Bf-109 Stall characteristics

The most mass-produced fighter of World War II
thunder100
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Bf-109 Stall characteristics

Post thunder100 »

dear Bf-109 Designer,dear FDE guy

My newest addon to my FS9 is the Bf-109.I am allready owner of the 190's among other paywares.

I like exterior,the VC.

My question:
Why does the Bf-109 stall at 4,5 G positive and negative?
Basically this is not correct.It is too early for the positive G (should be arround 6,4 to 7 g and too late for negative G(outside looping) where 3 G would be more accurate.I have a90 year old friend which flew 109's and he is confirming this data(I mounted the Real Air Scouts G-Meter to the panel to confirm my feeling that the plane stalls to early)

Godspeed

Thunder100

SD_Research
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Re: Bf-109 Stall characteristics

Post SD_Research »

thunder100 wrote:dear Bf-109 Designer,dear FDE guy

My newest addon to my FS9 is the Bf-109.I am allready owner of the 190's among other paywares.

I like exterior,the VC.

My question:
Why does the Bf-109 stall at 4,5 G positive and negative?
Basically this is not correct.It is too early for the positive G (should be arround 6,4 to 7 g and too late for negative G(outside looping) where 3 G would be more accurate.I have a90 year old friend which flew 109's and he is confirming this data(I mounted the Real Air Scouts G-Meter to the panel to confirm my feeling that the plane stalls to early)

Godspeed

Thunder100
We appreciate your comments and will try to explain the situation.

We just tested our Bf 109E to confirm the performance were able to pull +7.7 G's in a dive recovery without stalling with nearly full fuel. It is all in proper energy management and technique.

Now for a more detailed explanation.

An airplane, any airplane, does not stall at a particular G force. The G-rating of a plane is meant only to measure the airframe's ability to handle stress, not when it will stall.

The point where a plane stalls is that point where the airflow over the wing is disturbed to such a point where it is no longer making lift, and this can be at a high angle of attack or a high G-force, or a low pitch angle and low G-force. The bank angle of the aircraft greatly increases the stalling speed, that is, the more you have the plane banked, the higher the stalling speed. The weight and loading (location of the center of gravity) is critical, and the Bf 109E as you know has the fuel tank located in a very bad place. This tank should be at least half-empty before attempting any serious acrobatics such as stalls. Also the technique you use to test the plane's stall characteristics is very important. Just a little too much stick and the plane will stall prematurely.

So to say the plane stalls incorrectly based on the amount of G's you are pulling in a simulator is not an accurate assessment of the performance of the plane. It was well-researched and will perform correctly but it will take practice.

On a final note, FS is not very good at simulating flight under negative-G conditions so don't expect too much under those circumstances.

thunder100
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Location: Austria

Post thunder100 »

Dear Researchers

I was not specific enough in my post.Yes to recover from dive it works very well.Also that over 800 km/h (heavy overspeed)there is no rudder function anymore is correct and well set up.But if you fly level at 4000-5000 m 400 km/h or over,and then pull into a tight turn you cannot do more then 4,5 g also the airspeed did not bleed off to stall speed.Also it goes in a vicious stall what needs gear out ,flap out to recover.In reality(as said to me) if you pull into a tight turn you would be able to still have 7,5 g like in the dive and stall characteristics would be different as you cannot pull further the plane does not turn in further and once you have regained more speed it turns again.

Is this corect?

Godspeed

Thunder100

SD_Research
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Post SD_Research »

thunder100 wrote:Dear Researchers

I was not specific enough in my post.Yes to recover from dive it works very well.Also that over 800 km/h (heavy overspeed)there is no rudder function anymore is correct and well set up.But if you fly level at 4000-5000 m 400 km/h or over,and then pull into a tight turn you cannot do more then 4,5 g also the airspeed did not bleed off to stall speed.Also it goes in a vicious stall what needs gear out ,flap out to recover.In reality(as said to me) if you pull into a tight turn you would be able to still have 7,5 g like in the dive and stall characteristics would be different as you cannot pull further the plane does not turn in further and once you have regained more speed it turns again.

Is this corect?

Godspeed

Thunder100
Regarding: "the airspeed did not bleed off to stall speed", are you expecting the plane to stall at the 1 G stalling speed listed in the specs in a turn at 250 mph IAS? This is a misunderstanding of how an aircraft stalls; the stall speed INCREASES drastically with bank angle and you can also induce an ACCELERATED STALL by hauling back too hard on the elevator.

This is not an arcade flight model; the lift coefficient of the wing and the aircraft weight and elevator authority are accurate and if you exceed what is physically possible the plane will stall.

However it sounds like much of the problem is in your technique as well as the way you are trying to translate what you have been told into controlling the airplane in the sim. We were able to pull over 6 G's in a descending turn but you must be very sensitive on the stick. You are not going to be able to pull 7+ G's in a turn going only 400 km/hr IAS, it is not going to happen. You are going much too slow. Lift is based on airspeed, bank angle, and wing angle of attack/coefficient of lift. Those numbers are hard numbers and the sim is pretty accurate in calculating them.

You should also be aware that most pilots begin to pass out at about 4 G's and could only sustain 6 G's for an instant, so the notion of WWII pilots screaming around pulling 7 G's is inaccurate to say the least. 7 G's is the normal limit for a modern jet fighter (although they can easily exceed this if the pilot decides to override the fly-by-wire), and those pilots are wearing G-suits.

We would recommend taking some time to learn more about accelerated stalls. You can start here...

http://shockwaveproductions.com/forum/viewtopic.php?t=5

GOZR
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Post GOZR »

Pilots that pass out at 4 G's will never enter combat period. Those statement are wrong.

7,5 g are exeeded in all cases.
We have people starting to faint or be very bad at 4.5 this is sure but a experimented pilot.. 7.5 is ok. During WW2 many new pilots died because of it even before the battle or even to shoot..

It depend of brief high G's or sustained G's.

Positive G's you get use to it by flying and training but the worst is the negatives G's this is the hardest and very hard to get used to... see impossible

It is possible to get 7.5 G's + at 400km/H it all depend of how..

I have to say that i did correct some plane's FM that i fly regularly in the FSX simulation to be more accurate to the real ones.
-GOZR

thunder100
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Post thunder100 »

Dear Developer

Sorry you seem not to understand my post.It is not claiming Shockwave anything.I also know that I can improve my own performance anytime,but as real pilot (past Up to Pilatus PC-9) and 10 years experience on several FS versions,I am quite sure to know how to fly a corner and initiate accelerated stall,within the limitations of an simulation(you cannot feel what the airframe does,while in real planes you get some hints always).But even so I have the honour to be able to try and discuss the plane with a real Bf-109 pilot ,one of my friends(now 90 years old and still mentaly fine).In this light the FDE/air file combination is,we think not fully accurate.You should be able to do up to 6,5 g for short time in cornering on a Bf-109 E upwards(K even a bit more).

As it is a minor item,of an otherwise very nice plane,as conclusion I will stop here ,as shockwave anyway thiks that the plane behaves correct and try to improve the behaviour by myself(air file)

Best regards

Thunder100

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Scott - A2A
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Post Scott - A2A »

GOZR,

Do I sense a little bit of good old fighter jock cockiness in your post?

To put things in perspective for the average person out there, when you are sitting in your chair, you are experiencing 1 g (representing earth's gravity). At 5 g's, your 200 lb body is now 1,000 lbs, and your 10 lb head is now 50lbs (most people complain when carrying a 50lb back pack properly distributing weight across their body).

So pull over 7.5 g's, and it will feel about the same as a full-grown Polar bear sitting on your lap, with two of those 50lb backpacks stacked on your head. Most people would last about 2 seconds under these conditions.

Most should watch this video:
One thing you should take away from watching these pilots in this video, is pulling g's is just extremely fatiguing and brutal on the body. After watching this video, think about how these pilots felt in the beginning and the end. Fighter jocks like to think they are super-human, which is what makes them so good at what they do, but watch this video and decide for yourself what just 4 g’s feels like if you have not experienced it yourself.
http://www.fugly.com/view_video.php?vie ... 1e006d8e24
Image

Scott.
A2A Simulations Inc.

SD_Research
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Post SD_Research »

thunder100 wrote:Dear Developer

Sorry you seem not to understand my post.It is not claiming Shockwave anything.I also know that I can improve my own performance anytime,but as real pilot (past Up to Pilatus PC-9) and 10 years experience on several FS versions,I am quite sure to know how to fly a corner and initiate accelerated stall,within the limitations of an simulation(you cannot feel what the airframe does,while in real planes you get some hints always).But even so I have the honour to be able to try and discuss the plane with a real Bf-109 pilot ,one of my friends(now 90 years old and still mentaly fine).In this light the FDE/air file combination is,we think not fully accurate.You should be able to do up to 6,5 g for short time in cornering on a Bf-109 E upwards(K even a bit more).

As it is a minor item,of an otherwise very nice plane,as conclusion I will stop here ,as shockwave anyway thiks that the plane behaves correct and try to improve the behaviour by myself(air file)

Best regards

Thunder100
We should mention again that we also consulted with a WWII Bf 109E ace (more than five victories) in developing this plane, as well as two other WWII P-51D double-aces (each with over ten victories apiece) and a highly experienced F4U-4 Corsair pilot with over 250 carrier landings to his credit. We flew in a P-51D among many other planes and researched this very, very carefully. Not only did we do this, but we consulted with current owner/operators of the Bf109E to a great extent so we feel our research has been very thorough in this regard. We agree you should be able to pull the 6+ G and we said before we were able to do this in testing on an instantaneous (very brief) basis, as would be correct. This seems to be a matter of technique.

Did you empty half the fuel from the fuel tank before you tried this? It is well-understood that the Bf 109's rear fuel tank contributes to early stalls if full, try emptying about half the fuel and being quite careful on the stick.

It is not realistic to think you can purchase a plane and immediately begin to fly that plane right to its limits; you would not do that with a real plane so please take some time with your new 109.

We will post some screen shots of turns and G-loads. BTW you do not need to install any gages to see the G-force, just press Shift-Z twice and the G-force will be displayed at the top of your screen, for convenience.
Last edited by SD_Research on 18 Dec 2006, 10:45, edited 2 times in total.

SD_Research
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Post SD_Research »

GOZR wrote:Pilots that pass out at 4 G's will never enter combat period. Those statement are wrong.

7,5 g are exeeded in all cases.
We have people starting to faint or be very bad at 4.5 this is sure but a experimented pilot.. 7.5 is ok. During WW2 many new pilots died because of it even before the battle or even to shoot..

It depend of brief high G's or sustained G's.

Positive G's you get use to it by flying and training but the worst is the negatives G's this is the hardest and very hard to get used to... see impossible

It is possible to get 7.5 G's + at 400km/H it all depend of how..

I have to say that i did correct some plane's FM that i fly regularly in the FSX simulation to be more accurate to the real ones.
I think we are saying exactly the same thing. We said before that BRIEF or instanteous G-forces of over 6 G's were possible but when pulling 4-5 G's sustained, pilots begin to black out and eventually have to back off. The 109E did not have G-suit like the later Corsairs and if memory serves it did not have a G-meter so claims of 7.5 G's are most likely exaggerated just a bit. As we said, the max G setting for fighter jets is usually to 7 G, and those guys are wearing serious G suits.

To get 7.5 G at 400 km/hr IAS in the 109 would be a matter of instantaneous G in a very sudden, descending maneuver and this would certainly result in a stall or near-stall condition; the aerodynamic math involved can easily show this.

Let us also mention it would require a SUPERHUMAN pilot to pull that kind of force without a g-suit...not likely.

SD_Research
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6.8 G at 392 km/hr

Post SD_Research »

We just pulled 6.8 G at 392 km/hr IAS (211 KIAS) at 19,900 feet with a full fuel tank in a 90-degree, descending bank.

Screenshots available on request.

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Scott - A2A
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Post Scott - A2A »

Thunder100,

Also, please understand and be assured that every comment made on these aircraft is heard and looked into if necessary. You are our customer and your comments are welcome, and I appreciate you taking the time to post.

I am not sure if this helps, but here's a screenshot of the 109 in a hard turn at a bit more than 200kts. Now if you watch that video above, imagine what the pilot is experiencing in this shot:
Image

Scott.
A2A Simulations Inc.

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Post Osram »

G Tolerance was of course a major issue and investigated in WWII (and probably before). Germany even built a specialy plane for this investigation, ther Berlin B9. This was a pure research vehicle, like the American "X" planes after the war. Here is the data they found:

Sitting position,
lower legs vertical Max. 6g over 3-4 seconds
Sitting position,
lower legs angled forward Max. 6.5g over 3-4 seconds
Sitting position, upper body angled forward,
lower legs angled forward as previously Max. 8g over 3-4 seconds
Lying supine with pilot
looking toward the rear Max. 15g over 120-160 seconds
Lying prone with pilot
facing the direction of flight Max. 12g over 120-180 seconds

Unfrotunately I only have a summary right now and don't know what pilots this is about, but probably it is about experienced ones. With complete newbies it would be somewhat lower.

IOW in WWII for 3-4 seconds you could pull 6-6.5 g. Shorter durations would allow even more (if the plane allows it), longer ones less. The reason the Ju87 has an automatism for the case that the pilot goes unconscious during pullout is simply that it can and does happen.

I doubt WWII pilots would be screened for g tolerance before admitted, but don't know.

Here is how you look when you "take a nap" ;) :
http://www.youtube.com/watch?v=ZF4r-knEZTA

thunder100
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Post thunder100 »

Dear Developer

Sorry You are right,I am wrong !!

As I have 1000 plus planes as kind of collection it takes long to load them.Therefore I saved the 109 level flight to retry again.I thought I was going to 60 % fuel(What is my usual amount) but typed by error 80 %.

At 20 % fuel the plane fly's as I and my friend supposed it should in best condition.Sorry again I should have checked twice.

Just one minor thing .i think as stall behaviour only one thing can be modelled.When the 109 has accelerated stall it usually drops the nose sharply into the corner when beeing low fuel,when heavy it drops the rear out of the vcorner and increases AOA to totally lose control(Because of the heavy tank)

Thank you for the patience

Godspeed

Thunder100

GOZR
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Post GOZR »

Scott - Shockwave It just happen that i flew actually the RL Yak9U flew in many different aircrafts as well like the Mig15 etc... You can find many real pilots and talk to them but you must discuss with real pilots that are good in Combat or flight sims.. they will understand the difference and separate the views, feeling g's compare to the flight sim.. It is not good to make a pilot try the sim with out spending lot of time in it first.

I now a few that fly in real as well on acrobatic flights and airliners witch are exelent in the Sims as FSX Lockon and IL2.

Same as a real aircraft you have to teach him first for some time.. ;)

I did correct some of your planes as well as some eyes positions some time just a bit off ;) ( exelent job on the planes btw )
-GOZR

SD_Research
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Post SD_Research »

GOZR wrote:Scott - Shockwave It just happen that i flew actually the RL Yak9U flew in many different aircrafts as well like the Mig15 etc... You can find many real pilots and talk to them but you must discuss with real pilots that are good in Combat or flight sims.. they will understand the difference and separate the views, feeling g's compare to the flight sim.. It is not good to make a pilot try the sim with out spending lot of time in it first.

I now a few that fly in real as well on acrobatic flights and airliners witch are exelent in the Sims as FSX Lockon and IL2.

Same as a real aircraft you have to teach him first for some time.. ;)

I did correct some of your planes as well as some eyes positions some time just a bit off ;) ( exelent job on the planes btw )
Yes, you are exactly right, there are many pilots and many opinions and it's not easy to translate for the sim! BTW we also interviewed a Yak-9 pilot.

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