Is There Anything To Learn?

I believe the answer is clearly “yes”.  The following summarizes my personal takeaways.  You may need to adjust these based on your flying environment, your experience and skills, and your glider.

Recognize the Potential for Microbursts

First, there are a few facts about microbursts that I will try to remember:

1. Microbursts are a common summer-day phenomenon. In the Western US, they occur on practically any good summer soaring day.
2. Microbursts do not just develop below towering cumulonimbus cells.  They can occur under any mature cumulus cloud that is starting to dissolve, especially if there are signs of precipitation below cloud base.
3. Dry microbursts are invisible.  The only visible indicator may be a ring of dust on the ground emanating from the center of a downburst.  However, dust can obviously only be noticed after the microburst has already reached the ground. You may not be able to see it in time!
4. Virga is an indicator that microbursts may be present because virga is a tell-tale sign of evaporative cooling, which accelerates any downward movement of the air.
5. Microbursts can be extremely powerful and the sink alone can be overwhelming.
6. Near the surface, strong sink from a microburst is typically followed by a sudden and powerful tailwind, no matter in which direction we’re heading.  This is a consequence of the fact that the down-streaming air is deflected outwards in all directions as it hits the ground.
7. The greatest risk of sudden tailwinds exists below 1000 ft with a peak wind differential at around 200 ft AGL.  That’s why microbursts are so dangerous in the landing pattern.
8. In addition, I will remember that AWOS reports are outdated.  Microbursts occur suddenly and the reported wind speed necessarily reflects what happened in the past, not what is currently happening. There can also be a substantial time delay in the reporting.

Anticipate and Avoid

Second, the best strategy to minimize the risk of getting caught in a microburst at a low altitude is to anticipate and avoid it.  Practical strategies I will use going forward are:

1. If there is any indication of overdevelopment or virga I will adjust my final glide approach such that I plan to arrive at the target airport with a minimum altitude of at least 3000 ft AGL. This will give me more time to assess the conditions and make alternative plans.
2. If virga is present above or immediately next to my landing site I will attempt to delay my landing by staying in rising air at a safe distance and altitude and wait for the virga to move away or dissipate completely.  This usually only takes a few minutes.
3. If this is not possible I will divert to a different airfield or landing site provided that the conditions look more favorable.

Modified Landing Pattern if Necessary

Third, as a last resort, if I must land despite the presence of virga above or next to the field I will modify my landing pattern as follows:

1. I will enter the landing pattern much higher than usual.  This may be as high as 3000 ft AGL to allow for the possibility of massive sink on the downwind leg.  (I will also announce this unusual pattern on the radio so other traffic is not taken by surprise.)
2. I will plan to maintain a substantial altitude safety margin throughout the pattern and complete my final turn while still at an altitude of approx. 1000 ft AGL, planning to fly a very steep final approach.  Completing the final turn around 1000ft will significantly reduce the risk of a sudden gust from behind, especially while turning.
3. I will fly at a much higher pattern airspeed. This is especially important once I get below 1000 ft because that is where a gust from behind is most likely and also most dangerous.  If there is any virga in the vicinity I will fly at a minimum IAS of 80 kts (20kts above the yellow triangle speed).  If I encounter sink in the pattern I will immediately increase my airspeed further.  As a rule of thumb I will add extra airspeed equivalent to my sink rate.  E.g., if my sink rate is 10 kts (1000 fpm), I will add another 10 kts and fly at 90 kts IAS.  If my sink rate is 20 kts, I will fly at 100 kts IAS.  The stronger the downdraft, the stronger the potential tailwind once I get close to the ground.  I think this airspeed adjustment will better protect me against sudden tail gusts or descending into a sudden tail wind.

Communication and Training

I realize that flying such an unusual pattern can in itself be a risk.  There are two concerns in particular:

1. Other traffic may not anticipate it and be taken by surprise.
2. I could misjudge my altitude and overshoot the runway.

With respect to the first concern, I will mitigate it by clearly announcing my intentions.  I would also hope that such a pattern is rarely necessary because I intend to avoid to land in such conditions whenever possible. This pattern is the last resort.

With respect to the second concern, it is something that I will deliberately practice when there is no other traffic in the vicinity.  It is clearly helpful to get accustomed to the sight picture of finishing the turn to final at 1000 ft AGL and making a spot landing at the normal aim point.  I am fortunate that my glider has very powerful airbrakes, which allow for a very steep descent if necessary.  This approach may not work for gliders with less effective spoilers.

Final Thoughts

Writing this article has been difficult.  However, I sincerely hope that it was worth it. Unfortunately, it won’t help Shmulik.  But I know that it will help me and hope that you, too, find it valuable.  I am not a fatalist and I like to avoid leaving things to chance. I know that our sport is objectively dangerous.  But I also know that if we are willing to do the hard work that it takes to learn from the accidents of others it does not have to remain quite as dangerous. I hope this analysis is another step in that direction.

Disclaimer: this analysis is not intended to preempt or substitute the official NTSB accident investigation.  It is solely based on information that I had ready access to.  More information may come to light (e.g. by analyzing the more detailed igc trace rather than the ADSB trace).  My analysis also includes interpretations that are necessarily subjective.

 Clemens Ceipek first started to fly gliders in 1983, just after his 16th birthday. For a few years, Clemens flew fairly regularly and added certificates for winch launching and self-launch to the initial aero-tow license. Then came university, family, and a global business career. In 2017, Clemens finally decided to return to the sport that he once loved. His blog, SOARING - CHESS IN THE AIR, chronicles a second journey to become a better soaring pilot. It is, first and foremost, written for himself: to document what he learns, the mistakes, and the sense of wonder that is experienced. The blog can also serve to inspire other glider pilots and those who consider joining this wonderful, and incredibly challenging sport...