Keeping Aircraft Powered: Electrical Load Analysis (ELA)

Electrical Load Analysis (ELA) is a critical part of aircraft design, certification, and continuing airworthiness. It involves calculating all electrical power demands placed on the aircraft under various operating conditions (normal, abnormal, and emergency) by listing every electrically powered item or circuit and its corresponding power requirement. The demand for each item may vary depending on the aircraft’s phase of operation, such as takeoff, cruise, or landing.

Adding or removing equipment—whether essential or non-essential—requires the same rigorous analysis as weight and balance calculations, ensuring the electrical system’s integrity is maintained. The ELA is a living document and should stay with the aircraft, constantly updated to reflect its current configuration.

Electrical Load Initial Airworthiness

Under CS 25.1351, the electrical system must supply all essential loads through a combination of power sources. The generating system, including buses, cables, and protective devices, must:

• Operate correctly independently and in combination.

• Ensure failure of one source doesn’t compromise others or essential loads.

• Maintain voltage and frequency within equipment limits.

• Prevent system transients from causing inoperative essential loads or fire hazards.

• Allow crew-accessible disconnection when necessary.

• Provide indicators for voltage and current essential for safe operation.

External power use must include safeguards to prevent damage, and alternate high-integrity independent sources are required unless total loss is extremely improbable.

The ELA produced for type certification reflects the aircraft’s electrical load status at delivery and serves as the reference point for all future updates.

Electrical Load Continuing Airworthiness

Modifications to the ELA, such as changes in circuit breaker loads, bus connections, power factor, or duty cycles, constitute changes to the type certificate and require approval under Part 21 regulations.

Manufacturers typically provide a difference sheet or ELA supplement. This documentation may take the form of an ELA datasheet, Service Bulletin (SB), or Supplemental Type Certificate (STC) load analysis, which serves as a reference for updating records and keeping the analysis aligned with the approved type design.

Instructions for Continued Airworthiness (ICA) must include:

• Electrical generating capacity of normal and emergency sources.

• Load capacity and actual loading of each bus.

• Procedures for updating ELA data after modifications.

Operators are ultimately responsible for ensuring that every modification influencing the electrical distribution system is properly analyzed and documented, so that electrical integrity is preserved throughout the aircraft’s operational life.

It is important to note that the ELA should also consider non-essential systems, such as Power Supply Systems (PSS) which connect aircraft electrical power to Portable Electronic Devices (PED). Future articles will explore how these systems impact the ELA and their Instructions for Continued Airworthiness (ICA) requirements.

Managing ELA Data

Operators need reliable ways to track and maintain their Electrical Load Analysis data. The three main approaches are:

• Spreadsheets
  Practical for operators with a single aircraft type or fleets supported by a dedicated Avionics or Electrical Engineering team. However, as fleets grow or include multiple aircraft types, maintaining accuracy becomes challenging, and spreadsheets alone may not fully prevent errors.

• Specialized Software
  Designed to automate calculations, handle complex fleet variations, and minimize errors. Software can improve efficiency and provide easier updates after modifications.

• Outsourcing
  When in-house expertise is limited, external specialists can perform or review ELA analyses. This ensures accurate, up-to-date documentation and compliance with regulatory requirements.

Conclusion

By carefully documenting loads, keeping records up to date, and managing them accurately, the ELA ensures that electrical systems can support all operational scenarios and maintain continuing airworthiness.