Back to Home

Back to Helicopter Walkarounds

Kaman K-1200 "K-MAX"
in Shizuoka Heliport, 13 Nov. 2004

In a day of the Shizuoka Heliport Festival, a K-MAX came here for refuel.

K-MAX is developed by Kaman Aerospace as a specialty of cargo sling. This aircraft is owned by AKAGI HELICOPTER Co.Ltd., usually works in Nara prefecture, Japan for transportation of lumbers.

"K-1200" is Kaman's developement number. A name "K-MAX" is so popular and "K-1200" is not so common, but type certification is achieved as "K-1200".

K-MAX is always working hard in the mountains, peoples cannot see it. Cause I was looking forward to see it, when K-MAX arrives at Shizuoka Heliport, I was so glad.

I loves this specialty machine ! ! !

Development engineers thinks about only cargo sling. Speed is thrown away. How do I make it able to lift heavy loads? How do I make it low cost? How do I make it good maintenance machine? How do I make it good tool for the pilot?

Engineer's thought is clear. This is a reason of that I love specialty machines.

Funny configuration. There are reasons.

Crew : 1
Passengers : 2 are possible on two auxiliary seats fastened to the fuselage side
Length : 15.85m (with rotor)
Rotor Diameter : 14.73m
Width over main wheels : 3.56m
Empty weight : 2268kg / 5000lb
Max hook load : 2721kg / 6000lb
Fuel : 863 litres
Max. weight without external load : 2721 kg / 6000lb
Max. gross weight with external load : 5216 kg / 12000lb
Powerplant : AlliedSignal (Lycoming) T5317A-1 turboshaft
Power : 1341 kW (1800 shp) / flat rated to 1118 kW (1500 shp) for take-off

VNE, Power On No External Load:
   100 KIAS, S.L. to 5000 feet density altitude
    90 KIAS, S.L. to 8000 feet density altitude (IFR)
    70 KIAS, S.L. to 5000 feet density altitude (with HEC)
VNE, Power On With External Load:
    80 KIAS, S.L. to 5000 feet density altitude
VNE, Power Off
    80 KIAS, S.L. to 5000 feet density altitude
   15,000 feet (day/night VFR)
   12,000 feet (IFR)
   Maximum 100% Nr (260 r.p.m.)
   Minimum   75% Nr (195 r.p.m.)
   Maximum 105% Nr (273 r.p.m.)
   Minimum  100% Nr (260 r.p.m.) ≤ 6500 lbs.
   Minimum  104% Nr (270 r.p.m.) > 6500 lbs.
   Minimum  104% Nr (270 r.p.m.) for operations above 10,000 feet density altitude
   Maximum 100% Nr (260 r.p.m.) for ground extended operations

Two NRs are unusual. 100%(260rpm) is for light weight, and 104%(270rpm) is for slinging load and/or above 10,000ft density altitude.

270rpm NR, thus tip speed 207.8m/s is so slow in modern helicopters. Speed is thrown away, large blades round slowly, required power for hovering is reduced and great sling capacity. 

Fuji/Bell 205B (UH-1J in Japan Ground Self Defense Force) using same engine, its maximum gross weight is 11,200lb and max hook load is 4500lb / 2041kg. K-MAX can sling heavier than 205B, and is "Normal category" helicopter. It's essential.


A pair of two bladed rotors, side by side, counter-rotating and intermeshing type. Angle between rotors is 25 degree. There is no tail rotor.

World's first mass production helicopter, Flettner FL282 Kolibri was same type. Therefore this is traditional configuration, but now only Kaman can produce this type.

Two rotors are connected by gears in transmission. Therefore rotors never hit each other.


Intermeshing rotor dosen't need tail rotor and can use all power for generating the lift. It's an advantage for cargo sling helicopter.

The power increases on cargo pick up and decreases on release. In case of single rotor helicopter, the pilot must adjust pedal to match with main rotor torque. But in intermeshing helicopter, the pilot dosen't have to adjust pedal. It's also an advantage.


Large bubble canopy on both left and right side of cockpit. Circular cylinder shape canopy for a variety of the pilot's height and narrow fuselage, the pilot can see his sling load directly in his eyes.

This is great advantage for speedy cargo work.

Installation of the external instrument panel on the fuselage exterior is below the door. This panel included load weight, engine torque, NR or EGT. “Repeater” lights for the fire warning and master caution lights were also included on the external panel.

An adjustable torso support is mounted to the seat to allow the pilot to comfortably rest his upper body while looking outside the aircraft for long periods.

The crashworthy seat has a 20g vertical, 16g horizontal, and 8g lateral energy absorbing capability and incorporates a 5-point restraint harness.

Conventional helicopter controls are outfitted with all the functions necessary to perform external load operations and handle any critical emergency procedures. The cyclic also has a vertical energy absorbing feature in its design to allow the stick to compress under impact loads.

The “flying pilot office” was further simplified by incorporating smart gauges. The gauges monitored and recorded engine, transmission, and hook performance values throughout the flight. These values included peak values, any exceedances, and in the case of the load meter each load lifted could be automatically recorded and then downloaded with a computer. Historical values are retained by these instruments to document aircraft operations. These historical values can be used to optimize the weights being carried, track pilot utilization, and monitor aircraft exceedance trends.


The tail section includes horizontal stabilizers with vertical endplates and a vertical fin with a rudder.

The stabilizer is connected via control tubes and cranks and moves proportionally to collective inputs. The rudder is connected via control tubes and teleflex cable, and also moves proportionally, to the rudder pedals. These further reduce pilot control inputs required in forward flight.

In intermeshing rotor helicopter, pedal input is reversed in autorotation. Thus Kaman's helicopter equips "reverse mechanism" to reverse yaw response by pedal input when collective pitch lever is down to autorotation position.


The high, tricycle landing gear allows for ground obstacle clearance. It consists of three wheel and tire assemblies, individual highenergy absorbing shock struts, and includes skid plates (“bear paws”) around the wheels for soft terrain and snow.

The main wheels are equipped with disc-type hydraulic brakes that can be individually applied at the top of the rudder pedals or locked for parking.

The nose wheel is self-centering with the nose gear fully extended, swivels 360 degrees, and can be locked in the forward position. Any or all of the skid plates may be removed with no change in flight limitations.

Pitot tube is in front of nose gear.


The hook and support structure. Webs and stringers are exposed to outside. Maybe inside of this section is fuel tank to alleviate any aircraft pitching changes associated with fuel consumption. Large flat panel above hook is a door of baggage compartment.

The fuselage is semi-monocoque 2024-T3 and T42 alclad sheet aluminum alloy structure with extensive steel hardpoints for component attachments and addon equipment. The fuselage skin is .050 - .060 inch (.127-.152 cm) material with higher thicknesses in the cockpit area.


The hook was positioned near the rotor center of gravity (CG) to alleviate any aircraft pitching changes associated with picking up or releasing an external load.


A cargo hook junction box, located just forward of the hook contains four connectors. There are connectors for the aircraft hook, the load link (for measuring loads on the hook), a long line with a remote hook, and a spare for optional equipment.

A loudspeaker locates just aft of the hook for cargo worker.


The rotor system includes servo-flaps on the trailing edge of the blades (at the 3/4 radius position) and in-flight blade tracking capability. This is also Kaman's technology of proud.


Each rotor blade is mounted on the hub with a lead-lag pin. The hub assembly has a 30deg offset built in where the blade attaches to the hub. Two damper assemblies connect the rotor blades on each hub to each other. The rotor is a teetering rotor system, with lead and lag. Each rotor blade is mounted rigidly in the hub through the blade sleeve assembly. Torsional movement is obtaining by the servo flap assembly twisting the blade.

The rotor blade is 289 inches long, with a chord of 17.2”, and weighs 191 pounds. It has a 23012 airfoil. Its structure is composite, with an inspection requirement at 10,000 hours. Through response to the servo flap, the rotor blade is able to generate 13deg of pitch. There is 2deg of twist built into each blade. Angle of incidence of the blade is 5deg, which is obtained by installation in the hub assembly. Therefore, effective twist is 7deg.

(from HTK-1 flight manual) 

The conventional cockpit flight controls connect to a mechanical mixing module underneath the cockpit floor. The mixing module transmits control inputs via control tubes to the azimuth assembly. An azimuth assembly joins the non-rotating flight control system to the rotating rotor controls and mounts to the bottom of the transmission. The azimuth contains two gimbal-mounted cyclic control rings, one for each rotor, that pivot in any angular plane directed by the flight controls. Two rods from each azimuth transmit control inputs through the hollow rotor shafts to cranks on each rotor hub. These cranks transmit the inputs to the servo-flaps on the rotors. It’s this direct mechanical control of the servo-flap on the rotor that eliminates the requirement for a hydraulic system.


The Honeywell Allied Signal (Lycoming) T5317A1 turboshaft engine has an 1800 SHP thermal rating and is flat rated to 1500 SHP with a maximum continuous rating of 1350 SHP. The K-MAX helicopter utilizes 1350 SHP as a maximum limit and requires only approximately 1200 SHP to lift a combined weight (aircraft and external load) of 12,000 Lb. (5443 Kg) under ICAO standard day conditions at sea level.

The 1500 SHP transmission is operated at a maximum of 1350 SHP (58 PSI torque) and is attached to the engine via a no-maintenance, fail-safe Kaflex drive shaft. The transmission has one input and two output gear assemblies driving hollow rotor shafts and incorporates a freewheeling unit and rotor brake.





 40 psi(920shp)  58 psi(1350shp) (0 - 25 Knots)
 45 psi(1040shp) (> 25 Knots)

Max Continuous

 40 psi(920shp)  45 psi(1040shp) (0 - 80 Knots)

It should be noted that 40 PSI (920 SHP) of torque was used, although the powerplant is capable of developing 58 PSI. This limitation of 40 PSI was placed on the aircraft based on handling qualities.


K-MAXのファンサイト、"The Kaman K-MAX ALL ABOUT THIS EXCITING AERIAL TRUCK"によると、1991年から始まったK-MAXの生産機数は38機(2004年現在)。年産たったの3機! でもOH-1よりいいか・・・








頑張れ K-MAX!




Taxi out and take off.




K-MAX References:

Akagi Helicopter Co.Ltd.
Helicopter History Site, Kaman Timeline

  1) George Haliscak (Chief Test Pilot, Kaman Aerospace Corporation), "Vertical Reference Flight (VRF) the Kaman K-1200 "K-MAX" Helicopter Design", American Helicopter Society 55th Annual Forum, Montreal, Quebec, Canada, 25-27 May, 1999.
  2) Frank Gallagher, Fu Shang (John) Wei and Alfred Gates, "Kaman K-MAX K-1200 High Altitude Performance", American Helicopter Society 58th Annual Forum, Montreal, Canada, 11-13 June 2002.
  3) T.O. 1H-43(H)B-1(CHANGE 5-16 May 1968), Flight Manual, USAF Series HH-43B Helicopter, 22 September 1966 .
  4) AN 01-260HBA-1/NAVWEPS 01-260HBA-1, Flight Manual, Navy Models HOK-1 HUK-1 Helicopters, 1 January 1960.
  5) AN 01-260HAA-1, Pilot's Handbook, Navy Model HTK-1 Helicopters, 1 September 1952.
  6) Type Certificate Data Sheet, NO.TR7BO Revision 2, Kaman Model K-1200, Federal Aviation Administration, Department of Transportation, February 28, 2001.
  7) Shawn Coyle, "Cyclic & Collective - More Art and Science of Flying Helicopters", Mojavebooks LLC, 2003.
  8) Kaman Aircraft Corporation, US PATENT NO.676,398, "Helicopter", September 14,1950.

   6: from FAA TCDS Site
   8: from The Europe's Network of Patent Databases, esp@cenet

Back to Home

Back to Helicopter Walkarounds