109G2 performance is low

[madrebel]

Did some offline testing to confirm after someone mentioned the G2 is slower than the F4 even after dropping the bomb.

http://kurfurst.org/Performance_tests/109G1-6_datasheet/109G_perftable_EN.html

Here we see two clean 109G2s flying in the 405mph range. Do note, the first G2 isn't clean as it has 2 x MG151 gondolas and a tested speed of 636KPH. A few lines lower we see a clean armed G2 with a camera installed reaching 652kph/405mph. Gondolas are reported to have a speed penalty in the 12-16kph range. here we see this tested and it is a 16kph difference.

For the F4, 635kph/394mph seems to be the general consensus for performance using the 30m power rating of 1.3aTa at 2500rpm. Clearance for the 1.42@2700rpm came later and brought the F4 right up to the 400mph mark, but we don't have that one and it should be noted the G2 was also eventually cleared for 1.42aTa@2800rpm too - neither is important to this discussion though.

Comparing the two directly leaves very little in terms of differences. As I recall, 125KG weight difference the vast majority of which was engine/oil weight. You might think, well, heavier plane will climb worse etc etc ... but you need to account for the improved VDM prop, the 100rpm difference between motors, and that 125KG added to ~3100kg is less than 10% increase in weight that will be significantly offset by an increase in thrust efficiency via the new prop as well as 100 additional revolutions of the prop. Lastly, the armored windscreen was moved from being an external addition to the wind screen to being an internal/integral redesign of the hood and this absolutely cleaned up the drag a bit. remember too that G2s were part of the later high speed dive tests conducted by the Germans. G2s hit .805 mach in those tests and well over 500mph.

the 109G2 was aerodynamically cleaner, flew faster, had better climb, and superior acceleration than the F4, full stop. it wasn't massive but it was better.

if you want a bomb laden 109 in tier2 that is NOT faster than the F4 you could have easily done this by adding a bomb to the F4 or adding a bomb to the F2. either of those are valid options. having a broken G2 is great and all but it isn't correct.

*edit* there was a radio upgrade as well as a radio antennae change as well from the F4 to the G2.

Edited August 12, 2021 by madrebel

[delems]

*** and that 125KG added to ~3100kg is less than 1% increase in weight

Actually, 125/3100 is more like 4%.

[madrebel]

15 minutes ago, delems said:

*** and that 125KG added to ~3100kg is less than 1% increase in weight

Actually, 125/3100 is more like 4%.

forgot a 0 sorry meant to say less than 10%.

4% increase in weight with 4% increase in revolutions and an improved prop = more thrust = better performance than the F4. windscreen accounts for the remainder of the performance differences. 4% of additional weight that is internal doesn't affect top speed. it will affect climb, turn, and acceleration but not top speed. fwiw, the spitfire experienced a similar shift from early external armored windscreens to internal armored windscreens and there too an increase of top speed was had.

396mph for the F4 is a 9MPH difference from the G2's 405mph, or, a 2.27% performance advantage for the G2.

Edited August 12, 2021 by madrebel

[madrebel]

Let's break it down further.

109F4

2890KG with 1200PS@2500 rpm worth of power delivering a tested performance of 396MPH.

http://kurfurst.org/Performance_tests/109F4_Datenblatts/109F4_dblatt_calculated.html

ignore the tested speed of 660 in that test as it wasn't corrected, this test has the correct tested speed for 1.3aTa and 2500 RPM

http://kurfurst.org/Performance_tests/109F4_Datenblatts/109F4_dblatt_calculated.html

109G2

3130KG with 1350PS@2600 rpm worth of power delivering a tested 405mph

http://kurfurst.org/Performance_tests/109G1-6_datasheet/109G_perftable_EN.html

The G2/R2 listed there does have the camera but that weighs like 3-4kg at most so really ... doesn't affect anything.

Differences:

Weight difference of 240KG or 8.3% more weight for the G2

Power difference of 150PS or 12.5% more power for the G2

RPM difference of 100 RPM or 4% higher RPM for the G2

add in the new prop and the improved aerodynamics from the windscreen changes and you get a better 109 in all aspects of flight. what is the rationale then for the in game 109G2 being in fact slower than the F4? what is that decision based on?

Edited August 12, 2021 by madrebel

[madrebel]

Can this please get a 'under review' or 'ticketed' tag? All the evidence required is in this thread, the in game performance doesn't match up. thanks.

[BMBM]

I’ll ticket this.

[madrebel]

Danke. Not crazy high priority but accuracy is important. 

[BMBM]

Did some simple controlled testing.

F4 is slower than clean G2 at both sustained Max and sustained WEP at sea level.

Both crates hits the Rechlin numbers for SL far as I can tell.

[fidd]

On 8/12/2021 at 5:03 PM, madrebel said:

Did some offline testing to confirm after someone mentioned the G2 is slower than the F4 even after dropping the bomb.

http://kurfurst.org/Performance_tests/109G1-6_datasheet/109G_perftable_EN.html

Here we see two clean 109G2s flying in the 405mph range. Do note, the first G2 isn't clean as it has 2 x MG151 gondolas and a tested speed of 636KPH. A few lines lower we see a clean armed G2 with a camera installed reaching 652kph/405mph. Gondolas are reported to have a speed penalty in the 12-16kph range. here we see this tested and it is a 16kph difference.

For the F4, 635kph/394mph seems to be the general consensus for performance using the 30m power rating of 1.3aTa at 2500rpm. Clearance for the 1.42@2700rpm came later and brought the F4 right up to the 400mph mark, but we don't have that one and it should be noted the G2 was also eventually cleared for 1.42aTa@2800rpm too - neither is important to this discussion though.

Comparing the two directly leaves very little in terms of differences. As I recall, 125KG weight difference the vast majority of which was engine/oil weight. You might think, well, heavier plane will climb worse etc etc ... but you need to account for the improved VDM prop, the 100rpm difference between motors, and that 125KG added to ~3100kg is less than 10% increase in weight that will be significantly offset by an increase in thrust efficiency via the new prop as well as 100 additional revolutions of the prop. Lastly, the armored windscreen was moved from being an external addition to the wind screen to being an internal/integral redesign of the hood and this absolutely cleaned up the drag a bit. remember too that G2s were part of the later high speed dive tests conducted by the Germans. G2s hit .805 mach in those tests and well over 500mph.

the 109G2 was aerodynamically cleaner, flew faster, had better climb, and superior acceleration than the F4, full stop. it wasn't massive but it was better.

if you want a bomb laden 109 in tier2 that is NOT faster than the F4 you could have easily done this by adding a bomb to the F4 or adding a bomb to the F2. either of those are valid options. having a broken G2 is great and all but it isn't correct.

*edit* there was a radio upgrade as well as a radio antennae change as well from the F4 to the G2.

I should look into that more deeply, specifically the speed penalty for carriage of Gondolas. I do not believe for one instant that the "12-16kph" penalty for carriage of gondolas, is correct here, as they both reduce available clean-wing area, make a significant addition to zero-lift drag, and add considerably to the weight, all of which will affect achievable to speeds. 12-15kph is the sort of speed difference achieved by flush-rivetting and polished wings, not by getting rid of a ruddy great load of iron-mongery under the wing. I would expect a value more in the 50Kph range.

 

[madrebel]

On 9/28/2021 at 2:23 AM, fidd said:

I do not believe for one instant that the "12-16kph" penalty for carriage of gondolas, is correct here

this is a well established number. knock yourself out, i'm sure you'll find the correct answer 80 years and thousands of internet arguments later!

[vanapo]

On 9/28/2021 at 11:23 AM, fidd said:

I should look into that more deeply, specifically the speed penalty for carriage of Gondolas. I do not believe for one instant that the "12-16kph" penalty for carriage of gondolas, is correct here

go and change your mind: http://kurfurst.org/

[fidd]

On 9/28/2021 at 7:17 PM, vanapo said:

go and change your mind: http://kurfurst.org/

Thanks, I eventually found the correct part. There's no mention of the weight of the cannon and associated ammunition being part of the test, merely that a wooden representation of the Gondola was tested., which would only serve to indicate the loss of speed purely due to profile drag, rather than the sum of zero-lift and induced drag, which would be considerably more. As the 6kph figure makes no sense whatsoever to anyone with even a modicum of flying experience, there are clearly other factors at work here which are acting to reduce the loss of speed consequent from dragging around two whacking great gondolas, the cannon, and weight of additional ammunition, not to mention the loss of lift from the wing above the gondola having to be compensated for by additional lift from the rest of the wing..... This website may or not be reliable, however, to extrapolate from the declared test conditions to the statement that "the addition of Gondolas, cannon, plus ammunition on operational aircraft results in a speed difference of 6-19kph", is clearly well beyond what was actually demonstrated by the declared test, ie with just the gondolas shape in wood affixed to the wings, and without regard to additional weight etc,

The reason I baulked at the figures is simple, I had a long career flying numerous types of light aircraft, and the declared speed reduction simply made no sense. After that, it was merely a case of looking at what was different about the test, that might account for the too-good-to-be-true performance figure. Not mimicking the weight of guns and ammunition, and therefore reducing induced drag that would have occurred were the airframe to be heavier, would undoubtedly account for the discrepancy.. Accordingly this test is not a reliable underpinning for a statement that the difference in speed due to the carriage of weapons, gondolas and ammunition is in the order of 6-19kph.

I'm sure the test was done with all possible rigour, and for a specific purpose - likely measuring zero-lift drag (only) of the Gondolas would be my guess - but it doesn't say, I believe, what you've understood it to mean, because it does not declare that the test used appropriate weights etc. Please understand I'm not "having a go" at you here, it's an easy mistake to make unless you a) know it makes no sense and b) look for why it doesn't, in terms of the extrapolated statement about operational 100G's carrying the Gondolas, cannon and ammunition weight.

We need a documented, better test that also mimicks the weight/induced drag, not just the profile-drag of the wooden Gondolas. Jerry designers were pretty good, but they're not that good!

 

Edited September 28, 2021 by fidd

[greyman]

The 12-16 km/h figure always seemed too low to me as well -- based on British testing the effects various equipment had on the speed of their own aircraft.

A test of a 109 with mockup MK108 pods demonstrated a loss of only 8 km/h (!)

A VVS report appears to make more sense, with a speed loss of about 19 km/h. Still a remarkably low figure based on all of my hobbyist research. According to Russian-speaker input the data is probably averaged from several captured examples.

http://www.wwiiaircraftperformance.org/me109/VVS-Me_109_G2.pdf

EDIT: page 13

Edited September 29, 2021 by greyman

[vanapo]

Well, we could rather take the data provided by official tests conducted by various nations over a great span of time.... or we just take the data we made up ourselves because we like it more ... and who wants to listen to those eggheads, amIright?

The top speed of an aircraft depends on multiple factors, drag is only one of them. Weight is only one of them. There are quite some other factors as well, especially how and where this drag occurs and how it can be handled. Adding a bit of drag might slow down a plane not as much, if it has a very high engine power to weight ratio. The impact might be greater if the plane achieves the same top speed with a significantly worse power to weight ratio. A fixed landing gear is not that big of a deal if your plane is underpowered, big and slow in the first place. Adding a long pole to the nose of your plane would not decrease top speed very much ... as long as you never turn the slightest bit.....

I am doing somewhat poor on abstract math and physics, so I gonna stick with the legitimate data that is provided by credible sources. Like madrebel said, this data is quite consistent. Of course you can still refuse to believe it and some people will always tend to do so. The most game developers, on the other hand, stick with "we head into the direction, the official tests and the official data is pointing us to."

Edited September 29, 2021 by vanapo

[madrebel]

On 9/28/2021 at 4:30 PM, greyman said:

The 12-16 km/h figure always seemed too low to me as well -- based on British testing the effects various equipment had on the speed of their own aircraft.

A test of a 109 with mockup MK108 pods demonstrated a loss of only 8 km/h (!)

A VVS report appears to make more sense, with a speed loss of about 19 km/h. Still a remarkably low figure based on all of my hobbyist research. According to Russian-speaker input the data is probably averaged from several captured examples.

http://www.wwiiaircraftperformance.org/me109/VVS-Me_109_G2.pdf

EDIT: page 13

I don't read Russian but, 3KPH for a captured example when compared to Rechlin test data is statistically a wash and could be entirely accounted for by two different example aircraft alone. the russian example may have been -3KPH slower than the Rechlin example. 12, 16, or 19KPH speed difference is an extremely minimal difference.

[fidd]

On 9/29/2021 at 2:29 PM, vanapo said:

Well, we could rather take the data provided by official tests conducted by various nations over a great span of time.... or we just take the data we made up ourselves because we like it more ... and who wants to listen to those eggheads, amIright?

The top speed of an aircraft depends on multiple factors, drag is only one of them. Weight is only one of them. There are quite some other factors as well, especially how and where this drag occurs and how it can be handled. Adding a bit of drag might slow down a plane not as much, if it has a very high engine power to weight ratio. The impact might be greater if the plane achieves the same top speed with a significantly worse power to weight ratio. A fixed landing gear is not that big of a deal if your plane is underpowered, big and slow in the first place. Adding a long pole to the nose of your plane would not decrease top speed very much ... as long as you never turn the slightest bit.....

I am doing somewhat poor on abstract math and physics, so I gonna stick with the legitimate data that is provided by credible sources. Like madrebel said, this data is quite consistent. Of course you can still refuse to believe it and some people will always tend to do so. The most game developers, on the other hand, stick with "we head into the direction, the official tests and the official data is pointing us to."

An artfully constructed reply, but it does not alter the fact that declared conditions of the test do not specify that the weight of guns or ammunition was ballasted, so the conclusion you have drawn from the test is beyond what the data actually demonstrates. I'm certain that had such ballasting occurred, it would most certainly have been declared in the test parameters. 6-19kph is literally unbelievable. Silly in fact. 6ph is the sort of gain you get by polishing the leading edge and faring down rivet heads. Putting two large gondolas with a cannon in each and many Kg of ammunition, and a wing that'll perform less efficiently, puts the speed-change considerably greater than even 20kph. These tests (or rather your interpretation of what they mean) are not "pointing to" or "heading in the direction of" the conclusion you assert. Not even close. 

Given the frontal area of the Gondolas, and fairly large surface area (both zero lift drag) I'd estimate the speed reduction due to this alone would be in the order of 15 knots, with another 10-15 knots from induced drag, which comes out to circa 46-55kph in foreign. It'd be interesting to time trial the in-game Hurricane AT with a regular Hurricane, which although a slightly more severe increase in weight  from the cannon, than the 109g with gondolas, should give a ball-park indication of the sort of speed difference one might expect.

It seems to me you took one look at test you quoted, saw it as a small speed change, and then stopped reading it with a critical-eye. If you had looked at it more carefully you'd have spotted with what it took me all of 2 minutes to twig.

[madrebel]

3 hours ago, fidd said:

An artfully constructed reply, but it does not alter the fact that declared conditions of the test do not specify that the weight of guns or ammunition was ballasted

Doesnt really matter when the Russian test Greyman references, which would have used production gondolas (possibly sans full load of rounds), was within margin of error with the rechlin tests. weight isn't going to matter much at all for top speed, not compared to drag. weight will impact the 90 to 90 bank times greatly, but not top line speed.

fwiw there are british tests comparing the longer 20mm gun barrels to the shorter/flush barrels. As I recall it was around 5MPH difference but its been a long time. also, comparing what did or didn't change in terms of performance from two completely different airframes using completely different wings and wildly different drag profiles doesn't ball park anything.

[fidd]

9 hours ago, madrebel said:

Doesnt really matter when the Russian test Greyman references, which would have used production gondolas (possibly sans full load of rounds), was within margin of error with the rechlin tests. weight isn't going to matter much at all for top speed, not compared to drag. weight will impact the 90 to 90 bank times greatly, but not top line speed.

fwiw there are british tests comparing the longer 20mm gun barrels to the shorter/flush barrels. As I recall it was around 5MPH difference but its been a long time. also, comparing what did or didn't change in terms of performance from two completely different airframes using completely different wings and wildly different drag profiles doesn't ball park anything.

I would not expect the top speeds of the two dis-similar aircraft to be the same, but I would expect the difference in speed to be roughly the same for the both types carrying similar gondolas. I take your point about induced drag being relatively low at top speed S+L, that said, there's always a cost in additional drag with additional weight.

[vanapo]

34 minutes ago, fidd said:

there's always a cost in additional drag with additional weight.

And we know what it is because we have a multitude of data.Spoiler: It's about 12-16kph.

[fidd]

4 hours ago, vanapo said:

And we know what it is because we have a multitude of data.Spoiler: It's about 12-16kph.

You have non-comparable data, as far as an operational aircraft is concerned, because the quoted test doesn't contain all the variables, weight of ammunution cannon or even the Gondola. All you've done is cherry-picked a data set with a different set of conditions both to a operational aircraft, or indeed to other tests. If other tests appear to give similar results, there will be reasons why this is the case, such as different fuels being used, as self-evidently two tests with very different conditions cannot produce the same result, without other conditions being changed also.

Then there's the issue of the natural variation in performance, from the norm, which even nominally "the same" airframes have. Any pilot whose flown a number of aircraft of the same type, will know that individual aircraft all have their own foibles and slight eccentricities, relative one to another. One may show a disinclination to roll left, and other might require higher power-settings than another to maintain speed at a given pitch attitude. A sample of one is insufficient to state with certainty that it is representative of the type.

 

[madrebel]

21 hours ago, fidd said:

Then there's the issue of the natural variation in performance, from the norm, which even nominally "the same" airframes have

+/- 5% for German airframes. I used to have a chart showing multiple examples from the same factory, 2 of which as i recall were rejected. the rechlin example could have been the mean average and the russian test could have been a below mean but still acceptable example prior to being captured. impossible to know for sure and really a waste of time. we have the german test and the russian test which supports the german test. however since you're unhappy with the one test ... here is another later test note the weight difference between the G2 with gondolas and the G2/R2 recce

http://kurfurst.org/Performance_tests/109G1-6_datasheet/109G_perftable_EN.html

A MG151/20 weighs 47.2KG 'dry' so x2 and we're at 94.4KG

G2 with gondolas is 3260KG, G2/R2 is 3130KG for a difference of 130KG. We'll use the Minen round for weight which is listed at 104 grams and do note this is the heaviest of the 5 different types of HE(m) rounds the germans used.

https://en.wikipedia.org/wiki/MG_151_cannon#Ammunition_specifications

each gondola had 135 rounds * 2 * 104 grams = 28,080 grams or 20.8KG for a grand total of 94.4+20.8=115.2KG ... with a 130KG difference between the clean recce and gondola sporting 109G2 and the cannon + heaviest ammo accounting for 115.2 of that weight difference seems safe to assume the remaining weight is in mechanism and aluminum housing. do note however that to my knowledge the belting for the MG151/20 was always APT, HE, HE(m), HE, HE(m) or 2/5ths HE, 2/5ths HE(m), and 1/5th APT. it 'could' have been different for the gondolas i've honestly never seen a belting specific to these or the 190 gondolas. given that these were specific weapons were intended to be used against bombers, i wouldn't be all that surprised if the belting were slightly different biasing HE(m) over the HE, but, the APT had to be first to blow off the plastic cap.

so, ball is in your court. seems like the previous 25 years of online sleuthing and arguments have well and truly put this issue to bed ... for most at least. you're welcome to enlighten us though with the 'real' performance penalty of the gondolas.

*edit*

p.s. i've been looking for the weight of the Rb 50/30 camera and have thus far been unable to find it. Pictures of the camera don't suggest much more than a few KG at most though.

Edited October 1, 2021 by madrebel

[fidd]

Many thanks for the full reply, and calculation of the weights involved. I've not read the Russian or Rechlin reports, and am therefore unaware of the conditions under which those tests which weren't relevant to my observation that the test which only modelled the shape of the Gondola (in wood), and were therefore unreliable when determining the speed difference. Of the two other tests, I'd probably consider the Rechlin test as being more reliable than the British or Russian tests, due to differences in fuel, limited number of airframes to test and in the Russian case, the likely lack of rigour.

115kg is not a trivial increase in weight for a small single-seat fighter. Self-evidently, I cannot, lacking a 109g of my own, test it. That said, I find the initially quoted figures (based on the contentious test) to be very, very surprising, based on a couple of decades flying experience, flying similar small aircraft with a variety of loads, with and without wheel spats and so forth, which experience is suggesting to me that the figure of 6ph is far, far, too low, and that, at the very least, these figures need to be looked at more critically, to see if the test conditions actually allow the inferences as to operational aircraft's performance may be safely drawn. I do not see the passage of time since the tests were done, as being indicative of conferring such confidence. YMMV of course.

[vanapo]

5 hours ago, fidd said:

Many thanks for the full reply, and calculation of the weights involved. I've not read the Russian or Rechlin reports, and am therefore unaware of the conditions under which those tests which weren't relevant to my observation that the test which only modelled the shape of the Gondola (in wood), and were therefore unreliable when determining the speed difference. Of the two other tests, I'd probably consider the Rechlin test as being more reliable than the British or Russian tests, due to differences in fuel, limited number of airframes to test and in the Russian case, the likely lack of rigour.

115kg is not a trivial increase in weight for a small single-seat fighter. Self-evidently, I cannot, lacking a 109g of my own, test it. That said, I find the initially quoted figures (based on the contentious test) to be very, very surprising, based on a couple of decades flying experience, flying similar small aircraft with a variety of loads, with and without wheel spats and so forth, which experience is suggesting to me that the figure of 6ph is far, far, too low, and that, at the very least, these figures need to be looked at more critically, to see if the test conditions actually allow the inferences as to operational aircraft's performance may be safely drawn. I do not see the passage of time since the tests were done, as being indicative of conferring such confidence. YMMV of course.

So what data do you propose to rely on as you seem to doubt the official data of actual testing been done on an actual plane close to the actual timeframe it actually flew at and lacking an actual plane of your own but keep demanding to "correct" the data of actual  testing that has been done on an actual plane close to the actual timeframe it actually flew at ?

Edited October 1, 2021 by vanapo

[fidd]

17 minutes ago, vanapo said:

So what data do you propose to rely on as you seem to doubt the official data of actual testing been done on an actual plane close to the actual timeframe it actually flew at and lacking an actual plane of your own but keep demanding to "correct" the data of actual  testing that has been done on an actual plane close to the actual timeframe it actually flew at ?

I already answered this upthread. Of the various tests on the website, my instinct is that the Rechlin tests are more likely to be accurate, although as yet I've not read them, or the Russian or British ones, simply because the Rechlin tests were more likely done with the same fuel as the operational fighter, meaning that the Rechlin test is more likely to be accurate both in terms of the top speeds attained, as well as the difference in speeds (as evidence of an operational fighters speeds). The British test was almost certainly done with 100 Octane, and therefore the top speeds attained may have been a little higher than those of an operational 109g flown by the Luftwaffe. The difference in speed being likely fairly accurate. The Russian test I couldn't give an opinion on, as I don't know anything about Russian fuels then available.

[madrebel]

On 10/1/2021 at 3:29 PM, fidd said:

British test was almost certainly done with 100 Octane

Don't forget to translate this too. German B3 had an average octane rating of 91 as measured by the US in a post war study of German fuels. This is equivalent to British/US 100 'grade'. German C3 with an average of 95 Octane was seen as generally similar to British/US 100/130 grade. The very rare C3+ or C4 was then similar to Brit/US 150 grade but was very very rare prior to the raids on German fuel production, non existent after.

The point is, if the Brits used 100 octane, thats very similar to B3.

 

*edit* report for reference - http://kurfurst.org/Engine/Fuel/mof-secth_Testing_and_Evaluating_Products_via_Fischer-Tropsch_Archieves.pdf

 

Edited October 4, 2021 by madrebel