radiators have no influence on speed

[TomcatViP]

Originally Posted by ACE-OF-ACES

From my previous post, where I just posted the link, here Ill post the picture



Note, speed is on the bottom (x axis), it is hard to read but it looks like it goes from

(left) 520 - 530 - 540 - 550 - 560(right)

If that is the case, than the diff is only ~5kph

PS this is for a 109G not a 109E, correct me if I am wrong but they totally re-worked the rads on the later 109s models (F onward?)

So, not sure how this applies to the E if at all other than to show the rad does affect the speed a little

Yeah I saw immediatly that it was for a G (the diff being with the laminar flow absorbing device). Thx for re-posting AoAce.

You hve to understand that cooling has always been a prob in aviation. The more the speed the more the drag you get with a cooling device and the less cooling effect you hve

Here is an interesting article related to this :

Quote from user "Brian Abraham"


It would seem from the drawing that the design did not draw upon Merediths work. I'm not sure exactly how you are defining the "first with a belly scoop". To me the Hurricane would seem to fit the bill of having a belly scoop (first or not), though I don't know if it embodied Merediths drag reduction ideas as did the Spitfire and P-51.

Edited to add I came across this article written by J. Leland Atwood of North American at An engineer's perspective on the Mustang | Flight Journal | Find Articles at BNET

North American Aviation (NAA) Mustang fighter is generally credited with a 20- to 30mph speed advantage over most of its WW II contemporaries . This speed advantage also permitted a considerable increase in range that required more fuel, but not enough to significantly reduce speed. Records show that some 275 U.S. aces were "made" in P-51s. The reasons for the Mustang's significant performance capability have never been clearly explained, and I hope to clarify why its aerodynamic features enabled this capability.

To begin: in 1940, the British Purchasing Commission, which I dealt with, had a member-H.C.B. Thomas from Farnborough whom I found to be familiar with the Meredith Report. This report outlined a feature that could enhance the performance of any internal-combustion engine at high speeds by using a radiator form of heat dissipation. A low-velocity airflow through the radiator was one element of this, and it was apparent to me that the larger the radiator, the lower the speed of the air flowing through it; this approached one of the Meredith Report's objectives.

I therefore offered Mr. Thomas sketches and other descriptions of a Mustang design that had the main radiator in the rear of the fuselage. The alternatives were wing radiators such as those used on the Spitfire and the Bf 109, and under-engine radiators such the P-40's; both positions limited radiator size and the length and size of the ducting that could be used to handle and control the cooling air.

In addition to the radiator's rearward position, after the design contract had been awarded and at the recommendation of NAA's aerodynamics group, it was decided to use a new airfoil of a class generally designated as "laminar flow." This was being developed at NACA (later NASA) at Langley Field, Virginia. A 1939 report by Eastman Jacobs and others at Langley contained the results of the tests of some small laminar-flow airfoils. The drag on these small models was quite low, and there was some hope that laminar flow could be achieved much farther back on an airfoil than had been predicted by previous investigators. The publishers of the report, however, warned that they had not been able to obtain laminar flow on wings of anywhere near the size of those required for actual aircraft and that their tests were to be taken only as the results from laminar-flow models of not more than six inches in width.

In spite of this warning, however, both Ed Horkey (leading aerodynamicist at North American) and Bell Aircraft's chief engineer, Robert Woods, decided to try laminar-flow profiles on the P-51 and the Bell P-63, respectively. These airfoils were incorporated on the Mustang and the Bell airplane with the hope that laminar flow could be extended well back on their wings. Extensive efforts were made to polish and protect the P-63 wing's leading edge profile, but the results were equivocal. Those who advocated the laminar flow wing felt that the Mustang's outstanding performance resulted from laminar flow over most of the wing. Kingcobra designers felt they were getting a similar effect, although that aircraft's performance did not justify this conclusion.

With respect to the Mustang, many tests-including some in recent years-have shown that extensive laminar flow was not developed on the Mustang wing and that the drag of the wing was probably no less than that of conventional wings of the same thickness and taper ratio. On the other hand, the Mustang's cooling drag was much lower. This was the result of using a ducted radiator with a large area and a slow-speed airflow through it (Pr and P2); closing up the exit and creating a back pressure restored the momentum of the cooling of air (momentum lost in radiator transit). This was possible because of the radiator's cooling capability, which, to be adequate in a full-power climb, was much more than that required at high speed and high dynamic pressure. According to calculations given in a supporting paper, the drag created by momentum loss in passing through the radiator can be reduced from some 400 pounds to close to 30 to 40 pounds because of the offsetting momentum of the jet thrust from the radiator exit (V2).

Since these two effects, i.e., the wing drag and the radiator momentum recovery, have never been disentangled in the literature, a technical reason for the Mustang's performance has never been clearly identified.

NACA had taken the lead in airfoil development and had worked out a large series of airfoils that were used generally throughout the industry. For instance, the Spitfire wing was of the NACA 2200 series-13 percent thick at the root and 6 percent thick at the tip. This is the same airfoil series as is used on the DC-2 and the original North American BT-9 and AT-6 trainers. To improve the stall characteristics, I later changed the NACA 2200 series on the AT-6 trainer to the 4412 at the tip. It is quite probable that the Spitfire's wing, being only 6 percent thick at the tip, had a lower drag than the Mustang's wing as actually incorporated.

The point of all this is that nearly all WW II fighters operated at Mach numbers of .65 or less. The primary advantage presented by the so-called laminar-flow wing was therefore not in drag reduction but in high-speed dives, where temporary airspeed shock waves were created on the wing's upper surfaces and a loss of control and lift occurred as the critical Mach number was exceeded. This was a phenomenon we called "compressibility," and it became the subject of a huge amount of research. The Mustang pilot, with his laminarflow wing, had a higher critical Mach number, so he could point the nose down and know he could out-dive virtually any airplane and recover relatively easily. The P47 and P-38, however, with their older, fatter wings would hit compressibility and have to use their dive flaps to recover safely. So, besides being an overall clean design, the legendary Mustang's speed and range rest as much on carefully designed radiator airflow as on anything else. As is often the case in aircraft design, it was the seemingly small details that counted.

It's not completely true in every line but it's in concordance with what we have to know.

(extracted from here : http://www.pprune.org/aviation-histo...first-one.html)

Pls note that the 109 had far more cooling power than the Spit wld get in all models. If you look at the 110 rads, you'll understand that the 109 was made for sustaining max power far more longer than any other warplane at the time in Eu. There is no secret, it's only tweaking

[ACE-OF-ACES]

Originally Posted by TomcatViP

Yeah I saw immediatly that it was for a G (the diff being with the laminar flow absorbing device). Thx for re-posting AoAce.

No prob!

Originally Posted by TomcatViP

You hve to understand that cooling has always been a prob in aviation. The more the speed the more the drag you get with a cooling device and the less cooling effect you have

Oh I understand that, have for years

What I don't understand is how guys like David can come here and make baseless claims.. Such that he had no idea how much the speed should be affected.. but did that stop him from making the claim? Nope! Now that we have some numbers to get a feel for the affect.. I get a good laugh at David's expence that he 'thinks' he can detect an 11kph difference that he didnt even know as 11kph until I provided him the data.

[David198502]

you still dont know that its 50kph difference and not 11...man im getting tired arguing with you...

and even if it was only a difference of 11kph, why shouldnt one be able to detect it???

[TomcatViP]

C'mon guys there was enough blood wasted at the time those events took place. No need for anymore shredding here

[David198502]

Originally Posted by TomcatViP

C'mon guys there was enough blood wasted at the time those events took place. No need for anymore shredding here

+1

sorry ace if i upset you...that surely wasnt my intention with this thread

[ACE-OF-ACES]

Originally Posted by David198502

you still don't know that its 50kph difference and not 11...man im getting tired arguing with you...

I think we are talking about two different things.. I am saying the difference in the two graphs is a constant ~11kph

Originally Posted by David198502

and even if it was only a difference of 11kph, why shouldn't one be able to detect it???

You can, but not with the naked eye! You would have to log the data, so you can take into account the variations of flight, because the fact of the mater is the speed vary as you fly due to you making small altitude changes.. That is to say YOU ARE NOT CAPABLE OF MAINTAIN A PERFECT ALTITUDE !!! But don't feel bad most cant! Thus the variations in speed due to altitude changes are on the order of 30-40kph. So, the 11kph falls within that range, thus you can not desern which is which unless you also plot altitude

[David198502]

Originally Posted by ACE-OF-ACES

I think we are talking about two different things.. I am saying the difference in the two graphs is a constant ~11kph


You can, but not with the naked eye! You would have to log the data, so you can take into account the variations of flight, because the fact of the mater is the speed vary as you fly due to you making small altitude changes.. That is to say YOU ARE NOT CAPABLE OF MAINTAIN A PERFECT ALTITUDE !!! But don't feel bad most cant! Thus the variations in speed due to altitude changes are on the order of 30-40kph. So, the 11kph falls within that range, thus you can not desern which is which unless you also plot altitude

yes but these constant 11kph is the DIFFERENCE BETWEEN THE DB601 and DB605 engine!

Now I would like to know if someone has made tests:
Full throttle, optimal rpm

what are the durations before ruining the engines depending on rad setting.

100% open, 95%, 90% ...

[ACE-OF-ACES]

Originally Posted by 41Sqn_Stormcrow

Now I would like to know if someone has made tests:
Full throttle, optimal rpm

what are the durations before ruining the engines depending on rad setting.

100% open, 95%, 90% ...

Bingo!

And with that said providing a track file is the min requirement to be taken seriously..

And log the data as you fly and record that track file if you really want to do a good job!

In IL-2 you could replay the track file and extract and log the data at a later date..

But I don't think you can do that in CoD! I am pretty sure you have to log the data as you fly the mission!

[ACE-OF-ACES]

Originally Posted by David198502

yes but these constant 11kph is the DIFFERENCE BETWEEN THE DB601 and DB605 engine!

Still as I noted the speed can varry by 30-40kph due to altitude changes.. Assuming you can hold it pretty steady, more if you cant! So your 50 would/could still be in the noise. The only way to tell is to log the speed and the altidue, than you can 'see' what is going on