Horton

[Crumpp]

All I am saying is the 'reason' the inner wing was swept to correct the cg,

No the reason the inner wing was not swept is due to stability and control issues with engine nacelles. Tractor propellers and jet intakes forward of the CG exhibit a destabilizing force at high coefficients of lift. In a turn, the destabilizing force in wing mounted nacelles is not symetrical.

Adding sweep lowers and flattens the CLmax but extends the available angle of attack so that the wing achieves more angle for a lower coefficient. In otherwords, it increases the destabilizing force of the nacelles.

Mtt did not sweep the inner wing to reduce this effect. In the second design, they did not add sweep only because they understood the basic's of swept wing theory. Unlike anybody in the mainstream aircraft designers of United States or Great Britain at the time.

After flight testing though, the original high aspect ratio wing design CG limits were not suitable for the higher mach limits the outboard sweep allowed.

As an aircraft enters transonic flight, the progression of the normal shock moves the AC rearward reducing the elevators effectiveness.
Additionally, the downwash angle behind the wing is decreased due to the seperated flow behind the normal shock. This increases the angle of attack of the horizontal stabilizer which is the main cause of mach tuck.

An airplane originally designed to have a straight wing would need to expand the forward CG limits if you are to increase the elevators effectiveness if you are going to fly in the transonic realm.

and 'reason' the outer wing was swept to correct the air separation..

Well duh....

What do you think raising critical mach number is all about?? That is the whole point of adding sweep!!

Behind the normal shock is seperated flow. If we increase the critical mach, we reduce the amount of seperated flow on the wing.

[ACE-OF-ACES]

Originally Posted by Crumpp

No the reason <snip>

Now don't take this personal!

But I am going to stick with the Me262 experts (Jenkins and STORMBIRDS) on this one..

Who said..

• The 'reason' the outer wings were swept was to correct the cg.

• The 'reason' the inner wings were swept was to correct the airflow separation.

It is nothing personal!

It is just when you consider the fact that Dennis Jenkins has written more aviation books than most people have read, and that the folks at STORMBIRDS surly reviewed all the research on the Me262 during the process of building reproductions of the Me262.

It would be silly to pick you over them!

But I still want to thank you for sharing your personal beliefs and opinions!

But to be honest, I really don't care about what you personally belive and your opinions!

All I care about is what can be proven.

I mean if we don't draw the line there was is to stop someone from posting in this thread that they 'belive' and are of the 'opinion' that the Germans were assisted by aliens from outer space?

So with that said I think you can understand why I drawn the line there..

I also want to thank you for information and calculations you provided!

But I am sure the likes of Dennis Jenkins and STORMBIRDS are privy to that same information/calculations and MORE and took it all into account during their research of the Me262 and their ultimate statements on the reason why the wings were swept.

Which begs the question as to why they didn't come to the same conclusions you did?

I suspect they wanted to..

In that the whole history channel 'the Germans were supermen' stuff sells these days..

Especially the folks at STORMBIRDS who are pro German tech biased..

But I suspect the stopped short of making the claims you made because they just could not find any real proof of the connections your claiming are there. That and unlike you they have a reputation to consider! I mean think about it, nothing would hurt their image, and thus sales, more than for them to say something they said was based on proof only to find out later there was no proof!

So with that said..

We will just have to agree to disagree as to the reasons why the wings were swept on the Me262

S!

[Crumpp]

you made because they just could not find any real proof of the connections your claiming

Thank you for the laughs!! I guess you don't understand the fact your sources are not wrong at all. They only convey a portion of the story but their facts are correct.


The information I posted comes from:

AIAA is the world’s largest professional society devoted to the progress of engineering and science in aviation, space, and defense.

Today, with more than 35,000 members, AIAA is the world's largest professional society devoted to the progress of engineering and science in aviation, space, and defense. The Institute continues to be the principal voice, information resource, and publisher for aerospace engineers, scientists, managers, policymakers, students, and educators.

You do realize that in the decades since WWII, we in the United States have had time to sort through the data compliled by the Germans. We have a much better understanding of their work and swept wing theory.

That is why those papers were published and presented at conferences for engineers and scientist.

In 1946 when the NACA and USAAF references your "experts" use were written, the United States had little to know understanding of swept wing theory.

Notice the P-80 had straight wings.....


Yes, the outer wings were swept to eliminate flow seperation!!

What do you think raising critical mach number is all about?? That is the whole point of adding sweep!!

Behind the normal shock is seperated flow. If we increase the critical mach, we reduce the amount of seperated flow on the wing.

Yes, the aircraft benefited from just 18 degrees of wing sweep!!!

Our critical Mach number is raised by reciprocal of the cosine of the angle of sweep. So for 18 degrees of sweep we see a 1.05146 increase to critical mach.

So mach limit of Mach .8 becomes a new limit of .84.

Now at sea level that is represents a 30mph increase in speed!

Now the drag reduction is proportional to cos^2<angle of sweep>

Or a 9.5% reduction in drag.....

Not a bad call on the part of Mtt to add 18 degrees sweep based off their advanced knowledge of swept wing theory. By keeping the sweep moderate, they certainly avoided all the stability and control issues found with sweep angles and engine nacelles.

Yes the center portion was adjusted to expand the forward CG limits!!!

In the transonic region, the formation of shock waves on the wing surface and the resulting separated flow (Figure 7.1) causes movement of the wing aerodynamic center.

The aft shift of the aerodynamic center is analogous to moving the airplane center-of-gravity forward.

http://www.google.com/url?sa=t&rct=j...kmfr_LD2mjThuA

After flight testing though, the original high aspect ratio wing design CG limits were not suitable for the higher mach limits the outboard sweep allowed.

As an aircraft enters transonic flight, the progression of the normal shock moves the AC rearward reducing the elevators effectiveness.
Additionally, the downwash angle behind the wing is decreased due to the seperated flow behind the normal shock. This increases the angle of attack of the horizontal stabilizer which is the main cause of mach tuck.

An airplane originally designed to have a straight wing would need to expand the forward CG limits if you are to increase the elevators effectiveness if you are going to fly in the transonic realm.

The sources you quote are correct and the sources they use were written at a time when you could count on one hand the number of United States Aereonautical Engineers who knew anything at all about swept wing theory.

Who said..

The 'reason' the outer wings were swept was to correct the cg.

yes it was...see above and it fits with swept wing theory.

The 'reason' the inner wings were swept was to correct the airflow separation.

yes it was...see above and it fits with swept wing theory.

[ACE-OF-ACES]

Originally Posted by Crumpp

They only convey a portion of the story

Well that is your opinion and your welcome to it!

But I am going to stick with the Me262 experts (Jenkins and STORMBIRDS) on this one..

Who said..

• The 'reason' the outer wings were swept was to correct the cg.

• The 'reason' the inner wings were swept was to correct the airflow separation.

It is nothing personal!

It is just when you consider the fact that Dennis Jenkins has written more aviation books than most people have read, and that the folks at STORMBIRDS surly reviewed all the data on the Me262 during the process of building reproductions of the Me262.

It would be silly to pick you over them!

But I still want to thank you for sharing your personal beliefs and opinions!

But to be honest, I really don't care about what you personally belive and your opinions!

All I care about is what can be proven.

I mean if we don't draw the line there was is to stop someone from posting in this thread that they 'belive' and are of the 'opinion' that the Germans were assisted by aliens from outer space?

So with that said I think you can understand why I drawn the line there..

I also want to thank you for information and calculations you provided!

But I am sure the likes of Dennis Jenkins and STORMBIRDS are privy to that same information/calculations and MORE and took it all into account during their research of the Me262 and their ultimate statements on the reason why the wings were swept.

Which begs the question as to why they didn't come to the same conclusions you did?

I suspect they wanted to..

In that the whole history channel 'the Germans were supermen' stuff sells these days..

Especially the folks at STORMBIRDS who are pro German tech biased..

But I suspect the stopped short of making the claims you made because they just could not find any real proof of the connections your claiming are there.

That and unlike you they have a reputation to consider!

I mean think about it, nothing would hurt their image, and thus sales, more than for them to say something they said was based on proof only to find out later there was no proof!

So with that said..

We will just have to agree to disagree as to the reasons why the wings were swept on the Me262

S!

[Crumpp]

As fro Smith/Creek, despite writing a 900 page tome on the Me262, they just pulled the CG and swept wing out of thin air.

Right!!

Why the heck would anyone think they just did it out of thin air???

Of course they did not, the Germans had 7 years of swept wing theory research and development behind them. Not only that, Mtt was a leader in the German aviation industry with swept wing designs already in flight!!

It is silly to try and make the case they did not know or consider it when they added wing sweep to the Me-262!!

Tagart said..

The 'reason' the outer wings were swept was to correct the cg.

Crumpp says: yes it was...see above and it fits with swept wing theory.

The 'reason' the inner wings were swept was to correct the airflow separation.

Crumpp says: yes it was...see above and it fits with swept wing theory.

[ACE-OF-ACES]

Originally Posted by Crumpp

Fixed that for ya!

[Crumpp]

they said was based on proof only to find out later there was no proof!

Learn about aerodynamics and aeronautical science. There are plenty of references out today on swept wing theory.

Thanks the Germans we have a good understanding of swept wing theory and we have a very detailed mathmatical model with the ability to predict behaviors.

We, meaning the world scientific community has improved upon it, but it was Germans who provided the basic foundation. framework, and direction.

Keep in mind, the United States had one scientist who was working on swept wing theory. His ideas were not accepted by the mainstream.

The United Kingdom had no one at all and their top designers thought swept wing theory was "bloody useless". Unfortunately, their swept wing pioneers were limited to toy gliders with rare exceptions pre-dating WWI.

swept wing theory was not taken up in Britain by any of the leading aircraft designers and manufacturers of the day.

http://www.aviationclassics.co.uk/ne...ing-technology

Is it surprising to anyone that the Allies had little understanding or ability to explain the German design decisions on the Me-262?

[Crumpp]

It is not my opinion Tagert. It is how it works.

Pick up a aeronautical sciences book on swept wing theory and read it.

[ACE-OF-ACES]

Originally Posted by Crumpp

It is not my opinion <snip>

Well that is your opinion on your opinion and your welcome to it!

But I am going to stick with the Me262 experts (Jenkins and STORMBIRDS) on this one..

Who said..

• The 'reason' the outer wings were swept was to correct the cg.

• The 'reason' the inner wings were swept was to correct the airflow separation.

It is nothing personal!

It is just when you consider the fact that Dennis Jenkins has written more aviation books than most people have read, and that the folks at STORMBIRDS surly reviewed all the data on the Me262 during the process of building reproductions of the Me262.

It would be silly to pick you over them!

But I still want to thank you for sharing your personal beliefs and opinions!

But to be honest, I really don't care about what you personally belive and your opinions!

All I care about is what can be proven.

I mean if we don't draw the line there was is to stop someone from posting in this thread that they 'belive' and are of the 'opinion' that the Germans were assisted by aliens from outer space?

So with that said I think you can understand why I drawn the line there..

I also want to thank you for information and calculations you provided!

But I am sure the likes of Dennis Jenkins and STORMBIRDS are privy to that same information/calculations and MORE and took it all into account during their research of the Me262 and their ultimate statements on the reason why the wings were swept.

Which begs the question as to why they didn't come to the same conclusions you did?

I suspect they wanted to..

In that the whole history channel 'the Germans were supermen' stuff sells these days..

Especially the folks at STORMBIRDS who are pro German tech biased..

But I suspect the stopped short of making the claims you made because they just could not find any real proof of the connections your claiming are there.

That and unlike you they have a reputation to consider!

I mean think about it, nothing would hurt their image, and thus sales, more than for them to say something they said was based on proof only to find out later there was no proof!

So with that said..

We will just have to agree to disagree as to the reasons why the wings were swept on the Me262

S!

[Crumpp]

Here you go Tagert,

A good simple primer on the basis of swept wing theory.

http://www.desktop.aero/appliedaero/...eeptheory.html