Page:NTSB - Railroad Accident Report - Derailment on May 25, 1989.djvu/55

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use must be made of the trottle modulation, throttle reduction and dynamic braking methods for slowing, controlling, and stopping trains. Unless rules specify otherwise, DURING PLANNED BRAKING OPERATION, IF ONE OR MORE OPERABLE DYNMIC BRAKES ARE AVAILABLE THE POWER BRAKING METHOD WILL NOT BE USED."

Of SP’s road fleet of 2,100 units, 1,800 units, according to the chief mechanical officer, are equipped with dynamic brakes. SP locomotives are designed such that when the train brakes are applied in emergency, an interlock will nullify the dynamic braking. According to SP’s chief mechanical officer, the system is designed in this manner "…to prevent train handling problems in the case of a break in two [a separation of two cars] and to prevent wheel slide because of excessive braking which would be the combination of the electric [dynamic] braking and the independent brake.…" He could offer no explanation as to why some railroads have modified the system to retain dynamic braking when the train brakes are applied in emergency. He stated that the SP had checked with the manufacturer and that the manufacturer "…will not make that modification for the SP or any other railroad." He further stated that the SP was not considering modifying the locomotives. The Safety Board contacted one manufacturer who indicated that any specifications requested by a carrier, as long as they were in compliance with Federal regulations, would be made. The Safety Board is aware that the Union Pacific and the Burlington Northern have their own retrofit program to eliminate the interlock feature.

Maintenance Reports and Reporting of Defective Locomotive Units.—SP Rule 2A requires the engineer to report locomotive defects to the dispatcher and to fill out a form outlining the defects. This form remains in the locomotive cab until the locomotive reaches an appropriate facility where mechanical department personnel can make the repairs. The head-end engineer testified that he complied with both parts of this rule with respect to the inoperative dynamic brakes on the lead locomotive unit, 7551. The helper engineer testified that he did not inform the dispatcher that the dynamic brakes on one of his helper units were inoperative because the dynamic brakes were inoperative when he began his tour of duty and he believed that the engineer whom he had relieved had reported the defect to the dispatcher. The assistant chief dispatcher who assigned the power (locomotive units) for the movement of Extra 7551 East testified that he does not request information from engineers and that he does not query the computer system[1] about the status of dynamic brakes on locomotive units. He further testified that it is the responsibility of engineers to inform him of any locomotive defects. He also stated that there are no written procedures that specifically address what to do with information received from engineers regarding defective locomotive equipment.

The chief mechanical officer testified that engineers, in addition to reporting defects to the dispatcher and filling out the appropriate form, will occasionally report defects directly to the roundhouse (engine repair

  1. SP’s computer system contains a listing of all locomotive units and the status of any defects reported.