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Chief S/Ms theory about the loss of the Affray

By Peter D Hulme

This is a recollection, of a conversation I had with the Chief Stoker Mechanic of HMS Amphion in 1954, when I was the (rather younger) PO Electrician in charge of the electrical propulsion and maintenance of 220 vdc electrical machinery, but in particular the propulsion battery. I had a staff of one Leading Electrician's Mate and two Electrician's mates. These three Electrician's Mates operated the motor switchboard, keeping a 24 hour watching keeping roster in the Main Motor Room responding to the telegraphed speed instructions for the Control Room. All three would be in the motor room during Diving Stations and with me as the Petty Officer in charge. Affray had a similar motor room team at the time she was lost.

The Chief S/M was a senior mess mate of mine and good company,who kept up the spirits of the crew in bad times. He had a significant number of medals from WW2.

I spoke to him after the submarine recovered from a serious bow down angle after a 'dip' under the surface while snorting that closed the snort head valve and pulled a vacuum and we stopped snorting. I was concerned about the action I had taken when the angle got to the point where the stokers were losing their hold and sliding down the engine aisle towards the platform and the people in my charge in the motor room would soon lose their ability to operate the heavy switchgear and so contrary to the Ahead on the telegraphs, I ordered Astern. This was intuitive as the RN has no policy on using the electric motors astern to act as a brake in bow down angle situation, as did the USN: it was only in later years that I read the USN manual and of the other severe bow down angle situations such as the USS Chopper.

The Chief S/M's position at diving stations was in the control room and I him asked if anybody had noticed that the tachometer had gone from ahead to astern? I was aware that I had technically disobeyed an order (the telegraphs) in ordering Astern, and as young man with a wife and baby, could not afford any charge that might result in a loss of income. He assured me they were all too busy hanging, on watching the moving depth gauge to notice the tachometer and I should just forget about it.


Click to expand image

The conversation somehow moved on to the loss of the Affray , some three years earlier and he explained that when snorting he always ensured the fuel tanks external to the pressure hull of the submarine were used, not the internal tanks shown in the diagram above. Listed at the end of this article are all the fuel tanks in A Class submarines of 1950 and the diagram above shows those related to the Chief S/Ms theory about the loss of the Affray.

In an RN submarine, the 1st Lt was responsible to the Captain for maintaining the 'Trim', that is the fuel, lube oil and water tanks were adjusted to balance the submarine in an level position when submerged. All men,weapons and stores etc, had to be allowed for and the Chief S/M was responsible for the measurement of the tank contents being measured and the results presented to the 1st Lt to include in his Trim calculations, and then make adjustments required by the 1st Lt to finalise the Trim calculations, that will then be confirmed by a Trim Dive on leaving harbour, before proceeding on patrol.

This all demonstrates that a submarine Chief S/M had to be a skilled man, with a complete knowledge of the submarine and the various tanks and compartments that formed its construction. In particular he had to pay attention to the state of the many diesel fuel tanks as the engines consumed their contents, with the fuel oil being replaced by sea water as will be described later. He also supervised the fuelling, that is the filling of the various fuel tanks from a fuel lighter or Submarine Depot Ship. An important job as sadly demonstrated by the sinking of the Artemis alongside the pier at HMS Dolphin while fuelling from a Lighter in 1971.

I think the foregoing provides sufficient background to take seriously, the Chief S/M's view on the cause of the mysterious loss of the Affray in 1951 in the English Channel where she still rests. She was a sister ship of the Amphion I mentioned previously and the Artemis that I served on from February 1950 until April 1951. The Artemis and Affray were in the both in the 5th Submarine Flotilla (later Squadron ) based at HMS Dolphin, Gosport, Portsmouth and accompanied us, Artemis, on ship visits during the summer of 1950.

Before proceeding further I wish make it clear that if the 'theory' has validity then it was a systems failure on the Affray, not a Command or crew failure, as has so often been the case in modern aircraft system failures where the competent crew were unable to save their aircraft.

I am also advised by a former Chief Mechanician who had a long career in Royal Navy diesel and nuclear submarines, but commencing some years after the Affray loss; that when he was a PO Stoker Mechanic on Amphion (1962), the practice was not to use internal fuel tanks while snorting. Whether Submarine Fleet Orders were issued at some time after the loss of the Affray, I don't know. It may be that when the Amphion Chief Stoker Mechanic in 1954, was explaining the internal tank situation to me, I failed to understand that he was not just describing a policy he uniquely applied aboard Amphion 1954, but was acting on a Fleet Order that was of recent origin. I am unfortunaely, not in a position to search the TNA for a possible Fleet Order banning the use of the internal fuel tanks while snorting, in particular the A Class submarines, perhaps issued some time after the loss of the Affray. Also I am not aware that the matter of using internal fuel tanks was raised at the Affray Inquiry, in particular it doesn't seem to been discussed when the Captain (E) of FOSM and the Engineering officer of the Artemis gave evidence regarding a severe stern down angle experience by this submarine.Incidentally I was serving in the motor room of the Artemis at the time of this incident and involved in cleaning out the oily bilge water from electrical reducer MG set and steering motor. I eventually collapsed due the fumes of the carbon tetrachloride we were using as well as distilled water. I taken to the control room to recover, the submarine by now surface and induction air being drawn in.

To continue with the Chief S/M's theory, it was based fact that the tanks were all self-compensated as had been the case in RN since WW1. Internal or External. As I understand the fuelling system, the open sea is allowed to fill the empty tank from the bottom. Then the fuel oil is pumped into the top of the tank forcing the water out of the tank bottom until it is determined the tank is full of fuel (there being tap-off measurement points to determine the level of the oil /water.)

In essence the fuel oil floated on the water and took up the pressure of the sea water, forcing the fuel oil along a pipe to the fuel system in the Engine Room. That is how I recall having explained to me in 1949/1950 at the submarine school. This is supported by the fact that while serving as an electrician, I cannot recall a separate electrically powered fuel pumping system and the fact that there were quite a lot of fuel tanks, both inside the hull and outside (listed below).

My diagram above is based on the basic Official Drawings used in the Alliance book - 1986 (by John Lambert and David Hill. In addition self-compensated fuel tanks have been in use in the RN since at WW1 with varying arrangements, unfortunately the last submarine described is the S Class designed in the 1930's, but in service, with various changes until the 1960's, limiting its value in reference to determining the detail of the A Class designed in WW2.

The Naval Architects of the A Class submarine are widely thought to have designed the submarine to meet the Admiralty's need for long range operation on the surface in the war in the Pacific, often at high speed, having two large super-charged diesel engines. This would require a substantial fuel capacity and it is useful to recall the Cube Law that applies to all ships; to double the speed of a ship requires an eight-fold increase in power and thus fuel.

In view of the Royal Navy's lack of interest in Snort during WW2, it is reasonable to assume they made no allowances in the overall A Class design detail that anticipated a snort would be fitted at war's end. The first A Class, Amphion, left the yard and completed commissioning trials just before war's end. It is said the Amphion was in the Suez Canal when the war in the Pacific ended.

It is worth noting the Dutch experimented with two successful snorting submarines early in the war, but the RN (and the USN) showed no interest until later in the war when the U-Boats started to be fitted with snort and when Allied aircraft and radar changed the course of the U-Boat campaign firmly in the favour of the Allies. This change in submarine warfare must have been noted by the various officials associated with submarine design in the RN

The first working snort system was not fitted in a British submarine until after the war in 1946 and the first A Class in 1947. Some of the last of the A Class left the Builder's Yards in the 1947-1949 period fiited with an early design of combined induction and exhasust mast, that was then changed to the seperate masts.

The records show the Affray was launched in 1945 and commisioned in November 1945 and about two years later was fitted with what became standard in all A Class: the seperate induction and exhausts masts. This short review of the A Class and snort, tends to support the view that Affray was not designed and built with any intention of later fitting snort. thus had no special layout of fuel tanks or piping for snorting, but rather for the long range surface operations in the war in the Pacific that ended so abrubtly. (See Snorting In The RN )

A review of the design of the "P&O" classes (the first commissioned in 1958) shows significant differences from the A Class in the placement of the Fuel Tanks in the quite a different hull. Hence there is really is no substitute for a skilled study of the construction and piping plans of the A Class itself, fortunately with an actual boat to examine, preserved at Gosport. Certainly some discrete dockyard alterations may have been made since the Affray investigation in 1951, but there are practical limits to alterations and I noticed nothing drastic happening to Amphion during the major refit in 1953, though I must emphasise I was an electrician.

So having set the scene as it were, this is the theory

The Affray is snorting in mild sea conditions and one can assume that as was usual, a modest running charge was taking place while snorting just to top-up the battery. The submarine loses trim, taking a bow down angle (just we had in Amphion and earlier, Stern down in Artemis ). The Snort Head valve closed stopping the mast from flooding. The submarine is working on the internal fuel tanks and as she gets deeper the pressure in the internal fuel tanks rises, placing increasing forces on the structure within which the tanks are fitted, as shown in the diagram above. As the submarine goes deeper the pressure increases until structural damage occurs.

Drastic structure failure did not necessarily take place, such the that severe flooding occurred, but serious cracking perhaps did and this allowed significant amounts of sea water to fill the small open volume of the battery tank (full of cells!) until the sea water got into the acid of the cells, resulting in significant amounts of Chlorine gas to being generated, that would then be taken by the battery ventilation system to the outlet in the Engine Room, with no engines running, to extract the fouled air.

The sea water contamination scenario has to be modified to allow for the fact that submarine was probably at a steep bow down angle and the sea water level at the forward end of the battery tank would be much deeper than the after end. This would result in the salt water creating cell terminal short circuits, with consequences I am not clear about, except that it raises the serious possibility that there was excess current built up that would have been sufficient to blow the battery fuses.

The No. 2 Battery would still be functioning, unless a serious study reveals unanticpated consequences. Similarly the Battery Fans would still running.

It is worth noting the so called Hotel Load on the battery when on the surface with no electric motors running, imposes a fairly large, more or less continuous discharge and when ever the engines are running, in suitable operational circumstances, the motors (as generators) take over the Hotel Load and supply a modest charge in addition to propelling the submarine: in these circumstances, the practice was to start the battery ventilation as there was always some hydrogen gas produced and in some cells more than others.

The construction of the No 2 Battery Compartment was quite different to the No. 1, in that the cell sat on stepped shelves set on the lower half-round of the pressure hull, with an internal fuel tank No. 5 (4024 gals) in much the same position as Nos. 1&2 in relation to No. 1 Battery tank, but in No. 2 Battery Tank, the bulkhead is actually one of the main dividing bulkheads of the submarine and presumably much stronger than that of the tank dividing, short bulkhead forward of No.1 Battery tank. While there is room for study of No. 2 Battery Tank, my recollection is that the Chief S/M was only referring to the No. 1 Battery Tank.

According to the drawings in the Alliance book, the No. 5 Internal Fuel Tank was later divided longitudinally to create aft a small No. 5 Fuel Tank and forward, two smaller tanks that I believe were to better manage the snort induction inlet spray and the oily bilge water in the Engine Room (refer to bow angle Artemis evidence by Captain (E) Darcy given at the Affray Inquiry June 1951). I assume these alterations were part of the major work of streamlining all the A Class in the late-fifties bar one, supposedly unfit, but still in service for some years.

To Conclude

The diagram of the basic hull and tankage is reliable, but no output piping is shown going to the fuel system in the Engine Room; with such things as the Snap Tank, as I don't think the fuel output system is relevant to the 'theory'. I do not know now where the sea water inlets were on the various self-compensated fuel tanks or if the inlets had any sophisticated control to limit the water inlet pressure applied to the tanks. The plans of the A Class would need reviewing with an expert eye to determine such detail.

In my opinion the Chief S/M's theory is worth at least a preliminary investigation by a naval architect with submarine experience, who has available the detailed hull and piping plans. Especially in these days of complex computer modelling.

A Class submarine fuel tanks listed follows:

  • Forward internal – No. 1 (4465 gals), No.2. (4465 gals). No.3 (1795 gals), No.4 (1950) gals.
  • Aft internal (no number) 3135 gals.
  • Port Forward external – No.1 (2505 gals), No.2. (3420 gals).
  • Starboard Forward external – No.1 (2505 gals), No.2 (3420 gals).
  • Port Aft external – No.3 (4040 gals). No.4 (2790 gals).
  • Starboard Aft external - No. 3 (4040 gals). No 4. (2790 gals).
  • Ballast tanks when used for fuel. Port No.4. (7205 gals). Starboard No.4 (7205 gals).

Additional Notes

1. From Keith Hallam, retired Chief Mechancian RN 15-6-2017

Extract from E-mail discussion.

We only ever used internal tanks on the surface. Never ever when snorting. In fact on any trip it was a case of using up the fuel in 4 main ballast kingston tanks first and then the aft external fuel tanks. We had usually refuelled before we got around to using the internal tanks. I always used the aft internal fuel tank when running the engines alongside.

Note this is quite some years after the loss of the Affray

2. The preserved Alliance is obviously of great value in any investigation as one can assume the critical parts of the main construction are still the way they were when she came out of the builder's yard, allowing they came out of the yards of different builders.

3. The reference to the article on Snorting in the RN may be of some value, particularly the diagram of the Battery Ventilation System.

4. In the book Subsmash, that I reviewed chapter by chapter. There is a reference to battery gas explosions and this being a possible cause of the loss. In later years I have read reports of battery gas explosions in A Class submarines some involving fatalities and serious injuries. I don't have a detailed list, but gained the impression that these events occured in the long period of service after the A Class were streamlined starting in the later-fifties and larger capacity cells installed in the original battery space, this increase heat and gas. I recently recieved a copy of the A Class Electrical Manual annotated that it was ammended in 1967, and the original cell capacity as been over written with 8000 ampere hours at the five hour rate. The original rating as-built was 6630 ampere hours at the 5 hour rate, apparently about a 22% increase, with a consequent increase in hydrogen gas emmission when over-charging with same ventilation system. This increase in cell size came well after the loss of the Affray. So despite battery explosions having occurred in the later service life of the A Class life, there have been no reports of serious structural damage to an A Class submarine and after Affray, went on to give long service to the Royal Navy.

5. Interrogation of U-Boat Survivors - Cumulative Edition June, 1944

(ii) Fuel tanks: The fuel tanks in a U-boat are self compensating. That is they are always open to the sea at the bottom. The fuel is taken from the top of the tanks, and as it is used, so its place is taken by sea water. Both internal and external ballast tanks are provided. The external tanks like the fuel tanks are permanently open to the sea at the bottom. The internal tanks have large valves in the bottom known as Kingstons. These Kingstons are always open when at sea. At the top of these tanks are vent valves and high pressure blow valves. The vents open to the outside of the boat and let air out when the tanks are being flooded. In the RN Kingstons are hydraulic (telemotor) operated valves, usually in the bottom of certain tanks. They are usually quite large.

6. The breaking of the snort mast has been generally believed to be caused by the forces generated by the impact of the hull on the sea bed and the recovered part of the mast was in 1951, thoroughly examined and an expert report issued to the Board of Inquiry. The report does not appear to offer the snort breaking as a probable reason for the loss. However the examination of the Affray mast and the masts of other A Class submarines revealed areas of inferior welding, However numerous photographs of the broken snort do not appear to show, at the site of the break, that there is any welding of the two pipes that form the mast or failure of the welding of the fairing plate that joins the two pipes. The photographs of the mast can be seen in my article on Snorting in the RN


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