THE MINISTAB SYSTEM
Identify the general characteristics and functions of the MINISTAB system.
A basic three axis system (pitch, roll, and yaw) with force trim designed to provide attitude retention and to smooth pilot input to the controls (rate dampening). It also provides altitude hold in cruise flight (above 40 kts).
Identify the controller buttons and their functions.
STAB:Engages and disengages the flight control system
FT:Engages and disengages the flight control system
ALT:Engages and disengages the altitude hold mode.
TEST:Initiates a test of the MINISTAB system.
Identify the functions of the force trim and STAB buttons found on the cyclic.
Force Trim: When pushed ministab goes in standby and force trim gradient is disengaged. When released Resets ministab and force trim systems.
STAB:Turns ministab on and off.
Describe the functions of the trim damper units.
The pitch and roll actuators are located at the top of the control tubes and provides input to the hydraulic servo pilot valves. Therefore they have a low output force. The pitch and roll computers provide a signal to the actuators which move about a neutral point (0.5 inch total movement NATOPS 2.12.5 pg 2-28, 1.0 total movement Systems Workbook (CNATRA P-402 (rev. 7-98))) to maintain attitude.
The yaw actuator is connected to the tail rotor control tube. Since the tail rotor flight controls do NOT have hydraulic boost. The tail rotor actuator is larger and has a temperature cutoff switch.
The Trim Damper Units (TDUs) provide force trim and smoothes / dampens pilot input. Pitch and Roll FT switch is on the cyclic, Yaw FT is on anti-torque pedals
Identify the major components of the MINISTAB system and state how they function independently and together in the flight control system.
Air Data computer
The junction box interconnects components of the system. Each axis computer contains a rate gyro, memory circuit (integrated rate), and integration cutoff (ICO) circuit. Within each computer, the rate gyro senses movement about its axis, allowing the computer to detect any deviation from the attitude stored in the memory circuit. The computer then sends a correction signal to the actuator which makes the appropriate control input. This is how aircraft attitude retention is provided.
The air data computer contains transducer that sense airspeed and altitude changes and it also incorporates an airspeed trip switch. The airspeed trip switch tells the FCS when the helicopter is above 40 kts indicated airspeed. This switch works in conjunction with altitude hold and the yaw axis computer.