J-20... The New Generation Fighter II

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Quickie

Quickie

Colonel
MiG-29 said:
well you will need to prove the rear cross section of the aft fuselage of the J-20 is narrower than the F-22`s specially when the widest part of the wing of the J-20 is at the aft of the aircraft, longer fuselages also generate more boundary layer thus drag is higher
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High mach aircrafts such as the Blackbird and Concorde have wings situated aft of the body for a reason. "Longer" is a relative term. A body that's "too long" will not be anymore draggier than a body that's too wide. The Blackbird has a long body relative to the F-22 but it can reach a top speed of more than 3 mach.
 
MiG-29

MiG-29

Banned Idiot
siegecrossbow said:
Correct. However we have to account for the fact that the total length of the F-22 include the length of the horizontal stabilizers that protrude a good length from the nozzles.
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The fuselage of the F-22 is much smaller, it measures 19 meters considering its tailplanes, the fuselage body length of the F-22 is less than 17 meters long not considering its tailplanes, now on the J-20 and F-22 case, considering a similar cockpit canopy size for both aircraft the J-20 has a total fuselage body length of 20 meters and considering its protruding vertical tails around 21-22 meters and with nose probe 23 meters
j20f22comp.jpg


Now use logic, having similar construction technics, the J-20 will be heavier unless the J-20 is all composites, something which its not true, if the F-22 weighs 19700kg empty why the J-20 will be lighter ifit is bigger?
 
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MiG-29

MiG-29

Banned Idiot
Quickie said:
High mach aircrafts such as the Blackbird and Concorde have wings situated aft of the body for a reason. "Longer" is a relative term. A body that's "too long" will not be anymore draggier than a body that's too wide. The Blackbird has a long body relative to the F-22 but it can reach a top speed of more than 3 mach.
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Your statement is not correct, the SR-71 achieves Mach 3.4 thanks to ramjets and a inlet cone design that moves backwards allowing supersonic flow to the engines, the F-22 has fixed inlets.
Long is not good, bigger is not good, the SR-71 is long just to carry lots of fuel in a very narrow fuselage, but the engines are not buried type, they are not part of the fuselage mainbody, but separate entities, thus alowing for a narrow fuselage.
The SR-71 has a much narrower fuselage than the F-22 and it has wing-fuselage blending with its chines that are basicly LERXes.
the J-20 cross section is not smaller than the F-22`s cross section and it has longer fuselage than the F-22`s, both cross sections are similar basicly the same with the exception of the inlet and engine nozzle separation at the end of the fuselage.
j20f22.jpg
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The J-20 won`t fly beyond Mach 2.0 simply because it has DSI inlets that are fixed.
 
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siegecrossbow

siegecrossbow

General
Staff member
Super Moderator
MiG-29 said:
The fuselage of trhe F-22 is much smaller, it measures 19 meters considering its tailplanes, the fuselage of the F-22 is less than 17 meters long this gives, now on the J-20 and F-22 case, considering a similar cockpit canopy size for both aircraft the J-20 has a total length of 20 meters fuselage body length and considering its protuding vertical tails around 21-22 meters and with nose probe 23 meters
j20f22comp.jpg


Now use logic, having similar construction technics, the J-20 will be heavier unless the J-20 is all composites, something with its not true, if the F-22 weighs 19700kg empty why the J-20 will be lighter?
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Read my comment again. That is exactly what I tried to say.
 
plawolf

plawolf

Lieutenant General
As soon as you make a baseless assumption, you cast doubt on your findings.

The canopy of the J20 and F22 may be similar, but it would be very unlikely for them to be the exact same size. Thus basing an estimate of aircraft size on the assumption that they are the same is likely to result in errors.

What more, your choice to measure the F22 from the middle of the tail and compare it to the whole of the J20 makes no sense.

Your arguments on drag is also less then convincing since you are only looking at a 2D image to make the comparison. The J10 may be physically larger, but that does not automatically equate to it having greater drag, a point reinforced by the fact that the J20 has higher swept wings and vertical stabilizers. The J20's considerably smaller vertical stabilizers would also help to reduce its drag.

Agility and speed is as much about lift and drag as it is about weight and thrust. The J20 can be heavier and have less thrust than the F22, but if it has a suitably lower drag and higher lift, it can still be just as agile and fast as the F22, if not more so.

But even if you had two exact, to scale models of the planes with exact weight and thrust figures for both, it would be hard to decide which would be faster and more agile without needing the use of a supercomputer and advanced modeling software and/or a wind tunnel.

To make such pronouncements using a few pictures is... unconvincing, at best.
 
MiG-29

MiG-29

Banned Idiot
plawolf said:
As soon as you make a baseless assumption, you cast doubt on your findings.

The canopy of the J20 and F22 may be similar, but it would be very unlikely for them to be the exact same size. Thus basing an estimate of aircraft size on the assumption that they are the same is likely to result in errors.

What more, your choice to measure the F22 from the middle of the tail and compare it to the whole of the J20 makes no sense.

Your arguments on drag is also less then convincing since you are only looking at a 2D image to make the comparison. The J10 may be physically larger, but that does not automatically equate to it having greater drag, a point reinforced by the fact that the J20 has higher swept wings and vertical stabilizers. The J20's considerably smaller vertical stabilizers would also help to reduce its drag.

Agility and speed is as much about lift and drag as it is about weight and thrust. The J20 can be heavier and have less thrust than the F22, but if it has a suitably lower drag and higher lift, it can still be just as agile and fast as the F22, if not more so.

But even if you had two exact, to scale models of the planes with exact weight and thrust figures for both, it would be hard to decide which would be faster and more agile without needing the use of a supercomputer and advanced modeling software and/or a wind tunnel.

To make such pronouncements using a few pictures is... unconvincing, at best.
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J-20 has smaller vertical dorsal tail than the F-22:true
the F-22 has no ventral tails while the J-20 does:true
the J-20 vertical dorsal tails and ventral tails total area is close to the F-22`s vertical tail area:true
then it can not have much less drag.

does the J-20 have a longer fuselage and larger cross section than the F-22?:yes it does
does the F-22 and J-20`s cross sections have similar size and shape? :yes they do

was the F-22 designed using super computers?: yes it was

Is it possible the F-22 has a design more optimized to the air dominance role?: yes it is possible

conclusion: it is more likely the J-20 is designed as an interceptor and strike aircraft that will use HMS and advanced missiles in a similar fashion to the F-35 and not to the F-22.
it will be less stealthy due to canards and size than the F-35 but will probably carry much more ordenance and longer range missiles than the F-35
 
L

latenlazy

Brigadier
MiG-29 said:
The fuselage of the F-22 is much smaller, it measures 19 meters considering its tailplanes, the fuselage body length of the F-22 is less than 17 meters long not considering its tailplanes, now on the J-20 and F-22 case, considering a similar cockpit canopy size for both aircraft the J-20 has a total fuselage body length of 20 meters and considering its protruding vertical tails around 21-22 meters and with nose probe 23 meters
j20f22comp.jpg


Now use logic, having similar construction technics, the J-20 will be heavier unless the J-20 is all composites, something which its not true, if the F-22 weighs 19700kg empty why the J-20 will be lighter ifit is bigger?
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Um, the length of the J-20 is no more than 20 meters long WITH its vertical stabilizers and horizontal stabs (At least two reliable methods of measurement have confirmed this). That nose probe won't be there in the production aircraft of course. We have no way of knowing what the dry weight is. That has as much to do with volume of the plane as it does with its density, and its internal structure. If most of the plane's extra volume is empty for fuel, its dry weight may be no more than the F-22s, or it may not (either lighter or heavier). Either way, it's advisable not to continue making assessments based on poor and unqualifiable guess work.

MiG-29 said:
The J-20 won`t fly beyond Mach 2.0 simply because it has DSI inlets that are fixed.
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That actually depends on what speed envelope the DSI's bump is optimized for. Furthermore, there is some possibility (though I myself would like to see further evidence) that the inlet lip of the J-20 is variable.
 
MiG-29

MiG-29

Banned Idiot
latenlazy said:
Um, the length of the J-20 is no more than 20 meters long WITH its vertical stabilizers and horizontal stabs (At least two reliable methods of measurement have confirmed this). That nose probe won't be there in the production aircraft of course. We have no way of knowing what the dry weight is. That has as much to do with volume of the plane as it does with its density, and its internal structure. If most of the plane's extra volume is empty for fuel, its dry weight may be no more than the F-22s, or it may not (either lighter or heavier). Either way, it's advisable not to continue making assessments based on poor and unqualifiable guess work.
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my assesment is not baised, i use aerodynamics and simple laws, the J-20 is not a F-22 type aircraft unless it can have engines of 19000kg of thrust with thrust vectoring, it is for sure heavier and much bigger and bigger than 20 meters around 21 without probe.
with the current technology, it is more likely the J-20 is a F-35 type aircraft rather than a F-22, using AAM like the AIM-9X, the J-20 can have the F-35 ability to fight but carrying more weapons sacrificing stealth a bit.
 
MiG-29

MiG-29

Banned Idiot
siegecrossbow said:
Doesn't this go against your hypothesis that the J-20 will primarily serve as an interceptor?
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In my opinion it is a F-35 type aircraft, just bigger because china lacks still engines with a rate of 17000 or 18000kg of thrust, thus they needed to design a twin engine that could carry enough fuel and weapons on a LO fuselage.
They added canards to add agility.
One of the findings of the F-35 design process is canard increase pitch control and AoA handling but do not give better drag neither at supersonic speeds neither at low speeds, by using relaxed stability the F-35 will achieve equal drag levels.
The F-35 wing type is rather conventional, so adding a canard would have added extra agility, but having HMS and AAMs like the AIM-9X plus excellent avionics the F-35 did not need canards, canards sacrifice stealth due to trimming and position, thus they went along for a simple back tailed design.

China i do not think it has now a 17000kg engine and much less a 18000kg engine then canards with RAM and a low drag delta wing made sense.
 
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