Definition
A rate of descent that has become so high, so close to the ground, that the airplane cannot recover before impact regardless of pilot input or available engine power. Once entered, the combination of altitude lost, energy state, and aircraft performance limits makes arresting the descent impossible in the time and height remaining.
Plain English
The airplane is going down so fast, and is so low, that there is no longer enough height or power left to stop the descent before hitting the ground.
Context Anchor
Seen in low-altitude maneuvering, approach, flare, and go-around discussions, especially when the airplane is slow or close to the ground.
Derivation
Irreversible comes from the Latin reversus, meaning 'turned back.' Adding the prefix 'ir-' (not) gives 'cannot be turned back.' In this term, it describes a descent that has passed the point where it can be reversed in time.
Why Pilots Care
Failure to prevent it leads to hard landings, runway excursions, or accidents; maintaining proper airspeed and energy state is the direct defense.
Analogy
It is like braking too late before a stop sign on a wet road. Even if you press the brake fully, there may not be enough distance left to stop in time.
Grounding Statement
Picture an airplane low over the runway, still descending fast, with too little height left for the descent to be arrested before touchdown.
Intuition Check
Irreversible does not mean the airplane can never climb again. It means the descent cannot be stopped soon enough with the height and performance still available.
Example Sentence 1
The instructor emphasized adding power at the first sign of a high descent rate on final, before it could develop into an irreversible sink rate near the runway.
Example Sentence 2
Wind shear on approach can quickly turn a normal descent into an irreversible sink rate if airspeed is allowed to decay.