Page 16 - Volume12 Number 5

since returned and been recertified in the United States, have the annunciators.
Since it seems the time required to blow enough oil out of the tank to be problematic usually elapses soon after takeoff, get in the habit of doing a very careful scan of engine instruments as part of your After Takeoff flow pattern and checklist. None of us can fly a King Air without spending time looking at ITT, Torque, and Propeller Speed (Np) gauges. However, the remaining ones – at the bottom of the vertical stack, or over on the right side in the early birds with a horizontal row of gauges – attract our attention rather rarely. So now is the time to force ourselves to carefully scan those remaining three: Oil Temperature and Pressure, Fuel Flow, and Compressor Speed (N1 or Ng).
What’s that I see? Dang, the left Oil Pressure is low! Is there any supporting indication? Could it be merely a faulty gauge? Oh, double-dang! There’s oil streaming out of the aft seam of the cowling!
Not all, but most, King Air emergency checklists direct us to reduce power significantly when the oil pressure drops out of the green arc, but not necessarily to shut the engine down until it hits the lower redline limit. Why is that?
It seems logical that if the engine were not receiving the lubrication that it should, we should not run it hard ... and perhaps that plays a role in the directive to reduce power. However, there is a more significant reason.
Remember that the torque instrument is actually an oil pressure gauge, reading the pressure in the torque chamber in the nose case of the engine, but displaying the pressure not in pounds per square inch (psi) but in the foot-pounds (ft-lbs) of twisting force on the propeller shaft that caused the psi value. (How that all works is a miracle of engineering, but it is a marvelous, mostly trouble-free, system.) When oil pressure drops too low, there comes a time when the torque meter becomes incapable of working correctly. Specifically, it will be limited in its ability to measure and display existing torque. For example, it may never read above 600 ft-lbs
no matter how much more torque exists! This is the main reason for reducing torque when you observe low oil pressure.
Sometimes an unexplained decrease in torque indication has been the first thing that caught the pilot’s attention and led him or her to then notice a low oil pressure reading.
Since any gauge or sensor is capable of providing a false reading, it is always a good idea to attempt to get some verification before responding to the situation. For example, if you are fortunate enough to be operating a model with the Low Oil Pressure annunciator, and it illuminates, check the gauge. Is it showing a low reading? If the answer is “Yes,” you should throttle back and return for landing, even securing the engine if/when the oil pressure hits the red line. On the other hand, if the gauge reads properly, you may have only a faulty annunciator. Now’s the time to check the cowling carefully. Nice and dry, no oil seeping out? If so, you are rather sure there is no true oil pressure anomaly.
2The next Gotcha is a badly bent Nose Wheel Steering Stop Block. I hope on your exterior preflight inspections that you are giving this item the attention it deserves. This is the metal tab with the three holes in it, located on the back side of the nose gear strut. Its purpose is to limit how far the nose wheel can turn when we make a tight turn while taxiing. Use of differential braking and/or differential power allows the pilot to turn the airplane “on a dime,” and when this is done the stop block is what is preventing any damage to the nose strut and steering linkage. It is strong enough that the pilot cannot force any further movement.
However, the leverage created by a sturdy tug and a long tow bar can easily overcome the resistance of the stop and permit a careless tug operator to go beyond the limits. When this takes place, not only will the stop block be deformed, but there is a chance that the strut itself will be fractured and/or that the nose wheel steering connection back to the rudder pedals
will suffer damage. So, if ever you find the block distorted, I would suggest not flying until an A & P has inspected the strut and steering linkage carefully and given you a thumbs up that you’re good to go.
While you are down by the nose gear checking the stop block, occasionally also look up on the left sidewall of the wheel well and locate the shock link, the spring- in-tube assembly that is in the forward part of the nose wheel steering mechanism. Make sure that you can see and/or feel all four
14 • KING AIR MAGAZINE
MAY 2018