Why is it upside down???

[bf109 Emil]

fuel injection allowde this, where as the carbs on a merlin resulted in a few flying characteristics as a pilot would roll and then dive to allow fuel to be pushed into the carb, where as a straight dive would have thrown the fuel up, causing the Merlin to sputter. Because of the weak wing roots, a cannon firing down the ceter, or crank hub was prefered to wing mounted cannons, and the drag from the bulge required to mount cannon shells (drum) hampered performance.

the biggest hinderance in performance was Germany's lack of a very high octane fuel.
"A breakthrough in gasoline production occurred in the United States in 1935 when it became technically possible to produce isooctane with a reading of 100 in large quantities. By 1939, both the American and English air forces had begun to use the improved gasoline, and their planes could then be equipped with correspondingly stronger engines. In Germany, also, a method had been discovered to manufacture such a high-test gasoline, but the process was much more complex, cumbersome, and expensive than the American method, which used different primary materials. Due to these difficulties in production, the Luftwaffe until the end of 1938 neglected to insist on the production of high-octane fuel. For this reason until 1945 the German Air Force had no fuel equal to that available in the English-speaking countries.19

How important the new aviation fuel was is demonstrated by the improved performance it made possible: 15 percent higher speed, a 1500-mile longer range for bombers, and an increased altitude of 10,000 feet. Göring attempted to make amends for the past neglect at the end of 1938 when he demanded that the 19 million barrels of aviation fuel included in the Revised Economic Production Plan be manufactured as high-test gasoline equivalent to the quality of isooctane.2"

bf109 Emil

 

[Fokker D21]

bf109 Emil, I don't think you are right. Read the following article:

Gasoline - Wikipedia, the free encyclopedia

During World War II, Germany received much of its oil from Romania. From 2.8 million barrels (450,000 m³) in 1938, Romania's exports to Germany increased to 13 million barrels (2,100,000 m³) by 1941, a level that was essentially maintained through 1942 and 1943, before dropping by half, due to Allied bombing and mining of the Danube. Although these exports were almost half of Romania's total production, they were considerably less than what the Germans expected. Even with the addition of the Romanian deliveries, overland oil imports after 1939 could not make up for the loss of overseas shipments. In order to become less dependent on outside sources, the Germans undertook a sizable expansion program of their own meager domestic oil pumping. After 1938, the Austrian oil fields were made available, and the expansion of Nazi crude oil output was chiefly concentrated there. Primarily as a result of this expansion, the Reich's domestic output of crude oil increased from approximately 3.8 million barrels (600,000 m³) in 1938 to almost 12 million barrels (1,900,000 m³) in 1944. Even this was not enough.

Instead, Germany had developed a synthetic fuel capacity that was intended to replace imported or captured oil. Fuels were generated from coal, using either the Bergius process or the Fischer-Tropsch process. Between 1938 and 1943, synthetic fuel output underwent a respectable growth from 10 million barrels (1,600,000 m³) to 36 million. The percentage of synthetic fuels compared with the yield from all sources grew from 22 percent to more than 50 percent by 1943. The total oil supplies available from all sources for the same period rose from 45 million barrels (7,200,000 m³) in 1938 to 71 million barrels (11,300,000 m³) in 1943.

By the early 1930s, automobile gasoline had an octane reading of 40 and aviation gasoline of 75-80. Aviation gasoline with such high octane numbers could only be refined through a process of distillation of high-grade petroleum. Germany's domestic oil was not of this quality. Only the additive tetra-ethyl lead could raise the octane to a maximum of 87. The license for the production of this additive was acquired in 1935 from the American holder of the patents, but without high-grade Romanian oil even this additive was not very effective.

In the US the oil was not "as good," and the oil industry had to invest heavily in various expensive boosting systems. This turned out to have benefits: the US industry started delivering fuels of increasing octane ratings by adding more of the boosting agents, and the infrastructure was in place for a post-war octane-agents additive industry. Good crude oil was no longer a factor during wartime, and by war's end, American aviation fuel was commonly 130 to 150 octane. This high octane could easily be used in existing engines to deliver much more power by increasing the pressure delivered by the superchargers. The Germans, relying entirely on "good" gasoline, had no such industry, and instead had to rely on ever-larger engines to deliver more power.

However, German aviation engines were of the direct-fuel-injection type, and could use methanol-water injection and nitrous oxide injection, which gave 50% more engine power for five minutes of dogfight. This could be done only five times or after 40 hours run-time, and then the engine would have to be rebuilt. Most German aero engines used 87 octane fuel (called B4), while some high-powered engines used 100 octane (C2/C3) fuel.

This historical "issue" is based on a very common misapprehension about wartime fuel octane numbers. There are two octane numbers for each fuel, one for lean mix and one for rich mix, rich being always greater. So, for example, a common British aviation fuel of the later part of the war was 100/125. The misunderstanding that German fuels have a lower octane number (and thus a poorer quality) arises because the Germans quoted the lean mix octane number for their fuels while the Allies quoted the rich mix number for their fuels. Standard German high-grade aviation fuel used in the later part of the war (given the designation C3) had lean/rich octane numbers of 100/130. The Germans would list this as a 100 octane fuel while the Allies would list it as 130 octane.

After the war the US Navy sent a Technical Mission to Germany to interview German petrochemists and examine German fuel quality. Their report entitled "Technical Report 145-45 Manufacture of Aviation Gasoline in Germany" chemically analyzed the different fuels, and concluded that "Toward the end of the war the quality of fuel being used by the German fighter planes was quite similar to that being used by the Allies."

 

[Kurfürst]

In the US the oil was not "as good," and the oil industry had to invest heavily in various expensive boosting systems. This turned out to have benefits: the US industry started delivering fuels of increasing octane ratings by adding more of the boosting agents, and the infrastructure was in place for a post-war octane-agents additive industry. Good crude oil was no longer a factor during wartime, and by war's end, American aviation fuel was commonly 130 to 150 octane. This high octane could easily be used in existing engines to deliver much more power by increasing the pressure delivered by the superchargers. The Germans, relying entirely on "good" gasoline, had no such industry, and instead had to rely on ever-larger engines to deliver more power.

An old myth that dies very hard - the German C-3 grade`s additives were changed in late 1942, making it equivalent to the 150 grade fuel the Allies begun to use in quantity in mid-1944.

However, German aviation engines were of the direct-fuel-injection type, and could use methanol-water injection and nitrous oxide injection, which gave 50% more engine power for five minutes of dogfight. This could be done only five times or after 40 hours run-time, and then the engine would have to be rebuilt.

The bold part is totally baseless...

Most German aero engines used 87 octane fuel (called B4), while some high-powered engines used 100 octane (C2/C3) fuel.

In fact a lot used C-3... DB 601N, the BMW 801D series, all DB 605s with methanol in early/mid 1944 etc. Fischer Tropsch estimates C-3 being a major volume of synt. avgas production, up to 2/3s...

The part on different avgas ratings is very true, though!

 

[Fokker D21]

Also read this:

The C-3 grade corresponded roughly to the U. S. grade 130 gasoline, although the octane number of C-3 was specified to be only 95 and its lean mixture performance was somewhat poorer. (see: Technical Report 145-45 - The Manufacture of Aviation Gasoline in Germany

Most Bf 109 ran on B4 fuel, except the later 109E and early F with DB 601N and some K4 with DB605D engines (not all DB605D's). B4 fuel was more or less equel to early British fuel. Two third of all German aviation gas produced was C3 fuel. US 150 grade fuel was intoduced late in the war.


I couldn't agree more with you, Kurfürst.

 

[Beto Aero]

One further reason: the gyroscope effect. Remember that most of the a/c with propellers uses this advantage in maneuver. The increased weight of rotational parts, in the attempt to obtain bigger engines, read more HP, deemed designers to put the crank as close as possible to longitudinal center line, in the attempt to reduce negative gyroscope effects, and increase maneuvering capability.
Of course, if the engine is too big, the heads would be in front of pilot's sight. In order to maintain pilots view, and the body as narrow as possible, the germans decided to invert the engine and put the pilot behind it. The americans invested on new wing's profile to reduce drag. Check out how much higher is the P-51 fuselage compared to the ME 109.
The problem with the 109's landing gear wasn't the hight: it was just too narrow. Germans made this way because the wings spar were too light, and would not hold the landing loads. Further more, the hydraulics were simple too.
Best Regads
Beto Aero

 

[vanir]

The Inverted V-engine, gives the airframe a larger angle to the usually low mounted wing. This reduced interferense drag and this was also the reason why the pilot head space was rather small. Nevertheless it was one reason why the 109 had a surpisingly high diving speed, what saved also their lives quite often.

This takes honours. Even the German aces have said this. There exists an argument it is a retospective benefit rather than design goals. But the original design was the BF-108 with an inverted V-8. I'd say definitely the design goals of that layout then was pilot view and low CG (as a civilian sports and military liason type), and probably ease of maintenance under field conditions.

So it is fairly likely I think this reasoning carried over into the BF-109 and its inverted V-12 engines, but with the added benefit of improved streamlining over the only serious competitor in its class, the British Merlin (AFAIK the Hispano-Suiza was a more rudimentary copy of the original Curtiss D-12 like the Kestrel). This thinking apparently affected the entire German aero engine industry, whilst radials were disliked due to frontal mass.

 

[jerryw]

There is a detailed coverage of the German inverted aero-engines on P 33 of the Aircraft Engine Historical Soc., journal, "Torque Meter" Vol 2, No.2 2003.
In summary: 1/ the reason of the inverted layout was due to direct instruction from the German Air Ministry, not from choice by the manufacturers.
2/ the biggest problem with the inverted installation was the excessive accumulation of oil thrown off the crankshaft in the left hand cylinder bank. This caused detonation in those cylinders as the oil passed by the rings and into the combustion chambers. This is why the compression ratios in the DB601 engines were different for each bank.(7.3 vs 7.5)

 

[KevinB]

My best guess is this created an engine with a lower center of gravity, putting most of the weight at the "bottom" of the engine instead of the top. It also made servicing the engine somewhat easier, as most of the "complicated" stuff (fuel lines, spark plugs, ignition wires, valve covers, etc.) was at the bottom of the engine, not the top, where it would be easier to get to.

The bad news is this required a "dry sump" lubricatiing system, which is more complicated than a "wet sump" lubricating system.

This is consistant with what I learned. The CG closer to the roll axis is a plus. The dry sump was a design improvement that improves BHP/ efficiency in cruise and better cooling, lubrication during manuvering.

all the best,

KB

 

[KevinB]

One further reason: the gyroscope effect. Remember that most of the a/c with propellers uses this advantage in maneuver. The increased weight of rotational parts, in the attempt to obtain bigger engines, read more HP, deemed designers to put the crank as close as possible to longitudinal center line, in the attempt to reduce negative gyroscope effects, and increase maneuvering capability.
Of course, if the engine is too big, the heads would be in front of pilot's sight. In order to maintain pilots view, and the body as narrow as possible, the germans decided to invert the engine and put the pilot behind it. The americans invested on new wing's profile to reduce drag. Check out how much higher is the P-51 fuselage compared to the ME 109.
The problem with the 109's landing gear wasn't the hight: it was just too narrow. Germans made this way because the wings spar were too light, and would not hold the landing loads. Further more, the hydraulics were simple too.
Best Regads
Beto Aero

on the landing gear:

Way too narrow. I was made to understand that the aircraft could be shipped in a smaller space due to the this feature. Even though the pilots didnt like it becuase torque on take off was a problem. Props-to-go and a heavy hand on the throttle with high pressure could be a poblem.

KB

 

[PWR4360-59B]

Maybe they liked hydraulic locking problems. I aways heard it was for pilot sight and keeping the prop up off the ground. Does't a gear box do the same?
The merlins and allisons worked just fine. So I don't get it. Lots on engineering things are not always based on logic but, on what the big wig in the company wants.

 

[KevinB]

I didn't mention earlier. I've been told the inverted V gives better visibility over the nose from the pilots perspective.

I know some of the late Spanish built 109's had merlins in them. Was the Merlin converted to run in an upside-down configuration in this setup? anyone with Pics or knowledge of how this was accomplished?

KB

 

[Denniss]

I didn't mention earlier. I've been told the inverted V gives better visibility over the nose from the pilots perspective.

I know some of the late Spanish built 109's had merlins in them. Was the Merlin converted to run in an upside-down configuration in this setup? anyone with Pics or knowledge of how this was accomplished?

KB

Bf 109 with RR Merlin does not look very decent:
Buchon 109 on Flickr - Photo Sharing!
Hispano Aviación HA-1112 - Wikipedia, the free encyclopedia

 

[GADGET]

The Hispano Aviación Buchones has a regular Merlin engine with no special conversions on them. Those Merlins also had propellers that turned in anticlockwise direction, the opposite the airplane was designed for, so making those Messer very tricky to fly and specially during take-off.

Armament of the Buchones has to be placed on the wings as there was no provision on their Merlin engines for a centershot cannon. I have been told by pilots who flew them that gunnery was on the trcky side due to assymetrical vibration and ammo stoppage of a single cannon made hitting a target impossible due to the induced yaw of the other cannon.

 

[The Basket]

Didn't the prototype 109 fly with a RR Kestrel which must have been fitted uninverted. So the engineers would have had to redesign the engine installation for the RR 109s and the DB 109s. No easy fit.

I have read nothing saying the original 109 was ever intended for night fighters so not sure about the exhaust configuration.

 

[antoni]

Didn't the prototype 109 fly with a RR Kestrel which must have been fitted uninverted. So the engineers would have had to redesign the engine installation for the RR 109s and the DB 109s. No easy fit.

I have read nothing saying the original 109 was ever intended for night fighters so not sure about the exhaust configuration.

The first intened engine, BMW 116 was rejected but its replacement, Jumo 210, was not yet available. With the help of Ernst Heinkel several RR Kestrel IIS engines were obtained.

RR had originally proposed, with the agreement of the Air Ministry, that the new engine that would later be known as the Merlin, have an inverted installation in order to provide improved visibility to pilots plus other sound technical reasons. In general, the airframe manufacturers at the time were totally opposed when a mockup was revealed to them at the end of 1932. An inverted installation invoved too many akward design problems. The new engine was revised for upright installation.

 

[gjs238]

FWIW, there were many inverted engines, some are listed here:
Category:Inverted aircraft piston engines - Wikipedia, the free encyclopedia

 

[VALENGO]

Sorry, gentlemen, but i´m afraid that this topic was treated in another post:
http://www.ww2aircraft.net/forum/engines/why-inverted-v12-26229.html

 

[vanir]

But rather than necrothread two on the same subject I'll post in this one, given it was revived. I read about some RLM requirements, Price listed some during his research. Keep in mind several individual figures were ad libbing fighter requirements in the thirties since OKdL/RLM were still formative in structure. There were many firebrands, there were many conservatives and there was interservice rivalry for strategic materials and subsidy (especially with kriegsmarine).

Now firstly, important to note that both DB and Jumo independently proposed inverted vees as second generation aero inlines, whilst Hispano and RR went traditionally. Their listed reasoning (noted by IG Farben in some wartime documents), was aerodynamic streamlining of the aircraft. Specifically the widest area of the engine was to be located on the plane of the wing roots, the cockpit and rear fuselage was to be narrow and this would reduce overall frontal mass.
The reason this was so important to them, important enough to invert their forthcoming inline prototypes, was because of where inlines and radials were wrt to each other coming into the thirties. Using the Curtiss D motor and Wright engines as a loose measure (this was before the close fitted cowl was invented, radials only had an oil shroud) you lose 150hp in a radial to wind drag. On average the radial produces around 150hp more than an inline. So the strategy was: reduce the drag of the inline even more, it is faster than a radial or an inline.

It was a way to make a faster plane, but the trade off is the narrow cockpit and need for light equipment, ie. fuselage mounted gear, burying everything along the centreline and keeping the low frontal mass, lightly constructed wings, etc.

Focke Wulf went the other road. Streamline the radial and you still get more bulk in the airframe than compared to a fast inline, plus far better load bearing.

Anyway around 34 (FW wasn't proposed 'til 38 I think), RLM specified for inverted inlines but the fact was those were going to be available engines anyway. Radials are oily and higher maintenance, streamlined fighter airframes for them didn't really exist and they weren't really preferred, despite being the more powerful engine on average.

It was another factor, which Dr Messer says was by design, that forward/down view in the 109 is excellent. The side mounted blower and inverted engine allowed the cockpit and wing placement such that the pilot could see over the leading edge and the cowling was slim, so there was good view. In a Spit the wings are in the way and so is the motor, there is no forward/down view from any angle, you have to bank. Spitfires are always banking, ever noticed that? Messers are always diving. Not just the carb thing, this seems to be the character between them right to the end of the war.

 

[Shortround6]

The "short" cowling AKA Townend Ring did a lot more than control oil leakage. While not as good as the longer NACA cowling it was a major step forward.

It may be Wiki; but it gives an idea. Townend ring - Wikipedia, the free encyclopedia

According to some studies the Townend Ring also improved cooling which allowed either more power to be used while climbing or a high throttle setting could be used for a longer period of time before overheating the engine.

A Townend Ring was good for 2-6mph even on a 1930 90-110hp 2 seat cabin monoplane.

 

[vanir]

I read a period description in a Jackson book that the claims were a little excited and they were fitted because radials were putting oil all over the windshield normally, which isn't good. Some manufacturers chose not to fit them because they thought it would cause overheating or reduce cooling, but they did find in service the opposite happened, it actually improved cooling and solved the oil issue.

The NACA shroud though, the speed increase was wind tunnel tested, it was a clear and noticeable aerodynamic benefit (although overheating scare was brought up again, not everyone used them at first). When FW proposed its close-fitted new cowl in 38 the main concern was overheating, but I guess that old Townend idea had led the design team in the direction that it could be solved, which they eventually did by putting space behind the engine for a negative pressure I guess and use shutters for airflow, they got it okay eventually (but in the FW got the most benefit when they moved the engine forward from the A-5 onwards which also helped a vibration problem they had).