Page 25 - Volume 15 Number 5

would apply enough force to allow “feet on the floor” flying with no rudder trim input while flying at VYSE (Blue Line) with the left engine feathered, the right engine at its full 850 SHP, and with the proper five degree bank into the good engine. The force value selected was close to 50 pounds. This brought the worst-case situation from 147 down to an easily-handled value of about 100 pounds.
Since the required rudder force decreases as the differential power decreases, there will come a point – as airspeed increases, making the rudder more effective, and as engine power reduces when a climb is no longer required – in which every ounce of required rudder force is being supplied by the boost system, even with no rudder trim input. In this situation, to maintain proper airplane coordination with feet on the floor, the “dead foot, dead engine” rule would cease to apply. Instead, we’d have to start pushing on the “wrong” pedal or crank in opposite rudder trim. Bud explained that this was the point that the design team selected at which rudder boost would stop working, and stop supplying any rudder pedal force.
An educational and fun demon- stration I have conducted during many flight training sessions is to be in the situation of an engine shut down with propeller feath- ered, full power on the other en- gine, and at Blue Line airspeed in a clean configuration climb. As mentioned above, in most cases the rudder trim wheel is very close to being centered. I tell the student to put both feet on the floor, to hold heading using ailerons only, and to start reducing the engine’s power a little at a time.
Let’s assume the left engine is the one shutdown. As the right engine power is reduced, the airplane wants to turn right – due to the right rudder force being supplied by the RB system – so the student dutifully turns the control wheel to the left, counter
clockwise, to maintain heading. Another minor power reduction leads to the same outcome. Soon it becomes obvious that airplane coordination is lacking. We are banked noticeably toward the dead engine with the skid ball displaced to the left. But then, as power is slightly reduced again, suddenly the heading swings left and the student roles the control wheel clockwise to get back on the assigned heading.
Well, looky there! We have “raised the dead” and are again flying in relatively correct coordination ... because the rudder boost just stopped working. Cool!
No, I am not advocating flying with feet on the floor and/or not using rudder trim! However, realize that rudder boost is helping when needed but is turning itself off when no longer desirable.
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JUNE 2021
KING AIR MAGAZINE • 23