Mass Subsystem

Mass Subsystem#

The mass subsystem in Aviary plays a straightforward but crucial role. We need to know a reasonable estimate for the mass of an aircraft to evaluate its performance. The mass subsystem provides this estimate.

Note

The mass subsystem in Aviary is similar to the “weights” or “weights and balances” in other tools or aircraft design.

Overview#

Aviary’s mass subsystem is designed to accommodate different methodologies, including FLOPS-based and GASP-based approaches, catering to diverse design needs and preferences. The subsystem is divided into multiple components, each handling specific aspects of mass calculation.

Aviary bookkeeps aircraft mass following the RP A-8 standard published by SAWE (Society of Allied Weight Engineers) where applicable. The SAWE mass breakdown and the individual masses computed by FLOPS and GASP are not an exact match, but the top-level summation categories are consistent with the standard. These top level categories (and a non-exhaustive list of their constituent components) are listed below. Bolded entries are groups that comprise of additional individual masses.

Empty Mass#

  • Structure Mass

    • Wing

    • Empennage

      • Vertical Tail

      • Horizontal Tail

      • Fins

    • Fuselage

    • Landing Gear

      • Main Gear

      • Nose Gear

    • Nacelles

  • Propulsion Mass

    • Engines

    • Thrust Reversers

    • Fuel Systems

    • Misc Propulsion

  • Systems and Equipment Mass

    • Controls

    • APU

    • Instruments

    • Hydraulics

    • Electrical

    • Avionics

    • Furnishings

    • Air Conditioning

    • Anti-Icing

  • External Subsystems

Operating Mass#

Empty Mass, plus:

  • Useful Load

    • Flight Crew

    • Cabin Crew

    • Passenger Service

    • Cargo Containers

    • Unusable Fuel

    • Engine Oil

Zero-Fuel Mass#

Operating Mass, plus:

  • Passengers

  • Cargo

Gross Mass#

Zero-Fuel Mass, plus:

  • Fuel

Using the Mass Subsystem#

The choice of which code’s methods for mass estimate to use is set using the variable settings:mass_method. This variable can be specified in the Aviary input file or can be manually set when using the Level 2 or 3 interface. To effectively use the mass subsystem in Aviary, users need to provide reasonable estimates for mass-related variables in their aircraft .csv file. Which variables are used depends on which mass estimation subsystem you’re using, such as aircraft:crew_and_payload:mass_per_passenger, aircraft:engine:additional_mass_fraction, etc.

Aviary allows for extensive customization and extensions within the mass subsystem. Users can develop alternative components and integrate them as subsystems with the existing platform.

External Mass#

Specifying the external mass method disables Aviary’s core mass group. This allows for external subsystems to completely replace all calculations.

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