Lavionic Reliability Basics Calculator

• The kind of system: one item, items in series (any one failure is a loss), redundant items (all must fail), or a redundant pair with a hidden failure.
• The MTBF of each item in hours, from the supplier data sheet or your own field data.
• The length of one flight, and for a hidden failure the flight hours between two checks.
• The severity of the failure condition: Minor, Major, Hazardous or Catastrophic, from your functional hazard assessment.

• The average probability of the failure per flight hour.
• Its probability class of AMC 25.1309: Probable, Remote, Extremely remote or Extremely improbable, and whether it meets the target for the severity.
• A block diagram of the system and a bar with the probability classes.
• The failure rate of each item and how the items combine.
• An edit panel: change one value and the result follows at once.

Use it online in your browser, or download it once as one HTML file. The file opens in Chrome, Safari, Edge or Firefox, works without an internet connection and sends no data anywhere.

The tool compares a result with the AMC 25.1309 classes for CS-25 aeroplanes. For a UAS, other values can apply.

The calculator is an aid, not a means of compliance.

• AMC 25.1309 (CS-25)
• ARP4761A / ED-135 (method names, in own words)