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Identifying Thermals/Ridge Lift and other at a distance

#1
I'm new to the forums, and this might be better suited to fixed wing electric, but I hear glider pilots talking about this topic more often.

Does anyone here have any knowledge of identifying thermals during flight? I'm familiar with programming and adding custom electronics hardware like thermal reading/imaging devices to projects, but I can't find any info online other than "Find birds gliding." I haven't made my way through the academic journals yet, though, so there may be something there I'm missing. I also see that variometers and some ground based techniques can be used to detect when currently in a lift area, but I'm looking for distance sensing.

The project goals:
  • Adding a lightweight general processing computer to the aircraft
  • Reading data in from GPS and other electronics for telemetry and decision making
  • Using a variety of sensors to detect thermals (IR or other... are there small RADAR modules?)
  • Possibly reading full size aircraft weather maps to model on the flight computer where lift might be if there is no sensor method
  • Possibly using ground-based systems to communicate up to the aircraft if equipment gets too bulky (I still want distance detection though)

I tried searching the forums here and found some neat info covering what may produce thermals and how to spot certain kinds, but not a resource for general thermal/lift seeking. ( https://forum.flitetest.com/index.php?threads/what-did-you-fly-today.57878/page-7#post-486853 )

I guess I could make a computer that follows birds :ROFLMAO:
 

Merv

Well-known member
#2
Does anyone here have any knowledge of identifying thermals during flight?.....I can't find any info online other than "Find birds gliding."
I am far from an expert when it comes to finding thermals. The sort answer is no.

Most of the gliders are in areas with hills or ridges. They call it slope soring for a reason. It's possible to locate places where the wind is forced up by the shape of the ground. Under the right conditions, you can reliably find lift in these areas.

Where I live, it's flat. Finding true thermals is difficult. There is no weather data that is going to help. You need to look for the proper conditions, sunny with a slight wind, 3-5 mph. If you notice the wind has stopped for a moment, you are standing in a thermal. As the wind picks up, the thermal is moving away. The only device that is of any value is the variometer, it will tell you when you happen upon a thermal and are being lifted. When you find a thermal the trick is to stay in it, they don't stay in one place, they move. Some thermals are big other are small, some have a lot of lift, others not so much. As far as finding the next one, no there is nothing to locate an new thermal. You glide around until you find lift.

Birds are much better at thermals then we are. Some speculate that birds can see or somehow sense thermals. If there are several birds in a big thermal, go for it, you can have a lot of fun. If it's just one bird gliding along, forget it. You will never be able to find it by following the birds. You are much better off hunting for your own thermal.
 

Piotrsko

Well-known member
#3
Thermals are repetive from a constant source. Look for something different, darker colored than the surroundings. Blacktop tennis court in a grass field, roads, dark roofs, burning trash, dust devils, leafs swirling, what have you. My flying field has a school with a monster A/C unit and a cooling tower. Thermals are temperature differential started where you get a bubble or column of warm air that unattaches and floats skyward. More differential, more often and more powerful uplift. Been my experiences that they are better above 50ft AGL, HOWEVER, I have caught them at 10 ft. How to detect: craft wobbles, or tail comes up slightly, warmer air for a moment, breeze when everything else is still, birds. NOAA has a convection predictor on their weather sites. Most places have them, most people can't recognize the telltales. If you have a cooler morning , sunny day and a puffy cloud or two, you got thermals.
 
#4
I am far from an expert when it comes to finding thermals. The sort answer is no.

Most of the gliders are in areas with hills or ridges. They call it slope soring for a reason. ...

Thank you for the thorough response. I guess I'll just have to have an alert for lift.

Do you happen to know how wide thermals are on average? I might be able to make a program for a single-click "Edge finder" for the thermal to stay in it.

And of course I find this project below just clicking through an unrelated video link... Not exactly what I was hoping, but might be the next best thing! https://ardupilot.org/plane/docs/soaring.html

I'll have to read through it to see exactly how it works. I'm reading the paper of its results currently.
 

sprzout

Knower of useless information
Mentor
#6
Here's a video that I found that actually helped me identify WHERE thermals would hide out, and some key factors to find them. We've constantly got them around my flying field due to the asphalt runway, piles of clipped grass that are decomposing (because those piles of grass generate heat!), and the parking area reflecting heat back up.

Here's the video - this guy did a pretty good job of explaining it, even though he takes 20 minutes to describe it.

 

sprzout

Knower of useless information
Mentor
#8
That's neat. I'm still making my way through the video (I work remote, so I have time :D)

I didn't know those extra details about thermals like the cone shape and spin.
Exactly how I felt. :) And one of the tips about having the wind at your back when looking for thermals - kinda goes against what I'd thought when flying slope, where you want to have it in your face!

It's a LOT of information, but it does give off some good points, and it's very helpful. :)
 

Merv

Well-known member
#9
Do you happen to know how wide thermals are on average?
No, nothing average about them. Some are huge, 1,000 feet wide or more, some are small, 50 feet. Some are round, some are more rectangular, more like a wave of air moving across the surface. Round thermals tend to be in lighter winds and get wider as you go higher. The rectangular, waves of air, tend to be in stronger winds. You ride them on an angle, like a surfer.

@Piotrsko makes a good point, sometimes you can find lift from the heat coming off roads, parking lots, roofs, ect. Sometimes you can find lift at the edge of a timber. This kind of lift tends to not be very high, 100-300 feet. True thermals can go very high 1,500 feet or more.

My Versa normally flies for 6 minutes or so, with thermals I've had 30 minute flights.
 
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sprzout

Knower of useless information
Mentor
#10
No, nothing average about them. Some are huge, 1,000 feet wide or more, some are small, 50 feet. Some are round, some are more rectangular, more like a wave of air moving across the surface. Round thermals tend to be in lighter winds and get wider as you go higher. The rectangular, waves of air, tend to be in stronger winds. You ride them on an angle, like a surfer.

@Piotrsko makes a good point, sometimes you can find lift from the heat coming off roads, parking lots, roofs, ect. Sometimes you can find lift at the edge of a timber. This kind of lift tends to not be very high, 100-300 feet. True thermals can go very high 1,500 feet or more.

My Versa normally flies for 6 minutes or so, with thermals I've had 30 minute flights.
LOL yup - to your point, if you've ever seen a dust devil, well, that's a small thermal that's just picked up some particulate and made it visible. Tornadoes are technically thermals, just on a large and violent scale...