109 performance notes

[gripen]

Originally posted by Kurfürst
The 109G was originally planned to have well doors, but in the end only a few got them.

Actually some FAF Bf 109G-2s had hydraulic lines fitted for the wheel doors and even some G-6s had them.

gripen

[Charge]

What about the effect of air temp and humidity between calculations and real flight testing?

-C+

[gripen]

Originally posted by Charge
What about the effect of air temp and humidity between calculations and real flight testing?

AFAIK Mtt calculations are based on CINA atmosphere and in the MT-215 tests conditions were quite near CINA standard (according to the report).

gripen

[Porta]

gripen,

The calculations for the start model (Me 109 G-1 Ausführung), for which those calculations (Me 109 G-1 Endzustand) were based on, are outlined in sheets IV/42/42 (Vorbemerkungen zum Datenblatt...) and IV/43/42 (Datenblatt...).

The "starting" numbers are (Kampfleistung, n = 2600 U/min):

- 0 m : 535 Km/h
- VDH: 660 Km/h @ 7000 m

With this in mind, the fantastic performance of the "Me 109 G-1 final condition" initially calculated is more "believable". But, as I said, the calculations for the basic model might bring even more heated discussions than the ones you initially showed...

[gripen]

Originally posted by Porta

The calculations for the start model (Me 109 G-1 Ausführung), for which those calculations (Me 109 G-1 Endzustand) were based on, are outlined in sheets IV/42/42 (Vorbemerkungen zum Datenblatt...) and IV/43/42 (Datenblatt...).

The "starting" numbers are (Kampfleistung, n = 2600 U/min):

- 0 m : 535 Km/h
- VDH: 660 Km/h @ 7000 m

With this in mind, the fantastic performance of the "Me 109 G-1 final condition" initially calculated is more "believable". But, as I said, the calculations for the basic model might bring even more heated discussions than the ones you initially showed...

Yep, I know but I'm merely using the posted datasheet as an example how a calculation (at what ever condition of the plane) can give quite false indication of reachable performance.

Overall the main problem in these calculations (Ausführung or Endzustand) is that the engine did not reach the estimated altitude performance. But even if the engine had lived up to the estimations, the high altitude performance would have been quite bit lower than in calculations, at least with the given propeller. At low altitude the difference to flight tested performance is quite low, say 10-20 km/h but at high altitude the gap is quite large.

Anyway, Mtt was not alone with these estimation problems and that is what I'm promoting here ie importace of flight tested data.

gripen

[Crumpp]

Yep, I know but I'm merely using the posted datasheet as an example how a calculation (at what ever condition of the plane) can give quite false indication of reachable performance.

It is not a false indication, you just do not take all the factors into consideration.  In short you make assumptions which are not correct.

Anyway, Mtt was not alone with these estimation problems and that is what I'm promoting here ie importace of flight tested data.

Your not promoting anything and how arrogant of you to make such a claim.  You simply posted a troll which is a non-issue. The numbers listed by Mtt are flight tested data.  The sheet posted in this thread is unknown however it has great agreement with the mean average of flight test data from another report.  

There is no estimation or calculation problem except of your own invention.

Calculations are generally conservative and not optimistic.

No one has claimed calculations should replace flight tested data in this thread or anyother thread.  Much of the time flight tested data is the better of the two!

What has been shown through documentation  is:

1.  Flight tested data falls within a wide range of performance based on manufacturers guarenteed percentages within the same design.

To argue over an exact number is rather silly especially when that number is the manufacturer's specification as published by the end user organization.  

2.  Calculations tend to be conservative not optimistic.

All the best,

Crumpp

[Bruno]

Originally posted by elkaskone
Hi Bruno,

on your second 109G14 Dokument is there a weight indicated?
Maybe the slower speeds are with Mg151/20 gondolas?!

The first Document i now its a clean 109G14-U4 with 3318kg!

I don't have access to the documents. I simply ran accross that info while over at LEMB while looking for G-14 paint schemes for a skin I am doing.

I posted it here in hopes that some one else might have them.

My first thought on the lower numbers was that it may have had gondolas.

[gripen]

Originally posted by Crumpp
It is not a false indication, you just do not take all the factors into consideration.  In short you make assumptions which are not correct.

I have no idea what you are trying to argue, I don't make any particular assumptions. I simply compare documented test data to the calculations.

Originally posted by Crumpp

Your not promoting anything and how arrogant of you to make such a claim.

Maybe you should leave personal attacks out of this thread and post data and facts instead.

Originally posted by Crumpp

You simply posted a troll which is a non-issue.

I have no idea what you are trying to argue, my first post to this thread was simply a note that GL/C-E data seem to a calculation and the Mtt data is an example how some caculations were unreachable in real life due to various reasons (engine not giving the expected performance, propeller efficiency etc.).

Originally posted by Crumpp

The numbers listed by Mtt are flight tested data.  The sheet posted in this thread is unknown however it has great agreement with the mean average of flight test data from another report.  

If the datasheet says "Rechnung" or "errechnete werte" there is no question if these are calculations or flight tested. If you want to prove that there is a great agreement, just post the data instead personal attacks.

gripen

[Crumpp]

just post the data instead personal attacks.

There are no personal attacks in anything I posted, Gripen.  You were not promoting anything and are making a baseless claim.  Even if the data is calculations, it is conservative and not optimistic.  I see nothing on the data sheet I posted on the Bf-109G14 which says calculations.  You are the one making that claim and have not proven it.

We only have your word.  

Please point out on the data sheet I posted where it says:

If the datasheet says "Rechnung" or "errechnete werte" there is no question if these are calculations or flight tested. If you want to prove that there is a great agreement, just post the data instead personal attacks.

Your "IF" does not apply so far.

I have an actual flight test report as well as the Flugzueg-Handbuch data on the Bf-109G14 to compare.  Both say the sheet is well within Mtt specifications for an average performing Bf-109G14 in clean configuration.

I don't make any particular assumptions.

Obviously if you assume all the data you need is:

the type of the plane, speed values, weight, the type of the engine, setting of the engine etc. All are readable.

To determine what the "correct" performance "should be" of a given type then you are making some large assumptions that will often lead you to incorrect conclusions.

Especially if you are trying to compare flight tested data from one or two data points.  Good example of your margin of error is found in the Me262 flight test data points:

http://img21.potato.com/img.php?loc=loc132&image=20b_Me262performance.jpg

Mtt data is an example how some caculations were unreachable in real life due to various reasons (engine not giving the expected performance, propeller efficiency etc.).

Sure a few calculations are optimistic.  However this is very much the exception and not the rule.  

You are trying to create the impression that calculations are almost always optimistic.  

Again, examine the Me 262 calculated performance document vs flight tested data.  Here is the Bf-109F4 performance estimates:

http://www.beim-zeugmeister.de/zeugmeister/index.php?id=27&L=1

AT 1185PS @ 6KM altitude we see a top speed of 635kph calculated.

In the flight tested data we see at 1180PS @ 6.2KM a top speed of 660kph:

http://www.beim-zeugmeister.de/zeugmeister/index.php?id=26&L=1

A 25kph increase over the calculated performance and very good agreement for a performance estimate.

In the Me 262 we see an increase of almost 50kph in the flight tested data OVER the performance estimate calculations.

The Focke Wulf estimates run about 15kph slower than the flight tested data.

Simply put, you have raised a non-issue.

All the best,

Crumpp

[Kurfürst]

Originally posted by Porta


The "starting" numbers are (Kampfleistung, n = 2600 U/min):

- 0 m : 535 Km/h
- VDH: 660 Km/h @ 7000 m

Originally posted by gripen


....what I'm promoting here ie importace of flight tested data.

That's great gripen, but tell us first why you presented that calculation in a dishonest manner, telling only half the truth about the conditions? Because it's plain simply to see what you did, you tried to dismiss G-14 saying that it's calculations only (which you did not prove), and calculations are very unreliable, especially that of Mtt. For that you brought us an example that bad Mtt calculated 737 km/h - only you 'forgot' to tell the conditions were special with great change in finish compared to the serial planes, simple to put you manipulated with the evidence didn't you? For the serial condition we are interested in Mtt appearantly calculated, as said :

"(Kampfleistung, n = 2600 U/min):

- 0 m : 535 Km/h
- VDH: 660 Km/h @ 7000 m"

Curiously, the Russians did actual flight tests with a Me 109G-2 at Kampfleistung, too. What happens, they got almost the same numbers as Messerschmitt AG calculated, they got 530 kph at SL (+5) and 666 kph at 7000m :

http://www.pbase.com/isegrim/image/11679724

In other words, Messerschmitt's calculations, which you claim to be non-representative, were SPOT ON on the VDH, and actually pessimistic by 5kph ... here crumbles the theory about calculations being totally different than flight tests.

Rechlin measured 650 kph at 7000m for another 109G-1, for which the plane conditions are unknown, which was the figure that was officially accepted and published for the 109G-1/2 :

http://www.pbase.com/isegrim/image/9759597

[gripen]

Originally posted by Crumpp

There are no personal attacks in anything I posted, Gripen.
 

At least in my scale calling some one's actions arrogant is quite personal.

Originally posted by Crumpp

I see nothing on the data sheet I posted on the Bf-109G14 which says calculations.

As noted above in the same data set there is exactly same speed values for the G-14 dated 13.8.1944 and marked as Rechnung just like all other values from the same date.

Originally posted by Kurfürst

Curiously, the Russians did actual flight tests with a Me 109G-2 at Kampfleistung, too.

Did the Russians actually do the full speed tests?

gripen

[Crumpp]

At least in my scale calling some one's actions arrogant is quite personal.

They were arrogant.  Spade is Spade.  I don't see where it says calculations anywhere on the document you posted.  Of course it is unreadable for the most part.

You mean they will clearly be labeled calculations at the top of the page just like this one?
 

All the best,

Crumpp

[gripen]

Originally posted by Crumpp
They were arrogant.

So in my scale you are taking this personally.

Originally posted by Crumpp

I don't see where it says calculations anywhere on the document you posted.

"Rechn."  means "Rechnung" ie calculation. If it's flight tested it should be marked as "Erfolgen" and nothing on these documents indicates that the values are flight tested.

gripen

[BlauK]

grippen,
look the word up from a dictionary.

It refers to your actions, not to your person. One's actions can be seen as aggressive, defensive, arrogant, flattering, etc. It is not like calling you names or such.

Seems to me, that sometimes when you cannot base your arguments on data, you revert to playing silly tricks with semantics. Please look back at the theme of this thread and present your arguments with data.

If your only argument is that calculations do not always provide reliable data, why are you bringing it into discussion about how the "new" 109:s perform in the game? Do you even play the game? Furthermore, your evidence cannot claim that calculations never provide reliable data... so what is the point?

If you want to argue about flight test data and calculation, start a new thread. Include the allied data and calulations to that discussion as well. Actually I have yet to see you criticize any allied data on these boards... then again, I have not been reading such threads with great interest.

It has been interesting, again, so far. Please keep it that way, and dont begin whining about personal attacks when your actions are being criticized.

[justin_g]

IMO, if WW2 engineers could produce calculations that fall within the (usually 3%) tolerance for performance(I believe they could), then it doesn't matter if the data is calculated or recorded from flight.

What DOES matter is the condition of the aircraft in question - as has been pointed out - the 732kph G-1 was not based on a standard condition serial aircraft.

If a calculated data sheet is based on an aircraft of the SAME condition as what was actually manufactured then it should be treated as worthy as flight test data for the purpose of modelling in a computer game simulation!