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Setting up of an Airship Base

With the Imperial Airship Scheme underway in 1926, the plans for other airship bases was planned for expansion. Masts were constructed at Montreal, Ismalia in North Egypt and Karachi in India. The mast head for South Africa had been constructed and a shed was also constructed in Karachi. The following guidelines were laid out for setting up masts and bases at further destinations, these included Mobassa, Capetown, Perth, Melbourne and Wellington.

Text taken directly from Air Ministry document "Approach Towards A System of Imperial Air Communications" Memorandum by the Secretary State for Air laid before the Imperial Conference 1926, together with the REPORT of the Imperial Air Communications Special Sub-Committee


Selection of Site
Whilst the linking up of commercial centres is the main object of high speed airship transport, there are certain operational factors which have to be borne in mind in selecting the precise site for an airship base and settling the type of base to be erected. A commercial airship will normally fly at a height above the ground of about 2,500-3,500 feet. While there is no difficulty in flying higher than this, evrery 1,000 feet of height means a loss of about one-thirtieth of the total lift, and consequently diminishes the airship's carrying capacity.

It follows from this that a site for an airship base should be selected as nearly as possible at sea level, since if an airship base is situated, say, 2,000 feet above sea level, the airship on leaving would halve less useful lift for freight. For the same reason the base should, if possible, not be sited so as to necessitate flying over mountain ranges at the outset or in the early part of the journey, since the ascent can only be made by reducing the load of the airship which is uneconomic from the operating point of view.

On the other hand when an airship has been flying for some time and has thus used up a certain weight of fuel, an increase of height can be gained without the same loss of useful load. Due regard should also be paid to weather conditions, especially in choosing a site for a shed base with docking facilities, where an airship may have to be man-handled into the shed. They are not of so great consequence for an inter- mediate base with mooring mast only, as the airship would always be flown from the mast and not handled on the ground.

At the same time local meteorological conditions might affect regularity of service; thus a locality in which thunderstorms are prevalent would generally be unsuitable. It was on account of climatic conditions that the shed base for India was sited at Karachi, leaving the question of bases at Bombay and Calcutta to be dealt with later. In the immediate vicinity of a base there should be no obstruction such as hills, high buildings, etc., and any high masts for wireless telegraphy or meteorological purposes should be located as far as possible from the mast and shed, 'so as not to be a source of danger to an airship landing or leaving.

Local communications
Should be good to permit of passengers and freight being dealt with expeditiously. A main railway line should be in the vicinity. Feeder services by aeroplane should also be kept in view. .

Area for Shed and Mooring Mast Base
A minimum area of about 600 acres is necessary, but a larger area (up to 1,000 acres) is preferable in order to provide for future extensions, in particular additional mooring masts.

Area for Mooring Mast Base
A clear space of about 800 yards square (about 130 acres) will suffice for a base with one mast provided there are no buildings of a greater height than 40 feet within 300 yards of the aerodrome. As the space required for landing operations at the mast is only about 100 acres, it is possible to use the remainder for grazing or other purposes. All electric cables in the vicinity of a base should be laid underground.

Drainage and Foundations
The land should be well drained and not subject to floods. In order to avoid expensive foundations the soil should be suitable for loads of not less than 2 tons per square foot.

Water Supply
There should be a plentiful supply of fresh water for ballast and general purposes. Salt water will not serve. owing to its corrosive action on aluminium alloys. The total amount of water required when abase is fully functioning is one of the questiot:ls on which the experimental flights will throw light. As an approximate estimate, the following figures may be given :-
For ballast for each airship at the mast 50,000 gallons per day.
For general purposes. .20,000 per dayI
For hydrogen, assuming a production of 1,000,000 cubic feet per week, by water gas process 20,000 per day or by electrolytic process..3-5,000 per day
Average weekly total, say 700,000 gallons. If a temporary hydrogen plant (silicol) is erected, an additional 200,000 gallons per week would be required. To meet any emergency a 100,000 gallon reservoir will be necessary) at most sites.

The dimensions laid down for the shed in course of erection at Karachi are:-
Length 850 feet.
Width 180 feet.
Height 170 feet.
The shed is constructed to stand a wind pressure :--- (a) 35 lbs. per square foot horizontally on roof. (b) 30 lbs. per square foot horizontally on sides or ends. (c) 30 lbs. per square foot horizontally on main sliding doors with doors open or shut. A shed of the above dimensions will probably meet future requirements for the next 10-15 years, but in any case as sufficient height has been allowed to meet further developments in the design of airships, the question of extension is not a serious matter. Good ventilation is necessary to allow easy escape of hydrogen, and a!l electric fittings should be gas tight to prevent explosions. As contracts for such buildings are of considerable magnitude, the design and execution should be supervised by an Engineer of repute, and only Contractors experienced in this work or used to erecting similar large engineering structures should be invited to tender.

Mooring Mast
The existing type of mast consists of a steel structure 200 feet high, fitted with a receiving arm at the top to which the airship is anchored. The structure is built to withstand the pull of the airship up to 30 tons in any direction, in addition to a wind force on the structure of 30 lbs. per square foot. A lift is provided to convey passengers up and down the mast. Mains for hydrogen, water and fuel run up the mast for the replenishment of the ship, and are joined to similar mains in the ship by flexible connections. The mast should be sited in such a position that an airship arriving or departing does not have to fly over the shed or other high buildings) and in any case these should be at least 800 to 1,000 yards away.

Anchor Points
Twenty-four snatch block anchor points should be provided to take the sideguys when the. airship is landing to the mast. These should be spaced in a circle round the mast at a radius of 750 feet from it, and should be designed to take a maximum pull of 25 tons in any direction. They should be placed flush with the ground to avoid obstruction.

Hydrogen Plant
The type of hydrogen plant to be provided will vary according to locality and requirements. There are a number of processes used in connection with hydrogen production, but only three of these have been used to any extent. in this country in making hydrogen for aeronautical purposes, viz., iron contact or water gas process, electrolytic process, silicol process. The latter would not normally be used at permanent bases on account of its high cost of production, but is useful as a temporary arrangement when a large output of gas is required intermittently at low capital cost. An outputof 1,000,000 cubic feet per 24 hours can be obtained from a plant costing 20,000 to 25,000. Plants of the iron contact and electrolytic types cost about 80,000 including cost of storage holders of 1,000,000 cubic feet capacity (about 30,000), which are necessary on account of slow rate of production. These figures are for plants capable of producing about 1,000,000 cubic feet per week, which is the amount of gas which should be available at anyone time, on a route operated by airships of 5,000,000 cubic feet capacity. In both the iron contact and electrolytic processes work has to be continuous, and shifts are necessary. The selection of one or the other will depend largely on whether cheap coke or cheap electricity is available.

Power and Light
If local current is not available, a power plant of 100 kilowatts will probably be required, preferably two 50 kilowatt sets. and two 10 kilowatt sets for light loads such as lighting, and wireless sets, for use when the larger plant is not running. An additional 100 kilowatt set might. be needed for a permanent station in regular operation.

Fuel Storage
A minimum supply of 10,000 gallons of fuel should be available for refuelling airships

For the experimental flights of R.100 and R.101 it is estimated that the ground staff at the shed base at Karachi will be about 150, of whom 100 will probably be natives; at the mooring mast base at Ismailia the total may be 100, of whom about 70 may be natives. These figures will be checked and possibly revised as the result of the experimental flights.

Meteorological and Wireless Telegraphy Arrangements

A local meteorological section is necessary at each airship base to deal with local conditions and to receive reports from other stations, and transmit them to airships in flight. 'roo much importance cannot be placed on this organisation, as not only is it an aid to safe navigation, but it will also enable an airship to take the most favourable route, and thus facilitate the economical running of an airship line. The main function of Wireless Telegraphy at an airship base will be the transmission of the meteorological data, and the carrying out of direction finding work, as an aid to the usual navigation methods. A local Wireless Telegrapliy set should also be available to ;-elay messages through the nearest high-power station. The receiving station and meteorological office should be housed as far as possible in the same building or in the immediate vicinity of each other .

Capital Cost of Bases
It is very difficult to give a figure for the costo! bases when a regular service is in operation, as so much will depend on .the scale and type of accommodation provided for dealing with passengers, mails and freight. The cost of erection will also vary in different dominions and localities. The following figures, which are based on the cost of the works carried out for the Air Ministry for the purpose of the experi- mental flights, may serve as a guide to the scale of expenditure involved. Permanent stations on a regularly operated route would probably cost 80,000-100,000 more to build and equip.

Related ships: Imperial Airship Scheme

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