Page 23 - Volume 15 Number 12

by advancing the power levers at whatever rate they choose to use. Based upon my observation of hundreds of pilots during King Air flight training, however, there is a simple and effective technique that I want to pass along.
It is rare that two different PT6s accelerate from idle at the same rate. Realize that the power levers do not affect fuel flow and power directly. Instead, they merely set a speedier spring tension that causes the fuel control unit (FCU) to reach and maintain a particular N1 or Ng speed, compressor speed. It’s the FCU that adjusts fuel flow and power in response to the pilot’s request for new N1 speed.
Since the FCU has “a mind of its own” about how to accelerate when suddenly told to go to a much higher N1 speed following a “throttle slam,” it is not uncommon to find that one engine will reach takeoff power before the other engine has even reached 30% power. Handling such a large power difference at low airspeed when the rudder is not very effective can be a challenge. Furthermore, it is impossible to know exactly what torque and ITT will finally be reached when the engine stabilizes and there is a strong probability that limits may be exceeded.
That’s why a couple of undesirable outcomes await the pilot who moves the power levers too far, too quickly, when faced with a “need-it-now!” high power requirement.
A better technique is to do what I call a “Bump and Run” with the power levers. When the stall horn starts to sound unexpectedly or when the deer suddenly appears in the landing lights in the flare, immediately bump the power levers forward as fast as possible but only about one-third of the way. “One one-thousand, two one-thousand, three one-thousand.” Pause for three seconds, then run the power levers forward rapidly as you watch the torque and temperature gauges, stopping when you are at or near takeoff power.
Why does this work so well?
Each position of the power lever corresponds to a unique N1. Since low idle is usually near 60% N1 and “full throttle” is slightly over 100% N1, our one-third forward “bump” means that we have requested about 73%, slightly more than high idle. To clarify, since the difference between 60 and 100 is 40, one-third of that is a little over 13. 60 + 13 = 73. No matter how mis-matched
DECEMBER 2021
KING AIR MAGAZINE • 21