landing at East Fortune,Scotland in bright sunshine, showing
the distinctive tri-lobe envelope design, and tail fin configuration
a replacement for C.23, landing with the help of a ground
handling party. C.23A was the last Coastal Class airship
up of the Coastal C.9 car which was based at RNAS Mullion
in Cornwall. Notice earlier two bladed propellor have been
replaced by 4 bladed, and then balloonet airscoop has been
moved behind the rear engine to avoid obscuring the view of
the crew as had been laid out on earlier configurations.
C.19 launching from in front of the metal shed at RNAS Kingsnorth.
Class C.46 on submarine and mine scouting patrol following
Class on scouting patrol following a destroyer.
and Sails" by reknowned artist Barry Barnes, depicting
a Coastal Class airship alongside a sailing schoner under
full sail. (AHT Collection)
loss of the C.23A at sea" A watercolour paining showing
the last moments of the last Coastal, C.23A lost at sea on
10th August 1918. Artist unknown but possibly one of the crew
members (A Lawson Collection)
the annotation noting the C.21 was "attacked by
a German Submarine", the damage was caused when
ship when leaving the ground for patrol. None of the crew
in the old girl yet"
spot of dismantling"
to bed" despite the ground crew handling the ship into
the Capel Coastal shed, the gondola was damaged beyond repair
and the ship deleted after 831 hours' flying.
being walked out of the Coastal shed at Pulham. The windbreaks
on either side of the shed caused eddies and made ground
handling very challenging.
open cockpit for the crew positions. Seen here are the navigator
position, the WT operator and rear engineer.
crew of C.25 adapted the cockpit with an enclosed canopy
for protection against nst the elements. This was the only
example of a Coastal ship converted in this way.
rare captured image of the C.27 envelope on fire after being
attacked on 11th December 1917. Only one of two ships lost
to enemy action.
Launching from the RNAS Longside Coastal shed. Notice the
more elongated tail behind the control fins, compared to
a Coastal Class ship envelope.
Coastal Star class airship with more elongated envelope.
close up of the C*1 enclosed gondola, taken from the C.12
ship. Notice the additional viewing portholes and engine
configuration with engines at both ends of the gondola.
Class and C * Class
As the war progressed, and
the designs of the raiding Zeppelins improve, so did the design
and performance of the British Coastal defense airships.
The SS Class
ships had proved not only a deferent and protection for submarines,
but they could also engage the enemy threat as well. A larger
ship was therefore required with a bigger bomb load, and longer
The Coastal Class
The urgent need for a non-rigid
airship to carry out antisubmarine patrol having been satisfied
for the time with the production of the S.S. B.E. 2C type, the
airship designers of the Royal Naval Air Service turned their
attention to the production of an airship which would have greater
lift and speed than the S.S. type, and, consequently, an augmented
radius of action, together with a higher degree of reliability.
As the name "Coastal" or "Coast Patrol" implies,
this ship was intended to carry out extended sea patrols within
the vicinity of the coastline of the British Isles and main shipping
lanes. With the losses to shipping convoys accelerating, by the
summer of 1915 this need was becoming very pressing.The German
U-boat force had primarily based itself in the port of Ostend
in Belgium, giving the submarines better access to the sea lanes
both the English Channel and up in to the North Sea, and therefore
all around England.
The German Navy made use of
this advantage, sending out a feet of nearly 20 U-boats to begin
the naval blockade. In January 1915, before the declaration of
"unrestricted submarine warfare" as the submarine blockade
was called, 43,550 tonnes of shipping had been sunk by U-boats.
The number of sinkings then
steadily increased, with 168,200 tonnes of shipping being lost
in August 1915. Attacking without warning, German U-boats sank
nearly 100,000 GRT per month, an average of 1.9 ships daily
The design for a new ship
fell on to the design team based at RNAS
Kingsnorth who were sent with instructions from the Admiralty
to create a new design of ship, but with use of existing equipment.
Using a French Astra Torres
ungainly looking tri-lobed envelope and based on the French design,
a new larger scouting ship was required to have a longer duration
and heavier bomb load. Design and advancement on the envelope
also progressed with an unusual Tri-lobe design. The
Admiralty had already acquired two Astra Torres ships after the
outbreak of the war. The first ship was originally designated
No.8, and was commanded at various times by Commander Hinks and
by Commander Usbourne. The No. 8 had an uneventful career before
being deleted in May 1916. The second ship, was commissioned in
early 1915, had been designated as No.10 and was almost immediately
dismantled in order to serve as the basis of the new design, and
her component parts were extensively modified in course of preparation.
This was seen as a stronger,
more aerodynamic. Again, the use of existing technology was used
to keep the costs down and production speeds up with demand. The
gondola was based on two tail-less Avro shortened aeroplane fuselages
connected end to end, and carried 2 engines in tandem. This produced
a four or five seater car, depending on configuration or comfort
of the crew.
The Tri-lobe envelope was 196 feet long and a capacity of 170,000
cft. The ridges in the envelope was connected to fabric curtains
inserted to help maintain the shape. Four ballonets were also
fitted, two in each of the lower lobes, and a single scoop consisting
of a single sheet of aluminum tube of oval cross section reached
down towards the forward propellor. Later versions of the ship
had the scoop at the rear propellor. Single skids replaced the
normal undercarriage and also protected the propellers. The rigging
was also the same type as seen in an existing Astra Torres ship.
The Coastals were fitted with
a larger bomb load than their predecessor ships, the SST class
ship, also a wireless, and 2 machine guns, one of which situated
on a small platform on the on top of the envelope. This gun positions
was accessed by a tube and rope ladder from the gondola up inside
the envelope and out through the top. The pressure of the gas
was firm enough to hold a platform gun and gunner. Sometimes commented
as the "ugliest" dirigibles ever made, these ships were
reported by the crews as erratic and unstable in flight. The responsiveness
in the controls was sluggish and often caused the crew to be airsick.
However one of the main advances in airship technology was the
very high rate of climb which the Coastals managed to provide.
Before the advent of later
and more reliable ships, the bulk of anti-submarine patrol on
the east coast and south-west coast of England was maintained
by the Coastal class ship, in protecting the convoys and signaling
On the east coast of England, with the prevailing westerly and
southwesterly winds, these airships had many long and arduous
voyages on their return from patrol, and in the bitterness of
winter their difficulties were increased ten-fold. To the wholehearted
efforts of Coastal pilots and crews is due, to a great extent,
the recognition which somewhat tardily was granted to the Airship
The shape of the envelope
is not all that could have been desired, for it is by no means
a true streamline, but has the same cross section for the greater
part of its length, which tapers at either end to a point which
is slightly more accentuated aft. Owing to the shape, these ships,
in the early days until experience had been gained, were extremely
difficult to handle, both on the landing ground and also in the
air. They were extremely unstable both in a vertical and horizontal
plane, and were slow in answering to their rudders and elevators.
This was to be later rectified in the C* (Coastal Star) class
The envelope was composed
of rubber-proofed fabric doped to hold the gas and resist the
effects of weather. Four ballonets were situated in the envelope,
two in each of the lower lobes, air being conveyed to them by
means of a fabric air duct, which was parallel to the longitudinal
centre line of the envelope, with transverse ducts connecting
each pair of ballonets. In earlier types of the Coastal, the air
scoop supplying air to the air duct was fitted in the slip stream
of the forward engine, but later this was fitted aft of the after
Six valves in all were used,
four air valves, one fitted to each ballonet, and two gas valves.
These were situated well aft, one to each of the lower lobes,
and fitted on either side of the rudder plane. A top valve is
dispensed with because in practice when an Astra-Torres envelope
loses shape, the tendency is for the tail to be pulled upwards
by the rigging, with the result that the two gas valves always
and covers, so called for their shape resembled fisherman's crabpots,
and non-return valves are employed in a similar manner to S.S.
Astra-Torres Envelope and Rigging System
The Astra-Torres system of
internal rigging is described in some detail as follows. The envelope
is made up of three longitudinal lobes, one above and two below,
which when viewed end on gives it a trefoil appearance. The internal
rigging is attached to the ridges formed on either side of the
upper lobe, where it meets the two side lobes. From here it forms
a V, when viewed cross sectionally, converging at he ridge formed
by the two lobes on the underside of the envelope which is known
as the lower ridge.
To the whole length of the
top ridges are attached the internal rigging girdles and also
the lacing girdles to which are secured the top and side curtains.
These curtains are composed of ordinary unproofed fabric and their
object is to make the envelope keep its trilobe shape. They do
not, however, divide the ship into separate gas compartments.
The rigging girdle consists of a number of fabric scallops through
which run strands of Italian hemp. These strands, of which there
are a large number, are led towards the bottom ridge, where they
are drawn together and secured to a rigging sector. To these sectors
the main external rigging cables are attached. The diagram shows
better than any description this rigging system.
Ten main suspensions are incorporated
in the Coastal envelope, of which three take the handling guys,
the remaining seven support the weight of the car.
The horizontal fins with the
elevator flaps, and the vertical fin with the rudder flap, are
fixed to the ridges of the envelope.
The car was evolved in the
first instance by cutting away the tail portion of two Avro seaplane
fuselages and joining the forward portions end on, the resulting
car, therefore, had engines at either end with seating accommodation
for four. The landing chassis were altered, single skids being
substituted for the wider landing chassis employed in the seaplane.
The car consists of four longerons with struts vertical and cross,
and stiffened with vertical and cross bracing wires. The sides
are covered with fabric and the flooring and fairing on the top
of the car are composed of three-ply wood. In the later cars five
seats were provided to enable a second officer to be carried.
The engines are mounted on
bearers at each end of the car, and the petrol and oil tanks were
originally placed adjoining the engines in the car. Various engines
were used on the Coastal class. The most common configuration
was two water-cooled Sunbeam engines, producing 150 hp each. Some
replaced the aft unit with a Renault engine of 220 hp (164 kW),
and various airships were deployed with a 100 hp Berliet engine
in the front position. The former change was usually an attempt
to improve the Coastals' leisurely top speed, whilst the latter
was an attempt to improve reliability over the Sunbeam units,
which had short lives when required to run at full speed for hours
at a time in the long patrols undertaken by the airships.
A 1.5 horsepower (1.1 kW)
ABC engine was mounted in the gondola. This drove a dynamo to
power the radio and, if needed, an auxiliary ballonet blower
At a later date various methods
of carrying the petrol tanks were adopted, in some cases they
were slung from the envelope and in others mounted on bearers
above the engines.
Wireless telegraphy is fitted
as is the case with all airships. In the Coastal a gun is mounted
on the top of the envelope, which is reached by a climbing shaft
passing through the envelope, another mounting being provided
on the car itself.
Bombs are also carried on
frames attached to the car. Sunbeam engines originally supplied
the motive power, but at a later date a 220 horse-power Renault
was fitted aft and a 100 horse-power, Berliet forward. With the
greater engine power the ship's capabilities were considerably
Exceedingly long flights were
achieved by this type of ship, and those exceeding ten hours are
far too numerous to mention. The moot noteworthy of all gave a
total of 24 1/4 hours, which, at the time, had only once been
surpassed by any British airship.
Launched in to Service: The
The prototype ship, classed
as C.1 entered undertook a first flight from RNAS Kingsnorth on
26th May 1915, which was to be applauded for the design team to
come up with a flying prototype to the new specification in such
a short time period.When she was brought out of her shed, it was
seen that the C.1 initially had a yellow envelope that was not
doped (or at least not doped in the same manner as other non-rigids).
No details of the first flight
were recorded in the Daily Report for the Kingsnorth Station,
however it was commented that the ship was unstable fore and aft
owing to the original small Astra Torres horizontal fins which
were fitted to the original envelope. A second flight was made
on 31st May 1915, again no flight details were recorded in the
Daily Report, however the comment was made that "at
nearly hull (full) speed, nose of envelope blew in. More nose
stiffeners added later"
The C.1 was little used for
the rest of the year, one flight in June, two in July, one in
August and two in September, with various modifications being
made between each flight. After the last flight in September 1915,
the C.1 was laid up until January 1916.
On 16th January 1916, the
C.1 was handed over for further evaluation. The C.1 passed the
initial tests and by the end of January completed her trials,
and certification, leading to further orders being based on the
same simple design to follow. The C.1 was launched with twin bladed
propellors and as in later designs, this was changed to 4 bladed,
along with further design changes.
After the trials, it was considered
that the range could be extended by the possibility of refueling
at sea, which would reduce the need to return to base, but also
extend the patrol range. During the spring of 1916, C.1 was involved
in experiments on 12th May, with being towed by the light cruiser
HMS Carysforth out of Harwich, and then by HMS Canterbury.
This was repeated again with success on May 16th, under the direction
of Commodore R. Y. Tyrwhitt. The C.1 under took the experiment
again with HMS Canterbury on 6th September 1916.
After many practice attempts,
it became possible for the airships trail rope to be picked up
at some 26 knots before speed reduced to 12 knots to allow the
ship to be pulled down safely within 100 feet of the cruisers
decks. From being in this "tow" position, a bosun's
chair could be lowered with a member of the crew, to the deck,
and a replacement crew member could be winched up to the airship.
The ship could be refueled by pumping of petrol up by compressed
air at a rate of 60 gallons in eight minutes.
Despite the success of the
practice crew change and offshore refueling, these techniques
were not widely used, but were in occasion enabled the Coastal
Airships to accompany the Grand Fleet as scouts out of their existing
The C.1 was active during
trials in 1916, and active again in 1917, but was laid up in February
1917 and not used again being deleted in June 1918 with only 90
hours flying time recorded.
life of Coastal C.2
The record of one of these
ships so deleted is surely worthy of special mention. Being first
commissioned on 28th January 1916 she was in commission for 2
years 75 days, with hours flown of 2,273
hours, and averaged for each day of this period 3 hours
6 minutes flying. During this time she covered upwards of 66,000
miles. The ship was finally deleted from service in October of
1919, from this it will be seen that she did not pass her life
by any means in idleness.
C.9 - Most Successful Service Life
The most successful ship in
this class was the C.9 which flew from RNAS
Mullion in Cornwall. The ship had a service flying life of
2,500 hours 11 minutes, some 68,201 miles, before being deleted
from the active list on 1st October 1918. The C.9 patrolled the
English Channel in all weathers and was often risky flown without
ballast, in order to carry more fuel and bomb load. The C.9 was
involved in many dramatic incidents and on several occasions successfully
attacked German U-Boats.
C.24 - Longest Flight
The longest single flight
recorded by a Coastal ship was 24 hours 15 minutes by C24 on 9th
10th July 1917
C.21 - Accidents do happen
the annotation noting the C.21 was attacked by a German Submarine,
the damage was caused by the ship when leaving the ground for
patrol. On 1 June 1918, when launching, the forward handling guys
hit the roof of a small hut and where whipped up in to the forward
engine's propellor, causing a rent around 4ft long in the balloonet
and a rent of 2ft long in the envelope.
The pilot immediately opened up the aft engine and turned back
to the aerodrome at Folkstone, with the idea of landing as soon
as possible. The airship managed to return to base at Folkstone
but the loss of gas caused the envelope to collapse. The photos
on the side of the page were captured in trying to get the damaged
ship in to the shed.
car was damaged beyond repair and the ship deleted after 831 hours'
flying. Despite the ship having been on the station at Folkstone
since February 1918, the C 21 had not been that successful on
operations and had absorbed far more manpower than she was worth.
After this accident, it was decided that the Capel / Folkstone
RNAS base was to only run SS-Zero patrol airships.
Production of this class
of ship ceased in 1916.
Only 2 were destroyed through
enemy action in the entire war. In total 35 Coastal
Class ships were built, however 12 were totally destroyed in some
manner and only 4 survived to the Armistice.
Four Coastal Class ships (C.a-d)
were sold to Russia in 1916, and one Coastal ship, the former
C.4 was sold to the French Government.
Due to the size and often
instability when landing or taking off, and often the inexperience
of the ground handling crew for handling a larger airship than
the smaller Submarine Scout class ships, many of the Coastal Class
ships were accidentally lost.
due to Enemy Action
Of all of the British airships
produced during the First World War, two were destroyed due to
enemy action during the entire war. Both of these losses were
Coastals, the C.17 and C.27.
On 21st April, 1917 Coastal
C.17 was captained by Sub-Lieutenant E.G.O. Jackson was was patrolling
the Straits of Dover. The C.17 was engaged and then attacked by
German aeroplanes. Despite fighting back using her machine guns,
the airship stood no chance as was shot down within sight of several
trawlers. Tragically all crew members were lost.
On 11th December 1917, Coastal
C.27 commanded by Flight Lieutennant Dixon was shot down in similar
circumstances as the C.17 enagement, this time being attacked
by two Hansa-Brandenburg seaplanes, flying from their base on
the other side of the English Channel from Zebrugge.
Both were shot down by German
aeroplanes when they strayed too close to enemy-occupied territory.
In both times, there were no survivors of the crew. It was unusual
for these losses to occur to enemy action, as airships were normally
safe from air attack, as they usually flew beyond the range of
land based aircraft. and no zeppelins were ever sent to intercept
Towards the end of 1917, these
ships, having been in commission for over two years, were in many
cases in need of a complete refit. Several were put in order,
but it was decided that this policy should not be continued, and
that as each ship was no longer fit for flying it should be replaced
by the more modern Coastal known as the C Star.
The RNAS Kingsnorth design
team took upon themselves to correct the earlier design problems
encountered with the Coastal class ship, and the crew feedback
regarding the instability of the ship on takeoff and landing.
In changing the control surfaces and making a more streamlined
tail to the envelope, these stability problems were corrected.
The second class of Coastal
were designated the C* (C Star) Class. Due to the
technical problems which were being encountered at RNAS Kingsnorth
with the development of the larger North Sea Class ships, it was
decided that an interim class of ship was needed. With this saw
the improvement of the Coastal Class ship, and the development
of the C Star airship class.
The control car of the C* class ship was similar to that of the
existing Coastal Class ship, and indeed the prototype C* ship
took the existing control car from the C.12. The C* ships retained
the open cockpits but extended engine mounts were put at the rear,
and the body was covered with plywood instead of fabric. In order
to improve observation, four circular portholes of Triplex glass
were provided for on either side of the car, and another placed
on the floor of the pilots compartment. The feedback from the
crews on the Coastal Class ship were incorporated in improving
of the overall comfort of the car for the crew.
The main alteration, which
was more recognizable was the change to the envelope. The common
Astra Torres trilobe form was retained, but the length was increased
to 207 feet and increasing the capacity to 210,000cft. The shape
of the envelope became much more streamlined and graceful compared
to the original Coastal Class envelope. This was a development
project, and so the first three ships of the C* Class still had
rather a blunt stern tip.
The later ships had more of
a slender tail with increasing the length of the tail by another
10ft, but without adding to the overall capacity. To improve control,
and stability, six balloonets were fitted, two large one amidships,
two smaller once forward and another two aft. Each pair was connected
by a tube., while the three starboard balloonets were further
interconnected by the air delivery duct, which lead from the airscoop
positioned to collect air from the slipstream of the after engine.
The duct was fitted externally at first but was later placed inside
the envelope in order to improve streamlining.
The Coastal "Star"
class ship enjoyed more powerful and reliable engines, with the
aft engine being changed to 220hp water cooled Renault engine,
whilst the forward engine was a 110hp water cooled Berliet engine.
On later models the Renault engine was replaced by a water cooled
240hp Fiat engine. Unlike the Coastal Class ships, there was no
gunner position on the top of the envelope, so this saved some
250lb in weight, and allowed a gas release valve to be placed
in the same position, but a pair of Lewis guns were carried in
the control car, which also had fittings for two 230lb and two
100lb bombs. For the crew, five parachutes were also carried,
the lines of which could be attached quickly to a harness worn
at all times by each crew member.
Although the rate of climb
on a C* ship, was not as fast as a Coastal class ship, the new
ships proved to be superior in every other way and capable of
a top speed of 56mph.
10 C * airships were completed
and put in to operation, however they were not regarded as entirely
successful as 20 were originally ordered, and production at RNAS
Kingsnorth was discontinued in favour of the SS Twin Sea Scout
airship, after the first 10 had been delivered between February
to July 1918.
The C* airships had rather
uneventful careers compared to those of the Coastal Class ships,
as they came late in on to the scene of the war, and all carried
out long and regular patrols carrying out their duties efficiently
without incident. The longest continuous flight recorded was of
34 hours and 30 minutes by C84 commanded by Captain Cleary on
27th to 28th May 1918.
Launching and Flying Ambulances
A project came under discussion
in the latter part of the war, and to better hunt the submarine
threat, was to equip all the C* airships with torpedoes. As the
enemy submarines frequently submerged no further than periscope
depth, with was decided to experiment with launching circling
torpedoes, designed to be run in descending spirals, before finding
the target. The end of the war prevented the plan from being furthered.
A second proposal was the modification of the C* design and due
to it's extended range, was to use the ships as flying ambulances.
The idea being that the airship would have brought urgent medical
cases from the Western Front, directly to England, escorted with
aeroplanes. Again the proposal made in January 1918, was never
fully investigated or implemented.
of the series
The Coastal airship played
no small part in the defeat of the submarine, but its task was
onerous and the enemy and the elements unfortunately exacted a
heavy toll. A German wireless message received in this country
testified to the valiant manner in which one of these ships met
with destruction. Despite being rushed in to production, having
to fulfill a role which was unprepared, they gave valuable experience
to design teams, ground crews and flight crews during testing
times of war. It cannot be ignored that the Coastal Class ship
was designed at a time of severe pressure during the war, and
can be seen as a jump from the previous Submarine Scout class,
and therefore very well conceived. The losses of the Coastal class
ship, seemingly more than any other class of ship, needs to be
seen as a combination of a fair share of disasters, caused by
combinations of inexperience, and some genuine and often overlooked
bad luck. Operational difficulties can also be linked with the
conditions in which the crews were put to work, with very bad
weather over the North Sea and Western Approaches. It has to be
applauded that these workhorses were the only airships available
to protect the East Coast commercial shipping for the whole of
1916 and the most of 1917. Despite the losses and accidents many
of the ships were often reused and became redeveloped in to the
new class of Coastal Star ship.
The improvements lead to the
redesign of and development of the C* ships, and the record of
the C* ships were quite extraordinary in comparison, as none caught
fire, was wrecked, lost at sea or destroyed in any way. From the
logs, none appear to have been destroyed in any way or noteworthy
incident, and all were still active at the time of the Armistice,
with all 10 ships being deleted in October of 1919.