Blade Liberation
Definition
The detachment of a turbine or compressor blade from its rotor disk, creating a high-energy projectile inside the engine. Certification standards require the nacelle to contain the blade without catastrophic downstream damage.
- Event
- Turbine/compressor blade detaches from rotor disk
- Hazard
- High-energy projectile inside the engine casing
- Certification requirement
- Nacelle must contain the blade
- Field
- Aviation accident investigation, engineering
Common questions
Why is containment of a liberated blade a certification requirement rather than just a design goal?+
An uncontained blade can penetrate the nacelle and strike fuel lines, hydraulic systems, or the fuselage, so regulators require engine manufacturers to demonstrate through testing that the casing will contain a liberated blade before the engine type is certified for flight.
What evidence does an investigator look for to confirm blade liberation caused an accident?+
Investigators examine the fracture surface of the disk attachment point for fatigue striations or overload features, trace the liberated blade's damage path through the engine and airframe, and check whether the containment structure held or was breached.
Related terms
- Fracture Surface Analysis
- Examination of the broken face of a component to identify the failure mode. Beach marks and striations indicate fatigue, cleavage facets indicate...
- ICAO Annex 13
- The international standard that defines the objectives, conduct, and reporting of aircraft accident and serious-incident investigations. It establishes the state-of-occurrence as the...
- NTSB / AAIB
- National Transportation Safety Board (USA) and Air Accidents Investigation Branch (UK): the two national authorities whose technical methods and report standards most...
- On-Condition Maintenance
- A maintenance philosophy that retains components in service until inspection or sensor data indicates they have reached a defined deterioration limit, replacing...
- Pressurisation Cycle Fatigue
- Fatigue damage driven by the repeated inflation and deflation of the aircraft fuselage as it climbs to altitude and descends. Each flight...