ORIGINAL: alan0899
G'day Brad,
If the plane reaches terminal velocity, so does the fuel in the tank, so it stays where it is, for the fuel to move forward, it must be moving faster than the plane, how can it be moving faster? Gravity can't do it, because the plane & everything in it, is moving faster than terminal velocity.
The only way that any of this can happen, is if the plane is slowed down, by possibly a large prop, acting as a break, but that is unlikely, as most pilots don't throttle back enough to cause this slow down effect, they do full power dives, usually the plane pays the price, by snapping the wings, when it is pulled out of the dive.
As bkdavy says, this is a quite common misconception in the RC world.
Terminal velocity is NOT the speed of free fall in a vacuum.
In effect the fuel in the tank is not being subjected to the air resisting the plane's motion... and free fall is FASTER than terminal velocity speed, so the fuel falls forward.
This can and will lead to deadsticks on prolonged downline manouvers especially once the tank falls below 70-60% fuel remaining.
What keeps the engine running is the remaining fuel in the lines coupled with a lower throttle.
A full speed dive ( which still may be slower than 1G acceleration downward ) can quickly deplete the remaining fuel leading to a deadstick.
Manouvers such as blenders permit a plane to "fall" nose down for quite a long time... something that got me into this discussion, as my Funtana had a pronounced tendancy to deadstick at the bottom of a long blender...
The video shows all of this quite well and helps dispell the "fuel remains at the back" myth.