Powerplant Strategies

The Powerplant properties group describes the aircraft's propulsion performance using one of several empirical models of aircraft engine systems.

Electric

The Electric strategy models an electric engine.

ParametersClosed

Field Description
Max Power The maximum power of the engine.
Propeller(s) The physical properties of the engine's propeller(s).

External Prop File

The External Prop File strategy uses propulsion data supplied by a .prop file.

ParametersClosed

The File Path field displays the currently selected file; click to browse to the file that you want to use. You can review the data in the file by selecting from a variety of data plots available from the drop-down menu at the upper right of the window. You can use the Throttle Tuple property to adjust the range of data that is displayed in the plots. Click anywhere in the profile to view information about the aircraft's performance in the Data at point properties group.

Click Create Copy... to save a copy of the file to your catalog file area, which is the default location that STK's Aviator capability opens when you select a .prop file to use.

The number of isolines displayed on the plot can be changed by moving the slider between the Less and More labels or by entering the value in the Level Factor field. The minimum and maximum values are 0.1 and 10, respectively.

Piston

The Piston strategy models a piston, or reciprocating, engine.

ParametersClosed

Field Description
Max Sea Level Static Power The maximum thrust that an engine can produce at a standstill. The maximum static power of the engine at sea level.
Critical Altitude The altitude at which the engine throttle reaches full open and the engine is still producing full rated power. The altitude at which the supercharger/turbocharger can no longer maintain sea-level manifold pressure, resulting in a decrease in power. This parameter models the effect of turbocharging.
Propeller(s) The physical properties of the engine's propeller(s).
Fuel Flow

Select the Calibrate Fuel Flow check box to edit the Fuel Flow at Max Power property. You can enter a new value for the property manually, or click Calibrate... to specify a flight condition and set a Fuel Flow at Altitude or Thrust Specific Fuel Consumption (TSFC) at Altitude. The value displayed in the Sea Level Fuel Flow field will be propagated to the Fuel Flow at Max Thrust field when you click OK.

Turbofan - High Bypass (Empirical Model)

The Turbofan - High Bypass strategy models a turbofan engine that produces significantly more fan thrust than jet thrust.

ParametersClosed

Field Description
Max Sea Level Static Thrust The maximum thrust that an engine can produce at a standstill. The maximum static thrust of the engine at sea level.
Design Point The highest corrected flow of an engine at inlet to the compression system. The Altitude and Mach The ratio of the aircraft's speed and the speed of sound at the aircraft's altitude, with local atmospheric conditions. Number that comprise the design point of the engine.
Fuel Flow Select the Calibrate Fuel Flow check box to edit the Fuel Flow at Max Thrust property. You can enter a new value for the property manually, or click Calibrate... to specify a flight condition and set a Fuel Flow at Altitude or Thrust Specific Fuel Consumption (TSFC) at Altitude. The value displayed in the Sea Level Fuel Flow field will be propagated to the Fuel Flow at Max Thrust field when you click OK.

Turbofan - Low Bypass (Empirical Model)

The Turbofan - Low Bypass strategy models a turbofan engine that produces significantly more jet thrust than fan thrust.

ParametersClosed

Field Description
Max Sea Level Static Thrust The maximum static thrust of the engine at sea level.
Design Point The Altitude and Mach Number that comprise the design point of the engine.
Fuel Flow Select the Calibrate Fuel Flow check box to edit the Fuel Flow at Max Thrust property. You can enter a new value for the property manually, or click Calibrate... to specify a flight condition and set a Fuel Flow at Altitude or Thrust Specific Fuel Consumption (TSFC) at Altitude. The value displayed in the Sea Level Fuel Flow field will be propagated to the Fuel Flow at Max Thrust field when you click OK.

Turbofan - Low Bypass Afterburning (Empirical Model)

The Turbofan - Low Bypass Afterburning strategy models a turbofan engine that produces significantly more jet thrust than fan thrust and has an afterburner A jet engine component that provides an increase in thrust by injecting additional fuel into the jet pipe, downstream of the turbine. An afterburner is usually employed in supersonic flight, certain takeoff scenarios, and in combat situations..

ParametersClosed

Field Description
Max Sea Level Static Thrust The maximum static thrust of the engine at sea level.
Design Point The Altitude and Mach Number that comprise the design point of the engine.
Fuel Flow Select the Calibrate Fuel Flow check box to edit the Fuel Flow at Max Thrust property. You can enter a new value for the property manually, or click Calibrate... to specify a flight condition and set a Fuel Flow at Altitude or Thrust Specific Fuel Consumption (TSFC) at Altitude. The value displayed in the Sea Level Fuel Flow field will be propagated to the Fuel Flow at Max Thrust field when you click OK.

Turbojet - Afterburning (Empirical Model)

The Turbojet - Afterburning strategy models a turbojet engine that has an afterburner.

ParametersClosed

Field Description
Max Sea Level Static Thrust The maximum static thrust of the engine at sea level.
Design Point The Altitude and Mach Number that comprise the design point of the engine.
Fuel Flow Select the Calibrate Fuel Flow check box to edit the Fuel Flow at Max Thrust property. You can enter a new value for the property manually, or click Calibrate... to specify a flight condition and set a Fuel Flow at Altitude or Thrust Specific Fuel Consumption (TSFC) at Altitude. The value displayed in the Sea Level Fuel Flow field will be propagated to the Fuel Flow at Max Thrust field when you click OK.

Turbojet (Empirical Model)

The Turbojet strategy models a turbojet engine.

ParametersClosed

Field Description
Max Sea Level Static Thrust The maximum static thrust of the engine at sea level.
Design Point The Altitude and Mach Number that comprise the design point of the engine.
Fuel Flow Select the Calibrate Fuel Flow check box to edit the Fuel Flow at Max Thrust property. You can enter a new value for the property manually, or click Calibrate... to specify a flight condition and set a Fuel Flow at Altitude or Thrust Specific Fuel Consumption (TSFC) at Altitude. The value displayed in the Sea Level Fuel Flow field will be propagated to the Fuel Flow at Max Thrust field when you click OK.

Turboprop (Empirical Model)

The Turboprop strategy models a turboprop engine.

ParametersClosed

Field Description
Max Sea Level Static Power The maximum static power of the engine at sea level.
Propeller(s) The physical properties of the engine's propeller(s).
Fuel Flow Select the Calibrate Fuel Flow check box to edit the Fuel Flow at Max Power property. You can enter a new value for the property manually, or click Calibrate....Clicking Calibrate... enables the user to specify a flight condition and set a Fuel Flow at Altitude or set a Thrust Specific Fuel Consumption (TSFC) at Altitude. The value displayed in the Sea Level Fuel Flow field will be propagated to the Fuel Flow at Max Thrust field when you click OK.

Thermodynamic Models

Aviator includes a set of high-end, complex, powerplant models that employ basic thermodynamics and several standard configurations of jet engine components. These models provide a set of tools that can be used to gain insight into the performance requirements of aircraft concepts that are still on the drawing board. They can help set reasonable expectations for technical managers to understand how different modes of propulsion operate across a potentially wide operating envelope.

By varying small sets of parameters, the performance of an engine in terms of thrust and fuel burn can be rapidly predicted across the flight envelope, then combined with a variety of aerodynamic models and modeled within STK, making use of Aviator procedures, guidance maneuvers, and other STK analysis features to understand how different propulsion systems enable certain tactics and capabilities, and to perform red versus blue analysis.

In addition, the models provide a framework, underlying the building blocks and functioning examples, for sophisticated users who want to incorporate their own or third party models of propulsion concepts and model those concepts inside of STK.

Individual Thermodynamic Powerplant ModelsClosed

Fuel Modeling

All of the thermodynamic powerplant models incorporate an extensible Fuel Model system that handles the thermodynamic properties of air / fuel mixtures. Aviator provides two kerosene air / fuel models - one based on AFPROP and the other on NASA CEA - and a hydrogen model based on CEA data. All of the models incorporate variable, specific, heat thermodynamics. The fuel models are all plugins, so you can employ your own models by providing additional plugins.

Sub/Super/Hypersonic Powerplant

A thermodynamic model that includes ramjet and scramjet performance modes. This model allows you to combine the operating concepts of turbines (for low speed regimes), ramjets (for supersonic regimes), and scramjet modes (for hypersonic regimes). This model doesn't assume any particular technical solution for integrating the different operating modes; it merely assumes that you have a design that can split airflow appropriately between the different operating modes. The framework enables you to control mode switchover via applicable pressure ratio and temperature considerations - accounting for the inherent limitations of compression and burner subsystems with and without turbomachinery.

Turbofan - Basic w/AB (Thermodynamic model)

A thermodynamic model based on a dual-spool, turbofan engine, in which the output stream of the fan and burner streams is mixed prior to passing through an afterburner - a standard engine configuration used on modern fighters and some bombers.

You can specify standard parameters, including the bypass ratio, to understand how advances in technology affect thrust and fuel burn across the flight envelope. The fundamental engineering concepts employed by this turbofan model are:

  • constant corrected mass flow through the bypass / core flow mixer
  • choked flow through the core stream burner

This is a conventional, fixed-geometry engine. The turbomachinery attributes are fixed and determined from the design point specification, so that the turbomachinery adjusts to different equilibrium points as the flight conditions and throttle settings change.

Turbojet - Basic w/AB (Thermodynamic model)

A thermodynamic model based on a dual-spool, turbojet engine with afterburning capability. This is a simple, technologically mature model. You can specify various maximum values for temperatures and pressure ratios along with component efficiencies to model the effect of those parameters on thrust and fuel burn. This model assumes that the flow through the burner is choked, meaning that it is at its maximum value for temperature and pressure as thermodynamic principles specify.