|A K-Max flying Rotex Helicopters|
|Role||Medium lift helicopter|
|First flight||23 December 1991|
The Kaman K-MAX (Company designation K-1200) is an American helicopter with intermeshing rotors (synchropter) built by Kaman Aircraft. It is optimized for external load operations, and is able to lift a payload of over 6,000 pounds (2,722 kg), which is more than the helicopter's empty weight. A remote controlled unmanned aerial vehicle version is being developed and is being evaluated in extended practical service in the war in Afghanistan.
In 1947 Anton Flettner, a former German teacher and inventor, was brought to the United States as part of Operation Paperclip. He was the developer of the former German helicopter Flettner Fl 282 "Kolibri" (Hummingbird), which had the principle of counter-rotating side-by-side intermeshing (combing) rotors, as the means to solve the problem of torque compensation, normally countered in single rotor helicopters by a tail rotor or vented blower exhaust. Anton Flettner stayed in the United States and became the chief designer of the Kaman company. He started to design new helicopters, using the Flettner double rotor.
The K-1200 K-MAX "aerial truck" is the world's first helicopter specifically designed, tested, and certified for repetitive external lift operations and vertical reference flight (Kaman received IFR Certification in 1999), an important feature for external load work. Other rotorcraft used for these tasks are adapted from general-purpose helicopters, or those intended to primarily carry passengers or internal cargo. The aircraft's narrow, wedge-shaped profile and bulging side windows gives the pilot a good view of the load looking out either side of the aircraft.
The transmission has a reduction ratio of 24 in three stages, and is designed for infinite life. The rotor blades are built with a wooden spar and fiberglass trailing edge sections. Wood was chosen for its damage tolerance, fatigue resistance and to take advantage of field experience and qualification data amassed from a similar spar on the HH-43 helicopter, built for the U.S. Air Force in the 1950s and 1960s. The pilot controls blade pitch with tubes running inside the mast and rotor blades to move servo flaps that pitch the blades.
The K-MAX relies on the two primary advantages of synchropters over conventional helicopters. The first of these is the increased efficiency compared to conventional rotor-lift technology; the other is the synchropter's natural tendency to hover. This increases stability, especially for precision work in placing suspended loads. At the same time, the synchropter is more responsive to pilot control inputs, making it possible to easily swing a load, to scatter seed, chemicals, or water over a larger area.
|RC version of K-MAX at Ft. Eustis|
|Autonomous K-MAX at Yuma[dead link]|
|Unmanned K-MAX at Yuma|
|K-MAX with wrecking ball|
Thirty-eight K-1200 K-MAX helicopters have been built. As of February 2012, 13 of these were not airworthy or have been written off in accidents. The production line was shut down in 2003, but may restart if the U.S. Marine Corps orders more autonomous K-MAXs.
Beginning February 2014, Kaman is considering restarting the K-MAX production, having recently received over 20 inquiries for firefighting, logging or industry transport requirements additionally to requests for the military unmanned version. Ten firm orders may convince Kaman to produce K-MAX again.
The K-MAX line has flown 300,000 hours as of 2014, and costs $1,200 per flight hour to operate.
Unmanned remote control version
An unmanned remote control and mostly autonomously flying, optionally piloted vehicle (OPV) version, the K-MAX Unmanned Multi-Mission Helicopter, was developed for hazardous missions. It can be used in combat to deliver supplies to the battlefield, as well as civilian situations involving chemical, biological, or radiological hazards. A prototype of this was shown in 2008 for potential military heavy-lift resupply use, and again in 2010.
In December 2011 an unmanned K-MAX was reported to be at work in Afghanistan. On December 17, 2011, the United States Marine Corps conducted the first unmanned aerial system cargo delivery in a combat zone using an unmanned version of the Kaman K-MAX. The unmanned K-MAX moved about 3,500 pounds of food and supplies to troops at Combat Outpost Payne. As of February 2013, the K-MAX had delivered 2 million pounds of cargo in 600 unmanned missions over more than 700 flight hours.
A third unmanned K-MAX, based in the US, was tested in 2012 to deliver cargo to a small homing beacon with three-meter precision.
On July 31, 2012, Lockheed announced a second service extension for the K-MAX in Afghanistan for the Marines. This extended operations to the end of March 2013, with the option to extend through to the end of September 2013. On March 18, 2013, the Marine Corps extended its use of the unmanned K-MAX helicopters indefinitely. The Corps does not currently have plans to buy more, but the two aircraft in use would remain "until otherwise directed". At the time of the announcement, they had flown over 1,000 missions and hauled over 3 million pounds of supplies. Assessments for their use after deployment are being studied. While proving useful, their "niche" in future Marine Corps aviation is not yet clear.
On June 5, 2013, one of the unmanned K-MAX helicopters crashed in Afghanistan while resupplying Marines. No injuries occurred and the crash was investigated. Pilot error was ruled out, as the aircraft was flying autonomously to a predetermined point. The crash happened during the final stages of cargo delivery. Operational flights of the remaining unmanned K-MAX were suspended following the crash. On August 14, 2013, the Navy said the K-MAX could resume flying by the following week, with the final decision resting with operational commanders. The week before, the K-MAX flew 16 hours. Swing load was seen as the prime cause of the crash. The Marine Corps is considering turning the K-MAX into a program of record, with possible uses including ship-to-shore deliveries. The investigation determined that the crash was not caused by mechanical problems, but by unexpected tailwinds. As the helicopter was making a routine food delivery, it experienced tailwinds instead of headwinds, causing it to start shaking. Operators employed a weathervane effect to try and regain control, but its 2,000 lb load began to swing, which exacerbated the effect and caused it to crash. The crash report determined that it could have been prevented if pilots intervened earlier and mission planned received updated weather reports; diverging conditions and insufficient programming meant it could not recover on its own and required human intervention.
The K-MAX supporting Marines in Afghanistan was planned to remain in use there until at least August 2014. The Marine Corps is looking into acquiring the unmanned K-MAX as a program of record, and the U.S. Army is also looking into it to determine cost-effectiveness. If it is accepted into service, the adapted commercial rotorcraft would re-enter production and Kaman would reopen the facility to build it. Lockheed and Kaman estimate re-establishing the line would take nine months, with the first aircraft delivered three months later. In theater, the unmanned K-MAX performed most missions at night and successfully lifted loads of up to 4,500 lb (2,000 kg). Hook-ups of equipment were performed in concert with individuals on the ground, but Lockheed is looking into performing this action automatically. It is building a device that sits on top of the package that the helicopter can hook up to by itself, and this feature was demonstrated in 2013. Other features are being examined, including the ability to be automatically re-routed in flight, and to fly in formation with other aircraft.
The House Armed Services Committee has shown its support for the unmanned K-MAX. It has urged the Army to look into the cargo UAV concept, as 30,000 lb (13,600 kg) of cargo were successfully delivered in one day over the course of six missions (average 5,000 lb (2,270 kg) transported cargo per mission). Lockheed and Kaman have discussed the purchasing of 16 helicopters with the Navy and Marine Corps for a baseline start to the program.
The unmanned K-MAX is competing with the Boeing H-6U Little Bird for the Marine Corps unmanned lift/ISR capability. Evaluations of the two helicopters were to begin in February 2014 at Marine Corps Base Quantico.
Marines at Quantico successfully landed an unmanned K-MAX, as well as a Little Bird, autonomously using an Ipad-like mini-tablet. The helicopters were equipped with technology called the Autonomous Aerial Cargo/Utility System (AACUS), which combines advanced algorithms with LIDAR and electro-optical/infrared sensors to enable a person holding a tablet to select a point to land the helicopter at an unprepared landing site. Autonomous landing without the need for remote control or tele-operation reduces operator burden and allows them be resupplied or conduct other missions like medical evacuation around the clock. The AACUS weighs 100 lb (45 kg), so it can be easily integrated onto other aircraft like the CH-53E Super Stallion and V-22 Osprey. Operational use of the system could be possible within two years.
Both unmanned K-MAX helicopters in use by the Marine Corps returned to the United States in May 2014, with the Corps assessing that they were no longer needed to support missions in the country. After deploying in December 2011, originally planned for six months, it stayed for almost three years and lifted 2,250 tons of cargo. The aircraft was sent to Lockheed's Owego facility in New York, while the service contemplated the possibility of turning the unmanned K-MAX into a program of record. Formal requirements for unmanned aerial cargo delivery are being written to address expected future threats. In Afghanistan, there were few anti-aircraft or electronic warfare threats, so the aircraft flew mostly at night and at high altitudes to avoid relevant threat conditions; as an affordable proof-of-concept project, self-defense systems and robust communications links to prevent hacking or jamming of the signal from a helicopter to the operators were not added. Future requirements will address a range of potential threats including electronic attack, cyber warfare, and effective hostile fire. Although unmanned supply systems will put fewer personnel in combat environments, the unmanned vehicles themselves need to survive to perform their mission, either by being more rugged and expensive, or through larger numbers of cheap and expendable hardware. Officials are assessing the K-MAX model that crashed and plan to repair it in 2015. Until then, the helicopters, ground control stations, and additional equipment will be stored at Lockheed's facility in Owego, New York. Renewed flight demonstrations are being urged for 2015 to show their continued utility for Marine Corps missions, including small-unit responses and amphibious operations in the Pacific theater.
- Skywork Helicopters Ltd.
- Rotex Helicopter AG
- Central Copters, Inc.
- HeliQwest International
- Swanson Group Aviation
- Timberline Helicopters, Inc.
- United States Marine Corps
Data from K-MAX Performance and Specs
- Crew: 1
- Capacity: 6,000 lb (2,722 kg) external load
- Length: 51 ft 10 in (15.8 m)
- Rotor diameter: 48 ft 3 in (14.7m)
- Height: 13 ft 7 in (4.14 m)
- Empty weight: 5,145 lb (2,334 kg)
- Useful load: 6,855 lb (3,109 kg)
- Max. takeoff weight: 12,000 lb (5,443 kg)
- Powerplant: 1 × Honeywell T53-17 turboshaft, 1341 kW (1,800 shp), flat rated to 1118 kW (1500 shp) for take-off / 1350 shp in flight)
- Maximum speed: 100 knots (185.2 km/h)
- Cruise speed: 80 knots (148.2 km/h)
- Range: 267 nm (494.5 km)
- Fuel consumption: 85 gallons/hour
- Related development
- Aircraft of comparable role, configuration and era
- Boyne, Walter J. (2011). How the Helicopter Changed Modern Warfare. Pelican Publishing. p. 45. ISBN 1-58980-700-6.
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- Kaman K-1200 "K-MAX"
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|Wikimedia Commons has media related to Kaman K-MAX.|
- Kaman Aerospace's K-MAX page
- Superior Helicopter K-MAX with Firemax system
- Austrian Wucher Helikopter
- Video of a K-MAX starting up