The third axis your SkyView autopilot has been missing.
WYMMS-1 adds a dedicated yaw-moment servo to any two-axis Dynon SkyView autopilot installation. It measures the asymmetric yaw produced by wing loading, slipstream, and P-factor in real time, and trims it out before you ever feel the ball move.
FIG. 1 — WYMMS SERVO STATUS PAGE, SKYVIEW HDXREPRESENTATIVE
01 Overview
Why manage yaw-moment?
Two-axis autopilots hold heading and altitude, but leave the rudder to the pilot. Every change in power, airspeed, or bank produces a yaw-moment the airplane has to absorb somewhere: in the ball, in the passengers, and in your right leg. WYMMS-1 closes that loop with a dedicated servo driven by the SkyView ADAHRS.
01.1
Coordinated by default
The control module samples lateral acceleration and yaw rate at 316 Hz and commands the servo to null the residual yaw-moment. The ball stays centered without your feet on the pedals.
01.2
Right-seat comfort
Uncoordinated flight is what makes passengers reach for the bag. WYMMS-1 was tuned for smooth, passenger-first ride quality, especially in the turns and the descent.
01.3
Native to SkyView
No separate control head. WYMMS-1 appears as a third servo in the SkyView autopilot setup menu, with its own status, calibration, and engage/disengage logic on the SV-AP-PANEL.
02 System
How it works
WYMMS-1 rides on the existing SkyView Network. The correction is continuous rather than commanded: once it is set, it simply holds the course. The control module listens to the ADAHRS, computes the yaw-moment correction, and drives the servo through the same slip-clutch architecture as the pitch and roll servos. If the module ever loses network, the servo goes limp and the pedals are yours.
SENSEADAHRS yaw rate and lateral acceleration, 316 Hz.
ESTIMATEControl module computes residual yaw-moment from airspeed, AOA, and power.
ACTUATEServo commands rudder deflection through a slip-clutch pushrod.
PROTECTLoss of SV-NET, over-current, or pilot pedal force disengages the servo.
03 Data
Specifications
All values at 25 °C, 14 VDC unless noted. Refer to WYMMS-IM-0406 (Installation Manual) for airframe-specific limits.
Servo — WYMMS-1
Part number
316-WYMMS-1
Rated torque
42 in·lb (4.75 N·m)
Slip-clutch range
8 – 42 in·lb, adjustable
Output
Arm, 1.25 in / 1.75 in hole spacing
Slew rate
60°/s no-load
Weight
2.8 lb (1.27 kg)
Envelope
4.03 × 3.16 × 3.17 in
Mount
4 × AN3, flange pattern 3.50 × 2.00 in
Operating temp
-30 to +55 °C
Control module — WYMMS-CM
Part number
317-WYMMS-CM
Input power
10 – 30 VDC, 0.4 A idle, 2.6 A peak
Interface
SkyView Network, DB-9
Loop rate
316 Hz
Weight
0.6 lb (0.27 kg)
Envelope
3.30 × 2.20 × 1.05 in
Firmware
4.3.22, field-updatable via SkyView USB
SkyView software
17.2 or later
Circuit protection
5 A breaker, dedicated
Kit contents
316-WYMMS-1
Servo assembly
317-WYMMS-CM
Control module
324-WYMMS-HRN
SV-NET harness, 6 ft
330-WYMMS-BRKT
Universal bracket + hardware
WYMMS-IM-0406
Installation manual
WYMMS-CL-0410
Servo activation checklist card
04 Fitment
Compatibility
WYMMS-1 requires an existing two-axis SkyView autopilot. It is a servo expansion, not a standalone autopilot, and does not replace the pitch or roll servo.
Avionics
SkyView HDX (SV-HDX800 / SV-HDX1100) SUPPORTED
SkyView Classic (SV-D700 / SV-D1000) SUPPORTED
SV-AP-PANEL REQUIRED
SV-ADAHRS-200 / -201 REQUIRED
Existing SV32 / SV42 / SV52 servos ANY
SkyView SE NOT SUPPORTED
Airframes
Experimental / amateur-built ALL
Light-sport (S-LSA with MRA) ALL
Cessna 172 (F–S) AML-STC
Cessna 182 (P–T) AML-STC
Piper PA-28 series STC PENDING
Beechcraft 35/36 STC PENDING
NOTE Certified installations must be performed by an authorized SkyView installer and returned to service under the AML-STC. Contact support for the current approved model list.
05 Procedure
Installation overview
Typical installation is 6 to 9 shop hours plus one validation flight. Full procedure in WYMMS-IM-0406. It is a permanent installation; there is no removal procedure.
Locate the servoMount the servo on the aft rudder bellcrank or the tailcone rudder cable run using the universal bracket. Verify pushrod geometry through full pedal travel.
Mount the control moduleBehind the panel or on the avionics shelf. Keep at least 12 in from the ADAHRS and away from strobe power supplies.
Wire SV-NETDaisy-chain the harness from the last existing SkyView Network device. Add a dedicated 5 A breaker for module power.
Configure in SkyViewSETUP > AUTOPILOT > SERVOS > YAW-MOMENT. Assign the servo, set direction, and run the calibration wizard.
Set the slip clutchAdjust to the airframe value in the manual. Confirm the pilot can override the servo with normal pedal force.
Fly the activation checklistPerform WYMMS-CL-0410 in smooth air. Confirm the ball stays centered hands-off through turns and power changes, then record servo current in the aircraft log.
06 WYMMS-CL-0410
Servo activation checklist
Every WYMMS-1 installation is signed off with one activation flight. The checklist card lives in the cockpit and walks the pilot through preflight checks, first engagement in cruise, and a short set of coordination checks before the servo is left in service.
Flow items are read challenge-and-response. A second crew member may read the challenges; the pilot in command performs and confirms each item.