2. Reliability



The objective of this test is to document unscheduled breakdowns, repairs, down time, and repair time that occur during testing.


                                                                                                 2-II.  TEST DESCRIPTION


Using the driver log and unscheduled work order forms, all significant breakdowns, repairs, man-hours to repair, and hours out of service are recorded on the Reliability Data Form.


                                                                                                     CLASS OF FAILURES


                                                                                 Classes of failures are described below:


(a)  Class 1:  Physical Safety.  A failure that could lead directly to passenger or driver injury and represents a severe crash situation.


(b)  Class 2:  Road Call.  A failure resulting in an en route interruption of revenue service.  Service is discontinued until the bus is replaced or repaired at the point of failure.


(c)  Class 3:  Bus Change.  A failure that requires removal of the bus from service during its assignments.  The bus is operable to a rendezvous point with a replacement bus.


(d)  Class 4:  Bad Order.  A failure that does not require removal of the bus from service during its assignments but does degrade coach operation.  The failure shall be reported by driver, inspector, or hostler.


                                                                                                       2-III.  DISCUSSION


A listing of breakdowns and unscheduled repairs is accumulated during the Structural Durability Test.  The following Reliability Data Form lists all unscheduled repairs under classes as defined above.  These classifications are somewhat subjective as the test is performed on a test track with careful inspections every two hours.  However, even on the road, there is considerable latitude on deciding how to handle many failures.


The Unscheduled Repair List is also attached to provide a reference for the repairs that are included in the Reliability Data Forms.



The classification of repairs according to subsystem is intended to emphasize those systems which had persistent minor or more serious problems.  There were no Class 1 or 2 failures.  Of the six Class 3 failures, four involved the suspension system and one with a tire and the electrical system.  These, and the one remaining Class 4 failure are available for review in the Unscheduled Maintenance List, located in Section 5.7 Structural Durability.




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