Lcs 500

This report is available at http://www.svc.ford.com/svc_quality/10YR150K.PDF

10 years/150,000 miles reliability: What does it mean?

Small & Medium Vehicle Centre Vehicle Centre Quality Review September 2, 1998
Note: Since this paper was first written, and filed in the Sept. 2, 1998 VCQR binder, some minor corrections to grammar and wording have been made. These changes are highlighted by a vertical bar on the left hand side of the page, similar to the one opposite.

Prepared: Tim Davis (TDAVIS5) SVC Quality Office 8-70-33149 D-MC/PI-1

Purpose: to clarify the definition of 10 years/150,000 miles (10/150) reliability, as it relates to automotive engineering, and to frame the discussion within the context of how we should set reliability targets for vehicle programs. i.e. we try to answer the question “what does 10 years/150,000 miles reliability mean?”. A good starting point is the AVT definition of 10/150 reliability, developed from pre-Ford 2000 reliability work in NAAO and EAO, and is “Satisfy Customer expectations for reliability throughout a vehicle useful life of 10 years or 150,000 miles (whichever is tougher)” Background: Reliability, as a mathematical concept, represents a measure of probability that a specimen remains free from failure within a specified period of either years or miles or cycles. This concept is sketched out in Box 1 on the facer. Ten years is considered a “reasonable period” over which a vehicle is used, and about 10% of our customers do more than 150,000 miles in this period. An engineering definition of reliability is failure mode avoidance. Avoiding failure modes increases the probability of failure free operation. Types of failure: The definition of failure is crucial to reliability assessment. Failures can be soft (degraded performance to an unacceptable level) or hard (product function ceases). Usually hard failures relate to components, while soft failures relate to systems. Professor Don Clausing (MIT) has categorized