wangdayun
8th Jun 2009, 01:52
Please help me ! My study is about CMRs, but I can't find any data about the history of the CMR.Why do we start CMR ? I guess that maybe there is a terrible air disaster to cause CMR item start, and "what introduced the very first ever CMRs?"
Mad (Flt) Scientist
8th Jun 2009, 02:38
No.
CMRs are first put in place by the OEM during the design and certification phase.
Typically, the safety analysis for a system will reveal that a given system has dormant failures which, if not detected by a dedicated check, will result in an unacceptable in-flight hazard. Consequently, it becomes a certification requirement that a maintenance action be performed so as to detect the failure before it becomes a hazard to flight.
The CMRs are thus a means of ensuring, by ground inspection, that the necessary redundancy is present. (Generally CMRs relate to dormant failures in redundant systems, which by their nature are hard to detect through normal operations).
For example, let's say I have a primary flight control load path and a secondary one, with the secondary one not normally used, but required in the event of a failure of the primary system. I'd never know in-flight if the secondary system was failed - until I needed it.
So the OEM will look at the expected failure rates of primary and secondary and decide that the longest amount of time it's safe to "not know" about the backup is 100 hours. Presto: 100 flight hour CMR to inspect the secondary load path.
Unless your question was "what introduced the very first ever CMRs"?
Could there be some confusion here over CMR = Certificate Of Maintenance Review?
Carried out at 90-day periods to review the maintenance status of the aircraft (and dissolved for SMP-20 AMP aircraft in the late 90's?)