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Run npx skillmds@latest add ashfordeou/specific-range in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

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Is Specific Range free to use?

Yes. Installing skills from SkillMD is free. This skill is licensed under Apache-2.

Who published Specific Range?

ashfordeOU (@ashfordeou) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Specific Range by ashfordeou — Agent Skill

Name: Specific Range
Author: ashfordeOU

Specific Range

Use when you must compute the specific air range of an aircraft in cruise: divide the true airspeed by the fuel flow to produce the specific air range in meters per kilogram, derive the fuel flow from the thrust specific fuel consumption and the required thrust, estimate the instantaneous range from speed, thrust specific fuel consumption, weight, and lift to drag ratio, and convert a block distance into the fuel burn for the sector. Produces the specific air range, fuel flow, and fuel burn that gate the cruise fuel economy assessment. Trigger: specific air range, fuel flow, instantaneous range, meters per kilogram, sector fuel burn.

ashfordeOU c99c929 3 files · 9.6 KB Updated Sep 17, 2026

File contents

Specific Range (flight-mechanics/performance/specific-range)

Use when the task is cruise fuel economy from the specific air range: true airspeed and fuel flow inputs, plus the fuel flow from thrust and thrust specific fuel consumption, the instantaneous range from the aerodynamic efficiency, and the sector fuel burn from a block distance.

Domain quick reference

The specific air range SAR is the distance flown per unit fuel mass: SAR = V / mdot, with true airspeed V in m/s and fuel flow mdot in kg/s, so SAR is in meters per kilogram.
Fuel flow follows from the thrust specific fuel consumption and the required thrust: mdot = TSFC * T, with TSFC in kg/(N s) and thrust T in newtons.
In steady cruise thrust equals drag, and the instantaneous range from aerodynamic inputs is SAR = V * (L/D) / (TSFC * W), with the weight W in newtons and L/D the lift to drag ratio.
The fuel burn for a block distance d is m_fuel = d / SAR, in kilograms for d in meters.
Cruise fuel economy sits in the FAR-25 / CS-25 transport performance context for cruise fuel planning.

Workflow

Collect the true airspeed and the fuel flow for the cruise point.
Compute the specific air range with specific_air_range.
Derive the fuel flow from thrust and TSFC with fuel_flow_from_thrust.
Estimate the instantaneous range from speed, TSFC, weight, and lift to drag with instantaneous_range.
Convert the block distance into fuel burn with sector_fuel_burn.

Pitfalls

Mixing TSFC units between kg/(N s) and 1/h; the fuel flow relation needs TSFC per newton second.
Using the aircraft mass in kilograms where the equations take the weight in newtons; multiply the mass by g0 = 9.80665.
Dividing by a zero or negative fuel flow; specific_air_range raises ValueError on non-positive speed or fuel flow.
Treating the specific air range as a total mission range; SAR is a point metric and must be integrated for a full leg.

Behavior contract (gate 3)

The specific air range, fuel flow, and fuel burn logic is exercised by the gate 3 contract test: scripts/test_specific_range.py against scripts/specific_range_logic.py (stdlib unittest, offline). Run: python3 scripts/test_specific_range.py

Compliance

Standards referenced, not reproduced: FAR-25 is US government work (public domain) and CS-25 is a free EASA download; the specific air range method is common cruise fuel economy methodology, summary-only per standards-map.yaml.
compliance: STANDARDS-REF, gated: false.

---name: specific-rangedescription: Use when you must compute the specific air range of an aircraft in cruise: divide the true airspeed by the fuel flow to produce the specific air range in meters per kilogram, derive the fuel flow from the thrust specific fuel consumption and the required thrust, estimate the instantaneous range from speed, thrust specific fuel consumption, weight, and lift to drag ratio, and convert a block distance into the fuel burn for the sector. Produces the specific air range, fuel flow, and fuel burn that gate the cruise fuel economy assessment. Trigger: specific air range, fuel flow, instantaneous range, meters per kilogram, sector fuel burn.license: Apache-2.0---# Specific Range (flight-mechanics/performance/specific-range)Use when the task is cruise fuel economy from the specific airrange: true airspeed and fuel flow inputs, plus the fuel flowfrom thrust and thrust specific fuel consumption, theinstantaneous range from the aerodynamic efficiency, and thesector fuel burn from a block distance.## Domain quick reference- The specific air range SAR is the distance flown per unit fuel mass: SAR = V / mdot, with true airspeed V in m/s and fuel flow mdot in kg/s, so SAR is in meters per kilogram.- Fuel flow follows from the thrust specific fuel consumption and the required thrust: mdot = TSFC * T, with TSFC in kg/(N s) and thrust T in newtons.- In steady cruise thrust equals drag, and the instantaneous range from aerodynamic inputs is SAR = V * (L/D) / (TSFC * W), with the weight W in newtons and L/D the lift to drag ratio.- The fuel burn for a block distance d is m_fuel = d / SAR, in kilograms for d in meters.- Cruise fuel economy sits in the FAR-25 / CS-25 transport performance context for cruise fuel planning.## Workflow1. Collect the true airspeed and the fuel flow for the cruise point.2. Compute the specific air range with specific_air_range.3. Derive the fuel flow from thrust and TSFC with fuel_flow_from_thrust.4. Estimate the instantaneous range from speed, TSFC, weight, and lift to drag with instantaneous_range.5. Convert the block distance into fuel burn with sector_fuel_burn.## Pitfalls- Mixing TSFC units between kg/(N s) and 1/h; the fuel flow relation needs TSFC per newton second.- Using the aircraft mass in kilograms where the equations take the weight in newtons; multiply the mass by g0 = 9.80665.- Dividing by a zero or negative fuel flow; specific_air_range raises ValueError on non-positive speed or fuel flow.- Treating the specific air range as a total mission range; SAR is a point metric and must be integrated for a full leg.## Behavior contract (gate 3)The specific air range, fuel flow, and fuel burn logic isexercised by the gate 3 contract test: scripts/test_specific_range.pyagainst scripts/specific_range_logic.py (stdlib unittest,offline). Run: python3 scripts/test_specific_range.py## Compliance- Standards referenced, not reproduced: FAR-25 is US government work (public domain) and CS-25 is a free EASA download; the specific air range method is common cruise fuel economy methodology, summary-only per standards-map.yaml.- compliance: STANDARDS-REF, gated: false.

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