Some opinion about maneuverability of Bf109K-4

[gomwolf]

The problem with that logic is that a lot of people (who favor the German aircraft) here argue that the Mustang should not have 150 grade fuel because "the DCS Mustang is supposed to represent a 9th Tactical Air Force Mustang", but by that same logic, they would NOT be using drop tanks, because they would be, well, *tactical* aircraft on relatively short-range missions.

 

Also, we're not talking "real" conditions of the real fights; if we were, we would also have to consider the shoddy late war German quality control, poor fuel, and insufficient number of fighters. We're talking purely about the capabilities of factory-fresh, built-to-spec fighters. To make that an honest discussion, you have to take out ALL variables, not just the ones you feel like avoiding. Unless you want to go down rabbit holes about how poor Luftwaffe POL was in late '44 and '45, or that the Kurfurst *also* had to tote around a belly tank just to have the loiter time for an intercept, let's do apples to apples. Similar fuel loadout, no externals.

 

Even if there is P-51D have lower weight to 9200lb(4173Kg) there is no big difference

 

P/M ratio

At sea level - 291W/kg

At 20,000ft - 250W /kg

At 33 ,000ft - 180W/kg

 

wingloading is quite lower than Bf109. P-51D can turn one circle faster than heavyer, but less CLmax and P/M ratio of aircraft, small stall angle and more drag at out of drag bucket of laminar flow airfoil is still huge onstacle. P-51D cannot sustain turn high AOA. Because it make P-51D stall.

[GrapeJam]

[quote=gomwolf;2368039

 

Few days ago, I asked stall speed of Bf109G to Messerschmitte Flugmuseum. Flugmuseum have three airworth Bf109s(G-4, G-6, G-10) and have lots of flight experience. I got answer about that. Thanks Flugmuseum.

 

Aircraft - Bf109G-4

Weigt - 5,842lb/2,650kg

Altitude - 6,000ft/1828m

Flap and undercarriage retracted

Stall Speed - 86mph/140kph

Wingarea - 16.1m²

 

I calculated CLmax of Bf109G based on this answer and standard atmosphere.

Standart atmospheric density of 2,000m is 1.0068kg/m³. When it conversion to kgf×s²/m⁴ is 0.102kgf×s²/m⁴.

Didn't see anything wrong with the weight? And even then modern example are unarmed so I'd take the stall speed of modern example with a grain of salt.

[gavagai]

I cannot understand about it...

Afaik leading-edge slat make aircraft can fly more slower speed. Stall speed calculation formula is [stall speed = √(2weight)/(density×CLmax×Wingarea)]. So leading-edge slat raise total CLmax.

 

Am I wrong?

 

When air flows over a wing there is a transition from laminar to turbulent flow. For the P-51, the transition happens relatively far aft on the chord line, so the wing stalls sooner rather than later because of separation of airflow at high angles of attack.

 

Leading edge slats move the transition from laminar to turbulent airflow forward on the chord line, so a higher angle of attack can be maintained before separation of airflow.

[gomwolf]

Didn't see anything wrong with the weight? And even then modern example are unarmed so I'd take the stall speed of modern example with a grain of salt.

 

In CLmax calculation weight cannot affect CLmax value. Because stall speed changed by weight configuration.

When you see same part of P-51D's calculation, you will found weight of P-51D is 8900lb.

[GrapeJam]

In CLmax calculation weight cannot affect CLmax value. Because stall speed changed by weight configuration.

When you see same part of P-51D's calculation, you will found weight of P-51D is 8900lb.

The strange thing is is according to Naca Report 829, page 29 stated that the P51D at full weight (5 tons) had a clmax of 1.28. The K4 in tunnel test had a clmax of 1.48. Also the P51 stall speed at 9000lbs IAS is 101mph, even in CAS it's 107mph. So your figures're off, frigging off.

 

Edited April 7, 2015 by GrapeJam

[gomwolf]

The strange thing is is according to Naca Report 829, page 29 stated that the P51D at full weight (5 tons) had a clmax of 1.28. The K4 in tunnel test had a clmax of 1.48. Also the P51 stall speed at 9000lbs IAS is 101mph, even in CAS it's 107mph. So your figures're off, frigging off.

 

 

You picture is engine off chart...

 

And I want to see that K-4 wind tunnel chart. Where can I find that?

Edited April 7, 2015 by gomwolf

[GrapeJam]

You picture is engine off chart...

Yeah, but the pic is to correct to stall speed you've obtained. Not regard the clmax.

[gomwolf]

Yeah, but the pic is to correct to stall speed you've obtained. Not regard the clmax.

 

http://www.leonbadboysmith.com/images/EM7.gif

 

 

This link is the EM chart of P-51D with engine power on.

I calculated CLmax with TAS in this EM chart. If you want I can give you another source.

Edited April 7, 2015 by gomwolf

[GrapeJam]

http://www.leonbadboysmith.com/images/EM7.gif

 

 

This link is the EM chart of P-51D with engine power on.

I calculated CLmax with TAS in this EM chart. If you want I can give you another source.

Why use this when you can use the official source? Which is mine.

 

Also stall speed is lower with power on. And calculating clmax based on power on stall speed is a poor way as power setting varies, power off stall speed is the only valid way.

Edited April 7, 2015 by GrapeJam

[gomwolf]

Yeah, but the pic is to correct to stall speed you've obtained. Not regard the clmax.

 

Why use this when you can use the official source? Which is mine.

 

Also stall speed is lower with power on.

 

There is no aircraft without power in air combat. Why do you want calculate CLmax for combat without power chart? I cannot understand about it.

 

See this wartime document.

 

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

 

Stalling speed is 95.3mph at 9071lb. Calculate it. Almost same value with my calculation. This is official wartime document of North American. If test environment is correct answer of calculation is same. Even it is not wartime official document.

[GrapeJam]

There is no aircraft without power in air combat. Why do you want calculate CLmax for combat without power chart? I cannot understand about it.

Because maximum power setting varies a lot. Modern aircrafts engine are gimped to increase engine life. The only valid way is to use power off stall speed than add power and calculate based on it.

 

See then wartime document.

 

http://www.wwiiaircraftperformance.o...na-46-130.html

 

Stalling speed is 95.3mph at 9071lb. Calculate it. Almost same value with my calculation. This is official wartime document of North American. If test environment is correct answer of calculation is same. Even it is not wartime official document.

Yeah, calculated.

 

And then you look at this real test.

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

Noticed the plane in "calculated" test was 7mph lower at SL(and the P51D in real test had wings racks) and climbed 200fpm slower?

Also, the "stall speed" in calculated test didn't even state what condition it was in, for all we know it could be power off stall speed with full flaps and gears down. Look at my stall speed chart, it's the almost the same.

Edited April 7, 2015 by GrapeJam

[gomwolf]

Because maximum power setting varies a lot. Modern aircrafts engine are gimped to increase engine life. The only valid way is to use power off stall speed than add power and calculate based on it.

 

Yeah, calculated.

 

And then you look at this real test.

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

Noticed the plane in "calculated" test was 7mph lower at SL(and the P51D in real test had wings racks) and climbed 200fpm slower?

Also, the "stall speed" in calculated test didn't even state what condition it was in, for all we know it could be power off stall speed with full flaps and gears down. Look at my stall speed chart, it's the almost the same.

 

 

1. I really want to know how to stall in level flight with maximum power. How could you do that?

 

2. That is why i do not use that official chart, but that calculation was almost right, it was tested in real life in 80's and the answer was almost same. If you want denying reliability of my source, find other chart stalling speed with power on and calculate CLmax. If it is far differ with my value, I will accept my calculation about P-51D is wrong.

[Kurfürst]

And then you look at this real test.

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

Noticed the plane in "calculated" test was 7mph lower at SL(and the P51D in real test had wings racks) and climbed 200fpm slower?

 

And then look at this real test. http://www.wwiiaircraftperformance.org/mustang/tk589.html

 

354 mph at SL at 67".

 

Mustang flight test results are all over the place.

[GrapeJam]

And then look at this real test. http://www.wwiiaircraftperformance.org/mustang/tk589.html

 

354 mph at SL at 67".

 

Mustang flight test results are all over the place.

Considering that British Thunderbolt III had lower service ceiling than 109G, excuse me if I'm skeptical about British capability to maintain and operate foreign aircrafts. Hey even P51As sent to the Soviets were also in pretty poor shape. Their "new" Spitfires transported to Australia also operated rather poorly(and I'm not talking about kill ratio)

 

Would you like your 109 to be modeled after some hand me down Finnish 109?

Edited April 7, 2015 by GrapeJam

[Kurfürst]

There is nothing wrong with the variation of flight test results, its just a consequence of mass production. I am just pointing out that the test you posted was apparantly for an exceptionally well built aircraft (or different measurement standards), mine was probably a worn or less well built example.

 

The typical aircraft was probably somewhere between.

[DB 605]

Would you like your 109 to be modeled after some hand me down Finnish 109?

 

What do you mean by this?

[GrapeJam]

What do you mean by this?

Most of Finnish 109Gs later on were rebuilt 2nd hand 109Gs used by the Germans.

[DB 605]

Most of Finnish 109Gs later on were rebuilt 2nd hand 109Gs used by the Germans.

 

No they weren't. Some of the G2's (from first batch, 16 new/14 rebuilt) were, but one that was in finnish tests (MT-215) was brand new erla built. All G6's were new too.

[GrapeJam]

http://www.virtualpilots.fi/feature/articles/109myths/

Me 109 G:

"The first 30 of the Me 109 G-2s (delivered to Finnish Air Force 1943) were delivered right from the factory production line. After that the delivered planes were more or less used, they were rebuilt. Also the first of the G-6s (delivered in 1944) were new, then later deliveries were rebuilds. The Germans did not make any distinction between new and rebuilt planes, the rebuilds were upgraded with new gear. The used planes were however found to be more awkward in use. They were unfinished. Some individuals could in higher speeds be held in straight course by constant application of vertical rudder. You had to throttle back as your leg began to shake and you were no more able to keep the pedal down. It got the worse the more speed you had. This kind of things. The planes used to veer to the right at takeoff and when airborne to the left. Products of the wartime, I say. Yet some 32000 of them were made after all."

- Kyösti Karhila, Finnish fighter ace. 32 victories. Source: Interview by Finnish Virtual Pilots Association.

[DB 605]

Well yeah, some of the replacement G6's and G2's were rebuilt but majority was new.

[IIIJG52_Otto_]

Slats do almost NOTHING regarding total CL max because they work only for a small part of the wing with low lift. The only one work they implemented for is to provide aileron authority just to complete stall and to avoid tip-stall leading to abrupt wing drop.

 

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:

Edited April 7, 2015 by III/JG52_Otto_+

[Kwiatek]

True that slats in 109 dont cover whole wing area but true is also that 109 pilots ( WW2 or modern) report that slats help a lot in turns and stall charactersitic of 109.

 

In DCS 109 fly like slats was only visual effect and has little effect.

 

I suppose 109 slats casue little higher Clmax and also higher critical angle of attack for that plane.

 

Comparing to P-51 laminar wing profil im no wonder that moder pilots whose fly 109 and P-51 said that P-51 dont turn at all comparing to 109.

 

 

 

http://www.skipholm.com/willy-messerschmitt.htm

 

" Once airborne and cleaned-up, the aircraft is a delight. A classic! And real fighter, ready to rock and roll! And the speed it loves to roll around is 250 mph and below. The roll rate is very good and very positive at 250 mph. Above 250 mph the ailerons get heavy and at 300 they are very similar to a P-51. Any speed after that results in the ailerons getting fairly solid and you need two hands on the stick for any meaningful roll rates. Most of my flights have been in formation with P-51s and the Me-109 is more maneuverable than the P-51 in most conditions. The Me-109 performs very well against the P-51 for takeoff, climb, and moderate cruise, but once the P-51 starts a dive or adds power in a level condition, the P-51 outperforms the Me-109 easily.

 

Pitch control is also delightful and very positive at 250 mph and below. As pitch and accompanying G is increased, the leading edge slats start to deploy. I have not found either aircraft to have any problems with asymmetrical slat deployment, as we see in other aircraft such as an A-4 for instance. The aircraft reacts very well to heavy maneuvering, and there is never any discomfort in pulling Gs, as wing separation and accompanying wing drop is mild, is easily noticed and dealt with by lightening up on the G. Pitch force tends to get heavy at speeds above 300 mph, but is still easily managed with a little 2-hand pull or left hand re-trimming."

Edited April 8, 2015 by Kwiatek

[IIIJG52_Otto_]

True that slats in 109 dont cover whole wing area but true is also that 109 pilots ( WW2 or modern) report that slats help a lot in turns and stall charactersitic of 109.

...

In DCS 109 fly like slats was only visual effect and has little effect.

...

I agree :thumbup:

[Ala13_ManOWar]

" Once airborne and cleaned-up, the aircraft is a delight. A classic! And real fighter, ready to rock and roll! And the speed it loves to roll around is 250 mph and below. The roll rate is very good and very positive at 250 mph. Above 250 mph the ailerons get heavy and at 300 they are very similar to a P-51. Any speed after that results in the ailerons getting fairly solid and you need two hands on the stick for any meaningful roll rates. Most of my flights have been in formation with P-51s and the Me-109 is more maneuverable than the P-51 in most conditions. The Me-109 performs very well against the P-51 for takeoff, climb, and moderate cruise, but once the P-51 starts a dive or adds power in a level condition, the P-51 outperforms the Me-109 easily.

 

Pitch control is also delightful and very positive at 250 mph and below. As pitch and accompanying G is increased, the leading edge slats start to deploy. I have not found either aircraft to have any problems with asymmetrical slat deployment, as we see in other aircraft such as an A-4 for instance. The aircraft reacts very well to heavy maneuvering, and there is never any discomfort in pulling Gs, as wing separation and accompanying wing drop is mild, is easily noticed and dealt with by lightening up on the G. Pitch force tends to get heavy at speeds above 300 mph, but is still easily managed with a little 2-hand pull or left hand re-trimming."

Don't get me wrong but, where does those words conflict with the current 109K4 model?

 

S!

[Yo-Yo]

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:

 

I meant slats effect that was documented in WT report.