JH-7/JH-7A/JH-7B Thread

[schenkus]

What really boggles my mind is the fact that they recently used the JH-7 for an interception mission recently. Can't they use something like a J-11 or even a J-8II instead?

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Does the link give any details ?

I could understand using a JH-7 for an interception if it's the closest available plane and the intercepted aircraft isn't a fighter jet.

 

[plawolf]

What really boggles my mind is the fact that they recently used the JH-7 for an interception mission recently. Can't they use something like a J-11 or even a J-8II instead?

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Its not a combat intercept, just a shadowing exercise. They could have used a trainer for all the practical difference that would have made.

It's probably more an issue of convenience and timing.

A JH7 flight was probably on patrol in the area, so ground control just rerouted them to intercept rather than potentially have to scramble a flight of J11s or J8s from Hainan.

 

[Richard Santos]

You mean J-16 has higher parasitic drag than jh-7?

Lift-induced drag, aka induced drag, is inversely proportional to aspect ratio and wing area. The ideal formula for it is too long to write here, so I refer you to the last equation at

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This is why gliders have huge wings for low induced drag at low speeds, where it is the dominating drag component.

Parasitic drag scales linearly with wetted area, which increases with increasing wing area. It also scales linearly with dynamic pressure (0.5rho*speed^2), which makes it larger than induced drag at higher speeds. In an ideal case,
Parasitic drag = dynamic pressure * wetted area * drag coefficient
see

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Other than this mixup in terminology, I agree with your assessment and conclusions on the agility, low&fast flying properties and high speed range of the aircraft.

Because su-27, or f-16 and f-15 try to achieve the lowest wing loading possible without excessive span, their wings are rather low aspect ratio. In addition, to improve performance at near stall AOA, I believe su-27 and f-16 put a twist on their wing chord so the tip is the last point to stall. F-15 achieve the same result by giving the wing a increasingly severe camber and twist. This means in normal flight only a small part of the wing is at the optimal AOA at a given moment, of the wing airfoil is not optimally shaped for low drag flight. This is what gives them higher induced drag.

 

[Richard Santos]

Does the link give any details ?

I could understand using a JH-7 for an interception if it's the closest available plane and the intercepted aircraft isn't a fighter jet.

This is not a hostile interception where the opponent is expected to use the full performance envelope of his aircraft to evade interception. So any aircraft that can fly faster and higher than the interceptee's normal cruising speed and altitude, and has the range to perform the intercept, it can perform the intercept.

 

[delft]

Because su-27, or f-16 and f-15 try to achieve the lowest wing loading possible without excessive span, their wings are rather low aspect ratio. In addition, to improve performance at near stall AOA, I believe su-27 and f-16 put a twist on their wing chord so the tip is the last point to stall. F-15 achieve the same result by giving the wing a increasingly severe camber and twist. This means in normal flight only a small part of the wing is at the optimal AOA at a given moment, of the wing airfoil is not optimally shaped for low drag flight. This is what gives them higher induced drag.

Induced drag is most important at high lift coefficient and thus at low speed taking off and landing and while manouvring at higher speed. Use flaps and slats and vortex generators as necessary. Cruising flight shouldn't be compromised for induced drag considerations.

 

[Richard Santos]

No, ydesigns that accept worse lift to drag relation impacts all induced drag in all flight regimes.

 

[MastanKhan]

I am not sure about that.

J-16 obvious derives her airframe design from su-27. The su-27 prioritized combat maneuverability over high speed penetration of enemy airspace. As a result, su-27/j-16 has huge wings, low wing loading, and big engines for its size. This means j-16 can sustain high turn rates, fantastic climb rates, and high roll and,pitch rates. But achieving these same attributes means su-27/j-16 also has high induced drag and needs big engines to go fast, are highly sensitive to gust and offers a punishing ride at high speed low altitude flight. In other words they make poor airframes for deep high speed low altitude penetrations of enemy airspace.

If jh-7 on the other hand didn't seem to put much emphasis on combat maneuverability. So it has relatively small wings with high wing loading. This means Jh-7 can't turn or climb with the su-27/j-16, but it probably has low gust response, low induced drag, smooth ride at low altitude, high speed penetration role, and need less fuel comsumption to,achieve the same low altitude, high speed performance, and thus a longer range for the same fuel load.

Yes, both the US and Russia decided to base their current strike fighters off of air superiority fighter airframes. But that was not done because air superiority airframes makes ideal low altitude penetration strike airframes. That was done to save money by reusing big powerfully engined airframes that could carry a lot of weight by virtues of their big engines and big wings. A truly ideal penetration strike aircraft would have a whole different mix of wing size, engine power, and airframe design than f-15e and su-34.

Hi,

Thank you for some informative comments on the JH7.

 

[davidau]

PLAAF has recruited the 11th batch of female pilots consisting 35 female cadets for 2017 admission program.

..flying tigress on JH 7..

...strict selection criteria: excellent eye sight, no colour blind, ideal weight & height; pass political, physical and have graduated from high school and have high scores in college entrance exams to be acceptable to specialised university...

...amongst the enrolled female pilots they can select training in combat, management, flight leader, astronauts and other options..

..Liu Yang and Wang Yaping are the two female astronaut to go to space and return safely...

..in future selected female astronauts will be sent to the China manned Space Station...

..studying...

..relaxing...

..after years of hard work...graduation!!

..under guidance...

...flying comradeship...

 

[davidau]

..more...

...i'm ready..

..a bit nervous..

...here we go....

...safely return..

..yippy....

 

[Equation]

I wonder how many of these female pilots will be qualify into China's next class of Taikonauts space program.