The Invisible Threat of Wind Turbines
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| Field of wind turbines. Photo by Waldemar Brandt on Unsplash |
West Texas has huge swaths of land covered with ever-larger wind turbines.
These turbines are a significant threat to aviation, as has been established in several studies of turbulence and visibility. The threat will grow as turbines become ever larger. The latest development is a turbine by General Electric with a 850 ft (260 m) tall tower and 350 ft (107 m) long blades that will likely show up in Texas some time in the future.
There are two problems for pilots: The blades are difficult to see from the air, and they produce significant turbulence downstream.
While the turbulence of single turbines has been studied in detail, little is known about the effect of an entire field of turbines. Here is a demonstration that fields of turbines can create powerful turbulence.
Below is a screen shot of a Garmin Pilot map taken on May 29, 2021 when we were planning a flight from Dallas to Albuquerque, NM. It shows a field of turbines south of the Hale County airport in the Texas Panhandle.
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| Clouds and precipitation indicated over field of wind turbines |
The green overlay seemingly indicates that the turbulence produced by the field creates clouds and some precipitation. A tall tower reaching 4,280 ft MSL is embedded in the field and poses an additional hazard.
Note the small field of turbines partially shown in the lower right corner of the picture. It has much reduced green shading, showing that larger fields produce greater turbulence.
A Different Explanation
Five days later we flew the route Dallas-Albuquerque and didn't see any such green shading. But when we returned to Dallas on June 6, the Garmin Pilot indicated severe thunderstorm weather over the same field.
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| A thunderstorm? |
When we approached the Hale County Airport, to our surprise there was nothing to see over the field: Not a single cloud except for wisps way above.
The folks at the Hale County airport explained: Yes, they had seen this before. It always happened when they had strong surface winds.
The intuitive explanation is that weather radar is fooled by the horizontal tornadoes produced by the wind turbines. Indeed, Hale County on that day had strong surface winds of 16 kts, with gusts up to 20 kts.
A long technical paper explains the effect of wind turbines on telecommunication, in particular on weather radar. It includes example images where radar is fooled into detection of precipitation. But the paper does not discuss the horizontal tornadoes produced by the wind turbines and their threat for aviation.
Here is another example where wind turbines produce fake weather.
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| Fake weather |
The Message
Given today's limited knowledge about the hazards of wind turbines, the following seems prudent:
1. Treat each field as if it were an area of open water. That is, your altitude must be sufficient so that in case of an engine failure you can glide to a site outside the field while staying at least 500 ft above the tallest point of the wind turbines. In the example case, the tallest structure in the field is 1,000 ft AGL, so you must stay at least 1,500 ft AGL above the field while gliding to the selected site.
2. In case of an engine failure, look for potential landing sites in the two directions perpendicular to the prevailing winds. That is, if the wind is from the north, go for a site to the east or west. The two escape directions are easy to determine: The blades of the wind turbines point them out since they rotate at right angle with the wind direction.
3. Points #1 and 2 once more prove that Sullenberger's rule for en route navigation is important. Remember, in the "Miracle of the Hudson" he made an emergency landing of an Airbus jet on the Hudson River that everybody survived. Here is his rule: Every 30 minutes, look ahead along the remaining route and examine the weather for each airport.
We have added to Sullenberger's rule a complete scan of the panel that covers all items: autopilot, instruments, radios, switches. This scan is in addition to the usual en route scans.
The rule has served us well, and will do so if we ever have to plan an emergency landing while over a field of wind turbines: We will have already thought about the two possible escape directions and be at an appropriate altitude, and can immediately start a safe glide away from the field and its turbulence.
Have any questions or feedback? Please share your thoughts in the comments.
Here is a device that most of us imagined would provide clean energy from the wind with little effect to anything else. Yet it turns out this was not the case. Thank you for sharing valuable information when it comes to the safety of aviation. Good to know.
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