Gear Up

This is the “H2” variant of the Lockheed C-130H Hercules tactical airlift aircraft rising above the runway at Rosecrans Memorial Airport during the Speed of Sound Airshow in September of 2024. This is one of many aircraft of the 139th Airlift Wing (139 AW) of the Missouri Air National Guard at Rosecrans.

There is a phenomenon displayed in this image that I don’t believe I’ve photographed before. Notice the white spiral lines behind the propellers. They are tip vortices formed by the propeller. I found this description of what causes these lines on the web: “The pressure in the core of a vortex (such as that shed at the tip of an operating propeller, rotor, wing or extended flap) is reduced well below ambient pressure. The temperature is also lower than ambient because of the lowered pressure. If the temperature is lowered to the dew point, the water vapor will condense and become visible revealing the vortex core.” 

I have seen the tip vortices trailing a jet’s wing tips, but I don’t recall seeing them from the propeller blade tips. I’ve learned it’s a fairly common occurrence. I didn’t notice them the day I was taking this photo, so I was surprised to see it when I viewed the photo on my computer screen.

By the way, I should have been using a slower shutter speed when capturing this image. A slower shutter speed would have given the propellers a bit of a blur, indicating movement. When the movement is frozen, as in this image, it seems odd to our brains and belies the incredible speed in which they rotate. I needed the faster shutter speed to better capture jets at this airshow, but should have had the presence of mind so reduce the shutter speed when shooting aircraft with propellers. (I guess I’ll have to keep my amateur status.)

You can get a better view of this image and the and the vortices by clicking on the photo to view a larger, more detailed version.

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