With the system the model railway enthusiasts use, the cars and trucks have moving wheels and steerable axles (well on those I have seen!) which would need to be replicated on your helicopter.
The only other method I can think of is an animatronic set up where the helo is on a pin that follows a slot made in the deck underneath of which is the mechanism that moves the model back and forth. Therein would lie wobbliness and possible jerkiness if the model needs to move in anything other than a straight line. These issues could be reduced if the pin has guide rollers.
On the animatronic topic, if the model were mounted on two pins that formed the axles of two roller chain links, then the chain could be driven around a course of sprockets (and if needed, rollers to define course changes) under the deck. I drawded a schematic for you

It's down to cost, complexity and desire on your part :)