Air Port or Air Station Aerodrome

AERODROME, AIR PORT or AIR STATION. An aircraft can land and take off safely in any large open space, but an organized and equipped aerodrome is required for regular flying. Just as railways must have depots and stations of vary ing kinds and ocean-going liners must have harbours and docks, so is it necessary for aircraft to possess aerodromes.

Provision of Aerodromes.

On a recognized air route for the operation of land machines, such, for example, as that from Lon don to the Continent, a series of aerodromes is provided at an approximate average distance apart of 25m. Croydon, outside London, Le Bourget, serving Paris, and Tempelhof at Berlin are terminal aerodromes, while between London and the Channel, for instance, there are intermediate fields at Penshurst, Marden and Littlestone. Lympne, which has become a prominently active aerodrome, is but five miles from Littlestone, but when Lympne on the high ground formed by the cliffs overlooking Hythe is ob scured by low clouds drifting in from the sea, Littlestone at sea-level is available to Croydon-Le Bourget traffic. Croydon and Lympne are provided with customs facilities, as are, of course, the great aerodromes of the Continent.

The Terminal Aerodrome.

The ideal terminal aerodrome should be close to the heart of the city which it serves; but in the event of this being impossible it should be provided with good communications by road, rail, train or bus. Consideration must be given to adverse meteorological conditions, especially fog.

The ideal layout for an aerodrome is to place the main block of buildings, surrounded by the hangars, in the centre of the aerodrome so that unnecessary taxying is avoided. Such an arrangement also keeps the landing area clear of interference from aircraft manoeuvring on the ground. One drawback is that it is necessary either to have an access road across a part of the ground used for flying, which would be both dangerous and inconvenient since it would tend to cause delays; or else to construct a tunnel road under the aerodrome, a very costly item. From an opera tional standpoint, the advantages of such a system far outweigh the disadvantages ; but the main obstacle to its adoption is the large area of ground that would be required, since it must be of sufficient dimensions to give a clear take-off run in any direction. Consequently it is the normal practice to group all the buildings together on one side of the aerodrome where adequate approach facilities by road exist.

The site should afford at least i,000yd. run into any wind. The soil should be light, the land level and for choice a plateau. The land immediately surrounding the site should be free from obstructions.

Aerodromes for the use of flying boats or seaplanes have an open-water site from which to depart and on which to alight, and slipways leading from this water site to the hangar accommoda tion and to the departure and arrival platforms.

Equipment.

A terminal aerodrome normally is equipped with hangars for the housing of aircraft, workshops, bonded and tech nical stores, administrative and booking offices for the companies operating services from the stations, as well as for travel and transport agencies, petrol and oil companies, etc. In addition, facilities frequently exist for the customs and for the immigra tion authorities. Aerodromes are further provided with wireless and meteorological facilities, together with government personnel to operate them. Illuminating beacons for the assistance of air craft flying by night, and some device for indicating the direction of the wind both by day and by night, are installed. Accommo dation is provided for an official belonging to the government aeronautical inspection department, whose duty it is to ensure that aircraft are being properly maintained; for traffic workers to carry out porterage duties and assist in handling machines on the ground ; and for the officials appointed by the government for controlling air traffic, the aerodrome, and the government per sonnel employed there.

Emergency Landing Grounds.

Emergency landing grounds between terminals may, or may not, be equipped with hangar ac commodation, but are normally provided with beacons and wind indicators. Telephones are generally installed, but no personnel other than a caretaker is ordinarily found there. Emergency land ing grounds are now usually equipped with hangar accommodation and many have beacons and wind indicators. Most of the sta tions on the route to the Continent show their names in large capital letters.

Lighting.

Adequate lighting facilities are essential to take care of the night flying traffic which is steadily increasing each year in a great number of countries.

Aside from the navigation beacons along an air route and the various radio aids to a pilot in flight, his departure point and destination must be well marked at night with safety and danger light signals, and he should have the assistance of powerful flood lights when leaving the ground or landing.

The field boundaries must be marked off and all obstructions, such as wires, buildings, towers, etc., should be indicated with red lights. A huge revolving beacon usually guides approaching craft to the aerodrome, and as it comes in for landing, flood lights are turned on the runway. Millions of candlepower in these floodlights throw a flat, fan-shaped beam horizontally over the runway and its bordering terrain, producing an effective equivalent to 75% or more daylight, with no confusing shadows. In addition to the lighting facilities on the ground, the pilot of any large plane has available his own landing lights in the wings of the ship, these being particularly valuable as he ap proaches the field.

Considerable experimentation has been carried on in search of a light that will penetrate fog, but comparatively little success has been attained in this direction, and pending perfection of blind landing methods through the combined medium of radio and instruments, most pilots play safe and avoid fog bound areas, choosing instead the nearest field that is clear and from which passengers and the plane's mail and express load are transferred by rail or motor to the most accessible metropolitan city.

International Obligations.

Under the International Con vention for the Regulation of Air Navigation (see AVIATION, Civil-) the contracting States, of which Great Britain is one, must nominate customs aerodromes, and the chief countries of the world have accepted it as a principle that the government or local authorities should be responsible for providing and maintaining the air ports required in international air navigation. Every air craft engaged in international flying must, before proceeding from one country to another, be cleared by the customs and must make its final departure from an appointed customs aerodrome; sim ilarly an aircraft arriving from another country must make its first landing at a cust )ms aerodrome for examination before pro ceeding elsewhere.

The Convention secures uniformity in such matters as markings, lighting, signals, rules, etc., at all public aerodromes belonging to the contracting States, whether owned by the Government or otherwise; also it provides that every public aerodrome must be available to the aircraft of all contracting States on exactly the same terms as to national aircraft.

The majority of contracting States have issued their own regu lations. In the British regulations, which are laid down in the Air Navigation (Consolidation) Order, 1923, and Amending Orders, 1925 and 1927, an aerodrome is defined as follows :— "Aerodrome" means any definite and limited ground or water area intended to be used either wholly or in part for the landing or departure of aircraft. Aircraft in this connection includes all balloons, whether fixed or free, kites, airships and flying machines.

All aerodromes in Great Britain and Northern Ireland, which are used as regular places of landing or departure by aircraft carrying passengers for hire or reward, must be licensed for the purpose by the Secretary of State for Air.

Service (Royal Air Force) Aerodromes.

Apartfrom the special facilities required at a civil aerodrome for commercial traffic, all the remaining features except some regarding lighting are to be found equally at a service aerodrome—with the addition of quarters for the officers and airmen and the installations neces sary for service operations and training.

The situation of a service aerodrome in peace time is governed largely by the nature of the units to be stationed there. It is gen erally unnecessary and undesirable that a service aerodrome should be located near a large town. The only exceptions to this rule are aerodromes belonging to squadrons of the Auxiliary Air Force which must be reasonably near the homes of their volun teer personnel.

Aerodromes used for training in flying are situated as a rule in the midst of open country to neutralize risk of forced landings. Aerodromes for fighting and bombing squadrons are disposed ac cording to strategic requirements. As bombing squadrons are equipped with heavy aircraft it is particularly necessary in their case that the aerodrome should have a hard surface and not be come soft in rainy weather. For co-operation with the Army and Navy it is necessary that aerodrome and seaplane stations should be provided in the vicinity of the areas employed for combined training. A number of aerodromes are also required for experi ment and tests in connection with new types of aircraft and equipment