We were told offshore some time ago that HUMS was a wonderful addition to helicopter safety. With this in mind, would someone care to comment on these words from the Interim Report:
These sensors had recorded increasing vibration
levels during the previous few flying hours prior to the
accident flight and were being monitored, in accordance
with the manufacturer’s maintenance manual.
It has raised questions out here on Safety Meeting Sunday - it would be good to give the troops some more feedback.
The following is from "AAIB Bulletin No: 8/2004" referring to the L2 G-JSAR incident, 22 February 2003. Though the actual failures are different, I find the similarities in the monitoring scenarios somewhat concerning.
On 21 February the RMS parameter threshold was breached, - this is also shown in Figure 4. This is the Root Mean Square of the signal and is a measure of the total energy, the value of which will tend to increase in the event of damage to the component. The EuroARMS Training Manual notes that defect detection using this parameter occurs "at a fairly late stage" in the damage process. Following a review of the thresholds, it was decided to continue monitoring both the RMS and the RMSR parameters. The MGB chip warning and oil cooler drive shaft failure occurred on the following day, some 21 flight hours after the initial alert on 21 February. The final EuroARMS data was sampled only 2 minutes prior to the chip warning.