PILOT TECHNIQUE

Smart flying can outwit microbursts

How scenario replays and science have teamed to tame these intense events.


Training

WSR88D radar at ICT (which is closer to EWK than the TDWR) does not show the downburst wind flow. TDWRs are superior at sensing winds than the WSR88Ds.

While corporate jets have less of the microburst-related “momentum” problem and are more likely to be able to escape a windshear encounter, there are microbursts so intense no aircraft can escape.

So, while simulator training can indicate the best method of escape, avoidance is the only truly safe course.

Visual avoidance

While TDWR and WSR88D radar cover most major US airports, there are numerous airports used by corporate pilots that are still not covered by these systems, especially in western states where dry micro­bursts are most common.

A “wet” microburst appears as an opaque rain shaft with a well defined edge both at cloud base and between the rain shaft and the surrounding atmosphere. Stronger microbursts develop a curl after striking the ground. While a dry microburst is not as visually obvious, any time blowing dust is seen emanating from a central point, a microburst should be suspected, especially if there are curling patterns.

Warnings

TDWRs were designed specifically to detect windshear-related threats and are installed at 44 US airports. They are equipped with algorithms developed by MIT’s Lincoln Labs to detect dangerous windshear conditions and sound an alarm in the control tower which is then relayed to pilots.

Effectiveness

First image from 2010Z using NWS’s WSR88D radar shows the purple echo associated with the microburst over Terminal D and nearby taxiways (ringed here for clarity). The official DFW observation (east side of the airport) had winds gusting to 38 kts and shifting to 280° at 2018Z.

How effective is this 3-pronged approach to microbursts? The research I conducted for my book Warnings: The True Story of How Science Tamed the Weather led me to estimate the windshear warning system has prevented more than a dozen airline crashes since Delta 191 in 1985, along with an unknown number of accidents involving corporate aircraft.

However, one of the difficult aspects of assessing the effectiveness of air safety and disaster mitigation systems is measuring a negative—deaths that do not occur. While the above estimate is simply an extrapolation based on the frequency of low-level windshear accidents up to and including Delta 191 (and including USAir 1016), I have identified one destructive microburst that was a recent candidate to cause a catastrophic crash.

If you were watching the Kentucky Derby on May 2, 2009, you saw NBC News break into its Derby coverage with the story of the Dallas Cowboys’ training facility being collapsed by high winds, with injuries on the scene. An investigation revealed that a microburst was responsible for the high winds that caused the collapse of the tentlike structure. But a few minutes before the collapse, the same microburst was over DFW. DFW Metar at 1959Z gave winds from 200° at 8 kts.

Light drizzle is reported as the thunderstorm containing the developing microburst is southeast of the airport moving northeast. The microburst warning system worked at DFW on May 2, 2009—no airplanes crashed in spite of a dangerous microburst passing right across the airport.

Twenty years ago, this would have been a near-certain accident or incident. So, 25 years after Delta 191, the aviation and meteorology communities have made tremendous progress at taming the deadly microburst.

Mike Smith is CEO of WeatherData Services, an AccuWeather company. A fellow of the American Meteorological Society, Smith is board certified as a consulting meteorologist.

 

 

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