Winston Churchill did not believe that low fuel was the reason why HMS Glorious was allowed to transit back to the UK ahead of the main convoy.
Furthermore, the documentary on HMS Glorious also sheds doubt on the Navy’s reason for Glorious returning to the UK ahead of the convoy that departed a day later.
Here is a transcript of the fuel debate from the documentary
Narrator: “A parliamentary statement said Glorious was sent ahead because she was short on fuel. But many believe this was cover for a more embarrassing explanation”
Narrator: “The head of the Naval Historical Branch today, firmly supports the official version”
NHB: “I believe it completely. She sailed eight days earlier. She was a very very short legged and short ranged ship. She had been hanging around in the Narvik area unrefuelled while she was there. She was going to be extremely short of fuel”
Narrator: “When Glorious left Scapa flow on the 31st of May its accepted she had full tanks of three and a half thousand tons (shows 3550). Sailing with Ark Royal she did the 1000 mile journey to Harstad at 17kts as noted in Ark Royal’s log. That used some 650 tons of fuel. For 3 days in the next 6 at Admiral Wells express order, Glorious was detached to conserve fuel. For the other 3 days. The two carriers kept together averaging 15kts though faster when glorious was flyinga aircraft on and off. But even deducting another 15% for error, Glorious would have atleast 1200 tons of fuel, more than enough to wait and return with the other ships”
Narrator: “The arithmetic suggested she still had plenty of fuel””
NHB:” What do you mean by plenty of fuel?”
Narrator: “Enough to stay with the convoy”
NHB: “And yet I have not done that particular sum myself”
Narrator: “How can you be so shore then that the Admiralties arithmetic is correct?”
NHB: “The admiralties arithmetic is correct because I’m satisfied that the amount of time she was away and you take the endurance figures . There is no other sensible explanation for it”
Here we will examine the ‘Low Fuel Scenario’ that the Navy has put forward as the reason why HMS Glorious was returning.
For this section of my research I have utilized feedback from experienced mariners, historic ship curators and historians to try and develop the most comprehensive and unbiased assessment of Glorious‘ fuel consumption.
From my research I have become aware of how negative the perceptions are to the “fuel shortage” reasoning put forward by by the Navy. I’ll openly admit I found this idea “unrealistic” to start with but forced myself to “un-trench” my opinions and pick apart the low fuel scenario which is detailed below.
Info on the ships
| Vessel | Bunkers | Max Range |
|---|---|---|
| HMS Glorious | 3800 Long Tons ( 3900 tons) Documentary 3550 tons | 6,630 nmi (12,280 km; 7,630 mi) at 10 knots (19 km/h; 12 mph) |
| HMS Ark Royal | 7,600 nmi (14,100 km; 8,700 mi) at 20 knots (37 km/h; 23 mph) |
HMS Glorious and HMS Ark Royal’s maximum theoretical ranges are separated by 1000nm with Glorious‘ shorter range calculated at just 10kts and Ark Royal’s greater range calculated at a much higher 20kts. Glorious‘ range would be reduced if she went faster than 10kts.
Ark Royal was a purpose built carrier that entered service in 1937 was 240m long with a beam of almost 29m and and a displacement of 27,720 (deep load). In contrast HMS Glorious was a converted cruiser laid down in 1915 and later converted during the inter war period. As a carrier she was roughly the same length of Ark Royal but with a beam of 24.7m, 4m narrower than Ark Royal. She displaced 22,360 tons (deep load)
The capabilities of both vessels were markedly different and it is safe to say, as noted by the Historical Branch in the Glorious documentary above, that in comparison with Ark Royal, HMS Glorious had ‘short legs’
Lets look at Glorious‘ fuel consumption
The last surviving fuel records for HMS Glorious are from March 194 and were kindly supplied by Tim Slessor (also included in his fantastic book “Lying in State”) and give the following values:
- 12kts = 5.6 tons/hour
- 14kts = 7.3 Tons/Hour
- 16kts = 9.4 Tons/Hour
- Extrap: 10.5 Tons/17kts
- 18kts = 11.75 Tons/Hour
- 20kts = 15 tons/Hour
Expanding on this we can develop a fuel consumption curve as shown below . This curve has extrapolated beyond the known values supplied by Slessor.
Using basic maths we can calculate the fuel consumption, based on the fuel figures provided by Slessor and the number of hours that Glorious was away from Scapa i.e 201 hours (8 days, 9 hours, 30 minutes).
This time period is based on a departure from Scapa Flow of 0800 on the 31st May up until her loss at approximately 17:30 on the 8th June). It is worth noting that this does not include any time zone changes that may have occurred but this value would only attribute to 1-2 hours fuel consumption.
- 201hours @ 12kts = 5.6 tons/hour =1,125.6t used, 2674.4t remaining
- 201hours @ 14kts = 7.3 Tons/Hour = 1,467t used, 2333 tons remaining
- 201hours @ 16kts = 9.4 Tons/Hour = 1,889.4t used , 1910.6 tons remaining
- 201hours @ 18kts = 11.75 Tons/Hour = 2,359.74t used, 1440.26 tons remaining
- 201hours @ 20kts = 15 tons/Hour = 3015t used, 785 tons remaining
As mentioned above, these consumption values are only until Glorious was sunk.
Now let’s look at what she would have burned if she had made it back to Scapa Flow
Assuming HMS Glorious was returning to Scapa flow using Admiral Well’s routing it would take her approximately 58hrs to make the homeward journey from Lofoten.
Based on this transit time we would have an estimated arrival time of 13:00 on Monday, 10 June 1940.
On arrival back in Scapa she would have been on deployment for 10 days, 5 hours (245 hours)
- 245 hours @ 12kts = 5.6 tons/hour =1,372t used, 2428t remaining = 63% remaining
- 245 hours @ 14kts = 7.3 Tons/Hour = 1778t used, 2022 remaining = 53% remaining
- 245 hours @ 16kts = 9.4 Tons/Hour = 2,303t used, 1497 remaining = 39% remaining
- 245 hours @ 18kts = 11.75 Tons/Hour = 2,878.75t used, 921 remaining = 24% remaining
- 245 hours @ 20kts = 15 tons/Hour = 3765t used, 35 remaining = 1%
The convoy which, hypothetically Glorious should have been a member or arrived safely back in the UK (Clyde) on the 12th June, 4 days after HMS Glorious departure from Lofoten independently.
Lets calculate the fuel consumption if Glorious had transited back with the convoy but broke off when in the vicinity of Scapa i.e not continuing to the Clyde with the merchant ships. Based on this assumption she would have arrived at Scapa on June 11th and only burnt an extra 24-30hrs worth.
Lets assume she was at sea for an additional 25 hours.
- 270 hours @ 12kts = 5.6 tons/hour =1,512t used
- 270 hours @ 14kts = 7.3 Tons/Hour = 1,971t used
- 270 hours @ 16kts = 9.4 Tons/Hour = 2,538t used
- 270 hours @ 18kts = 11.75 Tons/Hour = 3,172t used
- 270 hours @ 20kts = 15 tons/Hour = 4050t used
On the basis of previous consumption rates and deployment duration it would be easy to throw out the low fuel reasoning provided by the Royal Navy.
If Glorious had been averaging 18kts throughout her entire deployment to Lofoten then the ship will be approaching a low fuel situation but this would not have affected her returning with the convoy.
However, Glorious’ fuel consumption figures should be treated with caution as they were obtained during March 1940 when HMS Glorious was operating in the Mediterranean between Malta and Alexandria. and not the Norwegian Sea.
We will come back to the importance of these differences shortly.
But firstly, lets consider HMS Glorious actions from May 31st 1940 until here loss on the June 8th,
| Day | Date | Notes | Estimated Speed | Fuel Burnt |
|---|---|---|---|---|
| 1 | 31 May | 31st May 0800 Ark Royal and HMS Glorious Set Sail at 0800hrs on the 31 May, Transit to Norway. Most likely Zig-Zagging 31st – At 0600 ARK ROYAL, ACASTA, ARDENT and ACHERON arrived at Scapa. At 0800 ARK ROYAL (Flag Vice Admiral, Aircraft Carriers) and GLORIOUS escorted by the destroyers HIGHLANDER, DIANA, ACASTA, ARDENT and ACHERON sailed from Scapa for Operation ALPHABET. Course was set to pass west of the Orkneys. Between 0925 and 1630 ARK ROYAL’s Swordfish carried out A/S patrols. At 1015 in position 59N, 04-20W, ARK ROYAL flew on Skuas of 803 Sqd from RNAS Hatston together with two replacement Skuas for 800 Sqd, these latter two were the aircraft that failed to find ARK ROYAL on the morning of 30/5/40. On completion, course was set to the Northward, to proceed towards the Narvik Area. Calculated speed of advance 17kts, excluding time taken for aircraft ops | 18kts for an advancement speed of 17kts while zig zagging and making 96% Distance made good | |
| 2 | 1st June | Transit to Norway 1st – At 0730 ARKROYAL was in position 64-50N, 02-40W and steering northerly, the weather was foggy and the fog persisted intermittently throughout the day. At 2201 the Flag Officer Aircraft Carriers signalled the Flag Officer Narvik with an RV position for 1700/2/6/40, for a Walrus bringing out orders for Operation ALPHABET Calculated speed of advance 17kts, excluding time taken for aircraft ops | 18kts for an advancement speed of 17kts while zig zagging and making 96% Distance made good | |
| 3 | 2nd June | Transit to Norway 2nd – ARK ROYAL continued steering northerly and maintained ADA patrols during daylight hours. At 1710 ARK ROYAL was in position 68-58N, 00-33E when she landed on a Walrus from Narvik. At 1748 the destroyers ARDENT and ACASTA were detached to refuel at Harstad. At 1825 ARK ROYAL flew off the Walrus to return to Narvik | 18kts for an advancement speed of 17kts while zig zagging and making 96% Distance made good | |
| 4 | 3rd June | 3rd – At 0730 GLORIOUS and HIGHLANDER were detached to the northwest, to conserve fuel until required for embarking shore based aircraft. At 1002 The Flag Officer Narvik signalled; operation ALPHABET is to start tonight, Monday, without further orders. At 1600 ARK ROYAL was in position 71N, 12-56E and flew off two Swordfish 4K & 4C of 820 Sqd for an ADA patrol. Searching sector, 130¡ to 180¡. At 1700 the ACASTA and ARDENT rejoined from refuelling. Following which DIANA and ACHERON were detached to Harstad to refuel. At 1700 Deck landing practice for new pilots carried out. At 1835 ARK ROYAL flew off two Swordfish 2P & 2Q of 810 Sqd for an ADA patrol. Searching sector 130¡ to 180¡ At 2050 ARK ROYAL flew off two Swordfish 4A & 4B of 820 Sqd, 4B for an ADA patrol, searching sector 130¡ to 230¡, and 4A for a weather reconnaissance over Narvik. At 2230 ARK ROYAL flew off two Skuas 6B & 6C of 800 Sqd for a fighter patrol over the troop transports. Aircraft 6C returned soon after taking off with undercarriage jammed in the down position. At 2337 ARK ROYAL flew off two Swordfish 4G & 4H of 820 Sqd, 4G for an ADA patrol, searching sector 130¡ to 230¡, and 4H for a weather reconnaissance over Narvik | 14-16kts while conserving fuel to the Northwest. During this period Glorious would also deploy her own aircraft for protection | |
| 5 | 4th June | Conserving fuel | 14-16kts while conserving fuel to the Northwest. During this period Glorious would also deploy her own aircraft for protection | |
| 6 | 5th June | Lofoten Islands Glorious returns to be with Ark Royal while the destroyer Highlander is off being refueled | 14-26kts | |
| 7 | 6th June | Lofoten Islands bombing raid on Dietls HQ. Aircraft returned due to bad weather. Highlander rejoins and Glorious/Highlander head North to conserve fuel | 14-16kts | |
| 8 | 7th June | At 1330 in position 71-11N, 15-25E, GLORIOUS and HIGHLANDER rejoined the Flag from the Northwest. Cross flies out to Glorious in a Walrus to confer with D’Oyly-Hughes 1430 Four swordfish deployed to Bardufoss to guide fighter aircraft back to to Glorious At 1930 GLORIOUS landed on three Hurricanes of 46 Sqd RAF as a trial to test the feasibility of landing Hurricanes without arrester hooks on a carrier. The aircraft landed on very successfully, and it was decided to embark the remainder in GLORIOUS a.m., tomorrow, Saturday At 2035 GLORIOUS flew off a Swordfish of 823 Sqd to Bardufoss with instructions for landing on remaining RAF fighters | 16/17kts | |
| 9 | 8th June | Transit Home By 0115 GLORIOUS had landed on ten Gladiators of 263 Sqd RAF, (the first Gladiator had taken off just after 2300/7) followed by seven Hurricanes of 46 Sqd RAF, all from Bardufoss, and one Walrus of 701 Sqd FAA, ferrying Group Captain Wood, RAF from Harstad. All landings were completely successful. GLORIOUS then landed on the Swordfish of 823 Sqd that had acted as navigating aircraft. Walrus landed and departed Glorious At 0300 in position 70-17N, 14-10E, GLORIOUS, ARDENT and ACASTA detached for Scapa. Glorious initially advances at 22kts before reducing to 17kts a few hours later Lost in the evening of June 8th 17:30 ~(UK Time) | 18kts for an advance speed of 17kts while zig zagging and making 96% Distance made good |
Additional Considerations
As mentioned above there are some other considerations when comparing the previous fuel consumption rates from the Mediterranean Sea to probable consumption rates in the Norwegian Sea
In Malta the Average annual sea surface temperature is 20 °C (68 °F) (the highest annual sea temperature in Europe), from 15–16 °C (59–61 °F) in the period from January to April to 26 °C (79 °F) in August. In the 6 months from June to November, the average sea temperature exceeds 20 °C (68 °F).
In Alexandria, the Average annual sea surface temperature on the coast is 25.5°C, by the seasons: in winter 23.8°C, in spring 25.8°C, in summer 25.7°C, in autumn 26.7°C. Minimum water temperature (22.3°C) in Alexandria it happens in February, maximum (28.5°C) in May. The seawater in the part of the world also has a very high salinity value of 38 psu (average). This would give a seawater density of 1025.6 (kg/m3)
In comparison the Norwegian Sea of Lofoten Islands, in the Artic Circle would have been a significantly colder at around 6.5*C (Taken from Ark Royal’s log) with a much lower salinity value of around 35psu – this would give a seawater density of approximately 1027.4 (kg/m3)
Why is this important?
Although contrary to how it would seem, very cold saltwater is more buoyant than warm salt water. Cold water, like the 6*C water encountered in Lofoten is a lot denser than the warm water encountered by Glorious in the Mediterranean. The denser a liquid is, the higher you, or in this case a ship will float in it
Varying water temperatures will affect a ship’s draft, because warm water is less dense than cold water, providing less buoyancy. In the same way, fresh water is less dense than salinated or seawater with the same lessening effect upon buoyancy.
This is one of the reasons a ship has a plimsol line. For more info on Plimsol lines click HERE
So in the Mediterranean HMS Glorious would have probably sat slightly deeper in the water. However, during operations in the Norwegian Sea she would sit slightly higher in the water ( a smaller wetted area)
This difference may only be a matter of a few feet but any additional exposed area of the hull would present a bigger area to catch the wind and this is important as the windspeed in the Mediterranean during March is very different to the windspeed encountered off the Lofoten islands in June.
Lets assume that the difference between Med and Norwegian loadings on Glorious was 1m, along her 239m hull this would generate an additional 2,572 feet2 of surface area above the water on each side.
The mean windspeed around Malta and Alexandria is approximately 4-5.5m/s or 7.7-10.6kts with less intensties experienced closer to shore.
However, Ark Royal’s Log shows the weather observations around Lofoten typically fell within the Beaufort 4-6 range. or 11-27kts of wind. With Beaufort 5 being around average (17-21kt)
Based on this data we have a ship that is probably sitting slightly higher in the water, operating in denser water and exposed to almost double the mean windspeed commonly encountered in the Mediterranean. The increased wind encountered in Norway will also create more waves which, in turn, will create more resistance.
In this instance using the fuel calculation from the Mediterranean Sea will not adequately represent the conditions in the Norwegian Sea.
Vessel fuel consumption has become a ‘hot topic’ in recent years with climate change and the variation of oil prices. A number of studies have looked at predicating fuel consumption by vessels and attempting to make accurate predications for both environmental and cost studies. The procedure for estimating a fuel consumption curve prediction is given below.
The diagram shows that there is a lot more to fuel consumption than simply taking a previous set of fuel consumption readings and applying them to a future voyage without considering several external variables.
So lets put those factors together
Added Resistance Due to Waves
Added resistance due to waves refers to ocean waves caused by wind and storms, and is not to be confused with wave making resistance.
Ocean waves cause the ship to expend energy by increasing the wetted surface area of the hull (added viscous resistance), and to expend additional energy by rolling, pitching, and heaving. This component of resistance can be very significant in high sea states.
In the area of operations around Lofoten, the conditions were generally between Beaufort 4 and 6 which is aquatints to “Small waves becoming longer; fairly frequent white horses” (Force 4) and “Large waves begin to form; the white foam crests are more extensive everywhere; probably some spray” (Force 6)
It is probable that Glorious would expend additional energy/fuel during these periods of higher sea states than the average sea state experienced in the Mediterranean during March.
It is likely that outside of flight deck operations, Glorious would conduct zig-zagging maneuvers to reduce the likelihood of a successful u-boat attack. It would be foolish to think that Glorious would simply “hove to” in a war zone, head to wind, with known aircraft and u-boat threats. As Glorious zig-zagged she would present different profiles to the wind, some of these profiles would be beneficial to fuel consumption and others, would be negative.
Increased fuel consumption by a vessel in various Beaufort states has been studied in numerous papers and the figure below (On the estimation of ship’s fuel consumption and speed curve: A statistical approach) shows a substantial increase in fuel consumption in Beaufort 6 compared to lower sea states.
The data displayed below is from “Gentle Leader” operated by NYK. This vessel is 199m long with a beam of 32m. This makes her shorter than Glorious but with a greater beam. The ships DWT is 21122t. HMS Glorious would almost certainly experience similar if not more significant effects from higher sea states
Wind and Current Resistance
The environment surrounding a ship can have a significant impact on ship resistance. Wind and current are two of the biggest environmental factors affecting a ship. Wind resistance on a ship is a function of the ship’s sail area, wind velocity and direction relative to the ship’s direction of travel. For a ship steaming into a 20-knot wind, ship’s resistance may be increased by up to 25-30%.
The general conditions around Lofoten during this period were betwee Force 4 – 6 which is a Moderate (11-16kts) to Strong Breeze (22-26kts). The periods of higher wind velocity would result in greater consumption of fuel by Glorious
Fuel consumption in higher sea states has been studied at great length. The figure below was taken from ” On the estimation of ship’s fuel consumption and speed curve: A statistical approach” – Nicolas Bialystocki, Dimitris Konovessis
We know that conditions around Narvik experienced higher wind velocities with moderate to strong breezes. This would greatly increase resistance against a big, steep side ship like Glorious and result in greater fuel consumption.
As a hypothetical example, lets just assume that Glorious had a hull area of 239m long x 10m high e.g. 2390m2
For a stationary vessel with 5kts (2.5m/s) of wind on the beam, air density of 1.2, this would result in a dynamic pressure of 3.75 N (newtons)/m2 (0.3kg/m2), or total wind load on Glorious of 8963N (913kg) . In a 25kt scenario this would increase to 93.8 N/m2 (9.56 kg/m2) dynamic load and a wind load of 224,063N (22,848KG) on Glorious. There certainly is a big difference in wind loads from just under 1 ton of load to 22 tons.
Conversely the increased windspeed may benefit aircraft operations. The Fairey Swordfishes had a landing speed of around 40kts which meant they were practically hovering aboard a carrier that was making 20kts into a headwind.
Ocean currents can also have a significant impact on a ship’s resistance and the power required to maintain a desired speed. Steaming into a current will increase the power required to maintain speed. For instance, the Kuroshio Current (Black Current) runs from South to North off the coast of Japan and can reach a speed of 4-5 knots. What is the impact of this current? For a ship heading south in the current and desiring to travel at 15 knots it is not uncommon to have the propulsion plant producing shaft horsepower for speeds of 18-19 knots.
Without a doubt the Lofoten area is affected by the Norwegian Current with current velocities of around 1 to 2kts (and locally higher).
These currents will ultimately have an effect on Glorious performance with positive effects when running with the current and negative fuel effects when running against it
Due to the westerly routing of HMS Ark Royal and Glorious the benefits of the Greenland current out to Narvik and its hinderance on the way back may have only been experienced in the last day of steaming.
Conversely, in the Mediterranean , HMS Glorious would have sat slightly lower in the water. As there was little surface current acting upon this hull (unlike Norway) the affects would have been minimal and even if she sat marginally higher in the Norwegian Sea, the currents acting against the hull would have much much greater effect.
Air Resistance (RAA)
Air resistance is the resistance caused by the flow of air over the ship with no wind present. This component of resistance is affected by the shape of the ship above the waterline, the area of the ship exposed to the air, and the ship’s speed through the water. Ships with low hulls and small “sail area” or projected area above the waterline will naturally have less air resistance than ships with high hulls and large amounts of sail area. Resistance due to air is typically 4-8% of the total ship resistance, but may be as much as 10% in high sided ships such as aircraft carriers. Attempts have been made reduce air resistance by streamlining hulls and superstructures, however; the
power benefits and fuel savings associated with constructing a streamlined ship tend to be overshadowed by construction cost
For Glorious, her design didn’t change between the Mediterranean and the Norwegian sea. As mentioned above the ship would have sat marginally higher in the water due to the water density and thus present a greater non-wetted area for air resistance.
Colder air is also denser and the air resistance would be greater in Norway and thus, the ship would be required to burn slightly more fuel.
Conversely, the greater humidity and warmer temperatures of the Mediterranean would affect aircraft operations as the decrease in density affects the performance of the aircraft. The denser air of Norway would actually benefit flight operations and create lift (if other variables were excluded).
Steering Resistance
Steering resistance is added resistance caused by the motion of the rudder. Every time the rudder is moved to change course, the movement of the rudder creates additional drag. Although steering resistance is generally a small component of total hull resistance in warships and merchant ships, unnecessary rudder movement can have a significant impact. Remember that resistance is directly related to the horsepower required to propel the ship. Additional horsepower is directly related to fuel consumed (more horsepower equals more fuel burned). A
warship traveling at 15 knots and attempting to maintain a point station in a formation may burn up to 10% more fuel per day than a ship traveling independently at 15 knots
We know that HMS Glorious adopted zig-zagging to protect against U-Boat attacks. This action will ultimately result in greater fuel consumption as the ship engages its rudder more than if it was steaming in a straight line. Additionally the ship needs to increase speed while zig-zagging to main a set speed of advance. For example Glorious routing home was set to be 16kts. However, Glorious was also zig-zagging to confuse u-boats (reported as Admiralty pattern no 10). This zig zag pattern results in 96% Distance Made Good due to the deviations from her course as a result of zig-zagging. So if Zig Zagging at 16kts, HMS Glorious would only achieve an advancement of 15.36NM. If they wanted to maintain an advancement of 16kts,Glorious would need to go around 16.5kts
Flight Operations
The status and frequency of aircraft operations is relatively unknown without the log books.
HMS Glorious was present off Norway to ferry the RAF Gladiators back to the UK and the aircraft onboard were primarily there for her defense and, to a lesser extent, offensive operations where circumstances permitted.
However, we should consider that for a period during each day the ships were engaged in aircraft launch & recovery operations. During this period the vessel would increase to a much higher speed to maximize air flow over the flight deck for flight operations.
Lets say that flight operations required 1hr a day and that during this period the ship speed increased to roughly 20kts or 11.75 tons/hour
Hull Resistance
Glorious arrived in Malta in January 1940 for docking and refit. By June she had been out of dry docking for approximately half a year, with 3-4 months spent in the Med.
During the Mediterranean period the ships hull would have attracted growth although the colder waters of Norway would have most likely killed some of this growth and the negative affect on ship performance would be reduced.
However, studies have shown warships losing power over several months after leaving dry dock as the hull accumulates growth and anti-fouling becomes less effective (rougher). It is probable that Glorious would also experience a reduction in performance as the year progressed. However, to what extent if open to debate
There are additional considerations that may increase Glorious‘ fuel consumption. During my research I put these questions to a number of museums that house historic vessels from this era aswell as people with experience or knowledge of the equipment.
Below are additional fuel considerations that were highlighted when operating in cold climates or within the Artic Circle.
1. At colder temperatures the fuel heaters would have to be energized to prevent waxing of the fuel and clogging of the fuel lines, filters, and pumps. This would cause an extra strain on the electric heaters which would cause the generators to burn more fuel.
While Norway was a lot colder than the Mediterranean , I am not entirely sure if the fuel heaters would be needed. During the Artic convoys at near freezing this would be the case but possibly not with ambient temperature of 6*c? However, some ships heat the fuel to move it around the vessel and this certainly would demand more energy if the ambient temperature was lower
2. When a vessel is operating in colder temperatures the anti-icing system would have to be energized to prevent ice build-up in the engine intakes. This requires a huge draw of bleed air from the online engines that causes them to burn a lot of fuel to continue operating.
Again, it was cold, but I’m not sure the use of an anti-icing system would need to be implemented (if one existed on Glorious). The temperature was cold but ice/snow is not common at this time of year
3. Colder temperature produce less hull growth and thus less resistance
Agreed, this would actually be one of the major benefits to cold water operations. However, the speed values from March are shortly after the vessel exited docking with minimal growth.
4. Steam heaters for combustion air would have to work harder to provide the preheat needed for efficient combustion
I need more information to identify if this would affect Glorious and the Yarrow boilers that were installed.
5. Water density would also be a factor. Just by looking at the plimsoll line on ships you can see how much lower or higher they would float in different ocean’s.
Already factored into the discussion. Glorious would sit higher in the Norwegian waters
6. Heating & Draining: The fuel delivered to the ship is stored in the bunker tank where it is heated by supplying steam to the coils installed in the bunker tanks. Heating is an essential process, which makes it an integral part of fuel oil treatment. The average temperature maintained for heavy fuel oil bunker tanks is around 40ºC. After transferring it to a settling tank, the fuel is further heated to ensure it is at an appropriate temperature to enter the separators. Once the fuel is transferred to the service tank from the separator, the oil temperature is >80ºC. The main intention is to ensure the smooth pumpability of the fuel oil at different processes and to separate the maximum quantity of water from fuel by draining the settling and service tanks and using purifiers.
I don’t know the tank insulation setup and proximity of fuel tanks to the hull on Glorious but it is highly probable, due to the ambient temperature, that heating the heavy fuel so that it was more viscous in colder conditions (6*c) consumed more energy than in the warmer tropics (25*c). The Illustrated London News cutaway from 1935 shows the fuel stored at and below the waterline on the Courageous class carriers in tanks adjacent to the hull. Depending on the degree of insulation there maybe some thermal transfer considerations between the oil tanks and seawater and vice versa.
So what does all this mean?
Simply put, the fuel consumption figures that were collected for Glorious the Mediterranean do not accurately reflect the environmental and operational characteristics that would have been encountered by the same ship in the Norwegian theatre.
It is highly probable that Glorious would experience increased fuel consumption when operating in colder climates
Calculation of fuel consumption is much more complicated than a ‘blanket’ speed calculation for the whole deployment period. Glorious operation included periods of steaming, including periods of zig-zagging and aircraft deployment and recovery speeds.
Below is a graph showing fuel consumption including an additional 5 & 10pc consumption rate due to accumulation of all the factors detailed above.
In reality and considering similar studies the weather alone could increase fuel consumption by 20-30%. However, 10% seems a fair starting point for this study.
So lets revisit the initial figures
In the data below, I have calculated HMS Glorious returning to the UK as part of the convoy she was meant to be part of including an additional 10% for all the factors mentioned above.
During the deployment period I have calculated HMS Glorious steaming to Narvik at 17kts (speed of advance) but with a vessel speed of 18kts to account for zig-zagging. I have included 1 hour a day of flight operations which, in my opinion, seems pretty low for a carrier operating in a war zone. During flight operations the ship would increase speed to 20kts. In reality I think the flight operations speed may be slightly higher and this is a conservative figure. For the high speed Hurricanes recovered by Glorious on the 8th and 9th, accounts show that Glorious was steaming at high speed, probably in the very high 20’s possibly hitting 30kts. This would consume significant quantities of fuel – possibly as much as 40 tons per hour (before weather factors). These values have not been included in these calculations.
In my calculations, aircraft operations from Glorious are kept up until the the 8th when the RAF aircraft are onboard and I calculated the remainder of the deployment and loitering without aircraft operations.
During the period of ‘fuel conservation’ I have Glorious steaming at 16kts zig-zagging, effectively 15kts speed of advance. I think any slower would make her vulnerable to U-boats and aircraft and this seems to be the lower speed used by Ark Royal in her log
During the transit back to the UK HMS Southampton recorded the speed of advance at 15kts. I have factored a hypothetical speed of 16kts to account for zig-zagging etc
Weather and all other resistance factors have been grouped together in a 10% increase in fuel.
Finally, the size of Glorious‘ fuel tanks is also open to question. The documentary indicates bunkers of 3500 while other documents show 3800 tons. I have shown the remaining reserves based on both of these values
Above is a calculation showing Glorious’ departing on the 8th June and arriving on the 10th as planned. As can be seen in this calculation, Glorious has used 80% or more (86%) of her fuel on arrival in Scapa. The previous data shows that if Glorious had stayed with the convoy she would have returned with approximately 10% of her fuel.
We all know someone who tells us that you should let your automobile fuel run low because you will be drawing the sediment at the bottom of the fuel tank into the engine. Similarly, on a ship, drinking the last few dregs of your bunkers may also present issues with sludge and/or other contaminants. Unlike today, the stringent requirements of fuel composition were not present during WWII and sludge was (and remains today) a real issue. Even in modern shipping all fuels will have some amount of water and sludge. One offset of this problem is that HMS Glorious may have undergone tank cleaning during her dry docking 6 month previous and removed any existing accumulations in the tanks. However, this does not account for contaminants that exist within the actual fuel.
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Other than issues with sludge, the low quantities of fuel may also present, to a lesser degree, issues with vessel stability. However, I believe the main consideration when running low will be ‘lack of redundancy’ if fuel tanks are damaged and/or destroyed/contaminated by enemy action e.g. torpedo, mine, air attack and the resultant ingress of saltwater. Having more fuel means that you can spread it out in multiple tanks and if one is damaged the fuel can be sourced from another tank. While small quantities could be placed in separate tanks, the issue of sludge becomes a bigger problem.
Above: Nice carbon emissions from Glorious! She wouldn’t be winning any environmental pirzes 
The data points to the possibility that if Glorious had returned later with the convoy her fuel reserves would probably be low and in some cases on the verge of depletion.
While this does not justify many aspects of HMS Glorious‘ lightly guarded return to the UK , lack of patrols and other points of concern, it does lend credence to a possible low fuel scenario as presented by the Navy.
Understandably, this calculation will upset many of those who view the low fuel scenario as a ‘cover story’ for a vindictive Captain rushing to attend a court martial and thus jeopardizing his ship and crew in the process.
However, both the low fuel scenario and the Captain’s desire to court martial one of his officers should not be addressed as ‘either/or’ scenarios. It is possible that the low fuel situation of Glorious benefited the Captain’s attempt to court martial one of his officers and gave him a supplementary reason to return to Scapa. Both scenarios can exist simultaneously and not in isolation.
But who’s “fault” is it if Glorious runs low on fuel? The Captain’s? Admiral Wells who must have been receiving information on Glorious fuel consumption? Was it a calculated gamble that didn’t pay off?
While I accept that Guy D’Oyly-Hughes was an extremely complex character, I often wonder if D’Oyly-Hughes “what took you so long” comment to Cross once all the Hurricanes had been successfully landed may have been out of concern for the ships fuel consumption during the operation. Landing the RAF Hurricanes required Glorious running up to maximum speed to enable the fast aircraft to land, multiple accounts state she was running at 30kts with “steam busting out of every rivet” . At this speed, Glorious would have consumed up to 50 tons an hour normally, but with the heavy swell and wind reported by the pilots this could be 55-60 tons/hour. If Glorious had fuel issues this would have exacerbated the situation, literally burning almost a ton a minute!