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The Luftwaffe and drop fuel tanks 1939-40.

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The Luftwaffe and drop fuel tanks 1939-40.

Postby Francesco Baracca » 27 Jun 2010, 16:59





The subject of the Bf-109’s centerline rack is a confusing issue. Such racks would be fitted to sub-variants or modifications of the aircraft through the rest of its evolution, allowing the carriage of a 250 kilogram (550 pound) bomb, four 50 kilogram (110 pound) bombs, or a 300 liter (80 US gallon) drop tank. However, it is very unclear whether the same rack could be alternatively fitted with all three of these stores configurations, or whether different racks handled different subsets of them. As the issue is both insignificant and difficult to resolve, this document makes no judgment on it.

Despite the success of the Bf-109E in the French campaign, some worries cropped up. For one, the Bf-109’s range had proven inadequate. For another, the Bf-109E had come up against the British Supermarine Spitfire fighter while the Luftwaffe had ineffectually tried to stop the mass evacuation of Allied troops at Dunkirk, and the British fighter had proven a formidable opponent.

These worries would become critical as the Luftwaffe shifted its attention across the English Channel. At first, things went well for the Luftwaffe. After the beginning of the Battle of Britain on 13 August 1940, the Bf-109s were allowed to range freely and engage British fighters at will, using the fluid tactics devised by Moelders in Spain. The British were trained in traditional inflexible formation tactics that put them at a disadvantage, but the RAF quickly adopted the Luftwaffe’s tactics.

While the Bf-109s ranged freely, the job of protecting the bombers fell to the twin-engine Bf-110s. It didn’t work. The Bf-110s were slaughtered, and so by early September the Bf-109s were ordered to operate as bomber escorts. Forced into a defensive posture, the Bf-109 was at a disadvantage relative to Hurricanes and Spitfires.

The limited range of the Bf-109 was also proving a liability, as it could not stay over the battle area for long before having to return home. After the bombings campaign was switched from British airfields to British cities, the RAF began to gain the upper hand.

The last action of the Battle of Britain was on 31 October 1940. The British had lost 631 Hurricanes, 403 Spitfires, and 115 Blenheim fighters, for a total of 1,149. The Luftwaffe lost 610 Bf-109s, along with 235 Bf-110s and 937 bombers, for a total of 1,782. Worse, many of the British pilots who had to bail out returned to battle the next day. Luftwaffe pilots who bailed out went to prisoner of war camps.

From a tactical point of view, the battle was not all that lopsided and could be regarded as a stand-off. However, it was a moral victory for the British, who had been the first to stand up to Hitler and make him back off, and a moral defeat for the Luftwaffe, who had been used to victories.

Nonetheless, the Bf-109 was still a dangerous adversary, and its cannon armament was devastatingly effective against RAF fighters armed with rifle-caliber machine guns, another lesson the RAF would absorb. Werner Moelders was the first of Hitler’s Luftwaffe pilots to exceed 50 kills, with Adolf Galland close behind him.

An aeronautic drop tank is an expendable and often jettisonable external fuel tank carried by aircraft for long-range flights. It is designed to be discarded when empty or in the event of combat or emergency in order to reduce drag and weight.

The drop tank was first used during World War II (ca. 1942) to allow fighter aircraft to carry additional fuel for long-range escort flights without requiring a dramatically larger, heavier, less maneuverable fuselage. The German Luftwaffe began using external fuel tanks with the introduction of the ME-109 E7 and FW-190 A4 in mid-1942, after noting the disastrous range limitations of ME-109s in the Battle of Britain.

The first Luftwaffe aircraft to have drop tanks were, the Heinkel 51 and the Henschel 123. To increase the range the “manufacturers added drop tanks.” The He-51B structure was strengthened, including twin-wire bracing of the landing gear, and a provision for a 50-liter drop tank beneath the fuselage was added. The Henschel tanks had an igniter, which caused the tanks to explode after they had been dropped. Galland used them in close support in Spain and Poland. All the aircraft developed in the mid 1930’s had about the same range, which was considered adequate at the time: Hurricane, Spitfire, and Bf 109. The Bf-109 was being manufactured with no extra fuel line for a drop tank, let alone a rack to hold the tank.

The German Luftwaffe used them pre-war with some of their Heinkel He-51s. In these earlier aircraft that were already draggy to start off with… the addition of a drop tank probably was that much of a penalty. The Me-109s were designed as a clean fighter and so the drag penalty was much more serious. I’ve heard that the penalty imposed could be up to 50% of the fuel (for a badly designed tank) carried would be eaten up just in overcoming the drag. I think it was apparent with the Doras/early Emils that combat fuel range was an issue and thus it wasn’t until the later Emils came along that the extra plumbing and fittings were put in place to accept a drop tank. It does take time to modify aircraft and the production facilities to handle these new modifications and build the infrastructure to stock up on supplies. Aircraft such as the Spits and Hurricanes were also designed to accept ‘ferry’ tanks but when initially developed they were created with the ideal of extending ferrying range not combat range.

The Luftwaffe was more concerned with a “bomb” rack. The first racks were fitted to the Bf-109E by Er 210. The racks and release system were fitted by the unit, not the manufacturer.

Er 210 started fighter bomber raids on England on August 12, 1940. The unit flew converted Bf-109E’s and Bf-110’s, “as fighter-bombers.” The first factory fighter-bomber was the BF-109E-4/B This came with the ETC 250 rack for a bomb. It wasn’t until October of 1940, that the Bf-109E-7 came off the production lines, with the factory installed ETC 250 rack that was capable of interfacing with a fuel drop tank. The drop tank fuel line came up behind the right side of the pilot seat, and ran along the right side lower cockpit edge through the fire wall to the engine.

“In late August 1940, the Bf 109E-7 began to arrive at fighter units. This differed from the Bf-109E-4 by having the capability to carry a 66-Imp gal (300 Litre) jettisonable plywood fuel tank. The lack of range had been one of the main disadvantages of the Bf-109 during the French campaign, and would further embarrass the Jagdgruppen over England, limiting combat time to just a few minutes. In practice, the tank was prone to terrible leaks and suspected of a tendency to ignite. It was rarely used in action due to the suspicions of the pilots”

The Germans did develop a drop tank for the Bf 109 prior to the invasion of France. Unfortunately, the design was rather hasty and the tank (made of plywood) tended to come ‘unglued’ (great shades of Ta 154!) when in use. The design allowed for about 70 gallons of fuel to be carried. Because of the leakage problems and the potential that resulted in it being a fire hazard it went unused. The original intent was that the Bf 109E-7 could use this tank to extend its range for use in both the French campaign and later against Britain.

This is another case of a single German manufacturer building a defective product on the spur of the moment and when the product fails to meet service requirements there is no suitable alternative. By the time the problem(s) comes to the attention of higher levels of command and is dealt with the operational effects have already caused debilitating losses.

Look at the same problem with the Bf 110. The D model with the Dackelbauch tank suffered a number of losses from explosions occurring when the tank emptied and the remaining fuel - air mixture was exposed to a spark. If anything, the technical incompetence of the Luftwaffe’s technische Amt in providing suitable and adequate equipment and aircraft to that service was a disgrace. The Göring had the stupidity to place such non-technical officers such as Ernst Udet in command of this critical branch of the Luftwaffe only shows his own incompetence as a leader.

Many alternative histories suffer either from the author’s axe to grind, or simply an excess of determinism: X country lost due to lack of whatever. If they had “only” done something else, the outcome would certainly have been different.

Most descriptions of war-losing mistakes by the Luftwaffe revolve around two, maybe three precepts: no development to production of a four-engine strategic bomber; lack of long range drop tanks for the Bf-109 lost the Battle of Britain (and by extension the war due to two fronts), and Hitler missed a golden opportunity by not accelerating production of the Me-262. These ideas are based either on what is known in the intelligence community as “mirror-imaging”; the tendency to see yourself in the actions or intentions of the enemy, or else on one book. Lack of a strategic bomber must have doomed the Luftwaffe’s war effort as it could not strike at enemy war making because the Allies did so-and they won. Ergo, a strategic bomber was a must-even though strategic bombing did not do anywhere near the economic disruption claimed at the time, or postwar for that matter. Adolf Galland’s bio “The First and the Last” was enormously influential in many historians’ views of the Luftwaffe and its strategy. One of his claims was that if only his crew’s had drop tanks they could have stayed with the bombers for a tactically significant time and inflicted unacceptable losses on the RAF. The second was that Hitler’s bungling prevented the effective employment of the Me-262 which would otherwise have ended bombing raids over Germany. None of these theses take into account the old military adage that the enemy always has a vote, and the allies would have responded to each threat.

“Luftwaffe Victorious“ takes a less deterministic view based on research of the last 10 -15 years. In this story, nothing is truly decisive in and of itself. Four engine bombers are put in production, but due to actual economic conditions only a few hundred are constructed. They play key roles in the Battles of Britain and the Atlantic, plus the airwar in the East, but the Allies find countermeasures. Drop tanks are employed, but the actual problems with them, leakage and the tendency to hang instead of drop, are enough to keep single engined fighters from overcoming a flawed strategy. As far as the Me-262 is concerned it is immediately put into production, but is more effective as a low-level bomber over the invasion beaches than as a fighter. In essence, Hitler was actually correct! Such a revolutionary aircraft demanded changes to air combat tactics. Tactics take time to develop and teach, time the Germans just do not have due to overwhelming Allied numbers and increasing technological sophistication. The Allied response is to accelerate B-29 production and deploy their jet prototypes.
NEC JACTANTIA NEC METU ("zonder woorden, zonder vrees")

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