Fokker D.VIIF?

[BMA_Hellbender]

41 minutes ago, hrafnkolbrandr said:

Is our Camel running a Bentley or is it supposed to be the Clerget 9b?  I'm still trying to figure out why it is so fast.

 

It's not a Bentley or Clerget 9Bf Camel, but a top of the line Clerget 9B. It's identical to the pre-2014 patch (pre-1.034) Rise of Flight Camel.

 

Originally posted by @AnPetrovich:

 

 

 

Quote

Very interested to see how much of a bump the BMW provides.  Sea level in RoF it pulls a little over 200 at sea level using altitude throttle IIRC.  When they put it in this sim I expect we'll see about 207-208 bearing in mind the small bump everything here (minus the pfalz) got.

 

Going by RoF store figures, the Fokker D.VIIF has a top speed of 194km/h compared to 190km/h on the D.VII. Both will (probably) end up being 4km/h faster in FC, 194km/h on the D.VII we already know — so I would expect 198km/h on the Fokker D.VIIF. This makes it marginally faster than the Camel at sea level, where it honestly shouldn't be fighting it, and more than likely considerably faster at 3000m, in the neighbourhood of 30km/h.

 

EDIT: With altitude throttle fully engaged I can reach 204km/h at sea level in the RoF D.VIIF, so we might indeed get around 208km/h at sea level in FC (with altitude throttle fully engaged, actively damaging the engine).

 

https://riseofflight.com/store/aircraft/fokker-dvii/

 

https://riseofflight.com/store/aircraft/fokker-dviif/

 

 

The Pfalz actually got a small 3km/h bump to 171km/h, as it's original pre-patch figure is 168km/h.

 

https://riseofflight.com/store/aircraft/pfalz-diiia/

 

 

The Dolphin, likewise, got a 3km/h bump from 200km/h to 203km/h.

 

https://riseofflight.com/store/aircraft/sopwith-dolphin/

 

 

 

Only two planes have lost speed (so far) compared to pre-patch RoF.

 

The SPAD lost 1km/h at sea level: 219km/h down from 220km/h.

 

https://riseofflight.com/store/aircraft/spad-13c1/

 

And the biggest loser is the Fokker Dr.I, which retains its "undocumented" post-patch speed of 165km/h, compared to the RoF store figure of 178km/h. That's a whopping 13km/h.

 

https://riseofflight.com/store/aircraft/fokker-dri/

 

I believe this was done, not out of oversight, but to reflect that it has 20 less horsepower than the Camel. However, as has been pointed out, the Oberursel Ur.II actually generates closer to 120hp. Hopefully the latter will be fixed soon.

Edited March 16, 2019 by Hellbender

[SeaW0lf]

2 hours ago, Hellbender said:

The SPAD lost 1km/h at sea level: 219km/h down from 220km/h.

 

The store is wrong. Ingame it gets to more or less 214km/h (HUD) at ROF, so it gains the same 2% (ish) that every plane is gaining here. Especially because they apparently would have to tweak it to change the speed, since every plane is behaving the same, and they already said that they are not doing it.

Edited March 16, 2019 by SeaW0lf

[Zooropa_Fly]

I think it would be easiest if they just gave us the fastest version of everything, let's face it that's pretty much what most seem to want.

[SYN_Vander]

38 minutes ago, Zooropa_Fly said:

I think it would be easiest if they just gave us the fastest version of everything, let's face it that's pretty much what most seem to want.

 

Maybe better to have two engine versions for most of these planes, with the second one being the fastest. This gives a lot of possibilities in (multiplayer) mission design, assuming you can lock the loadout options. The fm discussions would then be mainly focused on the missions made/server settings and not aimed at the developers.

 

I like the way this has already been done for planes like the La-5, the Spitfire etc.

Edited March 16, 2019 by SYN_Vander

[ZachariasX]

58 minutes ago, Zooropa_Fly said:

I think it would be easiest if they just gave us the fastest version of everything, let's face it that's pretty much what most seem to want. 

 

Yeah, baby!!!!

 

 

 

 

[Panzerlang]

Oh, is there a slower version of the Camel? Who knew!

[BMA_Hellbender]

Yeah, I don't think we need the Bentley Camel right now, unless Central gets the Siemens-Schuckert D.IV (and then some).

 

Some Camels were fitted with a 110hp Le Rhone 9Ja when British license-built Clergets were failing at the beginning of the production run. This would be more or less the Camel currently present in RoF, comparable to the 110hp Fokker Dr.I in both RoF and FC (though the real Fokker Dr.I was a 120hp machine with a top speed some 10-15km/h higher than what we currently have).

 

I'm still not entirely okay with a 130hp Clerget 9B Camel reaching 195km/h at sea level. It's clearly excessive when we look at the Camel chart above. Official top speed was around 185-190km/h, greatly dependent on how well the engine was serviced. Obviously 5km/h (<3% of its top speed) is not much to worry about, but it adds up to an already unfair match.

[migmadmarine]

In case it has been overlooked, Jason confirmed that the D.VIIF will be introduced as a separate aircraft. 

[BMA_Hellbender]

28 minutes ago, thenorm said:

In case it has been overlooked, Jason confirmed that the D.VIIF will be introduced as a separate aircraft. 

 

And is she looking great already!

 

[EAF19_Marsh]

Out of vague interest, should not the drag of the DR.1 negate the competitive nature of the engine vs. the Camel? I do not recall anyone claiming that the Dr. 1 was a 'quick' aircraft, while the term used to describe its excellent climb (Yeats - 'like a lift') suggests high angle, low speed).

 

The DVII looks really lovely, though have yet to fly it.

[HagarTheHorrible]

46 minutes ago, EAF19_Marsh said:

Out of vague interest, should not the drag of the DR.1 negate the competitive nature of the engine vs. the Camel? I do not recall anyone claiming that the Dr. 1 was a 'quick' aircraft, while the term used to describe its excellent climb (Yeats - 'like a lift') suggests high angle, low speed).

 

The DVII looks really lovely, though have yet to fly it.

 

 Not sure exactly what you're driving at.  I think a significant difference, propulsion wise, between the DR1 and Camel would have been the pitching of the propeller.  The Dr 1 would have been pitched more for low speed grab and thus climb while the Camel would have possibly had a more balanced , general flight, pitched propeller for all round performance. 

[EAF19_Marsh]

3 wings plus struts are higher form drag was my point. A quick glance at the 2 suggests that the Dr.1 is draggier.

[ZachariasX]

The Camel has 2.55 meter pitch, the Dr.I prop has 2.3 meters. At equal rpm the Camel is ~10% faster.

[Cynic_Al]

1 hour ago, ZachariasX said:

The Camel has 2.55 meter pitch, the Dr.I prop has 2.3 meters. At equal rpm the Camel is ~10% faster.

 

Thanks for enlightening us regarding the extent of your relevant knowledge.

[AndyJWest]

2 hours ago, ZachariasX said:

The Camel has 2.55 meter pitch, the Dr.I prop has 2.3 meters. At equal rpm the Camel is ~10% faster.

 

Fokker clearly missed an opportunity there. If they'd fitted the Dr.1 with a 5.1 metre pitch propeller, it would have been twice as fast as the Camel. 

[BMA_Hellbender]

3 hours ago, EAF19_Marsh said:

3 wings plus struts are higher form drag was my point. A quick glance at the 2 suggests that the Dr.1 is draggier.

 

The Dr.I is an innovative machine in spite of its three wings (very much a political decision). It has internal bracing wires and the outward struts only serve to counter flexing, as the wings are cantilever and more or less of the same thick design as the Fokker D.VII. In that respect, it actually has comparatively small parasite drag.

 

In fact, the plane which Fokker wanted to design would have brought the Dr.I and D.VII together, benefitting from both the superb performance of a rotary engine and the superior efficiency of a biplane. That plane would be known as the Fokker D.VI, and it saw limited service, mostly due to rotary engine problems and shortages.

 

https://en.wikipedia.org/wiki/Fokker_D.VI

[EAF19_Marsh]

Wiki says I am wrong, which surprises me. Camel appears to have a worse drag co-efficient. Hmm.

[Cynic_Al]

17 minutes ago, EAF19_Marsh said:

Wiki says I am wrong, which surprises me. Camel appears to have a worse drag co-efficient. Hmm.

 

That doesn't necessarily dictate that it generated more drag.

[EAF19_Marsh]

1 minute ago, Cynic_Al said:

 

That doesn't necessarily dictate that it generated more drag.

 

No, quite. I merely used this as a quick check. Obviously it is a complex subject but I am surprised that the sheer flat plate area of 3 planes and associated impact on flow might offset 2 planes, albeit with external bracing. Especially give that the 2 have otherwise extremly similar general configuration from a fuselage perspective (like most rotaries).

[ZachariasX]

25 minutes ago, AndyJWest said:

Fokker clearly missed an opportunity there. If they'd fitted the Dr.1 with a 5.1 metre pitch propeller, it would have been twice as fast as the Camel. 

Only if he used imperial grade snake oil for lubrication of the engines.

 

2.55 meters pitch is still flat enough for the engine to reach rated rpm. A fixed pitch prop driven plane is rather exactly as fast as it managed to crank the propeller. By starting a climb, the finer pitched prop will hold rpm longer. 2.55 meters is hardly the maximum pitch you could put on there, as it would mean that there is hardly any flight situation whatsoever, where the propeller can operate at maximum efficiency. Thus consider the 2.55 meters being already a compromise.

 

In fixie bicycles, the gearing is very much shorter than what you could have for maximum speed in the plain. The shorter your gearing is, the slower your top speed will be, but the more margin you have for the climb. It will depend on the mix of climb and straights which gearing is the most efficient.

 

As drag increases exponentially, there is typically little real word use to be gained from the last couple of % pitch possible.

 

But when you see a ~10% real world speed differential in aircraft and that they, being similar in dimension and engine, differentiate such that the somewhat 10% faster aircraft has a 10% more coarse pitched prop, then you have the answer to whether one is draggier than the other:

 

5 hours ago, EAF19_Marsh said:

Out of vague interest, should not the drag of the DR.1 negate the competitive nature of the engine vs. the Camel?

Answer then: No. Same drag in both aircraft for practical purposes.

 

Now further question, why would Anthony chose 2.3 meters pitch and Thomas a 2.55 meter pitch?

 

Answer probably this: The Entente had fast aircraft, faster than the German aircraft, and they had a lot of them. If it came to hunt down aircraft, they had what it took already. When you're designing a dogfighter for that same team, it is fine if your aircraft is slower than both the SPAD and the SE5a. You just make it fast enough to really get cornered that easy by the other teams fighters. This means, you should at least try to make it somewhat equal in speed than most enemy aircraft. 2.55 m pitch on the Camel did just that. The Camel was somewhat on par with the Albatri in speed, it just couldn't dive with them. The Dr.I was

 

Fokker had a much different situation. The Entents inline engine fighters were so much faster than whatever he could squeeze out of the rotary powered plane that beating them at speed was impossible. But by making the aircraft light (it carries only half the fuel of the Camel) and by deliberately making it a tad slower, he could let it beat the Entente aircraft in climb. hence 2.3 meters.

 

58 minutes ago, Hellbender said:

In fact, the plane which Fokker wanted to design would have brought the Dr.I and D.VII together, benefitting from both the superb performance of a rotary engine and the superior efficiency of a biplane. That plane would be known as the Fokker D.VI, and it saw limited service, mostly due to rotary engine problems and shortages.

If we take Anthonys word here, he didn't care at all about that sweet plane. And he though very little of the "superb" roraty engine.  It was all just a stop gap possibility as the Dr.I quiet clearly needed to replaced with something in 1918 and at some point the triplane craze wore off. But he wanted inline engines and he wanted them in the D.VII. It took him a year of scheming and fighting to get them  finally. As it was not clear at all (to im at least) that he would be issued orders of inline engines reliable and large enough to bet his main production on, he desperately was trialling various designs to accept any kind of powerplant. Finally, idFlieg accepted his D.VII design and he got the engines for them, and he would just take any version they gave him, from the "weak" one we have in "our" current D.VII to the overcompressed variants later on.

 

Anthony openly stated that he was happy with the D.VII and didn't consider improving it anymore as it supposedly was perfect enough and he wouldn't waste money in further designs.

 

Fokker only bought the Oberursel Motorenfabrik because it was the only engine factory available to him. He wanted inline Mercedes Engines, but they thought he stinks and wouldn't deliver (reliably) to him. This put him in a terrible position. He could have made a lot of money through contract manufacturing airframes (as he did in large volumes). The huge downside of this from a business perspective (all he cared about) is that once you become a contract manufacturer for airframes, you lose the capability to invent new aircraft. This becomes deadly at the moment where huge aircraft orders stop. Read that as "Monday after the war". In order to stay competitive and in the game in the long run, he absolutely needed to be able make whole aircraft to specification. For this, he needed the engine factory, even though it was third choice behind Mercedes and BMW.

 

Often, even today, when a country buys military aircraft, apart from the usual briberies is often a clause in the contract that anything between "end manufacturing" and "license manufacturing" is being done in the buysers country. While politicians love that as they can (falsely) claim that they get a better deal by "spending in your own country", it actually both increases the cost for the aircraft plus it puts the manufacturing company in the same spot as Fokker then. Although it is a bit of free money for company wellfare, companies don't really like this kind of business, as they have to assign massive capital to a venture that can end rather quickly. If you wanted to do them a favor, you should let them build their own plane.

 

 

 

[AndyJWest]

33 minutes ago, ZachariasX said:

2.55 meters pitch is still flat enough for the engine to reach rated rpm. A fixed pitch prop driven plane is rather exactly as fast as it managed to crank the propeller...

 

Too wrong to be worth arguing with, in too many ways. I saw enough of this nonsense on the old RoF forum, and I'm not going to go through it again. You cannot calculate the speed of an aircraft from prop pitch and RPM. Simple fact. If you want to believe otherwise fine, but don't expect anyone to take you seriously.

Edited March 17, 2019 by AndyJWest

[ZachariasX]

2 minutes ago, AndyJWest said:

Too wrong to be worth arguing with, in too many ways. I saw enough of this nonsense on the old RoF forum, and I'm not going to go through it again. You cannot calculate the speed of an aircraft from prop pitch and engine RPM. Simple fact. If you want to believe otherwise fine, but don't expect anyone to take you seriously. 

So far, it gave surprisingly exact numbers for flight speed in aircraft.

 

Any source to enlighten me on how much I was wrong?

[AndyJWest]

3 minutes ago, ZachariasX said:

So far, it gave surprisingly exact numbers for flight speed in aircraft.

 

Any source to enlighten me on how much I was wrong?

 

It is you that is making the claim. The burden of proof is on you to support it. Find a book on aerodynamics (or a similar credible source) which does so.  Cite it.

 

Good luck with that...

Edited March 17, 2019 by AndyJWest

[EAF19_Marsh]

Not that this is a crucial element, Z, but your points about license manufacture are also inaccurate.

 

Edit: for modern programmes - this may have been true for Folker.

Edited March 17, 2019 by EAF19_Marsh

[SeaW0lf]

Chill will probably solve many of these problems when he starts flying with the Le Rhône and Clerget engines - perhaps end of the year as he says. He will certainly be flying at cruise speed or something around those numbers, but it will nonetheless give us a pretty good indicative of how they performed, and he said the first ones will be the 110 Le Rhône and the 130 Clerget. In other words, we could not have imagined it better.

[BMA_Hellbender]

 

Quote

If we take Anthonys word here, he didn't care at all about that sweet plane. And he though very little of the "superb" roraty engine.  It was all just a stop gap possibility as the Dr.I quiet clearly needed to replaced with something in 1918 and at some point the triplane craze wore off. But he wanted inline engines and he wanted them in the D.VII. It took him a year of scheming and fighting to get them  finally.

 

Anthony openly stated that he was happy with the D.VII and didn't consider improving it anymore as it supposedly was perfect enough and he wouldn't waste money in further designs.

 

Fokker only bought the Oberursel Motorenfabrik because it was the only engine factory available to him. He wanted inline Mercedes Engines, but they thought he stinks and wouldn't deliver (reliably) to him.

 

Fokker had always been partial to rotary engines and their excellent power-to-weight and compression ratio making them superb high altitude engines (remember that the humble 80hp Sopwith Pup outperformed the 180hp Albatros D.III at 4000m), as would anyone who designs light planes with clean lines and thick wings. Further proof can be found with the Fokker E.V/D.VIII monoplane.

 

Obviously both the Fokker D.VI and D.VIII had been designed with the Oberursel UR.III in mind, set to replace the obsolescent UR.II — but even with said outdated engine which suffered greatly from the use of Ersatz oil, these machines performed admirably.

 

Idflieg did favour the Mercedes inline engines because of their power and reliability — thus made sure most of them went to actual German manufacturers, rather than a Dutch immigrant. We can see a similar kind of nepotism with the British who favoured the state-run Royal Aircraft Factory over Sopwith and the French who favoured Béchereau/SPAD over Delage/Nieuport and provided them with their best (read: mostly highly rated inline) engines.

 

Still, of the three most advanced (high altitude) fighters to see service in WWI, two were rotaries: the Sopwith Snipe with its massive Bentley BR.II, the Siemens-Schuckert D.IV with its counter-rotary Sh.III, and finally the inline Fokker D.VIIF thanks to the high octane / high altitude carburettor in its BMW IIIa. The only reason rotaries were eventually discontinued was because of the physical limits of a spinning engine block and the development of static radial engines.

Edited March 17, 2019 by Hellbender

[1PL-Husar-1Esk]

Btw i read (think it was in Open cockpit by Arthur Gould Lee) about Pups vs Albatri  as you say at that  specific thigh altitude Pups were superior. Never checked it in ROF , is this portrayed in ROF?

[ZachariasX]

17 hours ago, AndyJWest said:

The burden of proof is on you to support it. Find a book on aerodynamics (or a similar credible source) which does so.  Cite it.

 

I guess I expressed myself rather poorly. What I brought up with my rule of the thumb, is a quick way to make an educated guess on the cruise speed of an aircraft. When comparing two aircraft of similar dimension, fitted with a similar engine and running that at similar rpm, it allows you to get an idea of the flight speed you're about to get at different prop pitch.

 

That this is not just made up, can be read here, it is described a bit more in detail and also reflecting prop efficiency, something I didn't mention as I assumed similar efficiencies of the two props (Camel/Dr.I) and I was just interested in potential speed differentials.

 

Also, to make this come true, there are a lot of assumptions made already, meaning the prop is in all cases properly dimensioned for the engine and aircraft.

 

Here, for your convenience:

http://zoomaviation.com/programs/prop_angle/index.php?dia=75&amp;pitch=57&amp;action=C-172

 

It is very basic knowldge, nothing fancy. With this I'm citing basically all books in aerodynamics on that matter. I chose this as source as I consider it informative and simple.

 

And when using that principle with real world aircraft, you get surprisingly good predictions on flight speed. And that's what this is about, making a prediction. I didn't explain the prop aerodynamically at all. It is just a model to make a prediction. Same as when you use the formula s=1/2at^2 to compute the distance an object falls out of your window over time, it doesn't explain gravity. It just gives (under the assumption you live in a Newtonian world) a good prediction of the falling distance over time. No more.

 

17 hours ago, EAF19_Marsh said:

Edit: for modern programmes - this may have been true for Folker. 

Imagine Boeing being told to license manufacture the A320neo. Or the Gripen (America finally getting a new jet fighter in numbers.). Even Pilatus in Switzerland is not fond of manufacturing any potential new fighter jet, even though they surely will do it.

 

But I do agree that business decisions very much depend on the actual situation of the company.

 

[EAF19_Marsh]

50 minutes ago, 307_Tomcat said:

Btw i read (think it was in Open cockpit by Arthur Gould Lee) about Pups vs Albatri  as you say at that  specific thigh altitude Pups were superior. Never checked it in ROF , is this portrayed in ROF?

 

Great book. Never really checked, but the Pup remained very flyable and nimble up high. Lee was - I think - not the only one to remark on this,

Quote

Imagine Boeing being told to license manufacture the A320neo. Or the Gripen (America finally getting a new jet fighter in numbers.). Even Pilatus in Switzerland is not fond of manufacturing any potential new fighter jet, even though they surely will do it.

 

Thing is, Boeing is unlikely to license-produce a military a/c as part of their rationale is development. Now, smaller companies that want to avoid the NRC of a major project - and particularly that have gov't support - might well be sensibly attracted to a license production not only as means of reducing necessity of internal IP generation but also because it is one step on a learning curve from 'make small bits' to 'make own designs'.

 

So, though the licenser will no doubt charge the liscensee a premium on this, the larger / wider 'offset' in general rather than specific terms) can be a great boon for a single company but more liekly for a whole domestic supply chain as the revenue tends to stay more within the country and is recycled to a degree in the inevitable payment / tax system. This might prove more immediately expensive than buying off the shelf, but the economic impact analysis (ignoring the political cache) is quite difficult to measure and varies by example in both short and long-term.. Even a domestically-produced version also benefits from access to an existing support network.

 

If the US chose Gripen - by the way- it would be made by Boeing (but t'ain't gonna happen). If Canada chose it, that is a more interesting industrial balancing act.

 

[BMA_Hellbender]

1 hour ago, 307_Tomcat said:

Btw i read (think it was in Open cockpit by Arthur Gould Lee) about Pups vs Albatri  as you say at that  specific thigh altitude Pups were superior. Never checked it in ROF , is this portrayed in ROF?

 

The Pup in RoF is a strange animal (pun intended). Before 1.034 (the infamous 2014 patch) it was a fast little dragster clocking in at around 180km/h at sea level (official store figure 176km/h). This may seem like a bit of a stretch considering its 80hp Le Rhone 9C, however this is an accepted figure in historical documentation. It's also around 10km/h faster than its French counterpart, the Nieuport 11 (official store figure 167km/h), which has the same engine, similar weight, a somewhat cleaner sesquiplane design, but also an overwing Lewis machinegun causing extra drag. The Nieuport 11 is in turn, marginally faster than the 110hp Nieuport 17 (official store figure 165km/h) — an even cleaner, though slightly heavier design — almost inexplicably so.

 

...which has led me to believe that there are quite a few errors in both historically published data and data interpretation in RoF.

 

I will list them all:

 

• The Pup operated with two different engines, the standard 80hp Le Rhone and a 100hp Gnome Monosoupape, the latter in RNAS service for shipborn use, and where the rather high performance figure of 180km/h may have come from. The Aerodrome actually lists the Sopwith Pup's top speed as a far more realistic 161km/h — which is nowadays also reflected in RoF since the 1.034 update. As such, I consider the Sopwith Pup as it exists today in RoF to be very close to the one which saw service during Bloody April, pitched against a 175-180km/h Albatros D.III. It would not have been a match for either its speed or twin guns at sea level and needed to climb to great altitude to make full use of its light weight, maneuverability and superior rotary engine compression ratio.
   
• The Nieuport 11 is also a strange affair, as the actual 11 designation may have been a misnomer. In fact, the term Nieuport Bébé may have been used interchangeably for both the 80hp Nieuport 11 and the 110hp Nieuport 16 (a Bébé with a Nieuport 17 engine). Here the Aerodrome lists its the Nieuport 11's top speed as 156km/h, far more in line with the power output of its 80hp engine. The Nieuport 11 present in RoF is simply put a Nieuport 16. The Aerodrome once again confirms this as its top speed is 165km/h.
   
• Finally the Nieuport 17 in RoF is about 10km/h too slow. Owing to the improvements in aerodynamic design over the Nieuport 11/16, it should be faster. Again confirmed by The Aerodrome as 177km/h. This would bring its performance very close to that of Chill's 110hp Fokker Dr.I, which has a similar top speed of 175km/h.

 

In conclusion:

 

RoF Sopwith Pup (pre 1.034) = real world Gnome Monosoupape 100hp Sopwith Pup

RoF Sopwith Pup (post 1.034) = real world Le Rhone 9C 80hp Sopwith Pup

RoF Nieuport 11 = real world Nieuport 16

Rof Nieuport 17 = 10km/h too slow

Edited March 18, 2019 by Hellbender

[AndyJWest]

1 hour ago, ZachariasX said:

 

I guess I expressed myself rather poorly. What I brought up with my rule of the thumb, is a quick way to make an educated guess on the cruise speed of an aircraft. When comparing two aircraft of similar dimension, fitted with a similar engine and running that at similar rpm, it allows you to get an idea of the flight speed you're about to get at different prop pitch...

 

So, your assertion that you could determine the speed of an aircraft via the prop pitch and RPM "rather exactly" turns out instead to be nothing but handwaving approximation based on all sorts of assumptions about comparing similar aircraft. Rather pointless, when the object of the exercise is to compare aircraft which aren't similar, and where the debate concerns factors which may lead to differing performance.

 

As for the source you cite, it isn't a book on aerodynamics. It is a webpage by an anonymous person, again resorting to rules of thumb in order to arrive at approximations regarding appropriate prop pitch for a very narrow range of aircraft. A source which introduces entirely unnecessary waffle about 'slip' (which whatever it is, isn't the same thing as propeller efficiency) , while entirely to either adequately explain how a propeller works, nor to discuss the multiple factors which affect both its efficiency and the manner by which appropriate propeller pitch  can be arrived at. And then you have the nerve to claim that you are  'citing basically all books in aerodynamics on that matter'. No you aren't. that isn't what 'citation' means. Look it up in a dictionary.

 

If you want to understand how a propeller actually works, you could make a start by reading pages 87 to 112 of 'Fly Better ... the things you should have been taught when learning to fly!' by Noel Kruse. This excellent publication is available for free download. You want part one, though the other three parts are interesting reading too. http://www.flybetter.com.au/

 

I suggest that when reading this, you pay particular attention to the discussion concerning the difference between geometrical pitch (incidentally, something which different propeller manufacturers have historically been  shown to define differently, making it a poor means of arriving at any conclusions) and the most efficient angle of attack. And then take note of what is clearly the most significant matter when discussing actual propeller performance: induced airflow. As Kruse makes clear, you simple cannot adequately explain propeller performance without understanding that when producing any thrust at all, the velocity of the air through it must of necessity be higher than that of the free air around it. This is, as Kruse again notes, the only explanation of why a propeller on a stationary aircraft can produce any thrust at all. And as Kruse clearly states, induced airflow is a significant factor at any airspeed: "the induced airflow velocity at full power is equal to about 30% of the slipstream velocity" (p. 96) I would hope that after reading this, you will stop applying the simplistic 'screwing through the air' model that Kruse notes tended to be used by early (unsuccessful) aviation experimenters, and instead start from the assumptions that the Wright Brothers did: that a propeller is best understood as a wing generating lift through its motion through the air. And then take into account all the actual factors that matter in assessing propeller performance, rather than claiming that rules of thumb on random websites somehow constitute current understanding of a very complex subject.  They don't. Rules of thumb (and approximations based on 'similar aircraft') may put you somewhere in the ballpark, but they clearly cannot be used to arrive at actual performance figures. They can't now (and don't need to be, since we have better methods to design propellers), and weren't able to do so back in WW1, when aircraft manufacturers knew enough at least to test their assumptions against verifiable results, and revise their designs accordingly.
 

 

Edited March 18, 2019 by AndyJWest

[ZachariasX]

5 minutes ago, AndyJWest said:

This excellent publication is available for free download. You want part one, though the other three parts are interesting reading too. http://www.flybetter.com.au/

That is one nice book. Thank you for posting the link!

 

And I appreciate you taking the time making your point clear and it seems that in principle we are very much in agreement. I must admit that initially I very much frowned upon this "rule of the thumb, then I was amazed How quickly I got to remarkably correct ballpart guesses *if certain circumstances were met*. One being the the aircraft in question must be *slow* aircraft. Then again, most GA are. That is why I use them occasionally as a first gauge.

 

But let's not drag that out further but return to our nice FC aircraft!

 

[BMA_Hellbender]

27 minutes ago, AndyJWest said:

They don't. Rules of thumb (and approximations based on 'similar aircraft') may put you somewhere in the ballpark, but they clearly cannot be used to arrive at actual performance figures. They can't now (and don't need to be, since we have better methods to design propellers), and weren't able to do so back in WW1, when aircraft manufacturers knew enough at least to test their assumptions against verifiable results, and revise their designs accordingly.

 

I agree. That said, it shouldn't keep us from making sanity checks when comparing 100-year-old test data.

 

To return to the example of the Sopwith Pup which I mentioned above: while it's not entirely impossible for a 80hp machine to reach 180km/h (especially if climb and acceleration are thrown out the window and a fixed propeller pitch is chosen solely for top cruise speed), it's better to lump all the 80hp machines together at first, then start making clear distinctions in terms of wing surface area, drag coefficient and weight, then compare to actual published data.

 

Then find out there is actually conflicting data.

 

Then somehow get the developers interested in applying corrections.

 

Then finally give up and just wait for the two-seaters to arrive so we can have ourselves a good old flaming scout buffet.

 

 

Sorry, got a bit carried away there. ?

Edited March 18, 2019 by Hellbender

[AndyJWest]

44 minutes ago, Hellbender said:

 

I agree. That said, it shouldn't keep us from making sanity checks when comparing 100-year-old test data.

...

 

 

Sanity checks are always good. Just as long as people don't confuse 'not being insane' with 'being entirely accurate'. Which seems to be the issue here. That and a great deal of circular reasoning (where the data you use to arrive at a conclusion is somehow validated by the conclusion you reached with it). Propeller pitch (however defined) and engine RPM are clearly relevant to aircraft performance. But so are other things. Lots of them. Including a great many things we'll probably never know, given the spotty historical record regarding aircraft built during a time when what really mattered was getting them out onto the front line airfields rather than making exact performance measurements with equipment not really suited to do so. The most useful rules of thumb in this regard are that applied by any competent historian: to look at sources in context, to avoid reading into them things they don't actually say, and to avoid giving undue weight to specific sources just because they support a conclusion you've already arrived at. Acknowledge the contradictions. And the inadequacies of data. Do that, and you'll understand why endless debates over exact performance figures for Sopwith Camels and Fokker Dr.1s are an obsession of air combat simmers, rather than historians. The only correct answer to 'How fast was a WW1 Sopwith Pup with a 80HP Clerget' or whatever is 'roundabout so-and-so' depending on who you cite, and on half-a-dozen factors you know about, along with lots more you almost certainly don't.

Edited March 18, 2019 by AndyJWest

[EAF19_Marsh]

29 minutes ago, AndyJWest said:

Just as long as people don't confuse 'not being insane' with 'being entirely accurate'.

 

Which is as true of people as it is of physics.

[ZachariasX]

3 hours ago, AndyJWest said:

Sanity checks are always good. Just as long as people don't confuse 'not being insane' with 'being entirely accurate'. Which seems to be the issue here.

 

It is indeed everything about sanity checks. It is all about having a quick and simple way to get an idea what you can expect. That often this sany check produces surprisingly exact values should by no means get in the way of knowing that you're just gauging your expectation.

 

That sanity check itself is taken from something that is a very, very, very [...] commom "general knowledge" about propellers. While from the point of sheer aerodynamics, it is as much garbage as "low pressure over the wing the creates lift", both being wisdoms that cannot be disposed anymore, it is with us. But at least unlike the incorrect lift theories, the first one can be made of some use, when knowing what you are doing.

 

It is very inefficient to tackle any problem "at the root" (in case of propeller difficult to the point that we wouldn't even start doing it) before you have an idea what to expect and this

4 hours ago, AndyJWest said:

but they clearly cannot be used to arrive at actual performance figures.

was never the point of it. It's just nice when it fits your measurements. no more, no less.

 

Now that it is in principle not very aerodynamical of a solution to guess your flight speed can be seen where it is actually mostly used, and these are ships. There the "slip" is a more clearly defined metric to define the efficiency of your boats performance.

 

You're probably right that the first aircraft propellers were made acording to that wisdom, until they learned a bit more about the issue. And hence it is everywhere basic knowledge. That principle is of course poor knowledge to design a propeller. But once you have good propellers installed, you can use if for a guess what they do.

 

[AndyJWest]

24 minutes ago, ZachariasX said:

 

...surprisingly exact values...

 

The only surprising thing here is that after reading what I have written, you are still working under the assumption that I believe it is possible to arrive at 'exact values' regarding aircraft that flew 100 years ago. I don't, as I have made absolutely clear. And neither will anyone who actually understands what the problems are.

 

If you want to multiple your shoe size by Pi, and add in the number of hours since the assassination of President Lincoln, you will arrive at a very exact figure (as exact as you want it to be, given only the limitations in accuracy of your calculator) It will be exact. It will be 'accurate'. It will however have no relation to anything in the real world. 'Exactness' is only meaningful in relation to whatever it is that is being measured. And if you can't measure it accurately any other way, no possible means to determine 'exactness' exists.

 

And with that, I'm done with this conversation. I should probably never have got involved, since it seems to be nothing but a repetition of the sort of nonsense that made the RoF forum such a time-waster.

[ZachariasX]

4 minutes ago, AndyJWest said:

'exact values'

Not excact. But close to that. Surprisingly close. ("How can that be?") And no, I don't assume you believe something or anything for that matter. I just don't want to be misrepresented like that.

 

But anyway, I still appreciate that you did. And thanks for posting the book. And yes, lets leave it at this. There's an update out. Happy flights.

[EAF19_Marsh]

The D. VII is a lovely piece of kit, but I wish the AI would not squander the VII’s advantages. Ace AI is dangerous head-on owing to its uncanny shooting, but after that everything seems to be dog-meat.

 

Oh well, maybe a future fix.

[=IRFC=Gecko]

A couple of questions,

 

I noticed that a rendering of the D.IIIau was on the first page. I cannot find in any of the photographs I have access to or on any of the Wingnut Wings kits or TVAL images where the D.IIIau has the little cylinder above the above the prop shaft and in front of cylinder number 1. Furthermore if you go to the Wingnut Wings website you can access the instruction sheets for all the models and these instructions also include colour and black and white WWI photographs of the engines of most of the kits they produce.

 

I was wondering about how many D.VII F's were actually available for combat during WWI. All my research indicates that the number was extremely small. J2 or 5 fully equipped?

Jagdgeschwader Nr II only had six in Bertholds command squadron out of it's 12 aircraft. J12, J13, J15 and J19 had none in JGII.

I have found only reference to BMW building at most 540 engines before the end of the war. Post war production bought this number to over 1000 and the 540 number was a production best estimate by BMW by November 1918. They could have possibly built more but I find that unlikely due to the disruption of raw materials and the state of Germany near the end of the war.

 

At least 30 engines appear to be set aside for testing on various airframes going by the aircraft being tested and allowing for spares in case of prop strikes/damage (which required an immediate engine overhaul/repairs). A further number, around 80 or more, were reportedly sent to Pfalz for the construction of Pfalz D XII's. Yes I know Fokker said in his book that those engines were stripped and put into Fokker D.VII airframes but he was well known for shall we say ...... exaggerating. Additionally as a pilot of a Pfalz D.XII would you willingly hand over your BMW for a D.IIIau or worse depending on what was available. I know no Squadron Commander who would have willingly hobble his aircraft without direct orders from above - of which I can't find any reference to anywhere though that isn't a surprise considering all the records lost.

Wingnut Wings is of the belief few if any Pfalz D.XII's were actually fitted with BMW engines in the Jastas and only Pfalz D.XII 1387/18 was actually equipped with the BMW and tested in the 2nd fighter competition during mid 1918 (WnW only know of one photo of a BMW equipped D.XII but I don't know the serial number). 

 

Additionally I was reading a French report on a captured Fokker D.VII and this aircraft was equipped with a stock D.III engine (160hp). Wingnut Wings also have photographs of a Fokker D.VII which appears to be equipped with a stock D.III engine. How many were actually flown like this - who knows. Either way it goes it appears that desperate shortages of materials resulted in old engines being placed in new airframes but documentation of this doesn't exist outside photographic evidence and it is possible that this is the same few airframes being referenced by multiple sources in multiple instances.

 

So give me your guess on how many D.VII F's were produced and the most active on the front at any one time allowing for spare parts (engine) maintenance and production numbers. If you have better info on BMW engine production please do share.

I'd be interested to see what everyone thinks.

 

Regards Shot

 

PS: As for using Wingnut Wings (a model company) as a reference - it is owned by the same owner of 'The Vintage Aviator Limited' and has access to all research materials gathered by both when researching WWI aircraft. Knowing this I'm pretty sure the research is both thorough and accurate.