Page 23 - Volumne 18 Number 5

Gust spread is not true windshear, but it has similar consequences; sudden increases or decreases in wind speed cause the roller- coaster effect we find on approach. If you watch autothrottles moving aggressively back and forth in these conditions, you’ll have an idea of what you need to be doing when hand-flying. The ancient rule is to carry half the gust spread in extra airspeed when landing on a windy day; a report of “15 gusting to 25” calls for tacking five more knots onto your normal Vref. Often, however, pilots make it 10 knots or more, with a corresponding increase in runway used during rollout. Just half the gust spread is enough.During departure, once you’ve climbed above the turbulent ground- influence layer that’s usually found within one or two thousand feet of the ground, the ride will smooth out until it’s time to land. As you descend for the landing, you’ll have to tighten your belts and prepareto fly aggressively. Don’t ignore a strong wind’s effect on any turns made during the landing approach. A turn to final with a stout tailwind tempts a pilot into steepening the turn’s bank angle as the runway enters the side window. Worse yet, he or she may unconsciously step on rudder to skid the airplane into alignment, an invitation to disaster at slow speed. Just let the turn’s ground track overshoot the centerline if necessary, then make a correcting turn in the reverse direction to regain the straight- in line-up.In mountainous terrain, beware of strong winds blowing perpendicular to the ridge lines. If the wind at ridge level (not surface wind) is 15 knots or more, there will be strong downdrafts on the lee side of the ridge, and wave action can persist a hundred miles downwind at altitudes far above the hills. It doesn’t take Alpine heights to create noticeable waves; even thousand-foot ridges above a valley floor will generate this dangerous turbulence if the conditions are right.Never forget that airport operations are conducted in a localized wind condition, and the generalized wind field can be altered by a number of factors, like buildings and terrain. Larger airports will have perimeter wind indicators that can give you clues of a shifting wind, and possible windshear warnings. Do not try to take off or land in close proximity to a thunderstorm. An outflow wind from the storm can turn everything around for your approach or climbout. Watch for blowing dust and tossing trees, and take them as a sign to fly elsewhere.Don’t ignore the wind as a component of the weather briefing. If you’re at the wrong airport at just the right time, you may find yourself exceeding the aircraft’s limitat•ions, if not your own. Have a plan to deal with the wind’s consequences. T&TMAY 2014TWIN & TURBINE • 21