Page 25 - TNTMay18

away from the safety of the lower terrain and warmer temperatures below. If we had been fighting ice all the way up, and were unable to get or stay on top, even though in a de-iced and turbocharged and pressurized airplane, the best thing for an experienced, mature and professional pilot to do is call it a day and simply not go further east. When operating in the Pacific Northwest there is a rule in this regard that is helpful to remember: “With winds from the west, do not proceed eastbound until certain there will be no need to return.”
Finally, after managing to cross the Cascades and approaching BOI, we need to do some ice-related descent planning. Given the 28-degree temperature at the surface, some ice should be expected during the descent, and if that ice was bad enough, it could force the airplane all the way to the ground even with the FIKI system running full blast. For this reason, I would not want to start my descent from “on top,” until relatively close to BOI and would so notify the controller.
Before starting the descent, I would make sure the cabin pressure rate controller was set to no more than 500 feet per minute and would plan on a good 1,000 foot per minute aircraft descent all the way to the final approach point, keeping the TAS up at high cruise and the engines warm by carrying power.
One of the reasons for the high airspeed is that air moving across the wing is warmed a bit from higher speeds. Sometimes just a 20-knot change in TAS will stop ice from forming in conditions that are otherwise identical. The lower angle of attack will also help prevent ice from forming on the bottom of the wing where you can’t see it. Another reason for the high descent rate is it means the airplane will pass through whatever icing layers exist much more quickly. Basically, if we encounter cloud tops on the way down at the forecast 8,000 feet, and the altitude at the IAF (initial approach fix) is say 4,000, we would spend no more than a total of 3 or 4 minutes in the potential ice.
Now all we have to deal with is the final approach and landing. In spite of our careful “ice avoidance” descent, it is possible that with the 28-degree temperature on the ground at BOI, whatever ice accumulated on the aircraft could still be present upon landing. Making sure windshield de- ice is working is important in these conditions. Even in a FIKI airplane with
boots and hot props all working, ice tends to stick to the wing in areas you cannot see, raising the stall speed by an unknown amount. For this reason, keep the airspeed higher than normal until close to the runway. In these conditions, a pilot with a professional mindset would only flight plan into airports with long runways (BOI has 10,000 feet).
Additionally, some inquiry as to braking conditions is in order before landing. If we had departed a wet runway at BFI and then climbed into freezing conditions, it’s also possible the brakes could be frozen and will not work initially after landing. Some turbine aircraft such as King Airs have a special hot air hose to the brakes for this very reason, plus the ability to reverse either the propellers or the engine thrust, piston twins do not, so you have to be extra careful.
After landing and getting clear of the runway, our problems are not yet over. In the winter there can be piles of snow that can be a problem for low wing twin-engine aircraft with their propeller blades sweeping less than a foot above the ground. So even if we know exactly where to go, if there is any question about the best route to take the best procedure is to just ask for progressive taxi instructions.
When finally arriving at the FBO and taxiing toward that lineman with the orange wands, keep your right hand on the mixture controls. You never know if a patch of ice will •magically appear under your main gear just as he waves you to a stop.
After all we have been through on this trip, scaring the line guy would be a bad way to end the day. T&T
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Kevin Ware is an ATP who also holds CFI, MEII and heli- copter ratings, has more than 10,000 hours and is typed in several different business jets. He
has been flying for a living on and off since he was 20, and currently works as a contract pilot for various corporations in the Seattle area. When not working as a pilot he is employed part time as an emergency and urgent care physician. He can be reached at kevin.ware2@aol.com.
May 2018
TWIN & TURBINE • 23