Traditional Helicopter – Swashplate Setup

The swashplate is designed to take the servo inputs that are based on the pilot’s pitch, roll, and collective commands and translate them to individual blade pitch inputs. There are many different servo arrangements for both three and four servo swashplates. The swashplate library covers all of the popular configurations for both three and four servo swashplates. If you have a unique swashplate, you can also use the generic three servo swashplate. Linearize servo is a feature that you can use for both three and four servo swashplates however it is optional for the three servo swashplates as there is no chance for binding. It will most likely always be required for four servo swashplates because of the potential for binding in a four point attachment.

Before You Begin

Prior to beginning the swashplate set up, be sure that your helicopter control linkages are set up in accordance with the assembly instructions. In order to make accurate blade pitch measurements, make the rotor shaft perpendicular to the ground by using shims underneath the landing gear as shown in the picture below.

../_images/TradHeli_swashplate_setup.png

Lastly it is possible if you haven’t adjusted your tail rotor linkage or your throttle linkage in the case of a gas engine that you could have binding occur while doing the swashplate set up. This is due to the H_SV_MAN feature provides manual servo settings that drive the servos to the min and max values which includes the tail rotor servo and the throttle servo due to throttle curve settings.

Select Swashplate Type

Below are the swashplate type selections using the H_SW_TYPE parameter. The diagrams shown list the servo 1, servo 2 or servo 3 for the three servo swashplate types. These correspond to the respective servo outputs in the parameters list and are the default servos for these swashplate types. For single heli, the servo function assigned to servo 1 is motor 33, servo 2 is motor 34, and servo 3 is motor 35. These assignments are the same for swashplate 1 for a dual heli frame. Swashplate 2 for a dual heli defaults to servos 4, 5, and 6 with motors 36, 37 and 38 assigned respectively. For four servo swashplates, the fourth servo on the single heli frame defaults to servo 5 and is assigned motor 37. For the dual heli frame, the fourth servo on swashplate 1 defaults to servo 7 and is assigned motor 39. The fourth servo on swashplate 2 defaults to servo 8 and is assigned motor 40. In the case of dual heli frame with four servo swashplates, the RSCHeli function (motor 31) will need to be moved to one of the aux servo outputs (9-16).

  • H3 Generic - Allows servo positions and phase angle to be set by user. Assumes all swashplate ball links are the same distance from the main shaft.
  • H1 non-CCPM - Servo1 is aileron, Servo 2 is elevator and Servo 3 is collective
  • H3-140
../_images/TradHeli_Swashplate_H3-140.png
  • H3-120
../_images/TradHeli_Swashplate_H3-120.png
  • H4-90
../_images/TradHeli_Swashplate_H4-90.png
  • H4-45
../_images/TradHeli_Swashplate_H4-45.png

Other swashplates types that can be supported

  • H3R-140 - Use H3-140. May require H_SW_COL_DIR to be reversed.
../_images/TradHeli_Swashplate_H3R-140.png
  • H3R-120 - Use H3-120. May require H_SW_COL_DIR to be reversed.
../_images/TradHeli_Swashplate_H3R-120.png
  • H3-90 - Use H4-90. Don’t use one of the servo outputs.

Check Proper Swashplate Movement

Use your transmitter to check for proper swashplate response to cyclic and collective inputs. Push forward on the elevator stick and swashplate tilts forward; pull back on the elevator stick and swashplate tilts aft. Push right on the aileron stick and the swashplate tilts right; Push left on the aileron stick and the swashplate tilts left. Push up on the throttle stick (collective) and the swashplate will rise; pull down on the throttle stick (collective) and the swashplate will lower. Set the SERVO1_REVERSED, SERVO2_REVERSED, SERVO3_REVERSED, and H_SW_COL_DIR parameters so that your swashplate responds correctly (as described above) to your collective and cyclic inputs.

Leveling your Swashplate

The swashplate can be leveled using either a tool specially designed to keep the swashplate perpendicular to the shaft or, a less expensive way, using a magnet and nail (shown below). Using the magnet and nail won’t require you to remove your rotor head to level your swashplate. Rotate the shaft so the nail passes over the swashplate arm. Adjusts swashplate using one of methods below so the nail touches the top of each swashplate arm.

../_images/TradHeli_swash_leveling.png

Leveling swashplate without using linear servo

If you aren’t using the linearize servo feature, then you will use the servo trim parameters to level your swashplate. Set the H_SV_MAN parameter to 1. Adjust the transmitter throttle stick (collective) until the servos are nearly perpendicular to the shaft. Adjust SERVO1_TRIM , SERVO2_TRIM, and SERVO3_TRIM until the swashplate is level.

Leveling swashplate using linear servo

If you intend to use linearize servo feature then you will have to level your swashplate using pitch links that connects swashplate to the servo. First though, you will set your servo so that at the midpoint of the servo travel, the arm is perpendicular to the pitch link which in most cases will be perpendicular to the shaft as well. If the spline on the servo control horn is not allowing you to get the servo arm perpendicular to the shaft, then you can use the servo trim parameters to make them perpendicular to the shaft. You want the trim as close to 1500 as you can get. Now you can adjust your pitch links to make the swashplate level.

../_images/TradHeli_linear_servo_setup.png

Setting Collective Pitch Range and Zero Thrust Point

Use the servo manual setting (H_SV_MAN ) to move the swashplate between min, mid and max positions. At each position use the blade pitch gauge to set the desired blade pitch. A typical collective blade pitch range is -2° to +10°.

Set H_SV_MAN to 2 to have swashplate move to maximum position. Adjust H_COL_MAX until blade pitch angle mesures the desired maximum collective blade pitch.

Set H_SV_MAN to 4 to have swashplate move to minimum position. Adjust H_COL_MIN until blade pitch angle measures the desired minimum collective blade pitch.

The H_COL_MID parameter is used for the collective to yaw mixing. It is also used as the lower collective pitch limit for modes that use altitude hold in the vertical axis. This keeps the autopilot from driving collective to low resulting in ground resonance. The H_COL_MID parameter is set to zero degree collective blade pitch or, if you have non-symmetrical blades, then set it to the blade pitch that produces zero thrust. In Copter 3.6 and ealier, the minimum collective pitch that the autopilot could command was done with the parameter H_COL_LAND_MIN.

Set H_SV_MAN to 3 to have the swashplate move to the mid position. Adjust H_COL_MID until the blade pitch angle measures the desired collective blade pitch that corresponds to zero thrust.

Setting Maximum Cyclic Pitch

The parameter H_CYC_MAX sets the maximum cyclic blade pitch. Checking the maximum cyclic blade pitch requires positioning the blades 90 deg to the axis that is being measured. Therefore if the longitudinal maximum blade cyclic pitch is being measured then rotate the blades until they are perpendicular to the fuselage of the aircraft (sticking out the left and right side). Measure the blade pitch with the elevator and aileron stick centered and then deflect the elevator stick full forward or aft and measure the blade pitch. The difference between the two measurements would be the maximum cyclic blade pitch corresponding to the H_CYC_MAX . The cyclic blade pitch is the same for the pitch (elevator) and roll (aileron) axes.