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How to do the Albatros series justice


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#81 =FB=VikS

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Posted 12 December 2011 - 17:46

But even the British data for the 150hp SE5 has it faster than the Mercedes-engined D.VII.

Case in point: you need to be very careful when using data from a captured aircraft.

Viks?

Well, its hard to be "careful" as its the only detailed source at the moment. 8-)

As example, lets say we add +10% to its speed, then what gonna be with climb? As this speed wont came from "magic", as when Andrew will change FM to tune speed - whats gonna be with climb? And so on…

PS: is that only rumors or? as i heard that "all (or most) of the german test data burned during WWII bombings"? As seems like all detailed tech specs are comes from these STAe tests.
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#82 MiG-77

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Posted 12 December 2011 - 18:13

PS: is that only rumors or? as i heard that "all (or most) of the german test data burned during WWII bombings"? As seems like all detailed tech specs are comes from these STAe tests.

Not rumor. Ofcourse not all german data were lost, but there are huge gaps because of that. Some german data can found IE in NACA arhives (copied and tranlated after WWI) and private collections.
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#83 Kwiatek

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Posted 12 December 2011 - 18:36

Aren't both test for Albatros with 160 HP engine? As i read Germans used later more horsepower engines - 170-185 Ps so with such engines performacne should be little better. But other hand in Viks charts it 2 lines for RPMs - i understand that one lower RPMs is for climb (1350-1380) and second is for level speed - 1500 RPMs (DV) and 1550 RPMs (DVa) - so its mean that there were used later engines?
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#84 WW1EAF_Paf

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Posted 12 December 2011 - 18:47

Yes Mig, that is most likely Time to Climb.
You can get "Temps de …."
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#85 gavagai

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Posted 12 December 2011 - 20:57

You cannot read text at the bottom of page what those 10,20,30,etc means. Are they climb times?

They are some kind of time. It says "temps de…"

Woops, Paf beat me to it.

But even the British data for the 150hp SE5 has it faster than the Mercedes-engined D.VII.

Case in point: you need to be very careful when using data from a captured aircraft.

Viks?

Well, its hard to be "careful" as its the only detailed source at the moment. 8-)

As example, lets say we add +10% to its speed, then what gonna be with climb? As this speed wont came from "magic", as when Andrew will change FM to tune speed - whats gonna be with climb? And so on…

Again, detailed isn't necessarily more accurate for the purposes of RoF.

Petrovich can deduce a new climbrate from the slightly increased ceiling, i.e. 6250m instead of 5600m.
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#86 J2_Adam

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Posted 12 December 2011 - 21:29

With a few accurate reproduction aircraft in existence, why not use information gathered for these machines?

How about the 2 Alb DVa's with the Merc DIIIa in New Zealand or the DVII with the Merc DIIIaü in the Netherlands? These will be about the best reference for WW1 German aircraft aside from the real thing IMO.
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#87 gavagai

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Posted 12 December 2011 - 21:33

Can you convince them to climb to the aircraft's ceiling? :D
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#88 =FB=VikS

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Posted 12 December 2011 - 21:44

Again, detailed isn't necessarily more accurate for the purposes of RoF.

Show me anything more accurate that these graphs, cause we need as much data as possible.

PS: and yes - RPM curves on these graphs shows that its no less than D.IIIa engine (you can check RPM curves from british test reports on D.IIIa).
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#89 =FB=VikS

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Posted 12 December 2011 - 21:48

With a few accurate reproduction aircraft in existence, why not use information gathered for these machines?

How about the 2 Alb DVa's with the Merc DIIIa in New Zealand or the DVII with the Merc DIIIaü in the Netherlands? These will be about the best reference for WW1 German aircraft aside from the real thing IMO.

Do you think they tested their airplanes on maximum (even for nominal) limits?
As if they did - it would be great to know.
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#90 WhoCares

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Posted 13 December 2011 - 00:04

I have no idea what I am talking about, but anyway a few things I notice when I read those documents.
First thing I noticed is that one engine is referenced just as 160HP (with the engine number) and the other as 160HP (nouveau modele - new model). Also interesting is the different oil capacity 20l the first (which seems to be excessive by the other numbers I can find) vs. 9l the other. Also the weight differences, 16kg empty, 24.5kg loaded.
Just from the weight, and if I had to believe Wikipedia (and here I lose all creditability :oops: ), the 890kg would be a DIII, 915kg a DV(a) and 937kg a DVa(ü) (depending on german, french or english Wikipedia :xx:; by RoF store DIII & DVa, both DIIIa engine).


P.S. I guess these are already known, but there is a series of PDF files of a Flight magazine from 1919 available here: Flightlobal Archive.
The linked and following PDF pages are about the 200HP Mercedes engine tests issued by the "Technical Departement (Aircraft Production) Ministry of Munitions". For this topic are intresting the following pages comparing 160/180/200HP - but of course, all on captured engines and by british standards. But maybe still interesting with respect to the relative performance.
While not relevant with respect to the Albatros, it is interesting to see the 200HP engine with lower power at low RPM, only equal to the 180HP at 1400 and reacing >210 at 1700rpm :geek:
(in the 1919-332ff is a nice long article on the Siemens DIV, even with climb data from Adlershof :D )
If someone feels bored he might find more gems ;)

PPS: Regarding the tests of the Replicas, I'd expect that they made at least some engine test runs to the limits and beyond. And depending when this was done I would also expect that they got some good engine statistics (HP vs RPM) out of those.
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#91 J2_Adam

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Posted 13 December 2011 - 00:23

With a few accurate reproduction aircraft in existence, why not use information gathered for these machines?

How about the 2 Alb DVa's with the Merc DIIIa in New Zealand or the DVII with the Merc DIIIaü in the Netherlands? These will be about the best reference for WW1 German aircraft aside from the real thing IMO.

Do you think they tested their airplanes on maximum (even for nominal) limits?
As if they did - it would be great to know.

I don't know what the requirements are in the Netherlands regarding testing of experimental aircraft. :? One way to find out I guess. One could email the guy. Most likely they have alot more of the proper information at their disposal that most of us.
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#92 gavagai

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Posted 13 December 2011 - 01:39

Again, detailed isn't necessarily more accurate for the purposes of RoF.

Show me anything more accurate that these graphs, cause we need as much data as possible.

Are you trying to say that you can only call data accurate if it is as detailed as those French tests? How do more data points ensure greater accuracy if what is tested is not representative of the larger sample?

How about this?

Attached File  AlbatrosDV.jpg   570.48KB   394 downloads

Even then it is not totally satisfying. The speed at 3km and the climb time to that height don't seem consistent with the data for sea level and 1km. There could be an error there where that airspeed and climb time are actually for 4km… hard to say for certain.
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#93 Chill31

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Posted 13 December 2011 - 03:52

VikS,

My question with regard to the Alb D5 (and the series in general) is how do you think it is possible that the RE8 is faster than the Alb D5a at SL? I mean this as a genuine question.


For all,

Given the data presented, I would entertain any speed for the Alb D5 between 175-187 kmh. We have a lot of data, although it is not all primary source data, for the Alb D5a with Mercedes D3a to fly 187 kmh at 1000m. We also have the data VikS posted, captured test data aside, that shows 172 kmh.

We are also accumulating a more evidence via the data Gavagi posted, the data VikS posted, and the data from theaerodrome forum, which supports a leaned fuel mixture for German aircraft at SL, thus reduced performance, which becomes richer with climb, thus increasing performance through the first 1700m or so.

I plotted the data VikS posted against the current Pup and Camel. The result was that the Alb D5a was faster than the Pup at all altitudes above 500m. It was faster than the Camel above 2500m.

I also plotted the data from Gavagis post and the D5a was faster than the Pup at all altitudes, and it was faster than the Camel above 500m. The 165 kmh at 3000m actually fit the curve very nicely too Gavagi…

I think ROF could use both the D5 and D5a. The D5 could assume a 160hp engine and top speed around 180kmh and the D5a could take the full 187.

Then the question VikS asked: What do we do with climb performance? To be honest, I think it is fine as is! The current Alb D5a reaches 1km at about 3.9-4 minutes which is within about 7% error of store data.
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#94 gavagai

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Posted 13 December 2011 - 04:52

Which Camel are you talking about Chill31? The Camel in RoF is still faster than the D.Va data I posted, at all altitudes, and B2312 would be faster at 3km.

I plotted the data VikS posted against the current Pup and Camel. The result was that the Alb D5a was faster than the Pup at all altitudes above 500m. It was faster than the Camel above 2500m.

Are you taking the data Viks posted to be IAS? Please explain.

Here is a plot of the RoF Camel, the proposed Camel (B2312 with a continuation of the plot to sea-level), the RoF Pup, the proposed D.Va data I posted, and the D.Va data Viks posted, (RoF Camel and Pup in TAS using the conversion formula you provided me):

Attached File  chart.PNG   22.36KB   350 downloads

Then the question VikS asked: What do we do with climb performance? To be honest, I think it is fine as is! The current Alb D5a reaches 1km at about 3.9-4 minutes which is within about 7% error of store data.

The D.Va is way behind in climb compared to other scouts with similar powerloading.
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#95 Der.Mo

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Posted 13 December 2011 - 10:33

Please improve the D.V ATM the D.V is much worser acompared to the D.III. and with both its impossible to catch a Re8 which was a bit slower in reality..
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#96 Hellbender

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Posted 13 December 2011 - 12:05

Here is a plot of the RoF Camel, the proposed Camel (B2312 with a continuation of the plot to sea-level), the RoF Pup, the proposed D.Va data I posted, and the D.Va data Viks posted, (RoF Camel and Pup in TAS using the conversion formula you provided me):

This looks excellent!

Where would a revised Fokker Dr.I fit in all this, considering it's supposed to be slower than the Camel but also outclimb it as well as the SE5a?

As an added benefit, by simply having these adjustments (faster D.Va, slower Camel, even slower Dr.I), the D.VIIF will de facto become "the best plane of the war".
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J5_Hellbender


#97 J2_Wallenberg

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Posted 13 December 2011 - 13:01

+1 for faster Albatros
+1 for slower Camel
+1 for even slower Dr.I (that "climbs like a monkey")

My lack of insight into the technical data (who knows not is bound to believe) I support these requests with knowledge of all the anecdotes I've been presented. These changes make perfect sense to me with the accounts quoted in "Dogfight" by N.Franks.

I say "thank you" in your general direction!
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#98 Tom-Cundall

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Posted 13 December 2011 - 13:13

VikS,

My question with regard to the Alb D5 (and the series in general) is how do you think it is possible that the RE8 is faster than the Alb D5a at SL? I mean this as a genuine question.

I know it is anecdotes so of little use except as a sanity test but these are Bristol fighter combat reports against Albatros scouts- universally they seem to show the Albs as at least as fast as them if not faster.

July 1917 so not sure which type of Albs they would be or which engine

16,000 feet



Attacking DH4's Bristol crew couldn't close due to the speed of planes involved:



As I say not data that you can use but a massive warning sign that what we have at the moment is very wrong.
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#99 winger2

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Posted 13 December 2011 - 13:21

Nice to read all that. But i doubt anything close to that will ever happen. I hope i am wrong.

Winger
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#100 gavagai

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Posted 13 December 2011 - 13:36

Here is a plot of the RoF Camel, the proposed Camel (B2312 with a continuation of the plot to sea-level), the RoF Pup, the proposed D.Va data I posted, and the D.Va data Viks posted, (RoF Camel and Pup in TAS using the conversion formula you provided me):

This looks excellent!

Where would a revised Fokker Dr.I fit in all this, considering it's supposed to be slower than the Camel but also outclimb it as well as the SE5a?

As an added benefit, by simply having these adjustments (faster D.Va, slower Camel, even slower Dr.I), the D.VIIF will de facto become "the best plane of the war".

The revised Camel data I posted would be good until the Spring of 1918 Bender, when the RFC (or now the RAF) finished upgrading its Camels to the Clerget 9Bf standard, which could be comparable to the Camel we have now. But I have never seen any data for a production Camel with the Clerget 9Bf (I'm sure it's out there somewhere), only the prototype testbed.

As for the Dr1, yes, it would be slower than the revised Camel, but still retain an awesome rate of climb.

———————

Anyway, I still think that drop-off from 1km to 3km looks incredibly steep, and doesn't resemble any of the airspeed plots from our other scouts. If 165kmh were for 4km, however, you get a much nicer progression that might look like this:

Attached File  chart2.PNG   20.85KB   236 downloads

I especially like the narrowing performance gap between the Pup and the Albatros here at high altitude, as that goes along with eye-witness descriptions.
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#101 Chill31

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Posted 13 December 2011 - 17:33

Yes gavagi, I used viks data as ias. I will do a flight test this week end on a fixed pitch, fixed mixture airplane to see what speeds I get. For a loose correlation to see what rate the speed falls off. Weather dependent of course…
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#102 gavagai

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Posted 13 December 2011 - 17:50

It would take a lot to convince me that it was IAS and not TAS. You would end up with the TAS steadily increasing up to 120mph (193kmh) at 4km, and the plot would resemble the Fokker D.VIIF or Pfalz D.XII. Instead of the Albatros exhibiting its well-known low and medium altitude advantage over the Sopwith Pup, it would remain inferior at low altitude and would grow superior at high altitude; the opposite of historical record.

The better explanation is that the captured aircraft the French tested were worn out examples.
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#103 J5_vonHippel

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Posted 13 December 2011 - 18:09

What a great read in this thread.
The Alb-series is one of my favoruite aircraft of all time.
But when you fly them in ROF you feel just: MEH! (i.e. nothing)
I have no actual data to provide it´s current performance is wrong, but all I have read about it, suggests that something stinks when it comes to it´s current state in this simulator.
But we have faith that it´ll get fixed soon enough.
We stand by your side in this Gavagai! Keep it up!
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#104 J2_Adam

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Posted 13 December 2011 - 21:31

Chill, (or anyone at 777) I'm not sure if you are interested but here is a link to the NZ Albatorses. It may be beneficial to contact these guys for performance data on the Merc DIIIa and the DVa.

thevintageaviator.co.nz/projects/aircraft/albatros-dva/notes-flying-d-va" onclick="window.open(this.href);return false;">thttp://thevintageaviator.co.nz/project … lying-d-va

I would contact them if I knew the correct questions to ask. In fact I will if someone outlines for me what to ask for.

info@tval.co.nz
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#105 =Fifi=

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Posted 13 December 2011 - 22:03

But when you fly them in ROF you feel just: MEH! (i.e. nothing)

I hope here something could be done for those Albatros series too.
And not only speed revised.
I'd love to FEEL something flying them, like in most of entente ones. That's mainly why i NEVER fly german side.
Only german very interesting to fly is DR1…because you have to care about speed, stall, spin, and landing.
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#106 winger2

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Posted 13 December 2011 - 23:20

But when you fly them in ROF you feel just: MEH! (i.e. nothing)

I hope here something could be done for those Albatros series too.
And not only speed revised.
I'd love to FEEL something flying them, like in most of entente ones. That's mainly why i NEVER fly german side.
Only german very interesting to fly is DR1…because you have to care about speed, stall, spin, and landing.

I cannot see where the Spads are anything harder to fly than an albatros. Both are stupidly easy to fly with some diffrences (not wanting to argue about how good or bad one of both is).
The argument "german planes are easy to fly and dont require brains" may count for noobs. But veterans like yourself should feel most of the planes qually easy to fly.
Anyhow. I would also love to see the albies somewhat harder to fly eg. tendencie to stall or something. Wouldnt change anything since most stalls in ROF are easy to recover from the moment on you learned how to do it. If they had this tendency to stall this could be exploited for maneuvers just like it can be in planes like the N17 or camel. Id welcome that.

Winger
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#107 gavagai

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Posted 13 December 2011 - 23:41

Indeed, it is more or less impossible to snap roll an Albatros.
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#108 =Fifi=

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Posted 13 December 2011 - 23:51

Well at least in Spad you have to care about speed (otherwise it just fell off the sky), tight turns (yes you can, but less than Albies) are harder to perform nicely, and engine management is a bit more interesting.
But right, that's not the point of this thread, and i don't really have any trouble flying all them (except N11 N17 for landings sometime :mrgreen: )

If they had this tendency to stall this could be exploited for maneuvers just like it can be in planes like the N17 or camel. Id welcome that.

Am all with you :D
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#109 J5_vonHippel

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Posted 14 December 2011 - 00:35

But when you fly them in ROF you feel just: MEH! (i.e. nothing)

I hope here something could be done for those Albatros series too.
And not only speed revised.
I'd love to FEEL something flying them, like in most of entente ones. That's mainly why i NEVER fly german side.
Only german very interesting to fly is DR1…because you have to care about speed, stall, spin, and landing.

Yes exactly Fifi!

Just to name a few: the Albatros series, the Pfalz III and the Fokker DVII all feel the same at the moment and that´s contrary to all reports read from the war. But let´s start with the Albatros.

A funny note: If you look at the air war from the german side as it stands now in ROF (Not the real war). I´d never let go of the DR1 for example. The rest I would have scrapped immediately except for the Fokker DVIII perhaps. And that´s a bit funny since there was a lot of aces flying Albatros planes. And don´t get me wrong here, I love flying the Entente planes too.
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#110 Chill31

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Posted 14 December 2011 - 03:32

Ok, I ran a LOT of numbers and did some reading, so here is what I've come up with.

First, the reading to address the Pup-Alb relationship. The quotes I have in "Sopwith Pup" by JM Bruce and Co are all late 1916 and early (first third) 1917 which talk about the Pup and Alb being on approximately equal combat terms above 16-18k feet. I hope someone can chime in here if I'm wrong, but at that point the Pup should be fighting 160 hp Alb D3s, right?

Next, the speed plots. Is it TAS or IAS? Here is my case for IAS based on 180 hp D5a and 160 hp D3.

The Alb D3 vs Pup speed plot with TAS in mph. (aircraft 1 is AlbD3 and aircraft 2 is Pup). Notice how they are the closest in speed at this point. This would give the Pup its greatest advantage over the Alb via turn rate and its ability to keep up with the Alb.

Alb D5 vs Pup and Alb vs Camel. Again all TAS in mph. With 180hp, its advantage in speed is decisive in a late 1917/early 1918 fight. ***also note that the Camel speed DOESNT need to be change to represent historical accounts! Not only that, the DR1 low altitude speed doesnt need to be change either.

AlbD5 vs FD7F. This shows the clear dominance of the D7F in the mid-high teens. So no, the 122 mph TAS of the AlbD5 as it is depicted doesnt even begin to resemble the FD7F.

So there is why I think the numbers are IAS and not TAS in gavagis data post.


With regard to climb rate: The Alb D5a and the N17 have almost identical Power to weight ratios. However, the AlbD5a has a 13% higher wingloading (which equates to an increase in drag) AND it also has a 13% slower climb rate at low-mid altitude. This is why I dont think that its climb rate is far off.

Attached Files


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#111 gavagai

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Posted 14 December 2011 - 04:54

So you're reading the data I posted as IAS too, not just Viks' data? Wouldn't that make our D.Va faster than the Fokker D.VII? One strong point of your idea is that it would make sense of the extreme airspeed drop-off from 1-3km; converted to TAS it looks like a normal decrease. It would also rationalize the claims of F2B/N28 pilots who report the Albatros D.Va as having been quite fast on the level.

With regard to climb rate: The Alb D5a and the N17 have almost identical Power to weight ratios. However, the AlbD5a has a 13% higher wingloading (which equates to an increase in drag) AND it also has a 13% slower climb rate at low-mid altitude. This is why I dont think that its climb rate is far off.

Can you explain the bolded part? You seem to say that it has a slower climb rate in order to explain that it has a slower climbrate.

I've never thought that the D.Va should equal the N17 in climb. My point has only been that something seems fishy when the D.Va is crushed in climbrate by aircraft with similar powerloading, especially in the case of the Fokker D.VII and Pfalz D.IIIa: the D.Va requires an extra 1.7 minutes to 3km!
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#112 J2_Wallenberg

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Posted 14 December 2011 - 10:54

Gav, wasn't the strength of the D.VII a thick upper wing yielding a high-lift profile? That might explain the D.VII's advantage in climbing.

The Fokker D.VII's thick wing section endowed the airplane with good stall characteristics.
Taken from here
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#113 gavagai

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Posted 14 December 2011 - 11:34

Yes it would. Again, I'm not disputing that they should be different, I'm questing the size of the difference. Remember, the Pfalz D.IIIa is right with the D.VII.

Here is a graph I made a long time ago, maybe it will help me get my point across:

Attached File  climbvspowerloading1.PNG   22.67KB   337 downloads
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#114 J2_Wallenberg

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Posted 14 December 2011 - 13:13

If the D.Va was faster than the D.IIIa and the D.VII, maybe a look at the D.Va's wing section might help? I'm pretty sure there could lay a possible reason, a cross-section designed for speed rather than high lift.

I'm neither opposed or conform, nor can I offer any data here.
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#115 hq_Jorri

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Posted 14 December 2011 - 13:29

I'd be surprised if having a thick wing slows you down more than bracing wires?
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#116 J2_Wallenberg

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Posted 14 December 2011 - 14:12

We're talking of difference in time to climb, Jorri…
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#117 gavagai

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Posted 14 December 2011 - 14:17

I'd be surprised if having a thick wing slows you down more than bracing wires?

Well, that depends on how much wire and how thick of a wing…But I agree with you: the D.VII should be faster than D.Va. On the other hand, if the RoF D.VII is equally pooched, then it needs revision, too. After all, it's hard to see how the preeminent scout of 1918 could have such disappointing performance.

Here's what one American pilot had to say about a captured Mercedes engined D.VII:

Attached File  deuce.PNG   76.17KB   295 downloads

And another comment:
Attached File  balanced.PNG   49.1KB   295 downloads
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#118 NickM

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Posted 14 December 2011 - 20:22

I'd be surprised if having a thick wing slows you down more than bracing wires?

This source http://www.hq.nasa.g...P-468/app-a.htm" onclick="window.open(this.href);return false;">http://www.hq.nasa.g...P-468/app-a.htm quotes zero-lift drag coefficients as follows (worst to best):

Fokker E.III = 0.0771

N.17 = 0.0491

Albatros D.III = 0.0465

Fokker D.VII = 0.0404

Camel = 0.0378

SPAD XIII = 0.0367

Dolphin = 0.0317

If these are correct (big if!), then maybe the D.VII's thick-wing-plus-no-wires design really did cause more drag at high speed than was the case for the thin-wing-plus-streamlined-wires designs used by Sopwith, or even just the thin-wing-plus-regular-wires used by SPAD. Notice also how the Albatros D.III is significantly worse than the Camel, SPAD and Dolphin.

Where's piecost when you need him?
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#119 gavagai

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Posted 14 December 2011 - 21:29

I've seen that source before, and it deduces the CDo based on level airspeed, planform area, and power. So if any of the airspeed data is off (and it probably is), then the CDo values are off, too.

Image

Notice that with velocity cubed in the denominator, the estimate is highly sensitive to airspeed data accuracy.
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#120 NickM

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Posted 14 December 2011 - 22:00

…that was my worry. If you put the wrong speed in then you'll get the wrong drag out.
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