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Appendix D. Heavy Jet Mode 1.

In its default mode the BFF CL software operation reflects the behaviour of simple GA aircraft with reversible flight controls. In V1.21 of the CL software (with v1.310 of the background process) I've added an operating mode that may be more suitable for some Heavy Jets (Use_FSTrim=10).

Heavy Jet Mode 1 is only available when the system is configured for Pot-less Operation. This is to allow the CL software to control the flow of position data to FSX selectively for each axis.

In this mode the trim and A/P following behaviour of the controls differs from that for the default.

Reminder - In default (GA) mode.... It may be helpful to provide a quick reminder of the default system behaviour.

• Elevator
  
  CL system trim is active (FSX internal trim is disabled - by removing the trim input assignments in FSX) - trimming then causes the force balance on the elevator axis to change, which allows the elevator to be brought into force balance (hands-off condition) where the pilot is holding it. So non-mid hands-off positions can be trimmed.
  
  When A/P is engaged the CL system moves the main elevator axis to simulate the pitch control actions of the (native) FSX A/P. When this is happening the position input to the FSX controls is disconnected (you will not see the FSX cockpit controls move). If auto-trim adjustment is active it will also adjust elevator trim so that the net force on the elevator is zero when A/P is disengaged.
   
• Aileron
  
  Similar to the elevator axis -
  
  CL system trim is active (FSX trim is disabled) - trimming causes the force balance on the aileron axis to change, which allows the aileron to be brought into force balance (hands-off condition) where the pilot is holding it. So non-mid hands-off positions can be trimmed.
  
  When A/P is engaged the CL system moves the main aileron axis to simulate the bank control actions of the (native) FSX A/P.
   
• Rudder
  
  Trim operation is similar to the elevator axis -
  
  CL system trim is active (FSX trim is disabled) - trimming causes the force balance on the rudder axis to change, which allows the rudder to be brought into force balance (feet-off condition) where the pilot is holding it. So non-mid feet-off positions can be trimmed.
  
  FSX native A/P does not use rudder movement for control. When A/P is engaged there is no movement of the rudder pedals - they are held at mid position. The rudder pedals are also disengaged from FSX along with the other two axes.
  
  (Update: for BLDRV-12/24 20X2 programming R35+ in GA mode the rudder axis remains loaded when A/P is engaged, but the position feed to FSX via FSUIPC remains disconnected. This is also the case for all CL_SPU cards).
   

In Heavy Jet Mode 1 the behaviours are different...

• Elevator
  
  CL trim input now drives the FSX internal trim, and disables the CL system elevator axis force adjustment. This causes the elevator axis to exhibit only one hands-off position - at mid position. In effect the trim input moves the aircraft stabiliser whilst leaving the elevator axis at mid position; this replicates the native FSX elevator trim behaviour.
  
  When A/P is engaged the elevator remains stationary at mid; and the CL trim position now follows the FSX internal trim position. The native FSX A/P controls pitch using elevator trim, and the CL trim (and indicator outputs) will follow this. When A/P is disengaged the CL trim input returns to driving the FSX internal trim position.
  
  This A/P trim following behaviour requires that trim buttons or switches are configured for the elevator axis; it does not operate if trim pot is configured.
  
  Whilst A/P is engaged the control loading on the elevator axis now remains active and position input to FSX remains active also (although FSX will attenuate the elevator control authority heavily whilst its A/P is active so there's not much point in moving it). In any case displacing the elevator position away from mid will cause A/P to disengage.
  
   
• Aileron
  
  The behaviour of the aileron axis remains the same as for the default GA mode...
  
  CL system aileron trim is active (FSX aileron trim is disabled) - trimming causes the force balance on the aileron axis to change, which allows the aileron to be brought into force balance (hands-off condition) wherever the pilot is holding it. So non-mid hands-off positions can be trimmed.
  
  When A/P is engaged the CL system moves the main aileron axis to simulate the bank control actions of the (native) FSX A/P. When this is happening the position input to the FSX aileron control is disabled (so you will not see the FSX cockpit aileron move).
  
   
• Rudder
  
  Trim operation is similar to the default GA mode -
  
  CL system rudder trim is active (FSX rudder trim is disabled) - trimming causes the force balance on the rudder axis to change, which allows the rudder to be brought into force balance (feet-off condition) where the pilot is holding it. So non-mid feet-off positions can be trimmed.
  
  However A/P behaviour is different - when A/P is engaged the rudder pedals do not move, they remain loaded and continue to drive FSX rudder position (although FSX is likely to heavily attenuate this input whilst its A/P is active).
   

Additional Features

In addition to the above trim and A/P following behaviours two other features have been added to use with Heavy Jet mode (although they can also be used in the default GA mode). These parameters can be set using the Configuration Manager.

1. (Force) Neutral position shift
   
   Parameter Tab 5 Item 9 Neutral_Pos_Offset_E can be set to define the neutral (or zero force) position shifted away from elevator axis mid range position. This can be helpful in some mechanical setups.
   
   Example, Neutral_Pos_Offset_E=20 will set the zero-force position at +20% of the column's half-range movement. This will then be the zero position at which the CL system will base its force calculations; it will be the natural hands-off position, assuming no fixed force components are configured which will cause a shift in position.
   
   Note that the position shift will NOT be visually apparent in the FSX virtual cockpit controls, but it will be present in the physical controls.
   
   Requires dsPIC firmware V41 or later.
   
   If you use this setting you may also want to use the Tab 4 Item 8 setting to set the mid-position for A/P position following.
    
2. Rudder Position Scaler
   
   Parameter Tab 5 Item 15 Rudder_Pos_Scaler can be set to scale down the position input from the rudder axis to FSX.
   
   Example, setting Rudder_Pos_Scaler=0.75 will reduce the rudder position sent to FSX to 75% of the actual rudder pedal position.

Important Pre-requisites for using Heavy Jet Mode 1:

1. Driver card 20x2 chip firmware version 35 (or later) is required or any CL_SPU programming.
    
2. For the Neutral Position Shift feature Driver dsPIC chip firmware version 41 (or later) is required.
    
3. CL software v1.210 and background process v1.310 (or later) are required.
    
4. The CL software and older BLDRV-12/24 driver cards MUST be set for Potentiometer-less mode.
    
5. Trim input for the elevator axis must be by buttons and not by potentiometer.
    

Configuration Settings:

1. Open the Configuration Manager and a "Heavy" configuration file to start with. Go to Tab 5 and select Item 18, and then click Update_Mode.
   
   This will enable heavy jet mode (Use_FSTrim=10), and make sure pot-less mode is set.
    
2. If you wish to use the Neutral Position Shift feature set Tab 5 Item 9 Neutral_Pos_Offset_E to the required shift (as a %tage of the column 1/2 range movement). You may need to experiment to determine if a +ve or -ve shift is required on your set up.
    
3. To use the Rudder Position Scaling feature set Tab 5 Item 15 Rudder_Pos_Scaler to the required scaling factor (range 0-1.0).
    
4. Trim buttons rather than pots MUST be used for the elevator axis - so in Tab 7 Item 8 (Line 47: Alt trim joystick no. -buts) set to specify the joystick card to be used for the elevator axis trim buttons. Items 9 & 10 are used to specify the buttons on the card.
   
   If pot based trim input is needed for either the aileron or rudder axes then Items 2 & 3 can be used - please read the description fields for more information.
    
5. Item 15 (Line 54: Button trim rate) may need to be adjusted to give the required elevator trim adjustment rate when the trim button is operated. Reducing the value will slow down the speed of response of the resulting trim movement.
    
6. Tab 4 Item 13 (Line 44: Elev AP Disengage Trigger) can be set to control the amount of displacement of the elevator required to cause A/P disengage.
    
7. SAVE the configuration settings.
    
8. NOTE: Breakout settings on the elevator axis can be usefully employed in heavy jet mode to set a force detent at the hands-off position. See Tab1 Items 26 & 27.

If the above settings are not made correctly then the heavy jet mode may not engage properly.
 

If the CL software detects a problem with the settings it will display an error message. Check the log files for further details of the issue.

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