109G2 - just broke speed of sound

Discussion in 'Warbirds International' started by lepper, Jul 30, 2006.

  1. Saddan

    Saddan Well-Known Member

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    109G is safe up to 12g, most WW2 aircraft did not reach their stress limits before being shoot down anyway...
     
  2. Red Ant

    Red Ant Well-Known Member

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    P-51 was a good plane but I completely doubt that. Just a nice piece of propaganda from a Mustang lover. The 109 was the uncontested king of climbers in WWII. Perhaps the late uberspits came close ... the P-51 never did.
     
  3. Red Ant

    Red Ant Well-Known Member

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    Perhaps, but not with a bomb strapped to its belly.
     
  4. Saddan

    Saddan Well-Known Member

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    The bomb has a effect of increasing G load for similar manouvers... It´s a preemptive effect.

    109G was clear to 12g, after 12g it suffers plastic deformation (ie. its shape is changed forever). Break point is 14g. The pilot would be dead or unconscius before 14g...

    Anyway production line samples where very far from these limits, most suffered light plastic deformation with just 8g, but this a non-issue as the aircraft would be shot down long before reaching its acumulated plastic deformation limits...
     
  5. gandhi

    gandhi Well-Known Member

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    ever hear of '1.5 safety factor'??

    voila

    12g is 1.5 of 8g

    all plane have safety factor
     
  6. biles

    biles Well-Known Member

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    Seems there is a lot more exponential progressions than geometric progression when this um, I am so confused, stuff, engineering stuff, I am so dumb, stuff, is um...
    well,
    happennin. Didn't Newton's laws have a bunch of exponents? I mean, he couldn't have figured out all this fancy stuff without exponential thingies, um, right?

    Not sure what I am sayin, becuase I failed grade three and stayed at that level...
    The only reason I finished school is they wanted me the fuck outta there before I was elderly.
     
  7. Red Ant

    Red Ant Well-Known Member

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    I'm not really privy to the exact limitations of the 109's airframe, but I'm almost sure that the hardpoints for external ordnance was rated for significantly lower G-forces than the rest of the airframe. For instance, the F-16C is normally cleared for 9 G's, but when carrying bombs or missiles (other than Sidewinders and AMRAAM's) it's only cleared for 5.5 G's.
     
  8. biles

    biles Well-Known Member

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    And there is some electronic gizmo too, that limits gees, sort of a kommandagerat type f-16 thingie, I forget what it is called.
    And if the pilot dumps his bombs and forgets to flick the switch, he is still limited while in air combat and, likely, dead too.
    CAT-somethin or other.
    Yeah
    CAT-1

    A 109 pulling 5.5 gees.
    Seems reasonable.
    Now, attach a 500 kg bomb.
    at 5.5 gees, it wieghs, um, 2750 kg.
    THAT IS A LOT OF BOMB.
    A 109Gx wieghs, what, um.....
    Approx 3000kg.....
    And at 5.5 gees, it wieghs
    16,500 kg.
    And a bomb slung would make it, um
    18,250 kg
    WOW.

    That would be kinda like a 110 gram barn swallow. I suppose a 110 gram barn swallow could fly.....
    straight down.

    I have read that one of the problems 109s suffered was wings pulling off. I suppose that was a problem many planes had.

    Take a piece of lumber.
    put the piece of lumber on two sawhorses.
    Put a bunch of wieght between the saw horses.
    When the wood starts to sag, put 5.5 times the wieght on it.
    LOL.

    Engineering ain't done with Roman Numerals. And it ain't done by addition and subtraction. An abacus won't work, nor will using yer fingers to do calculations, like I do.

    I always wanted to fire a .3006 rifle straight down at a target five miles away, straight down.
    I wonder what would happen.
    Would the bullet reach such a speed it would break up?
    Prolly wind resistance [that fuckin exponential stuff again] would slow it down. And prolly the spinning of the thing would tumble it.
    And a 110 gram sparrow couldn't catch flies.
    And I am a dummy and that is why I design no airplanes.
     
  9. looseleaf

    looseleaf Well-Known Member

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    WRONG! Read the accounts of P-51B pilots and from Wright Paterson AFB testing. Check out stories of Steve Gentile ww2 ace.

    All this adoration of the 109 is really going overboard. It was a good plane and better than most others for the first part of the war.
    I'm not a P-51 fan at all but many say it outclassed the 109 and was the best all-around fighter of WW2, including US AND German pilots.

    Remember: Chuck Yaeger's quotation: "First time I saw a 262, I shot it down."
    Remember: First US-262 dogfight; P38 met 262, 262 was shot down by P38.
     
  10. looseleaf

    looseleaf Well-Known Member

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    Maybe you are talking about the prototype 1939 Paris Air Show 109, that is hardly the case with the REAL 109s or "production" versions.
    No matter, if a 109 at FH can exceed the speed of sound and survive this is proof positve that the 109 flight sim is WAY OVERMODELED!
    If it was a 262, well...maybe ok..but a 109, COME ON ADMINS/Programmers/Code writers !!!!!
     
  11. looseleaf

    looseleaf Well-Known Member

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    You're right and he's right. He said adding the bomb increases the g-loading!

    That is to say: turning at X speed at Y radius without bomb the plane would pull a certain g load, then adding the bomb and traveling the same speed, same arc will INCREASE the g-load, so the plane would be pulling a higher g-load, MORE stress!(and most likely the bomb would leave its mounts and maybe take a few extra parts with it....???)

    And I agree, I really doubt a combat 109 could withstand 12 g's at all even new. For sure after about 5 g's the pilot is just along for the ride and not really in control anymore.
    Just a little note: The Bell X-1 was designed to withstand 16 g's.......and that plane DID fly faster than the speed of sound.
     
  12. biles

    biles Well-Known Member

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    Take a bucket and tie it on the end of a string.
    Swing it around at a certain rate of revolutions.
    there is a definite and measurable gee multiplier.
    take a bucket that wieghs lots more.
    Swing it around on the same string at the same rate.
    the gee mutliplier is the same.

    The bucket might rip your arms off though.
    Is that a gee load?
    Is that what gee load means?

    No, really...



    Is gees and gee load different?
     
  13. Red Ant

    Red Ant Well-Known Member

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    Biles is right, G load is not dependent on mass. It's simply a function of speed and turn radius.
     
  14. Saddan

    Saddan Well-Known Member

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    G load limits ARE dependent on torque effect.

    G load, wich is actually an aceleration, can be translated into a force and a force can be multiplied - keeping the work/power - or divided by the distance from the force application point to the center of mass of the object. (IE, less force but longer distance = same work, more force but shorter distance = same work)

    Talking about G-Loads over structures only makes sense, in the metal engineering stand point (G load can have some different effects on fluids and pressure systems, but we are talking about aiframes) if they are translated into forces that the aircraft can take.

    The bomb slung below the aircraft will have the effect of lowering the correspondent G-load for a given elevator position (Its a balance between those forces that go against the turn and those forces that push the turn).

    So a bomb doesnt necessarely change aircraft G-Limits, its effect is felt way before you start pulling G´s... It effects the aircraft own capacity to put itself at high G´s !

    Its the other way around !

    If your aircraft is able to rip itself (with a bomb underslug) at say, 9 G, it will rip appart, with the same force applied to the elevator control, at 12 G, and this is more of a control harmonization problem than a airframe problem...

    Translating everything : The problem is not the 109 supporting a 500kg at 12g, the problem is a 109 being able to reach 12g with a bomb at 1st place...

    But those high weight bombs where generally slug very near aircraft center of mass, making up for very low torque levels (airframe twisting), coupled with a increase of aircraft inertial momentum (Resistence to turn, IE, preemptively preventing the aircraft of actually REACHING a high-G situation).

    Its a previous effect (working against the forces that turns an aircraft) and not a post effect (working as a result of the forces that turns an aircraft).

    F-16 cannot be used here as an example due to its variable airframe harmonization (AKA = Fly by wire).

    Fly by wire aircraft are too complex to discuss, they are INTENTIONALLY built with controls capable of breaking the aircraft into pieces, the only thing that keeps them from doing this is the internal computer...

    The rule of thumb is that mass-loads do not prevent an aircraft from sustainning a specific G-Load, but, the other way around, mass loads increases the turn inertia preventing the aircraft of REACHING (and not from surviving) a higher G-load.

    The pratical effect is that a clean, pilot bringing the stick full back, 109 will turn at 8g in a very small turn radius. The same 109 with full fuel load and a 500kg below it will never reach its maximum 8g operational load, even with the pillot pushing the stick all the way back, due to increased inertias... The turn radius will suffer, and the aircraft will describe a bigger turn figure...

    Got it ?
     
    Last edited: Aug 14, 2006
  15. --stec

    --stec Well-Known Member

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    US pilots' accounts are as credible as their kill claims in ww2. I'd rather believe soviet pilot's stories about his plane told with commissar's nagant next to his occiput.
    Mustang was at best mediocre fighter (not a dogfighter for sure), what made it famous and important was the RANGE allowing it to travel with bombers all the way to target and back and quantities. Also average yank rookie pilot at that time was better trained and prepared for combat than average German rookie pilot.

    Think of inertia! Additional several hundred kilos slung under wings will make quite an additional force bending the wing as the plane makes G's. Hence it will decrease the plane's G limits.
     
  16. Red Ant

    Red Ant Well-Known Member

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    Nice essay. ;-) Tho reading it, I wasn't sure whether you wrote it to make it clear you're disagreeing with me or someone else.

    To remind you, here is what I said.

    And I stand by that because 'G' is not a force, it's an acceleration and supposing an object that flies a circle with a radius of x at a speed of y it makes diddly squat difference if the object has a mass of five hundred pounds or five thousand pounds. The G load is going to be the same.
     
  17. Saddan

    Saddan Well-Known Member

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    You cant mentiom acelleration without mentioning force...

    Aceleration is the result of a force applied to a mass (F=MA)
     
  18. Saddan

    Saddan Well-Known Member

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    it can be the same, but the STRUCTURAL result (Forces in the system) will be dfferent, but we can´t discuss this abstratically, we need an actual example system to discuss the torques and deformations involved in its behaviours.

    Per see, G-Load is very abstract, but the engineering interest in g-loads is that they result in forces applied at different points in the airframe (generating twist, deformation and breaks...)

    G-Load by itself is only a issue on fluid systems (IE, your blood), what a mechanical engenieer views in the g-load realm is the FORCES generated by g-loads...
     
  19. Red Ant

    Red Ant Well-Known Member

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    Basically I'm no longer sure what we're arguing about. Actually I have an inkling we're not disagreeing at all. Hanging heavy things onto an airplane reduces the number of G's it can pull without risking damage. That's agreed.
     
    Last edited: Aug 14, 2006
  20. Saddan

    Saddan Well-Known Member

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    BTW, the rule of thumb in building aircraft with very high INSTANTANEOUS turn rates (IE, those rates where the aerodynamics are negligible yet) is to have all the mass concentrated at the center of mass...

    This can be archieved with : Light wings, engine mounted exactly over the CG, long but light tails, etc...

    Imagine a power glider... It´s wings and tail are very strong but light, and all the essential mass is stored in a small bubble right in the center of the mass... This is done to decrease rotational inertias...

    Well, all i am trying to say is that the G-Limit is essentially the same on a 109 with or without bombs, but, the weight of the bombs will DECREASE the ARCHIEVABLE G-Load. People tend to think that the aircraft will behave the same and the bomb will make the aircraft rip appart at some lower G-Load. This is not true, the end result is an aircraft UNABLE To REACH the former G-Load it used to reach...

    Am i understandable ?
     
    Last edited: Aug 14, 2006