Page 22 - April 2015 Volume 9, Number 4

Expressed in the more often-used terminology, Beta old-timers there regaled some of us with his “war
and Reverse can only happen when we are “off of the governor” or in an “under-speed condition.”
And, the easy-turning, free-turbine-driven propeller on a PT6 turns very easily, meaning that it takes very little airspeed or power to spin the propellers up to governing speed. Once the RPM becomes constant, the blade angle is now being controlled by the governor and is at some angle greater than the LPS angle. If we are no longer on the LPS, it makes no difference where it is.
The emergency descent procedure calls for using the landing gear extended speed limit as the proper airspeed. This varies from 156 knots to as high as about 180 knots, depending on the exact King Air model. Even with Idle power – also specified in the procedure – the propellers will still be solidly holding their maximum governing speed – and you’ll have the governor set for its maximum speed since the procedure also calls for prop levers being moved fully forward. In other words, you will be operating “on the governor,” not on the LPS, not in an underspeed condition, so moving the LPS back to flatter blade angles achieves absolutely nothing.
Two interesting notes: First, when I was a wet- behind-the-ears newbie instructor at the Beech factory and hadn’t learned enough to know better, one of the
story” about trying out maximum reverse in a King Air dive, and how the airplane pitched over almost straight down and was virtually uncontrollable until he moved the power levers back forward. Now I realize it was a story told to show how macho he was, but all it really proved was what a liar he was. Second, recall the placard on your King Air’s power quadrant, “Caution: Reverse only with engines running.” If you try to enter deep Beta or Reverse while sitting in the hangar or on the ramp with the engines not running, of course the propeller blades will be in the feathered position. That’s as far away from the LPS as they can get. If you now try to move the LPS, it cannot happen. Resistance on the lever’s cable will be felt and if some very strong and very dumb pilot continued to pull back, the cable could be stretched to the point that the whole LPS mechanism takes a real beating and gets badly out-of-whack.
Imagine standing outside of a closed, hinged door to a room. The door swings inward toward you. Grab the handle, pull, and the door opens. Now imagine that the door is already wide open, jutting out 90 degrees from the wall. Now grab the handle and pull. Nothing happens. The door is already at its widest open position and all you will feel is stiffness in your muscles as you pull, but the door does not move.
That’s a silly, but somewhat proper, analogy about what takes place if you select Beta and Reverse with the propellers not on the Low Pitch Stops ... you’re trying to open a valve that is already open!
So to summarize, if we pick up the power levers and pull aft during an emergency descent, all we will get is resistance on the levers, possible LPS mis-rigging, and no extra drag.
Let me relate one more story from my Beechcraft factory training days, and this one isn’t a lie. In about 1974, I was giving transition training to a pilot who had been flying a King Air A90 that his company had replaced with a new C90. A part of our flight training syllabus was to give a real engine failure during a two-engine balked landing exercise. Needless to say, we had a rule to do all real engine shutdowns at or above 5,000 feet AGL. Typically, we would start a “make believe” landing pattern at 8,000 feet or so, and end up with gear down, full flaps, and landing speed all set no lower than 6,000 feet. As the instructor yelled, “Deer on the runway! Go around,” he would pull one condition lever to fuel cut- off. The whole intent of this exercise was to show that the procedure absolutely could not be accomplished without losing significant altitude; that full flaps and one engine, near the ground, was a commitment to land. If the pilot tried to hold altitude, speed would quickly be lost, getting us even further from VYSE and definitely close to VMCA.

20 • KING AIR MAGAZINE
APRIL 2015