight in a newer C90GTx and observe that the newer model has rudder boost whereas their airplanes do not. “It must be due to the higher power of the PT6A-135A engine as compared to the -20, -21 or -28 that we have,” is the common reasoning. And yet, all engine variants installed in C90s and E90s are limited to the same 550 SHP value. This article will attempt to shed light on this question and give some insight into the design and history of the rudder boost system. I wrote an article “Rudder Boost Ramblings” featured in the August 2020 issue of this magazine but there still seems to be a lot of confusion.
As I am sure you know, King Airs have the deserved reputation of being easy airplanes to fly with excellent handling characteristics. Even when operating OEI – One Engine Inoperative – they handle very nicely with plenty of trim authority to make “Hands Off” – and even “Feet Off” – flying quite easily accomplished. If this were not so, we’d probably see much fewer King Airs being used in the multiengine primary trainer role. Also, this good reputation applies even to the most basic of King Airs, those without such great “options” as yaw dampers, autopilots, rudder boost or autofeather.
by Tom Clements
20 • KING AIR MAGAZINE
JUNE 2021