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You asked for proof: the Albatros D.Va


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#1 gavagai

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Posted 09 February 2013 - 02:16

The point of this post is to prove that something is wrong with the Albatros D.Va in Rise of Flight. I can prove that something is wrong because I can prove that the performance data it is based on belonged to an Albatros D.V, not a D.Va. Rise of Flight and 777 have a track record of making changes when there is proof of error. Examples include the Pfalz D.XII center of gravity, the Fokker D.VII's up-down aileron deflection, and the SE5a's over-rev in a dive.

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.

Attached File  Albs_Serials.jpg   111.4KB   2125 downloads

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:

Attached File  D5a_engine_31102.jpg   313.48KB   2125 downloads

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:

Attached File  graph Albatros D.V(a) climb.png   67.05KB   2125 downloads

Second, the RPM of the Rise of Flight Albatros D.Va at sea level is an exact match:

Attached File  maxrpm.png   529.84KB   2125 downloads

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:

Attached File  RoFDVa.png   40.57KB   2125 downloads

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…

Attached File  D5a_no5695-17.jpg   312.92KB   2125 downloads

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:

Attached File  D.Vrpmairspeed.png   36.89KB   2125 downloads

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.
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#2 Haggart85

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Posted 09 February 2013 - 02:31

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.

Quote edited to avoid cluttering the thread.

I really hope this is the nail in the coffin to fixing the Albatros D.Va. I would love to actually be better equipped to give Camels a run for their money other than having to catch them napping! :x :lol:


As usual though, my hat off to you. Thank you for all your work! :S!:
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#3 Browning

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Posted 09 February 2013 - 02:47

Let's see if I have this right….

The facts that I can see are:

ROF's data for the DVa closely matches a French document for the DV.
The DV tested by the French has an older, rebuilt motor that is likely not to the same specification as the DVa's motor.
Therefore, the DVa in ROF is based on faulty data.
This first conclusion looks solid to me.

A French document for the DVa shows a slower maximum airspeed.
The tested DVa has a less course propeller than the DV.

The naïve conclusion from that data would be that the DVa in ROF is too fast and a courser propeller should be simulated to slow down the DVa ingame.
The speculative conclusion gavagai draws from that is that with a courser propeller the DVa would be faster and therefore the DVa in ROF should be faster.

The bits missing so far as I can see are:
1) Some kind of evidence that with a courser propeller, the DVa would be faster than both the French test and ROF's DVa. Can be easily demonstrated mathematically? I'm sure it can, I just don't see that case made.
2) Some evidence that a courser propeller pitch better represents the DVa. In other words; why not have the DVa match the data in the French DVa test if that is the only test data we have for the DVa? Do we have production figures for the propellers or something similar that shows that the course propeller was not normal?

If it turns out that nothing can be proved about item '2)', then what should be done to the DVa's flight model aside from slowing it down? (Better climb rate? Do we know how much better and if so, how?).
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#4 gavagai

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Posted 09 February 2013 - 03:23

Yeah Browning, that D.Va in the French test had a pretty good rate of climb: 12.5 minutes to 3km, compared to 14.5 minutes for our Albatros. The fine pitch slows the aircraft down in level flight, but yields a faster climb.

The evidence about what was the typical prop pitch for the D.Va is spotty at best. I've been browsing different forums, and at least one propeller fanatic says the Albatros D.V(a) used propellers from 5 different manufacturers. :o

Like I said, I'm not prepared yet to make strong case that coarse props were more common, nor to say that I'm 100% certain of what the resulting airspeed should be if it did. That's a further point that I have to investigate further. Thanks for your understanding.
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#5 AndyJWest

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Posted 09 February 2013 - 03:32

The theoretical projection is based on the aircraft's RPM, propeller pitch, and diameter.

Ah yes - so this is what all the waffle in the other thread was about: riseofflight.com/Forum/viewtopic.php?f=351&t=35542

You cannot predict an aircraft's performance from RPM, propeller pitch, and diameter. This isn't a theory. It is a fact. Not that the 'theory' presented in that thread actually had a theoretical basis worth bothering with. It was based on a coincidence…

As for the rest, you may well be right. The FM may be less accurate than desired. As to what, if anything, the developers do about it, that is up to them - and I suspect you'd get further if you stuck to presenting facts…
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#6 Browning

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Posted 09 February 2013 - 04:15

You cannot predict an aircraft's performance from RPM, propeller pitch, and diameter.

Well, you can predict speed from RPM, propeller pitch, prop diameter and drag coefficient and we don't need to worry too much about drag coefficient as it isn't changing, it is the props that are changing.

It's a good thing we can predict speed from these factors, else the only way to find the right prop for a motor's most efficient RPM would be trial and error.
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#7 AndyJWest

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Posted 09 February 2013 - 04:25

Ah, yes, drag. Something that got ignored entirely in the other thread…

You are probably right - if you know the drag, as well as the rest, you can make a prediction. And then you run the test to see if your prediction is correct…
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#8 J5_Vorlander

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Posted 09 February 2013 - 04:30

Good luck Gav,
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#9 JoeCrow

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Posted 09 February 2013 - 07:53

Just one important point which shouldn't be overlooked regarding propellers:

A fine-pitch propeller is often used on short-runway airfields or where the surrounding topography requires a steep climb-away. Effectively, a fine-pitch propeller produces increased acceleration and climb-rate at the expense of top speed. A coarse-pitch propeller does the opposite and is more effective for achieving higher top speed and for cruising but only at the expense of acceleration and climb-rate.

In a combat situation you need to make your mind up about which is most important to you: acceleration and climb rate (favouring TnB) versus higher top speed and faster dive speed (favouring BnZ) and choose a propeller accordingly. It is not quite as simple as described because there are many other factors involved. The SE5a review was a very good example of this.

Cheers.
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#10 J2_Wallenberg

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Posted 09 February 2013 - 08:02

Do you think that maybe Vasek from AB1 can provide propeller data? I'm not sure if he has enough information on Central Powers airscrews, but who knows.
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#11 Feathered_IV

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Posted 09 February 2013 - 08:21

A well set out appeal. Fingers crossed that the correct refinements are made.
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#12 elephant

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Posted 09 February 2013 - 08:22

The same from me too…
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#13 hq_Jorri

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Posted 09 February 2013 - 08:59

This all goes above my head…I just hopes Petrovich will take another look at the Albies, wether this is right or not :) But I hope it is.
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#14 Mogster

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Posted 09 February 2013 - 11:36

It would at least be nice to know if he agrees or disagrees with some recent suggestions.
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#15 J.j.

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Posted 09 February 2013 - 11:56

It would at least be nice to know if he agrees or disagrees with some recent suggestions.

My bet is he must be quite busy polishing Roland and Halberstadt DII's FMs…
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#16 gavagai

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Posted 09 February 2013 - 12:43

Doing a little more digging, accoring to Bob Gardner (http://www.woodenpropeller.com" onclick="window.open(this.href);return false;">www.woodenpropeller.com), Axial props for the D.Va were the type 95 and type 87.
http://www.theaerodr...rew-photos.html" onclick="window.open(this.href);return false;">http://www.theaerodr...com/forum/aircr … hotos.html

Type 95 was used on the Albatros D.III and the D.Va:

8644 (serial number I think)
AXIAL
160PS
D278
ST220
TP 95

Type 87, I'm 99% confident, is the 2050mm pitch prop mentioned before.
http://www.theaerodr...42-prop-id.html" onclick="window.open(this.href);return false;">http://www.theaerodr...com/forum/repli … op-id.html
http://www.theaerodr...-prop-size.html" onclick="window.open(this.href);return false;">http://www.theaerodr...com/forum/aircr … -size.html

So far, it sounds like much of the production records for WW1 German props are lost forever. :(
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#17 SYN_DerHesse70

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Posted 09 February 2013 - 15:11

Where can i sign the petition? ;)
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#18 redcoat22

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Posted 09 February 2013 - 17:06

Where can i sign the petition? ;)

All you have to do is Paypal them 3k to fund the time

Edit: would it make sense ( assuming this is all true) to convert our current Alb D Va into a straight V and create a new Va? Re: Brit Noop 17. Then it could be funded!
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#19 JG1_Lee_J10

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Posted 09 February 2013 - 20:46

A reasonable case for a flight review. Fix the D.Va with an easy path to a D.V.

Here's another idea for money making aircraft mods: Propellers! Provide propeller mods for each type. Offer a fine pitch to enhance climb and a course pitch for higher top speed. Then you choose to optimize for climb rate or top speed depending on your mission. There is some historical precedent for this. Late in the war, the Dr.I's gave up any pretense of speed and were fitted with climb optimized propellers.
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#20 gavagai

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Posted 09 February 2013 - 21:16

Yes, I think it would be reasonable to tweak our D.Va to match the D.Va test data with the 1795mm pitch prop @1555rpm, and then for Petrovich to make an experiment with alternative propellers. In particular, I hope that he would try out the 2050mm pitch Axial type 87. The 2200mm pitch Axial type 95 seems excessive, and I have read that pilots were not so happy with it on the Pfalz D.IIIa because it reduced the rate of climb and limited RPMs.

I agree leeG, propeller mods could be useful for us and profitable for 777.
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#21 Stick-95

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Posted 09 February 2013 - 22:10

Gavagai wrote:
I can prove that something is wrong because I can prove that the performance data it is based on belonged to an Albatros D.V, not a D.Va……Rise of Flight and 777 have a track record of making changes when there is proof of error.

In summary, there is proof that our Albatros D.Va is actually an Albatros D.V with a 160PS Mercedes D.III engine.


In my estimation there are two options available to 777 if they wish to fix the Albatros D.Va based on the data presented.

1. 777 can go back through thousands of lines of code for the D.Va and make changes to FM or whatever to bring the performance for the ROF D.Va in line with the presented historical D.Va data.

OR

2. 777 can take off the "a" from D.Va everywhere it appears in ROF as gavagai has proved we already have just a D.V. This requires no programming changes by 777. 777 can then develop a D.Va based on available parameters within its future work schedule which may be easier and result in a better product in the long run.


If 777 selects to do option 2 above we end up with both a D.V (current model) and a new D.Va.

EDIT: there is always option 3
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#22 elephant

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Posted 09 February 2013 - 22:30

It's a good idea, only…
A D.V would require a tiny bit of 3D work to be correct…
(Aileron control cables through the upper wing, modelling of the upper wing control shrouds).

From October '17 the D.V-s were upgraded with Merc. D.IIIa engines.

IMO, they would make the best out of it, if they present each type with two engine options.

D.V early (Merc. D.III) - D.V late (Merc. D.IIIa)
D.Va early (Merc. D.IIIa) - D.Va late (Merc. D.IIIau)

Where the late D.V and early D.Va would have common FM.
The "early" and "late" naming is just conventional.
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#23 Der.Mo

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Posted 09 February 2013 - 23:54

According to Bob Gardner Axial Type 87 was used on Alb.D.V
Axial TP 95 was used on Pfalz D.III, Alb.D.III and Alb.D.Va
http://www.theaerodr...rew-photos.html" onclick="window.open(this.href);return false;">http://www.theaerodr...com/forum/aircr … hotos.html

So why do you want a prop pitch of 2050mm for the D.Va?
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#24 gavagai

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Posted 10 February 2013 - 00:40

I wasn't aware that they were used exclusively? Mostly the record seems like a very sparse sampling of confirmed examples found from particular aircraft. We should contact BoB and see what he thinks.
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#25 J2_Adam

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Posted 10 February 2013 - 04:18

If the current DVa was changed to a DV would the performance actually be correct? I was under the impression that the real DV was only a few miles per hour slower than the real DVa.
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#26 gavagai

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Posted 10 February 2013 - 05:05

If the current DVa was changed to a DV would the performance actually be correct? I was under the impression that the real DV was only a few miles per hour slower than the real DVa.

It should be clear enough now that there was no single airspeed for these Albatros scouts. Each prop would yield a different airspeed and a different climb.

Would the performance of our Albatros be "correct" as a D.V? I suspect that the aircraft (or the test data) was a mess. Neoqb seems to have believed the same based on their preference for the theoretical airspeed above 2km instead of the measured airspeed figures.
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#27 Browning

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Posted 10 February 2013 - 05:09

Unless they had another source we do not know about.
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#28 gavagai

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Posted 10 February 2013 - 05:16

Unless they had another source we do not know about.

True enough, but Viks produced those two French documents as the evidential basis for the Albatros D.Va's in-game performance. If they have additional documentation, let them present it.
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#29 1PL-Sahaj-1Esk

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Posted 10 February 2013 - 10:02

… so what now ? Propeller Mod $ with different pitch positions ? I wonder if the game engine would handle that. Somewhat it looks to me as if the service engineers on aerodromes would tweak the planes and work on the engines, propellers what resulted in quite different performance figures for the planes and pilots after the tuning.
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#30 Mogster

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Posted 10 February 2013 - 14:39

Propellers as mods have been suggested for a year or so now. There's no doubt squadrons used various different ones and enterprising pilots sourced and changed them as they saw fit.

Personally I like the idea of it. The only problem is if there's only really one that works, makes the others a waste of time, then there's flight test data or the lack of it….
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#31 piecost

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Posted 10 February 2013 - 16:01

Prop mods would be cool. I can imagine a really nice graphic in the store of different propellers.

3D model representations. Problem is, some hotshot pilot on the forum would anounce which is best and the others wouldn't sell.
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#32 Browning

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Posted 10 February 2013 - 16:36

There is no best. All fixed props are a compromise between top speed and climb rate.
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#33 Red-Piano

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Posted 10 February 2013 - 16:54

Prop mods would be cool. I can imagine a really nice graphic in the store of different propellers.

3D model representations. Problem is, some hotshot pilot on the forum would anounce which is best and the others wouldn't sell.

Pretty sure a Dev has popped in and shot the idea down before, basically said that they think there's no interest in it and they're probably right.
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#34 Sylvis

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Posted 10 February 2013 - 17:27

777 can take off the "a" from D.Va everywhere it appears in ROF as gavagai has proved we already have just a D.V.

You, sir, are a genious! :S!:
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#35 Mogster

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Posted 10 February 2013 - 17:29

Hmmm, they could have some nice performance graphs showing the differences in climb and top speed. The sort of thing you get in racing sims to explain gear ratios to norberts :)

I like tweaking my plane, I think it's. great idea, especially if it could fund some other FM related changes….
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#36 BillyKid

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Posted 10 February 2013 - 18:56

Wish you were as enthusiastic about pointing out the structural flaws of the DVa as well as the other Albatross scouts as you are about the engine. The Albatross series aircraft inherited from the Nieuports which the Germans copied, the twisting and failure of the single spar of the lower wing under stress, or the excessive flutter of the lower wing which caused numerous fatalitys from the beginning of production. Adding an extra 20 HP by overcompressing the engine to 180 or adding a different pitch to increase rpm by a few would have just added to the inevitible problem. The fix ordered by Albatross and the German inspectorate, to be carried out in the field, was typically not done because the steel boxes added to the lower wing spar to reinforce the spar negated the added performance of tweaking the engines. There is a reason why the average central flier lost faith in the Albatross company. While we are at it on attempting to retweak aircraft, lets turn the Pfalz 3 into the inferior plane that it should be as reported by both central and allied fliers, and also give it the structural flaws that it is supposed to have.
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#37 gavagai

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Posted 10 February 2013 - 19:57

WhiteAce, do you fly the Albatrosses much? By your implication that they have no structural weakness, I'm guessing the answer is 'no.' What is true is that where their structural weaknesses occur doesn't always make sense. The D.II has the most fragile wings in a pullout of the three, and the D.III's aileron's rip off at normal maneuvering speeds. The D.Va is probably the toughest of the three, but its critical dive speed is slower than contemporary French and British scouts. I'm all for making the aircraft as accurate as they can be, that is all.
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#38 Tom-Cundall

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Posted 10 February 2013 - 20:24

If I recall Carl Degelow (maybe it was Josef Jakobs) preferred the Pfalz to the contemporary Albs.

I don't have the source to hand, Peter Kilduff's 'Black Fokker Leader' will tell you.
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#39 Der.Mo

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Posted 10 February 2013 - 21:27

Well, if it´s in the "Black Fokker Leader" book than you just have answered your own question ;)

But i think Werner Voss also prefered the Pfalz over the Albatros
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#40 Haggart85

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Posted 12 February 2013 - 03:27

WhiteAce, do you fly the Albatrosses much? By your implication that they have no structural weakness, I'm guessing the answer is 'no.' What is true is that where their structural weaknesses occur doesn't always make sense. The D.II has the most fragile wings in a pullout of the three, and the D.III's aileron's rip off at normal maneuvering speeds. The D.Va is probably the toughest of the three, but its critical dive speed is slower than contemporary French and British scouts. I'm all for making the aircraft as accurate as they can be, that is all.

There's evidently a lot of issues with the Albatros series, so not only an FM review would be ideal. However, I'd rather have the historical speeds above all else. Climb rate, dive and other advantages over Entente scouts would be nice but that's a lot of work so, at the moment, I'd be willing to settle for speed and or climb rate.

Well, if it´s in the "Black Fokker Leader" book than you just have answered your own question ;)

But i think Werner Voss also prefered the Pfalz over the Albatros

This wouldn't surprise me…the Pfalz was able to dive "better" than the Albatros series, if my memory serves me correct. Quite an advantage to be able to dive on your unsuspecting opponent!
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