Wednesday, July 23, 2014

What Can I Learn About Thermal Soaring from the Turkey Vulture

I have noticed that the turkey vulture which appear to be increasingly common in the Mississippi river valley city I live in are easily able to soar in thermal lift which late into the evening when it has been normally thought this lift is very weak. My thought is that with much observation and some research I might be able to improve my model soaring skills by learning from the turkey vulture. Comparing the aerodynamic specifications between the model gliders that I fly and other soaring birds would be where I would start.

Turkey Vulture in Flight

Turkey Vulture Soaring Over Water Which Normally Creates Little Thermal Lift 

The wingspan of turkey is close to 6 feet supporting a weight of around 4 pounds. Their wing is rather wide giving it a lot of wing area but it doesn’t create as much drag as a wing normally would because of the slots in the wing tips created by the feather arrangement. The Turkey vulture is more efficient at thermal soaring than the black vulture which might explain why black vultures are found in southern regions of US where thermal lift might be greater from warmer ground heating.

Notice Wing Tip Feathers

In an article on soaring on Stanford website it said that it had been determined that the minimum sink of the turkey vulture was only 2 feet per second. I then researched what minimum sink might be for a 2 meter radio control glider which is slightly longer in wingspan but would have a narrower chord. Weight varies for 2 meter gliders like does the weight of turkey vultures but I think half the weight of the turkey vulture would be common.  One person had determined that their electric 2-meter glider had a minimum sink of 3.2 feet per second but larger radio control gliders might only be 1 foot per second.  Small lightweight free flight gliders might have a minimum sink of only ½ feet per second.

Sport 2-meter Radio Control Glider

More Efficient RC Glider on Launch

It would appear to me that although the physical characteristics of the turkey vulture in regards to aerodynamics are good but many radio control sailplanes would be superior. The bird however has the ability to change its’ wings in many more ways than the variable camber changing available on the more sophisticated model sailplanes.      

Sometimes Many Turkey Vultures can be Seen Circling in a Thermal

The real question would appear to be how are soaring birds such as the turkey vulture are so good at finding the lift; on this there seems to be many opinions but not much that is a proven fact. It seems very likely the bird could feel when it was going up or down but people think the birds have senses that go beyond this such as detecting thermals with low frequency sound or smells from the ground.

Flying Lower

Flying Even Lower in Downtown

 Like model pilots, soaring birds seem very aware of other birds or even model planes going up in lift and will quickly fly over to join in flying in a spotted thermal. 

Some of My Thoughts from Watching Turkey Vultures Flying

* There would appear to be stronger thermal lift in the evening than many model flyers might realize. 

* Turkey Vultures are soaring in really overcast conditions which again might not appear to be good for thermal flying.

* I need to spend more time observing their flight patterns in thermals, sometimes they appear to change directions, is there a good reason for that? 

Update 7/28/2014

Cold front had moved in a Sunday with high winds but winds were lighter on Monday so I flew my Radian Pro after work. I just couldn't seem to find any lift to speak of except the two times I spotted turkey vultures over the field. Then the Radian was going up rather slowly but not coming down, the birds weren't climbing much either. We were all flying in the same area and height the second time, so much fun.

Please share your thoughts on turkey vultures or other soaring birds.

Bill Kuhl

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