Albatros fuel feeding and inverted flying ?
Hello,
the Oeffag Albatros planes were indeed more sturdy, and i still wonder why this change in the lower wing (2nd spar) along with other, if minor, improvements by the Oeffag did not make it into the "normal" series.
Certainly aviation was in its beginning, and even constructors and engineers themselves did not really know what happened during flight. They measured the weight a wing would carry under static conditions, placing sand bags on it until it broke off - however dynamic energies influencing the wing and fuselage were almost unknown.
There was e.g. a pilot (forgot the name) who said his Alb DIII lower wing leading edge suddenly moved during a glide, but downward (!), and then began to "wobble". He survived and crash-landed his plane with the upper wing alone, and told what he had seen prior to the lower wing breaking off, to the german "Idflieg" (monitoring organisation of plane quality, and improvements). But they would not believe him, and he himself then began to doubt what he saw - if it cannot happen, i must be wrong ...
He was certainly right, at a certain speed the lower wing wobbled, he just did not understand why the front wing edge moved downward if the plane was supposed to "swim" on the air - there only could be pressure from underneath ? Today we assume that it was the beginning of a harnonic vibration, a self-enhancing movement, due to the speed of the air stream.
And additionally I think it is like nowadays, there are some management and politics idiots that either have no idea of about what they decide, or are just too ignorant, or arrogant. The people that have to live with the consequences of those management decisions are never heard.
Again a question, and it still is one - let me just say i am doing a kind of "brainstorming" here...
since i heard about this Alb flying - i will post anything if i find it again in the books, but they are numerous, and only partly deal with the Alb planes.
Inverted flying - should be no problem for a short time in a looping, where the g-force still holds the fuel at the bottom of the tank, and feeding system, ok.
Then the carburettors - there were already carburettors allowing inverted flying before the war (see Pégoud, the Etrich and Rumpler "Taube" planes etc.). Some of the german "Argus" carburettors designed for inverted flying could be fitted to other-than-Argus engines.
And the fuel feeding system: there were not even mechanically driven fuel pumps in the Albatros afaik, but the whole tank was set under pressure with a pressure pump. There were also hand pumps for initial pressure before the engine start, and emergency situations.
(This certainly does not apply for the second "free-fall" pressure-less emergency tank, that could be switched on in case of a pressure drop, or failure of the normal feeding system).
So regardless the position of the fuselage and engine, there would be enough pressure to feed the engine with fuel.
The swimmer in the tank was also designed in a way to pick up fuel at any position.
So why no inverted flying at least in some of the planes ?
Is there any list of planes, that were able to fly inverted, and why ?
Thanks and greetings,
Kai
. If you get it right spins on a sixpence or dime 
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