Regarding the streaking on the underprop vent.
1. there are many things that can cause oil streaking like that. It is not proof of a conventional oil cooler.
2. We have photos of planes with the exact same vent, in both size and shape, and photos of these aircraft with the engine cowling open. It is clear that at least these A-0 series did not have a conventional radiator.
3. Looking at the open cowl pics it is evident that there is very little space for much of anything.
4. Where is the exit for this oil cooler?
From these points I think one can ask the following questions;
If the A-0s that did not have an oil cooler had this vent, then what purpose did it serve?
And if it did do something, as it must have, then wouldn't cramming a conventional oil cooler in there impair the original function of the vent?
And why wouldn't this vent be redesigned if it was having an oil cooler added? This same vent went through multiple revisions on the prototypes, so why not change it now?
And just how did they fit this in?
I think that on the whole, the most sensible estimation is the one that is most obvious: it is oil that could have been forced out of dozens of parts.
Until concrete evidence is shown, photo of the cooler installed on the plane, drawings of such an installation or documents from heinkel describing this. For now I view it as a lot of speculation over what amounts to very tepid evidence in a best case scenario.
All very true. I'm going to try to contact the author to see if any built He 100's had a full combat dress as I cannot find anywhere that any of them did nor did not.
In He-100 Record Breaker?
There are photos of He-100s with streaking under the gun ports. There is a photo of a he-100 sitting in a hangar with the tripod mounted head armor visible.
There are also heinkel documents mentioning armament on test flights.
Yes, V4 (WkNmr 1903) D-IRCN, had a retractable radiator, but it was smaller and still relied on the evaporative system. This airframe was the first to be test-fit for armament and was also one of the early series airframes that had the problematic under-carriage and small horizontal stabilizer.
It was one of the He100s sold to the Soviet Union, too.
The V-4 was actually meant to be the pattern aircraft of sorts for the production series.
It possessed the following improvements;
Lighter stronger fuselage
New landing gear with the interchangable struts.
Wing condensers refined
Steam pipes in wings improved
Many minor modifications to the aircraft and assembly method
Retractable auxiliary radiator (meant for takeoff, taxi, climb and slow speed flight)
(4 gun wing development stopped with this machine)
There is one known potential photo of the V-4, which looks very much like an A-0(or D series if you will)
The Soviets purchased six He-100s - v1,v2, v4,v5,v6,v7
Those last three are the first A-0 block of production, which was upgraded mostly to block II standards by the time they were sent to the Soviets. A-0 block II being what you call the D-1 series.
This is known by Heikel records confirming delivery.
Of the D series, the three D-0 pre-production airframes were sold to Japan, the 12 production series, the D-1 were fully combat ready and were retained by Heinkel as "point protection" by being stationed at Heinkel's airfield at Rostock-Marienehe.
These 12 were also used extensively as propaganda and featured in various propaganda photos and "news" reports and either referred to as the He112U or the He113.
There were 19-20 A-0 series machines making a total of 24-25.
Six went to the USSR as described above, and three went to Japan.
The Japanese received at least one block II series, which is known because of Japanese documents showing tests of a He-100 with the block II style tail.