Flight data and cockpit voice recorders are housed in armored enclosures engineered to survive impact forces up to thousands of Gs, fire, and deep-water pressure, because the recording medium is useless unless it outlives the aircraft. The recorder's value lies not in capturing data but in guaranteeing the data persists through the exact catastrophe it is meant to explain.
Investigators infer the sequence of failure backward from deformation patterns, soot deposits, fracture surfaces, and wreckage distribution, treating each physical mark as a timestamped record of force and temperature. The geometry of how metal bends, tears, or melts encodes the direction, magnitude, and order of the forces that acted on it.
Repeated pressurization and flight cycles grow microscopic cracks in aircraft aluminum that remain invisible and stable until they reach a critical length, at which point the remaining structure tears catastrophically in a single event. The danger is not force exceeding strength on any one flight but cumulative cycling that quietly erodes the margin over thousands of ordinary flights.
In 1988 an aging Boeing 737 operated by Aloha Airlines lost a large section of its upper fuselage at 24,000 feet, caused by fatigue cracks along rivet lines accelerated by salt-air corrosion over roughly 89,000 short inter-island flight cycles. The plane landed with one flight attendant lost overboard, and the case established that cycle count, not calendar age or flight hours, drives fuselage fatigue.
Whether occupants live depends less on impact speed than on how the airframe, seats, and cabin absorb and stretch out the deceleration over distance and time, keeping forces on the body below human tolerance. Seeing a crash as a deceleration-management problem reframes survival as a design variable rather than luck.