Spitfire question

Discussion in 'Aviation' started by Marshall_Stack, Oct 29, 2008.

  1. Marshall_Stack

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    Did the Spitfire employ self-sealing fuel tanks? I know that pilots were burned because of the fuel tank in front of them. If they were self-sealing, why did they still get burned?
     
  2. Airframes

    Airframes Benevolens Magister

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    Hi Marshall. As far as I know, self-sealing tanks were introduced on the Spitfire Mk1 at the time of the BoB, although they were often retrofitted. The reddish colourouring on the outer surface of the tank was the sealing compound. The tank immediately in front of the front bulkhead, as you say, often caused horrific burns when hit, and again, this was mainly due to non-self-sealing tanks being fitted. However, this also occured with sealed tanks, when hit by incendiary bullets or explosive cannon shells. The shell exploded inside the tank, causing a jet of flaming fuel to shoot rearwards. The tanks were later armoured.
    Sorry it's a bit of a simplified expalanation, but I don't have the required references to hand to give specifics, such as dates etc.
    Terry.
     
  3. pbfoot

    pbfoot Active Member

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    I think in a previous thread it was discussed and the upper tank was not self sealing but the lower was , to prevent burns there was a firewall between pilot and fuel tank.
     
  4. Marcel

    Marcel Well-Known Member

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    From the Spitfire MK.II manual:
     
  5. kool kitty89

    kool kitty89 Well-Known Member

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    And the Hurricane's nose tank (gravity fed reserve tank) wasn't initially fitted with self sealing material when the wing tanks were being so fitted. This area being thought to be realatively invulnerable, this proved wrong (particularly against bomber's defencive gunners, and high deflection shots from fighters in a dogfight) and self sealing material was added to the foreward tank as well. (this being later durring the BoB iirc)

    I think the Spitfire's upper tank did eventually get self-sealing as well, but not until much later. (Mk.V, maybe later?)
     
  6. claidemore

    claidemore Member

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    Mk IX Pilots notes mentions only the lower tank being self sealing.
     
  7. pbfoot

    pbfoot Active Member

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    IIRC the upper was never self sealing
     
  8. kool kitty89

    kool kitty89 Well-Known Member

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    OK, I couldn't remember how that other discussion ended. ;)

    Did the Spitfire have fewer problems with the upper tank that the Hurricane did with it's earlier non-sealing forward tank?
     
  9. slaterat

    slaterat Member

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    The Hurricane also had its glycol header tank directly in front of the fuel tank, while the Spitfire had its glycol tank behind the prop. The Merlin III used 100% glycol which is very flammable. The Hurricane MK I had a 4mm armour plate added in front of the glycol tank to protect it and the reserve fuel tank. The merlin XII and later marks all switched to 80/20 water glycol mix which was far safer. The Spit V also received a 4 mm plate in front of the upper fuel tank.

    The Spitfires fuel tank was separated from the pilot by a fire proof bulk head. Initially in the Hurricane the glycol header tank was in front of the bulkhead and the reserve fuel tank behind it. The fireproof bulkhead was subsequently modified to cover the reserve fuel tank.

    So initially the spitfire was better protected with a fireproof bulkhead completely separating the pilot from the fuel tank and the glycol header tank protected by the prop. However the top fuel tank never was made self sealing ,though it did get armour plate in the Mk V and later.

    The Hurricane on the other hand started life more vulnerable with an exposed glycol header tank and a fuel tank on the wrong side of the fireproof bulkhead. The pilot was also surrounded by a wooden "doghouse" Then the Hurricane gets progressively better with
    - 4mm armour in front of glycol tank (MK I)
    -fireproof bulkhead extended to enclose the fuel tank (Mk I)
    - a self sealing tank( late Mk I ?/ MkII)

    Slaterat
     
  10. slaterat

    slaterat Member

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    The steps taken by Hawker would seem to indicate that a problem was recognized and addressed. Although it must be said that many fighters carried far more fuel in front of the pilot than the hurricane did including but not limited to the Spitfire, Tempest and the Corsair.

    Slaterat
     
  11. kool kitty89

    kool kitty89 Well-Known Member

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    I've always read it was a 70/30 water/glycol mix. And a hit to the engine its self (piercing the cooling jacket) would also have lead to a fire while the water mix wouldn't.
    Note it wasn't just for safety, but the addition of water made the coolant much more efficient at cooling (water having a much higher heat capacity) while still retaining a much higher boiling point than plain water. (though the pressurized cooling system had a lot to do with this as well) Plus the diluted glycol would also have been cheaper.
     
  12. antoni

    antoni Banned

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    Difficulties with their evaporative cooled Goshawk led RR to experiment with a composite system using both a radiator and condensers. It was this combined cooling system that was initially used on the PV12, later to become the Merlin, The system proved troublesome and after a few hours flight time it was decided to use pure ethylene glycol as the coolant. Glycol was used by the American Army but it had to tendency to leak through gaskets and joints. RR had experimented with it in the Schneider Trophy S.5 but abandoned it because of the same leakage problems. On 27th November 1931 the Air Ministry authorised the investigation of glycol cooling. Before that the official policy was to concentrate on evaporative cooling. Just before the outbreak of WWII a pressurised cooling system was introduced to the Merlin. This used a 70% water 30% glycol mixture which had proved superior to 100% glycol at atmospheric pressure and was not so prone to leakage.

    The Air Misnistry issued instructions to "save at all costs" the glycol becuase it was very expensive.
     
  13. kool kitty89

    kool kitty89 Well-Known Member

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    That pretty much agrees with my knoledge on the subject. I believe all production models of the V-1710 used a 70/30 mix.

    Going back further, I think the Curtiss V-1570 initially used water cooling, but switched to glycol (Prestone) cooling later on (I think it was 100%), and problems with glycol leaks was one of the reasons the AAC decided to cancel further development. (the outstanding reason was a greatly increasing interest in radial engines) I don't think it ever used a pressurized cooling system though.

    And the earlier RR Kestrel had used a pressurized cooling system. (with water only though iirc)

    Apparently the Peregrine Mk.I used 70/30 water/glycol as well.
     
  14. antoni

    antoni Banned

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    Unpressurised Ethylene Glycol boils at about 130°C, unpressurised water at 100°C (at sea-level) so was a great advantage before pressurised cooling systems became common.

    Curtiss P-6 Hawk

    Quote:
    The P-6 Hawk series resulted from the installation of the new 600 hp Curtiss V-1570 Conqueror liquid-cooled engine in what were essentially P-1C airframes. The variant which is best remembered today is the P-6E, which IMHO was one of the best-looking biplane fighters ever manufactured.

    The Curtiss V-1570 Conqueror engine was a evolutionary descendent of the Curtiss D-12 which powered the P-1 Hawk. The direct ancestor of the Conqueror was the unsuccessful Curtiss V-1400 engine which powered the P-2.

    The first aircraft to carry the P-6 designation was the fourth P-2(Ser No 25-423), modified to race for the Army in the National Air Races of 1927. It was the first Hawk to be fitted with the new Curtiss V-1570 engine which later became known as Conqueror. Because of the use of the new Conqueror engine, the Army gave the airplane a new designation--XP-6. Stripped of military equipment, it placed second in the unlimited event of the 1927 National Air Races.

    For its principal entry in the 1927 National Air Races, the Army ordered that extensive modifications be made to a stock P-1A (Ser No 26-295). It was fitted with a V-1570-1 Conqueror engine and was equipped with a set of PW-8A-type un-tapered wings complete with the skin-mounted radiators. It bore the company designation of Model 34Q. The Army redesignated this aircraft XP-6A No 1 because of its use of the Conqueror engine. It took first place in the 1927 race at a speed of 201 mph. However, the XP-6A crashed during preparations for the 1928 National Air Races.

    The success of the Curtiss Conqueror engine in these two racing aircraft led to an Army contract for a service test quantity of 18 P- 6s placed on October 3, 1928. These aircraft were assigned the serial numbers 29-260/273 and 29-363/366. These aircraft were given the company designation Model 34P. The Y-for-service-test designation had just been adopted at this time, but it does not appear to have actually been applied to these planes, although they are sometimes recorded as YP-6s.

    One of the innovative features of the new Conqueror-powered P-6 was in its cooling system. The water coolant of the earlier P-1 series was to be replaced by Prestone, a trade name for an ethylene glycol (HOCH2CH2OH) mixture. Prestone was a product of the Union Carbide corporation, and had an advantage of having a very high boiling point and a very low freezing point. By using Prestone instead of water, Curtiss was able to reduce the surface area of its radiators by one third. In addition, since less coolant was needed, the use of Prestone rather than water resulted in the savings of about 50 pounds of weight.

    However, since the new Prestone-cooled Conqueror engines were not yet ready, aircraft 39-269/273 and 39-363/366 were delivered in October 1929 with water-cooled V-1570-17 engines as P-6s, so that they could be gotten into service as rapidly as possible. The rest of the aircraft in the order were completed later as P-6As once the Prestone-cooled V-1570-23 Conqueror engines were finally ready.


    http://www.sil.si.edu/smithsoniancontributions/AnnalsofFlight/text/SAOF-0007.txt

    pg 78:

    Quote:
    Finally, at the end of the decade, a belated attempt was undertaken to challenge the air-cooled engine's position by a new approach toward a still smaller frontal area, coupled to a much-reduced weight of both coolant and radiator by the introduction of high-temperature cooling.
    Research on this "hot" cooling can be traced back to McCook Field as early as 1923. The coolant adopted was ethylene-glycol, in America known under the trade name Prestone*. Several Curtiss D-12 and Conqueror engines were converted to Prestone cooling during 1928 and 1929 and submitted to extensive tests, both at the Wright Field laboratory and, later, in the air.

    One Curtiss P-1B Hawk was used with a radiator, the size of which had been reduced by 70 percent, and a P-1C Hawk was fitted with wing radiators. During the Cleveland aeronautical races of 1929, Lieutenant Doolittle put one of these fighters through its paces with an unforeseen result. The reduction in radiator size increased the diving speed to such an extent that the plane shed its wings when accelerating during an outside loop and Doolittle had to take to his parachute.

    The engineering division at McCook Field had specified a coolant temperature in the radiator of 300° F. As a consequence, the cylinder-head temperature of the D-12 rose from 378° to 508° F and that of the barrel from 187° to 209° F. The aluminum block-***-steel-barrel construction could not adapt to these temperature rises and the glycol began to seep into the crankcase at the lower joints between the barrel and the jacket.
    This difficulty and other troubles that developed were impossible to remedy on the existing design. The result was a difference in opinion between Curtiss and the Army's engineering division. The Curtiss engineers maintained that the tests showed clearly that the specification for 300° F was exaggerated, as the oil cooler was becoming bigger than the coolant radiator, which was true. To this, the engineering division retorted that the real trouble lay with the seven-year-old block design. This was true also, but the Army went further and expressed the conviction that all monoblock forms of construction were obsolete, and in this the Army would be proved wrong.


    * Shortly after Prestone was introduced as an automobile antifreeze a rust inhibitor and a leak sealer were added to its ethylene-glycol base. It then became entirely unsuitable for use in aircraft engine cooling systems because the added chemicals would form a jelly-like substance if the solution became too hot—that is, at temperatures above 250° F. Some D-12 engines were ruined when an overzealous supply officer replaced glycol with Prestone in an emergency.
    78


    FIGURE 41 .-Curtiss Chieftain, 600 hp, 1927. (Smithsonian photo A-4666.)
    Although the application of high-temperature cooling to the D-12 was not conclusive and did nothing to keep that engine in the forefront, the data gathered were to be of great consequence for the future of high-performance fighter engines. It was with glycol also that the term "liquid cooling" came into use; hitherto, all service engines had been cooled by plain water.
    The Army would remain adamant for several years in its attitude toward a 300° coolant temperature, though later experience and research would show that much better results could be achieved with the ultimately used temperatures of 250-265° F.
     
  15. slaterat

    slaterat Member

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    A mixture of 70/30 distilled water/glycol is correct.

    Slaterat
     
  16. kool kitty89

    kool kitty89 Well-Known Member

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    According to that article all the experiments with the "hot" cooling were done on the older D-12, not the V-1570. I wonder if a pressurized cooling system could have used a pressurized cooling system. (being otherwise a pretty modern design, cast block with 4 valves per cylinder, significantly larger in volume than the contemporary Kestrel or Jumo 210 -also unpressurized-)
     
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