(b.) A flying machine of 50 metres or upwards in length, when at anchor or moored on the water, shall, in the forward part of the flying machine, carry one such light, and at or near the stern of the flying machine, and at a height that it shall not be less than 5 metres lower than the forward light, another such light.

The length of a flying machine shall be deemed to be the overall length;

(c.) Flying machines of 50 metres or upwards in span, when at anchor or moored in the water, shall in addition carry at each lower wing tip one light as specified in (a) of this paragraph.

The span of a flying machine shall be deemed to be the maximum lateral dimension.

12. In the event of the failure of any of the lights specified under these rules to be carried by aircraft flying at night, such aircraft shall land at the first reasonably safe opportunity.

13. Nothing in these rules shall interfere with the operation of any special rules made by any State with respect to the additional station or signal lights for two or more military aircraft, or for aircraft in formation, or with the exhibition of recognition signals adopted by owners of aircraft which have been authorised by their respective Governments and duly registered and published.

SECTION II.-Rules as to Signals.

14.-(a.) An aircraft wishing to land at night on aerodromes having a ground control shall before landing fire a green Very's light or flash a green lamp, and in addition shall make by international Morse code the letter-group forming its call-sign;

(b.) Permission to land will be given by the repetition of the same call-sign from the ground, followed by a green Very's light or flashing a green lamp.

15. The firing of a red Very's light or the display of a red flare from the ground shall be taken as an instruction that aircraft are not to land.

16. An aircraft compelled to land at night shall, before landing, fire a red Very's light or make a series of short flashes with the navigation lights.

17. When an aircraft is in distress and requires assistance, the following shall be the signals to be used or displayed, either together or separately:

(a.) The international signal, SO S, by means of visual or wireless signals;

(b.) The international code flag signal of distress, indicated by NC:

(c.) The distant signal, consisting of a square flag having either above or below it a ball, or anything resembling a ball;

(d.) A continuous sounding with any sound apparatus;

(e.) A signal, consisting of a succession of white Very's lights fired

at short intervals.

18. To warn an aircraft that it is in the vicinity of a prohibited zone and should change its course, the following signals shall be used:

(a.) By day: three discharges, at intervals of ten seconds, of a projectile showing, on bursting, white smoke, the location of the burst indicating the direction the aircraft should follow;

(b.) By night: three discharges, at intervals of ten seconds, of a projectile showing, on bursting, white stars, the location of the burst indicating the direction the aircraft should follow.

19. To require an aircraft to land, the following signals shall be used:

(a.) By day three discharges, at intervals of ten seconds, of a projectile showing on bursting black or yellow smoke;

(b.) By night: three discharges, at intervals of ten seconds, of a projectile showing on bursting red stars or lights.

In addition, when necessary to prevent the landing of aircraft other than the one ordered, a searchlight, which shall be flashed intermittently, shall be directed towards the aircraft whose landing is required.

20.—(a.) In the event of fog or mist rendering aerodromes invisible, their presence may be indicated by a balloon acting as an aerial buoy and/or other approved means;

(b.) In fog, mist, falling snow or heavy rainstorm, whether by day or night, an aircraft on the water shall make the following sound signals with a sound apparatus:

(1.) If not anchored or moored, a sound at intervals of not more than two minutes, consisting of two blasts of about five seconds' duration with an interval of about one second between them.

(2.) If at anchor or moored, the rapid ringing of an efficient bell or gong for about five seconds at intervals of not more than one minute.

SECTION III.-Rules of the Air.

21. Flying machines shall always give way to balloons, fixed or free, and to airships. Airships shall always give way to balloons, whether fixed or free.

22. An airship, when not under its own control, shall be classed as a free balloon.

23. Risk of collision can, when circumstances permit, be ascertained by carefully watching the compass bearing and angle of elevation of an approaching aircraft. If neither the bearing nor the angle of elevation appreciably change, such risk shall be deemed to exist.

24. The term "risk of collision" shall include risk of injury due to undue proximity of other aircraft. Every aircraft that is required by these rules to give way to another to avoid collision shall keep a safe distance, having regard to the circumstances of the case.

25. While observing the rules regarding risk of collision contained in paragraph 24, a motor-driven aircraft must always manœuvre according to the rules contained in the following paragraphs as soon as it is apparent that, if it pursued its course, it would pass at a distance of less than 200 metres from any part of another aircraft. 26. When two motor-driven aircraft are meeting end on, or nearly end on, each shall alter its course to the right.

27. When two motor-driven aircraft are on courses which cross, the aircraft which has the other on its own right shall keep out of the way of the other.

28. An aircraft overtaking any other shall keep out of the way of the overtaken aircraft by altering its own course to the right, and must not pass by diving.

Every aircraft coming up with another aircraft from any direction more than 110 degrees from ahead of the latter, i. e., in such a

position with reference to the aircraft which it is overtaking that at night it would be unable to see either of that aircraft's side lights, shall be deemed to be an overtaking aircraft, and no subsequent alteration of the bearing between the two aircraft shall make the overtaking aircraft a crossing aircraft within the meaning of these rules, or relieve it of the duty of keeping clear of the overtaken aircraft until it is finally past and clear.

As by day the overtaking aircraft cannot always know with certainty whether it is forward or abaft the direction mentioned above from the other aircraft, it should, if in doubt, assume that it is an overtaking aircraft and keep out of the way.

29. Where by any of these rules one of the two aircraft is to keep out of the way, the other shall keep its course and speed. When, in consequence of thick weather or other causes, the aircraft having the right of way finds itself so close that collision can not be avoided by the action of the giving-way aircraft alone, it shall take such action as will best aid to avert collision.

30. Every aircraft which is directed by these rules to keep out of the way of another aircraft shall, if the circumstances of the case admit, avoid crossing ahead of the other.

31. In following an officially recognised air route every aircraft, when it is safe and practicable, shall keep to the right side of such

route.

32. All aircraft on land or sea about to ascend shall not attempt to "take off" until there is no risk of collision with alighting aircraft. 33. Every aircraft in a cloud, fog, mist or other conditions of bad visibility shall proceed with caution, having careful regard to the existing circumstances and conditions.

34. In obeying and construing these rules, due regard shall be had to all dangers of navigation and collision and to any special circumstances which may render a departure from the above rules necessary in order to avoid immediate danger.

SECTION IV.-Ballast.

35. The dropping of ballast other than fine sand or water from aircraft in the air is prohibited.

SECTION V.-Rules for Air Traffic on and in the Vicinity of Aerodromes.

36. At every aerodrome there shall be a flag hoisted in a prominent position which shall indicate that if an aircraft about to land or leave finds it necessary to make a circuit, or partial circuit, such circuit shall be left-handed (anti-clockwise) or right-handed (clockwise), according to the colour of the flag. A white flag shall indicate a right-handed circuit, i. e., that the flag is kept to the right side or side which carries the green light of the aircraft, and a red flag shall indicate a left-handed circuit, i. e., that the red flag is kept to the left side or side which carries the red light of the aircraft.

37. When an aeroplane starts from an aerodrome it shall not turn until 500 metres distance from the nearest point of the aerodrome, and the turning then must conform with the regulations provided in the preceding paragraph.

38. All aeroplanes flying between 500 and 1,000 metres distance from the nearest point of an aerodrome shall conform to the abovementioned circuit law, unless such aeroplanes are flying at a greater height than 2,000 metres.

39. Acrobatic landings are prohibited at aerodromes of contracting States used for international aerial traffic. Aircraft are prohibited from engaging in aerial acrobatics within a distance of at least 2,000 metres from the nearest point of such aerodromes.

40. At every recognised aerodrome the direction of the wind shall be clearly indicated by one or more of the recognised methods, e. g., landing tee, conical streamer, smudge fire, &c.

41. Every aeroplane when taking off or alighting on a recognised aerodrome used for international air traffic shall do so up-wind, except when the natural conditions of the aerodrome do not permit.

42. In the case of aeroplanes approaching aerodromes for the purpose of landing, the aeroplane flying at the greater height shall be responsible for avoiding the aeroplane at the lower height, and shall as regards landing observe the rules of paragraph 28 for passing. 43. Aeroplanes showing signals of distress shall be given free way in attempting to make a landing on an aerodrome.

44. Every aerodrome shall be considered to consist of three zones when looking up-wind. The right-hand zone shall be the taking-off zone, and the left-hand shall be the landing zone. Between these

there shall be a neutral zone. An aeroplane when landing should attempt to land as near as possible to the neutral zone, but in any case on the left of any aeroplanes which have already landed. After slowing up or coming to a stop at the end of its landing run, an aeroplane will immediately taxi into the neutral zone. Similarly, an aeroplane when taking off shall keep as far as possible towards the right of the taking-off zone, but shall keep clear to the left of any aeroplanes which are taking off or about to take off.

45. No aeroplane shall commence to take off until the preceding aeroplane is clear of the aerodrome.

46. The above rules shall apply equally to night landings on aerodromes, when the signals shall be as follows:

(a.) A red light shall indicate a left-hand circuit, and a green light shall indicate a right-hand circuit (see paragraph 36). The right-hand zone will be marked by white lights placed in the position of an "L," and the left-hand zone will be similarly marked. The "L's" shall be back to back, that is to say, the long sides of the "L's" will indicate the borders of the neutral zone, the direction of landing shall invariably be along the long arm of the "L," and towards the short arm. The lights of the "L's" should be so placed that the lights indicating the top extremity of the long arm shall be the nearest point on the aerodrome upon which an aeroplane can safely touch ground. The lights indicating the short arm of the "L" should indicate the limit of safe landing ground for the aeroplanes, that is, that the aeroplane should not over-run the short arm (see diagram A);

(b.) Where it is desired to save lights and personnel the following system may be used:

Two lights shall be placed on the windward side of the aerodrome to mark the limits of the neutral zone mentioned in paragraph 44, the line joining the lights being at right angles to the direction of

the wind. Two more lights shall be placed as follows: one on the leeward side of the aerodrome on the line drawn parallel to the direction of the wind and passing midway between the two lights on the windward side, to show the extent of the aerodrome and the direction of the wind, and the other shall be placed midway between the two lights marking the limits of the neutral zone (see diagram B).

Additional lights may be symmetrically put along the boundary lines of the neutral zone, and on the ends of the taking-off and landing zones on the line through the three lights on the windward side.

47. No fixed balloon, kite, or moored airship shall be elevated in the vicinity of any aerodrome without a special authorisation, except in the cases provided for in paragraph 20.

48. Suitable markings shall be placed on all fixed obstacles dangerous to flying within a zone of 500 metres of all aerodromes.

SECTION VI.-General.

49. Every aircraft manoeuvring under its own power on the water shall conform to the Regulations for Preventing Collisions at Sea, and for the purposes of these regulations shall be deemed to be a steam-vessel, but shall carry the lights specified in the preceding rules, and not those specified for steam-vessels in the Regulations for Preventing Collisions at Sea, and shall not use, except as specified in paragraphs 17 and 20 above, or be deemed to hear the sound signals specified in the above-mentioned Regulations.

50. Nothing in these rules shall exonerate any aircraft, or the owner, pilot or crew thereof, from the consequences of any neglect to carry lights or signals, or of any neglect to keep a proper lookout, or of the neglect of any precaution which may be required by the ordinary practice of the air, or by the special circumstances of the

case.

51. Nothing in these rules shall interfere with the operation of any special rule or rules duly made and published relative to navigation of aircraft in the immediate vicinity of any aerodrome or other place, and it shall be obligatory on all owners, pilots, or crews of aircraft to obey such rules.