Wang Mingsen Lei Zhu Li Rui
At the beginning of the year, according to the Israeli Ministry of Defense, Israel will purchase two KC-46A "Pegasus" new-generation aerial tankers manufactured by Boeing to enhance the long-range strike capability of the Air Force.
As a special aircraft that replenishes fuel for other aircraft in flight, aerial refueling aircraft plays an irreplaceable role in modern warfare, and has always been one of the main battle equipment developed by the air forces of various countries.
Its outstanding performance in increasing the fighter's range, endurance and effective load has won the reputation of "air power multiplier" and has become one of the important symbols to measure a country's long-range air combat capability.
The romantic "Kiss in the Sky" requires superb driving and manipulation behind it, and also requires sophisticated manufacturing technology.
Previously, Israel had signed a military purchase contract with the United States to purchase 8 KC-46A aerial tankers, but due to Boeing's continuous "small problems" in the manufacturing process, the delivery date was repeatedly delayed.
This is also enough to see that making an aerial tanker is not an easy task.
Compared with general large aircraft, aerial refueling aircrafts have both a large fuel capacity and high economy, and the technical difficulty of aerial refueling is even greater, all of which pose challenges to the manufacture of aerial refueling aircraft.
"Turn Around" Upgrade: A Road Full of Difficult Modifications
At present, many countries around the world have equipped air tankers, but most of them rely on purchasing products from other countries, and very few countries can independently manufacture air tankers.
As an indispensable member of modern air force weapons and equipment, air tankers are mostly modified from transport planes, bombers and even civil aviation airliners.
This undoubtedly raises the threshold for manufacturing air tankers for countries that lack the technology to develop large aircraft.
Owning a large aircraft does not mean that an aerial tanker can be manufactured. How to achieve this difficult leap is full of various technical challenges.
In order to meet the special functional requirements of the tanker, it is generally necessary to restructure the original platform.
From the perspective of the internal structure, it is mainly to adjust the layout of the fuel tank and cargo hold to meet the fuel load requirements to the greatest extent.
From the perspective of the external structure, the tanker also needs to install corresponding refueling devices at the tail and wings to realize the connection with the fuel tank in the fuselage.
Initially, the development of tankers in various countries used bombers as the main platform.
At the end of World War II, the United States upgraded the B-29 bomber.
Use it as a tanker and put it into action.
The United Kingdom used the "Victor" bomber as a platform for the modification of the tanker.
The early Soviet tankers also started with Tu-16 and Mia-4 bombers.
Due to the limited load of these aircraft and their use of turbojet engines with high fuel consumption, it is difficult to provide a large air fuel supply capacity.
To develop a more practical aerial tanker, a modified platform with stronger load capacity and larger internal space is urgently needed.
The mature large passenger aircraft has quickly become a new choice for Western countries to refit air tankers due to its advantages of low cruising fuel consumption, convenient maintenance and guarantee, and excellent multi-purpose potential.
Relying on multi-model Airbus aircraft, France has become a powerhouse in the research and development of aerial refueling aircraft.
Compared with large military aircraft such as bombers, it is more difficult to convert civil airliners into tankers.
While pursuing fuel economy and long-range performance, civil aviation aircraft have to sacrifice such factors as rolling distance, maneuverability, flight speed adaptation range, airflow interference resistance, and damage resistance of the main body.
In the process of refitting the tanker, people must make reasonable improvements to these performances in order to finally refit a tanker.
In addition, the cumbersome modification process is also a major technical challenge.
In addition to the conventional installation of refueling equipment and fuel tanks, re-routing the circuit and improving communication equipment according to military standards is also a "trouble" that should not be underestimated.
According to reports, Airbus will need to install about 16,000 new components and about 450 new electrical wiring harnesses, as well as 6,000 brackets and 1,700 connectors in the process of converting the A330 airliner into a multi-purpose aerial tanker.
In fact, once the tanker has been modified to "join the ranks", it must also consider its own configuration in combination with the actual battlefield.
In addition to using more advanced airborne equipment and refueling devices, Russia's Il-78M-90A is also specially equipped with the L370 "Vitebosk" airborne active defense system, which can effectively deal with threats from infrared and laser-guided missiles.
All of these technologies increase the difficulty of manufacturing an advanced aerial tanker.
"Kiss in the Sky": A Hidden Thrilling Romance
When did the technology of aerial refueling appear?
As early as the first aircraft came out, people began to imagine various ways to refuel without landing.
In 1923, the United States achieved the first real aerial refueling.
A single-engine DH-4B aircraft of the U.S. Army was refueled twice in flight by another aircraft of the same type in the way of artesian hose flow, thus opening a new chapter in the history of aerial refueling.
Of course, the whole process requires someone to hold the hose with both hands, and the difficulty of the operation is equivalent to an "aerial acrobatics".
In the 1930s, air refueling technology has developed to a certain extent, and the United States, the Soviet Union and other countries have developed corresponding airborne air refueling equipment.
During World War II, aerial refueling technology began to be used in actual combat.
Many Allied bombers carried out long-range raids on the German mainland by refueling in the air over the Atlantic Ocean.
At present, there are mainly two types of aerial refueling technologies that are relatively mature and widely used: the hose-floating anchor refueling scheme and the flying boom refueling scheme (also known as the hard refueling scheme).
The hose-floating anchor refueling solution was developed by the British Air Refueling Company in the 1940s and is the most widely used aerial refueling technology.
Using this method for aerial refueling, the oil receiving aircraft only needs to install an oil receiving pipe on the nose or the leading edge of the wing, and the refueling equipment of the tanker is composed of a winch, a hose and a funnel-type floating anchor.
The floating anchor is equipped with a mechanical self-locking device. When the oil receiving pipe extends into the floating anchor, the floating anchor will automatically lock the oil receiving pipe mouth to connect it with the oil delivery hose to complete the refueling work.
Due to its simple structure and easy disassembly and assembly, a large tanker can be installed with several sets of soft refueling equipment, so as to refuel multiple fighters at the same time. The flexible hose connection also improves the safety of the tanker and the oil receiver when they move relative to each other. sex.
However, the shortcomings of soft refueling are also very prominent: it is greatly affected by gas turbulence, the connection is more difficult, and the pilot's operating skills are higher; the pressure bearing capacity of the oil hose is limited, and the oil delivery speed is slow, so large military aircraft are refueled. requires longer working time.
The fly-beam refueling scheme is more complicated than the hose-floating anchor refueling scheme.
Generally, a refueling stringer composed of two rigid telescopic tubes and an operator control cabin should be installed at the rear of the tanker.
When refueling in the air, the tanker extends the refueling truss, and when the oil receiver approaches, the operator in the control cabin controls the refueling truss to align with the refueling hole of the receiver, thereby effectively completing the connection of the oil pipes.
Hard refueling can use pressurized equipment to improve the oil delivery speed, higher oil delivery efficiency, and better equipment stability and controllability.
Tankers with hard refueling equipment can only refuel one fighter at a time and require professionally trained refueling operators.
Modern aerial refueling technology has made great progress in refueling speed, reliability, and refueling volume, but the thrill of refueling is almost the same as in the early days.
Refueling in the air, a seemingly gorgeous "kiss in the sky", there are still countless risks hidden behind it.
In 2018, a U.S. Navy F18 collided with a KC-130J tanker during refueling, resulting in the crash of the two planes and heavy casualties among the crew members.
In 2019, an F35C in the United States rubbed against the oil pipeline during the refueling process, causing the taper sleeve of the oil receiving pipe to be damaged, and the parts were also sucked into the air intake, causing serious damage to the F35C engine.
In addition, the aerial tanker also involves a number of key technologies.
For example, in order to realize "automatic oil delivery after docking" and "automatic oil disconnection" during the aerial refueling process, the mechanical structure of the refueling floating anchor and the oil receiving pipe must be very reliable in design.
The oil delivery speed of hard pipe refueling is generally as high as more than 4,000 liters per minute, but the research and development is difficult, and it is still a difficulty that many countries need to break through.
Bright future: a powerful "voyage station"
Over the course of a hundred years, aerial refueling technology has developed from single-plane refueling to formation refueling between 30-50 aircraft, from daytime refueling to nighttime refueling, and from general weather conditions to complex weather conditions.
With the continuous application of various new technologies, the new generation of aerial refueling aircraft will also become a more reliable "distance travel station" for various types of fighter aircraft.
Air refueling capability has been enhanced in all aspects.
As a core indicator, aerial refueling capability has always been the primary consideration for countries to build aerial refueling aircraft.
On the one hand, countries generally choose aircraft with large carrying capacity as new aerial refueling platforms to enhance fuel supply capacity; on the other hand, countries are constantly developing refueling systems with higher refueling rates to improve refueling efficiency.
Take the A330MRTT developed by Airbus as an example. The aircraft also has 3 air refueling ports of type 2. Among them, the hose refueler can achieve 1590 liters/min refueling operation, and the hard tube refueler can deliver fuel up to 4540 liters/min. It can better meet the various oil receiving needs of multiple models.
Multi-field expansion of execution task types.
As an important support and support platform, air tanker has been paid more and more attention to its economical intensification.
Judging from the KC-767 and A330MRTT air tankers, the future air tankers should have the ability to perform a variety of tasks, taking into account the transportation needs of fuel, cargo and soldiers.
Especially when there is a shortage of strategic airlift forces, tankers with both airlift capabilities can effectively reduce the pressure on the Air Force's strategic transport fleet.
In addition, by installing sensors, tactical data links, communication gateways and other equipment, air tankers can also have some functions as early warning aircraft and electronic warfare aircraft, becoming an information node in the networked battlefield environment, providing information support for friendly aircraft.
The level of informatization continues to improve.
The high informatization of airborne equipment has become an inevitable trend for countries to develop aerial tankers.
In September last year, a foreign company announced the newly developed LMXT tanker program.
The plan shows that LMXT inherits the air-to-air refueling capability of the fully automatic boom system of Airbus A330MRTT, applies the fly-by-wire joystick technology, and is equipped with an open architecture system based on joint global command and control.
The continuous improvement of informatization and intelligence is conducive to better completion of combat tasks, the integration and utilization of resources, and the interconnection between tankers and other combat units in the wide-area battlefield space.
At the same time, the development of air tankers in terms of defense and stealth also provides a guarantee for them to better perform refueling tasks.
Air tankers have always been the target of enemy attacks. Therefore, countries are trying to take various protective measures to enhance the self-protection capabilities of air tankers.
When the KC-46A tanker was manufactured, it was equipped with a radar warning receiver, electromagnetic pulse protection, and infrared countermeasure equipment, which shows its survivability on the battlefield.
In addition, through the design of the appearance of the air tanker wing, combined with low observable features and camouflage marks, it is also intended to pursue the "stealth" effect and reduce the probability of being attacked.