UA.I.E.K16: Impact kinetic energy.

ACS Area I — Regulations Task E: Operations Over People References: 14 CFRCode of Federal RegulationsCloseThe federal rulebook where Part 107, Part 89, Part 48, and other aviation rules live. parts 89 and 107; ACAdvisory CircularCloseFAA guidance that explains acceptable ways to comply with rules or understand FAA procedures. 107-2; FAAFederal Aviation AdministrationCloseThe U.S. aviation regulator responsible for Part 107 rules, airspace, and pilot certification processes.-H-8083-25; FAAFederal Aviation AdministrationCloseThe U.S. aviation regulator responsible for Part 107 rules, airspace, and pilot certification processes.-G-8082-22

Key Concepts

Understanding Impact Kinetic Energy in Operations Over People

Impact kinetic energy is a core safety and regulatory concept for operations over people under 14 CFRCode of Federal RegulationsCloseThe federal rulebook where Part 107, Part 89, Part 48, and other aviation rules live. Part 107. Knowing how to evaluate and apply impact energy thresholds is essential for determining what operations are permitted and for ensuring compliance with Category 2 and 3 requirements. The FAAFederal Aviation AdministrationCloseThe U.S. aviation regulator responsible for Part 107 rules, airspace, and pilot certification processes. uses limits on impact kinetic energy as a key method to reduce the risk and severity of injuries in the event of a small unmanned aircraft (sUA) falling onto a person. As such, understanding how kinetic energy is calculated—and how it applies to practical operations—is a major exam topic and an operational requirement for remote pilots.

Calculating Impact Kinetic Energy

Kinetic energy (KE) is a measure of the energy carried by an object due to its motion. For sUASSmall Unmanned Aircraft SystemCloseA small drone plus the control and communication links used to operate it., kinetic energy upon impact is determined by both the aircraft's weight and its speed at impact, and is calculated using this formula:

KEimpact = 0.0155 × w × v²

where:

• w = weight in pounds (lbs) of the sUA (including all onboard or attached components during operation)
• v = maximum impact speed in feet per second (ft/s)

For example, a 1.0 lb sUASSmall Unmanned Aircraft SystemCloseA small drone plus the control and communication links used to operate it. with a maximum impact speed of 26 ft/s would have an impact kinetic energy calculated as KEimpact = 0.0155 × 1.0 × (26)² = 10.5 ft-lbs. If the speed is increased to 40 ft/s for the same weight, the kinetic energy jumps to 24.8 ft-lbs^[4]. This demonstrates the critical importance of both mass and velocity: even a relatively light aircraft can exceed energy thresholds quickly at higher speeds.

Practical Application for Remote Pilots

Part 107 divides operations over people into Categories 1 through 4, with Categories 2 and 3 relying directly on kinetic energy limits as ‘performance-based safety requirements’. This means the aircraft must not exceed a specified maximum impact kinetic energy in the event of a failure or loss of control. Manufacturers and remote pilots must assess the worst-case scenario speeds that could result from system malfunctions, equipment failures, or pilot error, and use the above formula to ensure the sUA remains within allowable limits^[4].

Remote pilots are responsible for:

• Knowing the weight of the UASUnmanned Aircraft SystemCloseAn unmanned aircraft plus its control station, communication links, and supporting components. throughout flight (including temporary payloads or after-market attachments),
• Understanding the potential speed the UASUnmanned Aircraft SystemCloseAn unmanned aircraft plus its control station, communication links, and supporting components. could reach during uncontrolled descent,
• Verifying that the aircraft is authorized, labeled, and listed as eligible for operations over people in the relevant category,
• Consulting the FAAFederal Aviation AdministrationCloseThe U.S. aviation regulator responsible for Part 107 rules, airspace, and pilot certification processes.-accepted Declaration of Compliance (DOCDeclaration of ComplianceCloseManufacturer compliance document that matters for some Operations Over People categories.) and manufacturer instructions to stay within permissible impact energy limits^[8].

Operational Implications

• Pre-Flight: Always consider the effect of adding or removing payloads, or making modifications that could change the operational weight or falling speed—a heavier or faster aircraft may exceed category limits.
• Category Compliance: Ensure your sUA's impact kinetic energy is below the maximum permitted for the Category of operation (exact thresholds are determined by FAAFederal Aviation AdministrationCloseThe U.S. aviation regulator responsible for Part 107 rules, airspace, and pilot certification processes. testing and compliance procedures; do not estimate or invent values).
• Risk Mitigation: The calculation assumes full energy transfer (without accounting for energy-absorbing materials), so a conservative approach is required.
• Documentation: Maintain and review all required documentation, including remote pilot operating instructions and the DOCDeclaration of ComplianceCloseManufacturer compliance document that matters for some Operations Over People categories., prior to operations over people^[8].

By mastering the concept of impact kinetic energy and knowing how to monitor and comply with its thresholds, remote pilots can operate safely, responsibly, and in compliance with the law when flying over people.