We are working on an unit that will be used in helicopter.
The MTBF value calculated per MIL-HDBK-217FN2 is under the target value.
As you know, environment factors (πE) for the ARW conditions are very high.
To reduce the effects of shock and vibration, the related unit is mounted to the helicopter with the mounting tray having shock and vibration absorber.
We evaluated the rate of effect of shock and vibration in the ARW (Airborne Rotary Winged) environmental conditions, using some informations.
Also according to the measured test results, the mounting tray reduces the effects of shock and vibration coming from the platform.
As a result, we obtained some improvement in the stress values.
Our customer doesn’t accept to reflect the mentioned improvement to the MTBF value directly.
We consider using the inverse power law (IPL) model (or relationship) between the stress levels and MTBF as life characteristic.
But we need the model parameter n to be determined and it isn’t possible to perform accelerated testing for the moment.
Dou you have any information about model parameter n for shock and vibration stresses in helicopter or ARW (Airborne Rotary Winged) environmental conditions or can you suggest any other way or solutions for this mentioned subject?
Your prompt response will be greatly appreciated.
Thanks and best regards.
Microelectronics, Guidance & Elektro-Optics Division
Electronic Design Department