China miliary plane design

Tailless delta was something the US and the Russians abandoned early. Problem with a tailless delta is that you have two wing control surfaces doubling as ailerons (roll control) and elevators (pitch control).

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The tailless delta desisn has indeed not widely been adopted by the US and Russian aircraft manufacturers.

But the usage of elevons in the tailless delta-winged design is a compulsion, and not a technical difficulty. Due to the tail's absence, the entire wing must perform the function of the elevator and the airelons.

Once you go turning deeper into a circle or continue to maneuver after successive maneuvers, the plane easily loses bleeds speed. Again that is due to the unassisted delta wings. This is something rectified with canards, double delta or cranked delta designs.

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The above statement is accurate. The loss of speed is due to the high drag that is generated by the large surface of the delta-wing.

One may imagine negotiating underwater current, with a membrane of skin joining our palms to our thigh. The arms are swept backward at an angle.
Upon bending one arm against a strong current, we may turn (or topple) instantaneously, but there is significant reduction in the forward speed.

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The delta wing is indeed the final evolution from the perpendicular wings of aircraft of WW2. Post war, gain in speed was important, and thus wings were swept backward, but were "cut-short" and joined in a perpendicular to the fuselage. Examples are the F-16, and MiG-29.

Later, the wing was allowed to be swept upto the tail, thus removing it. This was the pure delta wing (F-106). Later, it was cranked (XB-70 Valkyrie), canards were added (Valkyrie), cropped (Mirage-2000), compounded (SAAB Draken), compounded, cranked and cropped (LCA), canards in addition to crop (Rafale, Eurofighter, J-10).

The functions of canards in the case of the XB-70 Valkyrie are as follows :-

"The canard design enabled the foreplane to be used to assist with trimming the aircraft across a wide speed range from a minimum 150 kts. (278 km/h) landing speed, up to Mach 3; they could also serve as flaps."

Source:


Canards are now present on most modern aircraft such as the Gripen, Rafale, Eurofighter and the J-10.
However, canards are also known to have disadvantages such as increasing the interference drag.

Added 1 day later : The part about compression lift of the XB-70, that was quoted by me was incorrectly attributed to the usage of canards, partly due to my lack of knowledge about the term. I assumed that the shockwaves were generated by the canards. I investigated more about this term in search for Sumdud's query on it.

Chinese Industry Gains from Foreign Concepts

Just to follow-up on an old question:

eecsmaster said:

in other words, Pakistan. Who else operates F-16s and are on good footings with the Chinese?

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I think that everyone by now has heard the rumor that Pakistan provided China with access to the F-16. This is the most likely scenario.

There have also been rumors, however, that Egypt (which like Pakistan flies both US and Chinese warplanes) provided China with access to the F-16.

This rumor may or may not have merit. However, Egypt is also widely reported to have provided China with access to a MiG-23 back in the 1970s. Technology gained from this exchange reportedly influenced the redesign of the J-8 II inlents.

One thing I might add is that some delta designs like the Mirage III and 2000 have very low wing loading which enables them to instantaneously turn quickly. The F-102 Delta Dagger and the F-106 Delta Dart also has similar characteristics. Despite the similarity of the Delta Dagger and the Delta Dart, the wings are completely different; the Dagger uses outboard wing fences, the Dart uses a more modern leading edge slats.

However, the delta quickly gathers drag in the middle of the turn as it gains alpha, so it bleeds speed and lift. Thus it is not good for sustained turn rate. When Boyd's theories came to the fore in the USAF, it placed more emphasis in sustained turn performance. Somehow the French didn't get the message as quickly, leading to the Mirage 2000.

I gather the J-8I and J-8II should perform similarly with their low wing loading. It can do one or two quick turns before air speed drops off.

As the deltas are clipped in the J-8I/J-8II I suspect the plane has a fast roll, but because of the plane's length might have some potential yaw problems. The J-8II's larger ventral stabilizer and large tail seems like a better counter to that.

Low wing loading makes a plane buffet at low altitudes. Thus, the flight of such low wing loading jets are much better at high altitudes.

The MiG-21 evolved from a low wing loading jet in its early version to a high wing loading plane in the last versions. During its evolution it picked up power and weight, but the wings remained the same. In the case of a plane like the MiG-21bis, the instantaneous turn rate would suffer at higher altitudes but at lower altitudes, the plane is more stable and has a smoother ride. As you might suspect, planes that have a ground attack role is better to have a higher wing loading to get a smoother flight in low altitudes.

The J-7s except for the MiG-21MF based J-7C and -D, retain the original design of the MiG-21, and thus the wing loading remains nearly the same as the original. The J-7E gained some weight but did add more wing area to it so it all evens out.

Low wing loading makes a plane buffet at low altitudes. Thus, the flight of such low wing loading jets are much better at high altitudes.

The MiG-21 evolved from a low wing loading jet in its early version to a high wing loading plane in the last versions. During its evolution it picked up power and weight, but the wings remained the same. In the case of a plane like the MiG-21bis, the instantaneous turn rate would suffer at higher altitudes but at lower altitudes, the plane is more stable and has a smoother ride. As you might suspect, planes that have a ground attack role is better to have a higher wing loading to get a smoother flight in low altitudes.

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How does a low wing-loading plane (more manuverable) make an easier flight?
Isn't manuverability on the ground even more important? A smoother, less manuverable flight can spell disaster for the plane would it? A ground attack plane carries more because it takes more to destroy a building than a jet.

With lower wing loading, you get more lift for the same speed and that translates to better maneuverability. This lift becomes more precious at higher altitudes and low wing loading is a necessity for planes performing at higher altitudes.

A higher wing loading on the other hand smooths out the plane's ride, and that helps in situations like dives, or flying in low altitudes preparing for a bomb run. A true multirole aircraft has to find a proper balance between these two attributes.

Note fighters from World War II.

Spitfire and Zero both have low wing loading. They are very agile, and can quickly turn in tight circles. Other planes falling into this category are Russian fighters like the LaGG and Yakolev series, and just about every Japanese fighter except for the Shoki.

Fighters like the Me-109, FW-190 and the P-47 Thunderbolt have high wing loading. They can dive extremely fast and deliver accurate ground attacks. Other fighters along this line are the P-36 Airacobras and the P-40 Warhawks.