During the course of the year I will fly hundreds of hours in close proximity to Mikes Super Cub. Often I will be behind Mike, and I learned early-on to stay at or above his flight path. This is true when following any airplane, but all the more true when it is a fat winged, heavy, super cub with droop tips. You can see the wing tip vortices kicking up dust on the ground below Mike as he sets up for landing. For those of you unfamiliar with wing tip vortices, it’s the tornado that is created when the high pressure beneath the wing leaks around the tip of the wing and combines with the low air pressure above. The vortices are the worst when the aircraft is heavy, slow, and no flaps. The Vortices of larger aircraft are a real danger to small airplanes as the turbulence can cause a loss of control.
I do a fair bit of survey work which means I do a lot of low level circling. Here’s the scenario; It’s a cold winter morning with wonderful calm dense air. I am planning to fly for 7+ hours so I fill both wing tanks and top off my 32 gallon belly pod. Then I throw the survival gear in the back and cycle my wheel skis which weigh nearly 100 pounds. Then I fly over and pick up a 200 pound passenger and their gear. My Super Cub is now at it’s max gross weight of 2000 pounds. We fly out to start working and locate our first critter that we need to identify. As the animal passes beneath the jury strut I roll into a steep right turn so as not to loose sight of it and crank the airplane around in a perfectly coordinated turn. The cold calm air is awesome and I can feel the airplane carving through the air and it feels like I am on a rock-solid rail. I hold the turn for about 300 degrees of rotation, and it would feel so good to hold it and keep the animal in sight, but this is where I level my wings and swing back around for a figure eight. Or maybe just swing wide so as not to complete a perfect circle. I am avoiding my old flight path to stay out of the vortices. This is something that becomes a sixth sense with thousands upon thousands upon thousands of low level circles. Your own wing tip vortices are so strong in scenarios like this that they will make you crap your chaps if you get stuck in one. A whole bunch of Super Cub jocks with more time than me have spun into the ground and I believe it can happen to anyone. If you think I’m crazy then you have never experienced this. Sometimes you hit the vortices and they feel like a speed-bump, but other times, if you are maintaining the same flight path in a turn, the air is trying to flip you over on your back. The only way out is to #1 pitch forward and #2 apply full left rudder, because the ailerons are virtually useless. Its easy with a relatively light cub and 5 knots of wind, but when it’s calm and cold, and the cub is heavily loaded LOOK OUT!