Focke Wulf light fighter

[z42]

Calum wrote this.
Would that be feasible/possible to scale down a Jumo 213J for the light fighter design's purposes?

From what I understand, Calum's point was that the 213J contained many for the time advanced features that you'd find to this day in a high performance piston engine. To quote the same post you quoted "water cooled exhaust valve guides, swirl throttle, crankshaft nose oil feel, oil centrifuge and so on.". So would it be possible to create a smaller engine with these same features, yes of course it would.

The problem is timing. The 213J was a late 1944(?) prototype. If you start a new engine from scratch, count say 5 years before you have something mature for service. If by some magic Germany is still undefeated in 1950, the new lightweight fighter with the smaller 213J inspired engine would be going up against what, F-86 and Mig-15? Good luck with that.

 

[Shortround6]

The problem is timing. The 213J was a late 1944(?) prototype. If you start a new engine from scratch, count say 5 years before you have something mature for service. If by some magic Germany is still undefeated in 1950, the new lightweight fighter with the smaller 213J inspired engine would be going up against what, F-86 and Mig-15? Good luck with that.

Sometimes if you scale, you can short cut the development time a bit. This worked with jet engines a bit but not as well as they thought.

However it sometimes trapped designers. What does not scale well (or didn't at the time, before computers) were vibration patterns. Sometimes things worked well and other times they were chasing harmonic vibrations out into 3rd, 4th, 5th orders. 1930s engine designers did not like to change cylinder dimensions unless they had to.
Car engines are different, they are much heavier and can damp the vibrations out that way and they rarely run at high power settings which lessens the strain and since vibration is linked to the rpm cruising speed it often a very different vibration pattern than high speed.
This goes the other way at times. I had a BMW R90/6 motorcycle. BMW twins were noted for having low vibration back in the 60s and 70s. Except..................the 900 cc size. It liked to vibrate at about 55-60mph (you could not use the mirrors) but at 65-70 it was very smooth. Cracked the rear frame at about 8000 miles behind the left rear shock. When I was calling the east coast disruptor the service manager started describing where the break was to me before I finished talking. Hey, just putting in larger pistons and using bigger bore cylinders should be no problem right?

 

[GrauGeist]

Wait...what happened to Callum??

 

[dedalos]

There s no need to scale down the jumo 213j. With an output of 2600 ps , installed in a ,D-9 airframe (4100 kgr weight) the result would be spectacular performance. The problem is that
a) they would use it on 5+ tones Ta152
b) jumo 213j was scheduled for production in September 1945...
Only jumo213EB was production ready. Not as spectacular as the j , but still of decent performance given the limitations German industry faced

 

[tomo pauk]

Wait...what happened to Callum??

There was a temperamental discussion here, that saw J.A.W. banned, and Calum leaving the forum.

 

[bf109xxl]

...

The problem is that
a) ...
b) ...

c) they have no working biological system for fast cloning of experienced pilots.

Seems that all the other problems are less important.

 

[spicmart]

There s no need to scale down the jumo 213j. With an output of 2600 ps , installed in a ,D-9 airframe (4100 kgr weight) the result would be spectacular performance. The problem is that
a) they would use it on 5+ tones Ta152
b) jumo 213j was scheduled for production in September 1945...
Only jumo213EB was production ready. Not as spectacular as the j , but still of decent performance given the limitations German industry faced

I meant the scaling down to be wrt creating a Focke Wulf light fighter with the best piston propulsion.

 

[dedalos]

There was a temperamental discussion here, that saw J.A.W. banned, and Calum leaving the forum.

O nooooooo!!!!! Massive irreplaceable loss!
His book is THE BIBLE of ww2 air combat technology....

 

[GrauGeist]

There was a temperamental discussion here, that saw J.A.W. banned, and Calum leaving the forum.

Sorry to see that Calum left - thanks for the info, Tomo.

 

[spicmart]

Okay, let's put the Fw 190 on a diet.
F-W says that the BMW 801 powerplant will be heavier by 456 kg than the DB 605A powerplant for their spin-off of the Fw 187. Divided by two, difference of 278 kg. The 801s on the Fw 187 weight breakdown notes that two 801s will weight 2108 kg, with trapped fuel an oil. Armor is noted as weighting just 39 kg for the twin 801 installation, ie. ~20 kg per engine, however on the Fw 190 one engine there was 78 kg or armor for the oil system. If the 187 was projected to have the same armor as the Fw 190, the weight difference would've been up by ~120 kg.
The weight breakdown for these projects also notes the lower weight needed for the wing and U/C for the DB version, FWIW.

Back to a single 801 vs. 605A.
278 + 58 (= 78-20) = 366 kg weight reduction. The 605 allows for the motor cannon, so the MK 108 is installed instead of the cowl MG 131s and outer MG 151s. Less weapon drag even than what the D-9 had. Main gain is reduction of weapon-related weight (guns + ammo + mounts etc), circa 300 200kg, at least going by this table. Or probably 250 150 kg in case the cowl guns are the MG 17s? Compared with Fw 190A-6, were down by some 600 500 kg of take off weight, clean, mostly thank to the engine change - not a minor save vs. a 4100 kg fighter.
Now undercarriage - our brave new fighter will not be lugging around heavy bombs, so introduce a lighter U/C, with smaller wheels and a bit shorter legs. Instead of 258 kg, we might probably go down to 200 kg? Yes, I'm shamelessly copying what the NAA did here.
A 15% weight reduction allows us to cut the wing area by 15%, while keeping the wing loading the same. I'd try to get rid off the central - ie. the thickest - wing section by some 12-13% worth of span. Wing assy of the 190A8 weighed 475 kg, so here we can also save another 50-60 kg, and some drag, too (wing-related-drag on the Fw 190D-9 was significant 37% total drag - a new spanking low-drag wing on the 190/152 line certainly had a place here).

We'd be getting the lower wing- and weapon-related drag even when compared with the 190D-9 here, and probably the lower cooling drag. Weight save will be amazing vs. Antons and Doras, and wing loading will not be worse. Mileage will be much better.

edit: haven't accounted for the MK 108 + it's ammo weight in the 1st go; still a 600 kg decrease vs. the 190A-6 with lighter wing accounted for

Hi Tomo,

I was going back to your 190 lite and went through it again.
When taking a wing of 17 sqm and an armament of 3 x MG 151/20 (with 200 rouns per gun) and using your methods presented I get to about 585 kg that can be cut which is close enough to 600 kg.
Later DB 605 models weigh 10 to 50 kg. Especially the two-stage versions were heavier.

About range. I guess the DB 605 is less thirsty than the BMW 801's? I could find only a figure which is practically the same..
An estimate of how good range of the fighter would be with/without wing tanks and how much weight accrues when taking the ones from the D-12/13 R5?

 

[tomo pauk]

Later DB 605 models weigh 10 to 50 kg. Especially the two-stage versions were heavier.

I'd wager that late 605s weighted a bit more
There was only one 2-stage version, the 605L. It probably saw no service, though.

About range. I guess the DB 605 is less thirsty than the BMW 801's? I could find only a figure which is practically the same..

Spec consumption of the BMW 801D went to 300 g/PSh in Notleistung at the 2nd rated altitude (2nd S/C gear), dropping to 200 at different cruise settings in 2nd gear; figures for the fully rated engine. 801C consumption figures were worse (lower CR main culprit?), up to 345 g/PSh on Notleistung at the 2nd rated altitude (and still at 2550 rpm), and 215 at most efficient cruise settings. Per hour, the 801C was supposed to use 610+- L/h in 2nd gear on Notleistung, and about 300 L/h in most efficient cruise
DB 601E went to 235 g/PSh on Notleistung (440 L/h at the rated altitude), down to 205 in best cruise setting (2000 rpm, 1 ata; 240 L/h).
605A was supposed to consume 480 L/H in Notleistung ( obviously, this assume the fully rated engine), 440 L/h at Kampfleistung (the best power what it was reliably able to make before October of 1942), and 255 at best cruise (2000 rpm, 1 ata).

Note that 801s will still be with the greater drag and weight, further reducing the mileage.

An estimate of how good range of the fighter would be with/without wing tanks and how much weight accrues when taking the ones from the D-12/13 R5?

Sorry, that is all for today from me

 

[spicmart]

I'd wager that late 605s weighted a bit more
There was only one 2-stage version, the 605L. It probably saw no service, though.



Spec consumption of the BMW 801D went to 300 g/PSh in Notleistung at the 2nd rated altitude (2nd S/C gear), dropping to 200 at different cruise settings in 2nd gear; figures for the fully rated engine. 801C consumption figures were worse (lower CR main culprit?), up to 345 g/PSh on Notleistung at the 2nd rated altitude (and still at 2550 rpm), and 215 at most efficient cruise settings. Per hour, the 801C was supposed to use 610+- L/h in 2nd gear on Notleistung, and about 300 L/h in most efficient cruise
DB 601E went to 235 g/PSh on Notleistung (440 L/h at the rated altitude), down to 205 in best cruise setting (2000 rpm, 1 ata; 240 L/h).
605A was supposed to consume 480 L/H in Notleistung ( obviously, this assume the fully rated engine), 440 L/h at Kampfleistung (the best power what it was reliably able to make before October of 1942), and 255 at best cruise (2000 rpm, 1 ata).

Note that 801s will still be with the greater drag and weight, further reducing the mileage.


Sorry, that is all for today from me

Thanks!
Then MW50 became mandatory and accounted for the weight growths of the engines.

Edit: The MW50 installation weighed 64 kg (got that from a Ta 152). The unprotected wing bag tanks weighed about a couple of kilos (?). Our fighter gains about 100 kg and surpasses 3600 kg, still a very light figure.
With greater performance comes greater weight.