Now, to lay a bit of ground work, here is what you need to know about the Albatros D.V and Albatros D.Va. The first orders for the Albatros D.V were placed in April, 1917. The aircraft began arriving at the front a month or two later. The first Albatros D.Va order was placed in August 1917, and, likewise, the first aircraft began arriving in late September or October.
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Based on production records, we know that the Albatros D.V had a 160PS Merceds D.III engine. The Albatros D.Va was among the first German scouts to use the 170PS Mercedes D.IIIa engine, the one the British rated 180hp, and which you can see listed for the Albatros D.Va in the store page.
Rise of Flight Albatros D.Va performance is based on a French test of a captured aircraft. Here is the original document:
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Here is my proof that the Rise of Flight Albatros D.Va is based on this data. First, a rate of climb comparison. The two aircraft are an exact match:
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Second, the RPM of the Rise of Flight Albatros D.Va at sea level is an exact match:
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What doesn't match is the airspeed above 2km. However, thanks to chill31's airspeed calculator, we can see that neoqb went with a theoretical projection of the airspeed because the French data fell too far below it. The theoretical projection is based on the aircraft's RPM, propeller pitch, and diameter. That may seem overly simple, but I think that after seeing the graph, you will agree that it was by a similar calculation that neoqb decided on an appropriate airspeed for the D.Va above 2km:
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Now, in addition to the fact that the French document called this aircraft a D.V and not a D.Va (and they knew the difference, see below), the engine serial number, 31102, identifies its order date as pre-Frebruary 1917. Here is Dave Watts, who is also 777's data source for the D.IIIau engine in our Halberstadt D.II:
S.N. 37000 - 45900 are documented Daimler motors. In addition, a few of these are rebuilds being accepted into Fokker built D.VII's, but no source as to where they came from, but logic says these are from rebuild factories. There is, mixed in with the other motors, serial numbers in the 27700 - 37000 range, of which the later ones could well be Mercedes rebuilds, but the early numbers are just so early, I doubt they are Mercedes D.III's motors, as I have documentation that goes back to Armee orders starting in February and March of 1917 for Mercedes D.III's and they are serial numbers 31300 - 31599. So the early numbered motors would be from 1916! Anyone know what type of motor these could be? I have about 100 motors in this range and they were mostly accepted in October, although a few were in the July - September period.
In other words, based on production records, it is a 160PS Mercedes D.III engine. What would the performance have been with the Mercedes D.IIIa engine? Fortunately, there is also a French document for the Albatros D.Va…
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Yup, and note - both of them had almost exact performance (different take off weight?).Viks' quote.
But such similarity is superficial if we plot airspeed and RPM:
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And notice that the French document distinguishes the engine with the remark "nouveau modele," i.e. new model, a remark that is absent from the D.V document.
Now, you ask "why did Gavagai post the airspeed of a D.Va that was slower than the D.V?" For two reasons:
(1) The engine RPMs for the D.Va at sea level were much higher.
(2) The aircraft reached its theoretical airspeed, which is actually a better result than the D.V.
The main difference between the two aircraft was the propeller. The D.V had a 1970mm prop pitch, and the D.Va had a 1795mm prop pitch. Not every prop was fitted for maximum airspeed, as the Germans were very concerned about scrambling their scouts to meet their enemies above (some aerodrome threads refer to this as "climb bias"). However, there were numerous different props fitted to the Albatros D.V(a) series, ranging from the very low 1795mm to 2050mm (or possibly more–one type of Albatros D.III prop had a 2200mm pitch). What is really at issue is how many RPMs the D.Va would have generated with a coarser prop.
For example, with a 2050mm prop, if the D.Va generated only 1520 RPM, the theoretical airspeed at sea level would be circa 186.9 km/h (~116mph): that airspeed should be familiar to many of you.
In summary, there is proof that our Albatros D.Va is actually an Albatros D.V with a 160PS Mercedes D.III engine. The engine serial number, the relatively low RPM (1500), and the production documentation adequately support that point. While I believe that my remarks about RPM with the 2050mm prop are probably right, I admit they are more speculative. I intend to post at a later date with more solid support for my projections, perhaps after consulting with some of our more knowledgable forum members.
So, that is my summary. I hope you enjoyed it. I really and truly hope this results in some changes for our dead-horse Albatros D.Va.