# flight_performance.cfg Additional Information<no value>
This page contains various notes related to some of the functionality derived from the [flight\_performance.cfg](../flight_performance.cfg/) sections and parameters.

 

 

### Notes On V1, Vr, V2 Computations

In the case of using v-tables as part of the takeoff calculations, the {{< glossterm >}}v1{{< /glossterm >}} speed of the takeoff decision go / no go, the {{< glossterm >}}vr{{< /glossterm >}} speed of nose gear lift, and the {{< glossterm >}}v2{{< /glossterm >}} speed of the aircraft liftoff, are all calculated using the following method:

-   Determine {{< glossterm >}}v1{{< /glossterm >}}, {{< glossterm >}}vr{{< /glossterm >}}, and {{< glossterm >}}v2{{< /glossterm >}} from the Takeoff Speeds tables with brake release weight. That's these tables in the CFG file: `V1_table_by_flaps_and_weight`, `Vr_table_by_flaps_and_weight`, `V2_table_by_flaps_and_weight`
-   Adjust {{< glossterm >}}v1{{< /glossterm >}}, {{< glossterm >}}vr{{< /glossterm >}}, and {{< glossterm >}}v2{{< /glossterm >}} for temperature and pressure altitude from the {{< glossterm >}}v1{{< /glossterm >}}, {{< glossterm >}}vr{{< /glossterm >}}, {{< glossterm >}}v2{{< /glossterm >}} Adjustments tables. That's these tables in the CFG file: `V1_adjustments_table_by_altitude_and_OAT`, `Vr_adjustments_table_by_altitude_and_OAT`, `V2_adjustments_table_by_altitude_and_OAT`
-   Adjust {{< glossterm >}}v1{{< /glossterm >}} for wind and slope from the Slope and Wind {{< glossterm >}}v1{{< /glossterm >}} Adjustments tables. That's these tables in the CFG file: `V1_adjustments_table_by_slope_and_weight`, `V1_adjustments_table_by_wind_and_weight`
-   Additionally the following constraints will be applied to determine the values:
    -   \(V1 = MIN(V1, Vr)\)
    -   \(V2 = MAX(Vr, V2)\)

 

 

### Notes On Takeoff Distances

When it comes to calculating the *actual* takeoff distances (ie: the distance that an aircraft actually travels during takeoff) using the v-tables, the following friction coefficient of a freely rolling aircraft on a surface is used:

 

{{< table-wrapper >}}

| Runway condition | Friction coefficient, \[unitless\] |
|------------------|------------------------------------|
| Dry              | 0.03                               |
| Wet              | 0.05                               |

{{< /table-wrapper >}}


 

Once the actual takeoff distances have been determined (whether based on distance tables or V-tables, or a combination of them), the following limitation will be applied:

-   \(\textrm{Total distance} = MAX(\textrm{Ground roll distance}, \textrm{Total distance})\)

 

Once the actual takeoff *ground roll distance* and takeoff *total distance* have been determined (based on the aircraft capabilities), safety margins are applied to them for display in the {{< glossterm >}}efb{{< /glossterm >}} as **required** takeoff distances:

-   \(\textrm{required distance} = \textrm{actual distance} + \textrm{safety margin}\)

 

There are several safety margins based on the following parameters:

 

-   **Wind**
    -   Decrease ground roll distance and total distance by 10% for each 11 {{< glossterm >}}knots{{< /glossterm >}} headwind
    -   Increase ground roll distance and total distance by 10% for each 2 {{< glossterm >}}knots{{< /glossterm >}} tailwind

 

-   **Runway type**

    On a grass runway, increase:

    -   ground roll by 15%
    -   total distance by 10%

 

-   **Flaps state**

    If an aircraft has flaps and they are fully retracted or fully extended then increase ground roll distance and total distance by 20%.

 

-   **Maximum takeoff weight** ({{< glossterm >}}mtow{{< /glossterm >}})
    -   Increase ground roll distance and total distance by 15% for aircraft with {{< glossterm >}}mtow{{< /glossterm >}} of 2000kg or less;
    -   Increase ground roll distance and total distance by 25% for aircraft with {{< glossterm >}}mtow{{< /glossterm >}} of 3500kg or greater;
    -   For aircraft with {{< glossterm >}}mtow{{< /glossterm >}} of 2000kg to 3500kg, the coefficient of increase in the ground roll distance and the total distance is calculated by linear interpolation in the range from 15% to 25%.

 

 

### Notes On Landing Distances

Once the *actual* landing **ground roll distance** and landing **total distance** have been determined (based on the aircraft capabilities), safety margins are applied to them for display in the EFB as **required** landing distances:

-   \(\textrm{required distance} = \textrm{actual distance} + \textrm{safety margin}\)

 

There are several safety margins based on the following parameters:

 

-   **Wind**

    -   Decrease ground roll distance and total distance by 10% for each 11 knots headwind
    -   Increase ground roll distance and total distance by 10% for each 2 knots tailwind

 

-   **Runway type**

    On a grass runway, increase:

    -   ground roll by 40%
    -   total distance by 30%

 

-   **Flaps state**

    If an aircraft has flaps but they are not fully extended, then increase ground roll distance and total distance by 40% if flaps are fully retracted, or proportionally for intermediate flap positions.

 

-   **Engine type**

    Increase ground roll distance and total distance depending on engine type and runway condition by:

     

{{< table-wrapper >}}

    | Engine type | Dry runway | Wet runway |
    |-------------|------------|------------|
    | Piston      | +25%       | +44%       |
    | Turboprop   | +43%       | +64%       |
    | Turbine     | +67%       | +92%       |

{{< /table-wrapper >}}