Siemens-Schuckert D.IV

[Slater]

From a Wiki article on this aircraft:

Although the short landing gear and limited prop clearance led to tricky landing, the plane was otherwise easy to fly. It had a very short take-off run, and at heights above 4,000 m (13,100 ft) was faster and more manoeuvrable than the Fokker D.VII. Its most notable feature was its phenomenal rate of climb and extremely high service ceiling—it could reach 6,000 m (19,700 ft) in less than 14½ minutes. In 36 minutes it could reach 8,100 m (26,600 ft), about 1,200 m (3,900 ft) higher than the Fokker's maximum altitude

For such an apparently superior machine, one hears remarkably little about it. Was it just because of the relatively small numbers to enter service?

[Darby]

I can't answer your question but it's a lovely looking aircraft.

[sinnerboy]

ditto Darby....pugnacious little brute!

[Slater]

From a related article:

"The engine was unique among rotaries in that the crankshaft revolved in one direction and the cylinders and crankcase revolved in the opposite direction, thus giving an equivalent engine speed of 1,800 rpm with a propeller speed of 900 rpm, a direct 2-I reduction. This feature allowed the use of a huge four-bladed propeller that was streamlined with a spun aluminum spinner."

[KRK4m]

The complete fuselage of SSW D.IV - although modified by Albatros after the Great War for high-altitude flight experiments (hence called H.1 for Hoehenversuchsflugzeug) - is exhibited within the Polish Aviation Museum in Krakow. Contrary to popular belief the huge prop is two- (not four-) bladed.

http://s579.photobucket.com/user/tomeyk/media/Muzeum%20Lotnictwa/IMGP1301.jpg.html

The 11-cylinder Siemens-Halske Sh III engine is in situ. BTW the bi-rotary Siemens engine has been patented in 1907 by Polish engineer Henry Brzeski, living a century ago also in Krakow

Edited April 13, 2016 by KRK4m

[GrzeM]

I think the Siemens-Halske engine was not fully developed and difficult to maintain so pilots and mechanics preferred more reliable units - like in the Whirlwind-Peregrine case.

BTW, the link to the photo in previous (KRK4m) post doesn't open - one has to remove space in the end of it to see the photo.

[KRK4m]

BTW, the link to the photo in previous (KRK4m) post doesn't open - one has to remove space in the end of it to see the photo.

Replaced with another one that opens easily Thanks for your observation

[Jure Miljevic]

D.VII had thick airfoil wing which allowed for all internal bracing wires. Fokker borrowed that from Junkers monoplane from 1915, I think. Nevertheless, quite a courageous decision for a time, when thin airfoils were considered to be state of the art. Side effect of such a profile was a large front radius which allowed for higher critical angels of attack and plenty of warning before stall occurred. Hence the comment D.VII made good pilots out of mediocre material. Siemens-Schuckert D.II, D.III and D.IV all had thin airfoils and snapped into a spin rather quickly. That did not bother veteran pilots too much, but surely prevented less experienced to fly their mounts to the full. On a plus side its double-rotary (WWI term, today it is called contra-rotary) engine, essentially a geared one which cut propeller revolutions in half, allowed for coarser pitch propeller, which in turn was far more effective and more suitable for climbing than fine pitched prop on D.VII. Also, thanks to counter rotation gyroscopic effect was cut down to acceptable level.

Various sources give various climbing times for SSW D.III and D.IV but on general they are on pair with D.VII. I suspect SSW had no trouble to beat D.VII in that aspect if both started from the ground with their engines off and not previously warmed up. With liquid cooled engine Fokker had to wait for a couple of minutes for cooling water to reach working temperature, while SSW could take-off seconds after starting an engine. Apart from being contra-rotating Siemens-Halske Sh.IIIa was also over-compressed with one source stating its compression ratio was as high as 6:1. Over-compressing an engine was one of the shortcuts to retain power at higher altitude in absence of workable compressors. Unfortunately D.III with high-compressed (but not over-compressed) Sh.III engine first appeared on the front in time when it transpired that newly introduced castor oil substitute Volt-Öl is unsuitable and IdFlieg restricted Sh.III engines to 900 rpm in level flight. D.IV with SSW IIIa, which appeared in the summer 1918 was much better and apparently troubles with lubricant had been sorted out by then as Sh.IIIa could for a short time run at 1000 rpm at sea level, delivering 240 hp and could still manage its nominal power of 160 hp at 3700 meters. Some prominent German pilots (Rudolf Berthold among them IIRC) stated it was the best German fighter that reached the front. Regards

Jure

[GrzeM]

Very interesting, Jure!!!