Following the trials and design success of HMA No. 9, it was agreed that the Zeppelin threat had to be tackled head on; the Admiralty required more ships. There were initial problems at the Admiralty with regards to change of staff and also general opinion regarding rigid airships, as the successful non-rigid programme was expanding rapidly. However in June of 1915, along with the Vickers Company, three new contractors were selected to produce rigid ships.

The three new contractors were Beardmore, Armstrong and Whitworth and finally Shorts Brothers. All three companies were to become famous in the world of aviation.

By October 1915 the drawings were approved and three ships were ordered. By December the pace of design and the requirement for big ships had increased dramatically and a further sixteen ships had been budgeted for by the Admiralty. All of these ships were to become known as the 23 Class, which were in effect stretched versions of the original No. 9. The designs were seen in essence as modified versions of No.9, with an extra bay inserted in the middle of the ship. A gun platform was added to the top of the ship designed to take a two pound gun and two Lewis machine guns. The platform was surrounded by 18 inch sanctions carrying lifelines. These sanctions could be extended to double the height in order to carry a canvas windscreen. Three other Lewis guns were to be fitted at the extreme tail, in the control car further aft and on the top walking way.

The bomb load was to be greater than that of HMA 9 but none was actually specified. The ships each possessed an external keel, to the same pattern as the No. 9. The cabin being 45 feet long contain crew accommodation, a wireless room and a bomb room. From the keel further aft were three gondolas which were suspended below and accessible by open ladders. The ship gondolas also contained airtight buoyancy bags in case the ships had to alight on water. This was a technical requirement of all ships since HMA 1 - the Mayfly. With this rapid expansion of the requirement for airship production, there were a few problems in that so far, only one company had actually built a ship and hence had all the facilities.


H.M.A 24 - at Glasgow construction site of Beardmore

In April 1916 the Government approved for a total fleet of 10, 23 class ships, but this was later modified in the light of further design technology available from Germany. The later ships becoming the R23X class and the R31 class.

The HMA 23 was the first to be completed, and hence the designation of the class of ships. There were a number of delays in the initial constructions and the ship was completed on 26th August 1917. Although not unexpected, the figures were disappointing and 2 weeks later on the 18th October the Admiralty decided that the design must be altered.

On the day of the decision the HMA 24 was also tested and found to be mysteriously two thirds of a ton heavier than her sister ships, with a lift of only 5.1 tons. The alterations to the ships included the removal of dynamos and bomb frames and many other items which were deemed not necessary were removed. Upon inspection of No. 24 it was later found that the ship was heavier due to having used rivets, fastenings and bracing pieces which were slightly larger and heavier than originally expected and hence increased the overall weight of the ship.

No 24 required more than minor modifications, since she was so much heavier than the other ships. As Beardmore's shed was needed immediately for the building of R.34, it was necessary to move the ship to her new station at East Fortune as soon as possible. This required extra lift to enable her to fly safely over the hilly countryside of southern Scotland, so in addition to the changes already made, the drastic step was taken of removing all the machinery from the aft car: engine, propeller, radiator and silencers. All these modifications brought the disposable lift up to nearly 6.5 tons, but the price paid was a top speed barely in excess of 35 mph. In this form No 24 was delivered in October 1917.

No. 24 had a similar history to that of No. 23, flying a total of 164 hours and 40 minutes and covering 4,200 miles, but as the original intention of replacing her missing engine in a new and lighter car was never carried out, she remained very slow.

On one typical occasion, encountering an unexpectedly strong adverse wind near the Bass Rock, she remained for some time stationary, quite unable to make any headway. Despite this severe handicap she was used for training and convoy duties when conditions were deemed suitable, although she appears to have seen no action. She made her last wartime flight in June 1918, but was retained in service and two months later had her bows strengthened to adapt her for mooring trials at Pulham, where Vickers were building a new type of high mast.

The tests, which were carried out with both midship engines removed, were quite successful but were not completed finally until November 1919. The following month No 24 was deleted and scrapped.