Statistic analysis of airplane accidents

4. When do accidents occur?

Between the time a passenger boards an airplane and the time they disembark, there are 6 distinct phases:

• Taxi: the aircraft taxis to reach the runway, or it taxis to the gate after landing.
• Take off and initial climb: the aircraft accelerates, lifts off and starts climbing.
• Climb: the pilot retracts the slats/flaps, and the aircraft climbs until it reaches cruise altitude.
• Cruise: the aircraft flies at a more or less constant altitude. This is generally the longest phase of the flight.
• Descent and initial approach: the aircraft descends to get closer to its destination airport. Air traffic control may request the aircraft to loiter and wait its turn for the next phase.
• Final approach and landing: the aircraft, in landing configuration and aligned with the runway axis, approaches the runway threshold, then lands and slows down.

When do accidents occur?

Over half of all accidents occur during the final approach and landing stages. These aren't the most devastating accidents, however. A runway overrun may result in only a few injuries, for example.

Fatal accidents are more likely to occur during the climbing stage. If the aircraft left the gate with undetected faults, these may become apparent during the climb, as the first stage taking place off the ground, and could prove dangerous. If the crew believe the failure requires the aircraft to land as soon as possible, they will decide to perform an IFTB (In-Flight Turn Back). This could turn out to be difficult, however, as the aircraft may have already lost some of its capabilities.

Most accidents and fatalities take place during the departure (take off / climb) and arrival (approach/ landing) stages. During these phases aircraft are close to the ground and in a more vulnerable configuration than during other flight phases: the crew have to deal with a high workload and reduced manoeuver margins.