Study index
Understanding how the FMS balances time-related operating cost against fuel cost—and how that trade-off influences ECON speed, flight time, range, endurance and fuel remaining.
01 — STUDY INTRODUCTION
Cost Index expresses an economic priority
Cost Index is not simply a speed selector or a fuel-saving switch. It represents the relationship between time-related operating cost and fuel cost, allowing the flight-management system to calculate an economic speed strategy within the aircraft model and operational constraints.
A lower value generally places greater emphasis on fuel economy, while a higher value generally places greater emphasis on reducing flight time. The exact response remains aircraft-, engine-, software- and operator-dependent.
02 — STUDY INTRODUCTION
Faster does not automatically mean operationally better
Increasing ECON speed can reduce flight time but normally increases fuel flow and may reduce arrival fuel. Decreasing speed can reduce fuel burn per unit of time while extending exposure to winds, weather, airspace restrictions and other time-dependent factors.
The operational question is therefore not which Cost Index is universally best, but whether the planned strategy remains appropriate for the actual flight conditions and the operator's approved policy.
03 — STUDY INTRODUCTION
The complete edition develops the full decision framework
The protected 14-chapter NFA edition examines ECON speed, range, endurance, arrival-fuel prediction, step climbs, wind and temperature effects, ATC constraints, schedule pressure, re-dispatch considerations, crew monitoring and practical scenarios.
Cost Index selection and modification must remain within current regulations, operator fuel policy, the operational flight plan, approved aircraft documentation, MEL/CDL provisions, SOPs and applicable ATC requirements.
NFA PROFESSIONAL
Continue with the full professional edition.
This page is a public introduction, not the complete member study.
Open member editionProfessional plan in preparation. Full-study language availability is separate from this introduction.Educational material. Not a replacement for manufacturer manuals, approved operator procedures, MEL/CDL, operational approvals, AIP/NOTAM or regulatory requirements.