Home - Articles - Development - Snorting in the RN

Snorting in the Royal Navy, 1945 onwards

Compiled by Peter D Hulme

Message to author from Jeff Tall, Commander OBE, Royal Navy (ret)
A former SSK, SSN and SSBN Commander

At times snorting was as uncomfortable in a 'P' or 'O' as for your 'A'; however we seemed to get the amps in by hook or by crook without surfacing. A minimum of 15 minutes was required to make up for the preparation, but once that was made up then we were in profit. Improvements to charging rates and battery efficiencies may also have contributed to conduct the whole thing dived. I believe we fulfilled the dream of Dutch submariners who invented the Snorkel rather than any great influence of the Type XXI.


These notes focus on the Amphion Class submarine because so much data is available from the book by Lambert and Hill 'The Submarine Alliance' and the author, though with no claims to having knowledge in great depth, did spend several years in the motor rooms of snorting submarines, mainly on Amphion Class. The intention has been to use the available data and present a basic picture of how the dream of the Dutch Submariners, mentioned by Commander Tall, was achieved by snort conversion of Royal Navy submarines from end of WWII through to the later submarines designed and built with snort in mind.

In this article I have focused on snorting the Royal Navy, however there is a complimentary article Snorkel in the US Navy - 1945 onwards

While every attempt has been to be accurate there are no doubt certain aspects that would benefit from the experience of others, all comments welcome
Peter D Hulme


Extract from SUBMARINE ADMIRAL by Admiral Galatin US Navy (ret) Page 123

The Dutch invented the snorkel and used it for battery charging and ventilation of the boat. It was the spring of 1938 that I saw my first snorkel, in Pearl Harbour on board a Royal Netherlands navy sub of their 'O' class en route to the Netherlands East Indies.

Here are some notes about snorting during and post WWII that give a feel for the background.

The Dutch Navy fitted snort to two submarines O-19 and O-20, before WWII, these submarines were captured by the invading German forces. The O-21 had not completed trials when forced to flee to the UK where it is reported the Royal Navy showed felt the dangers outweighed the advantages and the snorchell equipment was removed before the submarine joined the Allied submarine forces.

The US Navy determined there was little to be gained in the Pacific war by fitting Snorkel. Admiral I J Galatin in the Prologue to SUBMARINE DIARY, Rear Admiral Corwin Mendenhall US Navy (retired).

It is likely Germany was well aware of the Dutch development as the Germans, to avoid Treaty restrictions, had a covert submarine design office in Holland prior to WWII, registered as NV Ingenieurskantoor voor Scheepsbouw but apparently the concept was not considered to be of any benefit to the U-Boats then successfully engaged in the initial stages of the Battle of the Atlantic, making their long transits to the battle on the surface largely unimpeded and making most of their attacks on the surface at night largely undetected by the escorts.

However, as is well known, the balance of the battle tipped against the U-Boats in 1943 with the growth and success of the Allied ASW forces, in particular the sudden attacks by wide ranging ASW aircraft. This led to the belated adoption of Schnorchel as a solution, but one with a price, slower transits between the bases and the convoy routes, with more attacks having to be made submerged, limited by speed and battery capacity. The first Schnorchel U-boat was U-58 in August 1943, but by June 1944 only about half the U-Boats operating out of the French bases were fitted with Schnorchel

In the closing months of the war when US Navy and Royal Navy submarines no longer had a critical role to play in the final defeat of Japan, both Navies decided the post war future was essentially with snort and successful trial conversions were made with HMS Truant and USS Irex.

There is little doubt both Navies were impressed by the success of the snorting U-Boats under difficult circumstances, but perhaps more importantly by the decision of the Germans to produce a fast battery submarine where snorting was an essential part of the overall design concept. The famous XXI that did not fire a shot in anger, but in the case of U-2511 did make an undetected simulated attack on HMS Norfolk shortly after receiving the ceasefire signal and the much smaller XXIII, that actually achieved success as the war came to a close with U-2336 reported to have sunk the last merchant ship of the war and returned undetected to Germany to surrender after a 14 day patrol.


The thinking of the Royal Navy is clearly indicated in this quote from The Staff Draft Requirements for the conversions of Royal Navy T Class into fast submerged submarines (FOSM letter, 546/SM.472 20th May 1948)

A fully operational submarine with maximum possible submerged speed and endurance, capable of carrying out a war patrol continuously submerged.

This additional historical note is an extract from the Engineering Section of a "Technical Staff Monograph on Submarines as a Weapon," prepared by Flag Officer, Submarines.


An early project to fit Snort in a U Class boat for experiment in 1942-3 was cancelled before the design was complete.

In 1944, Truant was fitted with Snort arrangements for trials, crew training and A/S training. The outcome of the experiment of this equipment is embodied in the Admiralty specification for Snort in S Class, T Class and A Class submarines.

This arrangement was evolved after a study of captured German documentsand material, and was remarkably satisfactory in that very little trouble was experienced during development and trial.

The Staff requirements included a submerged speed of not less than 5.75 knots.

Clearly snorting was to become a major feature of Royal Navy diesel submarine operations and as we will see, not just the eight T Class converted for higher submerged speed referred to above, but all the three main classes as described in Diesel Submarines 1948-1958, photographs of the submarines may seen with and without snort equipment fitted, including the Truant mentioned below.


The T Class submarine Truant is usually reported to have been the first fitted with a trial version of snort (Truant Log 1945), however some references state that early experiments used an Royal Navy U Class submarine, but it is likely this a confusion with reported detection exercises with a dummy snort fitted to a Royal Navy U Class as a target for escorts. Regardless the Royal Navy by 1948 had numerous submarines in service with the capability of snorting for sustained periods.

The folding mast was seen as the most practical option to convert an existing submarine with a standard WWII type conning tower. Unlike the WWII German U-Boats, the Royal Navy chose to fold onto the after casing.

Royal Navy snort conversion was confined to the Amphion Class, T Class and S Class diesel submarines as described in Diesel Submarines 1948-1958. All three conversions were basically similar; hence little will be lost by focusing this article on the Amphion Class. Later classes were of course designed and built with snort fitted.


The book by Lambert and Hill 'The Submarine Alliance' has been a valuable resource as it contains the reports on the early trial snorting cruises and detailed drawings of the Amphion Class arrangements. All taken from official sources.


It is self evident that the air induction mast with its float operated valve head and open exhaust masts, are the critical additional components to equip any submarine for snorting and the system used by the Royal Navy is not surprisingly, basically similar to the U-Boat. However it should noted that the float valve system was not adopted by the US Navy. Their snort head valve was opened or closed by a high pressure air system and while snorting was controlled by sea water detector electrodes on the head of the mast that determines when the head valve inlet has submerged. This again is reported to have been a U-Boat development, though apparently not widely used in WWII. It may well have been the system on the XXI U-Boat?



The Alliance book states that a combined snort induction and exhaust mast were fitted during building, 1947-1949 to Aurochs, Alliance, Ambush, Andrew, Artful, Acheron, and so fitted after completion was Aeneas. Two early photographs have been located showing this arrangement on an Amphion Class. The rest of this class were progressively fitted out and the author's opinion from observation at the time, was all were fitted before 1950.

A rare photograph of HMS Aurochs (P426) clearly showing both Snort and Bandstand
A rare photograph of HMS Aurochs (P426) clearly showing both Snort and Bandstand
Another rare photograph. This one showing of HMS Ambush (P418) with both Snort and Bandstand aft  of the fin
Another rare photograph. This one showing of HMS Ambush (P418) with both Snort and Bandstand aft of the fin

It is also shown in a outline drawing that in 1947 Ambush, Alliance and Anchorite were completed with the twin Oerlikon mounted in a railed 'Bandstand'. aft of the conning tower. Note the comments below on the extended snort cruises of the Alliance and Ambush .

This combined snort mast system was similar to that fitted and retained on the unconverted T Class and the S Class throughout their service lives, see Diesel Submarines 1948-1958 and the photograph shown as Fig 1

However on the combined induction/exhaust arrangement was replaced on the Amphion Class by a separate exhaust trunking firmly fixed to the ANF radar mast so few, if any were unmodified by 1949. This modification can be seen in Amphion Class photographs from about 1949 onwards Diesel Submarines 1948-1958. It is assumed that any boats still fitted with AA gun 'Bandstands' were removed at this time and the space so created below the casing by the removal of the gun mount welded to the pressure hull would be used by the new exhaust trunking leading up the trunking fixed to the periscope standards,

This was a modification; no vessels were known to have been completed in this form.

There are no technical documents available (to the author) concerning this change, but it should noted the Amphion Class engines were significantly larger than the T Class or S Class and this change would allow the separate induction to be of larger bore to enable a greater air flow. In addition the larger bore would allow faster stabilisation of the atmosphere of the submarine after an unintended vacuum had been pulled by the head valve closing due to temporary submersion.

It will also be noted that the larger pressure hull of the Amphion Class would have a greater air volume than the T Class and S Class. How significant this may have been is not known as no attempt has been made locate any Directorate of Naval Construction design documents that may be archived at the TNA.

It is not known if the Alliance was retrofitted with separated Induction/Exhaust as above and the Oerlikon 'Bandstand' removed, before going on the extended Tropical Cruise in November 1947. The same applies to the Ambush and its extended Arctic Cruise in 1948. It has not yet been possible to clarify this important point in this research into snorting in the RN, however the Alliance was completed May 1947 and sailed October 1947, while Ambush was completed July 1947 and sailed Feb 1948. Bill Dalton had a web site recording his time on Ambush during the Arctic cruise, one photograph now filed, looking aft shows the snow covered rails of the Bandstand, the gun if fitted would be out of sight. The Alliance book contains a general description of both cruises.

It should noted that prior to these long snort cruises, Taciturn has previously carried out long snorting cruise in temperate waters and would be fitted with usual T Class combined induction.exhaust snort mast, the author has not seen any reports on this cruise.

A ring float induction head valve was apparently intended to be fitted to all Amphion Class from 1949, perhaps as a result of the experiences of the Ambush 's Arctic cruise in 1948 where severe icing of the older style float valve was experienced. The Alliance book shows a detailed drawing with the ring float inside a beehive shaped snort head and electrically heated.

However this was not a rapidly implemented programme as the author has photographs of the Amphion when serving aboard as the Electrician up until 1955 and the old external float head is shown still fitted despite having had a full refit in 1953. Photographs in The Alliance book shows some streamlined Amphion Class submarines with a later spherical snort head attached to the fold down induction masts.

This short historical review is a merely a guide to the main technical article describing the various snorting features as they were fitted to RN submarines including the last major fleet submarine, the 'O' class. No data is available for the short lived RN Upholder Class, now in Canadian service.


For copies of full official drawing detail of the main components of the masts see The Alliance book.

The separate induction mast topped by its float operated valve, was of a streamlined shape with a internal strengthening plate running the full length of the 28 ft mast dividing the mast into a fore and aft pipes, however the plate was perforated with substantial holes to reduce the weight and perhaps equalise the flow. Text from The Alliance book. However in 1951 this was not the type of mast design fitted to some, if not all Amphion Class as can be seen from the photograph that follows of the broken Affray mast.

I have studied the diagram of the snort head and lacking any official text, come to a conclusion about the quite sophisticated design that includes an additional valve labeled as a "Double Beat Valve" sealing an air chamber in the top of the head valve structure.

I believe this valve and an air chamber provided for the mast valve to open automatically if the submarine went deep from snorting with the induction mast still raised full of trapped air and liable to implode due the increasing external sea pressure. The opening of the mast valve vents the air and allows the mast to flood as would have been the case if the mast had been lowered and the float valve opened by a crutch on the casing.

I looked at the comprehensive "Training Notebook" published by the Canadian Navy about their British built 'O' class submarines with telescopic mast and a then modern style snort head. They only had this to say on this subject despite other topics getting detailed descriptions

Note. In case the mast is not flooded up before the S/M goes deep the head valve is so constructed that it will lose buoyancy at 120ft (keel depth), drop open and flood the mast.

I am afraid I have no diagram of the 'O' class snort head and can only speculate on what is meant by 'lose buoyancy'. Still it tends to confirm that all snort heads were designed to vent and flood an upright induction mast when going deep. Perhaps as this operation was entirely automatic, with no access by the crew while submerged, no expanded explanation was thought to be needed.

This is the fractured mast salvaged from the sunken HMS Affray by HMS Reclaim in 1951. This type of mast was fitted to other boats of the class
This is the fractured mast salvaged from the sunken HMS Affray by HMS Reclaim in 1951. This type of mast was fitted to other boats of the class

Fig 1

The original style snort head float valve can be clearly seen
The original style snort head float valve can be clearly seen

HMS Artemis photographed during a publicity shoot called 'Operation Snort', May 1950. The landmass in the distance is the Isle of Wight. Note the float on the snort head has fallen open. The monocular attack and the larger binocular. Note the snort exhaust on the after standard clearly visible by the partially raised snort mast. Partly concealed is the radar mast. The mast locking bracket can be seen behind the lower mast.

The officer on the left is Lt Kirkwood, the first Lt sadly lost on Affray in 1951 as the instructing officer. The rating is signalman Jeffs. The author was an Electricians Mate on Artemis at this time.

To the right is shown the snort valve and exhaust outlet fitted to the combined mast of an unknown T Class submarine. The flap on the exhaust appears to have been abandoned later.

The raising and lowering of the combined and later separate induction masts was by a hydraulic (telemotor) ram mechanism external to the pressure hull that was enclosed in a pressure 'container 'to prevent leaking telemotor oil giving away the position of the submarine. The position of the mast was shown on a mechanical indicator in the control room.

Located near the mast raising telemotor control in the control room was a hand wheel that through a rod and gearing system passing through the pressure hull, positioned a locking pin to hold the raised mast upright in the yoke welded to the conning tower.

At the base of the mast, the air flow was taken by twin shaped pipes from either side to be combined into a single larger pipe by the adjacent drum shaped water trap, fitted flat under the casing, outside the pressure hull. The connections between this larger pipe and the hull induction valve will be described later. It would not be unreasonable to speculate that the twin pipes bring the induction from base of the air induction mast were a legacy from the original combined mast that had similar twin pipes of necessity, one for air induction and one for exhaust. This remained the arrangement on the T Class and S Class.

The snort induction system was not designed to withstand full submerged pressure and when lowered was free flooding. On raising the mast with the submarine submerged at periscope depth, water had to be drained by two main snort drains, one to drain the mast and water trap and one to drain the hull induction valve dome space. These drains were led into the control room into a tundish with two viewing ports to allow a check to be made that all draining had stopped. The tundish drained into inboard 'R' tank.

As the mast was lowered on completion of snorting, external lever operated vents at the base of the mast for each of the twin pipe were automatically opened as the mast fully folded to allow the escape of entrapped air. The snort head float valve was held open by a pad piece welded to the casing.

There was apparently no locking device holding the mast down in the folded position, this is a little surprising as these submarines were often in bad weather that on the face of it, could lift the mast from it's deck crutch, remembering that surfaced, the folded mast would be largely drained of water.

As discussed earlier all induction masts were fitted with float operated valve that closed the induction head should the mast head go below the surface due to difficulty in maintaining snorting depth for any reason, usually the problem occurred in bad weather.

However the exhaust mast was open to the sea and the outlet was permanently placed a few feet below the surface at periscope depth, relying on the engine back pressure to prevent any flow of water into the engine.


The submarine pressure hull integrity has been key aspect of the diesel electric submarine design from the beginning. Yet the need to supply air to the engine and remove exhaust gases required substantial hull apertures when the submarine was on the surface running on its diesel engines. To provide pressure hull integrity when submerged at depth, substantial valves were needed to close the induction and exhaust apertures.

There are no drawings available (to the author) showing the fine detail of the T Class and S Class valve arrangement however there is every indication they were basically similar to the Amphion Class. The author's memory of T Class arrangements fails on this point.


The Line diagram in Fig 3 shows the air flow, valves and drains.

Before conversion to snort, on the surface, the induction air feeding the engines simply came from two open Bridge Induction Inlets that were combined into a single pipe before running under the casing, above the pressure hull joining the Hull Induction Valve and entering the pressure hull. Air also came down the open conning tower hatches.

The induction valve in Amphion Class submarines was a hydraulically operated hinged clapper type, located in the engine room in a high pressure dome on the pressure hull just above the engine control platform.

It has been suggested that this valve was only converted to hydraulic operation after the Affray disaster, but apart from anecdotal evidence to the contrary, the submarine was always at risk with the open induction air intakes on the bridge that quickly started to flood as the submarine dived to avoid attack and the author's view is that the valve was hydraulically operated prior to snort being fitted. As were the submarine's Main vents etc (see Appendix B).

The valve control was operated from the engine control platform. As the new 'P' and 'O' had a telemotor (hydraulic) closing control valve in the Control Room. It may well the Amphion Class had this easily implemented safety feature, added later.

It is reasonably assumed this hull valve or similar was also fitted in earlier submarines to seal the air induction entry through the pressure hull. The cost of obtaining detail drawings, if indeed available can not be justified when the detail of the Amphion Class is readily available.

On passing through the pressure hull via the Hull Induction Valve, the flow continued through the manual Emergency Flap Valve. In the 'P' & 'O' class the flap of this valve was designed to shut automatically on the passage of a full bore of water and I am advised that this was also the case with the Amphion Class. See APPENDIX, Item No 6.

From here the induction air fed through an open ended pipe into the engine room bilges, though it could be diverted into the main ventilation system to distribute fresh air throughout the submarine with the engines drawing in the stale compartment air mixed with fresh air. It should noted there was no direct connection to the engines and any water coming down the single induction piping ended up in the ER bilge.

In the 'P' & 'O' classes the induction terminated in an open topped tank in the Engine Room presumably connected to the main suction line to enable any water brought down with the induction air to be pumped by the Ballast Pump. This tank was a feature of the later Amphion Class streamline conversions.


The available, Royal Canadian Navy 'O' class simplified exhaust diagram Fig 2 is adequate to show the Amphion Class exhaust system before and after the installation of snort. Using an 'O' drawing also serves to show that basically little changed even though snort was part of the original design of the 'P' & 'O' classes.

Fig 2 - P & O Engine Exhaust Systems

1. Group Exhaust (Hull Valve)
2. Surface Muffler Valve
3. Muffler Lock
4. Muffler Tank
5. Vent Pipe
6. Group Exhaust Drain
7. Expansion Section
8. Snort Muffler Valve
9. Snort Exhaust Mast
10. Screw Hoist
11. Mast Hydraulic Motor
12. Piston Control Valve
13. Snort Exhaust Blow (50psi)
14. Differential Gauge
15. Snort Exhaust Drain
16. Inboard Drain
17. Back Pressure Gauge
18. Lifting Screw Rods
19. Rod Bearings

Item 9 was a fixed tube within an 11.5" bore sliding tube. The fixed tube was connected as shown to the Snort Muffler Valve.
The slightly larger sliding tube formed the exhaust Snort Exhaust Mast, raised and lowered by the twin screwed rod mechanism 18 and 10. Driven by a hydraulic motor 11 from within the pressure hull.
The various pieces of equipment that formed this system were quite sophisticated and included mast supporting bearings in the fin.
Item 8, the Snort Muffler Valve could only be opened manually but could be closed by a hydraulic motor controlled from the engine room panel (not shown).
Part of the tee piece has been shown in orange but it has no relevance to the P & O classes. It is used in the main text to describe the similar system used in the Amphion Class pre and post snort.

For consideration of the Amphion Class pre snort arrangement the additional snort piping coloured orange and yellow should be ignored as should the Snort muffler valve. This leaves the original simple pipe bend from the Group Exhaust Valve through the hull to the surface muffler aft for surface running of the engines.

It should be noted that the engines of the 'P' & 'O' class were mounted on noise reducing mounts being self contained diesel generators. This was not the case with Amphion Class engines directly driving the propeller shafts and with the engines solidly bedded on the hull.

Thus the 'O' drawing Fig 2 shows a fixed and flexible exhaust section between the hull valve known as the Group Exhaust Valve and one end of the engine, whereas in the Amphion Class this large hull valve was solidly connected to the engine exhaust manifold between the 4th and 5th cylinders.

The exhaust of the 'P' & 'O' classes was telescopic as was the induction mast, again this makes no difference to using Fig 2 to gain an understanding of the Amphion Class system.

The Amphion Class surface exhaust systems for each engine were quite separate in the submarines built without snort and this remained the case with the surface exhaust systems of the later new 'P' and 'O' classes.

The direct connection to the engine cylinder exhaust manifold was by a large Group Exhaust Valve that sealed the hull for deep diving. Fig 2 shows this internal valve and its external piping carrying the engine exhaust gasses into the muffler tank mounted aft outside the pressure hull. All these items had cooling water jackets with pumped cooling water from the submarine's systems. This external piping would not have had any consistent immersion in the sea water while on surface passage and none when charging the batteries in harbour, hence the need for water jacket cooling.

The Group Exhaust Valve was opened well prior to engine starting and closed only after the engine was intended to remain shut down.

Inside the muffler tank the gases were released by an open valve (Exhaust Muffler) to expand and be cooled by water spray before emerging through the open tail pipes (port and starboard) to atmosphere

This exhaust muffler valve was controlled from inside the submarine by a substantial hand wheel that allowed rapid operation as the exhaust gas pressure rose or fell as the engine either was stopped or started. This required skilful judgement by the operator as the engine slowed with the consequent falling exhaust back pressures, to ensure any residual water contained in the Exhaust Muffler did not leak back into the engine.

The Group Exhaust valves operating wheels are prominent in roughly the amidships of any longitudinal photographs of Royal Navy submarine engine rooms of the Amphion Class, 'P' and 'O' classes. Sometimes the simple but substantial surface Muffler Valve operating wheel can be seen overhead, aft of the Group Exhaust, one port, one starboard.

This is not the case with the T Class and S Class class. No photographs are available (to the author) of these valves or their equivalent in either of these two submarine classes however drawings show the exhaust piping is similar to the Amphion Class and hull valves etc would be required.

When the Group Exhaust valve and Exhaust Muffler were closed, the piping between them was not flooded when deep dived and a drain was provided to detect and drain a possible sea water leakage of the Exhaust Muffler (valve) prior to the relatively leisurely opening of the Group Exhaust prior to an engine start.

The seat of the open Group Exhaust Valve was apparently not affected by exhaust soot and the open Exhaust muffler seat was constantly flooded with spray water.

This then was the arrangement for surface operation of the twin engines.



Fig 3 - Simplified line diagram of Amphion Class Induction.

Blue indicates pre-snort. Red & Green indicate snort additions. Mast vents are discussed in the main text.

The addition of a folding snort induction mast required significant additions to the piping feeding the existing induction hull valve that remained in position unaltered.

As has been mentioned in the mast description section, a circular water removal unit was fitted in the casing on the outside of the pressure hull, a relatively large, rather shallow drum, flat on its side. This unit also served to combine the two induction pipes coming from the base of the snort induction mast into one larger pipe.

The Bridge Induction inlets were retained for surface running and thus isolating valves were required to select either the Snort Induction or the Bridge Induction. These valves outside the pressure hull, were operated by hand wheels operating through rod and gear from the Engine Room. The outlets of these two valves were combined in a Y piece into one pipe that fed into the Induction Hull Valve dome. It is not clear if these two valve hand wheels were interlocked to allow only one at a time to be open, if not great care would been required to ensure that the correct valve was selected when either snorting or on the surface.

It is worth noting that later snort head valves of the Royal Canadian Navy 'O' class automatically opened and flooded the mast at about 125 feet if the submarine went deep with the mast full of air.


Diagram Note

As has been stated the Royal Canadian Navy 'O' class simplified exhaust diagram Fig 2 is adequate to enable discussion of the Amphion Class system before and after the installation of snort. The Amphion Class exhaust mast arrangement is generally similar but fixed in height, not telescopic.
The additional snort piping is coloured yellow. The orange shows the additional piping to alter the original simple bend to the muffler into a tee piece contained by the Group Exhaust, the Surface Muffler valve and the Snort Muffler Valve.

Stating the obvious, the 'P' and 'O' would have course been built with the tee piece of exhaust piping as part of the original design.

The Snort Exhaust System.

As already indicated the Amphion Class port and starboard additions for snorting involved joining a new exhaust pipe to each existing outboard exhaust pipe as it came out of the pressure hull and bent aft towards the exhaust surface muffler, thus forming a tee piece of piping with a double skin to act as a cooling water jacket. The addition can be seen in orange in Fig 2.

The forward outlet of the tee piece was fitted with a snort muffler valve, from here the port and starboard pipes were joined in 'Y' piece and continued to the base of the exhaust mast.

The Snort Muffler valve was operated from the Engine Room by a spindle through a pressure hull gland and was fitted with a valve seat grinding mechanism that allowed soot etc to be removed from the valve seat by rotation of the valve face against the seat..

The existing Exhaust Muffler (valve) hinged flap was fitted with a lock operated from the Engine Room when the valve was closed. The lock lever was adjacent to the Exhaust Muffler control wheel, operating though a rod and geared mechanism that passed through the pressure hull.

That this locking device was fitted as part of the snorting modifications is not certain but it is reasonable to assume that the type of valve fitted in the surface exhaust muffler was not originally intended to be closed tight with sea pressure on the one side and the exhaust pressure on the other. Snorting, the exhaust pressure was significantly greater than the sea pressure.

The 'Tee Piece' Fig 2 (purple and orange) formed by the water jacketed exhaust piping that connects the Group Exhaust, the valve in the surface exhaust and snort exhaust valve, is not flooded when the submarine goes deep, however an internal drain is provided to check there has been no ingress of water should the muffler valves have leaked, in particular the snort muffler valve that from time to time required the seat to be ground in with the inbuilt grinding mechanism.

At snorting depth, a reduced HP air blow (50lb per square inch) connection was fitted to blow the flooded exhaust mast and piping from the Snort Muffler Valve to the open outlet, clear of water before opening the Snort Muffler Valve and increasing the engine exhaust pressure until it exceeded the sea pressure. Air pressure was also applied to the exhaust system as the engine shut down

Obviously while snorting, starting the engine was a skilful business requiring teamwork and largely involved the exhaust system as the induction was merely a open pipe made ready well before the engine start.

The induction difficulties came when the snort induction flow ceased due the snort valve, unintentionally submerging and thus closing, with the engine(s) drawing a vacuum requiring a shut down. The management of this aspect of snorting was essentially in the control room by keeping the snort head float valve from closing due dipping below sea level.

As an aside, apparently modern teardrop hulls are even more difficult to manage while snorting in bad weather then the longer more conventional submarines that were far less subject to suction effect that tends to broached the submarine. This effect was particularly bad if the sea was from ahead or astern, this despite successful automatic plane control. It was often better to snort across sea as a matter of choice even if this delayed the ETA.

But to continue, if the CR failed to hold trim, the skill was stopping the engine and managing the exhaust back pressure to minimise the amount of sea water entering the engine. In Amphion Class one method was shut one engine first, thus using the back pressure of the second engine to prevent flooding in the common exhaust outlet while the first engine slowed and was shut down.

Then came the trickier job of shutting down the second engine. If flooding did occur one engine was ready to restart snorting while the second one was drained of sea water.

This then was the 1948 exhaust snort system of the Royal Navy, which continued to be used in principle in the new 'P' and 'O' class. With the most significant difference being the use of a telescopic exhaust mast in the new submarines that is shown simplified in the exhaust diagram Fig 2. It should not be overlooked that the propulsion system of the Amphion Class. T Class and S Class were direct drive. This system did not lend itself to snorting as readily as the propulsion of the Converted T Class and 'P' & 'O' where the propellers were always driven by the electric motors supplied from the batteries, with the diesel generators charging the batteries, thus a forced engine stop did not involve any temporary loss of propulsion as in direct drive where clutches etc were involved.

John Eade provided copies of the relevant pages from training documents for the 'P' class submarine.


This is useful point to mention the 'R' compensating tanks fitted as part of the original design of the submarine prior to snort, being one tank under part of the deck of the control room, shaped to fit in the curve of the lower pressure hull. It was divided longitudinally into two parts, port (1955 gallons) and starboard (2140 gallons). Source 'The Submarine Alliance' by Lambert and Hill.

In the Snort conversions of the Amphion Class the port 'R' tanks was used to take the water drained from the snort system prior to snorting, Fig 3. By observation of drawings and photographs, it can seen that the folding snort mast is located on the port side and when drained, the water simply moves down into the port 'R' tank with little alteration to the balance of the trim of the submarine. Clearly prior to each occasion when preparing to snort where the mast has to be drained first, the OOW had to ensure that the port 'R' tank had sufficient spare capacity to take all the drained water by pumping out the tank as required and generally adjusting the trim. There must also be sufficient capacity to continuously drain the water trap/dryer separating water spray from the incoming induction air.

With the streamlining of the Amphion Class, the starboard 'R' tank was converted into a fresh water tank. It is notable that the preserved Alliance has a gauge calibrated to a maximum of 1620 gallons. It is assumed that this gauge was fitted during streamlining conversion though maximum on the gauge of 1620 gallons is a puzzle.

Sufficient to say that the management of the 'R' tank contents was an important part of the whole snort operation and according to available official Canadian sources was considered so in the later 'O' class that also had an 'R' tank but whether it was divided into port and starboard is not known, but these submarines were designed from the start for snort operation. In a Canadian Force training notebook for the 'O' class, there is a warning reference to a margin of space of a minimum of 300 gallons, preferably 600 gallons.

A former Canadian 'O' class crew member states:

O Class R Tank contents gauge not fitted - Dip rod only. Main Line suction open throughout the Snort. 'R' Tank (capacity, about 2600 gallons) provided a safe margin for additional capacity in heavy sea conditions (excessive sea water entry across the Induction Hull Valve) and/or entry through Snort Drain 1 Hull Valve. (shut to two turns open in the Snort State) then through the Tundish to R Tank. Main Line suction open throughout the Snort. Overall, it was a balancing act with Ballast Pp./Trim Pp. orders by the Trim OOW.

It has been confirmed by a former Royal Navy 'O' class OOW, a flexible dip rod was used to measure 'R' tank.

The conversion of the T Class required considerable alteration to the area below the control room deck to fit the extra battery and no information is to hand as to the snort drain arrangements in the these conversions.


Diesel Submarine Battery ventilation has to be considered along with the Engine Air induction and Exhaust system. One of the more hazardous situations in a submarine is when the concentration of hydrogen emission from charging battery cells forms of 3% of the atmosphere of the submarine.

Fig 4 - Battery Ventilation System on the A Class Submarine 1945

It is not known if the Master Outboard Ventilation Valve was retained in the streamlined submarine modification. The Inboard 
Ventilation Valves No 1 & 2 Section Hull Valves were similar one piece construction with the main flapper type valve in one casing. The main hull valves were operated with a rack and pinion with the operating wheel within the pressure hull. The quick acting valves within the pressure hull were lever operated. Check drains were provided at each inboard valve
It is not known if the Master Outboard Ventilation Valve was retained in the streamlined submarine modification. The Inboard Ventilation Valves No 1 & 2 Section Hull Valves were similar one piece construction with the main flapper type valve in one casing. The main hull valves were operated with a rack and pinion with the operating wheel within the pressure hull. The quick acting valves within the pressure hull were lever operated. Check drains were provided at each inboard valve

Fig 4 shows a simplified system for the Amphion Class but basically applicable to the rather more complex 'P' & 'O' classes with one notable exception. Due to the piping layout, when in harbour the outlet in the engine room had to covered with a plate to provide sealed continuity to the outlet on the fin. In addition there were small fans that provided continuous ventilation when the main fans were not needed, these were after all, very much bigger batteries than those found in the Amphion Class and hydrogen could be generated when discharging.

In the files there is photograph of a 'P' or 'O' class (OTTER?) being scrapped with the casing stripped away and a cell being removed. The battery ventilation pipe to the No 1 battery compartment seen attached to the pressure hull with substantial stand off brackets. The valve housing can be seen turning into the pressure hull. The pipe seems to be about 400 mm in diameter.

To the best of the author's knowledge, nothing changed in regard to the design and operation of the Battery Ventilation when the older submarines were fitted with snort.

In older submarines such as the Amphion Class, on the surface, the dangerous accumulation of hydrogen gas while charging does not seem to have been a problem, with strict NO SMOKING rules when the charging voltage determined that the cells had reached the gassing stage of the charge. With the battery ventilation system clearing the cell emissions to the Engine room when at sea or though an outboard outlet in the conning tower when in harbour.

Equalising overcharging for up to 7 hours in addition to the normal charges was an essential part of submarine battery maintenance; else capacity fell away, with some cells worse than others. Ideally the overcharging was carried out in harbour on a monthly basis with the bulk of the crew living ashore.

Unfortunately a number of explosions occurred in diesel submarines when snorting that caused concern. In particular the Trenchant during the large exercise called the SUMMER WARS, 1950. The author was aboard the Artemis that surfaced to go to the aid of this submarine after she suffered a severe battery explosion in the accommodation space at the time we understood that the accident happened while snorting.

George Malcomson, Archivist of the Royal Navy Submarine Museum has told me, 'According to the database history that we have on file for HMS Trenchant (1)

It reads: 13 June 1950: While taking part in the Exercise Summer War in a dived state off the North West Coast of Ireland, HMS Trenchant was severely damaged by a battery explosion caused by a build up of gas during battery charging while snorting. The practice of charging while snorting was restricted.
Paul Kemp in his book 'Submarine Action' states that following the accident the FOSM said 'Like ammunition it (snorting) is safe as long as one remembers that it can be VERY dangerous'.

George Malcolm son, Archivist, Royal Navy Submarine Museum advised me, I can confirm that Raw was FOSM at the time but I have no obvious record of this quote by him.

In the detailed electrical operating T Class conversion manual BR 1965, dated 1953, various charging conditions are defined including overcharging, but the manual clearly states:

as the maximum state of charge allowable under snorting conditions is subject to periodical review and possible amendment, the stated charge conditions may not be permissible in practice.

I understand on good authority that overcharging at sea was not allowed on the modern Upholder Class . Only very occasionally was a dispensation from higher command ashore given on a long non-operational transit when the a regular equalising charge was overdue. Apparently these strict rules were a consequence of several gas explosions including the Alliance where three men were killed.

This in a US Navy training document for enlisted men:

Explosive and noxious gases are evolved from a lead-acid storage battery cell. Hydrogen, an explosive gas, is evolved when the battery is being charged or discharged. Due to chemical self discharge, hydrogen is also evolved when a battery is on open circuit. A mixture of hydrogen and air with 4 to 8 percent hydrogen will burn if ignited by a spark or flame. Concentration above 8 percent hydrogen will explode with increasing force as the hydrogen concentration rises. To prevent the hydrogen concentration from approaching the Inflammable limit, a 2.5 percent concentration is considered to be a safe maximum limit. In operation of the battery, the hydrogen concentration is kept below 2.5 percent by battery ventilation.

A modern US Navy document states that cell hydrogen emission is sensitive to barometric atmosphere changes and this can apparently lead excessive concentrations of hydrogen while snorting.

Modern technical literature shows that charging submarine batteries in the modern snorting environment is quite a sophisticated business compared to the situation in 1948, and beyond the scope of this article.


To conclude this basic description of the conversion of the Amphion Class submarine for snorting, several vitally important pieces of equipment common to all snorting submarines have to be mentioned, first the large vacuum gauge. At least two of these gauges were fitted, one in the engine room and one in the Control Room.

The Exhaust pressure gauge and the Differential Pressure gauge measuring the difference between the engine manifold and the open snort exhaust mast with valves closed.


All the members of the class were progressively modernised with the most obvious feature being the streamlining of the submarines with a fin replacing the original open conning tower.

An apparently new design of fold down snort mast was fitted with a globular snort head with internal valve, an improved version of the type illustrated. This new head was later covered in rubber by the submarine’s engineering staff (see anecdote No 6).

Unfortunately I do not have any details of the fitting a fin had on the engine induction inlets and the exhaust mast. I must assume the snort arrangements remained substantially as before.

I think it is reasonable to assume that the drum water dryer was replaced by a Helix dryer as in other submarines.

And as has already been discussed, a Snort Drain Tank was formed in space taken from No 5 Internal Fuel Tank., shown in simple form in Fig 3. I assume this was to prevent free water swilling about the engine bilges as had previously been the case.


Fig 5 - Mast System of Streamlined Amphion Class 1961

It is reasonable to assume that at rest (as shown), the yellow fixed tube extended inside most of the length of the moving red tube. It is difficult to determine the exact operation of the hydraulics but the general idea is clear.
It is reasonable to assume that at rest (as shown), the yellow fixed tube extended inside most of the length of the moving red tube. It is difficult to determine the exact operation of the hydraulics but the general idea is clear.

Much later, a number of telescopic snort induction masts housed in an extension to the after part of the fin, were fitted in the period 1965-74 to the streamlined Auriga, Aeneas, Alliance , Ambush, Artemis, Anchorite, Andrew , Acheron. The Alliance book has drawings of this arrangement.

With this significant modification came the removal of the Bridge Induction inlets, piping and valves leaving a remarkably simple induction system as can be see from the line diagram in Fig 3 with the snort head being the sole engine induction inlet.

Unlike the telescopic snort induction masts fitted in the Converted T Class, 'P' and 'O' classes the Amphion Class conversion masts raising section did not pierce the hull. On the other classes there was a periscope like mast section passing through the hull with internal raising mechanisms.

The still fixed exhaust mast was more or less in the original position with an exit through the after part of the fin.

It is not known why it was possible to avoid piercing the hull of the Amphion Class, but perhaps there were issues and compromises such as the height of the fin and a lesser range of height control in the Amphion Class. The Amphion Class certainly had the benefit of not adding another telescopic mast in the crowded Control Room.

The earlier Amphion Class folding mast as previously described, was automatically flooded and vented free of air when not in use in the lowered position in the submerged submarine and drained when surfaced. Though more simple in operation, this was also the case with the Amphion Class telescopic mast and as can seen on Fig 3, there was a normally open 6 inch Outboard Flood and Drain valve to drain the mast and external piping when surfaced or to flood the mast and external piping when submerged. It was only closed when snorting and for this purpose could be operated from within the submarine as could a normally open master valve that was fitted as a back up. The outlet/inlet pipe was fitted with a strum (filter) to prevent clogging with weed etc.

Similar arrangements were provided in the later P & O class, see Fig 6 and no doubt the converted T Class.

Museum Boat Alliance during repair work. Looking aft showing the exhaust snort pipes as they were 
after the boat was streamlined. The induction pipe passes into the hull forward, out of sight
Museum Boat Alliance during repair work. Looking aft showing the exhaust snort pipes as they were after the boat was streamlined. The induction pipe passes into the hull forward, out of sight


It is of interest to mention that there are photographs from the early sixties showing the streamlined Tireless fitted with the later spherical snort head fitted to folding mast. The mast does not appear to be of the original combined mast and it reasonable to assume that the exhaust on the Tireless had been moved to a position in the aft of the fin similar to the streamlined Amphion Class as shown in The Alliance book.

See the photographs in the article Diesel Submarines 1948-1958, Images 14 and 15.


The Royal Canadian Navy became Canadian Forces Maritime Command in 1968 but in this article will be referred to as the the Royal Canadian Navy.

All detail taken from copies of Royal Canadian Navy training documents provided by the late Dave Perkins, formerly of the Royal Navy and Royal Canadian Navy. On the principle that a picture is worth a thousand words, two Royal Canadian Navy training diagrams are shown.

These were originally rather poor copies and have been redrawn and coloured by the author, though in substance exactly as originally prepared.

There were significant changes in the Royal Canadian Navy 'O' class Onodoga SS73, 1968 and Okanaga SS74, 1968. It is assumed these design modifications were prior to building, not alterations.

Fig 6 - Royal Canadian Navy 'O' Class Modified Induction System

HMCS Onondoga (S73) and HMCS Okanaga (S74) 1968
HMCS Onondoga (S73) and HMCS Okanaga (S74) 1968

It has been suggested that the same changes were built into later Royal Australian Navy and one Royal Navy 'O' class submarines apparently known as Super 'O's, though no documentation is available to the author.

The most likely 'O' class with the modifications is HMS Onyx.

However identifying which of the class may or may not have had the similar alterations to the Royal Canadian Navy Submarines is beyond the scope of the article, it is sufficient to note that these important alterations came 20 years after the basics of the original system came in to fleet wide service.

In these modified submarines the battery ventilation system main ducts were brought inside the pressure hull and arranged to give a distributed input and output across all the cells. Fig 7.

Fig 7

The input to the battery ventilation system was in effect direct from the snort induction outlet, to a tank (S Class ) in the Auxiliary Machinery Space under the Control Room flat. The author's experience would suggest this is was a big improvement on the original system found in the Amphion Class and 'P' & 'O' classes, see the simplified Amphion Class battery ventilation drawing Fig 4 where the air inlets are in the main spaces of the submarine, not direct from the fresh air coming down the snort induction.

The changes to the snort induction involved bringing the induction through the hull into the Control Room and replacing the older hinged clapper Hull Induction Valve used in earlier submarines with a Deri-Sine motor operated sluice type valve. The valve was operated from the Control Room but could be closed in an emergency from the engine room. Fig 6.

In general terms the induction remained as before but with the outlet in Control Room compartment rather than the Engine Room. This was another major change in thinking with the control of the induction entirely in the Control Room. From the drawings it appears that all the incoming air to the engine had to pass from the AMS through the CR/ER bulkhead door, unless there is some trunking provision not shown?

The return bend in the induction outlet was a form of water separation. Terminating within a tank designated S Class sitting above the 'R' tank into which it finally drained,

Key Items

(a) A helix drier induction system is not fitted.
(b) The induction hull valve is a sluice valve operated by a Dari-Sine Motor and is sited overhead in the control room.
(c) The main control valve for the induction hull valve is sited in the control room and the emergency control valve in the Main Generator Room.
(d) Snort drains 1 and 2 each have a backing up valve.
(e) Three viewing panels are sited on the inboard side of the emergency flap valve.
(f) The flooding indicator pipe is led to a pressure sensitive switch wired to a buzzer and flashing light in the control room. A simple but effective device
(g) The inboard trunking terminates in a separate tank (S Class tank) sited in the MS above 'R' tank. 'R' tank vents into the induction mast well.
(h) Air supply to the generating engines is taken from a grill on the S Class tank via the ACS. Air supply to the battery compartments can be taken either from S Class tank or the ACS.

Associated with these Induction inlet alterations, the Group Exhaust Valves were also changed to an air operated Sluice types controlled from the starting platform.

(a) The bore increased to 8 inches.
(b) The valve is not in the gas stream when open.
(c) The resistance to shock is increased.

The valve consisted of a double faced sluice valve made up of two lids working in a body and operated by an external piston through a rack mechanism.

A toggle gear is provided for locking the valve in the shut position, this being operated from an HP piston.

Hand operation was available for both the lock and the valve.


In his article Upholder Class Boats Go To Canada, Commander Jonathan Powis RN, commissioning captain of HMS Unseen, had this to say on snorting in the Upholder Class :

A large double-armature motor on a single shaft provided propulsion through a large modern propeller. A 9,000-amphour battery capable of rapid charging along with two Paxman Velenta diesels (with twice the power of those in the O class) resulted in an extremely flexible propulsion system. Efficient hull design kept propulsion loads - and discharge rates? low, despite the increased operational electrical load. Patrolling at slow speeds would require 40 to 60 minutes of snorkelling per day; a transit at 8 knots would require snorkelling approximately 30% of the time. Top speed submerged matched that of any similar SSK and could be maintained for more than 90 minutes from a fully charged battery. Further, once a submarine reached the end voltage, it still had considerable capacity remaining for operationally useful speeds.


Although powerful, the main engines were not especially sturdy. They were designed originally for use in railway locomotives, and stress of stopping the rotating parts from full power at the end of snorkelling led to many failures. Once reorganised, this was relatively easy to fix. Similarly, the motor generator sets were working at their maximum limits, and redesigned brushes and filters had to be fitted during the early operational life of the class. In addition, the exhaust temperature of the powerful generators was unexpectedly high and salt deposits in the exhaust-valve seating caused leaks when snorkelling was finished.

Other less dramatic problems caused a few headaches in the early years. Consequently, acceptance into service of the first of class was late by three years. Although subsequent boats had an easier time, the press found a great deal to harp on. As one of the early commanding officers I spent much time preaching the message that the boats were a great success.

Regarding similar modern submarines of other countries, in 2001 this reply was received from a reliable European submarine source in answer to a query about charging while snorting in modern submarines.

During snorkelling, charging is being done in the voltage area below 2.4 V/C to avoid development of gas in the boat. Up to 70% SOC (State of Charge) the snorkelling period is inverted proportional with the size of the DC generator. From 70 to 80% SOC, the time depends upon the cell construction, where a so called double-decker or a BLC (Bottom Lug Connection) are especially favourable. From 80% SOC no snorkel charge is being done, as the risk is considered too high in proportion to the result achieved.


The practice of snorting has, over the decades, been the subject of many studies. One in the public domain is A DIESEL -ELECTRIC SUBMARINE PROPULSION SIMULATION by M A Bowker and N A Haines, a paper presented to the THE INSTITUTE OF MARINE ENGINEERS in 1991. This computer simulation was based on the RN type 2400 that became the Upholder Class. The purpose being to optimise the practice of snorting. The authors are both experienced Engineer Officers of the RN with academic backgrounds supported by sea service.

The modern submarine is always submerged in transit or operationally and the simulator enables various combinations of snorting or running on battery to get the best results in any given circumstance. It is possible a commander may decide to snort at 4 knots for a period and proceed at depth on battery at a speed of 8 knots. Slower snorting speeds in fair weather might be desirable to minimise water disturbance and possible detection. All the parameters are calculated including fuel used and the results displayed. No indication is given that the simulator was intended to be used at sea, but rather to define parameters for the guidance of commanders.


Despite there now being no diesel electric submarines in the Royal Navy, the nuclear submarines still have a snort system that allows the diesel generator to be run submerged to charge the large submarine type battery.

P D Hulme April 2009


Over the years I have collected a number of anecdotes about snorting, they may be of interest.


These extracts from 'letters home' are courtesy Dorset Submariners. They are quite genuine but the authors prefers to remain anonymous.

Sidon Letter Home. Written in 1953

This is a verbatim copy of a letter I sent home to my parents, written at sea during my first time as a serving submariner and as a crew member in the submarine Sidon on an exercise in September/October, (I was twenty one at the time and reading it now makes me feel embarrassed as it must have frightened my poor mother near to death). Tactless it may have been but as an accurate account it is a truthful word picture.

We surfaced at twelve noon after my longest dive. We had been down since 1.0 am Saturday, thirty-five hours in all. For about eight hours we have been 'snorting' so we got some fresh air into the boat while we charged the batteries. Oh! And a few smokes. It was our last dive so nobody minded too much. It is a hell of a strain somehow when you are 'snorting'. I don't know why it should be really. If you drop a bit too deep, the engines suck the air out of the 'boat' and it's a bit sickening for the ear drums but I can't see why it should strain the nerves quite like that. It could be the constant expectation of a 'dip' or perhaps the popping of the ears each time she does it.

Well that's the lot for now, I'll add a PS. when we get in. I'm glad it's nearly over but it's been an experience even if it is far from the last one.


Tally-Ho Letter Home. Written 1954

This is a copy of a letter I sent home to my parents, written at sea as a crew member in the submarine Tally-Ho on a fortnights exercise in October/November, it covers the first six days only, prior to a previously unexpected rendezvous with another vessel.

We came up to 32 feet to 'SNORT' this morning at about 0800 hrs, and returned to 110 feet at 1600 hrs tonight. I did another watch last night, from 8 pm. to 11 pm but that is all I have kept so far. When we were 'SNORTING' today, a chap burst his ear drum. He couldn't clear his ears and the vacuum in the boat caused it to break. As a result he's been 'turned in'


Hello again. Today is Wednesday, and we still haven't surfaced, which means 93 hours dived until midnight.

Last night was uneventful but today has been quite a pantomime. As has become the routine now, we came to 32 feet to 'SNORT' for the day. At noon I was on watch and on the forward hydroplanes. For some peculiar reason we lost full control and tried to 'SNORT' at 45 feet, an impossibility in these boats. (The loss of control was probably a layer of less dense water, due to reduced salinity or lower temperature.) Needless to say, we stalled the engines through lack of air. The Skipper threw us both off the job and replaced us.

(The 'Diving Station Crew', the experts at depth keeping, took over.)

Now once more I've got to say 'Goodnight'.


I didn't write last night but I thought I'd finish this letter off as we will be surfacing later tonight at about midnight. We are to rendezvous with some ship and she may take our mail. I'll write another next week.

Our submerged time up to tonight is 141 hours, 6 days all but 3 hours.


No 2

Michael Young, Cdr RCN (Ret) was a submarine watch keeping officer of the sixties serving in OBERON and converted T Class class submarines. He was kind enough to answer my questions on his snorting experiences aboard these classes of submarines and has approved my reproducing them here.

he fastest snort transit I remember was on an 'O' boat. I was the navigator at the time so I can remember much of the details. We went from Plymouth to Derry around the west of Ireland. We had to make good something like 8 knots SOA so that meant we snorted most of the time.

The weather was awful. We ran north in a huge beam sea snorting virtually full time. It was the most uncomfortable passage I have ever experienced at sea. We were pushing 10 knots much of the time and the vibration on the search periscope was incredible. Sitting on the roundabout keeping a good lookout was no picnic but it was the lesser of two evils as OOW, keeping trim was worse! Broaching was a regular event.

I would suspect our indiscretion rate was close to 80% but given the weather no crabfat would have been airborne anyway. Conversely, I did a mystery in an Oberon class where our indiscretion rate was less than 20% over a 6 week period. The T conversions were every bit as good as the Oberon's in this respect going north from Faslane or wherever dived would not be a problem. Much of the indiscretion rate was a function of the CO's sphincter. If he was twitched about the box and did not really understand the limitations Exide imposed, then topping up the box became the overriding factor. I was lucky. My CO's were all great guys who knew their stuff and would get you home.

We always ran with two OOW when at periscope depth, whether snorting or not, and often with two when deep and searching. We'd change positions often. I think that is why we ran in 2 hour watches.

The real question is not so much the capability of the boat to achieve a particular speed to make the SOA. In my view, it is the operational decisions that are made to make the SOA under the particular circumstances. Running an extended T boat dived for 5 days at 7 knots SOA, snorting 25% to 30% of the time is technically a feasible proposition. So the answer to your specific question is yes. The A boats crossed the Atlantic dived as did the Oberon so I don't see why a T conversion would have a problem. But if that same transit were planned to cross through a high threat area, air, surface or undersea surveillance systems, then 7 knots as the SOA may well be suicidal because if you are snorting you cannot listen well and the enemy can sure hear you, especially the not so quiet Ts. Spending 25% to 30% of your time deaf and noisy is not a smart move, as noted above! So the issue comes down to planning and intelligence, pick the right SOA for the route and the circumstances.

So I'm not sure if this has added to your knowledge but I hope it has helped a bit!

A further comment on modern submarines,

The advances in technology evident in the new generation of British submarines can also be seen in two other submarines of the new generation. One of them, the German designed and built TR 1700 which is now in Argentinean service, can be said to represent the leading edge of the generation. The first of the class, the ARA Santa Cruz, arrived in Argentina on 14 December 1984 after a submerged transit of 6,300 nautical miles. Her average speed made good was reported to have been in excess of 10 knots, with a maximum of only two hours in each 24 hour period being required for snorkelling to charge the batteries. It is also reported that she arrived off the River Plate with more than enough fuel to complete the round trip back to Europe. This submarine is also credited with a top speed well in excess of 25 knots, demonstrated on sea trials, and sustained speed of 20 knots for more than three hours.


Just reread the last part of your message. The routine in a transit such as you mention would be to snort likely once a watch rather than a whole bunch of snorting followed by an extended period on the battery. Getting the battery too low means longer charging so the prudent course is snort when you can rather than when you must. That may change your equation a bit.


No 3

Taken from Bill Dalton's web site years ago, he doesn't appear to be on the web now. I'm sure he will forgive my reproducing his article here. A partial official report appears in The Alliance book.

A personal account of the Ambush 's artic snort cruise.

On the 25th of March 1948 HM Submarine Ambush surfaced just a short distance from the Firth of Forth after completing a patrol of six weeks submerged, this patrol was started from Roth say on the Clyde and to go as far North as possible, if possible up to the icecap. This was after the Alliance had done a similar patrol in the equatorial waters of the Atlantic; both these boats had been fitted out with the Admiralty version of the German Schnook and the Ambush was to test in the Arctic region.

The boat also had an experimental fore and aft planes control that the Admiralty was anxious to test; the boat had her normal complement of crew plus one Lieut Commander Surgeon and an L/Sickbay Rating.

By to days standards a six weeks patrol is normal but in 1948 it was a bit of an unknown factor as to how the new Snort as we called it would stand up to the ice and weather, also the fore and aft planes control was viewed with a little suspicion, we knew what it was like when Snorting and the planesmen didn't keep his mind on the job, with the engines going and the Snort going underwater the top valve would close cutting off the air to the engines, the engines would then use the air from the boat and that would then put a vacuum in the boat causing your eardrums some distress. This was why we had the Surgeon and Sick Bay Tiffy onboard, throughout the trip we had numerous audiometer tests plus medical tests.

From the outset of the patrol we knew that we were going to get some rough weather, January, February or March isn't the best time you would pick for a voyage to the Arctic Ocean, we soon found out about it when we went into the notorious Pentland Firth, still I expect the powers that be, wanted the equipment to be tested in the worst possible conditions.

The fore and aft planes automatic gear was the first to go to the relief of all the crew, it was like riding a roller-coaster, we were all glad to have our own competent planesmen on watch, after the first couple of watches things began to settle down, we all had our own bunks { no hot bunks} we even had a salt water evaporator to trial, the idea of the patrol was to keep a small vacuum in the boat for the full voyage, we had to surface once every 24 hours to send our position signal, the skipper Lieut A G Davies would send a personal signal to his wife and she would send a copy by mail to all of the next of kin of the crew, once every 48 hours we would surface to let the navigating officer take a fix by instruments, we kept the vacuum by using the bottom hatch of the conning tower as an air lock.

The Ambush was proving to be a better sea boat than expected, she had the squarish ballast tanks of her class but she took the weather well, it wasn't until we were well north of Jan Mayen Island that the weather turned really foul, we had a blow of weather well above gale force that lasted for five days we had to surface, snorting in that sort of weather was impossible we were tossed around like a cork in a bottle, we spent most of our time pumping bilges, hot meals were rare, but we had onboard cases of tinned food given to us as extra from the depot ship Montclare, the only thing wrong was that it was salvaged and that all the labels had been washed off so you had to make an educated guess as to what you were going to open if you shook it and it felt solid it could be meat, jam, or even tinned bread if it was liquid it could be soup, tinned fruit, or juice, it was sending the Chef mad.

When the weather settled down we carried on with the Snorting and as we were getting near to our turnaround point {we should have been further north but had lost time in the storm} we started to run into small pack ice we were to learn later that the storm we had just been through had also brought down the pack ice, the ice started to get larger and more of it. It was an eerie feeling when in your bunk and you could hear these lumps of ice scrape their way down the hull, you had no idea how large they were and if there was an accident no one knew for sure where we were {I don't think we knew ourselves} and it would take days to get to us, so when our fore ends pointed South no one objected.

The trip back to the Firth of Forth was uneventful and the records of the trip show that the Admiralty were satisfied with the way the Snort operated,

No 4

Dave Perkins, sadly deceased, submarine author and long serving submariner in the Royal Navy and Royal Canadian Navy, responding to my question about long transits snorting.

Scratcher Posted: Dec. 22 2004,

Not just P's and O's but modernized A's and super T's running from Faslane 1959-62 also dived a couple of days out and stayed dived until nearing home base fifty or sixty days (or more) later. Was offered a peek through the periscope once about three weeks out and everything was grey and miserable so didn't bother again.

Them was the days. Eh!

No 5

1950's to early 60's submarine life on patrol

My name is Michael Dearden. In those days I was a Leading Radio Electrician (electronics engineer). I left the navy as Petty Officer in 1968 after fourteen years service, ten of which were in boats.

This was the cold war. Nobody trusting anybody, everybody trying to find out what the others were doing.

Enter the P & O Class submarine. Designed for long, silent patrols with sophisticated, long range listening sonar (mounted in the ballast tanks).

We regularly went out on three month, 90 = day patrols on HMS Walrus from Faslane in the late 50's early 60's and I bet they were much harder on us then than patrols are today on those huge, comfortable neuks! These were basically wartime patrols. Our patrols usually started early in the morning from Faslane, the 3rd. Submarine Squadron, located in the Gareloch off the river Clyde in the West of Scotland. We'd proceed down the Gareloch, through Rhu Narrows and into the Clyde. A turn to starboard and we headed south, leaving Gourock to port and Dunoon to starboard, headed for 'The Cumbraes'. Once clear of Little Cumbrae, we would dive to periscope depth and commence snorting. The next time we surfaced we were back in the Clyde, just south of the Cumbraes, dirty, smelly, probably somewhat thinner and certainly with very sore ears.

Our first inkling of a pending 'sneaky-beaky' patrol, as we knew them, was when, as the electronics engineer on board, I had to remove the two emergency radio beacons from their places in the casing. We would also strip out the radar and most of the radio transmitting equipment, to be replaced with huge amounts of electronic listening and data recording equipment. We also took on a huge amount of extra food, mainly tinned and dehydrated, which rapidly formed a 'second deck' along all the passages, greatly reducing the already tight headroom.

They were just so much fun! Swing the lamps I hear! Doesn't it just make you want to cry!

The course from Cumbraes was always the same. Turn West then South, passing through the channel between the Isle of Arran and the Mull of Kintyre. Turn West again, leaving Sanda Island to starboard and Ireland to port, then North all the way up the west cost of Scotland until you left the dreaded Cape Wrath to starboard and headed North East along the Norwegian coast to starboard and so to the Russian exercise areas off the North West coasts of the USSR.

These long snort transits were very uncomfortable for the crew, due to the size of the engines and the huge amount of air they pulled. Most of the patrol was spent with quite a large vacuum in the boat, and therefore very sore eardrums. This was constantly worsened by frequent emergency 'stop snorting' orders on the detection of a possible threat, when the snort mast was dropped and the engines seemed to take forever to stop, pulling more and more vacuum!

Mine, and the radar operators specific training for these patrols consisted of concentrated learning of all the Russian radar signatures we might hear on the then 'very secret' SHF-DF system fitted to the P&O boats, especially their aircraft ones. This was where the greatest threat was expected to come from. Another major threat were the ever present, Russian 'deep sea trawlers'. These were converted deep see fishing boats bristling with electronics, sonar and radars designed specifically to 'listen' and track NATO submarines.

During these patrols, the lads in the sonar shack would monitor and record all and every ship/propeller signature heard while the periscope tried to positively identify the ship. Of course this often meant getting in quite close and there were many occasions when we were 'detected' and the order 'flood Q, full dive on the fore planes, full ahead together, 400feet' would echo around the control room and we would slide away at 12 knots to the safety of deep water.

No 6.

Keith Hallam has made the following comment on the forum about this article.

I've just been going through this article and found this...

On passing through the pressure hull via the Hull Induction Valve, the flow continued through the manual Emergency Flap Valve (In the 'P' & 'O' class the flap of this valve was designed to shut automatically on the passage of a full bore of water, whether this was the case in the Amphion Class, I don't know.)

It was definitely the case in Artful and Amphion. The handle was held open by a spring loaded ball bearing type detent. It didn't need full bore flow to whack it shut. As I've mentioned before, the brass knob on the end of the handle would have cracked your skull open if it caught you. Once it tripped you had to be pretty smartish to haul it open again, watching the vac gauge going down and the engine noise changing, starting to labour. I never heard of anyone getting a burst eardrum.

One of the causes of deafness is loud noise and being under reduced pressure makes it worse.

Keith Hallam Joined the Submarine Service in 1959 and served on Talent, Artful and Amphion, as first a Stoker Mechanic, rising to PO Stoker Mechanic. After extended training to be a Mechnician amongst significant shore postings he spent 5 years on the SSBN Revenge as Outside ERA or Outside Wrecker as the position has been long known in the RN Submarine Service, responsible for all mechanical equipment outside the engine room.He retired after 22 years service in the Royal Navy.

His Amphion Class service was post the 1951 loss of the Affray. So we have no means of knowing if the flap valve was like this on the 'A ' class prior to the loss.

Artemis prior to the loss. I later joined Amphion in 1953 and remained with her when she entered the Dockyard for a complete refit, but so many things were stripped and refitted, that particular changes in the Induction area would not be obvious unless someone drew my attention to the matter as being a consequence to the loss of the Affray in 1951.

A glance at Fig 3 will show that prior to the fitting of snort, a hull induction valve was still required for the open induction inlets on the bridge that flooded as the submarine dived. In this drawing (LH side) the snort piping is an addition to the as-built bridge induction piping system.

Whether a flap valve was fitted prior to snort being fitted is not known, but diving quickly on the klaxon while running on the surface would require the hull to be sealed by an hull induction valve in a similar manner to that occurring if a snort head valve jammed open on the boat going deeper than snorting depth. This happened with ice and later heated head snort valves were fitted. And of course, also if the snort mast broke, an occurrence that has only happened once since snort fitment started about 1945 and that aboard the Affray.

In more recent times I have become aware that the subject of an automatic valve to prevent flooding through the Amphion Class submarine snort, induction valve was discussed several times at Question Time in House of Commons when questions were asked of the loss of the Affray in April 1951.

For instance, Hansard, 14th November 1951 Mr John Arbuthnot (Member for Dover) asked the First Lord of the Admiralty "and in particular if he will consider changing the design to an automatic valve at the bottom of the snort tube."

The First Lord of the Admiralty sought leave to answer at the end of question time and did so in a lengthy statement that included this extract:

A modified form of snort has successfully passed its tests and is being fitted to A Class Submarines.

I should like to say here that the adoption of an automatic valve has been considered on several occasions. Automatic arrangements for meeting a possible emergency which might never occur are apt to induce a false sense of security, and it has generally been preferred to rely on a correct drill to meet such situations. We are, nevertheless, considering the technical means of providing a thoroughly reliable automatic device.

Responding to further questions, the First Lord of the Admiralty said

I am glad to have the support of the hon. Gentleman, who was Parliamentary Secretary to the Admiralty such a short time ago. It is, of course, a very disappointing result (raising Affray ), but I think the decision to which we have come is inevitable. In regard to his second question on the automatic valve, I can assure him that we are pushing ahead with consideration of that point.

Lacking specific naval documents today, these questions and answers at the highest level of government, indicate that an automatic valve was a topic in the Affray debate and gives weight to the supposition that the emergency flap valve in the snort induction trunking was fitted to all Amphion Class submarines as a consequence of the loss of the Affray and the still unexplained breaking of her snort mast.. And probably fitted in other older submarines and certainly fitted to the later 'P & O' classes as the drawing above indicate.

I have no knowledge of the form the modified snort mast took, nothing obvious to me on Amphion IN 1953 after a refit and certainly the snort head valve remained the same old style?

Hi Peter

I can't remember what the Artful snort mast was like, it did have the hinged float.

The snort mast on Amphion was definitely teardrop shape in section, with the rounded end to the front. I presume it was for streamline/noise reduction. The head was the ball float type with electric kettle type heaters, although we didn't need that out the Far East. I told you about sticking secret rubber sheet to it for anti radar detection.

Artful went under the ice just before I joined her in 1960. There was some strengthening of the top of the fin for surfacing up through the ice. I also saw a load of photos that had been taken, obviously through the search scope, of the underside of the ice.

It was a bit dicey, they had to look for thin ice to be able to push up through. There were also great lumps of ice poking down hundreds of feet that they had to be careful not to bump into. There was a special upward sonar to check for thin ice.

All this stuff we just took for granted and now we have difficulty in getting the info on it.

Cheers, Keith

Hi Peter,

Amphion definitely had the ring float in 1965. I've said before, I remember repairing the secret squirrel radar absorbing rubber. We had to account for every sliver we cut off to make the pieces fit. It was special glue also with a skull and crossbones on the tube. Maybe that was to scare us!

Cheers, Keith

Most recent from Keith

Hi Peter

I've been looking through old pics (not digital) for some info. I did have some of Amphion. The Engineer knew I was into camera stuff and told me not to take photos of the rubberised snort head but I thought that was pretty stupid as anyone could. But I suppose it just looked like green paint. The Wrecker and me were told not to discuss it or make a big deal out of it.

At that time the four boats, Alliance, Ambush, Andrew and Amphion were experimenting with different hull colours. Black, green, blue and different shades and shapes of camo so the snort head didn't stand out too much when alongside. I did have some pics!

Problem is when I left the mob we bought a hotel in Blackpool. We were near South Pier and there was a massive storm the second year at high tide and our basement got several inches of water in it. We had boxes and suitcases stored. Loads of loose pics were stuck together, albums soggy!

I haven't found any pics!

Cheers, Keith

No 7.

This note and other documents in the main article, on snorting were from the late Dave Perkins, he had a long career in submarines in both the RN and RCN. He also was an RCN submarine historian and author.

Hi Peter.

If I recall the A-boat system correctly, the hinged mast was free flooding in the lowered position.

The A-boat periscopic mast was flooded on completion of snorting and the external portion was free-flooding in the lowered position, very similar to the O-boat system as attached.

You'll note in the Stop Snorting drill that care was taken to flood the external part of the mast on completion of snorting. The internal part (the tube) was tested to full diving depth. I've attached the O-class systems for your interest.

I don't ever remember running on the snort mast when on the surface in a streamlined A-boat even in bad weather in the Arctic. The tower was always the primary means of getting air into the boat. As a result the CO's cabin in the tower was commonly used as a store-room. Once the modern electronic fire-control was installed in the O-boats we always ran shut down using the snort mast for induction. The snort mast, like the exhaust mast, was open to sea when not in use. When doing this it was necessary to raise the mast about 3ft.

I don't have any more detailed information than what I've provided. It's of interest to note that the Upholder/Victoria-class always use the snort induction system for running the engines.

Keeping trim on a sudden stop snorting was tricky as we were invariably heavy. The ER was a bit of mad house as they had to stop the engines, shut off the system, shut down the compressors, shut down the distillers too if they were running and man the ballast pump. Fun.

For now,


Reproduced from photocopies of the evidence papers

H.M.S. AFFRAY- Minutes of Board of Inquiry.

The Board re-assembled at 1000 on 24th July 1951.

Captain (E) Norman John Hycinth D’ARCY, Royal Navy, H.M.S. DOLPHIN called and Examined by the Board.

  • Q.744. Are you Captain (E) Norman John Hycinth D’arcy.

    A. Yes, sir.

Witness was cautioned in accordance with K.R. and A.I. Article 488 paragraph 9, as amended.

  • Q. 745. What is your present appointment?

    A. Fleet Engineer Officer on the staff of Flag Officer Submarines.
  • Q.746. When did you take up that appointment?

    A. 15th October 1950.

Q.747 to Q. 752 omitted.

  • Q. 753. Do you feel consequent on what we know and the hypothesis of Flag Officer Submarines concerning the loss of the AFFRAY that an automatic shut off for the snort hull induction valve is desirable?

    A. I would say that no attempt should be made to fit an automatic shut off to the hull induction valve, that should remain as it is as a telemotor operated valve controlled by a man , but I feel that if the hypothesis that it was impossible to get at this control was in fact the trouble in AFFRAY, the only way of preventing it , in my view, would be to have an automatic method of shutting some valve and I would prefer to see such an automatic arrangement fitted to the emergency flap valve. The hull induction valve would remain as it is, a manually controlled valve.

Authors Note:

This evidence confirms that the telemotor hull valve was fitted to "A" class submarines before the loss of the AFFRAY , and that the existing induction pipe flap valve was made automatic after the disasaster , as described below by Chief Mechanician Keith Hallam , who served earlier in his career on "A" class submarines , but quite some years after the AFFRAY loss in 1951.>>>

The emergency flap valve was an automatic shutting valve. The force of water on the face of the flap created torque on the spindle. The spindle was connected to a lever on the outside of the pipework. The lever was about 2ft long with a knob about 2" diameter on the end. A few inches above the knob there was a hole about 1" diameter through the lever shaft, which was itself about a half inch thick. When the EFV was pulled to the open position the lever shaft passed through a slot in a 'detent'. This detent had a spring loaded ball that engaged with the 1" hole in the shaft. The spring tension was powerful and could be adjusted. When opening the EFV the shaft had to be pulled into the detent with a full force rapid movement to engage the ball in the hole. A full flow of water overcame the detent tension and the EFV slammed the flap to a nearly shut position. Because the EFV flap didn't completely shut off flow, the head of water quickly drained down into the snort drain tank. The Killick stoker watch-keeper on the platform would be watching the depth gauge and would be pulling the EFV open as the snort head neared the surface. You have to remember that the snort head float valve was also opening and shutting and was supposed to actually stop any water coming down the snort tube. The later enclosed float head design was better at this.

Cheers, Keith



This form is for you to comment on, or add additional information to this page. Any questions will be deleted. If you wish to ask a question or otherwise contact the Branch or the Webmaster. Please use the Contact Us page or ask your question on our Facebook Page

Please insert the result of the arithmetical operation from the following image:

Please insert the result of the arithmetical operation from this image. =


Note: All submissions are subject to webmaster approval prior to appearing on the page. As a SPAM prevention measure, any comments containing links to other sites will be automatically discarded

Origins Of The Amphion Class SubmarineSnorkel in the US Navy - 1945 onwards