a) Large models are more expensive and cost is a factor in attracting competitors.
b) Safety is very important, large models all launching, flying and landing together can be a hazard to other models, timekeepers, pilots and spectators.
c) The rules are designed to enable as many models as possible to be flown together in order to ensure a fair “man on man” competition format. With normal launch line spacing and every model being launched directly in line with it’s launch position marker, it will have it’s own 10 metre wide launch “corridor” and there will be a minimum of 6 meters between wing tips. Allowing larger models to compete would require more space between launch positions, fewer launch positions and a longer flight line. This could mean that more “slots” per round would be needed and consequently fewer rounds during the event.
d) Their is the possibility of larger models exceeding the 7Kg maximum weight limit imposed by CAA regulations (CAP 658). This could prevent the competition being held without special permission being obtained in advance from the Civil Aviation Authority.
a) The need to ensure that the timekeeper, who will be plugging in a "reader unit" as soon as the model has landed, is completely safe whilst doing so, is paramount. This is an important point in favour of having a cut-off where the motor cannot be restarted. Any firmware allowing re-start would leave the motor live whilst the launch height is being checked by the timekeeper.
b) Allowing motor re-starts would create an entirely new strategic element within F5J, which is not present in eSoaring, (where a motor re-start and a second flight attempt, is allowed.) Allowing a motor re-start in F5J would have the effect of allowing and encouraging some pilots to fly to very considerable distances in poor lift, hoping for better conditions knowing that they can return from very low altitudes by re-starting the motor. This would change the whole dynamic of the competition.
c) It has become evident that some 2.4gHz equipment is unhappy in certain combinations of low altitude, model type, orientation and weather/ground/flying site conditions, so re-starts at low altitude are not something to be encouraged.
d) Because different brands of Tx, and Tx programming vary, there is no definite value of motor off command from the Tx. When the altimeter "sees" the 1.2 us pulse width, the 30 seconds timing is initiated. If the pilot throttles back to below 1.2 mS, the altimeter puts a definite stop on the ESC. It also puts a definite stop on the ESC if the 30 seconds elapses. Whilst a restart within the 30 seconds could be detected, should the motor stop is the result of the 30 seconds elapsing, the pilot may still be giving a significant throttle setting. This would be interpreted as a restart and there is no logic process that could resolve this issue.
e) There is no method of detecting a re-start at a low throttle command that does not exceed 1.2 mS.
Because of the above, the only way of preventing cheating and and competition administration problems is not to allow restarts.