> >and the unexpected or unrealized partial or full
> failure can quickly get you in trouble, especially
> if your expected stopping distance or grade speed
> balance is based on the dynamics working with no
> or little room for compromise.
>
> If you get in this sort of a jamb, how did you get
> qualified as an engineer?

Funny thing is I have spent far more time as an engineer without dynamic brakes and run most trains with air only. I like dynamics and don't have an issue running with them. But the simple fact is every engineer has had and will have a train try to get away from them. Even moving trains of the same size over the same territory, most will behave as expected but some just won't. I've seen too many engineer's that did not have controll of their train, and the dangerous thing is that they did not have the skill/experience/training to realize it. Most commuter and regional passenger operations expect the engineer to operate the train at full performance, accelerating and decelerating to meet the schedule or gain time when running late. WHy do you think they keep increasing the commter locos horsepower? In most cases, it isn't needed to maintain track speed but to accelerate faster. Same thing with dynamics - the engineer's are expected to come roaring into a station and hit their mark - every time - regardless how well the brakes work. If the dynamics fade or drop out, then the engineer has to take quick action to get it stopped/slowed in time. Not the ideal situation, not consistent with many rules/regulations, but what the rules say isn't exactly common practice on the railroad.


> This is not quite what I've observed in 25+ years
> of operating psgr engines equipped with blended
> braking.

Both NYAB/Knorr and Wabtec/Wabco have issued insturction manuals describing braking systems and including recommended piping arrangements. Most of the 6ET/14EL/6BL and older systems tend to follow these designs, but of the many 26L/NL systems I have worked on, I don't think a single one has matched a Wabco/NYAB standard print. The most common substitution is Salem 596/599 check valves and replacing older dead engine arrangement with the newer pressure regulator arrangement - both of which I totally agree with. Railroads couldn't even agree on a dynamic brake interlock arrangement, one bails off the engine, the other releases the engine brakes but will reapply any automatic brake application not bailed off by the engineer if dynamics are dropped. I believe there may be a third version that drops dynamics once a certain engine brake cylinder pressure is reached (different from the IPS dropping extended range). 26NL actually comes in two very differing versions, one acts like 6/14 were you have to bail any engine brake application if an automatic brake application is in effect, the other acts just like 26. Then there is 26 Universal and the various 6BLC arrangenets. Air brake and train handling rules also vary greatly. There are some basic requirements in the 49CFR that the railroads have to comply with, after that it is a free for all and at times railroads have very different ideas compared to each other.

When discussing technical aspects of railroading, you have to realize that there are always exceptions. Even though the GCOR is supposed to be the common rule book for almost every railroad in the west, you start looking at the Special Instructions and it becomes clear that the railroads all have a different idea. I'm amazed on how confusing it has become to repeat a track warrant with the differences now between railroads. To every rule or typical practice, there is always an exception.