Allied tests of captured Bf-109's (1 Viewer)

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Intersting report - not specifically tagged to the 109 but in comparing 51 to fw 190D and Spitfire on Drag.

The total drag coefficients predicted by Lednicer's model is in very close agreement (and the same between the P51B and D) with wind tunnel tests.

This seems true despite the fact that the P-51D has a greater 'wetted area' than the P-51B. The 190D is closest to 51 in total wetted Drag but I haven't found an equivalent study on the 109.

The primary reason for better Bubble vs Birdcage or malcolm/blown hood' seems to be 1.) the better flow characteristics over the bubble top than the Bird cage canopy

This discussion and model would yield a nice comparison to the contrast between the 109 and the 51, particularly in predicting rate of energy loss in a manuevering fight.

Make your own judgements.

I like the model and the assumptions they made to set it up and the explanations for the variances. The 'singularities' used to simulate the finite element distribution of flow are source/sink pairs to create the 'circulation' and then they have to do iterations to introduce boundary layer growth to point of 'positive' pressure creating separation (and 'no lift') and resultant profile drag.
 

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Thanks Soren, we needed an expert opinion on this.
I stand corrected. :)
There's quite a few sources that mention springs, but heres a hobby site with some good diagrams.

basepage
I looked at them today and there are no springs it appears to me they work on airpressure from the airflow they can be pushed in and out with one finger , but it was once stated that they got jammed up by dirt ,sounds like poor maintainence to me as there as there is very little airborne dirt
 
I looked at them today and there are no springs it appears to me they work on airpressure from the airflow they can be pushed in and out with one finger , but it was once stated that they got jammed up by dirt ,sounds like poor maintainence to me as there as there is very little airborne dirt

Pb - I believe you are right. The one at the Smithsonian has no springs. The more I think about it there is no reason for it... the reduction in dynamic pressure as the wing in the slat region start to get separated flow in that area , the condition of lower freestream pressure on the nose of the slat than behind it - ought to 'actuate' the slats I would think.

From a design point I would be concerned about a spring jamming or otherwise artificially holding one slot open but not the other?

I suspect the jamming would be caused by getting 'crud' on the rail/slot interface (but I do not know this to be true)
 
Call it suction or seperation, it's the same and it creates drag and this is the prime reason for the P-51B being faster than the P-51D, as-well as the dive speed issues.

The reason the P-51H is so much faster than the P-51 is not only because of the much more power available (It ran at 90" Hg) but also the different wing.

A little off topic, but did the F-86's LE slats use the same mechanism? (It would make sence since the Me 262, and HG variants, had alot of influence on the Sabre iirc)

Yes exactly the same, but the F-86 pilot was also given the option of locking them in place incase of a jam or other mechanical issues, otherwise they operated just the same.
 
Guys as already explained the LE edge slats operate by means of airpressure alone (There are no springs what'so'ever), extending as the pressure on the top of the wing decreases while the AoA increases. Thus the speed of the deployment is completely dependant on how quick the increase in AoA is, so if it's slow and gradual than so is the deployment, and if it's fast and gradual then so is the deployment.

It is therefore that automatic LE slats are AoA dependant devices.
 
Call it suction or seperation, it's the same and it creates drag and this is the prime reason for the P-51B being faster than the P-51D, as-well as the dive speed issues.

No, Soren - and no.

In the model 'suction' is a lower pressure than the freestream dynamic pressure.

The nature of a singularity distribution across finite element 'surfaces' in the model generate 'increased' flow across the top surface in accordance to wind tunnel flow results obtained chord wise on the airfoil at that wing station..until the 'iterative modelled' increase in boundary layer results in a local 'positive' pressure gradient from one model element upstream from the next one considered.

Isn't that your understanding?

Others tend to call it 'lift' in the real world. Separated areas are the 'non red' areas in the model. It should be intuituve Soren? Are you suggesting that the 'red' regions in Lednicer's model is 'separated' flow and that the rest is 'lift??

And yes, Lift creates drag but that drag manifests itself as induced drag due to the energy loss due to the tip vortex... not across the top of the wing where laminar flow/small boundary layer exists (or in the case of the 51D canopy - where flow has not yet gone 'positive' relative to freestream. Those drag elements are described as Profile or Wake drag and are represented in his tables. I don't recall seeing a friction drag component, but neither 51 would have much and both should be less than the Spit IX and Fw 190D if the distribution of flush rivets, and surface finish of a 51 is any indication.

From Lednicer's comparisons between the 51D and the 51B, it seem intuitive to me that one of the factors that kept the 51D at the same total drag coefficient was the improved (delayed) separation over the canopy..

what is your interpretation?

and if you don't like the Lednicer Comparison and tables - the same model results that you used to demonstrate your knowledge of 'flat plate' drag a month back in our Fw 190D vs Fw 190A 'disappointment' debate - why did you use it?

Dive speed issues? The 51D added a strake to the rudder to compensate for the loss of turtleback 'stabilizer', and added uplock kits to the landing gear doors and thickened/stiffened the ammo doors to improve some issues experienced in the B.

IIRC there is a pretty good report on the visible effects of the ammo doors Beginning to locally distort at near .85 mach in Mike Williams Website - but that was past recommended Max dive speed by some 40 mph TAS. I admit I was suprised that a dive was ever made at .85 for sanity reasons but apparently it was done under controlled conditions.

The wetted drag is the same for both 51B and 51A ships... so make your case that weight was or was not the key factor when a.) drag same, b. P-51D weighed approximately 600 pounds more, and the P-51D had a more powerful engine (at lower altitudes than 25,000 feet)


The reason the P-51H is so much faster than the P-51 is not only because of the much more power available (It ran at 90" Hg) but also the different wing.

And your proof that the 51H wing was more efficient is to be found where?There IS a slight difference in both the plan form and the airfoil itself, but I assume you have wind tunnel results or model results to justify your statement? I don't so would love to see them

Yes exactly the same, but the F-86 pilot was also given the option of locking them in place incase of a jam or other mechanical issues, otherwise they operated just the same.

The 51H is also 'so much faster' than the P-51B. Hp makes a difference, weight reduction made more of a difference in my opinion... prove otherwise?
 
Guys as already explained the LE edge slats operate by means of airpressure alone (There are no springs what'so'ever), extending as the pressure on the top of the wing decreases while the AoA increases. Thus the speed of the deployment is completely dependant on how quick the increase in AoA is, so if it's slow and gradual than so is the deployment, and if it's fast and gradual then so is the deployment.

It is therefore that automatic LE slats are AoA dependant devices.

Soren, you may not have the notion of pressure distribution, causes of boundary layer separation and stall, quite clear.

Briefly - before getting to Slat 'physics' and pressure conditions causing them to deploy as brief summary of Principle of Flight.

What causes 'lift' is essentially bernoulli's principle. Faster flow DECREASES local pressure relative to the freestream passing over a tube. It is the same principle as flow travels up and over the top and bottom surface of the airfoil from the relative Zero angle of attack. Nature wants desparately for the flow stream elements to arrive at the trailing edge at the same time.

Conceptually, the point at which the freestream separates into 'top' and 'bottom' flow is called a stagnation point on the leading edge.

As the AoA increases from Zero Lift Angle of Attack, the velocity over the top surface must travel faster to reach the trailing edge than the flow over the bottom surface.

This results in the LOWER relative pressure (to Freestream) on the bottom of the wing and EVEN LOWER relative pressure on the top surface of the airfoil. ece between the Lower pressure on the bottom and the Even Lower Pressure on the top is usually called a Pressure Differential.

If one is flying inverted, one wants the airflow AoA to be Below the reference Zero AoA, so that the airflow on what used to be the bottom surface of the airfoil is now faster than the flow on what used to be top surface... otherwise there is contact with a solid surface.

People call this Pressure Differential 'suction', with a positive vector UP normal to plane of the wing in the case of Lednicer's model, and Lift to aerodynamicists.

When the AoA reaches the region called CLmax, the energy of the flow for that wing has a critical point where the boundary layer is not 'attached' and has grown to point where the local pressure behind the boundary layer is HIGHER than the flow in front. As the AoA moves a little more there is an onset of turbulent flow which has more energy than the laminar flow in front. When that region of turbulent flow reduces the area of Suction/Lift to point where the resultant positive force is adequate to sustain level flight and velocity, or local flow over control surfaces like ailerons, we now have a condition some people call 'STALL'.

Now for the So, what?

Now, those wonderful inventions called Slats are locally affected as the laminar flow behind it are disrupted to point where the local Lift/Suction still exists on the top surface of the Slat, but not behind it, and it deploys- having the effect of letting the freestream air which now has more energy than the stalled region, flow under the slat and thence to the leading edge of the wing and beyond, restoring boundary layer flow, sorting out chaos in the turbulent area, and restoring lift in that area.

At the point where the slat deploys, the pressure distribution behind and then to the slat have become relatively 'positive' with respect to pressure distribution over the Slat

Regards,
 
Oh when it comes to the issue of pressure distribution and boundary layer seperation I see things quite clearly Bill, and nothing of what I explained is wrong, nothing.

The slats start to deploy at very low AoA's as the pressure on the top of the wing becomes lower than the pressure under the wing, making the slats extend. Quite simple.

Moving on..

I trust Lednicer very much, no doubt about it, and here's his words exactly:

2006050085672843414_rs.jpg


Stronger suction = more drag. Very simple Bill, no need to complicate it.

And furthermore from the very same article:

2006028415181748090_rs.jpg


Again like I said, the P-51B features less drag than the P-51D, and primarily because of the bubble canopy. A bubble canopy creates more drag than the razor back configuration, that's a common known fact Bill, deal with it.

And as for the P-51H's wing, it's slightly smaller = less drag (Decreased Root chord) and there's plenty more power available to the a/c, hence the higher speed.


As for the dive issues, well because of the bubble canopy and cut down aft fuselage the D series suffered from directional instability, something which was shared by the P-47's featuring bubble canopy's as-well. This is the cause for adding the dorsal fins.
 
Oh when it comes to the issue of pressure distribution and boundary layer seperation I see things quite clearly Bill.

And I trust Lednicer very much on this as-well, no doubt about it, and here's his words exactly:

2006050085672843414_rs.jpg


Stronger suction = more drag. Very simple Bill, no need to complicate it.

Not complicated at all.

It is clear that you may not understand either the model or the results. It is more clear that you may not fully have the principles of Fluid Mechanics, and extended further, the theoretical tools of Aerodynamics..

Can you explain the theory behind the use of 'singularities' as he has used them to model the pressure distribution? and why that is a valid model approach?

You should also attempt to put that paragraph in context as other may see by looking at the entire article. For those that care - look to the comments Lednicer makes regarding the poor canopy design of the Spitfire and contrasts it with the P-51D and look at the relative 'suction' distribution over both canopies


And furthermore from the very same article:

2006028415181748090_rs.jpg


Again like I said, the P-51B features less drag than the P-51D, and primarily because of the bubble canopy. A bubble canopy creates more drag than the razor back configuration, that's a common known fact Bill, deal with it.

Words like 'commonly known facts', 'far superior' etc are what occasionally cause issues with us Soren.

If you refer to Gene's Lednicer's models and report your interpretation as 'the commonly known facts', then you have mis interpreted the both analysis and the conclusions - he draws exactly the opposite conculsion in Table II/Section VII of the P-51B vs P-51D report.. and explains that the results do not include the 'scoop'..In other words the Table II results include canopy difference, etc but not the oil cooler and radiator intake fairing. As I will repeat below his model resulted in .0033 for P-51B and .0031 for P-51D as the respected wetted Drag Coefficients.

The Table you chose to show was the roll up including friction drag, induced drag and profile drag. The numbers on the left of your table are the SUM of the flat plate equivalents of Friction/Wake/Induced streamwise components of force.

If the 51D has greater area and same wing can we conclude that the factual flat plate equivalent of friction drag is greater and the induced drag is the same? But the wetted drag coefficient is exactly the same for all drag components? would you conclude that the profile drag (including canopy, boundary layer/wake drag) is Slightly Higher for the P-51B than the D?

I would. An that is what Lednicer was showing with 'suction' on the canopy as boundary layer attached region.. i.e Not Separated creating additional wake drag.

Is there another source that would better serve the 'phrase 'commonly known fact'?


Do you care to present the rest of the tables showing the wind tunnel comparisons, and the past theoretical calculations between the two ships, and his words Soren, and note that the Total Coefficient of Wetted Drag is the same in that table which is extracted from his model? When you have presented your past 'models' using drag - did you use 'flat plate drag' or Total Drag Coefficient.

And as for the P-51H's wing, it's slightly smaller = less drag (Decreased Root chord) and there's plenty more power available to the a/c, hence the higher speed.

So far I find 235 sq ft for all variants even though the leading edge 'strake' was completely removed. Your source for less wing area is?



As for the dive issues, well because of the bubble canopy and cut down aft fuselage the D series suffered from directional instability, something which was shared by the P-47's featuring bubble canopy's as-well. This is the cause for adding the dorsal fins.

I think I mentioned the reason for the strake and the other mods that made first the P-51D safer than the B, and then the H much safer than the B in dive. Your point is what?

As to 'directional instability' that would be an incorrect overstatement also.

Correct would be 'slightly less yaw stability' between the two at top dive The pitch stability was the same for the same speeds. Yaw stability slightly favored the P-51B until the changes were applied to the D (and H).

ALL Mustangs exibited tendency to pull right as Mach number increased The P-51D apparently had a higher safe dive speed over the B when the modifications were applied (including metal elevators, increased rudder spar strength at fuselage attach points, improved ammo door stiffness, wheel door uplocks

Here is the RAF Dive tests performed without metal elevator modification, in which the a/c was dived up to .85 Mach

Note on Dive Tests on 'Mustang IV'

You still think 'suction' is drag in Lednicer's model? Would you care to educate all of us on the Graphical representation of the pressure distribution by 'color' and interpretation'? I would be interested in learning why I don't understand what he is saying.

And perhaps explain why he doesn't know what he is talking about when he describes the Drag term as 'Stream wise components' versus what I think you are describing ('suction' which is a normal component) as drag?


As to difference in predicted CDwetted between the models, I draw your attention to page 8, Section VII, Table II and the explanation below by Lednicer (for context).

According to VSAERO model, CDw for P-51B = .0033, P-51D = .0031 for the model condition I just described from his report. Which of these two numbers would you rather have?
 
This is ridiculous Bill,

Are you claiming that bubble canopies don't increase drag over the razor back configuration or not ? I need you to answer that question specifically.

Lednicer's graphs does indeed show a similar CDwet for both a/c, but that doesn't mean that the bubble canopy doesn't provide any additional drag over the razorback configuration, esp. seeing there were other design changes between both a/c. In short a stronger suction means more drag Bill, it's that simple really.

And as for the British tests, well why use them and not the US ones ?? If I wanted to compare the P-51B D I'd use data from its country of origin, i.e. the same place, leaves out many possible discrepancies.

But since you don't want to realize any of the above I guess it'll take a vet P-51 pilot to convince you;

Robert C. Curtis, American P-51 pilot:
"The P 51 was redlined at 505 mph, meaning that this speed should not be exceeded. But when chasing 109s or 190s in a dive from 25-26,000 it often was exceeded, if you wanted to keep up with those enemy planes. The P 51b, and c, could stay with those planes in a dive. The P 51d had a thicker wing and a bubble canopy which changed the airflow and brought on compressibility at lower speeds."
 
This is ridiculous Bill,

Are you claiming that bubble canopies don't increase drag over the razor back configuration or not ? I need you to answer that question specifically.

Yes.

I am claiming that in Lednicer's reports, the Model, and cases to compare the bubble canopy of the P-51D,to the birdcage canopy version P-51B, the malcolm hood Spitfire IX and the blown hood Fw 190D - in the common report you and I both have and for which I have posted in their entirety (and you have not) he CLEARLY demonstrates the greater Suction (normal force), and hence LOWER pressure drag (horizontal force in streamwise direction.


Lednicer's graphs does indeed show a similar CDwet for both a/c, but that doesn't mean that the bubble canopy doesn't provide any additional drag over the razorback configuration, esp. seeing there were other design changes between both a/c. In short a stronger suction means more drag Bill, it's that simple really.

Specifically Suction is a Normal Force (i.e Perpendicular to the modelled surface) and Drag is a Streamwise Force (or Parallel force to the modelled surface in the stream/flow direction. To go any further you have to understand the difference. Do you?

If you understand Vectors you should understand. Where are we on that? In Vector terminology these two forces are Orthogonal (perpendicular) to each other and most specifically are Not the same in either direction or magnitude


Specifically Soren, he shows a LOWER CDwet for the 51D sans lower faired radiator/oil cooler structure - and EXACTLY the same CDwet for the TOTAL components of Friction, Pressure/Form/Wake (whatever term you want), and Induced Drag for the two airplanes. You seem to be equivocating and obscuring what he wrote when you say 'similar'

And as for the British tests, well why use them and not the US ones ?? If I wanted to compare the P-51B D I'd use data from its country of origin, i.e. the same place, leaves out many possible discrepancies.

I used it only to show the only reported and controlled test that measured a velocity of .85Mach for ANY version of a Mustang - to help you understand visual observations during the course of the controlled tests. I have the results of the terminal tests performed by NAA on the P-51B in which it reached .75 Mach without prop (and prop drag) in controlled tests. That is not the limit speed of a 51B but I haven't yet seen a similar test to ultimate in a controlled test - have you

But since you don't want to realize any of the above I guess it'll take a vet P-51 pilot to convince you;

Why introduce a component of sarcasm - I will keep my comments objective and relevant. I was under the impression that we were debating the Lednicer models, reports and conclusions relative to drag.

Robert C. Curtis, American P-51 pilot:
"The P 51 was redlined at 505 mph, meaning that this speed should not be exceeded. But when chasing 109s or 190s in a dive from 25-26,000 it often was exceeded, if you wanted to keep up with those enemy planes. The P 51b, and c, could stay with those planes in a dive. The P 51d had a thicker wing and a bubble canopy which changed the airflow and brought on compressibility at lower speeds."

He must have been flying a different Mustang from what he thought he was flying. Actually both were redlined at 505mph TAS and both often exceeded 505, in some documented cases past 550mph.. but he is wrong about the wing. Are we at the point you want to change the subject to anecdotal discussion or - do we stick to your understanding of Lednicer model and results?

The P-51D wing is only different by having a longer Root chord at the Cl which results in the greater 'sweep' of the leading edge of the section inboard of the guns. Same primary airfoils, same tip airfoils, same specs on area and wingspan, etc. Even though the specs indicate same wing area as for the B, I would suspect the D has slightly greater wing area... very slightly

the set tail incidence is slightly different, the only material change was the elimination of the birdcage canopy and the turtledeck behind it and replace with streamlined teardrop canopy, adding two extra .50 cal guns plus ammo and some additional structure in tail spar fitting, wheel uplock kits and a slightly larger fuselage fuel tank.

In other words, the differences in surface area (for friction drag calcs) was the very small increase of the inboard leading edge in front of wheel well and a very small decrease in the surface area behind the canopy. In other words some of the wing surface increase was offset by lowering the deck aft of the canopy... somewhere the 51D gained about 4 sq ft. Every other material change was the incremental weight and the difference in aero dynamics of the canopy.

Now to the analytical part.

Surface area on P-51D slightly greater. Would you assume the friction drag was slightly greater? I would

The Induced Drag of the P-51D due to extra weight for the same speed would be greater with the same wing? Yes?

That leaves us with Form Drag/Wake Drag. Correct? Two increase over the P-51B, leaving us with one last component.

If the P-51D was the same shape, same wing span, same airfoil, same length, tail, elevator, engine cowling, lines, lower radiator fairing, etc - except the Birdcage canopy/turtledeck vs the tear drop canopy. Right?

So, two of the three components of Drag (not 'suction') of the 51D are greater than the 51B - yes? And neither relate to the canopy shape.

But the TOTAL CDwet of the two airframes are Exactly the same.

What does the math then say about the Profile Drag of the B? It says to me that the Profile drag of the 51D is LESS than the 51B. Says so in Lednicer's Table II and his write up.

It says to me that flow around the P-51D canopy remains laminar almost to back of canopy as Lednicer shows. It says that the flow separates on a P-51B and the Spitfire IX right on the top area of the forward windscreen. What does it 'say' to you?

Lednicer's model demonstrates this as well as presents the differences in tables.

So, If you agree with everything he says, as you said earlier, how do you rationalize 'suction' with drag - or describe the 'suction' in the model as a streamwise force vs Vertical?
 
Oh when it comes to the issue of pressure distribution and boundary layer seperation I see things quite clearly Bill, and nothing of what I explained is wrong, nothing.

The slats start to deploy at very low AoA's as the pressure on the top of the wing becomes lower than the pressure under the wing, making the slats extend. Quite simple.

Forgot to touch on this.

Your thesis is that somewhere close to level flight, in all regions of the flight profile, at the above described 'low AoA', that the Me 109 slats deploy?

That Must have been very annoying. particularly on a routine climb to altitude or final approach at any speed.

Further such sensitivity to low AoA must have created very annoying asymetrical forces like a gentle turn when the upwing slat opened as it's local relative AoA gained slightly over the AoA for the lower wing. You know the induced drag, and hence the local AoA, is greater for the upwing?

Why would Messerschmidt design team do that? Most other design teams want, and only want the slats to deploy at stall in that local area - just to prevent them from suprising pilots in ordinary flight envelope.
 
It would be interesting to see Soren actually respond to all the questions u've put in ur posts Bill....

I too feel that he is not interpreting some of the issues brought up in the report correctly, and would really like to see him, in his words, answer some of the insights u have about the Lednicer Report...

I cant really understand how one extremely intelligent person can interpet a set of facts completely different from another extremely intelligent person...

This is a very interesting discussion, way beyond my grasp on several levels, but learning new stuff is always a treat... But honestly, Im confused at the discrepancies between u two guys...
 
It would be interesting to see Soren actually respond to all the questions u've put in ur posts Bill....

I too feel that he is not interpreting some of the issues brought up in the report correctly, and would really like to see him, in his words, answer some of the insights u have about the Lednicer Report...

I cant really understand how one extremely intelligent person can interpet a set of facts completely different from another extremely intelligent person...

This is a very interesting discussion, way beyond my grasp on several levels, but learning new stuff is always a treat... But honestly, Im confused at the discrepancies between u two guys...

Dan - I can't really explain the difference in opinions regarding Lednicer's analysis and his conclusions. Those are hard to overlook per se... but

If Soren believes the 'suction' term that Ledicer uses is either a drag component or somehow related to induced drag due to lift, it would explain his perception and follow on arguments. Lednicer makes it clear that all drag in the dicussion are the forces in the streamwise direction - I think he used 170 stream tubes which would be roughly one every 2/10 foot on a 35 ft wingspan.

The stream tube does not permit spanwise flow, only chord wise parallel to a/c axis.

The reason I was delighted that Gene (Crumpp) sent me these reports is that this is the kind of 'stuff' I was doing when I first entered the airframe industry and went from aero models using finite element/rigid structures, then to finite element/elastic structures, then on to pure Structural models when I went to Bell.

Lednicer's VSAERO application seems more sophisticated in the context of building in boundary layer and thence to separation conditions.. I know the theory but it was beyond my then current ability to 'model' the iterative process to get reasonable correlation.. and everybody else's in 1968-1969.

But the distribution of singularities in each of the panels it was exactly the same approach.

Having said all this, the experience in the airframe industry in which manuever performance had to consider this type model plus consider aeroelasticity, stability and control parameters, thrust in asymetric flight etc.. make me smile when I see the discussion come to 'simple physics'.. and I repeat - I am an amateur.. the degrees and the industry experience I have scratched the surface - but I know what I don't know.

I suspect there will not be direct answers to the questions but I would like that kind of discussion on both the Lednicer model and cause/effect on slat deployment.

Good to chat - I've about drained the swamp on this discussion. I'm gonna get up and scrtach some ears.

Say, how do I engage (and with whom) the loading of the 5-7 mb portraits of 30 + 355th side elevations for my book. Steve Daisley is a pretty good little artist and perfect for my book

Regards,

Bill
 
I would just start a new thread and start adding the pics Bill... Make a disclaimer in the Thread Title **56k NO WAY** or something like that... Its gonna take awhile to upload em that way, but damn they'll be pretty for anyone willing to wait for them to load....

Or......

U could try and email me a few at a time due to mailbox size, I'll shrink em down to a more manageable size, and email u for more.... In a few days, we could get em all done...
 
I would just start a new thread and start adding the pics Bill... Make a disclaimer in the Thread Title **56k NO WAY** or something like that... Its gonna take awhile to upload em that way, but damn they'll be pretty for anyone willing to wait for them to load....

Or......

U could try and email me a few at a time due to mailbox size, I'll shrink em down to a more manageable size, and email u for more.... In a few days, we could get em all done...

just sent you a PM
 
The suction issue was braught over from "Best Piston Engined Fighter Ever
"
...

I'm not sure that was intentional, but oh well.


I think some of the confusion is coming from interpretaion of terminology. (though most of this, particularly the specifics, is over my head)



Maybe this will help to bridge the canopy issue: How does the Malcolm hood P-51B/C compare to the "birdcage" or teardrop/bubble canopy?
 
The suction issue was braught over from "Best Piston Engined Fighter Ever
"
...

I'm not sure that was intentional, but oh well.


I think some of the confusion is coming from interpretaion of terminology. (though most of this, particularly the specifics, is over my head)



Maybe this will help to bridge the canopy issue: How does the Malcolm hood P-51B/C compare to the "birdcage" or teardrop/bubble canopy?

Good question. It didn't seem to help per se in the lednicer model but he made a specific comment that the Spit IX wind screen had a larger angle from the P-51 D and suspected that was more of a problem than the geometry aft of that.. in other words separation high on thr windscreen in his model. Go back and look at the reports I posted and see if he amplifies
 
Ok fair enough Bill, I apologize for the sarcasm then. And let's be objective about this.

About the slats first;

My thesis is not and has never been that the slats deploy fully in conditions close to straight flight, and I honestly can't really understand how you interpret it that way either. Also I don't bring forth any thesis on this subject only the facts.

You need to understand that the slat deployment process is gradual, the slats starting to deploy at a very low AoA's, not fully extending ofcourse, but extending out slightly. And so in climbs, landing approaches and slow turns a pilot wont even notice the slats popping out unless he looks at them as the deployment process is so slow and the slats themselves not fully extended. However if the pilot banks hard where the Critical AoA of the original airfoil is reached nearly instantly, then he will feel a very slight notch on the stick as the slats pop out to their fully deployed position almost instantly.

Furtermore the slats aren't linked together, they're completely independant of each other, and thus so is the deployment process. So if one wing is starting to stall before the other then the slat on that wing is also further extended.

As Mark Hanna puts it:
"As the stall is reached, the leading-edge slats deploy-together, if the ball is in the middle and slightly asymmetrically, if you have any slip on."


Anyway got get back to work now, will address the rest later.

PS: Glad we can discuss this in a calm objective manner Bill.
 

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