THE HONG KONG GOVERNMENT GAZETTE, DECEMBER 17, 1937.
pelled to land and is unable to transmit its intended message owing [Schedule to the rapidity of the landing, but does not require immediate IV,-contd.] assistance.
(c) When ап aircraft has a very urgent message to transmit concerning the safety of the aircraft or of any person on board or within range of assistance or the safety of another aircraft, or of any ship or vehicle, the following signals (which as a general rule will be addressed to a specific authority) shall be used or displayed, either together or separately, before the sending of the message:-
(i) In radiotelegraphy the group XXX (
with the letters of each group and the successive groups clearly separated from each other.
(ii) In visual signalling either a succession of green pyrotechnical lights or a succession of green flashes made with signalling apparatus.
(4) As to safety signals:-
When an aircraft is about to transmit a message concerning the safety of navigation or giving important meteorological warnings, the following signals shall be used, either together or separately, before the sending of a message:-
(a) In radiotelegraphy the group TTT (
) with the letters of each group and the successive groups clearly separated from each other.
(b) In radiotelephony the French word "SECURITE" corre- sponding to the English pronunciation of the syllables SAY-CURE- E-TAY.
(c) In
visual signalling the international visual signalling procedure as laid down in the International Code of Signals.
Other Signals to or from Aircraft.
18. At aerodromes open to public use:-
(1) By day and by night when there is an officer controlling traffic, he shall, except as permitted by sub-paragraph (2) of this paragraph, use the following signals (which may be preceded by the last three letters of the registration group of the aircraft to which the signal is addressed sent in the International Morse Code by using a luminous beam of the same colour as the signal which is to follow):
(a) to authorize movement on the landing area other than taking-off, he shall direct at the aircraft an intermittent white luminous beam;
(b) to authorize taking off, he shall direct at the aircraft a continuous white luminous beam;
(c) to prohibit taking off or any movement on the landing area, he shall direct at the aircraft an intermittent red luminous beam.
(2) By day, when there is on the landing area an officer con- trolling traffic, he may use the following signals:
(a) to authorize movement on the landing area other than taking-off, he shall wave a small white flag in the direction to be followed as shewn in the diagram below
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