Help Documents

Mathematical Models Spares Calculator optimizes spare parts using a logorithmic poisson distribution as prescribed by Dr Sherbrooke and Dr Feeney in their work for the US DoD in the 1960’s. These models are now the industry standard and are used in nearly every spare...

Spare parts obsolescence and redundancy are an important factor in managing the lifecycle of a typical high value system. Electronic components typically have short production lifecycles, typically 2-5 years and even military suppliers have difficulty maintaining...

Here is an example of a recent question that we were asked by a client. I have a unit that with a lifetime of 10 years and I want zero stock-out-risk. How many spare parts should I recommend? The short answer to this is infinity spare parts. Only infinity spare parts...

Many items in a typical inventory do not actually get repaired and they are simply discarded on failure. These are known as items with a Discard on Failure Repair Policy. A customer recently asked: How should I model with items that have a discard on failure repair...

One of our customers recently asked: The budgets of our customers are being continually slashed, yet they still want and need the same level of spare parts support. Is there a way of using Spares Calculator to help them spend their money more wisely so that they get...

In this article we show how to convert the Probability of Availability to Stock-Out-Risk or Mean-Time-Between-Stock-Out for Spare Parts inventory. Problem Spares Calculator can forecast [Stock-Out-Risk],  [Mean Time Between Stock-Out] and [Probability of Availability]...

Why use a MTBSO (Mean Time Between Stock-Out) goal? Why not use Stock-Out-Risk or Availability? Problem a) No Time-Frame Often requirements documents will specify something like, “spare parts availability shall be 95%”. What does this mean? Nothing. For an...

How to calculate the No Fault Found Ratio for a Line Repairable Unit. Background Technicians often remove Line Repairable Units (LRUs) when there is nothing wrong with them. If they send the LRU back to the service centre and it is diagnosed as serviceable this is...

Availability Availability is the probability that a spare part will be available in the spares pool when demanded to carry out a repair during the Repair Delay period. For example, a stock-holding of 10 spare parts might have an Availability probability of 90% in a...