Version originale :The Daimler-Benz DB 605 List of content.
2)A short note on the basic technical aspects of the DB 605
-basic lay-out and performance
-the supercharging system.
3)Focusing on the single-engine applications of this engine, performance charts and commenta-ries on the following sub-types are presented:
-DB 605A-1, AM, AS, ASM, ASB, ASC, D, D-2, DB and DC.
4)Comparison with the two-stage Merlin engines - the direct rival of the DB 605. 5)Appraisal of a partnership: the DB 605 powered Me 109G and K.Introduction.
The Daimler-Benz DB 605 engine was an up-bore faster running development of the famed DB 601 and served the same main aircraft types as its predecessor: the Messerschmitt bf 109 and bf 110. Introduced in 1942 it presented the fighters with more basic power, better altitude performance - and higher weight. As the Me 109 remained a mainstay throughout the war - so did the DB 605. It was progressively developed to stay competitive, and luckily for the Luftwaffe it had good develop-ment potential, although reliability suffered somewhat. The war demanded ever more power and - in the west - still better altitude performance, and that challenge was met by the DB 605 through the use of higher grade fuel, higher compression ratios, higher boost pressures, better supercharging, and injection of anti-detonant water-methanol and oxygen carrier nitrous-oxide. As it turned out, the final demise of the Luftwaffe fighter force in 1944 can hardly be blamed on this the primary fighter engine of the Luftwaffe. Sadly from a Luftwaffe point of view, when the fine high-power, high-altitude versions came into service during 1944 they were put to use in an overstretched airframe piloted by inexperienced rookies, who starved of fuel were completely overwhelmed by superior allied forces. Basic technical aspects of the DB 605.
(This description and the following performance tables will be using metric measurements.) - 60 degrees inverted V-12, pressure-cooled - bore: 154 mm, stroke: 160 mm, total volume: 35,7 litres - compression ratio: 7.5/7.3 (87 octane), 8.5/8.3 (96 octane) - length: 2303 mm, height: 1050 mm, width: 762-845 mm - dry weight: 730 - 745 kg, built-in weight: 764 - 815 kg - 4 valves per cylinder, 1 overhung camshaft - direct fuel injection - single-stage variable speed mechanical compressor driven via a barometricly controlled hydraulic clutch (the DB 605L had a two-stage compressor) - rpm: max. 2800, climb: 2600, max. cruise: 2300 - performance: 1435 - 2000 hp at sea level - rated altitude in climbing condition: 5.8 - 8 km (again excluding DB 605L) . - several versions ecquipped to utilise MW-50 or GM-1 A note on the supercharging system.
Compared to the two-stage two-speed and turbo-charged engines of the western powers it is im-pressive what Daimler-Benz could achieve with the single-stage DB 605. By comparison the two-stage Merlin engines had a rated altitude ranging from approx. 5.8 km to 7.9 km. At the combat al-titudes of 1944 the performance of the DB 605 rivalled that of the high altitude Merlins 60 and 70 series of the Spitfire and the Mustang. While the conventionel mechanical superchargers consisted of one or two compressors driven via a two-speed gear, Daimler-Benz utilised an ingenious barometricly controlled hydraulic clutch which adjusted the compressor speed and thus the charging of the engine according to the needs at a given altitude. The conventional method results in a relative loss in efficiency below rated altitude, because the compressor uses energy to produce surplus charging. A graphic presentation of engine output relative to altitude would show a "saw-touth" line: the output in low gear rising with altitude until reaching the rated altitude, then output falls until the high gear kicks in, when the output again rises the rated altitude is reached. In comparison the Daimler-Benz system is more flexible. A graphic presentation would show a smooth shallow curve. A source of efficiency loss with this system being progressive heating of the oil as pressure in the clutch builds with altitude. Performance charts with comments
Source: Mercedes-Benz AG, Archives, Stuttgart, Germany. * = The DB 605D didn't enter service until spring of 1944 with the advent of the Me 109G-10. Comments.
The Me 109 sub-types were delivered with the following power trains:
Me 109G-1 through G-4: DB 605A-1
Me 109G-5/G-6: DB 605A-1, AM, AS, ASM, (ASB, ASC ?)
Me 109G-8: DB 605A-1, AM, (others ?)
Me 109G-14: DB 605A-1, AM, AS, ASM, (ASB, ASC ?)
Me 109G-10: DB 605D, (D-2 ?), DB, DC
Me 109K-4: DB 605DC, ASC (others ?).
As the table shows, the different sub-types gave very different performances, thus the performance of the Me 109G-6 varied a lot as this model was powered by a whole range of engines depending on availoability. The DB 605A-1 was still installed to the very end of the war.
A note on MW-50.
MW-50 (water-methanol 50/50) was injected into the air-intake and served as an anti-detonant allowing higher boost to be used below normal rated altitude. The evaporating water also cooling the charge-air thus increasing the weight of the charge. Limited by the performance of the supercharger the MW-50 induced max. output began declining 1.5-2 km. below normal rated altitude until it became impotent at and above the normal rated altitude (compare for example DB 605A-1 and AM). Max. continous use: 5-10 minutes. Penalties: drasticly shortens flight endurance and spark-plug life, added weight of MW-50 tank and piping. Most Me 109 sub-types from 1944/45 were equiped to utilise MW-50.
A note on GM-1.
Another means of improving the performance was GM-1 (Göring Mischung 1). In short the system worked by injecting nitrous oxide into the supercharger above normal rated altitude of the engine. The nitrous oxide serving as an oxygen carrier to improve the output at high altitude (pure oxygen prooving too volatile). The effect was phenomenal, raising output 25-30 % instantly. GM-1 was used by dedicated high altitude formations from 1941 onwards. Excessive bulk and weight were major penalities though, and additional supercharging was generally seen to be more efficient.Comparison with two-stage Merlins.
I shall not present performance charts for the Merlin engines here, partly to limit the size of this page, and partly because I lack detailed data (my sources are: "Allied aircraft piston engines" by Graham White and "Jane's fighting aircraft of world war II").
Taking into account the age of the Merlin design and its relative small displacement this two-stage inter- and aftercooled engine was a superb maschine. In comparison with the german engines the Merlin was lighter due to the relative abundance of metals for making light alloys. When comparing outputs one should also bear in mind that the allies were well supplied with high grade fuels (100/130/150 octane). The germans had to make do with 87, 92 or 96 octane, the higher grade fuels being especially scarce. ADI was used by both sides in the later stges of the war.
The Merlin 60 series were put into service in the late summer of 1942, around the same time that the DB 605A-1 went into service. The high altitude performance the Merlin 60 series was superior to the DB 605A-1. This superiority lasted into 1944 when the new AS and D sub-types went into service. These late sub-types equalled or bested the high altitude performance of the Merlins (Rolls-Royce and Packard) perhaps with the exception of the Mark 70. When GM-1 was used the picture changed thoroughly in favour of the DB 605.
The DB 605 basicly gave good low altitude performance, especially at sea level (read the discussion of the supercharging systems). In this regard the DB 605A-1 was superior to the Mark 61, 63, 66 and 68 Merlins. The superiority of the late mark DB 605's at low and medium altitude was very pronounced when using MW-50 (AM, ASM), high octane and high boost (DB, ASB), high octane high boost and MW-50 (DC, ASC).Appraisal of a partnership: the DB 605 powered Me 109G and K.
The advent of the Me 109G coincided, roughly speaking, with the irreversible shift in the fortunes of war for the germans: the allied offensive in Africa and Stalingrad. The luftwaffe confronted a vast and increasing allied numerical superiority, enemy planes and pilots were of increasingly better quality, and soon came the Götterdämmerung in home defence of the Reich, which bleeded the Luftwaffe of men, material and fuel.
Whether there is any symbolism in that, I shall leave unspoken. But a lot has been written about how the Gustav was loathed - blisters everywere destroyed the aerodynamics and looks of the plane, it was heavy and unresponsive, a retrostep compared to the F sub-type. Still many of the greatest Experten tallied the majority of their kills in the Gustav.
The Me 109G was, as were the earlier models, a very capable interceptor in fighter vs. fighter combat. It was endowed with fine low-speed flight characteristics, a high ceiling, and it was lightly loaded thus ensuring a very good or even phenomenal climb, fast acceleration in level flight, and the ability to perform sustained maneouvering. The normal armament although relatively light was deadly accurate due to the central positioning of all guns. In short it was a classic dogfighter.
Weight escalated of course with the installment of stronger and heavier engines, which again necessitated structural strengthening, and the old ease of handling suffered to some degree.
Although keeping up with the new allied fighters in terms of speed, climb and ceiling, it was in the fighting of 1943-45 against the US day bombers and their escorts, that the shortcomings of the mid-30's vintage interceptor were to show themselves. Equipped as a bomber destroyer with two underwing 20 mm cannons the Gustav became very unwieldy. As a result of this and the fact that the high altitude performance was much better than that of the Fw 190, the Gustav primarily took on the american and british escort fighters. These air battles took place at high altitude and very high speed, and at these speeds the control forces of the Gustav grew very heavy, the responsiveness and effectiveness of the control surfaces became very poor as did directional stability. Maneouverability was lost and the Gustav became a poor gun platform. Being a light interceptor the Gustav could not compete in dives with the new american fighters.
These shortcomings should not be overstressed though. The real horror of the air battles over Germany was the downright impossible tactical situation, where the overstretched Luftwaffe had to face overwhelming numbers of well trained, well equipped and aggressive allied forces