BFF CL Software - Short User Guide


 

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4. Force Feedback Tuning Procedure

Force tuning settings are made in Tabs 1, 2 and 3 of the Configuration Manager.

IMPORTANT - force tuning should be done AFTER the system is fully setup and commissioned - see the Configuration Manager Tab 9 steps and the project build documentation.

Actual levels of force output will be different for different flight control designs - it is not possible to have a single configuration that will work for all installations. Additionally some users may not use some of the force features, so you may wish to adjust the settings to suit your own preferences.

The best way to adjust the settings is to disable ALL force components other than the one you are working on (use the check boxes for each setting to enable/disable it). Then place and pause the aircraft in a flight situation which will generate the required loading conditions. The gains associated with the force component can then be adjusted and made-active in the Configuration Manager and tested by engaging the force feedback through the CL Software.

The main force components and relevant flight situations are below - it may be helpful to make the adjustments in the order given. Note that Tabs 1, 2 & 3 give SEPARATE settings for each control axis. The comments below refer to Tab 1 - Elevator, but they also apply to Tabs 2 & 3 - Aileron and Rudder

Once the basic settings have been made check the response over a range of flight conditions and adjust as required.

  1. Main Control Surface Lift Force:

    Enable the main lift force (Tab 1 Item 1 - Lift Gain). Disable all trim, propwash, alpha, weight and vibration force elements. Place and pause the aircraft in straight and level flight at the normal cruising speed for the aircraft. Adjust the Lift Gain and click the Make-Active button, then Engage the force output in the main CL software to test the force levels.

    Increasing the gain will increase the stiffness of the controls. The stiffness will also vary with varying airspeed - but setting at normal cruise speed should give a reasonable benchmark at the upper end of the loading. The Tab 5 Item 16 - AS_Exp parameter sets the power to which the airspeed is raised in the force calcs. So AS_Exp=2 sets stiffness proportional to airpseed squared and may be suitable for GA aircraft. AS_Exp=1 will make stiffness linearly proportional to airspeed and may be more suitable for fly-by-wire heavy or fast jets.

    If the force progress bars routinely go to maximum during NORMAL control displacements before you feel reasonable force output then it is likely that the overall force output of the system is not adequate. Re-assess the motor transmission gearing ratios, check the power supply voltages when under load (is the supply capable of delivering the current required).
     

  2. Trim Force:

    Enable the trim lift force (Tab 1 Item 2 - Trim Gain). Disable all propwash, alpha, weight and vibration force elements. Place and pause the aircraft in straight and level flight at the normal cruising speed for the aircraft. Adjust the Trim Gain and click the Make-Active button, then Engage the force output to test the trim adjustment direction and the force levels. The trim direction can be reversed by reversing the sign of the gain.

    Note that without airflow over the control surfaces there will be no trim forces generated unless a Tab 1 Item 6 - Min Air Speed has been specified..
     

  3. Alpha (Angle of Attack Effects):

    Enable the Alpha effects by specifying a Tab 1 Item 4 - Alpha Gain of -1.0. With the main lift force and trim force settings made place the aircraft in straight and level trimmed flight at the normal cruising speed for the aircraft. With the flight active Porpoising the aircraft should induce short surges in the centring forces at the elevator as the aircraft angle of attack varies with the nose-up, nose-down motion of the aircraft.

    If the Alpha Gain value has the incorrect sign the force variations will be felt as reductions in the centring forces as the aircraft porpoises.

    Adjusting the Alpha Gain will also affect the magnitude of the out-of-trim forces that arise when the aircraft airspeed changes and its pitch angle adjusts to the new airspeed.
     

  4. Prop-Wash Loading:

    Enable the Tab 1 Item 3 - Propwash loading. Disable all weight and vibration force elements. Place the aircraft stationary on the runway, apply the brakes. Apply engine power to generate airflow over the control surfaces - this will induce propwash loading on the axis concerned which will drive the controls towards mid position. Assess the strength of this loading and adjust the Propwash Gain to suit.
     

  5. Elevator Weight Effects:

    If you wish to feel static (or dynamic) weight effects on the elevator uncheck the Tab 1 Item 25 - Balanced checkbox. Place the aircraft stationary on the runway. If propwash loading is active make sure the engine power is removed.

    When the FFB is engaged the elevator should pull forward to simulate the static weight of the controls. Adjust the Mass Gain to tune the force level. Reversing the sign of the Mass Gain value will reverse the static loading.
     

  6. Engine Vibration:

    Untick the Tab1 Item 21 checkbox to enable the engine vibration effects. With the aircraft stationary on the runway and brakes applied throttle up the engines. The engine vibration effects should be felt through the controls - they will vary in magnitude with the engine thrust and in frequency with the engine rpm.

    Adjust the Gains to tune the vibration effects to set the maximum vibration against maximum engine thrust.

    The Item 19 - checkbox can be unchecked to enable a minimum engine vibration which will always be on when the FFB is engaged. Adjust the adjacent Gains to set a low level minimum engine vibration effect.
     

  7. Runway Vibration:

    Temporarily disable the engine vibration effects.

    Untick the Item 17 checkbox to enable runway vibration effects. Place the aircraft on the runway and proceed with take-off; pause the sim when you reach your maximum takeoff speed before the aircraft leaves the ground.

    Adjust the Gains to set the runway vibration magnitudes and frequency. They will vary in magnitude and frequency with runway speed. Once set check the effects over the full raange of runway speed to check both low and high speed feel.
     

  8. Stall Vibration:

    Temporarily disable the engine vibration effects.

    Untick the Item 15 checkbox to enable stall vibration effects. Place the aircraft in a stall and pause the sim.

    Adjust the Gains to set the stall vibration magnitudes and frequency. They will vary in magnitude with relative angle of attack so the stall vibration should begin as the aircraft approaches stall.

NOTE if your mechanical controls have significantly more inertia than the flight yoke designs on the web site the vibration force cap levels may need to be raised. This can be done by altering the flash programming on the card. Please contact me for information and instructions if you wish to do this.

 

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