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Kaman K-MAX

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Title: Kaman K-MAX  
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Subject: VMU-2, Intermeshing rotors, Kaman aircraft, Lycoming T53, Flettner Fl 282
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Kaman K-MAX

K-1200 K-MAX
A K-Max flying Rotex Helicopters
Role Medium lift helicopter
Manufacturer Kaman Aircraft
First flight 23 December 1991
Status Active
Produced 1991-2003
Number built 38+

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.


  • Development 1
  • Unmanned remote control version 2
  • Operators 3
  • Specifications (K-MAX) 4
  • See also 5
  • References 6
  • External links 7


Kaman K-1200 "K-MAX" operated by Timberline Helicopters

In 1947 Anton Flettner, a former German teacher and inventor, was brought to the United States as part of Operation Paperclip.[1] 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.[2] He started to design new helicopters, using the Flettner double rotor.

The K-MAX series are the latest in a long line of Kaman synchropters, the most famous of which is the HH-43 Huskie. The first turbine-powered helicopter was also a Kaman synchropter.[3]

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.[4] 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.[5] The pilot controls blade pitch with tubes running inside the mast and rotor blades to move servo flaps that pitch the blades.[6]

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.

External media
RC version of K-MAX at Ft. Eustis
Autonomous K-MAX at Yuma
Unmanned K-MAX at Yuma
K-MAX with wrecking ball

A K-MAX has been used for demolition work by having a wrecking ball as a slung load.[7]

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.[8] The production line was shut down in 2003, but may restart if the U.S. Marine Corps orders more autonomous K-MAXs.[9]

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.[10][11] Ten firm orders may convince Kaman to produce K-MAX again.[12]

The K-MAX line has flown 300,000 hours as of 2014, and costs $1,200 per flight hour to operate.[12]

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,[13] and again in 2010.[14]

In December 2010 the Naval Air Systems Command awarded a $46 million contract to Kaman for two aircraft,[15] and in 2011 they completed a five-day Quick Reaction Assessment.[16]

In December 2011 an unmanned K-MAX was reported to be at work in Afghanistan.[17] 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.[18] As of February 2013, the K-MAX had delivered 2 million pounds of cargo in 600 unmanned missions over more than 700 flight hours.[19]

Unmanned K-MAX

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.[20]

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.[21] 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.[22]

The unmanned K-MAX has won awards from Popular Science and Aviation Week & Space Technology,[23] and was nominated for the 2012 Collier Trophy.[24]

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.[25] 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.[26] The investigation determined that the crash was not caused by mechanical problems,[27] 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.[28]

At the 2013 Paris Air Show, Kaman promoted the unmanned K-MAX to foreign buyers. Several countries have reportedly expressed interest in the system.[29]

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.[30] Other features are being examined, including the ability to be automatically re-routed in flight, and to fly in formation with other aircraft.[31]

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.[27]

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.[32]

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.[33]

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 from a proof-of-concept project into a program of record. Formal requirements for unmanned aerial cargo delivery are being written to address expected future threats, including electronic attack, cyber warfare, and effective hostile fire; these were avoided in Afghanistan quickly and cheaply by flying at night at high altitudes against an enemy with no signal degradation capabilities.[34][35] 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 Oswego, North Carolina. 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.[36]


A HELOG Heliswiss Kaman K-Max
  • Aeromaster, 1 aircraft[38]
 New Zealand
  • Skywork Helicopters Ltd.[40]
  • Rotex Helicopter AG[41]
 United States

Specifications (K-MAX)

Data from K-MAX Performance and Specs[47]

General characteristics
  • 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[48][49])


See also

Related development
Aircraft of comparable role, configuration and era


  1. ^  
  2. ^ "Anton Flettner"; Hubschraubermuseum Bückeburg
  3. ^ "Twin Turborotor Helicopter." Popular Mechanics, August 1954, p. 139.
  4. ^ 'K-Max Intermeshing Rotor Drive System' 53rd Annual Forum Proc., AHH, 1997.
  5. ^ 'Composites take off ... in some civil helicopters.' March 1, 2005. Retrieved: 26 June 2011.
  6. ^ Chandler, Jay. "Advanced rotor designs break conventional helicopter speed restrictions (page 2)" . ProPilotMag, September 2012. Accessed: 10 May 2014. Archive 2
  7. ^ Karman III, John R. (18 August 2008). "Demolition precedes new construction for Ursuline schools". 
  8. ^ The Kaman K-MAX Current Status by Markus Herzig
  9. ^ Padfield, R Randall (March 2012). "Civil Tiltrotor and K-Max Aerial Truck Back in the Saddle?". Retrieved 31 March 2012. 
  10. ^ Kaman Aerospace Soliciting Interest in New K-MAX® Production Businesswire
  11. ^ Heli-Expo 2014: Kaman looks to restart K-MAX production Shephardmedia
  12. ^ a b c Head, Elan. "Production potential" page 44 Vertical Magazine, April/May 2014. Accessed: 8 July 2014.
  13. ^ "Lockheed Martin And Kaman Aerospace Demonstrate Unmanned Supply Helicopter To U.S. Army". Retrieved 13 August 2009. 
  14. ^ "Team K-MAX demonstrates successful unmanned Helicopter Cargo resupply to U.S. Marine Corps", Lockheed Martin press release, 8 February 2010. Retrieved 14 March 2010.
  15. ^ "Lockheed Martin awarded $45.8 million for unmanned KMAX" Defense Update, 6 December 2010. Accessed: 11 December 2010.
  16. ^ "Lockheed Martin/Kaman K-MAX Completes US Navy Unmanned Cargo Assessment", 8 September 2011. Accessed: 9 September 2011.
  17. ^ John Roach. "Robotic helicopters at work in Afghanistan". Future of Technology,  
  18. ^ "Unmanned helicopter makes first delivery for Marines in Afghanistan".  
  19. ^ McLeary, Paul. "K-MAX Chugging Along in Afghanistan" Aviation Week, 3 February 2012. Accessed: 4 February 2012.
  20. ^ "Beacon improves UAV’s cargo-delivery accuracy" Marine Corps Times, 8 July 2012. Retrieved: 9 July 2012.
  21. ^ U.S. Marine Corps to Keep K-Max Unmanned Cargo Re-Supply Helicopter in Theater for Second Deployment Extension - Lockheed press release, July 31, 2012
  22. ^ US Marines extend K-MAX unmanned helicopter's use in Afghanistan -, March 18, 2013
  23. ^ "Unmanned K-MAX Wins Top Innovation Honors, USMC Praise". HeliHub. 9 Jan, 13. Retrieved 26 February 2013. 
  24. ^ "Unmanned K-Max is nominee for Collier Trophy". HeliHub. 11 Feb, 13. Retrieved 26 February 2013. 
  25. ^ Unmanned Marine helo crashes in Afghanistan -, 13 June 2013
  26. ^ US Navy set to resume K-Max flights -, 14 August 2013
  27. ^ a b Marines Work to Extend K-MAX in Afghanistan Through 2014 -, 25 September 2013
  28. ^ Tailwinds caused K-Max crash in Afghanistan -, 11 August 2014
  29. ^ K-Max looks to lift overseas sales -, 18 June 2013
  30. ^ STEPHEN TRIMBLE. "Lockheed tests K-Max cargo enhancement" -, 18 November 2013. Accessed: 18 November 2013.
  31. ^ Lockheed seeks more autonomy for unmanned K-Max -, 11 September 2013
  32. ^ USMC Unmanned Lift Competition Taking Shape -, 25 September 2013
  33. ^ Marines Fly Helicopters With Mini-Tablet -, 5 April 2014
  34. ^ K-MAX RoboCopter Comes Home To Uncertain Future -, 24 July 2014
  35. ^ K-Max returns from Afghan deployment -, 25 July 2014
  36. ^ K-MAX cargo drone home from Afghanistan, headed to storage -, 2 August 2014
  37. ^ "colombian army aviation". Retrieved 5 January 2013. 
  38. ^ a b EC725 "Peruvian police anti-drug order boosts K-MAX pg. 21". 29 January 2001. Retrieved 27 October 2014. 
  39. ^ "HELOG". Retrieved 5 January 2013. 
  40. ^ "Skywork Helicopters". Retrieved 6 January 2014. 
  41. ^ Markus Herzig. "Swiss Helicopters - Current Fleetlist". Retrieved 2012-06-18. 
  42. ^ "Central Copters Inc.". Retrieved 7 July 2013. 
  43. ^ "Heliqwest Fleet". Retrieved 10 August 2013. 
  44. ^ "Swanson group aviation". DNA Web Agency. Retrieved 5 January 2013. 
  45. ^ "Timberline Helicopters". Retrieved 5 January 2013. 
  46. ^ "US Marine Corp K-Max". Retrieved 5 January 2013. 
  47. ^ "K-MAX Performance and Specs".  
  48. ^ Kaman K-1200 "K-MAX"
  49. ^ "Kaman K–1200 FAA Approved Rotorcraft Flight Manual" Page 1–4. Kaman, February 17, 2004. Retrieved: October 2, 2012.

External links

  • Kaman Aerospace's K-MAX page
  • Superior Helicopter K-MAX with Firemax system
  • Austrian Wucher Helikopter
  • Video of a K-MAX starting up

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