Obviously, before landing a helicopter on the battlefield, it is required to suppress the enemy’s firepower so that he cannot attack the stationary vehicle. In the mid-sixties, shortly after the entry of the American army into the Vietnam War, an original proposal emerged concerning the protection of helicopters during landing and take-off from the battlefield. Helicopters should be equipped with a special multi-barreled system - a kind of “machine gun” capable of carrying out a massive salvo and crushing the enemy, literally covering him with a hail of bullets.
Split layout of a separate module XM215
A new helicopter protection system project was launched in 1968 year. In mid-November, the Pentagon signed a contract with MRC Corporation. The subject of the agreement, which cost a little more than 202,5 thousand dollars, was the development of a finished product suitable for use by the troops. The work was carried out under the supervision and with the participation of specialists of the military department. The program as a whole was called Suppressive Fire Weapon System for Helicopters - “Helicopter weapon system for fire suppression”.
The project received the working designation Multiple Barrel Gun XM215 - "Multiple weapon type XM215". Also, the finished product was often named after the project name, including using the abbreviations MBG and SFWSH.
At the request of the military, a promising product was supposed to suppress the activity of the enemy in a large sector in front of the helicopter. In fact, it was required to “clean out” the area from potentially dangerous objects as soon as possible. In addition, the system should have a minimum size and weight, not depriving the carrier of the stock of carrying capacity. It was obvious that it would not be possible to fulfill such requirements with the use of standard weapons and proven developments. In this regard, the company MRC has proposed a completely new solution based on unusual ideas.
To protect the helicopter landing, it was proposed to use a multi-barreled machine gun with the highest rate of fire. Differing in relative simplicity, such a weapon installation could in the shortest possible time fall asleep the enemy with a huge number of bullets and show efficiency, at least, not worse than the existing machine guns of the classical appearance. Some features of the design of the future system XM215 allowed to obtain certain advantages over alternative weapons.
By mid-1969, MRC Corporation completed the design of a new security system. A set of design documentation was handed over to production, and soon the first prototype of the XM215 product went to the landfill. Subsequently, taking into account the experience of testing and inspections, the development company manufactured several more experienced "machine guns" for aviation technicians. All of them, in general, had a similar design, but differed in certain features.
The main element of the XM215 MPG helicopter was a multi-barreled weapon module. It was based on a curved metal plate; it served as a shutter, and also accommodated a large number of separate triggers with electric control. On the plate was fixed a large cage with a lot of holes for barrels. The bending of the slab and the shape of the cage were determined in such a way that the trunks were divorced in different directions at small angles. Due to this, it was proposed to ensure the dispersion of bullets when firing.
The barrel was a tube caliber 5,56 mm (.22) with a length of just 2 inch (50,8 mm), half of which served as the chamber. Each of the modules of the XM215 system used 306 trunks. They were located in the cage, forming a kind of cellular structure consisting of 17 horizontal rows with 18 or 19 trunks in each. At the same time, some cells of such “cells” were given not under the trunks, but under the fastenings of the clip to the main plate.
As part of the protection system, it was proposed to include four modules as standard. They were to be mounted on a special frame, suspended from the helicopter carrier. The frame was designed in such a way that the two upper modules were located at some distance from each other, and the lower ones were placed side by side. It was proposed to install all four modules at certain angles to the axis of the helicopter. They were bred to the side and slightly tilted down.
A small breeding of the trunks and the special installation of the four modules allowed the MRC engineers to get a fairly large lesion sector. The bullets had to fly through a horizontal sector 40 ° wide — 20 ° right and left from the XM215 MBG axis. The width of the vertical sector overlapped by the trunks was determined at the level of 15 °. It was assumed that the system will be mounted with an inclination forward, and due to this, the helicopter will be able to fire at targets in the forward hemisphere beneath.
"Multi-barreled machine gun" in combat configuration. Four separate modules mounted on a common frame.
The authors of the project XM215 faced restrictions on the mass, and therefore the system had to use not the largest and heaviest ammunition. For her chosen cartridge M24. It was a modified version of the popular .22 Long Rifle (5,56x15 mm R), distinguished by a tombpack bullet. The technical and combat characteristics of the two rounds did not differ much. It should be noted that the M24 was taken to supply the US Air Force and was originally used with survival rifles that were part of the emergency stock of pilots. Perhaps this circumstance in the future could simplify the supply of ammunition parts.
The Multiple Barrel Gun / Suppressive Fire Weapon System for Helicopters project provided for the use of a special fire control system capable of providing several firing modes with different results. Control over the operation of the modules was provided by the console located in the helicopter cabin. It had fire control and mode selection options. Naturally, there was a manual fuse, which allowed to exclude accidental opening of fire. In the case of UH-1 helicopters, it was proposed to use two consoles at once, for the pilot and for the commander.
Depending on the current situation, the operator of the XM215 multi-barreled “machine gun” could choose from one or several modules, including all four at the same time. Electric descent controls provided shots with 1800, 3600 and 7200 technical tempo shots per minute. Thus, the system could in the shortest possible time to use up ammunition, at the same time showing the highest density of fire. When firing with a minimum rate of ammunition in the form of more than 1200 ammunition enough for about 40 shooting. Turning on the maximum rate of fire, all the trunks could be devastated in just 10-12 with. One can imagine what would happen on earth after such a lead "hail."
The use of a lightweight and low-power M24 cartridge has certain advantages. Fully assembled system XM215 differed small size and weight. A frame with four modules should be hung under the nose of the helicopter, and it did not adversely affect aerodynamics or balancing. In addition, it did not reduce the capacity of the helicopter, allowing it not only to have protection, but also to fully solve the tasks.
Expected some difficulties with the maintenance of the rifle installation. To prepare for use, the barrel holder was required to be removed from the slab-plate and then all 306 empty shells were removed. Then it was proposed to install new cartridges in the barrels. Having reloaded the trunks of one module, the technicians had to do the same procedure with three others. Whether any technical tools have been developed to facilitate the work of the technical staff is unknown. If they were not there, then it is hardly worth envying the gunsmiths, who had to prepare the helicopter for a test flight.
The first prototype of the XM215 SFWSH protection system was manufactured in the autumn of 1968, and in November it was sent to the Aberdeen Proving Ground for extensive testing. Shooting was conducted, according to the results of which the experts made a number of conclusions. In practice, it turned out that in the proposed form, the complex has not only the expected advantages, but also the characteristic disadvantages. Moreover, some of the negative features of the developed system are dangerous not only for the enemy, but also for their soldiers.
First of all, it turned out that the characteristics of the M24 cartridge do not correspond to the tasks set — despite the new bullet, it was an old low-power .22 LR. In addition, the situation deteriorated the design of the trunk. Passing through the barrel of the entire length of 1 inch (4,5 caliber), the bullet simply did not have time to get acceptable energy, and its initial speed left much to be desired. A light bullet with insufficient speed quickly lost energy, and also flew along a rapidly decreasing trajectory. Finally, the bullets were affected by a downward flow of air from the rotor. They were simply blown away from the intended trajectory.
Thus, shooting from the XM215 MBG installation led to very specific results. Light bullets with insufficient speed immediately after leaving the trunks fell under the air flow from the rotor. This combination of factors led to the fact that the bullets flew in a downward trajectory and fell to the ground closer than expected by the calculations. In addition, depending on the height of the helicopter, by the time of the fall they could lose most of the already small energy. Because of this, the effective aimed fire range was limited to only a few meters, after which the behavior of the bullets became unpredictable.
Tests have also shown that the XM215 Multiple Barrel Gun system can pose a danger to its own soldiers on the ground. In certain cases, when shooting from a low altitude, uncontrollably falling bullets could hit not only the enemy, but also their fighters. This problem was also aggravated by the characteristics of piloting helicopters at low altitudes: even small movements of the helicopter could lead to new risks.
There was also an operational problem, directly connected with the combat use of weapons. Having shot off the ammunition of the four modules, which could be done in just a few volleys, the helicopter remained unprotected. After that, he needed to return to the base and undergo a slow reloading procedure.
In its current form, the XM215 helicopter protection system had only a few advantages and a whole set of shortcomings. After testing 1968-69 of the year, MRC Corporation returned to the design work and engaged in the improvement of the existing design. It was planned to correct the main shortcomings in one way or another, providing the possibility of a normal solution of the tasks. Various elements of the complex were improved, but certain of its features were not affected.
During a lengthy test program, in parallel with which the design was refined, new experienced “machine guns” of the Multiple Barrel Gun type were assembled. Over the course of several years, four prototypes were sent to the test site with some differences. As far as is known, these products almost did not differ in appearance. The main innovations involved technical and technological issues. In addition, weapons controls were being finalized.
The XM215 debugging work on the Suppressive Fire Weapon System for Helicopters program continued until the 1971 year, when it finally became clear that they did not make sense. The main problems of the original machine-gun installation were associated with an unacceptably weak cartridge, and the rejection of it did not make sense. Transferring the XM215 to a more powerful ammunition would allow to obtain the desired accuracy, accuracy and range of fire, but it should lead to a deterioration in other characteristics. Designers would have to choose between a significant reduction in ammunition and a sharp increase in size and weight. However, in both cases it was possible to get some increase in firepower.
By showing sufficient firing characteristics, the updated protection system would be large and heavy, which could lead to an unacceptable expenditure of the carrying capacity of the carrier. Retaining acceptable dimensions, in turn, would reduce the effectiveness of volley fire against enemy positions. Thus, both possible ways out of the existing situation would not lead to the desired results.
By 1971, the customer and the developer realized that the Suppressive Fire Weapon System for Helicopters had failed in a most real way. The original proposal was not suitable for practical use, and its further development was meaningless. As a result, in May 1971, the Pentagon decided to close the useless program. Four assembled XM215 MBG / SFWSH prototypes were out of work and went to storage, without having any chance of returning to the landfill.
The basis of the project Suppressive Fire Weapon System for Helicopters was the original idea of protecting the helicopter by salvo shooting at the enemy. In practice, it was found that such a concept - with all its originality - at least, was extremely difficult to implement and could not find application in the troops. It turned out that “traditional” machine guns and unguided rockets are a more convenient means of firing support for the troops, protecting helicopters and clearing the terrain before landing. The idea of a salvo system for small arms no longer returned.
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