All About the Nathan P5a Train Horns

In 1975, Deane Ellsworth who was originally from Chessie ventured for a career at Amtrak. Elsworth's tenure in Amtrak included an idea to develop a train horn to substitute the Leslie SL-4T that was used on the SDP40F locomotive models. The search for the horn resulted to the birth of the Nathan P5a. During these times, development on better maintenance measures was becoming invaluable for railroad companies and for other shortlines as well. Subsequently, the P5's were better options compared to M5's regarding maintenance expenditures. Obviously, railroads executives were noticing the ever expanding varieties of train horns and have realized the importance of more conventional ideas for development. Not only did newer train horns contributed in smart accounting, but also in better operations as well.

Shorthand for P1234a5, the P5a includes a new, P-manifoldwith a low profile ( or base.) This special arrangement of the base, allows the two train horn bells which were originally under the base to be placed on the sides of the manifold. The horn is given the designation, PL5a, because of the two train horn bells that were moved from their previous architecture. The vertical plane originally contained all the back caps that were on the P5 manifold design. The physical design pf the P5a did not differ much on other P5 manifold designs, except for the two bells that were unique to the sort.

This train horn uses a #4a bell tuned to A# to produce a harmonic C# diminished chord, which was also the same chord Bob Swanson originally conceptualized for the M5 train horns. The P5a was first installed on an Amtrak P30CH locomotive, also known as the turbo train. The horn was also used on the F40PH's (200-299) which was, in turn, replaced by the K5LA. A more popular user of the P5a's was Metra, a Chicago-based commuter railroad. A lot of Metra's train horns had the #4a bell to be inverted, which made the commuter trains presumably having the P5a installed.

The P5a's visual design includes optional screen cones to repel insects and foreign matter out. This was common among P5's to keep unwanted particles from coming in the bells, not only to avoid the disruption of sound but also to lessen or better yet save up on maintenance. Amtrak 229, the last of the Amtrak F40PH series of locomotives, was the first locomotive to have the P5a on its physical design. The P5's have the distinct "out of tune" horn bells that was a unique characteristic apart from the other train horns. The implementation of this train horn on the 229, gave birth to a handful of dischordant or "out-of-tune" P5a's in the line.

Original tuning of the P5a was a C# diminished (C#dim). The horn had in its design the #1, 2, 3, 4a and 5 bells that were stereotype of the P-series. A lot of the P5's were slowly going out of production, because Amtrak were revamping the F40PH trains with better performance locomotives. But some can still be seen installed on some locomotives from Norfolk Southern (previously Southern) and on some Metra F40PH locomotives.