# Project #58294 - Week 11 Homework

1. Chapter 2, page 78, Problems, #8

2. Chapter 2, page 80, Problems, #14

3. Chapter 2, page 81, Problems, #17

4.   A piece of electronic equipment used for aviation has three elements connected in series, or sequence.   The reliability of each of the three elements is as follows:

Element A:   0.92                                         Element B:   0.94                                         Element C:   0.91

a)   Draw how these three elements are connected.

b) What is the reliability of this system?

c)     Suppose we wanted the reliability to be at least 0.85 by upgrading Element C with a higher reliability.   What would the reliability of Element C need to be?

d)   Instead of increasing the reliability of Element C, each of the elements is supported by an identical element in parallel as a back-up.   What is the reliability of this system?

5.   Let's revisit the preventive maintenance problem discussed in the webinar.   A hospital has seven large identical heat pumps. If one of the heat pumps malfunctions, it could seriously impact hospital operations. If preventive maintenance is performed weekly, it costs \$1200 to perform preventive maintenance (PM) on all seven of them.   If one of the heat pumps breaks down between PM inspections, the average cost to the company of a breakdown is \$2200.   The historical data for the heat pumps is as follows:

 Weeks between Preventive Maintenance Expected Number of Breakdowns between Preventive Maintenance 1 1.10 2 2.52 3 4.63 4 8.27

Now suppose that for each week that preventive maintenance is delayed, the cost to the company of a breakdown increases by \$200 (for example, if preventive maintenance is every week, the cost of a breakdown is \$2200 and if preventive maintenance is every two weeks, the cost of a breakdown is \$2400, etc.)   Based on the above information, what Preventive Maintenance policy do you recommend?   Why?

6.   Ethical Dilemma #3

When a McDonnell Douglas DC-10 crashed over Iowa, a subsequent investigation suggested that the plane's hydraulic systems did not provide enough protection.   The DC-10 had three separate hydraulic systems, all of which failed when an engine exploded.   The engine threw off shreds of metal that severed two of the lines, and the third line required power from the demolished engine that was no longer available.   The DC-10, unlike other commercial jets, had no shutoff valves that might have stemmed the flow of hydraulic fluid.   Lockheed's similar L-1011 tri-jet had four hydraulic systems.   A McDonnell Douglas VP said at the time.   "You can always be extreme and not have a practical airplane.   You can be perfectly safe and never get off the ground."

1. Discuss the pros and cons of McDonnell's position as expressed by the VP.
2. What strategy would you have recommended McDonnell Douglas follow to address the failure?   Why?

 Subject Business Due By (Pacific Time) 02/20/2015 12:00 am
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