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Damage due to overspeed, over-g etc.


Baikingu
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Hi.
Anyone know if there is ever going to get implemented damage due to overspeed or over-g etc.


I'm able to do 8-9 g pull in a Hornet with full bomb loadout. (FCS g-limit set to 7,5)

I bring up the Hornet because by using the paddle switch you can pull way more g's than it should be able to sustain.

I also constantly see the Viper do 900 to even a 1000 knots way below 30k feet (many times at 10k to 20k feet).
I have read that at these speeds the compressor blades start to vibrate violently (due to the supersonic air entering the engine inlet) and eventually destroy the engine/badly damage.
There is also apparently some violent shacking/oscillation of the airframe according to an real F-16 pilot (https://www.youtube.com/watch?v=riZYJ8lP3nE min 2:30)
I bring up the F-16 because its the one jet i see constantly going this fast (at low alt.). And it does not have variable geometry inlet duct to counter the supersonic airflow.


Edited by Baikingu
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  • Baikingu changed the title to Damage due to overspeed, over-g etc.

You can rip ordinance off the wings of the MiG-21bis if you exceed G limits.

You can flame out the engine if you exceed Mmo/Vmo.

MiG-15bis will loose control if you exceed Mmo. I think you can rip the tanks off too?

Ka-50 will encounter rotor destruction if you exceed maximum speed and certain other flight conditions.

UH-1H can destroy main rotor mostly related to maneuver and G limits.

 

Both aircraft you have mentioned are still in Early Access

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I knew about the flameout in the MiG-21. As i understand it flamesout as a result of pulling g's that create "vortex" or disturbs the airflow at the inlet. (and/or causing fuel flow issues). But it doesn't "kill" the engine. It has an airstart mode because of this issue.
(Note: The 21 does have the inlet cone to help counter supersonic airflow in the engine)
Did not know about the ripping of ordinance at high g's in the Fishbed though.


But as far as i know you can't damage the engine due to overspeed (jets not helos)
Though the F-14 can breake its wings if sudden high g's are introduced.

The MiG-15 example is more a wing-stall than a over-g damage no?

I know you can overtorqu in helos. But concerning jets I belive we can't really "kill" the engine atm. AFAIK


Edited by Baikingu
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18 minutes ago, Baikingu said:

As i understand it flamesout as a result of pulling g's that create "vortex" or disturbs the airflow at the inlet.

No, you can flame it out at 1G.. done it many times.

19 minutes ago, Baikingu said:

But it doesn't "kill" the engine. It has an airstart mode because of this issue.

No. It has an airstart mode for any issue that causes a flame out in a single engine aircraft. F-16C also has an airstart mode. So does L-39...

21 minutes ago, Baikingu said:

(Note: The 21 does have the inlet cone to help counter supersonic airflow in the engine)

Note: F-16 inlet design and location is intentional to counter supersonic airflow in the engine

21 minutes ago, Baikingu said:

But as far as i know you can't damage the engine due to overspeed (jets not helos)

Overspeed of airframe? or Overspeed of engine? In the props you can certainly damage the engines with engine overspeed. Probably the same for helos too.

You would need to explain what you mean for jets. Just because something is damaged does not mean it instantly fails. It could still produce full power. But total useful life is reduced. It is not a simple answer as you seem to suggest (i.e. punish Viper fliers for going too fast).

 

24 minutes ago, Baikingu said:

Though the F-14 can breake its wings if sudden high g's are introduced.

The MiG-15 example is more a wing-stall than a over-g damage no?

In the F-15C you can also destroy tail with excessive G.

MiG-15 example is over-g damage.. but it's been a long time since I saw this so I would have to check.

 

I can't see there being any core simulation reason that jet engines should not suffer over stress damage, should the developer choose to enable it for that specific aircraft.

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Not «punish» Viper fliers for going too fast. But “punish” any pilot over stressing the jet in any airframe.
 

Just to take the F-16 example. I have seen (tacview) a 16 doing 950-1000 knots for a full minute or more chasing someone down with no consequences. I believe it’s only the later models of F-16 that has the “Diverterless supersonic inlet” design to counter supersonic air flow.?

Anyway I’m mostly wondering because i see the issue (lack of over stress simulation in general. in the modern jets) being often discussed in various forums.

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48 minutes ago, randomTOTEN said:

Just because something is damaged does not mean it instantly fails. It could still produce full power.

I agree. But potential power reduction and eventually engine failure if limits are exceeded for to long.

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56 minutes ago, randomTOTEN said:

Overspeed of airframe? or Overspeed of engine?

Both really. But I guess engines would be the first to go in the pure speed department. If we leave g’s out of the equation. For the more modern jets (we have in DCS)

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The limits IRL are there for a reason. To limit maintenance hours required, extended lifespan of the airframe etc. but also so you don’t inadvertently break the plane.

ofc. they put in a “buffer” in the calculation for safety reason.


Edited by Baikingu
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Well if i understood you correctly to your reply earlier. You clame that the F-16 we have in DCS has the Diverterless supersonic inlet. But the first picture is from an older version 16 inlet. And the second picture is the newer Diverterless supersonic inlet design for the 16.

and currently the 3D model in DCS looks like the first one.

 

But you seem to be pretty sure in your statements. So either you’re a real pilot/aviation engineer or just know all there is to know about the current F-16 block 50 we have in DCS. 
So if they are able to do 1000 knots at 15k feet without any consequences I will take your word on it

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Since every time you start a mission you get an aircraft fresh from the factory. So in that little time you fly the airplane and overstress it just a bit you it won't matter because as soon as you land and end the mission, the airframe gets scrapped and next time you have another factory fresh plane. If you abuse it in that little time you will get damage in all sorts of modules. The airframe will not break because someone pulled 12g for a couple of seconds, but if you pull those 12g another 20 times it will break sooner or later.

Engine overspeed is already modeled in the game and you also get certain warnings in certain frames if you are going to fast. And also flameouts can occur in pretty much all models which have an emergency airstart procedure.

 

And honestly you have time for so many extra posts but you were not able to look up Divertless supersonic inlet on wikipedia which states:

Quote

History

Initial research into the DSI was done by Antonio Ferri is the 1950s, and further developed & optimized by Lockheed Martin in the early 1990s using computational fluid dynamics. The first Lockheed DSI was flown on 11 December 1996 as part of a Technology Demonstration project. It was installed on an F-16 Block 30 fighter, replacing aircraft's original intake diverter. The modified F-16 demonstrated a maximum speed of Mach 2.0 (Mach 2.0 is the F-16's clean certified maximum speed) and handling characteristics similar to a normal F-16. It was also shown that subsonic specific excess power was slightly improved.

The DSI concept was introduced into the JAST/JSF program as a trade study item in mid-1994. It was compared with a traditional "caret" style inlet. The trade studies involved additional CFD, testing, and weight and cost analyses. A DSI was later incorporated into the design of the Lockheed Martin F-35 Lightning II after proving to be 30% lighter and showing lower production and maintenance costs over traditional inlets while still meeting all performance requirements.[1]

 

But you guess a lot and write a lot about it, instead of taking a couple of minutes to do a simple google search and bring some facts to your discussion.

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https://info.publicintelligence.net/HAF-F16.pdf

The main reason  i am curious is because according to this F-16 block 50 (the one we have in DCS) flight manual it states.

MAXIMUM AIRSPEED OPERATING LIMITATIONS Refer to figure 5 3. Maximum operating airspeed is 800 knots from sea level to 30,000 feet MSL. Above 30,000 feet MSL, the aircraft is limited to 2.05 mach”

 

so if the block 50 has a 800 knot limitation from sea level to 30k feet. I wonder it there would be possible severe consequences for exceeding this limit. As when I see them flying 1000 knots below 20k feet.

 

but its not just the F-16 I am wondering about. I have yet been able to damage stores etc. in the Hornet while pulling the paddle switch and exceeding the FCS g limit by 3-4 g’s multiple times. With heavy A-G Loadouts. 

(Yes the Hornet and Viper is still i EA)

 

Anyway a valid point on the fact that in DCS we always start with a factory fresh plane. (Even though the 3D model/skin has weathering on them. But thats just cosmetics)

so it would make sense they can take a bit extra punishment.

 

I am still curious though about the immense forces these planes can be subjected to that its possible to “break”/damage even a new plane.

 

And again there is a significant amount of players with way more playtime in many different modules that are asking for better over stress simulation in general.

 

I just want the real life limitations-consequences to be in the game aswell.

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If you exceed 800kts indicated for this aircraft, you're at serious risk of losing ailerons if you deflect them, the tail (or other parts of the fuselage) may just come apart spontaneously etc.  The engine could melt.

 

Losing any part of the fuselage means destruction at those speeds:  Any pitch or yaw it may induce would cause the aircraft to experience great forces and fall apart.

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4 hours ago, erniedaoage said:

Since every time you start a mission you get an aircraft fresh from the factory. So in that little time you fly the airplane and overstress it just a bit you it won't matter because as soon as you land and end the mission, the airframe gets scrapped and next time you have another factory fresh plane. If you abuse it in that little time you will get damage in all sorts of modules. The airframe will not break because someone pulled 12g for a couple of seconds, but if you pull those 12g another 20 times it will break sooner or later.

 

This ^^^

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Do you know what speed the GCI (F10 map) indicates?


I'm not sure if it shows the KCAS or KTAS.
I belive it shows KCAS. since if it shows KTAS when i see someone at 40k feet at say 280-300 knots that would mean they have an KCAS 124-133 knots.
which is stall speed


Makes more sense that is is KCAS 300 at 40k feet which is KTAS 677 knots.

If that is the case then when i see them doing KCAS 1000 knots its KTAS 1356 knots at 15 000 feet
Does that make sense? or am i way off?


Edited by Baikingu
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F10 speed is labeled.  If it's IAS it's the speed you're looking for WRT restrictions.

 

And yes, you are correct - any form of IAS will typically be less than the TAS as altitude increases.


Edited by GGTharos

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  • 2 weeks later...
On 12/3/2020 at 8:09 AM, Baikingu said:

https://info.publicintelligence.net/HAF-F16.pdf

The main reason  i am curious is because according to this F-16 block 50 (the one we have in DCS) flight manual it states.

MAXIMUM AIRSPEED OPERATING LIMITATIONS Refer to figure 5 3. Maximum operating airspeed is 800 knots from sea level to 30,000 feet MSL. Above 30,000 feet MSL, the aircraft is limited to 2.05 mach”

 

so if the block 50 has a 800 knot limitation from sea level to 30k feet. I wonder it there would be possible severe consequences for exceeding this limit. As when I see them flying 1000 knots below 20k feet.

 

but its not just the F-16 I am wondering about. I have yet been able to damage stores etc. in the Hornet while pulling the paddle switch and exceeding the FCS g limit by 3-4 g’s multiple times. With heavy A-G Loadouts. 

(Yes the Hornet and Viper is still i EA)

 

Anyway a valid point on the fact that in DCS we always start with a factory fresh plane. (Even though the 3D model/skin has weathering on them. But thats just cosmetics)

so it would make sense they can take a bit extra punishment.

 

I am still curious though about the immense forces these planes can be subjected to that its possible to “break”/damage even a new plane.

 

And again there is a significant amount of players with way more playtime in many different modules that are asking for better over stress simulation in general.

 

I just want the real life limitations-consequences to be in the game aswell.

 

Worth a read about said limits:

https://www.dropbox.com/s/8lqhpdolqge1a07/F-16_Code_One_article_Dont_Stretch_The_limits.pdf?dl=0

Something worth considering pretty much every jet is going to be built with a F.S. (factor of safety) where the "limits" aren't the maximum possible the jet can take (there will be exceptions ofc).  Rather it would just have negative impacts on the longevity of the airframe.  Which for 40+ million dollar jet is a big deal.  Hence stuff like the F14 being limited to 6.5G (7G?) during peacetime.  And instances of F15's pulling 12+ G's without the airframe suffering any damage.  There's also a few stories i've heard of hornets pulling 9+ g and the worst that happened was one of the engine bay doors was slightly bent.  So we should just be careful in making it so something, that yes is bad for the longevity (in terms of decades/ 10's of thousands of flight hours) of an airframe, but normally wouldn't be catastrophic is made so just because of limits meant to preserve the longevity of something.


Edited by nighthawk2174
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