A fatigue life gauge, mounted on a mechanical amplifier and bonded to a structure, will integrate the load/frequency pattern to which it is exposed. Subject to static calibration establishing the strain/load relationship registered by the device, gauge manufacturers data will closely predict the output for programmed loading within the range of 0–2 to 40 ohms. The purpose of the device is to compare the rate of loading, accumulated by a test structure, with the rate accruing to similar structures undergoing variable service loading. Inasmuch as this loading affects the fatigue life of a component, the device will monitor fatigue damage. Some agreement is shown between laboratory test of an aircraft fin and measurements taken during routine flying. The device is sensitive to change in aircraft utilisation. In the case of fin structure, no correlation exists between the measured damage factor and the damage assessed by the standard aircraft fatigue mete