Starting a Kaman K-MAX helicopter

An interesting helicopter type and one of its unique features is the way it controls the rotor blade pitch.

The Kaman K-MAX helicopter uses a unique servo-flap rotor control system rather than direct mechanical pitch links, eliminating the need for hydraulic flight control servos. Small, pilot-controlled flaps on the trailing edge of the wooden rotor blades move to create aerodynamic forces, causing the main blades to twist and change pitch. https://www.homemadetools.net/forum/...BJRU5ErkJggg==Aviation Stack Exchange +2

Key details of the K-MAX pitch control mechanism include:

Servo-Flap Control: Small trailing edge airfoils, located about 75% of the way to the tip, change the angle of attack of the main blades. When the flap moves down, the blade pitch increases, and vice-versa.
Reduced Control Forces: Because the aerodynamic forces on the flaps drive the blade pitch changes, the pilot's control inputs require much less force, allowing for a robust, non-hydraulic system that simplifies maintenance.
Internal Control System: Push-pull tubes travel down through the hollow rotor mast to the hub and then along the blades to actuate the servo flaps.
Intermeshing System: The K-MAX uses two side-by-side rotors that mesh together. The system applies differential collective pitch to control yaw and differential cyclic for pitch/roll control. https://www.homemadetools.net/forum/...BJRU5ErkJggg==Aviation Stack Exchange +4

This design makes the K-MAX highly effective for external load operations, as the system provides direct, responsive handling without hydraulic lag.

Starting a Kaman K-MAX helicopter - GIF