Over the years, operators have sent Duncan Aviation's Avionics & Instrument Shop a number of inoperable JET Yaw Damper (YD) Computers for repair. They are quick to blame the PWR/TEST or Engage buttons as the culprits, but what they really should be looking at is the OFF switches.
The four OFF switches on these YD units are well known for becoming intermittent and stuck, causing the YD to not function.
If the PWR/TEST or ENG light won’t come on when pushed, the corresponding OFF switch has probably gone bad. Snapping this OFF switch a few times may help the unit to re-engage.
The FAA requires two functioning Yaw Damper (YD) Computers during all flights. If one suddenly quits, your aircraft is grounded. A potential temporary fix is to cycle through all of the OFF buttons by snapping them. This may cause them to re-engage so your flight can continue.
Once you get back home, send this unit to Duncan Aviation for repair. We have loaner units available while it is being fixed.
At Duncan Aviation, we have been working on JET Components for more than 45 years. On average, we repair around 700 JET components each year with Current Manual data.
In addition to the Yaw Damper Computers, Duncan Aviation's Avionics & Instruments Shop has repair capabilities on the following units:
FC-110 Flight Control System
AD-101() Air Data Computer
AD-102() Air Data Sensor
CA-260()/CA-261() Dual Fuel Monitoring System
IA-201B Interface Adapter
CA-200() Autopilot Computer
MT-101() Mach Trim Computer
SP-101() Spoileron Computer
YD-202() Yaw Damper Computer
SA-500()/SA-501() Servo Actuator
SA-400() Nose Wheel Steering Actuator
MW-701 Malfunction Warning
SA-200() Servo Actuator
SA-460() Servo Actuator
SA-461() Servo Actuator
VG-206A Vertical Gyro
VG-206B Vertical Gyro
VG-206C Vertical Gyro
VG-206E/L Vertical Gyro
VG-206F/L Vertical Gyro
VG-206G/L Vertical Gyro
TDR 94/94D Common Error Codes
Aircraft Compass System Alignment Formulae