Considering the Germans already had used jets, had axial flow turbines, afterburners, turbo props etc and were aware of centrifugal turbines I'm not sure it was the British jet technology itself they were worried the Germans would copy. Just fear that the Germans would know exactly at what stage of development the British were at.
The Germans already had spectacularly performing helicopters able to lift artillery and whole airframes. They were already being thrown into use, it wasn't hypothetical. They had already used helicopters for submarine spotting and dropping marker flares over the submarines.
They already used helicopters for picking up downed airmen, artillery spotting and other observation duties.

Very basically without going into all the points again, the helicopter could never had chamged the war, just the possible effects that it could have after the war, in terms of deployment and uses.

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There's some stunning Footage of a Fa-223 airlifting a whole fieseler storch off the ground here. Image and Film Galleries And the remains of a FW190 and a kübelwagon.
Apparently the FW remains were flown over 30kms to a parts recovery area.
Also some nice footage of a Fl 282 being assembled from storage on the back of a ship at sea: Image and Film Galleries and being tested by Allies after capture: Image and Film Galleries

An interesting alternative possibility is the US XF5U "flying pancake." The original Zimmerman prototype proved to be a good flying machine on very limited horsepower. The production model was expected to hit 500+ mph (probably a highly optimistic figure) but even if it only did a bit over 400 it would still have made a powerful alternative to helicopters. The aircraft could take off using a very short run of just tens of yards and land nearly vertically.
A variant for use as a small transport with landing gear suited to rough fields might have been a viable alternative to the helicopter. Certainly, the higher flight speed, ability to fly over a larger range of altitiudes, the probability that it could actually defend itself against an enemy aircraft, and its longer range all argue that it would have made a good helicopter replacement.

Vought V-173 / XF5U-1 Flying Flapjack Info

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Thanks Grommo I enjoyed lerning about this.

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If this kind of wing worked so well, why did the concept vanish with the cancellation of this project? I would have thought that the skies would be full of nothing else...

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Because the concept is limited to propeller driven aircraft. The props are an integral part of generating the necessary lift over the "wings" such as they are. The jet did away with the concept; although I also suspect that its limited development also simply relegated it history rather that wider acceptance.

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Yes T.A., the pancake was a spectacular design . Testing of concept models showed tail-sitting hovering modes but the full size craft did not seem to have sufficient rotor lifting power for hover.
Footage of it landing at what almost appears to be running pace, (I'm exaggerating slightly) shows it possible suitability for ship board use and landing on rough and remote tiny island airstrips.
Watching the doco "strange planes" seems to suggest that due the requirement for greater power to match other fighters speed, the drive-train complexity escalated and the weight penalty offset the performance gain.


The british alternative to island combat fighter support was the Saunders Roe jet seaplane where you could have jet speed and still land almost anywhere in the lee of an island.

The prototype test bed flew on just 160 hp and weighed about 2200 lbs loaded for a power to weight ratio of .082.

The intended production version had 3200 hp on 15,000 lbs load or a ratio of .213. That's alot better than many other fighter aircraft of the period had by quite a margin. But, since it never flew any real test flights we shall never know for sure.

Seaplanes, jet or prop, have some severe drawbacks. The biggest is the need for a planing hull and having the engines mounted such that they will not ingest water or spray. These problems along with the saltwater corrosion issue make them less than desirable in many applications.
The Zimmerman design built with a couple of turboprops of even greater power could even today provide a useful ground attack design. I would think that the aircraft itself could be made rather stealthy without undue difficulty and having the engines buried on the top of the "pancake" would make them less vulnerable to dust and fod ingestion while the exhaust in such a location would reduce the IR signature to ground fired missiles.

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i'm more interested in hovercraft development, both with submerged propellers and pure hovercrafts. would the germans having those have made sea lion feasible?

I suggest you check out wiki as an introduction to the history of the hovercraft's development. Hovercraft - Wikipedia, the free encyclopedia

Another one would be Hovercraft history.

The website MilParade.ru | #32 | Levkov*s Hovercraft has an article on Soviet research on the hovercraft's military applications. I concede that it was the Austrian Hungarian navy that first looked at some form of hovercraft in the pre-WWI era but they didn't continue it. The Soviets in the 1930s made an effort and did produce some craft. However with Germany rampaging across the countryside, the development was still born.
It's unlikely, though, for the Germans to have developed hovercraft for crossing the Channel to invade England. Even if German pilots did prove the existence of the ground cushion effect with the Dornier aircraft, as far as I have checked, the German research didn't dwell into hovercraft.
The modern-day British inventor recognized for the development of today's hovercraft is lucky that the Soviets had such a penchant for secrecy.