Signals visible from the ground
60.—(1) A black ball, 60 centimetres in diameter, suspended from a mast signifies that the directions of take off and landing are not necessarily the same.
(2) A chequered flag or board, 1.2 metres by 90 centimetres, containing 12 equal squares, 4 horizontally and 3 vertically, coloured red and yellow alternately, signifies that aircraft may move on the manoeuvring area and apron only in accordance with the permission of the air traffic control unit at the aerodrome.
(3) Two red balls, 60 centimetres in diameter, positioned vertically one above the other, 60 centimetres apart and suspended from a mast, signify that glider flying is in progress at the aerodrome.
(4) Black, Arabic numerals in two-figure groups and, where parallel runways are provided, the letter or letters L (left), LC (left centre), C (centre), RC (right centre) and R (right), placed against a yellow background, indicate the direction for take-off or the runway in use.
(5) A black letter C against a yellow background, as illustrated in this paragraph,
indicates the position at which a pilot can report to the air traffic control unit or to the person in charge of the aerodrome.
(6) A rectangular green flag of not less than 60 centimetres square and not more than 66 centimetres square, flown from a mast, indicates that a right-hand circuit is in force.