In the U.S. raid this. bin Laden’s operation, a helicopter crashed, the wreckage of the plane caused by the unique shape of the attention of the outside world, some people that this is the latest U.S. stealth helicopter, or even news that China may be sought by Pakistan These debris.

stealth helicopter is actually not a new stuff, the 80s of last century the United States developed a stealth helicopter RAH-66 “Comanche”, but because changes in the situation was eventually canceled. China in recent years the research on stealth technology, has mastered the relevant technology, the latest WZ -10 helicopters also use these techniques, so even if this stuff really is a stealth helicopter is also of little value in China.

representatives stealth helicopter “Comanche”

RAH-66 is the world’s first stealth helicopter, attention to its complex shape, the goal is to improve stealth capabilities

80s of last century, taking into account the existing U.S. Army OH-58, OH-6 of these reconnaissance helicopter has become obsolete, and its range, and fire detection systems can not adapt to the deteriorating EU battlefield, so to improve the development of a new reconnaissance / attack helicopters, AH-64 form with the combat formations to improve the U.S. Army Air Corps in the anti-armor / close air support capabilities, the Army made in 1988 related to the tender system, after a review in 1991 by Boeing / West Corky aircraft joint proposal won the competition, the aircraft was named the RAH-66 “Koeman Odd “In 1993 the first prototype RAH-66 aircraft to complete critical design review through trial and, completed its first test flight in 1996, second prototype was completed in 1998 test flight.

RAH-66 was described as “the world’s first stealth” attack helicopters, RAH-66′s stealth design include use; machine Photoelectric sensor head showing the shape of the edge with an angular cheek, can eliminate the reflection of radar waves, the fuselage sides constituted by two half-plane rotation, which avoids the cylindrical fuselage radar reflectivity due to the strong, the helicopter tail boom to shore up both sides of inverted planes, can deflect radar reflection, tail ducted tail rotor tilted to the left, tail to the right tilt, so as not to cause the vertical angle, with fixed-wing airplane, helicopter inlet is also a strong reflection source , RAH-66′s two engines concealed in the body, the inlet is embedded in the fuselage, the prism and the air intake was not sharp on the radar reflection of the propeller hub and the rotor blade Ye have increased root fairing to form a smooth transition, which are not easily detected by radar, aircraft, airborne weapons are also an important source of radar reflectivity, the RAH-66 fixed-wing aircraft with stealth like design with a bomb bay, Each cabin has 6 weapons pylons, in reconnaissance missions, they can put weapons on the weapons in order to reduce aircraft cabin RCS, commonly used as helicopter gun turret is an external installation, so although can bring more fire in the community, but also increase the aircraft’s RCS, so RAH-66 of the gun can rotate 180 degrees backwards, after the contraction in the turret fairing, in addition to Arms, RAH-66 also use of retractable landing gear, thus avoiding the exposure of aircraft landing gear to the impact of RCS. The stealth design, the shape is very important, but also requires advanced materials and processes, RAH-66 in the body structure uses a lot of advanced composite materials, accounting for 50% of the overall weight of the structure, in conjunction with advanced technology and equipment to ensure control components installed in the process of tolerance, which improves the aircraft’s stealth capabilities, in addition to other radar, given that many modern short range air defense system also uses an infrared detection system, so the RAH-66 made in this regard the efforts of relatively large , including the use of belt exhaust system, each outlet has a multi-blade mixer exhaust composition, the exhaust from the fuselage to the rotor taken after the cold air intake, and follow a certain proportion with the engine exhaust hot air to mix, so that effectively reduce the temperature of the body and engine heat, so RAH-66 as a “cold,” the helicopter, in addition to radar and infrared measures, taking into account the helicopter at low altitude, low altitude flight are unique, RAH-66 is still noise, reflective and other areas to address in order to reduce the signal strength in these areas, such as rotor blades with swept design, while on the wing and the curvature of the blade designed to reduce the speed reasonable, the use of bypass type tail rotor to reduce aircraft noise, etc., in the reflective side, RAH-66 rotor with 5 leaves, glass and dark reflective coating to reduce the strength of the aircraft.

the same as fixed-wing stealth aircraft, RAH-66 uses a built-in weapons and bomb bay

after the adoption of these measures, so that all aspects of RAH-66 signal strength than the normal helicopter has been significantly reduced, according to information RAH-66′s radar cross section (RCS) is equivalent to AH -64 helicopters, 1 / 630, even if the small OH-58D helicopters, the RCS is also higher than the RAH-66 is about 250 times. In the infrared stealth capabilities, RAH-66′s infrared signal characteristics of AH-64 is only equivalent to the 1 / 5, OH-58D 1 / 3, also in the acoustic detection of lower than about half of the two helicopters.

stealth helicopter, Aka Adams sulfur heel

Although the RAH-66 stealth capability in the visible progress, but the Army is still in the beginning of this century to give up, public reason is that the aircraft is in Cold War brewing, so the battle with its intended dissolution of the Soviet Union ceased to exist, although the use of a large number of stealth tactics allowed to have advanced technical indicators, but also caused the aircraft’s soaring costs and prices has been from the initial $ 25,000,000, up to 5,000 million U.S. dollars, almost doubled, but the author is speaking from the root cause of this whole stealth helicopters and fixed-wing aircraft not made as cost effective.

for the helicopter, there is no stealth design, all with good stealth capability

us that radar detection range and target RCS, receiver sensitivity, antenna parameters such as pore size and transmitter power on, so stealth aircraft need to reduce as much as possible their own RCS, to reduce the radar detection range of each other, is more for non-stealth aircraft The approach taken by low-level penetration of radar detection but also to avoid each other, this tactic is mainly because the terrain and weather conditions of low complexity, there is more clutter interference, which would reduce the sensitivity of each receiver, will reduce the radar detection range, low altitude penetration also involves another reason is that the radar distance wireless TV, radar, now we know that the main work in the microwave band, so the wave is basically a straight line, even though the band can also be reflected in the atmosphere by means of waveguide ultra-horizon detection, but because these means for the technology and weather, the environment are higher, and therefore improve the general level of radar is relatively limited, the radar line of sight of the basic formula; 130 kilometers (square root of the diameter of Earth, where taking into account radio refraction and other factors, so the actual data to a large number of) * the square root of the radar antenna height and target height of the square root, that is, when the target height of 9,000 meters when the ground radar horizon at 400 km, when the target altitude down to 1000 meters, the ground radar to reduce the 130 km line of sight, but there are many low-altitude penetration limitations, such as the dense air at low altitude, the air resistance, affect the flight, but also the range of airborne weapons, there is a low-altitude terrain, weather complex, with highly limited, so once the plane failure and other conditions, so no time to dispose of, together with the development of the modern early-warning aircraft, the radar horizon effectively improve and enhance the detection capability at low altitude, so the more modern non-stealth aircraft Standoff use more stealth attack on the target system to improve the combat ability, so the largest value of stealth technology is to allow the aircraft to return to high altitude, relatively thin in the upper atmosphere, air resistance, easier to achieve supersonic cruise, while the delivery of airborne weapons distance increased, the height increases, the increase in the radar line of sight will help improve the radar detection range.

for stealth helicopter, the rotor is Aka Adams sulfur heel

for the helicopter which is not much help benefits, the first helicopter already in the low-altitude and low altitude activities, for the low-flying helicopters, can effectively reduce the other side of the radar line of sight, and cover with complex ground clutter, but also reduce the target signal is the probability of radar receiver , and for the air early warning aircraft, its principle is the use of Doppler detection efficiency goals, that is, by measuring the echo Doppler frequency, the movement of the target and non-sports ground and sea separately, due to the Doppler effect and the target is proportional to the radial velocity, so when the target radial velocity is 0, the radar can not detect the target, while a feature is the ability to hover the helicopter does not move, so to avoid each other radar detection, so now for the helicopter detection is the use of its main rotor, which means that although the helicopter can hover, but the rotor was spinning, so it’s back to the Doppler frequency difference between the ground there, so is the use of modern radar to detect the difference helicopter, so we can see whether it is for a helicopter with stealth technology have generally found it very difficult radar, regardless of how much a helicopter with stealth technology, it can not prevent the rotor from the rotation, so the radar can also by detecting the approach to determining the helicopter rotor position. From here we can actually see the helicopter, it can take certain measures to reduce its RCS, but the principle of the helicopter determines its own fixed-wing aircraft can not be as stealthy as to achieve higher capacity, which is why the RAH- 66 did not produce the desired benefit-cost ratio of the root causes. Actually used from a few U.S. special forces such as MH-47E helicopters and MH-60K, these aircraft are equipped with FLIR and terrain following radar detection system, with the terrain following, regression to avoid the capacity, so have a good super- low-flying capabilities, including early-warning radar in fact generally difficult to find, do not rule out new variants of these aircraft could use some technology to further enhance the aircraft’s stealth capabilities, but like the RAH-66 helicopter as the possibility of full stealth estimation large.

use of U.S. special forces MH-60K helicopters, equipped with terrain following radar and forward-looking red detection systems

of the use of stealth technology helicopter

from the 80 years since the last century, China will focus on technology as a stealth technology to track and research, to the beginning of this century great progress has been made, has been the design of weapons and equipment is widely used, such as China’s new gun, ships have used stealth technology, like O22 missile boats, new offshore frigate is a more comprehensive use of stealth technology and greatly reduce the RCS, this year’s F -20 aircraft flight test is the field of stealth technology on behalf of our country into the world, while our helicopters have also been some stealth design exploration and use of, for example increased in the new helicopters the use of composite materials, in particular, be pointed out that China’s new armed helicopters WZ -10 used a number of stealth technology, represents the highest level of stealth helicopter, from the point of view related images, WZ -10 there is a significant body line, suggesting that Its body and RAH-66, is constituted by two inclined planes, so is mainly to deal with the side of the radar, the helicopter, its side of the largest cross-sectional area, and the general threat of the side at 30 degrees, So let light by tilting the body to deviate from their exposure to the direction of the radar waves, thus reducing the radar of the RCS, the author also notes that other weapons such as direct -10 inlet like the RAH-66 is the use of embedded, the outer mask has fairing, together with a smooth body, thus effectively reducing the inlet RCS, thus eliminating the helicopter radar reflection of a strong source, in addition to the engine can not see clearly the vents, indicating that the aircraft is also equipped with infrared suppression system, the engine exhaust gas temperature before mixing with the cooling air discharge, thereby reducing the aircraft’s infrared signal strength, the other can see the stealth measures include the use of multi-leaf blade, and plate glass to reduce helicopter noise intensity, That is for the present, for the development of a type of stealth helicopter is much difficulty did not exist, nothing more than that the helicopter is not much it cost effective.

WZ -10 of more stealth technology used, pay attention to the fuselage and engine

This photo clearly shows WZ -10 stealth airframe design.

highest towers begin from the ground

whenever significant in some areas of China results, the western media always heard “theft”, said the most obvious is with the F-117 F -20 links, in my view, this in addition to that some in the West’s “Pride and Prejudice” They do not have other meanings, to stealth technology as an example it is a combination of electromagnetic, aerodynamic, materials, electronics and other areas of the comprehensive course, no longer based on relevant research in the field could not be achieved simply too big breakthrough, only target RCS measurements is very difficult, requiring as much as possible to eliminate residual radiation on the back of RCS aircraft itself the “pollution”, which is the need to test the smooth interior of the ground as possible, but must cover the inner wall of high-quality radar absorbing materials If no relevant basic research and facilities, even to a country full F-22 drawings, materials and production lines, it can not produce the original standard F-22.

are anechoic chamber tests of the F-35 fighter

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Note:

References:

1, the world’s helicopter manual

2, article with pictures from the Internet, rights to original author

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