14 C.F.R. § 450.131 – Probability of failure analysis.

(a) General. For each hazard and phase of flight, a flight safety analysis for a launch or reentry must account for vehicle failure probability. The probability of failure must be consistent for all hazards and phases of flight.
1. (1) For a vehicle or vehicle stage with fewer than two flights, the failure probability estimate must account for the outcome of all previous flights of vehicles developed and launched or reentered in similar circumstances.
2. (2) For a vehicle or vehicle stage with two or more flights, vehicle failure probability estimates must account for the outcomes of all previous flights of the vehicle or vehicle stage in a statistically valid manner. The outcomes of all previous flights of the vehicle or vehicle stage must account for data on any mishap and anomaly.
(b) Failure. For flight safety analysis purposes, a failure occurs when a vehicle does not complete any phase of normal flight or when any anomalous condition exhibits the potential for a stage or its debris to impact the Earth or reenter the atmosphere outside the normal trajectory envelope during the mission or any future mission of similar vehicle capability.
(c) Previous flight. For flight safety analysis purposes—
1. (1) The flight of a launch vehicle begins at a time in which a launch vehicle lifts off from the surface of the Earth; and
2. (2) The flight of a reentry vehicle or deorbiting upper stage begins at a time in which a vehicle attempts to initiate a reentry.
(d) Allocation. The vehicle failure probability estimate must be distributed across flight phases and failure modes. The distribution must be consistent with—
1. (1) The data available from all previous flights of vehicles developed and launched or reentered in similar circumstances; and
2. (2) Data from previous flights of vehicles, stages, or components developed and launched, reentered, flown, or tested by the subject vehicle developer or operator. Such data may include previous experience involving similar—
  1. (i) Vehicle, stage, or component design characteristics;
  2. (ii) Development and integration processes, including the extent of integrated system testing; and
  3. (iii) Level of experience of the vehicle operation and development team members.
(e) Observed vs. conditional failure rate. Probability of failure allocation must account for significant differences in the observed failure rate and the conditional failure rate. A probability of failure analysis must use a constant conditional failure rate for each phase of flight, unless there is clear and convincing evidence of a different conditional failure rate for a particular vehicle, stage, or phase of flight.
(f) Application requirements. An applicant must submit:
1. (1) A description of the methods used in probability of failure analysis, in accordance with § 450.115(c); and
2. (2) A representative set of tabular data and graphs of the predicted failure rate and cumulative failure probability for each foreseeable failure mode.