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Why it's hard limited to 6G when speed higher than Mach 0.85?


Kumabit

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Why it's hard limited to 6G maximum when the speed is higher than Mach 0.85? The airframe should "feel" the same when pulling 9G at Mach 1 and pulling 9G at Mach 0.8. No matter under what speed, as long as the aircraft is experiencing the same gravitational acceleration, the stress applied on the airframe should be the same. Therefore, I don't think it's necessary to put a 6G limit when the speed is high.

 

If anyone know why, please tell me. Also, it seems like the JF17 is the only aircraft that has this limitaion.

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The reason aircraft have a lower G limit in the transonic region (.9-1.1 Mach) Is due to the center of pressure on the wing shifting. As the aircraft starts to enter and then punch through the shockwave, the center of pressure shifts on the wing. Usually shifting aft, This means that the "load bearing structure" of the wing, the main spar usually, is no longer colocated with the center of pressure. Basically think all of the aircrafts weight is no longer being supported by the main spar which is designed to support the full G capability of the aircraft. After the transonic region the Center of Pressure stabilizes and is no longer moving, and the aircraft can resume its normal G limits.

Wings arent solid structures, they are mostly empty space with specific strengthened parts, the G limit goes down so you aren't trying to pull 8 times the aircrafts weight supported by just the thin metal of the skin of the aircraft.

 

Below corner airspeed AOA is always the limiting factor in how much you can pull, above corner airspeed (Transonic or supersonic is generally always above corner) G is the limiting factor, you are going fast enough supersonic that you can generate the maximum G of the aircraft with very little AOA.

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If anyone know why, please tell me. Also, it seems like the JF17 is the only aircraft that has this limitaion.

 

You can bypass this limiter by turning on EFCS which will help you pull more than 8 Gs at high mach speed 0.85+, But be cautious about that cause it can break your wings at 1.3 Mach 11Gs etc stuff

 

Recommended Settings for EFCS:-

 

Interception loadout 4 SD-10s, you are free to pull more than 9 Gs no problem with that, Don't use EFCS when you have fuel tanks cause it can break the wings and break the fuel tanks, After using EFCS bring it back to Auto if you are flying less that mach 0.85 something cause you are not gonna pull high G on EFCS at low speeds, I recommend Bind Keys on Auto And EFCS. It will help you during BVR engagement.

[sIGPIC][/sIGPIC]

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Pretty much all modern FBW aircraft in the game have similar restrictions, the F-18 changes the control laws in the transsonic region, so does the Mirage and F-16 (I think, I do not own it). G limit gets replaced by an AoA limit for most, if not all, of them.

 

For F-18 you just push a button and you are allowed to pull 9G at Mach 1.3. For F-16 and M2000C there is no such limitation.

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You can bypass this limiter by turning on EFCS which will help you pull more than 8 Gs at high mach speed 0.85+, But be cautious about that cause it can break your wings at 1.3 Mach 11Gs etc stuff

 

Recommended Settings for EFCS:-

 

Interception loadout 4 SD-10s, you are free to pull more than 9 Gs no problem with that, Don't use EFCS when you have fuel tanks cause it can break the wings and break the fuel tanks, After using EFCS bring it back to Auto if you are flying less that mach 0.85 something cause you are not gonna pull high G on EFCS at low speeds, I recommend Bind Keys on Auto And EFCS. It will help you during BVR engagement.

 

Thank you for your suggestion! I will try this.

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The shift in center of focus usually results in drastic change in pitching moment if you're changing speed rapidly. The problem usually reveals when decelerating rapidly through transonic regions where static stability rapidly decreases and for the same elevator deflection, you're able to create more pitch-up moment, causing a tendency to overshoot the aircraft structural limit.

 

The closest aircraft I found with a similar G limit is the Mig-29, which allows 9G below m0.85 and 7G above m0.85 (if gross weight is below 14200kg), and 8G below m0.85 and 6G above m0.85 (if gross weight is above 14200kg). Although you can overcome the G limit by applying extra force on the stick (same as Su-27), but the pilot irl is not allowed to override the stick kicker.

 

Speaking of Su-27, it has a similar arrangement but there're 3 different FBW G limit values for subsonic, transonic and supersonic, and varies with gross weight. The pilot irl are also prohibited from overriding the limit.

 

The JF-17 took a conservative approach which does not vary its FCS G limit based on gross weight.

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EFM / FCS developer, Deka Ironwork Simulations.

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The shift in center of focus usually results in drastic change in pitching moment if you're changing speed rapidly. The problem usually reveals when decelerating rapidly through transonic regions where static stability rapidly decreases and for the same elevator deflection, you're able to create more pitch-up moment, causing a tendency to overshoot the aircraft structural limit.

 

The closest aircraft I found with a similar G limit is the Mig-29, which allows 9G below m0.85 and 7G above m0.85 (if gross weight is below 14200kg), and 8G below m0.85 and 6G above m0.85 (if gross weight is above 14200kg). Although you can overcome the G limit by applying extra force on the stick (same as Su-27), but the pilot irl is not allowed to override the stick kicker.

 

Speaking of Su-27, it has a similar arrangement but there're 3 different FBW G limit values for subsonic, transonic and supersonic, and varies with gross weight. The pilot irl are also prohibited from overriding the limit.

 

The JF-17 took a conservative approach which does not vary its FCS G limit based on gross weight.

 

Thank you for these information!

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