675. The Role of Systems Engineering Principles in Mass Properties Data Requirements

Paper

Abstract

Systems Engineering has been descrlbed as ‘an awareness of the allness of the problem.’ In instrumentation engineering a lack of this ‘awareness’ can seriously impare the validity of a measurement, and, in the reduction and evaluation of the measurement data the lack of ‘awareness’ can impare the validity of a measurement, and, in the reduction and evaluation of the mesaurement data the lack of ‘awareness’ can lead to a totally eerroneous conclusion.
The author’s interest and activity has been in the aerospace field for the past 18 years. This paper is based on actual experience in VTOL (XFY-1, Convair POGO-STICK), large aircraft (XC-99),, supersonic aircraft (F-102), liquid rockets, space boosters and spacecraft. The author’s intent is to present a foundation style, thought generating evaluation of the concepts of systems engineering as applied to instrumentation engineering in the aerospace field. Iterations of past problems and their solutions, by themselves, do not product a good understanding of the principles used in the solutions of the problems, and therefore will be used only in support of the main text.
In the engineering of instrumentaiton for a new vehicle, whether is be for land, sea, or air, an all-encompassing understanding of the environment in the immediate area of the transducer, as well as an understanding of the total environment sphere within which the instrumented vehicle will perform, is necessary to provide for a true and lucid interpretation and understanding of the test data.
An important link in the search for truth in data is a full understanding of transducer limitations and their effects upon the produced signal. When data on a given event are taken by two or more transducers of slightly different characteristics, the traces must be evaluated relative to the individual peculiarities of the specific transducer and its associated electronics.
The effective use of the precepts of system engineering, applicable to the instrumentation discipline, is a powerful tool with which the instrumenation design engineer (IDE) can produce designs and installations that are compatible and effective in the data environment, and of prime importance, satisfy the data requirement of the mass properties engineer. The use of the principles of systems engineering connotes the use of full and adequate communication between the MPE and the IDE, to the end that neither one says’yes, I understand’ until in truth he really does undersand. Nothing is more destructive to good and productive engineering than to not be honest in trying to understand one another.
An example could be in the field of dynamic balancing. The MPE must assure himself the the IDE is not in doubt as to the specific data needs of the requirement.
Dynamic balance data that are not fully understood by the requesting engineer has little value.
In addition to design and installation, calibration and data reduction/evaluation must also be ‘Systems Engineered’ or the value of the designs and installations is markedly diminished. The IDE and MPE must of necessity involve themselves in teh data reduction/evaluation activity so tht the reducing and particularly the evaluating personnel may adequately understand the meaning of the data and more properly be able to evaluate anomalies as either ‘datum’ or ‘non-datum’.
Practical assistance is offered through the medium of check lists of questions to be answered, by the group requiring the measurement, by the design and installing group, and the data reductions and evaluation group.
The check list for the requiring group allows them to set down the end results they seek and the use to which it will be put. This one point can be the key as to why the results obtained are often not the results requested. All too often the requesting group attempts to request a measurement based on their understanding of what type of instrumentation may be available. The results can be and have been disastrous. The MPE is well advised dto not try to design the measurement, but, only to request specific data.
The check list for the design gorup allows the designer to pinpoint potential problem areas.
The check list that the data reduction/evaluation group receives is completed by the designer, and contains information and pointers needed to correctly evaluate the provided data.