Mission file

General description

A mission file describes precisely one or several missions that could be computed by the performance model fastoad.performances.mission of FAST-OAD.

The file format of mission files is the YAML format. A quick tutorial for YAML (among many ones) is available here.

The mission definition relies on 4 concepts that are, from lowest level to the highest one: segments, phases, routes and missions. They are summarized in this table:

Mission elements

Type	Parts	Description
segment	N/A	The basic bricks that are provided by FAST-OAD. They are described in this specific page.
phase	segment(s) and/or phase(s)	A free assembly of one or more segments and/or other phases.
route	zero or more phase(s) one cruise segment zero or more phase(s)	A route is a climb/cruise/descent sequence with a fixed range. The range is achieved by adjusting the distance covered during the cruise part.
mission	routes and/or phases and/or segments	A mission is what is computed by fastoad.performances.mission. Generally, it begins when engine starts and ends when engine stops.

Important

Starting with version 1.4.0 of FAST-OAD, any mission has to use a variable for mass input. This variable can be defined using the start segment, if it provides the mass at mission start (typically a ramp-up weight), or using the mass_input segment otherwise (typically a takeoff weight, achieved after the taxi-out).

In the case no variable is defined for input mass, FAST-OAD will automatically add, at the beginning of the mission, a taxi-out and a very simple takeoff phase (transition segment) with a mass_input segment. In that case, the input mass is given by the data:mission:<mission_name>:TOW variable, which represents the aircraft mass just after takeoff.

This addition of taxi-out, takeoff and mass input allows to keep compatibility with mission definitions for FAST-OAD versions earlier than 1.4.

(Please note that takeoff weight should be actually considered as the mass just before takeoff, but this way of doing is kept for maximum backward-compatibility)

File sections

The organization of a mission definition file is organized in sections according to above-defined concepts.

Phase definition section

This section, identified by the phases keyword, defines flight phases. A flight phase is defined as an assembly of one or more flight segment(s).

Basically, a phase has a name, and a parts attribute that contains a list of segment definitions.

Nevertheless, it is also possible to set, at phase level, the parameters that are common to several segments of the phase.

The phase section only defines flight phases, but not their usage, that is defined in route and mission sections. Therefore, the definition order of flight phases has no importance.

Note

Some parameters may be more conveniently set at an upper level than segment-level. See section Factorizing parameters to see how.

Example:

phases:
  initial_climb:                               # Phase name
    parts:                                         # Definition of segment list
      - segment: altitude_change                   # 1st segment (climb)
        polar: data:aerodynamics:aircraft:takeoff
        thrust_rate: 1.0
        target:
          altitude:
            value: 400.
            unit: ft
          equivalent_airspeed: constant
      - segment: speed_change                      # 2nd segment (acceleration)
        polar: data:aerodynamics:aircraft:takeoff
        thrust_rate: 1.0
        target:
          equivalent_airspeed:
            value: 250
            unit: kn
      - segment: altitude_change                   # 3rd segment (climb)
        polar: data:aerodynamics:aircraft:takeoff
        thrust_rate: 0.95
        target:
          altitude:
            value: 1500.
            unit: ft
          equivalent_airspeed: constant
    climb:                                    # Phase name
      ...                                          # Definition of the phase...

Specific takeoff phase definition section

The takeoff and associated manoeuvres may be simulated by assembling the specific segments. An exemple of takeoff phase definition, as well as start-stop phase are given here:

Example:

takeoff:
    engine_setting: takeoff
    polar:
      CL: data:aerodynamics:aircraft:takeoff:CL
      CD: data:aerodynamics:aircraft:takeoff:CD
      ground_effect: None # Ground effect model selection
      CL0_clean: data:aerodynamics:aircraft:takeoff:CL0_clean
      CL_alpha: data:aerodynamics:aircraft:takeoff:CL_alpha
      CL_high_lift: data:aerodynamics:high_lift_devices:takeoff:CL
    thrust_rate: 1.0
    isa_offset: data:mission:operational:ISA_offset
    parts:
      - segment: ground_speed_change
        target:
          equivalent_airspeed:
            value: data:mission:operational:takeoff:Vr
      - segment: rotation
        target:
          delta_altitude:
            value: 35
            unit: ft
      - segment: end_of_takeoff
        time_step: 0.05
        target:
          delta_altitude:
            value: 35
            unit: ft
start_stop: # start - stop manoeuvre with only brakes on
    engine_setting: takeoff
    polar:
      CL: data:aerodynamics:aircraft:takeoff:CL
      CD: data:aerodynamics:aircraft:takeoff:CD
      ground_effect: Raymer # Ground effect model selection
      CL0_clean: data:aerodynamics:aircraft:takeoff:CL0_clean
      CL_alpha: data:aerodynamics:aircraft:takeoff:CL_alpha
      CL_high_lift: data:aerodynamics:high_lift_devices:takeoff:CL
    thrust_rate: 1.0
    isa_offset: data:mission:operational:ISA_offset
    parts:
      - segment: ground_speed_change
        wheels_friction: 0.03
        time_step: 0.05
        target:
          equivalent_airspeed:
            value: data:mission:operational:takeoff:V1
      - segment: ground_speed_change
        engine_setting: idle
        thrust_rate: 0.07
        wheels_friction: 0.5
        time_step: 0.05
        target:
          true_airspeed:
            value: 0
            unit: m/s

Route definition section

This section, identified by the routes keyword, defines flight routes. A flight route is defined as climb/cruise/descent sequence with a fixed range. The range is achieved by adjusting the distance covered during the cruise part. Climb and descent phases are computed normally.

A route is identified by its name and has 4 attributes:

• range: the distance to be covered by the whole route

• climb_parts: a list of items like phase : <phase_name>

• cruise_part: a segment definition, except that it does not need any target distance.

• descent_parts: a list of items like phase : <phase_name>

Example:

routes:
  main_route:
    range:
      value: 3000.
      unit: NM
    climb_parts:
      - phase: initial_climb
      - phase: climb
    cruise_part:
      segment: cruise
      engine_setting: cruise
      polar: data:aerodynamics:aircraft:cruise
      target:
        altitude: optimal_flight_level
      maximum_flight_level: 340
    descent_parts:
      - phase: descent
  diversion:
    range: distance
    climb_parts:
      - phase: diversion_climb
    cruise_part:
      segment: breguet
      engine_setting: cruise
      polar: data:aerodynamics:aircraft:cruise
    descent_parts:
      - phase: descent

Mission definition section

This is the main section. It allows to define one or several missions, that will be computed by the mission module.

A mission is identified by its name and has 3 attributes:

• parts: list of the phase and/or route names that compose the mission, with optionally a last item that is the reserve (see below).

• use_all_block_fuel: if True, the range of the main route of the mission will be adjusted so that all block fuel (provided as input data:mission:<mission_name>:block_fuel) will be consumed for the mission, excepted the reserve, if defined. The provided range for first route is overridden but used as a first guess to initiate the iterative process.

The mission name is used when configuring the mission module in the FAST-OAD configuration file. If there is only one mission defined in the file, naming it in the configuration file is optional.

Note

About reserve

The reserve keyword is typically designed to define fuel reserve as stated in EU-OPS 1.255.

It defines the amount of fuel that is expected to be still in tanks once the mission is complete. It takes as reference one of the route that composes the mission (ref attribute). The reserve is defined as the amount of fuel consumed during the referenced route, multiplied by the coefficient provided as the multiplier attribute.

Example:

missions:
  sizing:
    parts:
      - phase: taxi_out
      - phase: takeoff
      - route: main_route
      - route: diversion
      - phase: holding
      - phase: landing
      - phase: taxi_in
      - reserve:
          ref: main_route
          multiplier: 0.03
  operational:
    parts:
      - phase: taxi_out
      - phase: takeoff
      - route: main_route
      - phase: landing
      - phase: taxi_in
  fuel_driven:
    parts:
      - phase: taxi_out
      - phase: takeoff
      - route: main_route
      - phase: landing
      - phase: taxi_in
    use_all_block_fuel: true

Factorizing parameters

Some parameters may be common to several segments and have same value across all of them. In such case, it is possible to define them at higher level (i.e. phase, route or mission) to avoid repeating them.

For example, to specify a temperature increment at mission level, the mission section could be:

missions:
  operational:
    isa_offset: 15.0            # It will apply to the whole mission
    parts:
      - route: main_route
      - phase: landing
      - phase: taxi_in

A high-level parameter definition will be overloaded by a lower-level definition, as illustrated in this example of phase definition:

phases:
  initial_climb:                               # Phase name
    engine_setting: takeoff                        # ---------------
    polar: data:aerodynamics:aircraft:takeoff      #   Common segment
    thrust_rate: 1.0                               #   parameters
    time_step: 0.2                                 # ---------------

    parts:                                         # Definition of segment list
      - segment: altitude_change                     # 1st segment (climb)
        target:
          altitude:
            value: 400.
            unit: ft
          equivalent_airspeed: constant
      - segment: speed_change                        # 2nd segment (acceleration)
        target:
          equivalent_airspeed:
            value: 250
            unit: kn
      - segment: altitude_change                     # 3rd segment (climb)
        thrust_rate: 0.95        # --> PHASE THRUST RATE VALUE IS OVERWRITTEN
        target:
          altitude:
            value: 1500.
            unit: ft
          equivalent_airspeed: constant