1
Investigation of the Dynamic Relationship between Oil Temperature and
Bearing Gearbox Condition Indicator Values for the Bell 407
Helicopter Based on Cointegration Analysis
Oumayma Babay
1
, Lotfi Saidi1
1,2,4
, Eric Bechhofer
3
,
Mohamed Benbouzid
4
1
Department of Electronics and Computer Engineering, Higher School of Sciences and Technology of Hammam Sousse,
University of Sousse, Sousse 4011, Tunisia
Oumaymababay2000@gmail.com
2
ENSIT- Laboratory of Signal Image and Energy Mastery (SIME), University of Tunis, LR 13ES03, Tunis 1008, Tunisia;
lotfi.saidi@ieee.org
3
Green Power Monitoring Systems, LLC, VT 05753, USA
eric@gpms-vt.com
4
University of Brest, UMR CNRS 6027 IRDL, 29238 Brest, France
mohamed.benbouzid@univ-brest.fr
ABSTRACT
The primary objective of this study is to investigate the
dynamic relationship between oil temperature and the
Bearing Gearbox Condition Indicator (BGCI) values of the
Bell 407 helicopter. To achieve this goal, we employ robust
econometric tools, such as unit root tests, cointegration tests,
and Autoregressive Distributed Lag (ARDL) models for
both, long-run and short-run estimates. Our findings indicate
that variable temperature tends to converge to its long-run
equilibrium path in response to changes in other variables.
The results of the ARDL analysis confirm that spectral
kurtosis, inner race, cage, and ball energy significantly
contribute to the increase in temperature. Furthermore, we
use the impulse response function (IRF) to trace the dynamic
response paths of shocks to the system. The identification of
a cointegrating relationship between oil temperature and
BGCI values suggests a practical and significant connection
that can potentially be used to predict hazardous changes in
oil temperature using BGCI values, which is an important
implication for enhancing the safety and reliability of
helicopter operations.
This study presents a promising direction for condition
monitoring (CM) in rotating aircraft machinery, emphasizing
the potential of integrating temperature data to simplify the
diagnostic process while still achieving reliable results.
KEYWORDS: Bearing gearbox; Cointegration; condition
monitoring (CM), Condition indicator (CI); Oil temperature
1. INTRODUCTION
The relationship between oil temperature and BGCI values is
crucial for assessing the health of helicopter main gearboxes.
Monitoring systems like Health Usage Monitoring Systems
(HUMS), utilize vibration signatures to detect faults (Tabrizi
et al., 2017, Zhang et al., 2012). Oil temperature is a key
parameter affecting gearbox health (Huang et al., 2020). Data
analysis and artificial intelligence techniques are employed
to monitor the lubrication and cooling systems of modern
helicopters (Li et al., 2019). Additionally, the vibration
signatures of damaged components, like bearings, are used as
condition indicators, which can vary based on the system
design and operating conditions (Wei et al., 2022) and oil
temperature. The use of advanced signal processing tools can
help extract bearing fault signatures from vibration signals,
thereby enhancing the fault detection capability. Overall,
integrating oil temperature monitoring and bearing condition
indicators can provide a comprehensive approach for
ensuring the safety and reliability of helicopter gearboxes.
In Tabrizi et al. (2017), proposed a novel combined method
for fault detection in rolling bearings based on cointegration
for the development of fault features that are sensitive to the
presence of defects but insensitive to changes in operational
conditions.
According to Zhang et al. (2012), the root cause of high oil
temperatures is improper lubricating oil selection and serious
solid particle pollution. Oil analysis techniques are also
applied to monitor the working conditions of oil, to prevent
mechanical failure, and to extend machine life.
Oumayma Babay et al. This is an open-
access article distributed under the
terms of the Creative Commons Attribution
3.0 United States License,
which permits unrestricted use, distribution, and reproduction in any
medium, provided the original author and source are credited.
