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#81 2Lt_Joch

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Posted 05 November 2012 - 19:43

First of all, my post is addressed to the Devs who can interpret the data as well as I can. However, if you insist:
1. Captured aircraft data is not a unreliable source

agreed, it is reliable. However, how is that pertinent to my post?

2. The Germans did not measure TAS with the same methods as the British and French.

Wrong. Yes they did, except for test #9. Do your homework.

You would like to a have a straight-forward comparison of the available performance data, but it is just not possible, Joch. The apples-to-apples data we need does not exist.

How is that in anyway pertinent to my post? The available data is there, the Devs can come to their own conclusions.


Because the Albatros D.III was faster than the figures you give here. Threads at the aerodrome say 175kmh @1km, and estimated 180kmh @sealevel.

That is an estimate, not data. Do you know the difference between the two?

The D.VII had superbly balanced controls, was easy to fly, and more structurally sound. It also had a better rate of climb with Mercedes engines than the Albatros.

That does not address my point, why would they choose a slower fighter?


P.S. your 122mph Camel figure is for a BR1 or LeRhone engine.

Based on what? Do you own the book?

The only account we have of a Camel being faster than an Albatros is from Paul Strahle of Jasta 18, who fought two Camels near ground level (and survived!). TC reported to us that the Camels he fought were from a squadron that had Le Rhone engines. That gives good indication that the maximum airspeed of the Albatros D.V(a) near sea level was somewhere between a Clerget and Le Rhone Camel, i.e. circa 112-122mph.

How is that in any way data?

Norman Macmillan was part of a patrol of 7 Camels that attacked 3 DR.1 and 18 Albatros Scouts on september 1917. He shot down 2 Dr.1s and had no problem evading the Albs. Does that mean that Camels are faster and more maneuverable than Dr.1s and Albs? Your last point is meaningless.

This thread is for Data, unless you have some, why are you posting?
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#82 =FB=VikS

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Posted 10 November 2012 - 11:28

Thanks Joch!

One thing - maybe you had more detailed reports from german fighter competitions?
As maybe there was more than those tables which posted in windsock/profile series.
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#83 Waxworks

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Posted 10 November 2012 - 13:42

Macmillan encountered Triplanes once while with 45 Squadron, on September 11 1917. He led a patrol of seven Camels at 15000 feet on a misty day and east of Langemarck he spotted the mixed formation of Triplanes and Albatros Scouts below.

Macmillan was able to dive at one of the Triplanes and fire, but the Triplane evaded his fire and dived beneath the rest of his formation, where it was dangerous to follow. Macmillan then regained height, but unfortunately McMaking in another Camel had not recognised the peril and had followed an Albatros into the enemy formation. Another Triplane was able to get on McMaking's tail. Macmillan tried to drive this second Triplane off, with his own tail protected by the rest of his patrol, but the Triplane pilot was too good and continued to follow McMaking down.

Then an RE8 blundered into the fight, possibly mistaking the Fokker for a Sopwith Triplane, and Macmillan was forced to take evasive action to avoid a collision. Macmillan lost the Triplane in the mist. McMaking never returned. Several decades later Macmillan saw a photograph of Werner Voss, and recognised him as the Triplane pilot.

So… no Triplanes or Albatros Scouts were lost. One Camel was destroyed and the pilot killed.

Also, if a DIII engine had a speed range of 165-175kmh and a DIIIa 168-172kmh, then by your own logic why would the Germans use an engine which offered no improvement?
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#84 2Lt_Joch

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Posted 10 November 2012 - 23:17

Thanks Joch!

One thing - maybe you had more detailed reports from german fighter competitions?
As maybe there was more than those tables which posted in windsock/profile series.

I will see what I can find. It would be nice if the data was clearer/ more complete.
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#85 Tom-Cundall

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Posted 10 November 2012 - 23:23

Macmillan encountered Triplanes once while with 45 Squadron, on September 11 1917. He led a patrol of seven Camels at 15000 feet on a misty day and east of Langemarck he spotted the mixed formation of Triplanes and Albatros Scouts below.

Macmillan was able to dive at one of the Triplanes and fire, but the Triplane evaded his fire and dived beneath the rest of his formation, where it was dangerous to follow. Macmillan then regained height, but unfortunately McMaking in another Camel had not recognised the peril and had followed an Albatros into the enemy formation. Another Triplane was able to get on McMaking's tail. Macmillan tried to drive this second Triplane off, with his own tail protected by the rest of his patrol, but the Triplane pilot was too good and continued to follow McMaking down.

It should be noted that this account is apparently inaccurate only one F.1 being involved in that fight (Voss) he was however credited twice to Norman MacMillan in the same fight as OOC despite returning home safely. FWIW MacMillan reported seeing 3 Triplanes in the fight.

For his part Voss really did shoot down two 45 Squadron Camels that day though.
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#86 Tom-Cundall

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Posted 10 November 2012 - 23:29

P.S. your 122mph Camel figure is for a BR1 or LeRhone engine.

Based on what? Do you own the book?

121 mph is the fastest speed I can find for the Camel recorded in the improved Bentley 5:7:1 compression engine at 10,000 feet (effectively the Bentley Mk.2)

The Clerget 130-hp we have in game is recorded in example B2512 as 104.5 mph at the same altitude.

And remember "Performance left something to be desired and RFC squadrons using the 130-hp Clerget 9B never found it satisfactory"

Of course pilots report it failing - blowing cylinders and over-heating above 1250 rpm so ours revs too highly as well.
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#87 Waxworks

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Posted 11 November 2012 - 00:52

The account I posted is from the 1969 revised version of Macmillan's 'Into The Blue.' The number of Triplanes was not specified, though he still set the German formation at twenty-one machines. He does not mention his claims for either of the machines he fired on, and it is fairly clearly implied that neither was damaged.

Though there were only two Triplanes at this time, they had both been sent to JG.1, so it seems possible they could both have been in this formation? Otherwise it is awkward for Macmillan to have fired at a Triplane, and then for the same machine he fired at to slip behind McMaking?

'Into The Blue' doesn't mention any other 45 Squadron loss that day and Macmillan claimed that it was their only encounter with Triplanes. Voss seems to have gone on leave shortly afterwards, which might be curious if he had a Triplane to trial. It has been suggested that he may have been lightly wounded.
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#88 Tom-Cundall

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Posted 11 November 2012 - 08:38

The account I posted is from the 1969 revised version of Macmillan's 'Into The Blue.' The number of Triplanes was not specified, though he still set the German formation at twenty-one machines. He does not mention his claims for either of the machines he fired on, and it is fairly clearly implied that neither was damaged.

Though there were only two Triplanes at this time, they had both been sent to JG.1, so it seems possible they could both have been in this formation? Otherwise it is awkward for Macmillan to have fired at a Triplane, and then for the same machine he fired at to slip behind McMaking?

'Into The Blue' doesn't mention any other 45 Squadron loss that day and Macmillan claimed that it was their only encounter with Triplanes. Voss seems to have gone on leave shortly afterwards, which might be curious if he had a Triplane to trial. It has been suggested that he may have been lightly wounded.

No it doesn't you're right. I was going by MacMillan's diary and logbook and 45 Squadron's logbook.

The claims are clearly listed on the Aerodrome's site (which in turn are taken from Over the Trenches by Franks & Shores et al) - although they are erroneously listed as Fokker Dr.1s

http://www.theaerodr...d/macmillan.php" onclick="window.open(this.href);return false;">http://www.theaerodr...d/macmillan.php

Probably Macmillan with the benefit in hindsight of how many Triplanes were really in that fight and how many the Germans lost that day omitted his claim for two of them when writing 50 years later. Interestingly his notes and anecdotes and drafts of other books are in his extensive papers in the IWM archive. He was heavily involved in the reunions of 45 Squadron and collecting their histories, diaries and anecdotes after the war and up until his death.

Voss' page on the Aerodrome lists as one Sopwith Camel (McMaking) and one Bristol Fighter F2B or Sopwith Camel on the same date.

http://www.theaerodr...ermany/voss.php" onclick="window.open(this.href);return false;">http://www.theaerodr...ermany/voss.php

The accounts that I have read credit Voss with the two 45 Squadron Camels - not sure where the confusion otherwise comes from but I'm sure one of the German enthusiasts on here can enlighten us around that.
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#89 2Lt_Joch

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Posted 11 November 2012 - 12:03

P.S. your 122mph Camel figure is for a BR1 or LeRhone engine.

Based on what? Do you own the book?

121 mph is the fastest speed I can find for the Camel recorded in the improved Bentley 5:7:1 compression engine at 10,000 feet (effectively the Bentley Mk.2)

The Clerget 130-hp we have in game is recorded in example B2512 as 104.5 mph at the same altitude.

And remember "Performance left something to be desired and RFC squadrons using the 130-hp Clerget 9B never found it satisfactory"

Of course pilots report it failing - blowing cylinders and over-heating above 1250 rpm so ours revs too highly as well.

Totally agree, which is my point.

The 122 mph max speed for a 130 hp Clerget is clearly wrong, so the 116 mph max speed for a Alb. DVa quoted in the same book may be just as wrong.
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#90 2Lt_Joch

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Posted 11 November 2012 - 12:19

In the excerpt that I have from "Into the Blue", Macmillan clearly states that there were 3 DR.1s present and he strongly implies that he shot down two, although he does not say he saw them crash. He was officially credited with two.



The accounts that I have read credit Voss with the two 45 Squadron Camels - not sure where the confusion otherwise comes from but I'm sure one of the German enthusiasts on here can enlighten us around that.

I also read the Voss version. The contradiction is not surprising, you often see that, not just in pilot accounts, but any type of combat reports. Because of stress, fear, adrenaline, target fixation and the short time span in which these fights occur, participant's memories of the events is often wrong.

Recent studies have shown that because of the fight/flight hardwiring of our brains, a human brain under life threatening stress is concentrating purely on survival, not on recording the event. Afterwards, the brain will reconstruct the memory from various pieces, which may or may not be correct. That is how you get the now well documented cases of eyewitnesses identifying the wrong persons, even just a short time after the event.
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#91 gavagai

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Posted 11 November 2012 - 14:42

The 122 mph max speed for a 130 hp Clerget is clearly wrong, so the 116 mph max speed for a Alb. DVa quoted in the same book may be just as wrong.

What rule of logical inference is that? Modus riduculans?

Here is what it comes down to, Joch. We have to decide on what to believe. On the one hand we have a handful of performance tests that say the Albatros was slower than the Camel. On the other, we have combat reports and observations of level flight airspeed that say the Albatros was faster than the Camel. Which is right?

By itself it would be a difficult decision about where to place our belief if the above were the only information. You agree to that much, I think.

However, we have a wealth of evidence that points to performance problems with the Clerget 9b engine. Moreover, we've never seen anything about quality control problems with the Mercedes D.IIIa engine. That tips the scale of credibility toward the combat reports.

Perhaps the best Clerget Camel really was faster than the D.Va, but, by and large, the ones at the front in France were not. That is the inexorable conclusion.
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#92 BADMUTHA

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Posted 11 November 2012 - 14:56

So is there no factual testing that shows the Albatros D.Va is faster than the Camel? Anecdotal evidence is just that, anecdotal, just because 100 people say they saw a UFO doesn't mean they actually saw a UFO.
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#93 Mogster

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Posted 11 November 2012 - 15:44

I know using data from replicas is full of problems, but it would be interesting to know what the max sea level speed of the TVAL Albatros DVa is.

Which engine does it have, Diiiau?
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#94 gavagai

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Posted 11 November 2012 - 15:47

So is there no factual testing that shows the Albatros D.Va is faster than the Camel? Anecdotal evidence is just that, anecdotal, just because 100 people say they saw a UFO doesn't mean they actually saw a UFO.

Not exactly. If you believe the 187kmh figure for the D.Va at 1km, then it would be faster than the airspeed for B2312 (a production Camel) at the same altitude.

However, Red, I have a question for you. Do we know that "data" from WW1 was more reliable than anecdote? You seem to be assuming that it is without any justification for that conclusion, except for the fact that it comes with a number.

Treating performance data from WW1 as fact is like receiving a science lab report from a sixth grader and publishing their data in a journal.

I know using data from replicas is full of problems, but it would be interesting to know what the max sea level speed of the TVAL Albatros DVa is.

Which engine does it have, Diiiau?

They have both, a D.IIIa and a D.IIIau Albatros D.Va. I would be curious to know that too, and to have them to a side-by-side race with the Camel at, e.g. sea level, and at 1km.
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#95 BADMUTHA

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Posted 11 November 2012 - 15:59

I have no idea, I just mean to ask questions and hope you understand it's probably hard for 777 to tweak their flight models based on anecdotes.

What is the overall difference in MPH between the camel and the D.Va if both were be corrected to what you think is accurate?
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#96 gavagai

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Posted 11 November 2012 - 16:07

Not a lot, about 10kph (6mph), plus or minus a little bit.

It would upgrade the D.Va to "mediocre." :lol:…But I don't want to see that change without appropriate stall behavior (and decreased roll rate) for the D.Va.
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#97 BADMUTHA

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Posted 11 November 2012 - 16:33

Doh! Now that hardly seems significant enough to warrant a change, although maybe it's small enough to warrant a change depending on how you look at it.

So you want decreased roll rate, stalls and 6mph faster…that sounds like the D.Va will be a real pig if they make those changes
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#98 gavagai

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Posted 11 November 2012 - 16:47

It's the difference between the D.Va being able to extend away, or being dead-meat as soon as it is spotted. All those Camel pilots who lamented not being to run down German scouts (in a dive or in level flight) certainly thought it was a signficant difference.

Being able to stall can be advantageous if the pilot knows how to use that trait. For example, your SE5a has one of the best snap roll behaviors in the sim.

Fwiw, right now the difference is ~12mph in favor of the Camel.
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#99 BADMUTHA

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Posted 11 November 2012 - 16:50

How far off is the camel FM in terms of speed, maybe that just needs to be corrected to level the playing field more.
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#100 gavagai

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Posted 11 November 2012 - 16:59

It matches the protype airspeed test data perfectly, which is about 5-7% faster than the production type, depending on altitude, i.e. about 7mph. So, changing that alone would not be a game-changer.

But, regardless, the Camel's engine revs are 200rpm too high. Compare them to the Sopwith Tripe. That alone merits a look at the model.
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#101 Mogster

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Posted 11 November 2012 - 17:17

Doh! Now that hardly seems significant enough to warrant a change, although maybe it's small enough to warrant a change depending on how you look at it.

So you want decreased roll rate, stalls and 6mph faster…that sounds like the D.Va will be a real pig if they make those changes

Well from his TVAL write up Gene DeMarco seems to suggest it does oink a bit…. But if that's the way it was then bring it on.

Also the SE5a deserves these changes as it'd make the SE5a (and the Fokker DVII) more desirable as they were in reality. I'd be happy if this thing started with a re-work of the Camel as we have the data, with the alternative data applied to the Camel on its own would make it less easy to run down other scouts as you can currently. I like the Camel but even as a fan it feels wrong.
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#102 2Lt_Joch

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Posted 11 November 2012 - 21:52

So is there no factual testing that shows the Albatros D.Va is faster than the Camel? Anecdotal evidence is just that, anecdotal, just because 100 people say they saw a UFO doesn't mean they actually saw a UFO.

Agreed.
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#103 hq_Jorri

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Posted 11 November 2012 - 21:56

How many people in this case have not seen a UFO? In other words, how many reports are there of the contrary?
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#104 SYN_Vander

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Posted 14 November 2012 - 21:20

Interesting bit by Dan San Abbot:

http://www.theaerodr...ifferences.html" onclick="window.open(this.href);return false;">http://www.theaerodr...com/forum/aircr … ences.html

So 187 km/h for both Albatros DV and DVa? What are his sources?
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#105 gavagai

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Posted 14 November 2012 - 21:34

Interesting bit by Dan San Abbot:

http://www.theaerodr...ifferences.html" onclick="window.open(this.href);return false;">http://www.theaerodr...com/forum/aircr … ences.html

So 187 km/h for both Albatros DV and DVa? What are his sources?

Reading DSA's posts at the aerodrome is like reading a Platonic dialogue:

DSA: "Aircraft X did 123.54 and 29534.54 and had 2181.4923 widgets."

Others: "Yes Dan!" "You are so wise!" "Indubitably!" "How could it be otherwise?!"

:lol:

Anyway, I think it was Imperator who explained that DSA was wrong about the Mercedes D.IIIau engine and its introduction date. Notice that DSA implies that the Albatros D.Va had the D.IIIau engine in Fall 1917, and that the D.V had the D.IIIa engine (apparently, DSA believed that any Mercedes D.III engine with a horizontal air pump was a D.IIIau, and that is not true).

Because the D.V production actually began in April 1917, it originally shipped with the Mercedes D.III engine, not the 170ps D.IIIa. The other bits I've read at the aerodrome and other sources indicate that the D.IIIa engine was not ready until July or August 1917, in time for the OAW Albatros D.III and the Albatros D.Va in September-October.

This thread suggests some dates for Mercedes engines:
http://www.theaerodr...iii-series.html" onclick="window.open(this.href);return false;">http://www.theaerodr...com/forum/aircr … eries.html
1916.08.15 Mercedes D-III(160PS/162,5HP)
1917.02.01 Mercedes D-III(175HP) [This is a dubious figure!]
1917.09.15 Mercedes D-IIIa(170PS/180HP)
1918.03.01 Mercedes D-IIIaü(180PS/200-217HP)
1918.10.15 Mercedes D-IIIavü(185PS/200-220HP)

The PS-HP conversions are misleading because they don't even stand for power at the same RPM (PS was rated at only 1400rpm, and the British rated HP at something higher).

—————-

Anyway, what is probably true is that the Albatros D.V and D.Va had about the same airspeed, 187kmh @sealevel, and 188kmh @1km. The Albatros D.V reached that airspeed with the Mercedes D.III engine, and the heavier D.Va needed the more powerful Mercedes D.IIIa engine to do the same.

Here is a table from Guttman's SE5a vs. Albatros DV:
Attached File  DV.png   229.44KB   606 downloads

I can only guess that the D.III and D.V used different props. Otherwise the ridiculously different climb rates don't make sense (maybe some very aggressive rounding to whole numbers, too). The D.V's higher ceiling (as mentioned by DSA) is consistent with a coarser pitch.

But I doubt the D.III climbed that well. According to those figures the Albatros D.III would outclimb our Fokker D.VIIF at low altitude. That is another reason why WW1 performance data has to be balanced by information from non-quantitative sources.
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#106 gavagai

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Posted 14 November 2012 - 23:16

And here are more precise production figures for the Mercedes engines:
http://www.theaerodr...iii-series.html" onclick="window.open(this.href);return false;">http://www.theaerodr...com/forum/aircr … eries.html

DIII
1914 9 total

1915 1165 total

1916 2379 total

1917 1696(other sources say 1604) total
January 193
February 256
March 371
April 344
May 324
June 169
July 20
August 10
September 7
October 2
November 0
December 0

1918 1


DIIIa
1917 2644 total
June 45
July 330
August 420
September 441
October 483
November 457
December 468

1918 4044 total
January 428 (D.IIIa)
February 328 (D.IIIa)
March 283 (D.IIIa)
April 370 (min.200-D.IIIa/max.170-D.IIIaü)
May 405 (min.110-D.IIIa/max.295-D.IIIaü)
June 413 (min.22-D.IIIa/max.391-D.IIIaü)
July 498 (1-D.IIIa/497-D.IIIaü)
August 495 (D.IIIaü)
September 480 (D.IIIaü)
October 229 (D.IIIaü)
November 100 (D.IIIaü)
December 15 (D.IIIaü)

And Albatros D.V(a) production batches that Viks posted before:
Attached File  Albs_Serials.jpg   111.4KB   590 downloads
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#107 HotTom

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Posted 14 November 2012 - 23:38

And here are more precise production figures for the Mercedes engines:
http://www.theaerodr...iii-series.html" onclick="window.open(this.href);return false;">http://www.theaerodr...com/forum/aircr … eries.html

Gav,

That is an amazingly informative thread by some posters who clearly know their stuff!

I'd never stumbled over it before. Definitely added to my bookmarks.

Thanks for the link!

:S!:

HT
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#108 gavagai

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Posted 15 November 2012 - 00:03

Glad you like it! Did you notice the lag time between engine production and when they were actually used in scouts? The D.IIIau engines were being manufactured in April 1918, but the first Fokker D.VII with a D.IIIau wasn't accepted until June. :o
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#109 HotTom

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Posted 15 November 2012 - 00:22

Glad you like it! Did you notice the lag time between engine production and when they were actually used in scouts? The D.IIIau engines were being manufactured in April 1918, but the first Fokker D.VII with a D.IIIau wasn't accepted until June. :o

Well, as I understand it, the first few were built right at the end of April the engines accepted in May by Fokker and the aircraft accepted by the German air service in June. It describes the German military testing unit that apparently flight-tested every aircraft before it was accepted. There is a vague reference to Fokker's "reputation," which I took to mean they didn't entirely trust his factory's quality control department. :mrgreen:

One of the mysteries that is mentioned but not solved in that thread is the question of rebuilds. I know Mercedes had rebuild facilities in both Belgium and Germany and, clearly, D.IIIas were upgraded with the domed pistons to D.IIIau standards when they were rebuilt. But no one seems to know how many actually were upgraded nor how common or scarce the au (both new and rebuilt) engine was.

It's a looong thread but kind of like reading a detective story. Thanks again!
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#110 Gunsmith86

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Posted 18 November 2012 - 23:13

Glad you like it! Did you notice the lag time between engine production and when they were actually used in scouts? The D.IIIau engines were being manufactured in April 1918, but the first Fokker D.VII with a D.IIIau wasn't accepted until June. :o

Well, as I understand it, the first few were built right at the end of April the engines accepted in May by Fokker and the aircraft accepted by the German air service in June. It describes the German military testing unit that apparently flight-tested every aircraft before it was accepted. There is a vague reference to Fokker's "reputation," which I took to mean they didn't entirely trust his factory's quality control department. :mrgreen:

One of the mysteries that is mentioned but not solved in that thread is the question of rebuilds. I know Mercedes had rebuild facilities in both Belgium and Germany and, clearly, D.IIIas were upgraded with the domed pistons to D.IIIau standards when they were rebuilt. But no one seems to know how many actually were upgraded nor how common or scarce the au (both new and rebuilt) engine was.

It's a looong thread but kind of like reading a detective story. Thanks again!


Windsock datafiles No.3 Albatros D.V page 1:
Serie production and delivery of the Mercedes D.IIIa (in text it is D.IIIa but i belive that it should be the D.IIIau update because of the late date. ) began in March 1918 and some 1500 high compression pistons were available every month for retrofitting to older Mercedes powerplants.
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#111 Gadfly21

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Posted 19 November 2012 - 00:20

How far off is the camel FM in terms of speed, maybe that just needs to be corrected to level the playing field more.

We have to give credit to the devs, because they've done a great job overall.

Based on what we can find, considering performance numbers and large-scale patterns in the anecdotal evidence (consensus largely points towards the Alb being faster than the Camel), the Alb D.Va should have a top speed of about 185-188kph. The game version has a top speed of 175kph TAS. Likewise, the serial production Camel should have a top speed of maybe 175-180kph TAS, but it goes 191kph TAS.

So, for each plane, the top speed is off by only 10-15kph. This is incredibly close, considering each plane individually. However, the difference ends up giving the Camel a net edge of 25kph over the Albatross, which is huge. Fixing the speeds for both planes would give the Alb a 10-5kph advantage, which is more consistent with the overall patterns that come up in combat reports. The Alb should dive faster than a Camel as well, in part due to the limit the Camel should have on RPMs.

That said, the Alb also needs to be nerfed in terms of structural strength (vertical dive only shears the ailerons, with no damage to the lower wing; D.Va would be tougher than a D.V or D.III though due to the extra struts), needs more adverse yaw, and needs to be more pitch sensitive, so that the controls aren't as well harmonized.
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#112 hq_Jorri

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Posted 21 November 2012 - 22:53

Analysis of 1917 German scouts with Mercedes engine performance data by Gavagai:

Circa 1917 German Scouts


Mercedes D.III engines

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#113 Rumcajs

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Posted 09 December 2012 - 13:12

Just found these documents on the internet.
sjharker.customer.netspace.net.au/WWIAircraftPerformance.pdf
home.comcast.net/~clipper-108/AIAAPaper2005-119.pdf
I'm not sure if they have already been posted here on the forums but i found the data in those files interesting.
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#114 gavagai

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Posted 09 December 2012 - 15:06

The second one has been posted before, and its known that its analysis methods are unsound.

The first one I haven't seen before, but I can see that it is just a compilation of secondary sources. In some cases it doesn't bother to specify altitude for airspeeds, even where they are known. It's a neat idea to try to put all that stuff together, but the end result is an amalgamation of an amalgamation that obscures the mixed origin of the data points.
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#115 piecost

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Posted 23 March 2013 - 00:55

Pilot June 1999

Flying the Aircraft of the Shuttleworth Collection, Andy Sephton

"Regard the gyroscopic and torque effects, in flight the phenomena have roughly the same effect as that on a medium Merlin-powered fighter. On the ground, however, one must be especially careful. The Sopwith Pup, for example, even with full right rudder applied, will swing to the left if the tail is raised too early in the take-off run. If it is lifted too late, the machine will be airbourne in the thee-point attitude with the attendant possibility of stall and catastrophic wing drop. A compromise is called for and can only be found by practive and experience, but the nose will swing to some extent to the left and this must be allowed for when assesing the runway area required.

The ideal landing technique follows that recommended when the types were current. The engine is shut down by cutting the fuel at the start of of the final turn and the aircraft side-slipeed down the approach to just before touchdown. This manoeuvre can be achieved most precisely in the Sopwith types, as the yaw inertia is low and the rudder powerful."
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#116 hq_Jorri

hq_Jorri
  • Posts: 14143

Posted 23 March 2013 - 08:24

Note that they have a Sopwith Pup and a Sopwith Triplane they fly, the probably means these two planes when he says 'the Sopwith types'?
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#117 piecost

piecost
  • Posts: 1318

Posted 23 March 2013 - 11:57

Yes, I think that the Triplane was flying at that time
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#118 wangpipixiong

wangpipixiong
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Posted 08 July 2013 - 08:55

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#119 piecost

piecost
  • Posts: 1318

Posted 26 December 2014 - 16:18

Flying the Pup

Andy Sephton

Richard Shuttleworth purchased the Collection's Pup in 1936. It was orignally being constructed as a single-seat Scout-Pup was a later name-but the 1918 armistice intervened and it was converted, along with nine other aircraft still on the Sopwith production line, into a Dove. This was a civilian, two-seat variant of the military Pup. Shuttleworth reconverted the machine, returning it to its single-seat configuration.

I learned of the Pup's existence when I was still a young aero modeller. Although I designed a small, rubber-powered version of the machine, it never came to fruition. But I did witness flights of several other model Pups and all showed the characteristics of a delightfully stable machine, bouncing along on light, thermally air. This was a vision that has stayed throughout my acquaintance with the aircraft and it hasn't burst yet.

My first flight in the Collection's Pup was on the morning of a Sunday airshow at Old War­ den in 1995. The air was light, bouncy even. There was puffy cumulus at 2,500 feet and a light, south-westerly drift of warm summer air. I was not disappointed. The light and responsive controls, coupled with a fair field of view and a comfortable cockpit gave the impression of an ideal Sunday flyer. But then, as I looked for­ ward along the single Vickers machine-gun, I realized that this delightfully pleasant little aircraft was also, in the right hands, a potent war machine. 'In the right hands' is the key, for although the Pup is an enchanting machine to fly, it does have some interesting take-off and landing characteristics to fly it effectively, a mastery of the delights of operating a rotary engine is essential.

So, let's look at the engine. The Le Rhone in the Pup is a nine-cylinder, four-stroke motor, aspirated by two valves in each cylinder head, and controlled by a single push/pull rod. The associated rocker has an exhaust valve at one end and an inlet at the other. The advantage of the single push rod system is lightness, which is essential for the rotary. The disadvantage is that it is impossible to overlap the exhaust and inlet valve timing, so perform­ ance is limited. Nevertheless, it does provide more than adequate power for the Pup.

All rotary engines are characterised by a hollow crankshaft which is attached to the air­ frame. Around it rotate the cylinders and crankcase, the propeller being attached to the latter. The result is a light power plant that does not require liquid cooling. But it can overheat on the ground with prolonged running and the gyroscopic precession of the rotating mass causes some not insignificant problems for the pilot. The handling of the engine is also specific-any pilot errors in this area can quickly lead to power plant failure.

The pilot of the Pup is presented with a cockpit containing few flight instruments and, relatively speaking, many engine-associated controls, systems and indicators. The fuel is transferred to the engine by air pressure generated by a cockpit handpump and/or a Rotherham propeller pump. The latter is fitted in the main propeller slipstream on the port forward wing strut and the former is fixed on the right side of the cockpit. At the base of the cockpit handpump is a small tap. Setting it perpendicular to the feed pipe isolates the pump; turning it parallel with the pipe allows the tank to be pressurised by the pilot; finding the correct position, at about 45° to the pipe, vents the air system to atmosphere. The various positions of the tap can be used in flight to control tank over-pressure, tank under-pressure and to possibly cure an air leak. After flight, the tap is used to equalise tank pressure with ambient. There is also an air pressure gauge to monitor the fuel tank pressure-the maximum is 2.5 psi-and a Jones valve, which acts as an engineer­ adjustable pressure relief valve.

Oil flow to the engine is total loss; an on/off tap, which is inaccessible to the pilot, is fitted in the line under the tank. Oil flow is confirmed by an oil pulsator fitted to the lower left of the instrument panel. The oil meniscus moves slowly up and down in sympathy with engine rpm when the engine is running, thus confirming that oil flows. However, given the blue mist that can readily be seen emitting from the engine, and the pleasant odour of castor oil in the cockpit, the pilot is in no doubt as to whether or not oil flows to his rotary! Nevertheless, the pulsator may have one use. In certain circumstances e.g. failure of the rpm gauge, engine rpm can be checked by timing the rate of pulsation and comparing the result to a calibration chart. But, as with the oil flow, in practice, the pilot's perception is as good an indication of engine rpm as any-in this case it is achieved by ear and airframe feel.

A fuel on/off tap is located in the fuel line, forward, on the lower left side of the cockpit. Fuel flow to the engine is pilot-controlled by two, coaxial levers fitted in a quadrant marked from one to ten on the left cockpit wall. The larger, outboard lever, referred to as the blocktube or fuel/air lever, is directly connect­ ed to a blocktube carburettor, which is located on the pilot end of the extended hollow crank­ shaft. It controls airflow to the engine and to a certain extent fuel flow. The inboard, smaller lever, referred to as either the petrol lever, the fine adjustment lever or the tampier filter tap lever, directly controls fuel flow into the block­tube.

Contrary to popular opinion, rotary engines of the two lever type, such as fitted to the Pup, can be modulated over a range of rpm. In practice, this is about 700 to 1,150 rpm on the ground, noted on the cockpit rpm gauge, which equates to about 50 to 100 per cent of available power respectively. The approximate lever positions for 700 rpm are 3.0 on the blocktube lever and 2.5 to 3.0 on the petrol lever. For 1,150 rpm, the approximate posi­ tions are 7.0 and 3.5 to 4.0 respectively. For a given blocktube position, if the petrol lever is set too far forward (too rich), or too far back (too lean) the engine will cut. A rich cut should clear in about thirty seconds, which is disastrous in low-level flight; a lean cut can be cured in about five seconds. The trick for safe operation of a rotary is to know when the engine is running rich or weak and what to do if it is.

Finally, the engine suite is completed by a single ignition system with magneto on/off switch on the instrument panel and a 'blip' but­ ton on the control column, which cuts the ignition when depressed. Although the engine can be modulated by judicious use of the blip switch, it is not recommended as a primary engine control. The engine is 'shock' loaded every time the blip switch is pressed and con­ tinuous flight with the ignition switched off leads to oiled and fuel-fouled plugs. Better to use the petrol lever to modulate the engine over its lim­ ited range-or if even less thrust is required, to shut the engine down completely by selecting the petrol lever to the fuel off position.

Prior to flight, normal checks of locking wires, wire tensions, control integrity and airframe condition must be made. Perhaps the most important check is that of the under-wing hoops. They are fitted to the lower wing spars, via metal cups, and serve to protect the lower wing aileron horns in the event of a wingtip striking the ground. They give as good a hint as any that the ground-handling of the machine is special.Cockpit entry is via a single footstep in the left fuselage side and a hard point on the wing-root. When seated, the pilot notes a good field of view for an aircraft of the period, with a gap cut into the centre panel of the upper wing centre section to improve the view forwards and upwards.

Rotary engine time is a precious commodity - time between overhauls is measured in a few tens of hours. So, given the propensity to overheat on the ground and the wish not to waste precious engine time, the Collection parks the rotary-engined aircraft at the mar­ shalling point of the runway-in-use prior to flight. Following strap-in, the pilot immediately carries out normal pre-take-off vital actions as his hands will be full once the engine is running. The harness is secured, the flight con­ trols checked and goggles are positioned and secured-the cockpit environment of the Pup is windy, get into the air with loose goggles at your peril.

When settled and prepared, the pilot calls ready to start to the groundcrew. The fuel is confirmed on, the ignition off and the engine levers are set closed. The groundcrew turns the engine oil on and confirm the same with the pilot. Each engine cylinder is then primed in turn by depressing the respective exhaust valve and injecting a measured amount of petrol by syringe. Meanwhile, the pilot pumps the fuel tank to a pressure of 2 to 2.5 psi and checks that the pressure is maintained. The groundcrew turns the engine over several revolutions to distribute and mix the fuel. When the groundcrew calls ready, the pilot sets the blocktube to about 3.0, rechecks fuel tank pressure, holds the control column fully back, calls "Contact" and sets the ignition on. The groundcrew confirms that there is one of their number holding the tail down and that chocks are in position.

The propeller is swung. If all has been set and primed properly, the engine bursts into life with its characteristic staccato crackle, the air­ frame twists in opposition to the torque and a cloud of blue smoke is quickly carried away in the slipstream. The pilot waits for the prime to burn off then, as the engine dies, he advances the petrol lever slowly towards the expected running position. This will vary according to ambient conditions but will never be more than about 0.5 of a division from position 3.0. The engine is warmed at about 700 to 800 rpm for about fifty seconds as the lever positions for smooth running are essayed.

The engine will go from rich to lean and vice versa with a petrol lever movement of between one-eighth to one-quarter of an inch around position 3.0. A lean engine exhaust sounds light but rough, a rich exhaust note is harsh and heavy. With practice, the two states can be heard and felt through the airframe and if the pilot is diligent, they can be noted as a slight drop in rpm as the over-rich or over-lean state is reached. A rich cut is cured by closing the fuel lever and awaiting engine pick up-it should pick-up within thirty seconds in the air, but it will stop and remain stopped on the ground. A lean cut is remedied by slightly advancing the petrol lever and the engine should pick up within a few seconds, either on the ground or in the air.

At this point the pilot cannot fail to be impressed by the smoothness of the rotary when compared to radial engines. This is probably due to the big end, the largest mass in the engine, being stationary in the rotary engine, whereas it rotates in the radial.

After a fifty-second warm-up, full power is tested. The blocktube lever is advanced to about position 7.0. As there is not enough fuel flow to maintain running, the engine lean cuts. The petrol lever is then advanced slowly until the engine picks up and the lever posi­ tion will be between 3.5 and 4.0. Again, the rich and lean positions are noted and this time the lever spread is about a quarter to half an inch. The maximum rpm is noted, normally about 1,050 rpm, but provided it is above 1,000 rpm, the flight can go ahead. Time at high power is minimised, about thirty seconds is reasonable. Power is then reduced to minimum by first retarding the petrol lever to cause a lean cut, then resetting the blocktube to the slow-running position, then resetting the petrol lever as appropriate.

Following a quick cockpit check and a confirmation that the fuel tank air pressure is sufficient to commit to flight , the chocks are waved away. The blip button is now used for the first time. As the low power setting of 700 rpm provides about fifty per cent of maximum thrust, if engine power is not killed when the chocks are removed-given that the machine has no brakes-the machine will jump forward and strike the groundcrew. When the groundcrew is clear, the blip button is released and the blocktube advanced, followed by the same with the petrol lever, both being set to the positions for high power noted during the ground run. The aircraft accelerates briskly and the pilot must guide the machine between two limiting handling areas. If the tail is raised too quickly, even with full right rudder applied, gyroscopic pre­ cession will cause the machine to yaw about 30° to the left. Following that, if right yaw is rapidly applied to control the situation, the propeller will certainly strike the ground. Conversely, if the tail is kept on the ground too long, the aircraft will take to the air close to the stall, with all the associated dangers. The tail must be lifted slowly and progressively as the aircraft accelerates.

As airspeed increases, the propeller unloads and the engine rpm increases. Fuel arrives at the engine via the hollow crankshaft and is fed to the engine via tubes running along the sides of the cylinders. The increased centrifugal force produced by the accelerating engine will enrich the mixture. Therefore, if the petrol lever is not retarded slightly on take-off, the engine will suffer a rich cut and the pilot will get to practise Engine Failure After Take-Off drill.

Climbing at the best climb speed of 65 mph, the delights of the Pup become clear. The controls are light and effective, the machine is relatively stable in pitch and roll, but it does wander a little in yaw. With four ailerons and no ameliorating devices, adverse yaw is apparent, but is easily controlled with the effective rudder. Gyroscopic precession is always there-there is no getting away from it with a rotary engine-but it is not excessive. At medium to high airspeed it is no worse than that of a Griffon-powered Spitfire, but the rudder power, although effective, is a lot less.

The stall qualities are also good, but they must be tested with the engine off. The fuel lever is retarded and the pilot tips forward in the seat as drag takes over from thrust. There is slight but adequate warning of the coming stall in the form of airframe buffet and stall break occurs at about 35 mph indicated. After aerodynamic recovery, the petrol lever is advanced and the engine bursts into life with associated torque roll, precession turn and airframe acceleration. But, as experience is gained, the apparently random movement of the aircraft becomes predictable and is easily contained with slight pressure on the relevant (aerodynamic) control. As successive manoeuvres are attempted, the pilot must take special heed of the engine note. As speed is increased, for similar rea­ sons to those on take-off, the petrol lever must be retarded to prevent a rich cut. As alti­ tude is increased and the air gets thinner, the petrol lever must be further retarded to pre­ vent a similar occurrence. Conversely, the petrol lever must be advanced as airspeed and altitude reduces to maintain smooth run­ ning and to prevent a lean cut.

A descent with engine on is only possible in a fast dive, so entry to the circuit pattern must be made engine off. The petrol lever is retarded and the engine stopped, although it does windmill in the slipstream. The machine glides well at 65 mph and a forced landing pattern is set up. The ideal turn-in-point is about 800 feet, a half mile or so from the air­ field, in the late downwind position. A constant aspect turning approach is then made, aiming to land about a third of the way into the airfield and keeping the speed slightly fast. At this stage, there is no substitute for a little excess kinetic .energy; excess energy is easily lost in side-slip, but without an engine, it is impossible to gain. So, in the latter stages of the approach, heavy side-slip is used to bring the touchdown to a point 100 yards or so into the field. Just before touch, the engine levers are reset to the running positions and as the engine picks up it is killed on the blip button. It should then be ready for instant use if it be necessary to help stop a swing during landing.

To prevent a swing starting during the landing run, the landing must always be made into the wind. It must also be a three-pointer. Wheeled landings invariably lead to a ground­ loop to the right, owing to the gyroscopic pre­ cession of the rotating engine causing the nose to go to the right as the tail is lowered. This, coupled with the narrow forward under­ carriage and the lack of airflow over the rud­ der, gives the pilot no chance of recovery (hence, under-wing skids).
While the Pup slows after landing, the blip button is released and as the engine fires, the control levers are retarded to achieve 700 rpm or so. The aircraft deceleration is pro­ longed by blipping, but the aim is to allow the engine to run at low power for about thirty seconds to temperature stabilise the cylinder and crankcase. The ground roll-out distance is not critical at Old Warden, however, great care must be taken not to allow the concen­ tration to drift-until she stops, the Pup is still waiting to swing and to catch the unwary. The machine is guided off the duty runway and the engine is shut down by closing the petrol lever and fully advancing the blocktube. When stopped, the silence is deafening. The engine clicks and snaps as it cools, the air-frame dies. The ignition is checked off and fuel tank air pressure released with the tap at the base of the cockpit pump. The pilot vacates the air­ craft to a quiet hissing noise as the tank pressure blows off.

So, in the euphoria of a flight in the Pup, what have we forgotten? We didn't check the tank pressure once in flight, nor did we look at the oil pulsator. Of the latter, we were in no doubt that oil was flowing as a constant stream of castor oil fumes continuously invaded the cockpit. As to the former, if air pressure had fallen in flight, the engine would have died through lack of fuel. Should this have happened, a check of the air pressure gauge would have confirmed the problem and a few pumps on the cockpit handpump would have rectified it-we make a mental note to bring the pressure gauge and the pulsator into the cockpit scan on the next flight.

I've now flown several sorties in the Pup and what a marvellous machine she is. The handling qualities are superb for a machine of her era… but there are enough interesting characteristics to require a certain amount of piloting skill to achieve safe flight.It's no wonder the Scout pilots of the RFC and RNAS held the machine in high regard. As for me, well, the vision still hasn't burst!
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#120 1PL-Husar

1PL-Husar
  • Posts: 558

Posted 26 December 2014 - 23:52

Thank You piecost. Amazing and detailed read. I wish i had this book.
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