The following rules apply to engines in operation:
(A) No engines shall be started on an aircraft not equipped with adequate brakes, which are fully set or the wheels set with blocks equipped with ropes or other suitable means of removal and not having a competent operator at the controls of the aircraft;
(B) No aircraft engine shall be warmed up except in designated locations;
(C) Aircraft about to use a runway for a take-off shall warm up the engines on the warm-up pad at designated locations;
(D) No aircraft engine shall be run or warmed up unless the aircraft is in such position that the propeller blast shall clear all buildings, parked planes, groups of people in the observation areas and the flight path of landing aircraft.
(`78 Code, § 4.16.030.)