In engine investigations, what are the four compressor failure modes?

• A. FOD; Blade failure; Serration failure; Disc failure / chunking
• B. FOD; Blade failure; Disc failure; Serration failure
• C. FOD; Serration failure; Disc failure / chunking
• D. Blade failure; Serration failure; Disc failure / chunking; FOD

Answer: (A)

The question focuses on the four ways a compressor can fail in an engine investigation. The four recognized compressor failure modes are: foreign object damage (FOD), blade failure, serration failure, and disc failure with chunking.

Foreign object damage occurs when debris is ingested into the compressor, leaving impact marks, nicks, or missing material on blades and vanes. This damage can initiate cracks or lead to imbalance and further failures.

Blade failure refers to the fracture or separation of individual blades due to fatigue, corrosion, or overload. When a blade fails, fragments can be released and cause additional damage downstream.

Serration failure involves the failure of serrated features, such as blade roots or vane/segment interfaces, which can produce misfit, increased vibration, and debris release. This mode highlights problems at the serrated contact points rather than broad blade or disk damage.

Disc failure or chunking is a structural fracture of the rotor disk itself, potentially producing large chunks. This is often catastrophic and can be a consequence of other damage accumulating in the compressor.

Among the options, the only set that lists these four modes exactly is the one containing FOD, blade failure, serration failure, and disc failure / chunking. The other choices omit one of these modes or reorder them in a way that doesn’t match the standard four compressor failure modes.