428 THE HONG KONG GOVERNMENT GAZETTE, AUGUST 16, 1929.
SCHEDULE,—Continued.
Provisions Amended.
Schedule IV, Para. 16.)
Schedule IV, Para. 17.
Schedule IV, Para. 31.
Amendment.
make intermittent signals either with a lamp or projector other than the navigation lights or with any sound apparatus. In addition, it shall make by international Morse code, by means of sound or luminous signals, the two-letter group constituted by its nationality letter and the last letter of its registration mark.
(b) Permission to land will be given by the same two-letter sign from the ground, made with a green light and followed by intermittent signals of the same colour."
For paragraph 16 the following paragraph shall be substituted :-
"16. An aircraft compelled to land at night shall before landing make with its navigation lights a series of short and intermittent flashes."
Paragraph 17 shall be amended :-
(1) by inserting after sub-paragraph (a) the following new sub- paragraph :-
"C
(aa) The international distress call 'MAYDAY' (corres- ponding to the French pronunciation of the expression
m'aider) by means of radio-telephony ";
(2) by inserting the following words at the end of the paragraph :-
"When an aircraft desires to signal that it is in difficulties, or about to land compulsorily, or has momentarily interrupted its flight, but does not consider it necessary to ask for immediate assistance by using the signal SOS it shall use the international urgent signal PAN by means of radio- telegraphy or radio-telephony.
$
Where radio-telegraphy is used the three letters must be well separated so that the signals AN' may not be transformed into one signal 'P.' The urgent signal may be transmitted only with the authorisation of the commander or person responsible for the aircraft.”
For paragraph 31 the following paragraph shall be substituted :—
"31. In order to obviate the increased risk of collision which exists on air traffic routes, the following rules shall, so far as it is safe and practicable, be observed when flying on or in the vicinity of such
routes:-
(a) Every aircraft when flying by compass along the straight line (rhumb line) joining two points on an air traffic route in common use, shall keep such line at least 500 yards on its left.
(b) Every aircraft following an air traffic route, which has been officially recognised, shall keep such route at least 300 yards on its left.
(c) Every aircraft which, in the vicinity of a route frequented by aircraft, is following a line of landmarks such as a road, railway, river, canal or coast line, etc., shall keep such line of landmarks at least 300 yards on its left.
(d) An aircraft shall not fly keeping any of the lines or routes above referred to on its right, except at a distance there- from sufficient to avoid aircraft following such lines or routes in accordance with these rules.
(e) When crossing one of these lines or routes above referred to, an aircraft shall cross it at right angles as rapidly as possible and as high as is reasonably practicable.
(f) In the case of flights in group formation the aircraft of the leader of the group shall be responsible for leading the flight in such a manner that every aircraft in the group can comply with the above rules of this paragraph."