How did they come up with 1472 days between major inspections?

[Ulrich]

1472 days or 15 years, which ever come first. How was 1472 days arrived at?

[Overmod]

It's actually four years, as in the old days of working steam, with the 15-year proviso enacted for locomotives that see only light or intermittent service (as on tourist lines or in fantrip service) but are still wearing out progressively...

The current version was developed with the assistance of people like Steve Lee and Lynn Moedinger, in case you worry it is some weird Federal boondoggle.

One reason why the 'math' appears strange is that a FRA 'quarter' is 92 days, and there are sixteen of these in 'four years' -- hence the number.  The 92-day "quarter" ensures you can have quarterlies scheduled on the same day of the month and never be 'late' -- which helps you remember when action is due.

Here is a link to a description of the evolution of the present rule.

[cefinkjr]

Ulrich

1472 days or 15 years, which ever come first. How was 1472 days arrived at?

 

That's always bugged me, too, Ulrich.  What kind of thinking, if any, went into selecting an interval of 4 years and 12 days (or 11 days if you use the more accurate 365.25 days per year to allow for Leap Year)?

 

I'm a retired System Software guy and weird numbers like this are always a warning of fuzzy thinking at best.

[Overmod]

I understand it a bit like this:

Reports are quarterly.  The Feds want a 'metric' that is consistent on a pure 'quarterly' basis.  Therefore we're going to calculate using a 'quarter' as the basis for statutory measurement, but then express the result in 'days'

Assume for a moment that we don't care about a calendar year as a measurement of elapsed time to servicing.  

Now: starting at January first, what is the 'longest' quarter of a year you will have?  This will be the standard length assigned to a 'quarter' to get a consistent length.  Note that the two last quarters of the year will have 92 days (31+31+30) in them.  So FRA standardizes on that length for a 'standard' quarter.

Four years, deemed to be 'four quarters each', produces 92 x 4 x 4 and voila! your day measurement.

 Perhaps it may help to think of the '4 year' period as 'statutory' years, rather than irregular calendar years.  It's an artifact of legislative interpretation, not a fundamental natural constant.

I doubt that you will get a complaint from the preservation community that they'd rather have the shorter 1461 days to a major just because the math works out more consistently if you're using a Gregorian calendar!

[cefinkjr]

Trust me; I'm not dissing you, Overmod, but I almost fell out of my chair laughing as I read your explanation..

Only a government bureaucracy could come up with that logic!  The last few years of my career dealt with Medicare claims, etc. and they too had their "standard quarter".  Pointing out that the fourth "statutory quarter" will eventually occur in the following calendar year draws a deer-in-the-headlights stare.  They don't seem to grasp the thought that normal people (non-bureaucrats) live in a real world with calendars that have been accepted for more than 400 years (since 1582 to be exact).

[Semper Vaporo]

To understand it, you really need to read that part 49 of the Code of Federal Rules document (49CFR230) referred to earlier in this thread.  VERY informative.  Here is the link again:

http://www.steamcentral.com/documents/49cfr230.pdf

 

It is not as bureaucratic as it appears... there was a lot of work that went into it by people that knew what they were doing.