AirChime K5LA

The picture illustrates the K5LA as it is used by Amtrak and other passenger railroads, with all bells facing forward. The horn bells are numbered from largest to smallest; from left to right in the picture, the bells are numbers 5, 3a, 1, 2, and 4a. Freight railroads generally opt for the horn with one or more bells reversed. Common arrangements include reversing the #2 and 4a bells to give a K5LAR24 or the #2 and 3a bells to give a K5LAR23.

The K5LA was developed in 1975 for Amtrak at the suggestion of Deane Ellsworth. The horn was an adaptation of the AirChime K5H in which the #3 and #4 bells were modified to change the D# Minor 6th chord to B Major 6th. The "A" in the designation refers to this "American" tuning. The "L" in the designation indicates the use of a low-profile manifold, which was also developed specifically for Amtrak to meet their clearance requirements. All five horn bells are arranged in a low arc, compared to the 3-over-2 arrangement on the K5H. While there is nothing to prevent the "American" bells from being mounted on an H manifold to give a K5HA, this is rare. Amtrak did receive a few K5LA's with the horn bells spread over two separate manifolds, 2 bells on one and 3 on the other. These were used to replace the two-piece Leslie SL-4T horns on some of the later SDP40F's. The sound is the same regardless of the manifold used.

The picture at left illustrates the optional screen cones that could be applied to help keep insects and other foreign matter from fouling the horn. Many Amtrak F40PH's had horns with these screens. Three photos and horns at left courtesy Brent Lee.

As an attention-getter, the K5LA is effective almost to a fault. The horn is quite loud, to the point that residents along many commuter corridors have complained about the horns lifting them out of bed at night. Several operations have taken steps to either quiet the horns with choke fittings (see below), or position the horns so that the sound is focused down the tracks. Amtrak California's Pacific Surfliner cab cars sport their K5LA's in a recessed area just above the coupler, as shown in the photo at right, to minimize sound emanating to the sides or the rear.

This Metra cab car has a horn that probably started out as a K5LA, but has had the #2 and 4a bells removed and their positions blanked on the manifold. Whether this was done to quiet the horn, or because the two bells were damaged and not replaced, is not known.

Factory tuning is B major 6th: (D#,F#,G#,B,D#).

The horn uses the K-series #1, 2, 3a, 4a, and 5 bells.

Although it was designed for Amtrak, the first production K5LA's went to Chessie System on an order of GP40-2's. The horn is now the standard on Amtrak and numerous commuter railroads across the US. Freight carriers CSX and Norfolk Southern receive the K5LA (with reversed bells) on their new locomotives. In a somewhat surprising move, 3-chime adherant Union Pacific received K5LAR24's on one of its groups of new SD70M's delivered in 2001. The horn has also found its way onto a variety of shortlines.

K5LA sound samples:

Amtrak F40PH:
Sample 1...422kB...19 seconds
Sample 2...340kB...15 seconds
Sample 3...458kB...21 seconds
Sample 4...314kB...14 seconds
Sample 6...302kB...14 seconds

Amtrak F69PH-AC:
Sample 1...211kB...9 seconds

Amtrak Dash 8-32BWH:
Sample 1...438kB...20 seconds

Amtrak P42DC:
Sample 1...465kB...21 seconds

CalTrain F40PH-2 and cab car:
Sample 1...113kB...5 seconds
Sample 2...174kB...8 seconds
Sample 3...145kB...6 seconds

In response to complaints that the K5LA horn is too loud, some roads like CSX use the horns with restrictors or "choke fittings" installed. These cut down the supply of air to the horns and reduce the decibel level. The character of the horn is also changed, as these samples illustrate:

CSX, various locomotives:
Sample 1...194kB...9 seconds
Sample 2...629kB...29 seconds
Sample 3...567kB...26 seconds
Sample 4...459kB...21 seconds


Some K5LA horns have come from Nathan with standard #3 bells instead of #3a's. The resulting sound is sort of half-way between a K5L and a K5LA. Horns like this can be found on some Amtrak and Norfolk Southern locomotives.

Amtrak P42DC:
Sample 1...248kB...11 seconds
Sample 2...184kB...8 seconds
Sample 3...180kB...8 seconds
Sample 4...697kB...32 seconds
Sample 5...173kB...8 seconds

When bad things happen to good horns:

K-series horns are generally fairly durable, but under adverse circumstances, even they can "go bad." In the 1990's, in the interest of reducing the noise level in the locomotive cab, Amtrak began relocating the airhorns on their F40PH locomotives from a notch in the cab roof to a position between the exhaust stack and the dynamic brake fan (click for photo). Unfortunately, this is one of the hottest locations on the outside of the locomotive, and the horns are subjected to a constant diet of diesel exhaust. Over time, as a result of the heat and smoke, they develop a rather peculiar sound as bells start overblowing or "squealing," or stop sounding altogether. This is illustrated in the following samples. San Francisco Bay Area commuter railroad Caltrain had the horns similarly relocated on their F40PH's in the late 1990's, with similar results.

Amtrak F40PH's with "smoker's horns:"
Sample 1...307kB...14 seconds
Sample 2...332kB...15 seconds
Sample 3...194kB...23 seconds
Sample 4...66kB...3 seconds
Sample 5...268kB...12 seconds

Caltrain F40PH's with "smoker's horns:"
Sample 1...208kB...9 seconds

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