«TRUTRAK FLIGHT SYSTEMS 1500 S. Old Missouri Road Springdale, AR 72764 Ph. 479-751-0250 Fax 479-751-3397 Table of Contents Operating ...»
TRUTRAK FLIGHT SYSTEMS
1500 S. Old Missouri Road
Springdale, AR 72764
Ph. 479-751-0250 Fax 479-751-3397
Table of Contents
Mode and Data Display
GPS Steering/GPS Nav Mode
NAV/Loc Course Mode
Reverse Course Mode
Gyro Back-Up Mode
Altitude Hold Mode
Vertical GPS Steering Mode
Altitude Select Mode
Stopping the Transition to a Selected Altitude........... 15 VNAV Mode
Additional Operating Instructions Initializing the Autopilot
Altitude Select with AP Off
Engaging the Autopilot
Setting Pitch Trim
GPSS Missed Approach Function
Setup Procedure Lateral Setup
3 General Introduction The TruTrak autopilot can be defined as being an orthogonal rate system.
This means that gyroscopic rate sensors sense motion about each of the major axes (roll, pitch and yaw). These sensors generate the fast signal responses necessary to create an autopilot with the best possible dynamic performance.
To fly an aircraft well about the axis controlled by the ailerons, velocity of aileron movement must be directly proportional to the rate of roll for small movement. This means that aileron position corrections do not lag behind motion of the craft about the roll axis. Aileron control systems that use a turn coordinator, which senses twice as much azimuth as roll rate, cannot do this. Instead, yaw disturbances in turbulence cause undesired aileron movement. In some aircraft this effect is so severe that the controls may even momentarily move in the wrong direction.
The goal at TruTrak is to create systems with the very best dynamic performance available—systems that do not need to be disengaged in turbulence, but instead provide function when needed most.
The complete TruTrak autopilot system combines all the electronic and sensing elements needed for the roll and pitch functions within a single panel-mounted programmer/computer package. A rate-gyro-controlled yaw damper can be added to the system.
Basic directional control is provided by digital selection of a GPS track.
This replaces heading selection on the DG and eliminates drift as well as crosswind correction. In the GPS steering mode of operation, the system responds to digital guidance information to fly a complex navigation program.
The vertical portion of the system contains a digital altimeter and associated altitude selector with selectable increments as small as fifty feet.
Altitude transitions can be made by airspeed, vertical speed, or horizontal distance (VNAV) selection. If an upward vertical speed is selected which is beyond the capability of the aircraft, there will be no stall. Instead, the autopilot will cause the aircraft to climb at a pre-set minimum safe airspeed.
This is the only known system to provide this safety feature.
For any set of features all TruTrak computers are identical. Servos likewise are identical in velocity response. Servos do differ according to total torque required. By providing setup functions in the programmer for system activity and torque, one TruTrak programmer-servo combination can fly any aircraft.
As a starting point in understanding how to operate the TruTrak system, the following describes the presentation of data, the operating controls, and the procedures for selecting modes of operation.
4 Autopilot Power Up The autopilot master switch should be in the off position when the engine is started. Aircraft electrical systems can generate voltage transients during an engine start and like other avionics systems, the autopilot should not be subjected unnecessarily to these conditions.
After start up, turn on the autopilot master switch and keep the aircraft stationary as the internal gyros are initialized. This takes approximately ten seconds during which time the display will show the words PWR UP in the lower right. When initializing is complete PWR UP will change to AP OFF.
Mode and Data Display The display shows operating modes and associated data. It is also used to display setup mode screens and their values. When displaying operating modes, the left side shows lateral data and the right side shows vertical data. NO GPS will be displayed in the top left of the display when no GPS signal is detected. A flashing period will appear when a GPS signal is detected, but no position information is available. The words NO FIX will be displayed. Once GPS position data becomes valid a flashing asterisk will appear and the display will show GPS OK. If GPS flight plan information is being received over the serial channel or if GPS steering information is being received, a flashing plus sign will be shown in place of the asterisk.
The upper left display is labeled TRK, showing the electronic DG slaved to GPS track. When the GPS track is not available, TRK will be replaced by BANK. This means the autopilot is using its internal gyros for bank angle control. The lower left display labeled SEL shows the selected GPS ground track when in the standard track mode. When in the gyro mode, the lower left shows the current selected bank angle. The upper right display shows altitude or selected altitude, and the lower right display shows either selected vertical speed or selected airspeed.
Underlined numbers indicate a value that can be adjusted by rotating the knob. A sample of the display is shown below.
5 Sorcerer Setup Procedure In the Sorcerer setup screens, pressing VS UP on the rocker switch will advance the page to the next setup screen. Pressing VS DN will return to the previous screen. All values are changed by rotating the knob. Pressing the knob will exit the setup mode.
Lateral Setup To enter the lateral setup mode, press and hold the TRK button for two or more seconds until the first setup screen appears. This screen shows the current value for the LAT ACTIVITY. Any value between 0 and 24 may be chosen. In this example, the value of 3 is selected. The higher the number is set, the faster the servo moves the control system.
Too low of a setting will cause hunting, too high of a setting will cause hunting and the servo to be overactive and jitter. (Any lost motion or play between the servo and the control surface can cause hunting in still air).
The next setup screen is for adjusting LAT TORQUE. This determines how much torque the roll servo is allowed to apply with 12 being the maximum. A default value of 12 is set at the factory but may need to be modified to suit a particular aircraft or pilot. Trutrak recommends a setting of 12 for all aircraft. If the torque setting is too low the AP may not be able to control the aircraft in all flight conditions. This could cause the aircraft to drift off selected track.
The next screen shows the RS-232 input BAUD rate setting. The default setting is 9600. Consult the Sorcerer installation manual for information on how to setup some GPS receivers to properly communicate with the Sorcerer AP.
6 The next screen shows the BANK ANGLE adjustment. It is adjustable to LOW, MED, or HI. This will limit the AP bank angle to approximately 13°, 18°, and 24° respectively. This setting has no effect on the GPSS mode. It only affects GPS TRK and GPS NAV modes.
The next screen is the MICROACTIVITY. This setting is used in cable controlled systems to remove any slack or lost motion introduced by the cables. This setting should be left at zero unless advised by the factory.
Advance to the next setup screen. This is the GPSS GAIN setting. This setting should be left at 16 unless advised by the factory.
The next setup screen is SPEECH. This setting turns the speech annunciation on and off. If the speech is turned off, the autopilot will give a series of alerter tones for important information. If the speech is turned on, there will be a voice annunciation for important information.
The next setup screen is for AUDIO LEVEL. While this screen is displayed, the autopilot will send an audio tone to the audio system.
Adjust the value between 0 and 16 for the desired volume.
The next screen is the EXT DG/HSI selection. Use the knob to select either Y (yes) or N (no) depending on whether an external DG or HSI is connected to the system. Leave setting at N for Garmin G3X.
The next screen is the YAW DAMPER selection. Select Y (yes) or N (no) to indicate whether or not a yaw damper is present. If N is 7 selected, this is the final lateral setup screen. Click the knob to exit the lateral setup mode. If Y is selected push VS UP on the rocker to advance to the next setup screen.
If the YAW DAMPER? was answered with Y, then the next setup screen will be for YD LEVELING. This is the fine adjustment for the yaw damper to maintain a ball centered condition. The value is adjustable from -8 to 8 and is used as necessary to have the yaw damper keep the aircraft slip/skid indicator (ball) centered when the yaw damper is engaged and the autopilot is flying the aircraft straight and level.
When adjusting this value, allow a few seconds for the yaw damper to respond to each new value setting.
The final setup screen is for yaw damper activity. The yaw damper activity functions exactly like the lateral and vertical activity settings. This setting is adjustable from 0 to 12, where 0 is the lowest activity and 12 is the highest activity.
Vertical Setup To enter the vertical setup menu, press and hold the ALT button for two or more seconds until the first setup screen appears. This screen is the VRT ACTIVITY adjustment. Any value between 0 and 24 may be chosen. Choose a level that gives the best overall performance in all modes of flight.
The next setup screen is for VRT TORQUE. Any value between 0 and 12 may be selected. A default value of 12 is set at the factory.
8 Trutrak recommends a setting of 12; however the value may be lowered to suit pilot comfort level.
The next setup screen is the MIN AIRSPD setting. This value is displayed in knots Indicated Airspeed. This value should be set above the clean stall speed of the aircraft, but not so high as to interfere with maneuvering with the autopilot engaged.
The next screen displayed is the MAX AIRSPD setting. This value is also displayed in knots Indicated Airspeed. It should be set safely below the redline IAS of the airframe, but not so low as to interfere with maneuvering with the autopilot engaged.
The next screen is the NORM CLIMB setting. This value is the default indicated airspeed value selected when an altitude select is entered above the current altitude.
The next screen is the STATIC LAG adjustment. This allows the user to compensate for lag in the static system of the aircraft that causes pitch oscillations in calm air. Select the lowest value over the range 0 to 2 which results in the elimination of “hunting” in the altitude hold mode.
This adjustment should be done in still air at cruise airspeed.
The next setup screen is MICROACTIVITY. This setting should be left at zero unless advised by the factory.
The final screen is the HALF-STEP setting. Most of the time, this setting will not need to be adjusted. When it is set to Y (yes), then the pitch servo will have a higher resolution and take smaller steps.
However, it will also have less available torque. This setting should be 9 left at N (no) unless the nose of the aircraft moves up and down very slightly in very still air.
Push the knob to exit the setup menu.
Controls The autopilot can be engaged in one of three ways; (1) Pushing the AP button; (2) using the control wheel steering switch; (3) pressing the GPSS button when a GPSS steering signal is available. The CWS (Control Wheel Steering) switch is a momentary switch that should be located on the stick/yoke for accessibility. When this switch is held closed for 1.5 seconds from a disengaged state, the AP will engage. If held closed for 1.5 seconds from an engaged state, the AP will enter CWS mode. When the switch is momentarily closed (pressed and released) from an engaged state, the AP will disengage.
Lateral Modes When the autopilot is engaged it will synchronize to the current GPS ground track. At this time the cursor will be located underneath the numbers indicated by SEL on the display. The desired ground track can be changed by rotating the knob to select a new track. Rotating the knob will increment the selection by 5°. Pressing and holding the knob while rotating will give 1° increments.
Pushing the TRK button at any time will return the autopilot to the basic track selector mode.
When an external heading source (DG or HSI) is present and turned on, pressing EXT will engage the external DG mode. When in this mode, the heading “bug” within the external DG or HSI will control the direction that the autopilot flies. For use with a Garmin G3X system, the EXT button will still follow the heading bug of the PFD, but N must be selected in the lateral setup menu.
GPS Steering (GPSS)/GPS Nav Mode/GPSV Pressing the GPSS button will enter either GPS Nav or GPSS mode.
The type of steering command that is available will determine how the autopilot will fly a flight plan programmed into the GPS.
10 If only NMEA (RS-232) GPS information is available, the autopilot will overfly each waypoint prior to turning and intercepting the course line to the next waypoint.
With ARINC steering commands, the autopilot will follow lateral steering or bank commands generated by a navigation system (EFIS or GPS). This means the autopilot will round corners and not overfly the course line to the next waypoint. The display will indicate when the autopilot is in one of these modes by displaying GPSS in the bottom left of the display.
The vertical GPS Steering mode (GPSV) is also engaged with GPSS if the signal is present. If the autopilot is engaged during a climb or descent, you must either zero the vertical speed with the rocker switch or press the ALT to engage GPSV. The vertical steering can be decoupled by selecting any other vertical mode. To re-engage the vertical steering, press GPSS again, then press ALT or set the SVS to 0 using the rocker switch.