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JF-17 Thunder Multirole Fighter [Thread 6]

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I understand of the rest of your post.

I am keen to know the spool up time for RD93 which is currently in use and the expected version of MA and do I took your post as meant to informing that RD93-MA will comes with FADEC ?? Kindly answer Thanks.
To date I have not read any official data to suggest what exactly is the Spool up time of RD93. So at least I cant answer that question for you. There is information of a general nature on Airliners.net | Airplanes - Aviation - Aircraft - Aircraft Photos & News but none related to RD93. The MA will have increased thrust and FADEC which are being reported as a big pluses for it along with increase in MTBO. However between now and 2018 is a long time and a lot can happen/change till then.
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If f16 has better maneuverability than jf17 then how come PAF claims it did well against SU 27 of PLAAF in Exercise ? I believe that in air show the jf17 is not pulled to its limit or near to it. What I have noticed is that Jf17 in airshow is actually like a simple maneuvers or fly passes not actual performance display, Even if they claim it was maneuver display. Maybe not displaying the complete quality of the jet.
 
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Thank you for the correction. While we have got you here, would you please explain the Quadruplex fly by wire and in layman terms what it means. Thanks in advance.
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Very simply a fbw system that is four times redundant for safety. So there are four flight computers runing normally and all four would have to fail for the fbw system to fail. All four are doing the same thing as a safety measure. If one fails the system doesn't fail. Not even if three fail.
 
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SCO states in Central Asia likely export targets for JF-17
Staff Reporter 2015-09-30
A JF-17 Thunder fighter on display at the Paris Air Show, June 15, 2015. (Photo/Xinhua)

China and Pakistan may target the Central Asian members of the Shanghai Cooperation Organisation as potential buyers of their jointly developed JF-17 Thunder (FC-1 Xiaolong) multi-role combat aircraft, according to the Kanwa Defense Review, a Canada-based Chinese-language military magazine.
At this year's Paris Air Show in June, it was reported that the first export order for the fighter jet — developed jointly by the Pakistan Aeronautical Complex and the Chengdu Aircraft Corporation of China — had been signed, with deliveries likely to begin in 2017. While industry experts note that manufacturers remain secretive as to the buyer, there are unconfirmed claims that deal was signed with either Myanmar or Sri Lanka.
Kanwa notes that China and Pakistan's export options for the JF-17 are essentially limited to Central Asia. West Asia and the Middle East are traditionally markets for European and American manufacturers, and no countries in these regions are likely to import the JF-17 in the near future, even though the Arab states of the Persian Gulf have all signaled plans to update their fighter fleets.
JF17.jpg

Of the former Soviet states in Central Asia, Kazakhstan is unlikely to buy JF-17s due to its close military ties to Russia, from which it recently bought a fleet of Su-30SM fighters.
That leaves countries such as Tajikistan, Uzbekistan and Kyrgyzstan, none of which have acquired new fighter jets since the dissolution of the USSR. All of these countries are also members of the SCO, a Eurasian political, economic and military organization that also includes China, Russia and Kazakhstan.
China and Pakistan have strengthened economic military cooperation with Central Asian countries in recent years. Five years ago, Pakistan boosted its economic cooperation with Tajikistan and is currently developing a gas pipeline from Turkmenistan to Pakistan through Afghanistan. Since 2007, China has been providing military products, uniforms, loans and rail carriages to Turkmenistan, a guest attendee of the SCO, though it is unlikely to purchase the JF-17 because the country's military budget in 2014 was only US$200 million.
However, Kanwa believes China and Pakistan could still sell the JF-17 to Central Asian countries that cannot afford the jets outright through trades or loans. Like China, Pakistan has needs for natural gas and other sources of energy, and could agree to exchange JF-17 fighters in return for rights to resources in those countries, Kanwa said.
Beijing's ambitious "Belt and Road" initiative to boost connectivity and cooperation through Eurasia will likely provide many new opportunities that will increase China's flexibility in crafting a deal, Kanwa added.
 
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SCO states in Central Asia likely export targets for JF-17
Staff Reporter 2015-09-30
A JF-17 Thunder fighter on display at the Paris Air Show, June 15, 2015. (Photo/Xinhua)

China and Pakistan may target the Central Asian members of the Shanghai Cooperation Organisation as potential buyers of their jointly developed JF-17 Thunder (FC-1 Xiaolong) multi-role combat aircraft, according to the Kanwa Defense Review, a Canada-based Chinese-language military magazine.
At this year's Paris Air Show in June, it was reported that the first export order for the fighter jet — developed jointly by the Pakistan Aeronautical Complex and the Chengdu Aircraft Corporation of China — had been signed, with deliveries likely to begin in 2017. While industry experts note that manufacturers remain secretive as to the buyer, there are unconfirmed claims that deal was signed with either Myanmar or Sri Lanka.
Kanwa notes that China and Pakistan's export options for the JF-17 are essentially limited to Central Asia. West Asia and the Middle East are traditionally markets for European and American manufacturers, and no countries in these regions are likely to import the JF-17 in the near future, even though the Arab states of the Persian Gulf have all signaled plans to update their fighter fleets.
View attachment 261635
Of the former Soviet states in Central Asia, Kazakhstan is unlikely to buy JF-17s due to its close military ties to Russia, from which it recently bought a fleet of Su-30SM fighters.
That leaves countries such as Tajikistan, Uzbekistan and Kyrgyzstan, none of which have acquired new fighter jets since the dissolution of the USSR. All of these countries are also members of the SCO, a Eurasian political, economic and military organization that also includes China, Russia and Kazakhstan.
China and Pakistan have strengthened economic military cooperation with Central Asian countries in recent years. Five years ago, Pakistan boosted its economic cooperation with Tajikistan and is currently developing a gas pipeline from Turkmenistan to Pakistan through Afghanistan. Since 2007, China has been providing military products, uniforms, loans and rail carriages to Turkmenistan, a guest attendee of the SCO, though it is unlikely to purchase the JF-17 because the country's military budget in 2014 was only US$200 million.
However, Kanwa believes China and Pakistan could still sell the JF-17 to Central Asian countries that cannot afford the jets outright through trades or loans. Like China, Pakistan has needs for natural gas and other sources of energy, and could agree to exchange JF-17 fighters in return for rights to resources in those countries, Kanwa said.
Beijing's ambitious "Belt and Road" initiative to boost connectivity and cooperation through Eurasia will likely provide many new opportunities that will increase China's flexibility in crafting a deal, Kanwa added.
South African countries can also be big market and some countries in South America.
 
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Well then take it from an aeronautical engineer :p
Yaw and roll are coupled, that means you can't have one without the other. For most designs pitch isn't coupled to Yaw or roll. What this means is that the pilot has an easier time controlling pitch. He pulls the stick back, the nose pitches up. On the other hand a pilot rolls right he yaws as well and actually has to give negative rudder to just roll purely. Similarly for yawing. It is because of this that the controls for Yaw and roll feel rather "unnatural".
Hmmm...

Yaw and roll are coupled only in the sense that we want a stable coordinated turn. But when I learned to fly back in high school in a Cessna 152, I can, and have, rolled without touching the rudder pedals. Not something desirable but it was part of the lessons.

When wings are leveled, lift counteracts gravity, assuming thrust is sufficient. But when wings are not level, gravity induces yaw about the aircraft's vertical (yaw) axis. The rudder is there to counteract that effect.

On a fully manual and mechanical flight controls system, it is up to the pilot to command some yaw (rudder pedal) to make a stable coordinated turn. On a computer assisted and powered (hydraulics) FLCS, the computer does most of the work in commanding the flight control surfaces in a stable coordinated turn.

This is why it makes sense to have fbw in the lateral modes (Yaw and roll) if you are not going to have full fbw. Some of the most dangerous tendencies of the aircraft are in the lateral modes.
According to public information, the JF-17' FLCS is fully FBW in the pitch axis and conventional powered in roll and yaw.

Relaxed stability in pitch is the most important factor in making the aircraft maneuverable. That was how the F-16 was designed. For roll and yaw, the JF-17's design apparently is stable, only pitch is 'relaxed', hence the need for a full FBW system for pitch. Most people, including most pilots and even some flight control systems engineers, do not know the fact that the Wright Flyer was relaxed stability in pitch.

http://authors.library.caltech.edu/21217/1/CULaiaawfp84.pdf
What is by no means evident is the extent to which the Wrights inadvertently produced unstable aircraft. They certainly refused to follow their contemporaries who were preoccupied with the goal of inventing an intrinsically or automatically stable airplane. On the other hand, it is not necessary that an airplane be unstable to be controllable.

In fact, the Wrights did not understand stability in the precise sense that we do now.
The Wright Brothers did not set out to DELIBERATELY produce a pitch unstable design. They just happened to design one that was unstable enough to achieve flight but stable enough for the human pilot to control the aircraft.

Given what we know today, it is possible to design an aircraft that is pitch relaxed only.
 
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Thank you for the correction. While we have got you here, would you please explain the Quadruplex fly by wire and in layman terms what it means. Thanks in advance.
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Quad means 'four', obviously...

But what is not obvious is: Four of what ?

It means four channels of pitch, of roll, of yaw, and of air data.

It begs the question: Why four ?

Why not have only one set of wires from the cockpit to the FLCS computers to the flight control surfaces ?

In theory, that should work.

But, as given in post 3499 about safety, what if this one channel failed, either from combat or non-combat related reasons ?

So what General Dynamics did for the F-16, which is the pioneer for this quadruplex thingy, was that they physically replicated four channels of pitch, of roll, of yaw, and of air data, and placed them in physically distinct locations on the aircraft.

There is only one pilot control stick. But from that single source, four separate electrical signals for pitch and for roll are produced.

There is only one set of rudder pedals. But from that one set of rudder pedals, four separate electrical signals for yaw are produced.

So let us take PITCH ONLY for now...

From the cockpit, four physically separated electrical signals, aka 'channels', are routed in different paths. This is so that if one channel is damaged in any way, most likely from combat related reasons, then there are three other channels for which the FLCS computer can work with.

Quad means 'four', obviously...But why four ? Why not three or even two ?

Any EE worth his diploma can immediately answer that the moment you introduce longer wiring, more connectors, etc...etc...there will be slight differences -- impedance for example -- between channels despite them sharing the same source. So if you know and have two slightly different signals, how do you know which one is the closest to source ?

Then why not have three channels and electrically vote ? The two channels that are closest to each other will average out and we will use that signal to command pitch.

But what if one channel is damaged or electrically degraded in comparison to the the other two ? Now we are down to only two channels, which lead us back to the original problem.

This is where the concept of quadruplex (four channels) came to be and is the standard for ALL aircrafts that want the advantages of FBW and safety.

The concept is called 'two fail operability' or 'two fail redundancy' system.

Operability - Wikipedia, the free encyclopedia
...is the ability to keep an equipment, a system or a whole industrial installation in a safe and reliable functioning condition, according to pre-defined operational requirements.
In a four channels system, three are used for electrical voting with the fourth in standby.

If one channel is degraded or lost for any reason, the standby channel would be in play and we would still have three channels for voting. This is 'one fail' operability.

If one more channel is degraded or lost for any reason, we now have only two channels in operation, the voting process is eliminated and one channel is selected for primary usage. This is 'two fail' operability.

If one more channel is degraded or lost for any reason, the entire FLCS fall back to a set of pre-set signals. At this point, if the jet is still airborne, the F-16 might as well declare an in-flight emergency (IFE) and limp home. All responses to commands will be much slower than normal.

In the F-16's history, there is no known 'two fail' operation.

Now...Just in case anyone thinks I am making this stuff up...

IEEE Xplore Abstract










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Redundancy Management of Shuttle Flight Control Rate Gyroscopes and Accelerometers

The Space Shuttle Flight Control System is required to be two-fault tolerant; i.e., the system must be capable of returning to a landing site even though two system failures occur. This is referred to as fail-operational/fail-safe performance. To achieve this fault tolerance, the avionics equipment is made redundant. A redundancy management (RM) system is required to detect failures and reconfigure the avionics accordingly. This paper describes the Flight Control System (FCS) rate gyro and accelerometer redundancy management design, analysis tools and analysis results.
IEEE is a respected source.

If the 'two fail operation' concept is good enough for the Space Shuttle, it is good enough for everyone else.
 
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