Exhaust Thrust ????

[Kwiatek]

He mention 18 m/s for P-51

[Kwiatek]

 

There is NO flight tested data of an FW-190D9 climbing using MW-50 at 1.8ata @ 3250rpm.

 

When you run the math it all agrees...The Dora in DCS climbs as it should with the additional power of 1.8ata @ 3250rpm.

 

What do you propose ED does? Not model the aircraft with any additional power, just limit it to the lower power setting in a climb?

 

:noexpression:

 

Dunno but what about these chart for D-9 at 4350 kg?

 

[Crumpp]

Dunno but what about these chart for D-9 at 4350 kg?

 

Which matches Flugmechanik calculated performance.....

 

That is not a flight test. Notice Notleistung m MW50 curve is not part of curves 1, 2, and 3, which have defined aircraft conditions according to the legend.

 

He mention 18 m/s for P-51

 

Which is excellent agreement with the actual aircraft's performance and is only 50 fpm short of the aircrafts 3600 fpm climb rate for a example some 300lbs lighter.

 

Yes the P-51 climb performance gives good agreement and is slightly optimistic compared to the average example.

 

NAA also underestimated their aircraft's performance. Here we see a 10,000lb airplane should be climbing at ~3200 to 3400fpm at sea level.

 

http://www.wwiiaircraftperformance.org/mustang/na-46-130-chart.jpg

 

The DCS Mustang at 1066lbs climbs at 3543fpm.

 

In the calculation NAA predicts a 9611lb airplane should climb at 3410fpm at 67" @ sea level.

 

http://www.wwiiaircraftperformance.org/mustang/p-51d-na-46-130.html

 

Here we see a 9760lbs airplane in a flight test achieves 3600 fpm at 67" @ sea level:

 

http://www.wwiiaircraftperformance.org/mustang/p51d-15342.html

 

That puts the NAA climb prediction some 5% pessimistic when compared to flight testing.

 

As a general rule, calculated performance is almost never optimistic. Why? Making an optimistic performance estimate that the company cannot deliver on in flight makes the company look stupid and the customer unhappy.

 

It is a great way to never sell another airplane.

Edited March 11, 2015 by Crumpp
Combined two post's

[Alladyn]

The things I keep learning since I started using combat flightsims!

 

Reading that Dora climb rates thread I just learned that the exhaust thrust is indeed something that adds significant power to the total thrust available from the engine? I was looking forward for it only when I get the Me-262 :-)

 

I was totally unaware of it's importance in a ww2 prop fighter before!

 

Thx guys, GrapeJam, Solty, Crummp, gavagai, Pilum, ... ( by order of appearance in the thread... ) and Yo-Yo "DA MAN!" who gives us this great models and flight / overall physics modeling that come with them :-)

 

 

Not even 2 Lt of stewed beans could get me that additional power when flying my glider :) and the outcome would be disgusting!

 

23:30 min here: "the exhaust thrust" 20-25mph faster in spitfire ^^

Edited March 11, 2015 by Alladyn

[Solty]

At 4175Kg.....

 

And it should be 19.5 m/s at sea level at 4070kg....

 

http://www.wwiiaircraftperformance.org/fw190/Fw_190_V53_climb.jpg

 

Which means the FM is spot on and additional climb performance is the result of additional power at 1.8ata using MW-50.....

 

Understand? It is just physics man!!!

 

I was saying for P-51D. Not for Dora

 

And you are saying it's suppose to be 19m/s but in DCS Dora goes 28m/s lol

 

Also, Crummp. Please take my whole post and answer it as a whole. You are just taking bits of my post and counter-argumenting them even though it is the followup that is crucial to the essence of the issue.

Edited March 11, 2015 by Solty

[Solty]

At 100% fuel?

No... I think it was 81%. I was trying to get the same weight on take off as the tests. And it was 9760lb. Which in all actuallity is 81% of fuel.

 

That gave me back then a performance around 18m/s at SL. So P-51 seems to be near perfect to the data given.

 

But I encourage you to test it yourself. Here is ROC for P-51D at 67' with 9760lb http://www.wwiiaircraftperformance.org/mustang/P-51D_15342_Climb-Fig5.jpg

 

Edited March 11, 2015 by Solty

[RAZBAM_ELMO]

God this is why I love DCS

[Solty]

God this is why I love DCS

This is why DCS gives me hypertension.:P

Edited March 11, 2015 by Solty

[ARM505]

I've had the displeasure of browsing through too many Warthunder forum posts recently.....*Ugh, washes hands, can't escape dirty feeling* I only play WT for the tanks (bad enough), but even coming close to those aircraft make me feel unclean :)

 

It's really nice to read some proper technical stuff again, thanks all. DCS still the champ.

[GrapeJam]

Let's see.

 

If you ran a company that guaranteed a 10% performance variation by contract meaning the customer does not have to pay for any aircraft that fall below that 10% margin....wouldn't you do something to ensure you could always meet that requirement?

 

I would.

 

:smilewink:

Yeah, except when said company is in country that is being daily bombed, on the verge of defeat, is desperate for anything better than what they currently have(the Dora itself is a creation of desperation in waiting for the Ta 152).

 

Please use actual common sense.

 

The only data that the DCS Dora does not match is the ONE calculated performance report. That calculated report does not include exhaust thrust effects.

I'd like to see where is it explicitly stated that exhaust thrust was not included. Edited March 11, 2015 by GrapeJam

[Crumpp]

Yeah, except when said company is in country that is being daily bombed, on the verge of defeat, is desperate for anything better than what they currently have(the Dora itself is a creation of desperation in waiting for the Ta 152).

 

Please use actual common sense.

 

Extremely offensive, immature, and uncalled for Grapejam. Please discuss this like an adult using facts to advance your argument and not an emotional plea.

 

Do you really think it would common sense to over estimate and lie on a piece of paper promising something you could not deliver in any circumstances?

 

Once again, it is fact that North American Aviation also underestimated the P-51's climb performance in their calculations. You will find most performance calculations are pessimistic in the performance they report.

 

How do you explain that? A lack of common sense? :music_whistling:

[Yo-Yo]

Yeah, except when said company is in country that is being daily bombed, on the verge of defeat, is desperate for anything better than what they currently have(the Dora itself is a creation of desperation in waiting for the Ta 152).

 

Please use actual common sense.

 

I'd like to see where is it explicitly stated that exhaust thrust was not included.

 

Can you mention a physical law explicitly stated and signed: "Approved. The God"?

[Crumpp]

Also, Crummp. Please take my whole post and answer it as a whole

 

Which I am Solty. I read your post and answer it. Please return the same courtesy.

 

So P-51 seems to be near perfect to the data given.

 

While it gives good agreement, it is actually slightly optimistic. The DCS P-51 is heavier due to the tail warning radar and matches the climb performance of a 300lbs lighter variant.

 

Bottom line is there is nothing to complain about in either FM.

Edited March 11, 2015 by Crumpp

[Anatoli-Kagari9]

NOTAM: This thread is meant to be, above all, a recognition of the detailed modeling work done by DCS ( and in particular "yo-yo" ) in the development of their ww2 modules.

 

Above all I am sure that yo-yo is totally impartial regarding the way he seeks to model his ww2 fighters, and in the very first place, he want's to deliver, from a dev but above all from a flight dynamics computer-based simulation PoV the best possible performance and realism.

 

All contributions from those who can offer their knowledge or documents is certainly welcomed, and I am sure that all of us want exactly the same - to continue to feel that indeed DCS World is probably the combat flight simulator where this commitment to accuracy and as close as possible in a PC-based flight simulator, plausibility, is taken to the higher levels among the various alternatives available.

 

So, please, try to continue the thread with the very same spirit it was initiated - POSITIVENESS!!!!

 

Allow me to leave here a link to a totally unrelated but rather positive and beautiful experience, whose footage I came across just a couple of days ago...not in combat flight, but rather in soaring :) Those instructors and the children enjoying a great time have in common exactly the same we have, after all - a Passion for Aviation !

 

Let's be Passionate, not derogative ... This is Kindergarten!!! as far away as possible from our daily stresses and frustrations ....

 

Please RELAX and ENJOY!

Edited March 11, 2015 by jcomm

[GrapeJam]

 

Once again, it is fact that North American Aviation also underestimated the P-51's climb performance in their calculations. You will find most performance calculations are pessimistic in the performance they report.

 

How do you explain that? A lack of common sense? :music_whistling:

 

So you use one example of a company that is being pessimistic in one performance calculation test as the proof that Focke Wulf's also pessimistic in their calculation? Really?

 

I can show loads of calculated being "optimistic", in fact calculated performance is usually optimistic than actual production version.

 

Compared to this:

http://www.wwiiaircraftperformance.org/P-63/P-63A_42-69417_TSCEP5E-1938.pdf

 

http://forum.warthunder.com/index.php?/topic/43717-spitfire-mk-ix-too-slow/?p=612281

 

Do we need to talk about the Horten's calculated claim of the Ho 229 being able to reach 1000km/h, or Soviet planes calculated tests alway have higher performance than the actual production planes?

[GrapeJam]

Can you mention a physical law explicitly stated and signed: "Approved. The God"?

And how can you be so sure that Focke Wulf's performance does not factor in exhaust thrust, if, I say if, the tests reports don't mention anything about exhaust thrust?

[GrapeJam]

Which I am Solty. I read your post and answer it. Please return the same courtesy.

 

 

 

While it gives good agreement, it is actually slightly optimistic. The DCS P-51 is heavier due to the tail warning radar and matches the climb performance of a 300lbs lighter variant.

 

Bottom line is there is nothing to complain about in either FM.

 

The APS/13 tail warning radar system weighted a whooping 25lbs. I don't know where did you get this "300lbs" figure.

http://www.hawkertempest.se/index.php/contributions/stories/134-the-electronic-war-and-the-tempest

2. The A. N. A. P. S. 13 consists of a Unit of approximately 15" by 8" by 10" overall dimensions, mounted on the port side of the aircraft behind the pilot. The pilot's control box is mounted on the starboard knock out panel and carries an on/off switch and a test switch for the indicator lamp, which is mounted near the gun sight. The indicator lamp will light up at a range, which is pre-set on the ground. A single dipole aerial is carried on the port wing near the wing tip. The overall weight of the equipment is approximately 25 lbs.

Edited March 11, 2015 by GrapeJam

[Anatoli-Kagari9]

http://www.wwiiaircraftperformance.org/fw190/BMW-VB-126.html

 

Under I.2 we can read:

 

"A follow up check of the speed change with

v2 / v1 = N2 / N1 accounting for exhaust thrust with the power, the speed variances were below 0,5%."

 

And Crumpp, old chap!!!! You were already there in 2005 :-), just like me ;-)

 

http://bbs.hitechcreations.com/smf/index.php?topic=146949.60

Edited March 11, 2015 by jcomm

[Yo-Yo]

And how can you be so sure that Focke Wulf's performance does not factor in exhaust thrust, if, I say if, the tests reports don't mention anything about exhaust thrust?

 

I can not say more than I have said. Except the obvious fact that flight performance tests deal with the plane AS IT IS with its prop, exhaust stacks,etc. The only case you can see something about jet thrust when various exhaust stacks are tested in comparison.

[Crumpp]

Good post Jcomm.

 

One the best thing's in Aviation is passing it on to the kids.

[Solty]

Can you mention a physical law explicitly stated and signed: "Approved. The God"?

I do not agree with you YoYo. So far we have presented real, hard data that FW190D9 with different power settings could go through variety of ROC but not a single chart has shown that the Fw190D9 could be capable of anything more than 23m/s, let alone 28m/s.

 

 

You have not presented anything to prove that your FM is indeed correct. As I see it. The FM has overclimbing issue of around 6m/s in sustained climb.

 

There is no data available that says "these tests do not contain exhaust thrust".

 

Foke-Wulf company data shows clearly that 1.8ata version should reach 22m/s climb rate sustained.Those are facts. Not just guessing.

[Crumpp]

I can show loads of calculated being "optimistic", in fact calculated performance is usually optimistic than actual production version.

 

Experimental vs New type vs production...depending on the purpose of the report.

 

It depends on who the information is for Grapejam. If is it for the company internal staff to expand its capability boundaries thru an experimental or new type design, I would agree.

 

If the information meant for a potential buyer, as a general rule it tends to be pessimistic.

 

That is not to say mistakes do not happen. Rules made by man do get broken.

 

Which brings us to this:

 

Under I.2 we can read:

 

"A follow up check of the speed change with

v2 / v1 = N2 / N1 accounting for exhaust thrust with the power, the speed variances were below 0,5%."

 

Great find...that is Focke Wulf telling us the difference in their estimates vs flight tested performance.

 

That is a flight test of Erhöhte Notleistung.

 

http://www.wwiiaircraftperformance.org/fw190/BMW_VB_126.pdf

 

 

So far we have presented real, hard data that FW190D9 with different power settings

 

You have presented data but are not correctly interpreting it for different conditions of flight.

 

The APS/13 tail warning radar system weighted a whooping 25lbs. I don't know where did you get this "300lbs" figure.

 

That is good information. Our DCS Mustang weighs 10,066lbs clean configuration with full fuel.

 

I do not have a weight and balance sheet for the P-51 that reflects the tail warning radar I just know there is 300lbs difference from the weight and balance sheets I have on the design.

[Crumpp]

This will help folks to gain an understanding of how to align some of the data found in these reports.

 

From the Air Ministry, UK:

 

NOTES ON THE USE OF PERFORMANCE ESTIMATES

 

http://www.spitfireperformance.com/spittest.html

 

The terminology might change New Type, Experimental, Original Estimate, Provisional, Final, etc. The specific language is unique to the culture and country but the principle remains the same.

[NineLine]

I do not agree with you YoYo. So far we have presented real, hard data that FW190D9 with different power settings could go through variety of ROC but not a single chart has shown that the Fw190D9 could be capable of anything more than 23m/s, let alone 28m/s.

 

 

You have not presented anything to prove that your FM is indeed correct. As I see it. The FM has overclimbing issue of around 6m/s in sustained climb.

 

So maybe its at this point you go start your own sim company and make your own FM, because its getting tired that you some how "demand" proof of FM making abilities when he has created so many quality FMs already. He can only answer your questions so many times, and this is a copy of a thread that got locked once already, and this one is headed that way as well...

 

To expand, Yo-Yo has been researching this FM for some time, he works hard to get it as accurate as humanly possible, but dont take any evidence you can find on the internet at face value, and dont assume because you found a couple test on some random website that you are now an expert in the flight characteristics of any aircraft. If he believes something is missing of a particular document based on his research, then that is his/ED's interpretation... and should be respected based on his/their proven history at FM creation.

Edited March 11, 2015 by NineLine

[GrapeJam]

Experimental vs New type vs production...depending on the purpose of the report.

 

It depends on who the information is for Grapejam. If is it for the company internal staff to expand its capability boundaries thru an experimental or new type design, I would agree.

 

If the information meant for a potential buyer, as a general rule it tends to be pessimistic.

 

That is not to say mistakes do not happen. Rules made by man do get broken.

 

Yeah, like Messersmitdh's extremely pessimistic calculated performance of the Me 209, Me 309. The Bell charts that I've shown were also for buyers btw. If anything it's general rule that estimated performances tend to be optimistic.

 

Which brings us to this:

 

 

 

Great find...that is Focke Wulf telling us the difference in their estimates vs flight tested performance.

 

That is a flight test of Erhöhte Notleistung.

 

http://www.wwiiaircraftperformance.org/fw190/BMW_VB_126.pdf

And if Focke Wulf's estimation is so accurate (less than 0.5% variance) why should you think there should be such a large disparagement of the D9's calculated performance versus real product.

 

In fact, by march 1945 there were plenty of flying D9s in combat already, it would make no sense for Focke Wulf to keep the same test figure in their march 1945 test document if it wasn't accurate.

Edited March 11, 2015 by GrapeJam