Page 22 - Volume 11 Number 6

air “sideways” as they rotate we have zero taxi thrust. Plus, it is quiet!
So, what is this “situational awareness” I mentioned? First, although the propellers feather quite rapidly – just a few seconds – they take as much as 30 seconds to unfeather. So, if you will need positive taxi thrust to make it up that hill ahead or to maneuver with some tight turns on the ramp, it is not the time to feather. Second, we must remember that it is only safe to feather when the power levers are at Idle, not back in Beta or Reverse. Third, if we roll to a stop and leave the props in feather, there is a chance that our hot exhaust gases will not be blown safely away, but may negatively impact the nacelle and nose paint, oil temperature, as well as cause overheating of the nose- mounted avionics boxes. Remember to push those prop levers forward when stopped.
This in-and-out of feathering while taxiing is especially useful is we have found that our dead band is too small – N1 is picking up too early – yet the mechanic has not yet had time to adjust it properly. It is easy to taxi without residual thrust, no matter how messed up our rigging is, by using the feathering technique.
Also, remember this useful “trick.” When starting to taxi, if the airplane does not begin to roll when the brakes are released, try a quick in-and-out feathering instead of an application of power. Isn’t that cool?!
The momentary bigger bite of air is just what was needed to make the plane begin to roll, yet with zero chance of blade erosion.
Another time that it is easy to erode the prop blades is during high-power run-ups. For example, the Overspeed Governor test requires a lot of power. Please make every effort to find and use a rather clean, paved area of the tarmac when conducting your checks.
Similarly, consider the condition of the runway as you initiate the takeoff roll. If it is unpaved or the pavement is in poor shape, now is the time to make a rolling takeoff with power application coming in proportionally as the airspeed increases. Of course, when the runway is of minimum length, we won’t have the luxury of slow power application. But when there is excess runway, it is a technique that has merit.
How about landing? How do we avoid blade erosion now when we need and want to use Reverse? Easy answer: Go in quickly and deeply, then get out.
For a landing where aggressive Reverse will be used, it is common to run the propeller levers full forward well before touchdown so that we waste no time moving them after touchdown. All we have to do is lift and pull the power levers aft. Here is a time that aggressive, fast action is indeed called for and won’t harm a thing. Remember when I stated that Maximum Reverse is less than 50 percent power? Hence, there is no way that torque, ITT, not N1, is of any concern to you, the pilot, when those power levers are buried all the way back. “Slam” is a word used rarely when talking about flight and engine controls but, truly, here is the time to slam those power levers into Maximum Reverse without delay. Also realize that the power levers move in an arc, not in a straight line. To position them at Max Reverse requires more of a downward push during the last bit of travel, than an aft pull.
There are three important reasons for obtaining Max Reverse immediately. First, the sooner we can establish full reverse thrust, the shorter our landing distance will be. Second, the drag that Reverse provides is dependent upon airspeed squared. That is, at 80 knots, the drag is four times as effective as at 40 knots. Third, we only want to utilize Reverse when we are moving forward fast enough to leave the sucked-up dirt and debris behind us.
It is maddeningly common for me to observe a pilot who uses very little Beta or Reverse after touchdown but then, when he sees the turnoff coming into view, he at last starts pulling Reverse thrust. No, no, no! Now, not only is Reverse not very effective due to the slow airspeed, but also blade erosion is almost guaranteed if the surface is less than perfect!
Sure, if you are quite familiar with the airport layout and know that the turnoff is far ahead, the use of Beta only after touchdown – and maybe not even much of that – is just fine. But when the turnoff is a bit “unknown,”
20 • KING AIR MAGAZINE
JUNE 2017