Santa Fe Alcos

Three American Locomotive Company (Alco) PA-1 units with a cabless PB-1 unit are seen at Tehachapi, California (see earlier posts) in July 1965.

The A1A-A1A family of diesel-electrics denoted PA were built in two different models: the 2,000 horsepower (1,500 kW) PA-1/PB-1 built between September 1946 and June 1950; and the 2,250 horsepower (1,680 kW) PA-2/PB-2 built between April 1950 and December 1953.

Aside from the small power increase between the PA-1 and the PA-2, differences between the models were minor. Internally, later PA-2 and PB-2 production featured a water-cooled turbocharger and other engine compartment changes, but these were frequently added to older models undergoing major repairs and/or overhauls.

Like the smaller Alco FA, the PA had distinctive styling, with a long, straight nose tipped by a headlight in a square, slitted grille, raked windshields, and trim pieces behind the cab windows. The overall appearance owed something to the Fairbanks-Morse Erie-built design, which had been constructed by Alco's electrical equipment supplier General Electric at their Erie, Pennsylvania, plant. Most PA components were compatible with the FA.

Railfans often called the PA an "Honorary Steam Locomotive", because of a peculiarity of the Alco 244 diesel prime mover when accelerating: until the turbocharger came up to speed, thick clouds of black smoke would pour from the exhaust stacks due to turbo lag.

The Alco 244 V16 diesel prime mover proved to be the undoing of the PA: the engine had been rushed into production and proved to be unreliable in service. The PA locomotives failed to capture a marketplace dominated by General Motors Electro-Motive Division (EMD) and their E-units. The original Santa Fe three unit set 51L, 51A and 51B was repowered in August 1954 with EMD 16-567C engines rated at 1,750 hp (1,305 kW). But this EMD repowering of the PAs was economically unfeasible and the remaining Santa Fe PAs retained their 244 engines. The later 251-series engine, a vastly improved prime mover, was not available in time for Alco to recover the loss of reputation. By the time the Alco 251 was accepted into widespread use, General Electric (which ended the partnership with Alco in 1953) had fielded their entries into the diesel-electric locomotive market. General Electric eventually supplanted Alco as a loco manufacturer and Alco's demise occurred in 1969.