Can I steer out of trailer sway?
Can you steer out of trailer sway?
The F-16 Fighting Falcon is an efficient, agile aeroplane. It is also impossible for a human to fly without the aid of a computer
Aeroplanes are generally designed to be stable. In aerodynamic terms that means the centre of gravity is a little ahead of the centre of pressure, which is the same as the CoG but for lift. The tailplane produces a corresponding downforce. This is a stable setup and exactly why is getting beyond the scope of this post, but the important point is the stability…and the corresponding downforce from the tailplane means the aircraft is less efficient as the main wing has to lift the aircraft’s weight, plus the downforce on the tailplane.
So the F-16 designers decided to eliminate the tailplane downforce, improving agility at the expense of stability, and also efficiency. However, the result was an aircraft so unstable no human could hope to fly it. Hence, we have fly-by-wire where humans suggest an input to vehicle, and the computers translate that into action. This tech has existed for a long time – the F-16’s first flight was in 1974.
The F-16’s dynamics are kind of like a heavy trailer operating at 0% towball mass towed behind a car half its weight doing 150km/h. Madness, right? Not if there’s constant, tiny, microscopic corrections.
Steering out of trailer sway is similar to trying to fly an F-16 manually. You’ll need to somehow turn the steering wheel fast enough, and exactly at the point to counteract the trailer. This is incredibly difficult as you can’t go off what you’re feeling in the car – if the car swings out and you react, well that’s too late, it’s not like the car skid itself is the problem.
Could the average driver do it? Not a hope. The average driver cannot even recover an oversteer skid in a car without a trailer, and I know, I’ve designed and run car control classes. In fact, many amateur race drivers cannot properly execute skid recovery in their sports or racing cars, on a racing track, when they are primed to do so – again, I’ve followed enough to see that and you can watch my skid recovery videos where I have collection of mishaps. Therefore, the chances of you ‘steering out of sway’ are not zero, but on the minimal side of tiny.
Another way to think of steering out of sway is to consider your trailer – now back it up at 50km/h. And now, add another trailer behind that. Could you reverse that at 50km/h? If you can, I will accept you could steer out of sway.
Have people ever steered out of sway? Yes. Skill? Possibly. Luck? More likely they were so slow to react they accidentally ended up steering at the right time, or something else happened.
You know what is really good at steering out of sway? Computers. Your modern towcar has something called TSC, or Trailer Stability Control. That is a system which detects sway quicker than you can, and makes tiny, incredibly rapid braking pulses to each wheel to counteract the sway, much like the way the F-16’s computers are constantly fighting to stop the aircraft flipping out of control.
Again…if you have a brake controller, just operate that to kill sway. Don’t try and steer out of. Don’t try and power out of it
Press Away The Sway
Pictured is the YF-16, tech demonstrator for the F-16. I wonder what the pilot must have thought. “I sure hope these engineers have their sums right!”
Actually the first ‘flight’ wasn’t a full circuit, it was a series of faster taxis. Still, there would have been a time when it was time to really get airborne, and I’m sure the pilot would have been thinking hard about the ejection seat and whether he’d actually have time to get that Martin Baker tie.
