Thanks for posting this ERJF15. Certainly this is sad, and I feel for the families left behind.
I just found this. Wasnt sure if this was a thread derailment or not, mods do with as you please. Thoughts on the article???
How to Halt Dutch Roll |
Dutch roll—the combined yawing and rolling motion that all airplanes exhibit to some extent—is almost a thing of the past due to better aerodynamic designs, and more importantly, the almost universal use of yaw dampers. But Dutch roll can be serious, especially in swept wing airplanes flying in the thin air of high altitude.
We all remember from ground school that Dutch roll is caused by yawing motion which adds a little airspeed and thus a little more lift to the advancing wing. That bit of extra lift causes the airplane to roll as well as yaw. In an airplane with neutral Dutch roll damping the yawing and rolling will continue until some control input stops the motion. Some airplanes, particularly early swept wing jet designs, had very little natural Dutch roll damping, or even divergent Dutch roll so each yaw-roll combination would grow in amplitude. In at least a few instances Dutch roll demonstrations got out of hand and the severe stress of the yawing and rolling tossed an engine off the wing.
In more recently designed jets the Dutch roll damping is at least a little positive and most are controllable without the yaw damper functioning. However, passengers would rebel against any intentional flight without the yaw damper operating because nothing stirs the stomach quite as quickly as Dutch roll.
There is, however, an old trick to end Dutch roll, particularly in a jet, that I had never learned until recently. But it’s something military pilots who flew the early jets learned in training.
In test pilot speak Dutch roll is a second order phenomenon. They describe it mathematically, but bottom line is that the roll and yaw are linked. One causes the other. So, to halt Dutch roll you need to disrupt one motion, either yaw or roll.
Using the rudder to stop Dutch roll is obvious, and that’s what the automatic yaw dampers do. With their electronic sensors and brains the yaw damper can move the rudder almost instantly to counteract yaw.
However, we humans need time to recognize the yawing motion, calculate how much pressure to put on which rudder pedal, and then for our muscles to react. That’s usually too much time for us to make the proper rudder input to halt the yaw.
But the Gulfstream test pilots showed me, as part of a new advanced pilot training program they are developing, an old trick with the ailerons that halts Dutch roll almost immediately. What you do is move the wheel back and forth a few degrees as quick as you can. This small and rapid movement of the ailerons disrupts the rolling motion and uncouples it from yaw.
When I was told to “just move the wheel back and forth” I did, and it didn’t work. I was making the movements too slowly. You need to wiggle the wheel like a madman and then the Dutch roll stops like magic.
Who knew wheel wagging would stop Dutch roll. Turns out pilots who went through military jet training decades ago do.