Special written by The Paper Wang Ruohong
At the South Korean Defense Industry Expo held recently, South Korea KAI Company launched the KF-21N, the carrier-based model of the KF-21 fighter , for the first time, to its grandfather, and it is a catapulted version of the fixed-wing carrier-based fighter.
KAI's move to develop carrier-based fighter does confuse the author: at the 2021 South Korea International Maritime Defense Industry Exhibition, the two Korean shipbuilding giants, Hyundai Heavy Industry and Daewoo Shipbuilding, have demonstrated the design scheme model for bidding for the South Korean Navy CVX aircraft carrier project for the first time, and neither is equipped with catapult , and there is no funding for the CVX aircraft carrier project in South Korea's 2023 fiscal year announced in August 2022.
When the prospects for domestic aircraft carrier projects are still unclear, why should KAI be eager to launch the KF-21N carrier-based fighter? Compared with the KF-21 land-based fighter, what improvements have the KF-21N made?
South Korea displays the KF-21N carrier-based fighter model.
The real intention of South Korea to develop carrier-based aircraft
Hyundai Heavy Industry and Daewoo Shipbuilding in 2021 Although the design model of the CVX aircraft carrier project displayed by Hyundai Heavy Industry and Daewoo Shipbuilding in 2021 adopts different flight deck designs, the former is a ski jump flight deck and the latter is a straight flight deck, but neither is equipped with catapults. Therefore, the two companies displayed the F-35B vertical take-off and landing stealth fighter on the flight deck at that time. Through testing and deployment on the US Navy's amphibious assault ship , the F-35B fighter can take off from the straight deck without the help of a catapult. If you take off on the ski jump flight deck, you can further increase the takeoff weight.
From a technical perspective, the South Korean Navy purchased F-35B fighter jets from the United States and deployed them on future CVX aircraft carriers. Whether it is the Hyundai Heavy Industry solution or the Daewoo shipbuilding solution, it is not a problem. However, the several inherent defects and shortcomings of this type of fighter jet have made it highly criticized in South Korea. For example, F-35B is the most complex and most expensive model among the three models of the F-35 family. While the cost of the F-35A has generally dropped to around US$80 million, the cost of the F-35B remains above US$100 million. This is still the purchase price within the US military, and South Korea's purchase price will only be higher. The complex structural design of
F-35B also increases the difficulty of maintenance. Whether it is the deflectable tail nozzle or the lift fan with a huge volume at the rear of the cockpit, it requires long-term careful maintenance. If the tail nozzle or lift fan fails during takeoff and landing, it may cause the plane to be destroyed and people to die. In addition, during short-range takeoff, the ammunition load and fuel volume of the F-35B fighter are limited. Although the use of a ski-jump flight deck can increase the takeoff weight, it still cannot be compared with the ejection takeoff carrier-based aircraft. When landing vertically, it is also stipulated that the F-35B fighter should not be too heavy. In many cases, a pilot must consume a considerable portion of the fuel to achieve vertical landing. In addition, since the lift fan occupies a large part of the space inside the aircraft, the F-35B fighter's oil carrying capacity is much less than that of the other two models, and the combat radius is greatly shortened.
KF-21N carrier-based aircraft uses folding wings to reduce the area occupied by parking on the flight deck and hangar.
, and what makes Koreans the most headache is the password lock problem of the export version of F-35 fighter. According to South Korean media reports, before each flight mission, the F-35A fighter , which is currently in service in the South Korean Air Force, must first connect to the Link16 data link network to obtain the password granted by the US so that the flight control system can work normally. Otherwise, the F-35A fighter can only "stay" on the ground. It is said that the United States has this "backdoor" on all exported F-35 fighters, mainly to guard against the so-called "allies" such as South Korea, Japan and Europe, one day, they will use this US-made stealth fighter to deal with the United States itself. Therefore, in theory, the United States can monitor every exported F-35 fighter connected to the Link16 data link network and control it through the reserved backdoor.
Even if the South Korean Air Force complains, it is helpless. After all, the F-35 is the only high-performance stealth fighter that can be purchased in the country. However, for the South Korean Navy, if the F-35B that also purchases the F-35 family, there is no doubt that it will encounter the same problems as the South Korean Air Force. The special requirements for maritime operations are simply impossible to allow the South Korean Navy to accept the conditions that must first unlock the lock with the password provided by the US. Coupled with several other shortcomings and defects of the F-35B fighter, the South Korean Navy hopes to have a carrier-based fighter that has the final say and has a higher cost-effectiveness. In order to meet this demand of the South Korean Navy, KAI proposed the KF-21N carrier-based fighter jet developed from the KF-21 to replace the F-35B fighter jet purchased from the United States. Moreover, based on land-based fighter jets, improving the development of carrier-based fighter jets is also a common practice in most countries.
The domestic aircraft carrier model displayed by the Korean shipyard.
Technical threshold from land-based to ship-based
At present, almost all carrier-based fighters in service in various countries have developed from land-based fighters, but the specific practices are different. The original prototype of the US F/A-18 series carrier-based fighter was the YF-17 land-based fighter that failed to bid with the YF-16, but the design changes from the YF-17 to the F/A-18 are quite large and can be regarded as two different fighters, . The US F-35B/C and French Rafale M carrier-based fighter jets were developed almost at the same time, adopting the "one aircraft, two types" model. The Soviet-Russian Su-33 and MiG-29K first had the basic models of land-based fighter jets, and then improved and developed based on this. No matter which model is adopted, the improvement of carrier-based fighter jets compared to land-based fighter jets is quite large in view of the special requirements of takeoff, landing and maritime combat deployment. First of all, from the perspective of fuselage design, the main structure of a carrier-based fighter must further increase its strength in order to withstand the huge impact force during ships and the powerful pulling force generated when using a tail hook to blocking cable . The main bearing structure of the front landing gear and the main landing gear must also be enhanced, especially the front landing gear, which generally adopts a dual-wheel design. If it is a ejection and takeoff, the front landing gear must be further strengthened and a towing rod must be installed.
The main wing of a carrier-based fighter usually needs to increase the wingspan compared to land-based fighter jets, mainly to increase lift and reduce landing speed. At the same time, in order to save the area occupied by parking on the flight deck and hangar, the main wing must also be equipped with a fully automatic folding/expanding mechanism. Of course, there are exceptional models for folding wing designs. For example, the famous F-14 carrier-based fighter does not have folded wings, but uses its unique swept wing design to reduce the footprint. Among several current carrier-based fighters in the world, the F-35B and Rafale M also do not have folded wings. The F-35B itself can use the power system to increase and increase during takeoff, so its wingspan is the same as the F-35A, both of which are 10.7 meters, while the F-35C has increased to 13.1 meters, and it uses folding wings. Although the Rafale M also maintains the same 10.8-meter wingspan as the land-based fighter, the aircraft can use the body-decapital vortex generated by the canard wing to increase the main wing, so its take-off and landing performance is also good.
KF-21 wings are equipped with missile using ram engine , which should be an supersonic anti-ship missile .
In addition, due to long-term deployment of maritime operations, carrier-based fighters must also take protective measures against salt spray corrosion, while land-based fighters usually deployed at inland airports basically do not consider this design. Coupled with the previous improvement projects, the air weight of carrier-based fighters generally increases a lot compared to land-based fighters, basically at a level of hundreds of kilograms. Therefore, carrier-based fighters must also consider urging-increased turbofan engines with greater thrust in the power system, so as to ensure that the flight performance will not decrease compared to land-based fighters.
It can be said that the technical threshold for carrier-based fighter jets is very high. There are many countries in the world that can develop fighter jets, but there are still only a handful of countries that can develop carrier-based fighter jets with advanced performance.The UK and Swedish once proposed the ship-based models of "Typhoon" and " Gripen ", but they were both at the stage of imagination. So, is the KF-21N carrier-based fighter jet designed by South Korea, which is not very strong in the aviation industry, reliable?
The future of "Falcon" going into the sea is uncertain
Judging from the KF-21N model disclosed by South Korea's KAI company this time, it does follow the above several improvement projects of carrier-based fighter jets. For example, the KF-21N has further increased its appearance size and wingspan compared to the KF-21, with a total length increased from 16.9 meters to 17.1 meters, a height increased from 4.7 meters to 5.2 meters (mainly because the height of the landing gear has been increased to facilitate takeoff and lifting and landing buffering), and its wingspan has increased from 11.2 meters to 12.3 meters. In terms of maximum take-off weight and payload, the KF-21N is basically the same as the KF-21, but the maximum flight speed has dropped from Mach 2.0 to Mach 1.6. This is mainly because the body's empty weight is increased, and the turbofan engine used is still F414-GE-400K, so its flight performance will inevitably decline. The
KF-21 fighter has successfully made its first flight and is named "Falcon".
In the specific details of the KF-21N, the improvement projects carried out are basically the same as those of carrier-based fighters in other countries, including strengthening the main landing gear and front landing gear, adding a fully automatic folding/display mechanism on the outer wing sections, and installing a retractable tail hook under the rear fuselage between the two engines. In addition, on the airborne weapon, the KF-21N also carries two unknown models of supersonic stamped anti-ship missiles in the middle of the wing. In addition, the design layout of the KF-21N is almost exactly the same as that of the KF-21, including 4 "Meteor" medium-range air-to-air missiles, which are still mounted on the semi-buried mount on the belly of the aircraft.
Overall, the flight performance of KF-21N is relatively mediocre compared with the models in other countries, and it does not have complete stealth ability, so it does not have great technical advantages compared to models such as F/A-18 and "Gust" M. More importantly, even if the South Korean Navy wants to have an medium-sized aircraft carrier with about 60,000 tons with catapult capability, how can it be obtained? At least at present, the electromagnetic catapult on the US Navy's Ford aircraft carrier still has defects such as high failure rate and poor reliability. Whether the South Korean Navy accepts it is still a question. Therefore, the future fate of the KF-21N is still unclear.
Senior editor of this issue Xingtan
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