Aircraft Accident and Incident Investigation — Page 492, Lesson 662

I want to walk you through the serious incident examples now. This is the heart of what separates a serious incident from a routine problem, and it's a list you need to know cold for the exam. Let me be clear about what this list is first: it's a set of typical examples, not an exhaustive catalogue. The book says it's guidance to the definition, so treat it as a strong indicator, not a closed list. Let's go through them one by one, because each one has a precise meaning. First, near collisions requiring an avoidance manoeuvre. That means you had to take evasive action to avoid a collision or an unsafe situation, or where such action would have been appropriate even if you didn't take it. The key word is "near" — you didn't hit, but you came close enough that action was needed or should have been taken. Next, controlled flight into terrain only marginally avoided. That's CFIT for short — the aircraft was flying normally under control, but was heading into the ground or an obstacle, and you only just managed to avoid it. "Marginally" is the operative word; if you'd avoided it by a wide margin, it wouldn't be serious. Then we have a cluster of runway events. Aborted take-offs on a closed or engaged runway. "Engaged" means the runway is in use by another aircraft or vehicle. So you've started your take-off roll and then had to reject it because the runway wasn't available. Similarly, take-offs from a closed or engaged runway with marginal separation from obstacles — you actually got airborne from a runway you shouldn't have been on, and you only just cleared the obstacles. And landings or attempted landings on a closed or engaged runway — same idea on the arrival side. Next, gross failures to achieve predicted performance during take-off or initial climb. "Gross" means a major shortfall — the aircraft didn't climb or accelerate anywhere near what was predicted. This is about performance, not a minor deviation. Then fires and smoke. This covers fires and smoke in the passenger compartment, in cargo compartments, or engine fires — even if you extinguished them with extinguishing agents. The fact that you put it out doesn't downgrade the seriousness; the event itself counts. Events requiring the emergency use of oxygen by the flight crew. That's a serious incident in its own right — the crew needed oxygen in an emergency context. Aircraft structural failures or engine disintegrations not classified as an accident. So the structure failed or an engine came apart, but it didn't meet the threshold to be called an accident — still serious. Multiple malfunctions of one or more aircraft systems seriously affecting the operation of the aircraft. Note "multiple" and "seriously affecting" — it's not one minor glitch, it's several failures that degrade the operation. Flight crew incapacitation in flight. A crew member became unable to perform their duties while airborne. That's always serious. Fuel quantity requiring the declaration of an emergency by the pilot. You had so little fuel that you had to declare an emergency — that's the trigger. Take-off or landing incidents including undershooting, overrunning or running off the sides of runways. Undershooting is landing short, overrunning is going off the far end, and running off the sides is exactly what it sounds like — departing the runway laterally. Systems failures, weather phenomena, operations outside the approved flight envelope, or other occurrences which could have caused difficulties controlling the aircraft. This is the catch-all — anything that could have made the aircraft hard to control. "Outside the approved flight envelope" means you exceeded the certified limits of the aircraft's performance or structure. And finally, failures of more than one system in a redundancy system mandatory for flight guidance and navigation. This is subtle. A redundancy system is one where you have multiple backup channels — say, two or three independent systems doing the same job. If more than one of those channels fails, you've lost your redundancy, and that's serious because it's mandatory for flight guidance and navigation. Now, the thread that ties all of these together: every single one is an event that, had it gone slightly worse, could have become an accident. That's why they're "serious." The list is guidance, not law — but in practice, if you see any of these in an exam scenario, you're looking at a serious incident.