Cost Analysis of Preventive Maintenance for Commercial Aircraft
Based on System Simulation
Pu Li
a
Shanghai Aircraft Design and Research Institute, China
Keywords: Preventive Maintenance, System Simulation, Cost Analysis.
Abstract: Economy plays an important role in the research and development of commercial aircraft. Under the premise
of ensuring aircraft performance and safety, manufacturers continue to pursue cost reduction. With the goal
of reducing the maintenance cost of commercial aircraft and the aircraft preventive maintenance process as
the main object, this research applies the system dynamics principle to analyze the dynamic characteristics of
aircraft maintenance costs, analyze the laws of the occurrence and development of aircraft maintenance costs,
establish a general model and conduct simulation analysis, so as to provide a way for the prediction, analysis
and control of commercial aircraft maintenance costs, and also to control the full life cycle cost of commercial
aircraft Provide effective means to meet the economic objectives of commercial aircraft.
1 INTRODUCTION
In the process of developing commercial aircraft, all
countries in the world have put forward the
requirements of safety, comfort, environmental
protection and economy without exception. Among
them, safety, comfort and environmental protection
are no longer difficult problems in technology.
Therefore, aircraft manufacturers have put economy
in an important position when developing new
generation aircraft. In short, on the premise of
ensuring aircraft performance, safety and reliability,
It has the lowest R&D cost, manufacturing cost and
operating cost.
However, some aircraft manufacturers often
focus on R&D costs and manufacturing costs for their
own interests and other factors, ignoring the overall
consideration of operating costs. As we all know,
R&D and design determine more than 50% of the cost
of products, and the proportion of aircraft products
will be higher (Pu 2014). Therefore, once the
products are finalized, the later manufacturing costs
and operating costs will be basically fixed, and it is
difficult to reduce the space, which will bring great
maintenance cost pressure to airlines after removing
variable costs such as fuel in later operations. For
example, the annual aircraft maintenance cost of the
a
https://orcid.org/0000-0002-4850-1686
US military has reached more than 20 billion US
dollars. Since the 1980s, this cost has been close to
the sum of its research and development costs and
procurement costs, accounting for 14.2% of the total
defense expenditure. At present, it is difficult to
obtain maintenance cost related data of major airlines
in the world, but the situation is generally similar.
With the goal of reducing the maintenance cost of
commercial aircraft and the aircraft preventive
maintenance process as the main object, this research
applies the system dynamics principle to analyze the
dynamic characteristics of aircraft maintenance costs,
analyze the laws of the occurrence and development
of aircraft maintenance costs, establish a general
model and conduct simulation analysis, so as to
provide a way for the prediction, analysis and control
of commercial aircraft maintenance costs, and also to
control the full life cycle cost of commercial aircraft
Provide effective means to meet the economic
objectives of commercial aircraft.
2 CAUSALITY ANALYSIS
System Dynamics (SD) is a discipline that closely
combines system engineering theory with computer
simulation to study the structure and behavior of
280
Li, P.
Cost Analysis of Preventive Maintenance for Commercial Aircraft Based on System Simulation.
DOI: 10.5220/0012073300003624
In Proceedings of the 2nd International Conference on Public Management and Big Data Analysis (PMBDA 2022), pages 280-284
ISBN: 978-989-758-658-3
Copyright
c
2023 by SCITEPRESS – Science and Technology Publications, Lda. Under CC license (CC BY-NC-ND 4.0)
system feedback. It absorbs the essence of chaos
theory, information theory, cybernetics, and
topology, and believes that the behavior mode and
characteristics of a system mainly depend on its
internal structure (Li 2006). Only by taking the whole
system as a feedback system can correct conclusions
be drawn. In 1999, the US military C-17 project
office first noticed that the system dynamics method
can be used in cost estimation, and the cost of
different activities under different circumstances can
be well expected.
Preventive Maintenance described in this study is
all activities to prevent aircraft failures or serious
consequences caused by failures and keep them in a
specified state. These activities include: wiping,
lubrication, adjustment, inspection, regular repair and
replacement, etc. The purpose is to find and eliminate
potential faults, which have some characteristics such
as complexity, integrity, connectivity, dynamics,
stability, etc. (Figure 1). From the perspective of cost,
the increase of preventive maintenance activities will
definitely lead to the increase of preventive
maintenance cost, and will also reduce the cost of
corrective maintenance, which will also have a
certain impact on spare parts storage costs and
maintenance personnel training costs. The theory and
method of system dynamics can solve this problem
well.
Characteristics of preventive
maintenance elements
Complexity
Wholeness
Relational
Dynamicity
Constancy
Tasks
Object
Elements of Maintenance
System are Complex
Relationship Between
Elements is Complex
1+1>2
Interrelation and Interaction
Aggregation of Processes
Establish and Maintain a Steady State
Figure 1: Characteristics of Preventive Maintenance Elements.
Preventive maintenance is generally divided into
four forms: regular maintenance, condition based
maintenance, advance maintenance, and failure
inspection, which will consume corresponding
resources and may be different from each other (Gan
2005). Therefore, in order to accurately estimate the
preventive maintenance cost, it is necessary to first
understand the preventive maintenance support
activities of similar commercial aircraft models
through the maintenance plan, then model the
maintenance support activities of newly developed
models, and apply the system dynamics method to
evaluate the maintenance support cost of the whole
life cycle. The influencing factors of preventive
maintenance cost are shown in Figure 2.
Preventive
Maintenance Cost
Number of Preventive
Maintenance
Number of Times
Single Preventive
Maintenance Cost
Life Time
Purchase Cost
Number of
Aircra ft in a Fleet
Preventive
Maintenance Cost
of Repairable Life
Parts
Repairable Non
Life Parts
Number of All
Parts of a Single
Aircraft
Non Repairable
Parts
Instantaneous
Failure Rate
Instantaneous
Failure Rate
Instantaneous
Availability
Number of Preventive
Maintenance
Replacement Cost
Single Preventive
Maintenance Cost
Instantaneous
Failure Rate
Instantaneous
Availability
Figure 2: Influencing Factors of Preventive Maintenance Cost.
Causality analysis is very important to establish
an accurate and reasonable system dynamics model
(Li 2006). The causal loop diagram (CLD) is an
important tool to represent the feedback structure of
the system. It contains multiple variables, and the
variables are connected by arrows indicating the
causal relationship. The causal loop of the preventive
maintenance cost influencing factors listed in Figure
2 is shown in Figure 3. The NRP means Non
Repairable Parts, RLP means Repairable Life Parts
Cost Analysis of Preventive Maintenance for Commercial Aircraft Based on System Simulation
281
and RNLP means Repairable Non life Parts of the
aircraft are all maintained in a fixed time interval. In
the early stage of aircraft operation, the failure rate is
relatively low, and the time interval between
scheduled maintenance can be relatively long; After
a long period of aircraft operation, with aging and
frequent failures, the preventive maintenance interval
should be reduced. In the figure, there are 7 stocks
and 7 flows, a constant number of organic groups of
aircraft, preventive maintenance costs for single
repairable life parts, etc.
Preventive
Maintenance Cost
Number of Preventive
Maintenance of RNLP
Number of Preventive
Maintenance of NRP
Single Preventive
Maintenance Cost
of RNLP
Life Time
of RLP
Purchase Cost
of NRP
Number of
Aircra ft in a Fleet
Preventive
Maintenanc e
Cost of RLP
Preventive
Maintenance
Cost of RN LP
Number of All
Parts of a
Single Aircraft
Preventive
Maintenance
Cost of NRP
Failure Rate
of RNLP
Instantaneous
Failure Rate
of RNLP
Repairable
Maintenance
Times of RLP
Replacement
Cost of RLP
Instantaneous Failure
Rate of RLP
Failure Rate
of RLP
Number of Preventive
Maintenance of RLP
Average
Availability of
RLP
Instantaneous
Failure Rate
of NRP
Replacement
Times of NRP
Average
Availability
of RNLP
Failure Rate
of NRP
Number of
Corrective
Maintenance of
RNLP
Single
Maintenance
Cost of RLP
-
+
+
+
++
+
+
+
+
+
+
+
+
+
-
-
-
-
-
-
-
-
-
-
+
Figure 3. Cause and Effect Loop Diagram of Preventive
Maintenance Cost.
3 CASES AND MODELS
The relevant boundary conditions in this study are
as follows:
All expenses incurred are present value,
without considering inflation;
The fleet has 24 single channel trunk aircrafts,
each of which has a service life of 20 years,
and each aircraft has an average annual flight
time of 300 hours;
The preventive maintenance of the fleet only
considers scheduled maintenance, and the
time interval will be adjusted as the aircraft
ages; Corrective maintenance only includes
repair and replacement of parts; The storage
management cost of spare parts is only
affected by the number of spare parts, that is,
the storage cost of each spare part is a fixed
value; The annual personnel training cost is
fixed.
Each aircraft has 100000 parts, and there are
only three types of parts: 60000 repairable
parts with life, 20000 repairable parts without
life, and 20000 non repairable parts. The
failure rate of all parts is the same. The cost of
a single repair is a fixed value, and the cost of
tools/facilities for inspection and repair is also
a fixed value.
The field maintenance rate of aircraft fault
parts is a fixed value.
When a component fails, the improvement of
reliability after repair or replacement is
considered as the improvement of the
reliability of the original component and the
continuation of the original component, but
the instantaneous failure rate is reduced.
Other detailed assumptions will not be elaborated.
The preventive maintenance interval of the
aircraft is determined by the method of timing
maintenance interval T:
()
T
e
T
A
λ
λ
−
−= 1
1
Where
A
is the average availability, λ Is the
failure rate. In engineering calculation, the time
interval T is not easy to express, so the
T
e
λ
−
in the
formula is decomposed by Taylor:
()() ()
!!3!2!1
1
32
n
TTTT
e
n
T
λλλλ
λ
−
++
−
+
−
+
−
+=
−
Generally, according to the requirements of
airworthiness regulations, the failure rate of aircraft
components λ Are extremely low, even reaching 10-
9, so λ 3 It is small enough, so the first three terms of
T
e
λ
−
Taylor decomposition formula are
approximated:
()
()
()
λ
λλ
λλ
λ
A
T
TT
T
e
T
A
T
−
≈
−
+
−
+−≈−=
−
12
!2!1
11
1
1
1
2
Then, the DAPCA analysis model of RAND
Company in the United States is used for simulation
analysis and estimation, and the PRICE model is used
for parameter estimation and verification.
4 ANALYSIS OF SIMULATION
RESULTS
This study observed the change of maintenance
support cost by increasing the frequency of
preventive maintenance (Figures 4 and 5): when the
maintenance frequency increased by 10%, the
maintenance support cost decreased; When the
maintenance frequency is increased by more than
20%, the maintenance support cost will increase
significantly, which deviates from the traditional
understanding. Therefore, it is suggested that the
higher the preventive maintenance frequency is, the
better. A more reasonable cycle balance point needs
to be found.
PMBDA 2022 - International Conference on Public Management and Big Data Analysis
282
Figure 4: The Influence of Preventive Maintenance Frequency Change on Annual Maintenance Support Cost.
Figure 5: Influence of Preventive Maintenance Frequency Change on Total Life Cycle Cost.
Preventive Maintenance
Frequency Increased by
Total Maintenance & Support Cost of Life Cycle
Preventive Maintenance Frequency
Increased by
Cost Analysis of Preventive Maintenance for Commercial Aircraft Based on System Simulation
283
5 CONCLUSION
This study provides an effective method to solve the
cost estimation of aircraft maintenance support
system with complex influencing factors and long
duration by applying system dynamics. Through case
based simulation analysis, the impact of failure rate
and preventive maintenance rate on maintenance cost
is analyzed, and suggestions are put forward to reduce
the failure rate of aircraft parts and determine
reasonable preventive maintenance frequency, This
will enable the winning manufacturer to pay full
attention to the aircraft development process and take
effective measures to reduce the life cycle cost to
achieve the purpose of economy.
REFERENCES
C. D. Purvis. (2001). Estimating C-17 Operating and
Support Costs: Development of a System Dynamics
Model. R. Air force institute of technology.
Gan M., Kang J. (2005). Military Equipment Maintenance
Engineering. M. Beijing: National Defense Industry
Press.
Guo S. H. (2013). Thoughts on Effectively Controlling
Airline Aircraft Maintenance Costs. J. Foreign
Investment in China (20), 130-131.
Jia R. A., Hu L., Ding R. H., et al. (2001). System
Dynamics Simplified Flow Rate Basic Tree Entry
Model and Application. J. System Engineering Theory
and Practice, 21 (10): 137-144.
Jia R. A., Wu F., Xu N. S. (1998). SD flow rate basic tree
modeling method. J. System Engineering Theory and
Practice, 18 (6): 90-95.
Li Z. Q., Chen Y. L. (2011). Research on aircraft condition
based maintenance strategy and model. J. Aviation
Science and Technology, 2011 (03): 28-30.
Macia N. F. ， Thaler G. J. (2006). Dynamic System
Modeling and Control. M. Translated by Li Naiwen and
Sun Jianghong. Tsinghua University Press.
Pu L., Huang Z. D. (2014). System dynamics analysis of
aircraft maintenance training cost. J. Civil Aircraft
Design and Research, 4 (2): 48-50.
Shao G. X., Qiu J. C., Li Z. & Liu J. (2012). System
dynamics analysis of aviation equipment preventive
maintenance cost. J. Aerospace Science and
Technology (03), 65-70.
Xu Z. Y., Peng Y. M. (1997). Research on Life Cycle Cost
Analysis of Aeroengines. J. Aviation Systems
Engineering, 1997 (5): 39-44.
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