CAT III Requirements

[middlepath]

Could anyone kindly explain why same type aircraft has diffrent CAT III requirements, eg: B757/767 if registration marked "N"(USA) it requires actual auto land satisfactory test every 28 days, where as in other countries there is no such requirements for the same type just a different registration marking.

Thanks.

[safetypee]

In addition to different regulatory requirements (FAR vs JAR), there are differences in the application of common sense across the Atlantic divide*.
Historically Cat 2 – Cat 3 systems required frequent checking to meet the stringent reliability targets set by the certification standard.
Modern systems are much more reliable and used more frequently; some have self checking modules which alert the crew to unavailability at any time during flight.
I suspect that there are authorities who elect not to change rules until all systems can meet current standards, elsewhere rules are adapted and modified, dispensations granted, and systems evaluated on merit.
* excluding N of 49 N?

[Short_Circuit]

Safety costs money..

Extra checks = Extra cost

[middlepath]

Thanks for the input:ok: