Seeing Thermals

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proppastie

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While reading "H is for Hawk" by Helen Macdonald I came across this statement:
"This hawk can see colours I cannot, right into the ultraviolet spectrum. She can see polarised light, too, watch thermals of warm air rise, roil, and spill into clouds......."

Not disputing this assertion would it be possible to have a display that did the same and we could see warm air rising......Is this like the heat waves rising over a hot highway in the distance,...perhaps something more sensitive, on our panel?
 

Jay Kempf

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It is possible to build a thermal imaging camera tuned to the right wavelength. I am surprised that that hasn't been done and marketed. Of course it would be illegal in competition so it would only be for recreational use. Filtering the camera for distance so not as to get false readings while in an area of high temperature differential would take some work. Or it could just be used to see the next one at a distance (training in other words).

When I was younger I met a guy who could definitely see thermals. I think people with that range of eyesight are rare. We would fly RC gliders together and he could always see the lift. I tested this with this guy over and over again and it wasn't some trick. He could describe when my glider was going to hit the lift. I have really good eyes for distance but couldn't see what he was seeing.
 

mm4440

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https://newatlas.com/military/trijicon-ventus-handheld-wind-mapping/?utm_source=New+Atlas+Subscribers&utm_campaign=9241f962de-EMAIL_CAMPAIGN_2020_02_14_02_37&utm_medium=email&utm_term=0_65b67362bd-9241f962de-76688727
This could do it. Some years ago in Soaring magazine an Army Apache pilot described seeing "Gray Ghosts" in the FILAR during daytime. Thermals were visible in the monochrome display. The temperature differences in a thermal are quite small so a sensitive imager is needed. What wavelength IR imager is best?? The LIDAR based unit works on sensing returns from dust particles so can detect non thermal lift.
 

bmcj

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I believe that some of the airlines are installing a laser system that can detect wind sheer and clear air turbulence far enough in advance to either avoid or get the passengers back into their seatbelts. Perhaps a similar system could work for thermals.
 

azevedoflyer

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Many, many moons ago the British experimented with static voltage differences between a glider wingspan tips.
If I recall correctly, they could tell the side a thermal was at by an increased static voltage on that side, compared to the other tip.
Of course, no "at distance" prediction was possible. Still playing from memory, the signal could be very noisy and thus unreliable.
Lost contact with development of such technique.
 

ypsilon

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There are onboard systems on airliners that measure wind shear. Those are laser based but not classical lidar systems. They are basically laser-speckle interferometers and a whole load of software postprocessing, to get a halfway reasonable response. The problem here is, that the volume you measure is your screen at the same time. So the number of aerosols plays an important role. Air too clear -> not enough reflection. Air too polluted -> too little range. I used to be part of a dev team working on such a device, so I can say, that I don't think anybody can use anything like this for CATs at cruise level of modern airliners.

As for "seeing" thermals: Forget thermo-cams. Thermals aren't necessarily much warmer than the surrounding air, letalone air that isnot in it's immediate vicinity. Above 500m of release height, there are virtually no temperature differences.
Even if thermals were much warmer, then what would you see while circling in one? You wouldn't be able to see the next one anyway, exactly when you'd need to make the decision where to go next. What could work, is getting a heatmap of the ground, but that doesn't necessarily show where the thermals release.

So I don't think there is a reasonable system that would allow to see thermal updraft.
 

Jay Kempf

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Many, many moons ago the British experimented with static voltage differences between a glider wingspan tips.
If I recall correctly, they could tell the side a thermal was at by an increased static voltage on that side, compared to the other tip.
Of course, no "at distance" prediction was possible. Still playing from memory, the signal could be very noisy and thus unreliable.
Lost contact with development of such technique.
But that is intuitive and obvious when thermaling. No instruments necessary. That tip goes up it is closer to the lift. Turn into it. QED.
 

Pops

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But that is intuitive and obvious when thermaling. No instruments necessary. That tip goes up it is closer to the lift. Turn into it. QED.
Yes, turn into it. I designed and built a 9' RC sailplane and flew it for about 10 years on a hill behind my house . It had a .15 engine with a one once fuel tank. I would wait until I seen some hawks in a thermal and launch the sailplane, the engine would take it up to about a thousand feet and run out of fuel. Then I would get in the thermal with the hawks. They didn't pay any attention to it if the engine was not running and be wing tip to wing tip with them. I would stay with them until they started to drift downwind until I needed to make sure I could get back upwind to the field. Lots of flights for 2-3 hrs.
The hawks are the masters.
 

Aerowerx

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Yes, turn into it. I designed and built a 9' RC sailplane and flew it for about 10 years on a hill behind my house . It had a .15 engine with a one once fuel tank. I would wait until I seen some hawks in a thermal and launch the sailplane, the engine would take it up to about a thousand feet and run out of fuel. Then I would get in the thermal with the hawks. They didn't pay any attention to it if the engine was not running and be wing tip to wing tip with them. I would stay with them until they started to drift downwind until I needed to make sure I could get back upwind to the field. Lots of flights for 2-3 hrs.
The hawks are the masters.
Pops, you have Turkey Vultures over there?

I once saw one working a thermal, turning within its own wingspan. Would like to see a sailplane, RC or full scale, try that!
 

Elmog

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Sometimes the lift is so easy to find with an R/C sailplane that your neck gets tired looking up at it (after an hour). The best pilots are are the ones that fly discus (hand launch) sailplanes that can find thermals at very low altitudes. There are all kinds of clues at ground level if you know what to look for. You may not “see” the thermals, but you can see/feel the signs of the thermal passing by.
 

Aesquire

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There was an ionization detector marketed to hang gliders once upon a time. A simple, small, ( big pack of gum size ) circuit board with battery clip & computer micro speaker. ( The one on motherboards that beeps ) You'd mount one on each wing tip with velcro. You'd hear one side beep, hopefully before the thermal lifted a wing. Everyone I knew who tried it said it worked, sorta, but was annoying. ( this from guys who love a nice variometer squeel! ) A one season wonder.
 

azevedoflyer

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Many, many moons ago the British experimented with static voltage differences between a glider wingspan tips.
If I recall correctly, they could tell the side a thermal was at by an increased static voltage on that side, compared to the other tip.
Of course, no "at distance" prediction was possible. Still playing from memory, the signal could be very noisy and thus unreliable.
Lost contact with development of such technique.
But that is intuitive and obvious when thermaling. No instruments necessary. That tip goes up it is closer to the lift. Turn into it. QED.
[Agree!
Frank Irving, from Imperial College - London, was behind such experiment. He was a smart guy and for sure had some ulterior motivation.
 

Pops

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Pops, you have Turkey Vultures over there?

I once saw one working a thermal, turning within its own wingspan. Would like to see a sailplane, RC or full scale, try that!


Yes, lots of them. There is a ridge a good 400' high running close to and parallel to the runway. At the north end the ridge is in part of the final approach to 25. The hawks and turkey vultures ridge soar on the ridge and you had to watch out for them while in the pattern. IF it is a good crosswind from the NW, you also have to swing away from the lift of the ridge on final and come in on final at a 30 deg angle.
 
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