J-10 Thread III (Closed to posting)

[no_name]

I am guessing because the engine is a turbofan, which mixes hot combustion gas with cold air ducted around the engine core, the final exhaust in the nozzle is actually cooler than the flash point of the fuel vapor.

Either that, or as soon as the exhaust plume leaves the nozzle it entrain surrounding cold ambient air so efficiently that it cools to below flash point of the fuel before the fuel had time to heat up to flash.

I don't know about military fuel but commercial jet fuel has a flash point of 60 degrees celsius and I doubt jet exhaust is that cool.

 

[chuck731]

I don't know about military fuel but commercial jet fuel has a flash point of 60 degrees celsius and I doubt jet exhaust is that cool.

If the fuel is dumped quickly then there may be no issue with flash, because so much fuel in liquid state is entering the exhaust stream that the fuel stick together and doesn't atomize quickly enough to cause substantial evaporation, and volume of the cold liquid fuel itself is cooling the exhaust, and preventing any small amount of fuel that does vapor from mixing well with exhaust gas for proper combustion until the body of the liquid has left the exhaust plume.

 

[plawolf]

Has anyone ever tries to use the fuel dump feature on AL31s as a defensive measure against incoming heatseekers or even enemy fighters on one's 6?

Dump a load of fuel as the missile approaches your six, light afterburners as the missile reaches the dumped fuel and the ensuing fireball should either cook off the missile or cause it to miss.

I guess the biggest risk to doing that would be if the fuel mixed too well with the surrounding air to create what would be in effect a massive fuel-air explosive blast that could also take out the fighter.

 

[chuck731]

Has anyone ever tries to use the fuel dump feature on AL31s as a defensive measure against incoming heatseekers or even enemy fighters on one's 6?

Dump a load of fuel as the missile approaches your six, light afterburners as the missile reaches the dumped fuel and the ensuing fireball should either cook off the missile or cause it to miss.

I guess the biggest risk to doing that would be if the fuel mixed too well with the surrounding air to create what would be in effect a massive fuel-air explosive blast that could also take out the fighter.

Modern IR AAM are capable of all aspect engagement, which means they don't need to chase the target from behind, and can engage the target from any angle relative to the target. Obviously this means in most tactical situations where modern missiles can be used would involve firing at a target from some position other than directly behind the target. This suggests the possibility of the a fireball from fuel dump engulfing a incoming missile is slim.

More recent IR AAM also have imaging IR sensors that can create images at several different wave lengths. It's no longer just a dumb heat seeker that will indiscriminatly go for any hot object it sees. This means the missile can discern both the shape of the target and distinguish it from the shape of the fireball, and discern the temperature of the target, and discern it from the temperatire of the fireball. In fact, modern IR AAM can discern the shape of aircraft so well that it can be programed to go for the plane's cockpit in order to maximize the chance of a pilot kill instead of merely an aircraft kill.


So the chance of a fuel dump fireball either incinerating or confusing a IR missile is low.

 

[Equation]

This means the missile can discern both the shape of the target and distinguish it from the shape of the fireball, and discern the temperature of the target, and discern it from the temperatire of the fireball. In fact, modern IR AAM can discern the shape of aircraft so well that it can be programed to go for the plane's cockpit in order to maximize the chance of a pilot kill instead of merely an aircraft kill.

I have a question Chuck, so if the missile locked on it's target and can distinguish its shape, so does that mean no matter what the targeted plane does to evade the missile it can still know it's intended target even though the shape changes (like hard rolling, sharp turns, going vertical, etc.)? I hope I'm not confusing you.

 

[chuck731]

I have a question Chuck, so if the missile locked on it's target and can distinguish its shape, so does that mean no matter what the targeted plane does to evade the missile it can still know it's intended target even though the shape changes (like hard rolling, sharp turns, going vertical, etc.)? I hope I'm not confusing you.

Pretty much. Modern missiles can not only image the target, its cone of vision can be up to 180 degrees. So there is little hope a cool headed pilot can can snap turn his plane out the cone of vision of the missile at the last second, like was possible in the 1960s 70s and 80s.

But there are still 2 ways a modern IR missile can be defeated.

1. blind its IR sensor, usually by means of a laser. The Russians supposedly have such a system undergoing test on the T-50. Flares don't work too well with imagine IR sensors.

2. take advantage of the fact that eventhough a missile is far more maneuverable than a plane, the high speed of the missile and the extremely high relative speed between plane and missile can still allow a skillfully piloted plane to turn inside the turning radius of the missile. When this happens, the missile would have to waste a large amount of its kenetic and fuel energy to turn all the way around to re-engage the target. Making very sharp turns vastly increases the drag on the missile, because the missile would for a while literally be moving side ways through the air, so it consume a lot of fuel for IR missiles to make radical maneuvers, like doubling back on its own course. Typically IR missiles can't do this more than once or twice before running out of fuel. And if the missile is engaging the target near the far end of its range envelope, it would have already burned much of its fuel when it reaches the target plane, and if the plane can just turn inside the missile once, the missile would be defeated.

 

[broadsword]

2. take advantage of the fact that eventhough a missile is far more maneuverable than a plane, the high speed of the missile and the extremely high relative speed between plane and missile can still allow a skillfully piloted plane to turn inside the turning radius of the missile.

But aren't modern missiles already developed with faster reaction to defeat the maneuver by making it impossible for the pilot to turn tighter than human tolerance to the G forces?

 

[chuck731]

But aren't modern missiles already developed with faster reaction to defeat the maneuver by making it impossible for the pilot to turn tighter than human tolerance to the G forces?

If the missile and the plane were traveling at similar speeds in similar direction, then yes, there is no possible way a plane that can turn at 10-12Gs at most can ever evade or turn inside a IR missile that can turn at 40Gs because the missile can turn in 1/4 the radius it takes for the plane to turn.

But in typical close air combat, the fighter will be traveling at subsonic or transonic speeds, while the missile will be traveling 3 times faster at Mach 3. The G force required to follow the same turning radius is proportional to square of speed. So in this case, if a Mach 1 plane makes a 10G turn, a Mach 3 missile would need to make 90G turn to follow the same turning radius and not allow the plane to turn inside itself. Most IR missiles advertise 40-50Gs, I don't know any that can do 90Gs.

This is how a plane with a man in it can still out turn a missile in combat environment.

 

[usaf0314]

 

[Totoro]

which bombs are those? 250 kg or 500 kg class?

if they're 250 kg, then why aren't those j10 using the four belly hardpoints as we have seen previously they can use for such bombs? that way the heavy duty middle hardpoint on the belly would be free either for more bombs, or more likely, for the central fuel tank?

it'd be nice if those bombs some day become equipped with satnav guided kits. then even a single j10 would pack a pretty decent punch in strike missions.

edit: measuring the bombs, it seems they're 250 kg class. so why not use additional belly hardpoints?