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Flight model


Mistang

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Obviously this question will be deleted. The Young's modulus of steel is around 400gpa. Therefore an hour flight could only put around 400 gj per square meter on the aircraft.

 

During a turn the aircraft is putting its weight on the wing root. So this comes out to around 40 million tons per square meter over the flight or 10,000 tons per second. The aircraft might also be accelerating a few times gravity so the effective weight comes out to a thousand tons.

 

So the maximum possible weight for structural reasons is around the size of an an225 and anything else is physically impossible.


 

And of course this is an absurd example, the tolerances in fighter jets are a few mm and they die earlier. This is why the flight model on stuff like the tomcat is fake and in real life it literally explodes beyond 6g. https://fighterjetsworld.com/air/f-14-tomcat-explode-after-sonic-boom-cause-engine-exploded-due-to-compression-failure/334/https://fighterjetsworld.com/air/f-14-tomcat-explode-after-sonic-boom-cause-engine-exploded-due-to-compression-failure/334/

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Maybe he (?) is on to something !

if I weigh 90 kg, then every time I step each foot carries 90 kg. 
if I take 20,000 steps each foot has carried 900,000 kg

900,000 kg resting on my foot would instantly turn it into bloody pulp, so obviously it’s impossible for me to walk anywhere, and my designer is conning you all. 

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Cheers.

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This from the guy who once wrote, and I quote: I'm not going to bother with everything you asked because I'm lazy

 

Should be an interesting discussion....😄


Edited by Lurker
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11 hours ago, Weta43 said:

Maybe he (?) is on to something !

if I weigh 90 kg, then every time I step each foot carries 90 kg. 
if I take 20,000 steps each foot has carried 900,000 kg

900,000 kg resting on my foot would instantly turn it into bloody pulp, so obviously it’s impossible for me to walk anywhere, and my designer is conning you all. 

If it wasn't for your bodies healing capacity, yes.

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This thread has just been officially added to the "Most weird thread of the year" contest

 

(With a good chance on winning 👍)

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4 hours ago, sirrah said:

This thread has just been officially added to the "Most weird thread of the year" contest

 

(With a good chance on winning 👍)

I dunno, the UFO nuts have been really active and very "energetic."

Reformers hate him! This one weird trick found by a bush pilot will make gunfighter obsessed old farts angry at your multi-role carrier deck line up!

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51 minutes ago, MiG21bisFishbedL said:

I dunno, the UFO nuts have been really active and very "energetic."

Hmm 🤔

You're right. Shouldn't underestimate the UFO thread...

But, at least that thread has an opening post that one can understand/watch.

 

I read the opening paragraph of this thread 3 times, yet still I have no clue what I'm reading. (Must be because I'm not native English)

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21 minutes ago, sirrah said:

Must be because I'm not native English

I'm going for a wild take here - I think your English and reading comprehension are perfectly fine, and the issue lies somewhere else.

 

But yeah the...posters with a creative perspective on the laws of physics, shall we say...have been putting in the effort lately.

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Based purely off the link you posted, which includes the phrase ''engine exploded due to compression failure''

 

I fail to see what flight models and g-limits have to do with the engine disintegrating and destroying the aircraft.

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Де вороги, знайдуться козаки їх перемогти.

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Young's modulus doesn't have much meaning in regards to failure points... It's essentially a measure of how much a material will stretch for a given amount of internal stress (force over the cross-sectional area). The material doesn't fail when it reaches a stress equal to the young's modulus, it fails when it reaches the end of the elastic region, the yield strength, and catastrophically fails when it reaches the ultimate strength of the material. Stress is also not cumulative, so energy input is mostly meaningless. The whole post is nonsense lol.

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"Fighter pilots have ice in their veins. They don't have emotions. They think, anticipate. They know that fear and other concerns cloud your mind from what's going on and what you should be involved in." -Buzz Aldrin

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Ah, so the usual routine of somebody reading random articles online they don't really understand, then rushing to the forums to demonstrate what fools the devs are for not utilising Google properly.

Де вороги, знайдуться козаки їх перемогти.

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On 8/21/2021 at 4:56 PM, Nightwolf said:

Young's modulus doesn't have much meaning in regards to failure points... It's essentially a measure of how much a material will stretch for a given amount of internal stress (force over the cross-sectional area). The material doesn't fail when it reaches a stress equal to the young's modulus, it fails when it reaches the end of the elastic region, the yield strength, and catastrophically fails when it reaches the ultimate strength of the material. Stress is also not cumulative, so energy input is mostly meaningless. The whole post is nonsense lol.

That doesn't help. It still fails.

 

Game is physically impossible.


Edited by Mistang
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The game is physically impossible if you redefine physics and materials science to your liking, shocker! You can't just do simple math like this to calculate the structural strength of an aircraft. You immediately assume all the weight of the plane is supported by the wing spar, which is not true even if the wings were the only things generating lift, not to mention that on many aircraft the fuselage generates a decent portion of the lift of the aircraft. Then, you'd need the force and the cross-sectional areas of the load-bearing members to calculate the stress (measured in units of pressure). That then tells you the percent deformation from unloaded that the member would flex to (where the Young's Modulus comes in). If the internal stress is outside the elastic region (beyond the yield strength of the material), then the metal permanently deforms, which is a failure. For our intents, as long as you're within the elastic region, you can load and unload the metal as many times as you want, it will return to its original position. This is why energy input is meaningless, because as long as you keep the stress below a certain point, the material won't fail (There are some factors to do with load-unload cycles that can lower the failure point of the bar but that's in the hundreds of thousands of cycles if not more, and highly material dependent).

 

I don't know where you're getting your information but just saying "this doesn't help, it still fails" without rebutting any of the arguments doesn't work.

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"Fighter pilots have ice in their veins. They don't have emotions. They think, anticipate. They know that fear and other concerns cloud your mind from what's going on and what you should be involved in." -Buzz Aldrin

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1 hour ago, Nightwolf said:

The game is physically impossible if you redefine physics and materials science to your liking, shocker! You can't just do simple math like this to calculate the structural strength of an aircraft. You immediately assume all the weight of the plane is supported by the wing spar, which is not true even if the wings were the only things generating lift, not to mention that on many aircraft the fuselage generates a decent portion of the lift of the aircraft. Then, you'd need the force and the cross-sectional areas of the load-bearing members to calculate the stress (measured in units of pressure). That then tells you the percent deformation from unloaded that the member would flex to (where the Young's Modulus comes in). If the internal stress is outside the elastic region (beyond the yield strength of the material), then the metal permanently deforms, which is a failure. For our intents, as long as you're within the elastic region, you can load and unload the metal as many times as you want, it will return to its original position. This is why energy input is meaningless, because as long as you keep the stress below a certain point, the material won't fail (There are some factors to do with load-unload cycles that can lower the failure point of the bar but that's in the hundreds of thousands of cycles if not more, and highly material dependent).

 

I don't know where you're getting your information but just saying "this doesn't help, it still fails" without rebutting any of the arguments doesn't work.


No, this is wrong, aircraft routinely develop cracks while operating within parameters and this is the entire reason for preflight checks. If it cracks enough pieces fall off. This is a incremental process, it's not tensile strength which is a lot higher.

 

China Airlines flight 006 experienced vertical load factors of up to 5.1 g on 19 February 1985. 

 

LC9dc.jpg

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1 hour ago, Mistang said:


No, this is wrong, aircraft routinely develop cracks while operating within parameters and this is the entire reason for preflight checks. If it cracks enough pieces fall off. This is a incremental process, it's not tensile strength which is a lot higher.

 

 

Hi Mistang, no you're not the only one here who is/was an engineer, an aeronautical engineer to be precise. So obviously it's very difficult to accurately model fatigue failures in a simulation, a very simplified model has to be used and it's never going to be anywhere near realistic.  As you correctly pointed out stress fractures occur over a period of time based on the forces the airframe has been exposed to, that's why real aircraft log many data points such as G loading and landing/take off data. In simulations such as DCS, the only real option is to model tensile strength.  Preflight checks very rarely discover cracks and fatigue failures on airframes, only very large failures in obvious areas would be spotted.  Preflight checks are supposed to check for obvious damage, wear and consumables such as oil levels, tire wear, broken latches, lose panels etc.  Fatigue is usually only discovered in 2nd or 3rd line servicing. 


Edited by Yeti42

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