The first thought when meeting Kaman K-MAX is impossible!
The helicopter violates the space-time continuum and the laws of Euclidean geometry, otherwise how to explain the pattern of motion of its blades? In contrast to the coaxial scheme, in which the planes of rotation of the propellers are parallel to each other, or the transverse scheme, in which the propeller hubs are spaced a significant distance exceeding the length of the blades, something unimaginable happens here - the K-MAX rotors intersect in space! Another moment, and they will smash the propeller hubs and chop each other to smithereens! But no … the blades miraculously pass through the matter and diverge to the sides. The helicopter continues its flight safely.
The above scheme with crossed rotors is called "synchropter". The ingenious invention belongs to the German engineer Anton Flettner, who experimented with such machines at the turn of the 30s-40s (Fl.265 and Fl.282 "Kolibri").
Synchropter is a transverse twin-rotor helicopter with criss-crossing rotors. The screws rotate in opposite directions, while their axes of rotation are located at a slight angle to each other. The rotation of the propellers is synchronized by means of a rigid mechanical connection to ensure the prevention of blade collision.
Like helicopters with a coaxial rotor design (for example, helicopters from the Kamov Design Bureau), synchropters do not have a bulky tail boom and power losses for the tail rotor drive. Other advantages over “classic” single-rotor helicopters include lower noise and vibration levels. Less moment of inertia - and therefore better maneuverability.
At the same time, the scheme with crossed rotors allows you to abandon the complex column of rotors: a simple and lightweight transmission helps to reduce the cost of the synchropter and makes it easier to maintain in comparison with helicopters with coaxial propellers.
The key disadvantage of synchropters is the lower efficiency of the rotor in horizontal flight due to their mutual influence on each other. In addition, the propeller planes are slightly turned in different directions - the thrust decreases (the thrust vector per cosine of the angle). As a result, synchropters are somewhat inferior in speed to helicopters built according to other schemes. Another unpleasant feature is the occurrence of a longitudinal moment and problems with the balancing of the rotorcraft. Servo-flaps on the rotor blades are used to control the helicopter.
The specific layout is a kind of "calling card" of Kaman Aircraft. This small helicopter company traditionally occupies narrow niches in the civilian market for special-purpose helicopters and creates specialized vehicles for military customers. The volume of serial production is limited to a couple of tens (at best, hundreds) of copies. Among the most famous works - Kaman (light anti-submarine / multipurpose helicopter SH-2 "SeaSprite", which was equipped with all cruisers and frigates of the US Navy in the 60-70s.).
In addition to the SeaSprite, which was built according to the usual single-rotor design with a tail rotor, Kaman Aircraft was very successful in creating helicopters with criss-cross rotor. Founder Charles Kaman built his first K-125 synchropter in 1945, but the first commercially successful model appeared two years later. Search and rescue and fire synchropter Kaman HH-43 Huski was serially built by order of the US Air Force and exported to other countries of the world.
Half a century after the success of the Husky, Kaman Aircraft decided to revert to the creation of helicopters with criss-cross rotor. In 1991, the prototype of the K-MAX flying crane, designed to transport goods on an external sling, took off in the air.
According to Kaman Aircraft specialists, synchropters are most effective in operations related to vertical lifting of a load, because two rotors create a large lift, and the layout provides a concentration of lift in the center of gravity of the helicopter. The design allows you to create a "wedge-shaped" silhouette, which improves the view of the lower hemisphere from the cab - when you need to check the condition of the load on the external sling, as well as select with high precision the place for unloading or picking it up.
An important condition is the absence of a tail rotor: in conditions where flying cranes usually work (construction sites, logging sites), there is a high probability of an accidental "meeting" with power lines, tree branches and nearby buildings. In this regard, the synchroopter is much safer than conventional helicopters.
As for the speed (the maximum permissible speed of the K-MAX is only 185 km / h), it does not play a big role in the characteristics of flying cranes, usually shuttling over a short distance.
The K-MAX helicopter was created with an eye to the interests of logging and woodworking companies: a small, extremely reliable flying crane for skidding logs. Prepared for cold climates and limited field maintenance. Improved visibility, reinforced tricycle chassis, rejection of complex and capricious equipment.
Working at logging sites, on hard-to-reach slopes and on construction sites poses a significant threat to the life and health of the pilot. Safety measures come to the fore: the K-MAX helicopter is equipped as standard with a Simula shock-absorbing seat with a five-point seat belt, capable of saving the pilot's life during impacts with an overload of up to 20g.
It is noteworthy that out of 38 built copies of the Kaman K-MAX, twelve vehicles have been lost as a result of various accidents and emergency situations. Nevertheless, the remaining helicopters continue to be actively operated by logging and construction companies in the USA, Germany, Switzerland, Colombia and New Zealand.
… He was a great guy and worked conscientiously. But a quiet, peaceful life did not work out - the Pentagon became interested in a hard-working helicopter.
- Get a summons, sign.
How K-MAX pulled a soldier's strap
In modern local wars, the main part of aviation sorties falls on the transportation of various cargoes in the conflict zone. Helicopter pilots are experiencing particular stress, on whose shoulders lies the supply of thousands of armies, dispersed at separate checkpoints over a vast territory, often in difficult terrain, surrounded by a hostile population.
This is undoubtedly Afghanistan. For the first time, the Air Force of the 40th Army faced similar difficulties: helicopter pilots had to show miracles of endurance in winter, supplying a 100,000-strong military contingent with everything they needed - from food, ammunition and kerosene, to tents, warm clothes, books and other specific cargo.
The Yankees, who have been waging a fruitless fight against al-Qaeda terrorists in the mountain gorges of Afgan for many years, also know about this. The supply of soldiers is constantly growing. Freight traffic is increasing.
On this and decided to play the company Kaman, which offered the military an unexpected solution to the problem - an unmanned vehicle capable of automatically delivering goods in the conflict zone.
In this situation, such a transport looks like a justified decision: there is no need for a person to risk his life in such banal and simple missions, flying over hostile territory every day. To fly from point A (Bagram airfield) to point B (a remote checkpoint near Jalalabad) and carefully unload cargo on a rocky plateau - such a mission does not require advanced supercomputers, special piloting skills or any complex technical solutions. The entire flight takes place according to the data of the GPS system, signals from radio beacons, and, if necessary, under the remote control of the operator.
The first prototype of the transport unmanned helicopter K-MAX Unmanned Multi-Mission Helicopter, created in collaboration with the Lokheed Martin Corporation, was presented to the military in 2008. An updated version appeared in 2010.
In the same year, Kaman received a $ 46 million grant to build two transport drones to demonstrate the system's capabilities in practice. The project was overseen by the Naval Aviation Systems Command (NAVAIR). By the end of 2011, both ordered helicopters, having received the corresponding livery of the Marine Corps aviation, arrived in the Afghan mountains and began test flights.
The first transport mission in conditions close to combat took place on December 17, 2011. The drone delivered 1.5 tons of food on an external sling to the remote Combat Outpost Payne base.
The Marines liked the idea - drones were regularly sent on missions. As of February 2013, both K-MAXs have flown 600 sorties over the Afghan mountains, spending over 700 hours in the air and carrying around 900 tons of various cargo during that time. During this time, Kaman received a prize from Popular Science magazine, and the unmanned version of the K-MAX helicopter learned to fly in the dark and deliver goods with an accuracy of 3 meters.
On March 18, 2013, the command of the ILC extended the project for an indefinite period with the wording "until special orders are received." There is no money for the purchase of new drones, but no one wants to give up transport UAVs.
However, on June 5, 2013, a nuisance occurred. During one of the transport missions on approaching the "point", the drone fell to the ground, seriously damaging the fuselage. The investigation showed that this was not an operator's mistake - the UAV at that moment was in autonomous mode, following the programmed route. The commission found no traces of enemy fire or malfunctions in the "mechanical" part and engine of the helicopter. There is no reason to seriously consider the version with the appearance of electronic warfare stations similar to the Russian Avtobaza among the Afghan Basmachs. It seems that the fault was in the program, or an incorrect signal from one of the UAV's sensors.
In September, the crashed K-MAX was sent to the United States for repairs, the second drone continued to carry out tasks related to the transportation of goods over Afghanistan.
The episode with the UAV crash did not diminish interest in the unmanned version of the flying crane: Kaman successfully presented her idea at the Paris Air Show, receiving warm reviews from future foreign customers.
The new version of the UAV received the ability to automatically capture cargo (a special module on the container body is required, which supplies the UAV's radio signal) and the skill of group flight in the same formation with other unmanned and manned vehicles. Rated payload - 5,000 pounds of cargo (2,270 kg) per trip.
There is reason to believe that the need for such machines may arise not only over the battlefield, but also in the zones of man-made disasters - suffice it to recall the risk faced by the liquidators of the Chernobyl accident, who were forced to drop sandbags from helicopters into the crater of the destroyed fourth power unit.
In view of the undoubted usefulness of such a system, Kaman and Lokheed Martin expect to receive a contract from the ILC aviation in the near future for the supply of at least 16 serial UAVs of this type.
A holy place is never empty. Smelling the smell of arrival, a Boeing pulled up to the scene with its version of a transport UAV based on the Little Bird light army helicopter.
Comparative tests of the Kaman K-MAX and Boeing H-6U Little Bird drones began in February 2014 at the Quantico military base in Virginia.
