Page 26 - Volume 10 Number 8

Ask the Expert
TAWS Procedures
by Tom Clements
For a few years now, all King Airs with six or more installed passenger seats are required to have a Terrain Awareness and Warning System (TAWS) onboard and operational. This is a stand-alone system in some installations and is integrated into the GPS navigator in other installations. I have a homework assignment for you: Go to the Supplements section of your King Air’s POH and find, then read, the supplement dealing with your exact system. After doing this, I bet you will discover a few things you did not know or had forgotten. There’s good info there!
If TAWS is a part of your latest, greatest, factory- installed Pro Line or Fusion system, its description can be found in the Systems section of the POH, not in the Supplements section.
Thanks to space shuttle flights, the entire earth has been mapped in great detail and that detail can now be included on a tiny chip in your TAWS unit. Amazing! GPWS – Ground Proximity Warning System – a system that preceded TAWS, was primarily based on radar altimeter readings so it knew your height above the ground right beneath you and it could calculate your rate of closure to terra firma. But it had no look-ahead capability – it couldn’t see that cliff looming up ahead – and it also lacked an airport database. But by combining a chip with knowledge of all terrain and airports with an exceedingly accurate GPS navigator that knows the airplane’s exact position both horizontally and vertically, as well as the track and speed of the airplane, it is now possible to look well ahead and to accurately predict whether the existing flight path is safe or not safe. EGPWS – Enhanced GPWS – is the name Honeywell assigned to their version of this advanced system. The FAA and other manufacturers use the moniker TAWS.
There would be absolutely no reason for a TAWS system if pilots never made mistakes! It’s only when scud-running suddenly turns into solid IMC, or when a pilot misreads a chart and descends too soon, or when a pilot fails to follow the assigned flight path that TAWS is a necessary life-saver. Let’s face it, we are human and humans can and do make mistakes. CFIT – Controlled Flight Into Terrain – has been a consistent leader of reasons for aviation-related fatalities and TAWS is a Godsend that helps reduce the likelihood of this cause of death. Will it ever completely eliminate CFIT? I doubt it because mistakes will still be made, but it surely improves the odds of survival by a huge amount.
24 • KING AIR MAGAZINE
How about giving yourself a little educational fun? On your next deadhead leg in excellent visual conditions, head directly for a convenient mountain. Oh, you don’t have one of those in Kansas, you say? In that case, just casually descend toward a wide open wheat field with no farmer nearby. I want you to actually experience both a TAWS Caution and a TAWS Warning in your exact airplane. This will always include verbal calls and in most installations it will include a visual presentation of the dangerous terrain. The caution you will hear probably is this: “Caution, Terrain! Caution, Terrain!” If we ignore that and continue toward the danger, then we should hear a warning: “Terrain ahead! Pull Up! Terrain ahead! Pull Up!” Now remember, we are doing this in good weather with plenty of visibility and we have an easy escape route, right? Right!
Descending toward the Kansas wheat field, the Caution we hear may be “Too Low! Terrain!” Continuing our descent will then lead to the “Terrain ahead! Pull Up!” warning as before.
Your system’s instructions will tell you that using the visual display to steer toward lower ground is not the correct procedure. Sometime you may have a system without a visual display or else it is malfunctioning. So the proper procedure is to climb like a homesick angel! Now is the time to use your four friends – Power, Props, Flaps, Gear – and get the heck away from the terrain. In the majority of the cases, your airspeed will likely be quite high ... cruising or descending. Also, your prop levers will probably be set for cruise RPM and your flaps and gear will be retracted. But not always. So always do all four steps: Power levers aggressively forward to torque or temp limits. Prop levers smoothly forward to the stops for maximum propeller speed. Flaps: Make sure they’re up. Gear? Same thing.
And as you are doing these steps be honking back on the control wheel to get the airplane into an optimum climb profile. Now is not the time to bring the nose up to 12 or 15 degrees and to wait for Vx to be achieved. No! Pull that sucker up to 25 degrees! Only when you see the airspeed approaching 120 KIAS should you drop the nose to maintain that speed ... probably the 12 to 15 degrees I mentioned before.
Now if you are exceptionally sharp and know the exact Vx number that is correct for your airplane, your weight, and your existing altitude, wonderful! Go for that number! But, dear readers, if you target 120 KIAS
AUGUST 2016