Some opinion about maneuverability of Bf109K-4

I meant slats effect that was documented in WT report.

what report do you meant? ...War Time or WarThunder??

What kind of reports have you taken to model the Bf-109K4?

what report do you meant? ...War Time or WarThunder??

 

What kind of reports have you taken to model the Bf-109K4?

Ehm... Wind Tunnel?

I really want to see war time wind tunnel test report about Bf109K-4. Where I can find that report?

Considering this is being run on a home PC for less than $40 for the program and airplane, how fantastic is it that we have a simulation so accurate that people are "straining at a nat" over the miniscule differences between real aircraft and our simulated version.

Wow!

I wonder the exact reason behind rounding the wingtips on the 109F-K - was it for reduction of drag (like winglets on modern airliners)?

Considering this is being run on a home PC for less than $40 for the program and airplane, how fantastic is it that we have a simulation so accurate that people are "straining at a nat" over the miniscule differences between real aircraft and our simulated version.

Wow!

There is no end of greed to people and it is the mainspring of advancement I think.

In turn fight, if P-51D and Bf109K-4 engage at more than 500kph, P-51D can get some advantage cause stiff stick force of Bf109, but in sustain turn more power mean deose not mean more high speed. It means more power loading in turning performance. Limit power or not Bf109 have better factors in turning performance than P-51D.

One of the things you're overlooking: more power means better E retention, i.e. the fighters won't fall to their sustained turn speeds as quickly, i.e. they can stay at corner turning speed for longer. Higher turn speeds are the P-51's preferred area, yes? So, this is one of the reasons why reduced power hurts the the P-51 more than reduced power hurts the Me 109; the 109 pilot is fine with both birds getting down to best climb / sustained turn speeds quickly, while the P-51 pilot would prefer both birds to stay fast, at corner or higher (where the 109's control stiffening is an issue). In other words: less power for both ships means the fight can't remain a high-speed fight for as long, which works in the 109's favor, since the 109 is more comfortable at slow speed fighting than the P-51 is. Yeah?

There are other things you're overlooking (not even getting into all of the other factors! e.g. hp. /= thrust, 'coz prop efficiencies); I'm having a difficult time trying to put them into words, even without worrying about language barriers, so I'm gonna leave that for someone more familiar with aerodynamics & language than you & I are.

Yo-Yo, do you mean like the DCS:Bf-109K4 or a Bf-109 aircraft in RL??

 

In this drawing of a Bf-109K4 you can see that the wing area, affected by the slats airstream is nearly to 40% of the total wing area.

 

Yo-Yo, 40% of the total wing area is a "small part"for you??:music_whistling:

The problem with this illustrarion is that it greatly exaggerates the effect of the slats on Cl max for the Bf 109. Known full-scale wind tunnel measurements on Bf 109 V24 point to very small or no gain at all (From Mtt AG Technical Report 94/43):

The slats' main goal was to provide a relatively undisturbed airflow to retain enough aileron control up to complete stall of the wing (condition 4 of the following sketch):

I wonder the exact reason behind rounding the wingtips on the 109F-K - was it for reduction of drag (like winglets on modern airliners)?

Jepp, I guess it is the same reason the F series received the rounding. It is a design compromise between production and design. Basically an elliptical wing is the perfect wing planform to minimize induced drag, but it is much more difficult to produce. The Spitfire has an almost perfect wing in this regard, but the production problems in the beginning delayed the total output considerably, as far as I remember.

The problem with this illustrarion is that it greatly exaggerates the effect of the slats on Cl max for the Bf 109. Known full-scale wind tunnel measurements on Bf 109 V24 point to very small or no gain at all (From Mtt AG Technical Report 94/43):

 

The slats' main goal was to provide a relatively undisturbed airflow to retain enough aileron control up to complete stall of the wing (condition 4 of the following sketch):

 

 

 

 

If I am not misinformed, the BF-109 V-24 (VK+AB) was a pre-production prototype of Bf-109F with clipped wings as Bf-109E.

As a result of the tests in the wind tunnel, the effect "aileron drops" of "Emil" series was removed, but the automatic slats were not eliminated.

When the slats are deployed drag is increased, .. if the Slats would not increased the CL properly, surely the Dr.Eng. Willy Messerschmitt would have eliminated the slats without hesitation from the biginning.

I think my illustration is not exaggerated, because it is very similar to the areas of influence of the slats marked on the sketch you've shared from the report of Bf-109G6 of 1944.

Please, If you want, share the full report of that Bf-109G6 from 1944, so we can see what final results are reporting.

One of the things you're overlooking: more power means better E retention, i.e. the fighters won't fall to their sustained turn speeds as quickly, i.e. they can stay at corner turning speed for longer. Higher turn speeds are the P-51's preferred area, yes? So, this is one of the reasons why reduced power hurts the the P-51 more than reduced power hurts the Me 109; the 109 pilot is fine with both birds getting down to best climb / sustained turn speeds quickly, while the P-51 pilot would prefer both birds to stay fast, at corner or higher (where the 109's control stiffening is an issue). In other words: less power for both ships means the fight can't remain a high-speed fight for as long, which works in the 109's favor, since the 109 is more comfortable at slow speed fighting than the P-51 is. Yeah?

 

There are other things you're overlooking (not even getting into all of the other factors! e.g. hp. /= thrust, 'coz prop efficiencies); I'm having a difficult time trying to put them into words, even without worrying about language barriers, so I'm gonna leave that for someone more familiar with aerodynamics & language than you & I are.

In WW2 aircombat, even engaging occured in high speed flight with maximum power, once air combat maneuver occured speed of aircraft fall down quickly. Because thrust to weight ratio of WW2 aircraft is very low. In modern air combat, T/W ratio of most fighter aircraft is over 1 in sea level so they can remain their cornor speed, but not in WW2. If you play this game, You can find how quickly speed fall down.

Actually, there is no WW2 documents about Prop efficiency. Al least, I cannot found that information. One of my friend who studying aerodynamic in doctoral diploma couldn't found that, too. He said "You cannot find that documents cuz I can't. Just think like this. Most of WW2 prop efficiency around 0.7." That is the reason why I do not use thrust to weight ratio in this thread.

But you have to think about this. Horsepower of DB605DB is 1,850PS(1,823HP) and P-51D is 1,630HP in sea level. in 6800m 1577HP and 1410HP. If P-51D have far better propeller than Bf109K-4(Of course, I don't think so. Because Climb rate of Bf109K-4 far better than P-51D), so calculate it with prop eff of P-51D is 0.72, and Bf109K-4 is 0.69, weight is 9611lb and 7414lb.

Thrust = HP×eff×375/v

Sea level

P-51D - 1630×0.72×375/374=1176lbf - thrust to weight ratio - 1176/9611=0.122

Bf109K-4 - 1823×0.69×375/370=1274lbf - thrust to weight ratio - 1274/7414=0.171

6800m

P-51D - 1410×0.72×375/422=902lbf - thrust to weight ratio - 0.093

Bf109K-4 - 1577×0.69×375/443=921lbf - thrust to weight ratio - 0.124

Still Bf109K-4 better than P-51D, even undervalued prop eff of Bf109K-4.

In WW2 aircombat, even engaging occured in high speed flight with maximum power, once air combat maneuver occured speed of aircraft fall down quickly. Because thrust to weight ratio of WW2 aircraft is very low. In modern air combat, T/W ratio of most fighter aircraft is over 1 in sea level so they can remain their cornor speed, but not in WW2. If you play this game, You can find how quickly speed fall down.

You're not telling me anything I don't already know. My point remains: the more you cut the power of the pair, the faster the fight drops to sustained speeds, which works in the favor of the Me 109 and against the P-51. This is one of many factors that you're overlooking. I'm dubious at this point whether anything I say can convince you that the narrow parameters you are focusing on aren't sufficient to draw conclusions. No hard feelings; good evening & see you in the virtual sky sometime.

109 has leading edge slats?

You're not telling me anything I don't already know. My point remains: the more you cut the power of the pair, the faster the fight drops to sustained speeds, which works in the favor of the Me 109 and against the P-51. This is one of many factors that you're overlooking. I'm dubious at this point whether anything I say can convince you that the narrow parameters you are focusing on aren't sufficient to draw conclusions. No hard feelings; good evening & see you in the virtual sky sometime.

My conclusion about your opinion is even do not cut the power of both aircrafts, still Bf109K-4 have advantage in combat maneuvering. Because one of few advantage in combat maneuvering is stick force in high speed, but there is lots of advantage for Bf109K-4 like CLmax and P/M ratio, less drag in high AoA.

Actually, this is not ordinary situation but, if pilot of Bf109K-4 is experte, he could overcome high stick force of Bf109 with his adjustable stabilizer. I know it is not ordinary, but it could.

I don't have hard feeling, too. Good evening.(Actually, afternoon here.)

One another thing. The stick force problem. There is lots of opinions from german aces to test pilots of allied about stick force of Bf109. Around 500km/h it become stiff I think.

However, 714km/h TAS the top speed of Bf109 in 7,500m is only 480km/h IAS. If it was very serious problem, RLM order Messerschmitte to fix it, but it does not happened.

Actually, this is not ordinary situation but, if pilot of Bf109K-4 is experte, he could overcome high stick force of Bf109 with his adjustable stabilizer. I know it is not ordinary, but it could.

Nope, the adjustable stabilizer simply lacks the fine tuning of your regular stick, plus irl scenario with only 1 hand on the stick while you're working on the stabilizer , you'll be not pulling enough in the mean time.

I tried this thing after the stabilizer got fixed in BoS and believe me it's worthless in dogfight.

In WW2 aircombat, even engaging occured in high speed flight with maximum power, once air combat maneuver occured speed of aircraft fall down quickly. Because thrust to weight ratio of WW2 aircraft is very low. In modern air combat, T/W ratio of most fighter aircraft is over 1 in sea level so they can remain their cornor speed, but not in WW2. If you haul back on the stick like an undisciplined idiot, You can find how quickly speed fall down.

There, fixed it for you :smilewink:

even do not cut the power of both aircrafts, still Bf109K-4 have advantage in combat maneuvering.

Yes, I know. The Me 109 is generally going to outmaneuver the P-51. However, cutting the power makes the difference more extreme, hence my low opinion of Mr. Hanna's comparison. The actual difference was smaller than often is suggested.

Just wanted it to be clear that I'm not making, and never have made, the claim that the P-51 was more maneuverable than the Me 109 under average conditions; I concluded ~10 years ago that the (real) Me 109 was generally better at turning & climbing than the P-51.

I hope this clarification settles the misunderstanding.

There, fixed it for you :smilewink:

Oh Thanks. I learned a good attitude in discussion today:smilewink:.

There is one thing you have to know.

The top speed of Bf109K-4 is 714km/h TAS on 7,500m, it is just 480km/h IAS. In USAAF Material Command report, Stick of Bf109 is stiffed at 500km/h, Mark Hanna said Stick of it is stiffed at 500km/h but still can get 5G easily.

Even you do not lose speed quickly you can control Bf109K-4.

Yes, I know. The Me 109 is generally going to outmaneuver the P-51. However, cutting the power makes the difference more extreme, hence my low opinion of Mr. Hanna's comparison. The actual difference was smaller than often is suggested.

 

Just wanted it to be clear that I'm not making, and never have made, the claim that the P-51 was more maneuverable than the Me 109 under average conditions; I concluded ~10 years ago that the (real) Me 109 was generally better at turning & climbing than the P-51.

 

I hope this clarification settles the misunderstanding.

I understand. I think trying find more information about that. It was good discussion. Thank you for your opinion.

Oh Thanks. I learned a good attitude in discussion today:smilewink:.

 

There is one thing you have to know.

The top speed of Bf109K-4 is 714km/h TAS on 7,500m, it is just 480km/h IAS. In USAAF Material Command report, Stick of Bf109 is stiffed at 500km/h, Mark Hanna said Stick of it is stiffed at 500km/h but still can get 5G easily.

 

Even you do not lose speed quickly you can control Bf109K-4.

Oh, I know... and I'm not about to suggest that the P-51 should out-turn it at slow speed (I dislike the term "outmaneuver", as the term is poorly defined, and can easily include dozens of different factors). The point is that a smart, disciplined pilot in a Mustang just won't let the fight degenerate to low speeds.

The drawing shows you the real area of slat effectiveness. And the report explains you what slats are for.

The worst problem was not CLmax but abrupt wing drop and ailerons low effectiveness due to early stall. Aileron deflected down lowers critical AoA, so if you try to counteract roll near to stall you even will get reverse roll reaction.

Really effective slats generally are placed over the whole wingspan like Storch, An-2 or Su-25.

 

In the real flight the total effect of the wing-tip slats on lift is small because as the root of the wing having a lot of lift is stalled loosing a lot of lift, the plane drops down, so the tip AoA increases rapidly.

Yo-Yo, I think, that you're overlooked many important things about the automatic Slats.

1/ The automatic slats was added to the wing design of Bf-109 for ensure the maneuverability in combat, at low or medium speed, and high AoA. Not only for landing such as; Storch, An-2 o that you say.

I think, you must studying, why the Lavochkin La-5 and LAGG-3 (35 series) was equipped with automatics slats, copied from Bf-109 for fighting against Bf-109.

In the book " DESIGN FOR AIR COMBAT" by Ray Whitford -1987- The benefits of automatic slats in combat, are well explained:.

""" Slat with a slot (slotted stat)

Though complex, requiring rails and rollers in addition to actuators, this is probably the most widely used leading-edge device for combat aircraft. However, when account is taken of the resulting increase in maximum lift and its favourable effect on lateral/directional flying qualities, the extra complication is amply justified.

....

The slotted leading edge was originally proposed by Handley Page and Lachmann around 1920 and proved extremely beneficial in extending the lift curve, as shown in Fig 64. Designed to operate automatically, it consists of a slat quite free to move on tracks. At low AOA the slat is held flush against the leading edge. At high AOA the high local suctions on the slat create a forward chord-wise force, pulling out the slat. The slot so formed allows the wing to continue lifting to a higher AOA. significantly increasing the maximum lift coefficient. A slight chord extension also occurs. """""

Fig. 64

2/ the abrupt wing drop and ailerons low effectiveness that you say, was not a worrying case or usual case flying a Bf-109, due to it may occur only at landing at very low speed.

On contrary, wing drop and ailerons low effectiveness was a very important problem in the P-51 in tightened turns, and this was well know by the pilots, but this stall behavior of P-51 is poorly modelled in DCS too.

Moreover. you can turn with ailerons to 45 degrees of bank or more, then and pull for a tight turn with elevator and high AoA, and aileron flushed in the wing, and applying the rudder as necessary, whitout wing drop or any ailerons negative effecs.