There seems to be a continuing interest in assigning phases to the various models of Diesels. Here is my take on these. Phases are an invention of various writers seeking a way to differentiate between external changes during production of a particular Diesel. There have been many "Phase" lists published. Some of these seek to break down into futher sub-phases and sub-classes. This is an interesting exercize but doesn't help if all are not using the same classifications. This listing characterizes the basic spotting features of the "as delivered' units and is not an exercize in delineating phases, sub-phases and variations of the sub-phases. For those who are interested in this type information I highly recommend J D Thompson web site

This phase listing is to aid the modeler in selecting the model with the best characteristics for modeling a particular diesel. These Phases correspond to those used by the model manufacturers. After the model is selected some more minor modifications may have to be made to match the exact diesel you are modeling. Working from dated photographs will allow your model to be correct for the time period you are modeling. Undated photos may be used, however, the model may not be correct for that time period. This may or not be of importance to your particular needs, if not, a factory painted model without modifications may be just the ticket. Please feel free to offer a comments/questions/additions.

Manufacturers would build a basic diesel over a period of time and would incorporate running changes into that diesel. From the beginning of production to the end the diesel model could and did change it's external appearance. This caused a good deal of confusion among those taking pictures and subsequently mislabeling them. "Phases" were not used by the manufacturers, these designations were developed by railfans and modelers to describe visual differences in units. Alco catalogued their production by an engineering specification numbers such as "E-1661" for the first RS-2 in 1946. Baldwin had their own system such as VO-1000 for cataloging their models. EMD had several systems such as FT, GP, SD etc. for designating their diesels. Fairbanks-Morse had a system of their own, CFA-16-4, Which was ok for a particular diesel, others were named for where they were built. General Electric developed a "U" class for the road engines, but never came up with system for switchers. All these designations are explained in the "ACRONYMS" section.

Phase designations begin with the initial production model. Demonstrators are not included. Standard factory options are excluded from the Phase designations.
These items include but are not limited to dynamic brakes, headlamp options, MU receptacles, MU hoses, High noses**, bi-directional control stands and other internal changes which don't affect the external appearance.
** Hi and lo noses are noted in the phase listings for each builder.

Phases only apply to production models "as delivered". Accessories or field modifications added by the owner could change the appearance of the unit. Examples of these are paint schemes, decals, AAR mandated changes, such as removal of pilot steps, addition of grabs, removal of items such as steam generators or plating over of window glass are all excluded from "Phase" designations.

What we are looking for are the external spotting differences of the basic models such as "F","GP","RS", "C" etc. units. Use of good pictures will allow one to determine the basic model and phase.

This "Phase" guide is like a road map, shows how to get to the basic model. Once there a more detailed guide is needed. This is good clear pictures showing the details. "Phases" are shown under each Diesel Builder
Thanks for reading this explanation...............(hosam)

S.A. McCall