palities receive in return steel hangars from the Government. The maintenance of the air harbor is assumed by the municipalities.

This policy met with great favor in progressive communities, and many cities not comprised in the original Air Service program are now laying out air harbors to government specifications and in cooperation with the Air Service.

AIR-SERVICE SPECIFICATIONS FOR LANDING FIELDS

January 1st, 1920, the Air Service issued revised landing field specifications, which are as follows:

In the selection of landing fields at a city, special attention should be given to the following points:

1. LOCATION:

(a) The Field should be situated close to transportation facilities, both passenger and freight, and electric power and water supply should be available.

(b) An effort should be made to select a location in a place where the field is unlikely to be later surrounded by building operations.

(c) If the city is unable to provide for a field of the ideal size, if possible, a site should be selected which is capable of expansion to a larger size, when the development of aviation makes such expansion necessary.

(d) A special effort should be made, if possible, by cities on the main aerial routes, as the development of trans-continental aviation depends upon the establishment of fields at such points.

2. SIZE:

(a) The size of municipal landing fields depends upon so many factors that it is impossible to prescribe exact regulations concerning it, and it is realized that a great many cities will not be able to establish airdromes to meet the requirements of the specifications set forth herein. The minimum size recommended by this office at the present time and with the present types of machines, is one that will allow 600 yards "Runway" in any direction from which the wind may be likely to blow. Such a field would permit any type of machine at the present day to be landed by an average pilot, and to be taken off without accident, should there be no failure of the motor. To have a field large enough to enable the average pilot to take any and all types of machines away from the field and to keep the machine always in such a position with reference to the field as to be able, in case of failure of the motor, to return to it and to land the plane without accident, it is necessary that there should be a Runway" of at least 1,000 yards in any direction from which the wind is likely to blow. Fields complying with these specifications are designed to take care of airplanes of all types under all conditions of traffic, weather, etc. These specifications are not intended to discourage the establishment

of small fields, as the presence of small fields en route are of vital
importance, and as such, they will function as emergency fields for
airplanes that need a great deal of room to take off and land, and as
landing stations for small or slower planes. In the establishment of
these fields, the general specifications should be followed in regards to
shape, character of ground, approaches, obstacles, etc. Should there
be obstacles around the field, the portion of the field available for
use will be shortened by a distance depending upon the height of
the obstacle. An obstacle 100 ft. high will make at least 700 ft. of
the field unavailable for use. The length of the " Runway" available
for use should be computed by subtracting seven times the height
of the obstacle surrounding the field from the length of the field in
the direction in which the "Runway" is being computed.

(b) Another factor which enters into the size of fields is the question of
the surrounding country. Should a field be located in a locality
where there are fields available for emergency landings immediately
adjacent to the municipal landing field, the danger of accident due to
failure of motor, immediately in the vicinity, will be much lessened
and the need of the 1,000-yard "Runway " is not so urgent. Should
the country surrounding the field, however, be covered with buildings,
or be of such a character that it is impossible to land upon it with
safety, the best interests of aviation demand that the field should be
large enough to enable the pilot to circle the field in any type of
machine, keeping always in such a position as to be able to return
to the field in case of the failure of the motor.
(e) It would thus seem, that it is impossible to make a classification of
landing fields according to size, which would show their relative
suitability for aviation purposes and, accordingly, all classifications
heretofore made are withdrawn.

(d) In addition it may be further noted that there are types of machines
with which it is possible for the average pilot to land in a field, with-
out chance of accidents, with much less than a 600-yd. "Runway."
It is also possible, with average luck, for good pilots to land any
present type of machine in fields of smaller dimensions than 500 yards.

3. SHAPE:

The best shape for a field is that of a square, but an “L” shaped field will suffice, providing each arm provides a satisfactory length of " Runway." It must be pointed out, however, that an "L" shaped field does not provide all the advantages for a return to the field in case of failure of motor, which are possessed by a square field.

4. CHARACTER OF GROUND:

The ground should be firm under all weather conditions. A light, porous soil with natural drainage is recommended as the most suitable. A field with clay soil invariably demands special drainage and is unsatisfactory as a rule during wet weather. It is possible, however, to lay a system of tiling which will drain any field after the hardest rain. The field should be covered with sod. The surface should be level and smooth, so that airplanes can normally land upon and taxi across without injury.

5. APPROACHES:

Surrounding obstacles, such as high buildings, high-tension power lines, trees, etc., limit the amount of field available for landing by the amount indicated above, and in addition provide an element of danger for the pilot in case of mis. adventure.

6. MARKING:

A white circle, 100 feet in diameter with a band 3 feet wide has proven by experience to be an excellent distinctive marking for a landing field. This can be seen at almost any attainable height with clear visibility. By digging out the earth to a depth of about six inches and filling in with crushed rock, a very substantial and economical marker can be made. It is necessary to keep the marking clear white to make it show up well. This can be done by white-washing from time to time. The name of the station should be marked in chalk letters 15 feet long by 3 feet wide. A wind indicator, such as the standard aviation wind cone, should be placed at one corner of the field 30 feet off the ground.

7. ACCOMMODATIONS:

Municipal landing fields should provide communication by telephone, transportation facilities, gasoline, oil and sundry supplies. Hangars, guards, and shop facilities will be needed in addition with the development of the use of the field.

8. CLASSIFICATION :

No classification for municipal landing fields will be published. However, for the purpose of consolidating information in a concise form and for the purpose of furnishing statistics, and furnishing pilots information as to crosscountry routes, the following divisions will be made:

(a) Field from which it is possible for the average pilot to operate every type of machine, even in case of motor failure.

(b) Field from which it is possible for the average pilot to operate every type of machine without danger to the pilot so long as the motor functions.

(c) Field from which it is possible for the average pilot to operate only certain types of machines without danger so long as the motor continues to function. The most skilful pilots will be able to land any type of machine in fields of this classification.

(d) Fields, which of necessity, must be classed as "emergency fields," inasmuch as they are of such a type that only under the most favorable conditions can successful operations be effected.

LANDING FIELDS MEAN SAFETY

The landing field movement derives its great importance from the relation it bears to the safety of flight. The impression prevailed up to the spring of 1919 that cross-country flying was extraordinarily dangerous. Multiplied flights by government and private airplanes disabused the public mind of this false belief, but it was not until the two first practical cross-country races were held, that indisputable

proof was given of the relationship which an air harbor within gliding distance bears to safe mechanical flight.

The winners of both the New York-Toronto and New York-San Francisco races agreed that the greatest need of aviation to-day is the establishment of adequate landing facilities, not only in the thickly populated areas, but along well defined routes across country, which are certain, in years to come, to be followed as commercial highways of the air.

The transcontinental airplane race demonstrated that aerial racing is of itself not nearly as dangerous, even where adequate landing fields are missing, as automobile racing on specially prepared tracks and with ample facilities for repairs and replacement. That this is true may be seen from the following table, in which the New YorkToronto and the transcontinental airplane races, the greatest aerial events of 1919 in the United States, are compared with the 500-mile race on the Indianapolis motor speedway.

Inasmuch as the aerial races in question covered more than ten times the distance of the automobile race referred to, they theoretically gave opportunity for more than ten times as many accidents. Moreover, expert pit service was available for the automobiles and not for the airplanes. Yet more than 54 per cent. of the airplanes finished and only 45 per cent. of the automobiles finished. The fatality rates are graphically shown in the following diagram:

Transportation authorities all over the world are agreed as to the finality the problem of air transport has assumed as a result of the development in aeronautics. That the advent of commercial air services on a wide scale is imminent, no one having studied the question can doubt for a moment. Chambers of Commerce throughout

AIR ROUTES OF THE WORLD

(Land flights in statute miles, sea flights in nautical.)