I actually have more years' experience maintaining aircraft than you, Perspective. That's one of the reasons I don't lose my temper when my aircraft comes out of maintenance with new, human-induced problems (and a bill in the double-digit thousands). I know, from long, first-hand experience, what goes on during maintenance and how easy it is to make mistakes.
I know what point you are trying to make. That you believe some maintainers over maintain for no benefit to safety.
No, that's not the point I was trying to make.
I apologise for not being clearer.
The point I'm trying to make is this: The data
prove that
some periodic maintenance required by
manufacturers' maintenance manuals is
unnecessary and counter-productive.
What I said in my first post on this thread was:
Most manufacturer's maintenance schedules require too much unnecessary maintenance and not enough necessary maintenance ...
An experienced maintainer will know how and when to do more of the necessary maintenance and less of the unnecessary maintenance.
You see: I'm actually advocating "more" - i.e. an increase in the amount of - maintenance. But only of the necessary stuff.
And that's not the same as saying leave everything alone until it breaks.
When people refuse to accept the implications of the data and instead treat a time limit in a maintenance manual as holy writ, it is indeed regulation by gut feeling rather than science. Old Wive's Tales rather than data.
I did chuckle at your mention of vacuum pumps. We'll have to agree to disagree on whether maintenance against schedule 5 provides more flexibility than the manufacturer's maintenance schedule. (I'm pretty sure there are lots of aircraft flying around with control cables more than 15 years old, despite the manufacturer's maintenance schedule, but I must be mistaken.)
The most authoritative link drawn between component time limits in maintenance manuals and schedule 5 was drawn by Egon Fice in the
Brazier decision. Although my view is that Egon got it wrong on the legal reasoning, that's neither here nor there at the moment. The irony of the decision is that it provides another example,
par excellance, of how arbritray the life limits in manufacturers' maintenance manuals are.
One of the many atrocities alleged by CASA against Mr Brazier was that he didn't replace an aircraft's vac pumps at 500 hours TIS or 12 monthly, which ever came first, in accordance with the Service Manual. At the time this atrocity was detected, the left hand pump had overrun by 886.9 hours and was still going strong. The right-hand vacuum pump had overrun by
1599.6 hours.
Imagine the horrific risks to aviation safety that arose when those pumps went past 500 hours' TIS, then the right hand pump went past 1,000, then 1,500 ... Oh the humanity!
Anyone who's run an aircraft with a vac pump or two knows when they're most likely to fail, and why.