A helicopter swashplate transfers stationary control inputs to the rotating rotor system. The FAA describes a stationary plate restrained from rotation and a rotating plate that turns with the mast; the pair can tilt and move vertically together. Pitch links connect the rotating plate to blade pitch horns. The calculator below models only the geometric vertical position of an ideal link attachment around a tilted plane.
Swashplate Interactive Calculator
Vary entered collective offset, cyclic tilt, link radius and rotor speed. The ideal plane model reports vertical link-position amplitude and one-per-revolution frequency; it is not a rotor-control or airworthiness calculation.
Equation Used
- The calculator samples an ideal tilted plane along a circular horizontal path. It does not calculate the motion of a physical bearing, drive link or pitch-link assembly.
- Collective and cyclic inputs are independent entered geometric scenarios.
- The cyclic high side is defined at psi = 0 degrees.
- Blade pitch, phase lag, control mixing, compliance, loads, dynamics and aircraft response are not calculated.
How a Helicopter Swashplate Works
The FAA describes two plates. The stationary swashplate is restrained from rotating but can tilt in any direction and move vertically. The rotating swashplate turns with the mast; both plates tilt and slide together. Pitch links connect the rotating plate to pitch horns on the rotor blades.
Collective control moves the assembly vertically. Cyclic control tilts it, so a rotating link attachment rises and falls once per revolution. NASA describes independent lateral cyclic, longitudinal cyclic and collective control, with collective translation and cyclic tilt producing the intended rotating-frame pitch variation.
Using the Animation and Calculator
The animation shows paired circular bearing rings: a stationary ring receiving control inputs and a rotating ring with link-attachment joints. Collective translates the pair and cyclic changes their tilt. Ring sizes and control rods are illustrative; pitch links and blades are omitted. The calculator separately samples a tilted plane at a fixed horizontal radius, which is not a physical bearing track.
It does not turn that height into blade pitch or aircraft response. Real systems require verified linkage geometry, phase convention, travel limits, bearings, strength, redundancy, dynamics, controls, maintenance data and approved airworthiness information.
Ideal Tilted-plane Geometry
For collective datum offset h, horizontal link-path radius r, tilt beta and azimuth psi:
The cyclic amplitude is A = r tan(beta). The high and low ideal positions are h + A and h - A. One-per-revolution frequency is rotor rpm divided by 60.
Worked Example: Entered Geometric Scenario
For h = 50 mm, beta = 15 degrees, r = 250 mm and 400 rpm, A = 250 tan(15 degrees) = 67.0 mm. The ideal high position is 117.0 mm, the low position is -17.0 mm relative to the chosen datum, and one-per-revolution frequency is 6.67 Hz.
The negative low value is a coordinate relative to the arbitrary datum. These results do not specify blade pitch, allowable travel or a safe control system.
What the Calculator Includes
- Established by the cited sources: paired stationary and rotating swashplates, vertical collective translation, cyclic tilt and pitch-link transfer to rotating blades.
- Calculated: ideal link-height amplitude, high and low coordinate positions, and one-per-revolution frequency.
- Not calculated: blade pitch, pitch-horn ratio, phase advance or lag, flapping, control mixing, actuator travel or force, loads, fatigue, vibration, dynamics, failure cases or airworthiness.
Frequently Asked Questions
Which plate rotates?
The rotating member follows the mast; the stationary member receives the non-rotating control inputs. Their exact arrangement depends on the assembly.
What does collective do in this model?
It adds the same entered vertical datum offset to every ideal link position.
What does cyclic tilt do?
It produces a sinusoidal height variation around rotor azimuth, with amplitude r tan(beta).
Why can the low position be negative?
The output is a coordinate relative to an arbitrary datum, not a physical link length.
Does link height equal blade pitch?
No. Blade pitch depends on pitch-horn and linkage geometry that this calculator does not model.
Can this calculator size a flight-control system?
No. Loads, travel limits, strength, redundancy, dynamics and airworthiness requirements are outside its scope.
References
- Federal Aviation Administration, Helicopter Flying Handbook: stationary and rotating swashplate arrangement, collective and cyclic control, and pitch-link connections.
- NASA Technical Reports Server, rotor control patent record: independent lateral cyclic, longitudinal cyclic and collective inputs; collective translation and cyclic tilt.
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