Jamboli (Bulgaria) at 4:30 A.M. on Nov. 21 1917 with over ten tons of machine-guns, ammunition and medical stores. She had passed Khartum when she was recalled and landed again at Jamboli at 5:30 A.M. Nov. 25, having covered 3,000 m. in 97 hr. with her full load of stores.
The Atlantic flight of R34 was slightly better in point of time. Leaving East Fortune, near Edinburgh, at 1:42 A.M. July 2 1919, she reached New York at 1:54 P.M. on July 6 after 108 hr. 12 min. in the air. The return journey to Pulham in Norfolk occupied only 75 hours.
The longest flight by an N.S. airship was 101 hours. The record for an S.S. ship was 51 hr., equally remarkable when it is realized that the crew of three were continuously on duty.
As indicating the regularity of the patrols, it is interesting that in 1918 from Jan. to Nov. there were only eight days on which there was no airship patrol. As showing the life of a ship, that of Coastal No. 9 at her patrol station in Cornwall may be quoted. She was inflated on July i 1916, and deflated on Sept. 14 1918. During this 805 days she flew 2,500 hr., or an average of 3 hr. 6 min. per day, over the whole period. The deduction to be drawn from the airship operations carried out appears to be that for future warlike operations their duties will be limited to those areas where intense hostile anti-aircraft fire or hostile aeroplanes are unlikely to be met. With this reservation their uses are likely to be the same as in the past war, with a very important extension to work over undeveloped country, the airships acting as patrols and for the transport of stores. The use of a large airship as a carrier from which fighting or bombing aeroplanes could be released, and to which they could return, was considered. An aeroplane was on two occasions dropped from a rigid airship with no inconvenience or danger to the pilot. Arrangements for the complementary process of hooking on again were not completed at the time of the Armistice.
For passenger and goods transport over distances longer than the aeroplane can profitably cover at one stage the airship has important advantages. By eliminating the time spent at inter- mediate stops and by flying day and night with the passengers in reasonable comfort, the effective speed over a long journey is probably greater than that of the aeroplane. To this must be added the ability to make long ocean passages in safety and so to select a course as to take advantage of trade winds or local meteorological conditions.
German commercial airship activity was already in 1921 very completely planned and was only suspended by the restrictions of the Peace Treaty. The " Bodensee " had already carried out a remarkable series of flights between Berlin and Friedrichshafen, making 100 flights in 97 days and carrying in all 2,300 passengers. The ship has now been enlarged and a sister ship built in order to extend the flights to Scandinavia. Larger ships and an ex- tension of the service to London and other capitals were con- templated, and a service of ships of considerably larger size from Cadiz to N. and S. America was planned.
Mooring and Handling. The earliest activity of airships had been limited rather by the ability. to handle them on the ground than by their ability to meet weather conditions in flight. British Rigid Air- ship No. I was moored by the bow to a mast and sheltered by a screen on Cavendish Dock, Barrow, before the ship was flown. This trial was successful, the ship remaining safe during winds with gusts up to 48 m. an hour. In the course of these trials the screen was abandoned.
The Royal Aircraft Factory in 1912 devised and used continuously for many months a new form of mooring mast to which a non-rigid airship was attached while floating in the air. To prevent the ship overriding the mast in gusty weather and to facilitate approach, the mast carried at its head a swinging cone duly counterpoised, into which the nose of the airship was drawn by a rope running down the inside of the mast. The cone was free to rotate about the axis of the mast as well as to rock vertically on a universal joint and the mast functioned satisfactorily, save that side gusts caused the cone to rub the bows of the ship with a tendency to bend it. These mast moorings were the precursors of one of the great developments in airship use, but till they were adopted generally the airship had to fie housed in a shed, and hence the activity of the ship was limited to those occasions when it was possible to take her out in winds of less than 10 or 15 m. an hour with a reasonable chance of rehousing her under equally good conditions.
Under war conditions this restriction was serious, and the method
of the mooring mast was again examined. A non-rigid envelope rigged with a dummy car was secured to the head of a mast at Kings- north, first with a cone but later with the cone removed. The ship was reinforced to take the pull of the mast, by fitting inside her bow a spar, the after-end of which was supported by a cone of cords led slightly forward and secured round a circle on the inside of the en- velope. The tension in the fabric of the envelope and in these cords held the spar rigidly, and supplied the reinforcement which was necessary for stiffening the bow of the envelope while in flight and also for mooring.
A further set of experiments was carried out at Barrow with a ship secured to a short stump mast, attached to her mooring point and stepped on a lighter. The point of attachment was not on the axis. Indeed, it was so low on the envelope that side gusts produced se- rious rolling. Accordingly a form was devised in which a somewhat taller mast was fitted with a horseshoe head, so that fittings carried at the top of its arms could be attached to suitably reinforced points aft of the nose of the envelope. This gave support against rolling, but the point of attachment was some distance aft on the ship, and consequently the steadiness was not quite so good as when the en- velope was attached by its extreme bow point.
Definitely comparative tests between mooring at the nose, using the spar inside the bow of the envelope and using the horseshoe mast were carried out at Pulham. After considerable time the internal spar of the former broke, for a reason that was not explained, and the horseshoe mast was preferred. As, however, other means were found for mooring the small ships at advanced patrol stations, the horse- shoe was little employed.
Mast mooring was, however, realized to be important for rigid airships, and prolonged trials with R24 secured to the head of a mast at Pulham were instituted in July 1919 with success. The ship later remained continuously at the mast for 70 days and experienced winds up to 35 with gusts of 43 m. per hour. Difficulty was experi- enced in taking the ship to the mast in any but light winds.
Experiments were continued with R33 on Feb. 2 1921, and up to the beginning of June 1921 the ship had worked entirely from the mast. On a few occasions she had been into the shed, but never for more than five days. During April and May 1921 she averaged between four and five flights per week. In this case the mast is provided at its upper end with a single arm, pivoted at its middle point. Down the centre of this arm passes the wire rope, which is attached to that dropped by the ship and by which she is hauled in. This arm, therefore, comes in contact with the bow of the ship before that has actually reached the head of the rigid mast, and gives im- proved safety as the ship approaches the masthead. Difficulty was experienced with the control of the winch which hauls in the ship's wire. In the experiments with R24 a kite-balloon winch was em- ployed and abandoned owing to its irregular action and control. For the experiments with R33 a steam ploughing engine was used temporarily and found to be satisfactory.
The process of landing to the mast consists in the airship dropping to the ground a rope some 1,000 ft. in length, which is then secured to the rope led from the winch up the centre of the mast and down to the ground. The winch hauls in these ropes and draws the ship to the masthead. There is no difficulty until the ship comes within some 200 ft. of the masthead, but as this distance decreases there is a tendency of the ship to swing both sideways and fore and aft, under the influence of gusts of wind. This difficulty is less serious when the ship is trimmed somewhat down by the stern, so that the wind force on the bow is approximately in the same direction as the tension in the wire. If this arrangement is not made, the variation in the wind force causes swinging of the bow of the ship, and a tendency to over- ride and strike the head of the mast.
Even with the stern of the ship trimmed considerably down, there was still, owing to disturbed conditions, a distinct tendency to swing- ing, and it was often desirable to employ side-guys led from the bow of the ship to fixed points on the ground, in order to guide the bow to the masthead. With these arrangements, it was possible to secure a 6o-ton ship to the head of the mast in winds of 30 m. an hour, with not more than eight men in addition to those actually in the ship.
During the time that R33 was secured to the Pulham mast, an engine was hoisted out and replaced by a spare, and a gasbag was deflated and replaced by a spare.
Three-Wire System of Mooring. As an alternative to the system of mooring an airship to a mast, and as a more temporary arrange- ment, the "three-wire system" was developed from one in which the ship was secured by her mooring-point to the head of a pyramid formed of three cables, the lower ends of which were secured to the points of an equilateral triangle of some 800 ft. side.
The height of the apex was arranged to be between 100 and 200 ft. in order that the downward component of the wires when resisting the wind force should not be excessive. A considerable weight of wire was, however, necessarily supported by the ship, and a large amount of static lift was therefore necessary. This system gave considerable success during 1918, but was found defective in gusty winds owing to the liability of one wire going slack under the influ- ence of side gusts. A wind along the axis of the ship produces a certain amount of dynamic lift which balances the downward com- ponent due to the tension in the wire. The force caused by a side- ways gust produces no corresponding increase of dynamic lift, and
