Lecture 1 - Context + RAMS

Question 1

RAMS (abbr.)

Answer 1

Reliability, Availability, Maintainability, Supportability.

Question 2

Functionability (def.)

Answer 2

The inherent ability of a system to perform a required function with specified performance requirements and attributes, when it is utilized as specified (under certain operating conditions)

Question 3

Aircraft environmental flight envelope (def.)

Answer 3

A given range of static temperatures and altitudes (pressures) an AC is designed to operate in.

Question 4

Failure (def.)

Answer 4

1. Every system is typically functionable at the beginning of its operational life.
2. Irrespective of the perfection of the system design/technology, during operation changes occur.
3. Changes that result from physical processes such as corrosion, abrasion, fatigue, deformation etc.
4. As a result, the system output deviates from the specification.

“Event that results in either loss of ability to perform the required function or satisfy the required performance requirements”

Question 5

Failure mechanism (def.)

Answer 5

The physical process that leads to failure.

Question 6

Failure mode (def.)

Answer 6

The way a system or component functionally fails, that is, extent a certain function cannot be fulfilled anymore.

Question 7

SoFu (def. + expl.)

Answer 7

State of functioning: system is functionable or in a ready state

Question 8

SoFa (def. + expl.)

Answer 8

State of failure: system is no longer functionable.

Question 9

Factors influencing the functionability profile

Answer 9

• Inherent characteristics of the system (RMS)

- Utilization characteristics

Question 10

Inherent characteristics of the system (RMS)

Answer 10

• Frequency of occurrence of failures (Reliability)
• Complexity of the restoration tasks (Maintainability)
• Ease of support of the tasks (Supportability)

Question 11

Utilization characteristics

Answer 11

• Operational scenario
• Maintenance policy
• Logistics function

Question 12

Availability (def.)

Answer 12

The probability that the system will be available and capable of performing its intended function at any random point in time.

Function of RMS

Question 13

Availability (metric)

Answer 13

= time in sofu / total time in utilization

Question 14

Maintainability theory (def.)

Answer 14

The scientific discipline studies the tasks that need to be performed to maintain the functionability of a system.

Question 15

Maintainability (def.)

Answer 15

The inherent characteristic of an item related to its ability to be restored when the specified maintenance task is performed as required.

Question 16

Maintainability (metric)

Answer 16

Sofa / (# failure events)

Question 17

Maintenance tasks (3x + example)

Answer 17

• Corrective: restore the functionability of the system after the loss of the function or performance.
• Hard-time preventive: reduce the probability of failure.
• Condition based: occur due to the monitoring of a change in condition.

Question 18

Objective of hard-time preventive maintenance tasks

Answer 18

Happens before a transition to sofa in order to reduce:

• Maintenance cost
• Prob of failure

Question 19

Types of checks w/ frequencyand duration of check

Answer 19

Major check (D), 18000 hrs, 25-30 days
Inter check (C), 4500 hrs, 9 days
Service check (B), 800-3000 hrs, 1-2 days
Ramp check (A), 125-500 hrs, 0.3 days

Question 20

Reliability (def.)

Answer 20

The inherent characteristic of a system related to its ability to maintain functionability used as specified.

Question 21

(M)TTF (abbr.)

Answer 21

(Mean) Time To Failure

Question 22

MTBF (abbr.)

Answer 22

Meant Time Between Failures

Question 23

MTBF (def.)

Answer 23

Measures only the time a repairable system is available and operating (so not a measure for non-repairable systems)

Question 24

Supportability (def.)

Answer 24

The inherent characteristic of an item related to its ability to be supported by the required resources for the execution of the specified maintenance tasks.

Question 25

Factors influencing supportability (3x)

Answer 25

Supplies required
Accessibility
Maintenance work

Question 26

Factors influencing reliability (3x)

Answer 26

Inherent: strength and condition of raw materials, manufacturing, quality control, initial packaging/ transportation/storage.
Environmental: temp, humid, salinity, vibrations, radiation, terrain, etc.
Operational: loading, # of cycles, the intensity of use, freq of use, misuse, and storage conditions.