Main Theme: This federal regulation details the safety requirements for aircraft seats and restraint systems during emergency landing scenarios. It outlines specific dynamic test conditions and performance criteria to ensure occupant protection.
Source: eCFR :: 14 CFR 25.562 -- Emergency landing dynamic conditions. (FAR 25.562)
Date Accessed: October 24, 2024
Key Points and Facts:
Applicability: The regulation applies to all transport category airplanes, dictating the design standards for crew and passenger seats and restraint systems.
Emergency Landing Conditions: The regulation defines two primary emergency landing scenarios for testing:
Vertical Descent: A downward vertical velocity change (Δv) of at least 35 feet per second, with the airplane pitched down 30 degrees.
"Peak floor deceleration must occur in not more than 0.08 seconds after impact and must reach a minimum of 14g." (§ 25.562(b)(1))
Longitudinal Impact: A forward velocity change (Δv) of at least 44 feet per second, with the airplane yawed 10 degrees to either side.
"Peak floor deceleration must occur in not more than 0.09 seconds after impact and must reach a minimum of 16g." (§ 25.562(b)(2))
Test Procedure:
Each seat design must undergo dynamic testing or be validated through rational analysis based on similar seat tests.
A 170-pound anthropomorphic test dummy is used to simulate an occupant.
Performance Measures: The regulation sets various performance limits to ensure occupant safety:
Restraint System Loads: Limits are placed on the tension loads for upper torso restraint straps.
"tension loads in individual straps must not exceed 1,750 pounds." (§ 25.562(c)(1))
Spinal Compression: The maximum force on the dummy's spine must not exceed 1,500 pounds.
Restraint System Integrity: Both lap belts and shoulder harnesses must remain in place during the impact.
Head Injury Protection: The regulation uses the Head Injury Criterion (HIC) to limit potential head trauma, with a maximum value of 1,000 units.
Leg Injury Protection: Measures are in place to prevent leg injuries, specifically limiting the axial compressive loads on each femur to 2,250 pounds.
Seat Attachment: Despite potential structural yielding, the seat must remain attached at all its points.
Evacuation Considerations: Seat yielding under the test conditions must not hinder the rapid evacuation of occupants.
Conclusion: This regulation plays a crucial role in ensuring passenger and crew safety during emergency landings by setting rigorous standards for seat and restraint system performance. The defined test conditions and performance criteria aim to mitigate the risks of severe injury during such events.
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