# Tail Geometry<no value>

{{< callout context="note" title="NOTE" icon="outline/bulb" >}}

This page is currently WIP.

{{< /callout >}}

 

### The Horizontal Tail

To adjust the horizontal tail's **vertical** and **longitudinal** position you can change the **Pos Lon** and **Pos Vert** (in {{< glossterm >}}ft{{< /glossterm >}}) inputs in the SimObject Editor, or edit the [`htail_pos_lon`](../../../../content-configuration/cfg-files/flight_model.cfg/#htail_pos_lon) and [`htail_pos_vert`](../../../../content-configuration/cfg-files/flight_model.cfg/#htail_pos_vert) parameters in the `flight_model.cfg`. You'll also want to adjust the horizontal tail **Thickness Ratio**, which is the [`htail_thickness_ratio`](../../../../content-configuration/cfg-files/flight_model.cfg/#htail_thickness_ratio) parameter in the CFG file.

{{< image-center
    src="images/7_Samples_Tutorials/Tutorials/Define_Flight_Model/geometry/htail/geometry_12_posthick.png"
    alt="The H-Tail Pos And Thickness Parameters in The SimObject Editor" >}}

The calculation for local thickness is as follows:

$$\textrm{Local thickness} = \textrm{local_chord(x)} \times \textrm{htail_thickness_ratio}, x = \textrm{lateral_coord}$$

 

Next you'll want to adjust the **Area**, the **{{< glossterm >}}sweep{{< /glossterm >}}**, and the **Span** of the horizontal tail based off of the data you have or using a visual alignment to the model. These parameters are [`htail_area`](../../../../content-configuration/cfg-files/flight_model.cfg/#htail_area), [`htail_span`](../../../../content-configuration/cfg-files/flight_model.cfg/#htail_span), and [`htail_sweep`](../../../../content-configuration/cfg-files/flight_model.cfg/#htail_sweep) in the CFG file. Note that if the aircraft only has an elevator and no horizontal stabilizer, the horizontal tale area should be set to zero.

{{< image-center
    src="images/7_Samples_Tutorials/Tutorials/Define_Flight_Model/geometry/htail/geometry_13_sweep.png"
    alt="The H-Tail Area, Span And Sweep Parameters in The SimObject Editor" >}}

 

You'll want to leave the **horizontal tail Incidence** ([`htail_incidence`](../../../../content-configuration/cfg-files/flight_model.cfg/#htail_incidence) in the `flight_model.cfg`) at zero for the moment, this value will be used to set the default trim of the aircraft later. However you should set the **Elevator Area** value in the *Controls / Properties* section of the Geometry panel, which relates to the [`elevator_area`](../../../../content-configuration/cfg-files/flight_model.cfg/#elevator_area) parameter in the CFG file.

{{< image-center
    src="images/7_Samples_Tutorials/Tutorials/Define_Flight_Model/geometry/htail/geometry_14_elevator.png"
    alt="The Elevator Parameter in The SimObject Editor" >}}

 

If you don't have these exact values available, you can adjust them visually using the debug overlay such that the surface sensor points cover the area correctly. When finished, you should see the surface sensors aligned to the horizontal tail:

{{< image-center
    src="images/7_Samples_Tutorials/Tutorials/Define_Flight_Model/geometry/htail/geometry_11_htail.png"
    alt="The H-Tail Surface Sensors Correctly Positioned" >}}

 

 

### The Vertical Tail

We'll now adjust the **Vertical Tail** the same as we did for the horizontal, starting with the vertical and longitudinal position using the **Pos Vert** and **Pos Lon** inputs, and also the **Thickness Ratio**. These correspond to the [`vtail_pos_lon`](../../../../content-configuration/cfg-files/flight_model.cfg/#vtail_pos_lon), [`vtail_pos_vert`](../../../../content-configuration/cfg-files/flight_model.cfg/#vtail_pos_vert), and [`vtail_thickness_ratio`](../../../../content-configuration/cfg-files/flight_model.cfg/#vtail_thickness_ratio) in the `flight_model.cfg`.

{{< image-center
    src="images/7_Samples_Tutorials/Tutorials/Define_Flight_Model/geometry/vtail/geometry_16_posthick.png"
    alt="The V-Tail Pos And Thickness Parameters in The SimObject Editor" >}}

The calculation for local thickness is as follows:

$$\textrm{Local thickness} = \textrm{local_chord(x)} \times \textrm{vtail_thickness_ratio}, x = \textrm{lateral_coord}$$

 

Next you'll want to adjust the **Area**, the **{{< glossterm >}}sweep{{< /glossterm >}}**, and the **Span** of the vertical tail based off of the data you have or using a visual alignment to the model. These parameters are [`vtail_area`](../../../../content-configuration/cfg-files/flight_model.cfg/#vtail_area), [`vtail_span`](../../../../content-configuration/cfg-files/flight_model.cfg/#vtail_span), and [`vtail_sweep`](../../../../content-configuration/cfg-files/flight_model.cfg/#vtail_sweep) in the CFG file.

{{< image-center
    src="images/7_Samples_Tutorials/Tutorials/Define_Flight_Model/geometry/vtail/geometry_17_sweep.png"
    alt="The H-Tail Area, Span And Sweep Parameters in The SimObject Editor" >}}

 

Finally you should set the **Rudder Area** value in the Geometry section, which relates to the [`rudder_area`](../../../../content-configuration/cfg-files/flight_model.cfg/#rudder_area) parameter in the CFG file.

{{< image-center
    src="images/7_Samples_Tutorials/Tutorials/Define_Flight_Model/geometry/vtail/geometry_18_rudder.png"
    alt="The Elevator Parameter in The SimObject Editor" >}}

 

After these steps, you should see the surface sensors aligned to the vertical tail, with a second row aligned about halfway along the tail width:

{{< image-center
    src="images/7_Samples_Tutorials/Tutorials/Define_Flight_Model/geometry/vtail/geometry_15_vtail.png"
    alt="The V-Tail Surface Sensors Correctly Positioned" >}}

 

 

### Rudder

The rudder now needs to be setup, so we'll start by defining the **Rudder Area** ({{< glossterm >}}sqft{{< /glossterm >}}) and the **Rudder Limit** in the Geometry section, which are the [`rudder_area`](../../../../content-configuration/cfg-files/flight_model.cfg/#rudder_area) and [`rudder_limit`](../../../../content-configuration/cfg-files/flight_model.cfg/#rudder_limit) parameters the `flight_model.cfg`.

{{< image-center
    src="images/7_Samples_Tutorials/Tutorials/Define_Flight_Model/geometry/rudder/geometry_24_rudderarea.png"
    alt="The Rudder Area And Limit Parameters in The SimObject Editor" >}}

 

As with the other parameters, if have this exact data then use it. If you don't have the data, you can set a value for the rudder area that is in the same order of magnitude as the aileron and elevator surface areas, and for the rudder limit, this is usually between 15° and 30°. The angle needs to be important enough to achieve the maximum possible crosswind landing and {{< glossterm >}}de_crab{{< /glossterm >}} the aircraft.

 

Similarly to the ailerons, you also need to define the maximum deflection ratio based on the speed of the aircraft by setting up the table that defines the ratio of rudder control depending on the amount of dynamic air pressure. This is done from the **Elasticity Tables** section of the SimObject Editor, or by editing the [`rudder_elasticity_table`](../../../../content-configuration/cfg-files/flight_model.cfg/#rudder_elasticity_table) parameter in the CFG file.

{{< image-center
    src="images/7_Samples_Tutorials/Tutorials/Define_Flight_Model/geometry/rudder/geometry_24_ruddertable.png"
    alt="The Rudder Elasticity Table in The SimObject Editor" >}}

 

At this stage, you should perform an approach test:

-   put the plane at low speed
-   go full rudder
-   check the skid angle of the airplane

Most planes are able to skid during a stable cross control by about 10° to 20°:

{{< image-center
    src="images/7_Samples_Tutorials/Tutorials/Define_Flight_Model/geometry/rudder/geometry_25_skid.png"
    alt="Checking The Skid In The SimObject Editor Debugger" >}}

 

In order to adjust the rudder authority, without changing the rudder surface or maximum deflection angle, which should be based on real data, two parameters are available in the **Flight Tuning** section of the SimObject Editor, the **Rudder Effectiveness** and the **Rudder Max Angular Scalar**. In the `flight_model.cfg` file these are under the `[FLIGHT_TUNING]` header, as [`rudder_effectiveness`](../../../../content-configuration/cfg-files/flight_model.cfg/#rudder_effectiveness), and [`rudder_maxangle_scalar`](../../../../content-configuration/cfg-files/flight_model.cfg/#rudder_maxangle_scalar).

![The Rudder Effectiveness And Max Angle Scalar Parameters in The SimObject Editor](images/7_Samples_Tutorials/Tutorials/Define_Flight_Model/geometry/rudder/geometry_24_ruddereffect.png)Also, you may want to go back to adjusting your aileron authority at this stage as most aircraft will have enough aileron control to counter a full rudder deflection and maintain a stable cross controlled flight.

 

 

### Elevator

The **elevator** is the last thing that we now need to setup, and we'll start by defining the **Elevator Area** ({{< glossterm >}}sqft{{< /glossterm >}}) and the **Elevator Limit**, which are the [`elevator_area`](../../../../content-configuration/cfg-files/flight_model.cfg/#elevator_area), [`elevator_up_limit`](../../../../content-configuration/cfg-files/flight_model.cfg/#elevator_up_limit), and [`elevator_down_limit`](../../../../content-configuration/cfg-files/flight_model.cfg/#elevator_down_limit) parameters the `flight_model.cfg`.

{{< image-center
    src="images/7_Samples_Tutorials/Tutorials/Define_Flight_Model/geometry/elevator/geometry_26_elevatorarea.png"
    alt="The Elevator Area And Limit Parameters in The SimObject Editor" >}}

 

As with the other parameters, if have this exact data then use it. If you don't have the data, you can set a value for the elevator area that is in the same order of magnitude as the aileron and rudder surface areas, and for the elevator limit, this is usually between 20° and 30°. The up limit angle needs to be important enough to allow flaring the aircraft upon landing.

 

Similarly to the ailerons and the rudder, you also need to define the ratio of elevator control depending on the amount of dynamic air pressure. This is done from the **Elasticity Tables** section of the SimObject Editor, or by editing the [`elevator_elasticity_table`](../../../../content-configuration/cfg-files/flight_model.cfg/#elevator_elasticity_table) parameter in the CFG file.

{{< image-center
    src="images/7_Samples_Tutorials/Tutorials/Define_Flight_Model/geometry/elevator/geometry_26_elevatortable.png"
    alt="The Elevator Elasticity Table in The SimObject Editor" >}}

Finally, in order to adjust the elevator authority, without changing the elevator surface or maximum deflection angle - which should be based on real data - two parameters are available in the Flight Tuning panel of the SimObject Editor, the **Elevator Effectiveness** and the **Elevator Max Angular Scalar**. These are the parameters [`elevator_effectiveness`](../../../../content-configuration/cfg-files/flight_model.cfg/#elevator_effectiveness) and [`elevator_maxangle_scalar`](../../../../content-configuration/cfg-files/flight_model.cfg/#elevator_maxangle_scalar) parameters in the `flight_model.cfg`.

{{< image-center
    src="images/7_Samples_Tutorials/Tutorials/Define_Flight_Model/geometry/elevator/geometry_26_elevatoreffect.png"
    alt="The Elevator Effectiveness And Max Angle Scalar Parameters In The SimObject Editor" >}}

 

At this stage, you should perform a stall test:

-   Put the plane at lower speed
-   power off
-   try to fly steady without descending

You will need to increase your elevator position closer and closer to the upper limit. When the wing stalls, you will see the lift force vectors on the surfaces change color. Yellow is getting close to stall, red is stalling, blue is a fully stalled surface:  

{{< image-center
    src="images/7_Samples_Tutorials/Tutorials/Define_Flight_Model/geometry/elevator/geometry_27_stall.png"
    alt="Stalling Forces Shown In The AIrcraft Editor Debug Visualisation" >}}

 

Stalling is computed individually for each surface in the new aerodynamics model of Microsoft Flight Simulator 2024. Most aircraft will allow getting very close to the stall speed limit when the elevator is maintained at the maximum upwards deflection. Some planes will never drop and start descending and others will have a sharp drop. Increasing or decreasing the maximum deflection angle of the elevator, or increasing or decreasing the effect of the elevator deflection, can allow you to achieve a higher or lower maximum angle of attack and therefore change the type of stall of the aircraft.