Gearbox Casing Crack Detection based on Vibration Signals in Frequency and Time Domain

Gearbox casing cracks in helicopters would be critical impacting the aircraft's reliability and operation safety directly. The Defense Science and Technology Group (DSTG) HUMS2025 gearbox casing failure data set was the unexpected result of a test stand operation. The gearbox undergoes high cycle (> 400 acquisitions) under high torque (100% and 125% nominal torque) conditions. We hypothesized that the any cracking would be due to the planet/ring gear interaction. A condition indicator (CI) would be sensitive to a crack feature and this would be sensitive to change in gearbox torque. This paper explores the development of both a cyclo-stationary based CI (frequency-domain) and a time synchronous average CI (time-domain). The trend shows that proposed methods can help to detect localized defects in gearbox casing at an early stage and trend as the crack propagates before catastrophic failure occurs.