11
Ministry of education and science of Ukraine
National Aviation University
Course work
on the discipline
Diagnostics of aircraft state
`Working out of the search algorithm of failures of Air Conditioning System of TU-154'
the work is performed by
the student of 505 FLA
D. Zhuravel
the work is checked by:
Y. A. Sapeljuk
Kyiv 2009
Component name
Diagnosis (Di)
Malfunction features
(Xj)
Number of diagnosis appearance
(n)
Probability of diagnosis appearance
(Qi)
X1
X2
X3
X4
X5
AAHE
D1
+
4
0.25
D2
5
0.31
ACM
D3
3
0. 19
NSD
D4
1
0.06
Pipelines
D5
2
0.13
Check valve
D6
*
**
D12
D 15
D36
Abbreviations and reference designation:
Diagnoses:
D1 - incorrect tubes` installation
D2 - non-pressurized internal cavity
D3 - weakened fitting
D4 - damage of a housing
D5 - non-pressurized part of line
D6 - wrong installation
* - number of diagnoses that are controlled by this sign
** - diagnoses, which are controlled
Signs of failures:
X1 - raised temperature in pipeline
X2 - unsatisfactory pressurization of right mainline
X3 - unusual noise in the cabin
X4 - no air supply to ACS
X5 - fumes in passenger cabin
Evaluation of probability of diagnoses appearance is calculated by the formula:
, , (1)
where ni - number of cases of appearance of і diagnose; N - number of all diagnoses of system aggregates.
In the table 1 there are written aggregates' names, their possible diagnoses, and their signs. If some sign from the totality Xj corresponds to diagnose Di on the crossing of their columns we put the sign (+), that shows stochastic relation between them. Presence of relations between diagnoses and signs is defined by the making of engineering analysis of work of the system and its aggregates with taking into account possibilities of system control, which is used on the given type of aircraft. Diagnoses are chosen by statistic data that are collected on operational enterprises in the process of operation of aviation technique.
For functional systems of the aircraft it is typical the appearance simultaneously several signs during failures appearance, that is underlined presence of several signs (+) in the columns of the table 1.
Data analysis attests that some signs may be shown in appearance of different failures and defects of aggregates, that's why in penultimate line there are written number of diagnoses, which are controlled by each sign. If some sign is shown in appearance of several diagnoses, then its appearance may be caused by appearance of either one diagnose or another one, and also when diagnoses appear together. That's why in the last line of the table there are written possible combinations of the diagnoses. In spite of that during analysis of functional systems of the aircraft it is considered that simultaneous appearance of several types of the failures of aggregates, but from theoretical point of view accounting uncertainty of information about the state of aggregates, in the case of appearance of such situation it is necessary to take into account this possibility. For usage of mathematical apparatus of theory of information it is necessary to define values of probabilities qi of appearance of this or that diagnose. For their calculation in penultimate column of the table there are written number of cases of appearance of each diagnose by statistical data, which are collected for some period of AT operation. It is evident that it is not possible to calculate probability of diagnose appearance, but it is possible to get their evaluation. Control of one or several parameters (signs) of the system, which is called check, gives information j about presence of aggregate diagnose. Quantity of information, accounting that we consider dichotomy, is evaluated as difference between level of system state uncertainty before H (S) and after check H (S/nj):
Страницы: 1, 2