WesWorld

Quoted

Originally posted by HoOmAn
How were German engines impaired by the lack of specialist metals for exotic alloys?

I heard this played a role in the Jumo 222 desaster?

I heard it had a huge effect on the Germans capailities to use high tempreture resistant alloys which then resulted in less effective engines (power output, fuel consumption etc.)?

How did Germans engines with or without such alloys compare to foreign (especially French, British or American) ones?

If there was such lack and if it had negative effects - what was done to counter that?

Thanks.

This is a famous opener known as a Herald trap.

First set up a premis as a test.

Well let's see.........

The Jumo 222 problems were not so much exotic alloys as they were heat dumping, getting the valve bores and displacement right, stopping leaks, and the allied bombing interrupting the line of development. When Junkers engineers finally closed in on a production grade proof type. It was in the middle of a war, German jets were coming into their own, and the RLM had sunk a ton of money into the project for no apparent immediate result. Exotic alloys would have helped Junkers at that point, but weren't necessary-just another six months of B-17s kept off their necks and the production grade engine would have finally proofed. Like the DB 600 series you could design around rare metal shortages and Junkers did-just not in time.

How did it compare to Allied types?

The design concept of individual blocks in a radial layout was simply brilliant, the execution was like the American hypers-promising, frustratingly close, and ultimately killed at the balance sheet.

The design was expected to operate with 87 Octane fuels at less than 7/1 compression for example. Fuel injection tech was plainly superior. So the tech was first rate.

The early prototypes leaked lub oil excessively and had complex seals that repeatedly failed from heat bloom spots. That problem Junker engineers solved in a frustrating series of rebuilds, which didn't help the development cycle in the eyes of the RLM.

Thanks for reminding me about it, though.

H.

http://www.tighar.org/Projects/Histpres/…ort/bmw801.html

In my frank opinion, BMW could have taught Pratt and Whitney a lot.

Let me quote:

Quoted

THE BMW 801 RADIAL ENGINE


The BMW 801 twin row radial engine formed the basis of the Focke Wulf fw190 design. This engine has the reputation as being among the better engine designs of WW2 regardless of limitations in German supercharger technology which lead to some failings at high altitude. It also powered many other Luftwaffe aircraft, from the Arado Ar 232A to the Junkers Ju 390.

The Bayerische Motroen Werke (BMW) based in Munich, were manufacturing Pratt and Whitney radials under license in the 1930’s and used this experience to develop its own twin row engine. Despite this, it can be considered an original design incorporating fuel injection and other German features.

A remarkably compact installation, adequate cylinder cooling was obtained using pressure baffling augmented by a magnesium alloy fan geared to turn at 1.72 times engine RPM (3 times propeller speed). An oil tank and cooler are positioned in the nose bowl and are armour plated. The engine mount ring is a sealed unit of square cross-section and also acts as a hydraulic fluid reservoir. Additional streamlining was achieved by the introduction of drag-inducing cowl flaps.

The BMW 801D-2 (fig.6.) was fed by methanol-water injection. Most revolutionary however, was the Kommandogerat. This hydraulicelectric “brain” unit was operated by a single control which was the pilot's throttle lever. It automatically adjusted fuel flow, mixture strength, propeller pitch setting and ignition timing. It also cut in a second stage of the supercharger at the correct altitude. The pilot could, if required, manually set the propeller pitch without altering any of the other settings.

The BMW 801 made the Gnome Rhone 14 look primitive.

What I want to emphasize is the systems approach that BMW and FW both took to make this engine work. The BMW motor designers paid close attention to Kurt Tank, and his design team, as he tried to design a cooling shroud and insisted on fan assisted cooling of the oil reservoir at the head of the engine, as well as designing a heat radiator for that oil reservoir.

The shell that went around the engine was so important to overcome the normal drag that large cross-section induced, that it gets well deserved famous mention..

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Data from Quest for Performance, Jane’s Fighting Aircraft of World War II, and Standard Aircraft Characteristics

General characteristics

* Crew: 1
* Length: 33 ft 7 in (10.24 m)
* Wingspan: 42 ft 10 in (13.06 m)
* Height: 13 ft 1 in (3.99 m)
* Wing area: 334 ft² (31 m²)
* Airfoil: NACA 23015.6 mod root; NACA 23009 tip
* Empty weight: 9,238 lb (4,190 kg)
* Loaded weight: 12,598 lb (5,714 kg)
* Max takeoff weight: 15,415 lb (6,990 kg)
* Powerplant: 1× Pratt & Whitney R-2800-10W "Double Wasp" two-row radial engine with a two-speed two-stage supercharger, 2,000 hp (1,491 kW [29])
* Propellers: 3-blade Hamilton Standard
o Propeller diameter: 13 ft 1 in (4.0 m)
* * Fuel capacity: 250 U.S. gal (946 L) internal; up to 3x 150 U.S. gal (568 L) external drop tanks
* Zero-lift drag coefficient: 0.0211
* Drag area: 7.05 ft² (0.65 m²)
* Aspect ratio: 5.5

Performance

* Maximum speed: 330 knots (380 mph, 610 km/h)
* Stall speed: 73 knots (84 mph, 135 km/h)
* Combat radius: 820 nm (945 mi, 1,520 km)
* Ferry range: 1,330 nm (1,530 mi, 2,460 km)
* Service ceiling 37,300 ft (11,370 m)
* Rate of climb: 3,500 ft/min (17.8 m/s)
* Wing loading: 37.7 lb/ft² (184 kg/m²)
* Power/mass: 0.16 hp/lb (260 W/kg)
* Time-to-altitude: 7.7 min to 20,000 ft (6,100 m)
* Lift-to-drag ratio: 12.2
* Takeoff roll: 799 ft (244 m)

Armament

* Guns:
o either 6× 0.50 in (12.7 mm) M2 Browning machine guns, with 400 rounds/gun, (All F6F-3, and most F6F-5)
o or 2× 20 mm cannon, with 225 rounds/gun
o and 4× 0.50 in (12.7 mm) Browning machine guns with 400 rounds/gun (F6F-5N only)
* Rockets:
o 6 × 5 in (127 mm) HVARs or
o 2 × 11¾ in (298 mm) Tiny Tim unguided rockets
* Bombs: up to 4,000 lb (1,800 kg) full load, including:
o Bombs or TorpedoesFuselage mounted on centreline rack)
+ 1 × 2,000 lb (910 kg) bomb or
+ 1 × Mk.13-3 torpedo;
o Underwing bombs: (F6F-5 had two additional weapons racks either side of fuselage on wing centre-section)
+ 1 × 1,000 lb (450 kg) or
+ 2 × 250 lb (110 kg)
+ 6 × 100 lb (45 kg)

Quoted

Specifications (Fw 190 A-

Data from Fw 190 A8

General characteristics

* Crew: One
* Length: 9.00 m (29 ft 0 in)
* Wingspan: 10.51 m (34 ft 5 in)
* Height: 3.95 m (12 ft 12 in)
* Wing area: 18,30 m² (196.99 ft²)
* Empty weight: 3,200 kg (7,060 lb)
* Loaded weight: 4,417 kg (9,735 lb)
* Max takeoff weight: 4,900 kg (10,800 lb)
* Powerplant: 1× BMW 801 D-2 radial engine, 1,272 kW (1,730 hp); 1,471 kW (2,000 hp) with boost

Performance

* Maximum speed: 656 km/h at 4,800 m, 685 km/h with boost (383 mph at 19,420 ft (5,920 m), 408 mph (657 km/h) with boost)
* Range: 800 km (500 miles)
* Service ceiling 11,410 m (37,430 ft)
* Rate of climb: 13 m/s (2560 feet/min)
* Wing loading: 241 kg/m² (49.4 lb/ft²)
* Power/mass: 0.29 - 0.33 kW/kg (0.18 - 0.21 hp/lb)

Armament

* 2× 13 mm MG 131 machine guns with 475 rounds/gun
* 4× 20 mm MG 151/20 E cannons with 250 rounds/gun in the wing root and 140 rounds/gun outboard.

Specifications (Fw 190 D-9)

General characteristics

* Crew: 1
* Length: 10.20 m (33 ft 5 1/2 in)
* Wingspan: 10.50 m (34 ft 5 in)
* Height: 3.35 m (11 ft 0 in)
* Wing area: 18.30 m² (196.99 ft²)
* Empty weight: 3,490 kg (7,694 lb)
* Loaded weight: 4,350 kg (9,590 lb)
* Max takeoff weight: 4,840 kg (10,670 lb)
* Powerplant: 1× Junkers Jumo 213 A-1 12-cylinder inverted-Vee piston engine, 1,287 kW, 1,544 kW with boost (1,750 PS / 2,100 PS)

Performance

* Maximum speed: 685 km/h at 6,600 m, 710 km/h at 11,300 m (426 mph at 21,655 ft / 440 mph at 37,000 ft (11,000 m))
* Range: 835 km (519 mi)
* Service ceiling 12,000 m (39,370 ft)
* Rate of climb: 17 m/s (3,300 feet/min)
* Wing loading: 238 kg/m² (48.7 lb/ft²)
* Power/mass: 0.30 - 0.35 kW/kg (0.18 - 0.21 hp/lb)

Armament

* 2× 13 mm MG 131 machine guns
* 2× 20 mm MG 151 cannons
* 1× 500 kg (1,102 lb) SC 500 bomb (optional)

http://www.wwiiaircraftperformance.org/fw190/ptr-1107.pdf

Why this detail? The Germans knew they had trouble with superchargers and fuels [RA mentioned this]. They especially, Kurt Tank, designed around it. The magnesium fan was one case where he had to use a scarce metal to overcome a performance limitation he faced. Magnesium takes casting and milling very well, far better than aluminum-so for a fan it makes a lot of sense.

Where the Americans went for brute power in their R-2800 to overcome drag, Tank was subtle. He tried to reduce frontal area and design a cleaner plane around that BMW801. The BMW motor engineers were forced to conform to his demands. They did a remarkable job of producing a lightweight competitive radial. It shows 0.16 hp/lb. for the Hellcat, as opposed to 0.21 hp/lb. for the FW-190.

It is a remarkable study in how to build around limitations. If the German engineers had solved the supercharger problem?

Quoted

I always got the feeling those German engines were 200 to 300 hp behind foreign engines and the Germans somehow had to compensate lost years of technical developments after the Great War. The only exception seems to have been diesel engines - both naval and aviation, right?

The technical experts who wrote the technology limitations into the Versailles Treaty were not fools. They hurt the German technology tree badly enough that it delayed the Germans' basic research by at least a decade in engines, metallurgy, though significantly not electronics.

That delay the Germans made up during the Great Depression [Slump] rapidly, but I get the feeling, they were always just a half cycle behind in the established technology trees. When you get to the new trees, like rocketry and jets, they easily kept pace or forged rapidly ahead. It also depended where they put their money.

Aircraft diesels was one place where the Versailles powers didn't care.

H

Quoted

Originally posted by HoOmAn
So German engine and aircraft engineers worked closely together? Does this happen with other engines too (i.e. DB6xx series)?

It wasn't as extreme then [total systems engineering approach] where all design factors including pilot workload burden was factored into the total aircraft as it is today. Kurt Tank really drove the FW 190 design choices such as the integrated fuel throttle propeller pitch controls for the power-plant. He simplified flight controls by using electric motors and magnets to operate all movable plane surfaces including the cowl flaps on the engine nacelles [primitive FADEC and fly by wire]. To an extent that not even Kelly Johnson achieved, he thought of the plane as a total unit with the Human being as part of it. If you could fly a glider or even walk and chew gum at the same time you could fly a Butcher Bird. You had to be an athlete with perfect hand/eye co-ordination to fly a P-38.

Other Kurt Tank projects followed this approach. Hugo Junkers followed a similar line with the Ju-88 series [same engines so he really didn't have much choice, the 801s had that primitive FADEC setup built in at the factory, so the engine flight controls had to be similar].

I don't think Messerschmidt or Claude Domier had a clue. With the DB 6XX engines, they just built an airframe and shoved the engine into it. Later Heinkel and Arado designs followed the Tank model. Most of the German jet projects-even Messerschmidt's followed the Tank HFE model.

With jets you didn't get a choice, you had to design a combined throttle control, and simplify the flight controls [hydraulics-the electric motors the Germans had weren't strong enough to move control surfaces under the new work loads , light enough, and used too much copper, to go into their jet aircraft] or the bizarre forest of toggle and slide switches you see in a 1950s multi-engine jet aircraft would be far worse for the pilot to memorize .

Quoted

Having engineers of both the airframe and the engine company work together doesn´t seem to be something special first place. I would have expected it from the British or Americans too for example (RR Griffon into new Spitfire version?). Probably just because it is quite common today....?!

Not as extreme as Kurt Tank drove it then. The British and the Americans were stuck back in the 1930s. NACA had some ideas about pilot workload burden and Ed Heinenman played with the concept of Human factors engineering, but until Tank came along, nobody really thought about the pilot as part of the engineering package in an aircraft. Strange that is. Orville and Wilbur between crashes talked about that all the time, as their second biggest problem in manned heavier than air flight control. The Human being, they concluded, is a lousy way to design a flight control input device.

R. J. Mitchell built the Spitfiire around the Merlin to be sure, but he didn't build it like a modern airplane. He didn't take the four influences, drag, lift, available thrust, and gravity, look at the powerplants he had [Jumo 139 first and 810 later for Tank, then] and try to build to his load limits off mathematics. He just craft designed as small as he could and as clean as he could within British tech [like an automobile of the era] to go as fast as he could off of his seaplane racers. He had a fairly good idea that it would fly well from his extensive Schneider Trophy experiences. This is not how Kurt Tank designed the FW-190. Tank started cold and modeled, bench tested flight-controls, and wind-tunneled thew aero-shell until he had a flying prototype aero-shell. BMW did the same with the engines. Tank was in the 1950s. Everyone else? Back in the days of Orville and Wilbur and not understanding Orville and Wilbur at all.

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Why haven´t others worked on airborne diesels? For example I seem to remember several Martin flying boats exploded in mid-air because of fuel leaks. That couldn´t have happened with diesels - or at least I can´t remember to have ever read about a BV138 exploding because of a fuel leak.

1. Diesel engines because of the greater working pressures either have to be;
a. heavier kW/kg [thicker cylinder walls, heavier blocks]
b. built out of light, strong, heat CE tolerant metal alloys.
c. built by people who know exactly what they are doing.

[C.] is very important. Gasoline engines have sloppier work load tolerances across the range of burden [spark plugs] so they are easy to build. Diesels? Carburetion or fuel injection for the aerosol mix has to be exactly right at the working atmospheres or no self-ignition at pressure.

It took the Americans twenty years to get decent working diesel locomotive engines. They packed those into their submarines. Good engines, except for the HORS. You have to know what you are doing

Junkers not only built a decent 2 stroke Diesel opposed piston engine in the Jumo, 205 but actually made it work at varying altitudes by the same kind of clever valve and 11 degree offset timing arrangement you find in the US Fairbanks Morse diesels. I suspect that the US company simply stole that idea from Junkers.

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I mention flying boats here as this type of aircraft seems best suited for diesels back then - no high speed but range needed, fires less likely and you can share fuel with your navy friends now and then... Well, at least if you´re German. The Allies used patrol for their PT boats after all.

The Dornier Do-26 flying boats for example?

H

Quoted

Originally posted by Red Admiral
Systems engineering and whole other branches didn't really exist at that point. It was pretty much a case of we've got these engines available and so we'll build an aeroplane around them. It wasn't really until the late 50s until the weapon concept arrived with the interaction between all the pieces being studied to arrive at the best result. This was brought about mainly through the much greater speeds available and the need to intercept nuclear-armed bombers. The complexity of aircraft massively increased as well. Back in the 30s it was possible for a single person to design an entire aircraft, backed up with some people to do detail work. Now you'd have someone working on optimising every single piece.

Engines of the day were fairly complicated with different levels of boost from the supercharger needed depending on throttle, speed and altitude. With the RR engines you had automatic boost control with the option to set manually if needed (to get very economical cruising). You've also got variable area flaps on the radiators depending on the throttle setting. Most were fairly simple two or three position that you opened or closed depending on engine temperature. There were lots of simple little things that could have been automatically to reduce pilot workload considerably.

That is more or less why I put Kurt Tank into his own special class as an aviation engineer. He tended to think in terms of the systems approach-even if it didn't exist yet and nobody else did.

H.