Just Takes One for Magic!
Rotary aircraft like helicopters are a real photographic challenge! Unlike prop aircraft where the rotation is perpendicular to the film plane, rotary is not so blurring them requires a much, much slower shutter speed. As soon as one starts to lower the shutter speed, the sweat beads start to appear as fear of getting a sharp image sets in. Then when you combine that slower shutter speed with panning, well, you’ve seen those folks laying on the ground at airshows, why do you think they are there? You have to ask yourself this question, you want visual impact or an easy sharp image?
I have two photos here of the same Blackhawk. The bottom one was a slam dung easy tack sharp image at 1/250. Because of the flex of the rotors, even with it being broadside to the camera, you can see those rotors are sharp. Compare the visual impact to the other photo where the shutter speed was 1/25. With most prop aircraft, 1/25 would capture a full 360 disk but not with rotary! Personally, 1/25 is at my lower limit of getting sharp images while panning with keeper rate dropping to 40-50% or, 1 out of every 2 clicks is sharp. Many are really uncomfortable shooting in the basement like this but you can do it, especially if you practice. And while the keeper rate really drops, keep in mind that to be successful, it just takes one for the magic!