Why don't short runways use (downhill) ramps for takeoff? This is a followup on question: Why don&#39;t short runways use ramps for takeoff?

There are multiple answers to that question that answer why an uphill ramp at the end of the runway does not make sense. But what about going the other way?



I would imagine a downhill ramp at the beginning of the takeoff roll could give the aircraft more energy on takeoff (converting potential energy to speed), and that could indeed improve takeoff performance. This would be useful at places where extending the runway is not possible.

How the aircraft would get up there is another question, but worst case scenario it could always back-taxi on the runway before turning around and taking off.

Is this practice ever used? If not, what are the reasons?
it could always back-taxi on the runway before turning around and taking off.


So ... that would limit the steepness of the slope significantly, and thus the potential benefit.

Most other aspects are already covered by Bjelleklang's answer: Landing aircraft would either have to clear the obstacle before being able to touch down, or they'd fall over the edge if they don't brake in time (rather than, as these days, get stuck in the grass behind the runway end)