flight_performance.cfg - Additional Information
This page contains various notes related to some of the functionality derived from the 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 V1 speed of the takeoff decision go / no go, the Vr speed of nose gear lift, and the V2 speed of the aircraft liftoff, are all calculated using the following method:
- Determine V1, Vr, and V2 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 V1, Vr, and V2 for temperature and pressure altitude from the V1, Vr, V2 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 V1 for wind and slope from the Slope and Wind V1 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:
| Runway condition | Friction coefficient, [unitless] |
|---|---|
| Dry | 0.03 |
| Wet | 0.05 |
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 EFB as required takeoff distances:
- \(\textrm{required distance} = \textrm{actual distance} + \textrm{safety margin}\)
There are several safety margins based on the following parameters:
- Wind
- 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 (MTOW)
- Increase ground roll distance and total distance by 15% for aircraft with MTOW of 2000kg or less;
- Increase ground roll distance and total distance by 25% for aircraft with MTOW of 3500kg or greater;
- For aircraft with MTOW 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:
Engine type Dry runway Wet runway Piston +25% +44% Turboprop +43% +64% Turbine +67% +92%
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