The windshear saga in American aviation history reveals a complex and costly past. Windshear has existed for as long as aviators have taken to the skies and is largely responsible for several classic aviation losses. Notable U.S. aviation accidents include Eastern Flight 66 (1975), Pan American Flight 759 (1982), and Delta Flight 191 (1985).

Windshear remained unrecognized for years. It was not clearly understood until swept wing, jet aircraft encountered the phenomenon. Since 1975, windshear has been researched and studied, measured, defined, catalogued, and rightly vilified. Technology has been developed to identify and minimize the threats that it poses. Procedures have been implemented to aid pilots who experience windshear in flight and flight crews invest hours of simulator training practicing windshear escape maneuvers.

Even with progress to date, windshear continues to be a worthy adversary to aviation professionals. It requires respect and wisdom to defeat. Pilots often must make decisions regarding known or anticipated windshear, and the best practice is always avoidance.

This month, CALLBACK shares reported incidents that reveal some means and extremes of windshear experienced in modern aviation. Lessons to be gleaned are ripe, rich, and many.

Teasing a Toronto Tailwind

After encountering windshear that resulted in an unstabilized approach, this A319 Captain elected to continue to a landing. He noted his awareness of the current winds and trends as well as his personal preparedness to go around as reasons for continuing the approach.

• After being delayed due to low ceilings in Toronto, we were finally descending…in heavy rain and moderate turbulence with clearance to 7,000 feet MSL. After a third 360 degree turn, we were…transferred to the Final Controller and proceeded inbound for the ILS RWY 05. The last several ATIS [reports] showed winds at approximately 090 to 100 [degrees] at 5 to 10 knots, and the Final Controller mentioned the same with an RVR of 6,000 plus feet for Runway 05. When cleared for the approach, we were at 3,000 feet MSL to intercept the glideslope, and I noticed the winds had picked up to a 50 knot direct tailwind. The First Officer was flying. We were assigned 160 knots and began to configure at approximately 2,000 feet AGL. At 1,500 feet the wind was a 30 knot direct tailwind and we had flaps 3. Indicated airspeed (IAS) had increased at this point [with] thrust at idle to 170-175 knots, prohibiting final flaps just yet. The First Officer did a great job aggressively trying to slow the aircraft, as we were concerned about getting a flaps 3 overspeed. As I knew from the ATIS and the Controllers (Tower now), the winds were to die off very soon to less than 10 knots. [Below] 1,000 feet we were just getting the airspeed to put in final flaps (full) and were finally stabilized and on speed between 500 to 800 feet. The winds were now at the reported 090 [degrees] at 8 knots or so [below] 500 feet. The total wind shift was approximately 90 degrees from direct tailwind to a right crosswind - losing 40 knots [of tailwind] in the space of 1,500 feet or so. The reasons I elected to continue the approach were:

1. We landed uneventfully in the touchdown zone and on speed…after breaking out before minimums.