Over-g question

[BloodyStub]

hello again,

 

got another question... why is it that when i pull a sharp turn in the 15c that im getting a over-g warning @ 7.5-8.5 g's shouldnt the 15c be able to do 10+.

 

when i do a g turn - level to start - then sharp right turn @ 8,000 feet agl @ 400 IAS @ 8 - 8.88 turn - im getting a over-g warning.

 

i know it does not mean anything and has no impact on the game - but i like to play it sorta real and a max 9g turn is supposed to be a air to air tactic.

 

example is when at an airshow a 15c pilot will do a 180 degree turn @ 9g's @ 425 or there about IAS - best conner speed

 

thanks

bloodystub

[GGTharos]

Who said it can do 10+ ?

 

The F-15C is cleared for 9g AFAIK - that's the max, and it's probably over the nominal structural limit.

[Maximus_G]

The plane might have it's weight (fuel and payload) limitations (speed limitations too, but not this case).

For example, the F-16's (MiG-29's, etc.) capability to sustain a 9G having full fuel load is said to be their advantage over the big birds.

[ARM505]

...and undoubtably the warning would come slightly before the actual limitation as most warnings tend to do, ie. warn you of impending problems! IRL, pulling 9G all the time would suck for airframe life I would imagine. Here in Lock On, as in all other sims, we get an out-of-the-box new plane each flight....pulling 9G the whole time might not get you, but it could catch your buddy out on the next flight.

[BloodyStub]

correct Maximus_G - the f-15 like the f-16 can pull a 9g turn for a quick 180 degree turn. as in case in point at the airshow this is a famous move that the 15 does every where.

 

the point is at best conner speed in lomac if i pull more then 7g's i get the over g warning and its not real. this vaule should be at least 9+.

 

for GGTharos the 15 can do this turn and it is practised by many american pilots for fighter training. take the documentry "american fighter pilots" disk1 eps3 - (believe is 1:3 might be 2:3 as this is when they are doing the BFM phase of the training. ) giggy does a 180 turn @ 9gs and the IP in the back tells him some pointers about it.

 

also fighter pilots have to pull 9g's in the centruifuge for what 20 secs or something... to pass its bye bye fighter pilot career.

 

i cant find a website to say it exactly, but from the sites that i can find and see its all most alway 9+ labled in the specs section.

but the point is it can and does do it all the time and lomac cant - simply a program change - overg = 9.X+ @ best conner speed. not 7 as is currently in lock on.

 

late

[Fjordmonkey]

I know it for a fact that at least the Norwegian F16's has a 9g limit in a clean configuration (no external stores except the AMA on the wingtip and maybe a captive Sidewinder on the other). As soon as you start hanging weapons and fueltanks onto the wings, the limit goes down.

 

Unless I'm wrong, the limit is (once again on the Norwegian jets) 5.5g with external 360gallon wingtanks, and 7.5 with a centerline tank on. Those were the numbers we were told when I asked about it. The reason I asked was because we had to spend some 5 hours removing access-panels and checking bulkheads on an aircraft that was Over-G'ed. (damn that flyboy breaking our aircraft....*grumble*)

[D-Scythe]

The reason why you can't pull 9G all the time is because the aircraft can only sustain a certain force that's fixed. Your weight unfortunately isn't fixed - your bird can be either pretty heavy or pretty light, depending on fuel and weapons. For example, an F-15C may pull 9 Gs with 50% fuel and 4 missiles, but this would say exert the same force on the airframe if the F-15 was pulling only 7 Gs with 80% fuel and 8 AAMs.

 

Despite this, I agree with the thread starter. The MiGs and Flankers tend to be able to pull 9 Gs over a wider range than the F-15C can, which is baseless and unproven IMO. The F-15C probably has more titanium built in it than either of the Russian birds, and is a pretty resilient aircraft in its own right.

[BloodyStub]

thanks ShadowXP this kinda clears it up for me.. that seams to make sence... but at the same time i think the 15 in lomac needs it G calculation made better because if you barely make a 45 degree turn with 50% and no aam's then i hit 7+g's easy... maybe it calculates it too fast.

 

again perameters that i was doing is as follows: FL150 (15,000 feet) turning on a 90 degree vertical to left or right and doing a 180 @ 400 knots (which is around best conner speed in the eagle) - this being a break turn.

 

oh and on that video "american fighter pilots" it is disc1 eps 2 and the start of ep3 that gets in to this for those that have it and would like to see it again.

 

now in that documentry they where doing these moves @ FL240 and above would this make any differnece at all.. hight alt?

[Yellonet]

Pulling a lot of drawn out high G manuevers could affect the pilots too ;)

[Yellonet]

The reason why you can't pull 9G all the time is because the aircraft can only sustain a certain force that's fixed. Your weight unfortunately isn't fixed - your bird can be either pretty heavy or pretty light, depending on fuel and weapons. For example, an F-15C may pull 9 Gs with 50% fuel and 4 missiles, but this would say exert the same force on the airframe if the F-15 was pulling only 7 Gs with 80% fuel and 8 AAMs.

 

Despite this, I agree with the thread starter. The MiGs and Flankers tend to be able to pull 9 Gs over a wider range than the F-15C can, which is baseless and unproven IMO. The F-15C probably has more titanium built in it than either of the Russian birds, and is a pretty resilient aircraft in its own right.

G resistance is more about how something is built, not by what.

Titanium is quite likely used as it is light and strong, but without knowing how it is used we cannot with certainty say that it helps G resitance or not.

[BloodyStub]

well i was playing with lockon and high g turns and i think i might have had my speed to high... i was going off of best conner speed... which in the sim is about 400knots indicated. also going off of video that i have seen and hud tapes that are on patricks.

 

so i lowered this to about 350knots and if i watched my joystick i did not over g **alot** but still once or twice..

 

alt high or low did not seam to matter - so im gonna play with my joystick setup sensetivy in the options and see what i can find out.

 

moving the stick in the real plan requires alot of force.. sometimes up to 10+lbs of force (this came from a website - www.f-15sim.com) so my joystick which is simulating this might be doing it too fast. so time to play with it.

 

i know its kinda trivial but hey .... more real - at least for me.

 

late

bloodystub

[bflagg]

my understanding is (also shown in the American Fighter Pilot DVD's) is when overG occurs.. you structurally messing up your plane and you shouldn't do it...

 

It would be nice if ED accomodated this in the game..

Too many overG's in a flight and one of the wings would fall off.

This would force the virtual pilots to fly it and not be just a Gfight all the time.

 

My info also states the 15 is rated at 14g.. but the limitation is 9-10 due to

the pilot....

This 14g rating I'm guessing.. is probably under the best and cleanest profile.

[Manny]

Who said it can do 10+ ?

 

The F-15C is cleared for 9g AFAIK - that's the max, and it's probably over the nominal structural limit.

 

Well, GG, if that is true and 9 is a nominal structural limit, then the Eagle must return for maintenance requiring airframe repair all the time. Perhaps the Eagle is G-limited to 9 but manufactured structurally for 12...this I do not know as I don't have the manufacturer's design information.

 

The MiG-25 info I posted in another thread recorded it pulling 11+ gs during training :confused: poor pilot but they wrote off the airframe when the plane landed.

[Fjordmonkey]

Overloading the G-limit is a good way to bring an aircraft to a permanent ground condition. Excessive G's can, as a worst case scenario, rip something off an aircraft in mid-air. Don't know about other airforces, but if an aircraft here in Norway gets Over-G'ed too badly, it will need a full shop-stay on-par with a 200-hour inspection before it will be certified to fly again. IF it is certified.

 

There has been accidents with aircraft where an Over-G has created warpage of the main spars in the aircraft fuselage, which again resulted in a breakup in mid air, killing the pilot and crashing the aircraft. Not very cost-effective use of an aircraft.

 

Usually, an aircraft is structually limited in the amount of G's it can take. For the F16 it's somewhere around 10 to 10.5 in a clean config, depending on fuel. Unless I'm wrong, the MiG-29 is rated for 13 or 14, just so it's theoretically impossible for the pilot to break the airframe through manouvering. This, again, would be limited by weapons and fuel-load.

 

Would be nice if this was programmed into the sim, as it would help a LOT on immersion and realism. Right now the only fear you have in a "Yank & Bank" is stalling out due to going outside the envelope, blacking out, and of course the danger of the other sides pilots :P

[504 Wolverine]

Would be nice if this was programmed into the sim, as it would help a LOT on immersion and realism. Right now the only fear you have in a "Yank & Bank" is stalling out due to going outside the envelope, blacking out, and of course the danger of the other sides pilots :P

 

It is modelled in the AFM. If you over G a 25T then bye bye wings.

[Fjordmonkey]

It is modelled in the AFM. If you over G a 25T then bye bye wings.

 

Cool ^^ Have to try that out, then.

 

Would be nice to have it for the other aircrafts as well. Ah, well. A fuelhead can dream, at least :D

[Manny]

Who said it can do 10+ ?

 

The F-15C is cleared for 9g AFAIK - that's the max, and it's probably over the nominal structural limit.

 

Would not the manufacturer have an absolute maximum and a operational maximum limited by the FCS?

 

Could those two numbers be equivalent? I highly doubt it.

 

The MiG-25 info I posted recorded a maximum of 11 gs, exceeding the operational limit, but not the maximum structural since the aircraft returned to base iintact.

[Yellonet]

Overloading the G-limit is a good way to bring an aircraft to a permanent ground condition. Excessive G's can, as a worst case scenario, rip something off an aircraft in mid-air. Don't know about other airforces, but if an aircraft here in Norway gets Over-G'ed too badly, it will need a full shop-stay on-par with a 200-hour inspection before it will be certified to fly again. IF it is certified.

 

There has been accidents with aircraft where an Over-G has created warpage of the main spars in the aircraft fuselage, which again resulted in a breakup in mid air, killing the pilot and crashing the aircraft. Not very cost-effective use of an aircraft.

 

Usually, an aircraft is structually limited in the amount of G's it can take. For the F16 it's somewhere around 10 to 10.5 in a clean config, depending on fuel. Unless I'm wrong, the MiG-29 is rated for 13 or 14, just so it's theoretically impossible for the pilot to break the airframe through manouvering. This, again, would be limited by weapons and fuel-load.

 

Would be nice if this was programmed into the sim, as it would help a LOT on immersion and realism. Right now the only fear you have in a "Yank & Bank" is stalling out due to going outside the envelope, blacking out, and of course the danger of the other sides pilots :P

In the Su-25T you can break stuff off.

Structural fatigue probably isn't cumulative though.

 

Edit: I was too late...

[Raploc]

In the book "Strike Eagle Flying the F-15E in the Gulf War" by William L. Smallwood a couple of pilots over-g'd their Strike Eagles. Later they could not take on fuel with their engines running but had to taxi to the ramp. One crew over-g'd at 6.5 G so me thinks that for every loadout there is a different max G you are allowed to pull. :icon_jook

[D-Scythe]

G resistance is more about how something is built, not by what.

Titanium is quite likely used as it is light and strong, but without knowing how it is used we cannot with certainty say that it helps G resitance or not.

 

I know that. The F-15C specifically had titanium spars built into the wings to withstand high Gs - the F-15A was only rated at 7.3 G I think, and this was increased to 9 in the F-15C. The F-15E was further strengthened to withstand 9 Gs at heavier payloads, but when carrying 3 bags of fuel and bombs...

 

I'm just saying that in the game, the MiG and the Flanker can pull 9 Gs over a greater speed/load-out range than the F-15 can. Not that it matters much though - 9 Gs will kill all your speed at corner.

[Yellonet]

I know that. The F-15C specifically had titanium spars built into the wings to withstand high Gs - the F-15A was only rated at 7.3 G I think, and this was increased to 9 in the F-15C. The F-15E was further strengthened to withstand 9 Gs at heavier payloads, but when carrying 3 bags of fuel and bombs...

Roger that, wasn't trying to 'teach' you or anything. I read somewhere that the Eagle is more than 25% titanum in weight.

 

I'm just saying that in the game, the MiG and the Flanker can pull 9 Gs over a greater speed/load-out range than the F-15 can. Not that it matters much though - 9 Gs will kill all your speed at corner.

It's a shame that we can pull G's as much as we want as this can and is being used unrealistically in dogfights and other situations.

[britgliderpilot]

In the book "Strike Eagle Flying the F-15E in the Gulf War" by William L. Smallwood a couple of pilots over-g'd their Strike Eagles. Later they could not take on fuel with their engines running but had to taxi to the ramp. One crew over-g'd at 6.5 G so me thinks that for every loadout there is a different max G you are allowed to pull. :icon_jook

 

Pretty close.

 

 

G-Force is a function of turn radius and speed.

 

It should be relatively obvious that if you pull 9G's with nothing on the pylons, the airframe is going to be less stressed than if you pull 9G's with a full load of weaponry.

Just imagine for a moment, the force that a 500lb bomb can put on an airframe when it's weight is multiplied 9 times . . . . seeing the point here ;)

 

 

Absolute G-limit is very rarely related to operational G-limit. The absolute limit will be what the aircraft can withstand and remain in one piece - and that's usually rather more than the G-load you'll pull in combat, which'd be about a maximum of 9.

 

Crash course in airframe fatigue approaches:

 

When you start to get close to G-limits, the structure of the aircraft begins to crack. Yes, really crack . . . . those little hairline fractures.

This is fine - an aircraft is designed to be able to deal with this for a certain length of time.

 

The design aim is to allow the aircraft to fly for a given number of hours at a given load. If you fly below that load all the time, the life will be extended because the cracks don't get as big.

If you fly above that load, airframe life WILL be reduced. Do it often, and airframe life will be SIGNIFICANTLY reduced.

 

As a result, and because combat aeroplanes are rare and expensive things, the G-limit is often artificially lowered to increase their flying life. The USN do it with quite a few of their aircraft . . . think it's 7G for the Hornet, rather than the theoretical 9G.

 

In a war scenario where it's critical, and airframe life usually isn't measured as critical by decades, you can push that operational G-limit up . . . . you don't care about the long-term fatigue effects.

 

 

 

The absolute maximum G that high-performance aircraft are designed to pull regularly is mostly limited by the pilot. S'true.

Humans aren't built to withstand much in the way of G, and even with the best G-suit it's extremely tough to stand them. The new Libelle suit we're developing in Yurp is probably the best there is . . . . but that's the first real suit that allows extended really high G's, and it's only coming into service now.

 

 

 

The G-modelling for the pilot is another question entirely . . . . there has been criticism over this in the past ;)

 

All of the above, by the way, doesn't prove in any way that the G-warnings in Lomac are right or wrong - it's a bit of useful background, though :p

[Yellonet]

Pretty close.

I'd say he was right on target ;)

[Yellonet]

As a result, and because combat aeroplanes are rare and expensive things, the G-limit is often artificially lowered to increase their flying life. The USN do it with quite a few of their aircraft . . . think it's 7G for the Hornet, rather than the theoretical 9G.

One of the advantages of F-15C compared to the A-model (I think) was that a software limitation was removed to increase the manueverability of the aircraft, allowing higher G's?

[Force_Feedback]

Errm, am I the only one here pulling 11-10 Gs in lomac on the eagle? And in an Su-27/Mig-29 you can yank as hard as you can, but it will remain nicely under the 9G limit, this all is with working ACS, so no jokes about that.

 

Mig-29s engines are also having titanium components, and the su-27 has titanium wing spars and other parts, like engine sections, intake doors and the all-famous cannon flameguard.

 

And How about the Mirage-2000, it is cleared to pull 13.5G and 10G is the structual sound limit (to not overstress the airframe).