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Research Article
Advances in Mechanical Engineering
2017, Vol. 9(4) 1–9
ÓThe Author(s) 2017
DOI: 10.1177/1687814017697893
journals.sagepub.com/home/ade
A new test study on measurement of
bias aircraft tire blowout
Yaohua Wang
1
, Guofeng Liu
1
and Zhibin Wu
2
Abstract
Failure of aircraft tires is a common cause for aviation accidents, whose results range from abnormal taking-off and land-
ing process to fatal air crashes. Those consequences should not be neglected; hence, an authentication of airworthiness
is necessary for the development of new aircrafts. Failure of aircraft tires can be caused by numerous factors and can be
categorized into various modes. The related tests are of great significance for newly developed aircrafts to pass the
authentication system. However, failures of aircraft tires can be unexpected, drastic, and extremely dangerous, which
adds to the difficulties in tests. Besides, the test methods used currently contain insurmountable defects. In this article, a
new test apparatus is developed to research the blowout of bias aircraft tires, which is in accordance with the Joint
Aviation Authorities standard, and a test scheme is designed. With the jet flow field formed by the test apparatus and
the comparison between simulation results and test data, the reliability of the test apparatus is proved. Ergo, a new test
method for the airworthiness authentication of tire failures has been developed.
Keywords
Failures of aircraft tires, airworthiness authentication, test apparatus, jet blast field, fluid simulation
Date received: 8 March 2016; accepted: 10 February 2017
Academic Editor: David R Salgado
Introduction
Aircraft tires are important devices which complete the
take-off and landing process of planes. Meanwhile, the
tires work under heavy loads, harsh functioning envir-
onments, and great variations of tire pressure, which
subject them to blowouts. There are complex factors
that could result in aircraft tire blowouts, among which
manufacturing defects and misuse are the main
causes.
1,2
A majority of aviation accidents are caused
by failures of aircraft tires, and this has drawn the pub-
lic’s attention. To make tires more secure and reliable,
agencies like Joint Aviation Authorities (JAA) and
European Aviation Safety Agency (EASA) request that
blowout tests be run on the key parts in the main gear
cabin, which aims to access the dynamic response char-
acteristics of these parts. Till now, main relative stan-
dards are the JAA Temporary Guidance Material,
TGM/25/8 (issue 2) Wheel and Tire Failure Model by
JAA,
3
and the 2013-02 Notice of Proposed Amendment
(NPA) by EASA,
4
both of which have elaborate rules
on failure modes which occur in cruise or the take-off
and landing process. Hence, blowout tests have to be
carried out according to different failure modes.
Among the aircraft tire failure modes given by stan-
dards of JAA and NPA, special attention should be
paid to the mode of tire burst pressure effect. This very
mode happens after the plane takes off when the air-
craft tires are back in the main gear cabin, and it is
often caused by undiscovered damages in the tires.
When the aircraft is cruising high in the sky, due to an
1
College of Field Engineering, PLA University of Science and Technology,
Nanjing, China
2
Jiangsu Hong Mao Heavy Industry Co., Ltd, Yixing, China
Corresponding author:
Guofeng Liu, College of Field Engineering, PLA University of Science and
Technology, Nanjing 21007, China.
Email: lgf801226@163.com
Creative Commons CC-BY: This article is distributed under the terms of the Creative Commons Attribution 4.0 License
(http://www.creativecommons.org/licenses/by/4.0/) which permits any use, reproduction and distribution of the work without
further permission provided the original work is attributed as specified on the SAGE and Open Access pages (https://us.sagepub.com/en-us/nam/
open-access-at-sage).
increase in the pressure differential between the inside
and outside, the aircraft tires are prone to blowout.
Today, aircraft tires mainly consist of bias tires and
radial tires with different shapes of flow field nozzles
and tire burst pressure effect mode irrespectively.
5
The
tire burst pressure effect mode when a bias tire bursts is
shown as Figure 1. These two criteria stipulate that this
model merely concentrates on air-jet pressure effect
while ignoring forced outward fragments when a tire
blows out.
3,4
Test studies of tire blowouts are of great significance
to not only airworthiness authentication and security in
flying but also the tire industry.
6
Correlational studies
have already been conducted by all the major tire man-
ufacturers worldwide; however, it is, to a certain degree,
especially professional, technically difficult, expensive,
risky, and hard to get into. In the test by Megan,
polished B-52 and F-16 were first fixed and tire burst
tests were carried out. The pressure data were obtained
via sensors placed around tires 900 mm away.
7
A regional jet is utilized in the tests, which is inde-
pendently designed and manufactured by China accord-
ing to the international standards of airworthiness. The
security test of the key parts in the main gear cabin was
carried out by Michelin and Cie and the process is
shown in Figure 2. In the test, Michelin and Cie, first,
determined grinding areas and depth by experience; sec-
ond, fixed the polished tire on the test table; third,
inflated the tire to 1.825MPa, then fixed a resistance
wire on the central part of grinding surface, and finally,
the ohmic heating resistance wire burned out ungrind-
ing cord threads to simulate tire blowout. Meanwhile,
the collection of pressure signals would be done by the
sensors as shown in Figure 2.
8
As seen in Figure 2, only dynamic pressure data
more than 500 mm (20 inches) away from the flow field
nozzle were collected in the test. However, key parts in
the main gear cabin of this plane were all within
500 mm from the nozzle, and therefore, dynamic
response of the plane cannot be analyzed directly with
the pressure data obtained during this test. Meanwhile,
the blowout jet field produced in this test varies greatly
from the model depicted in Figure 1 in terms of nozzle
shape, size, and the shape of jet flow.
In conclusion, there is no method to accurately mea-
sure the jet blast field produced when an aircraft tire
blows out, and its main reasons are listed as follows:
1. The blowout of tire is intense. The reproducibil-
ity of the test data is low as a consequence of
uncertain size and position of flow field nozzle
and yet a relatively fixed layout of sensors.
2. Fragments of different shapes flying at a differ-
ent speed are inevitably forced out in the
process of aircraft tire blowout, directly impact-
ing and damaging proximal sensors, and there-
fore, pressure data within 500 mm cannot be
collected.
To solve the above problems, in this article, a set of
test apparatus combing deflagration system with plate
values is designed according to the standards of JAA
and NPA, and jet field close to the nozzle is measured.
Test study
Test apparatus
The designing idea is to create a round hole on the sur-
face of aircraft tire to simulate the blowout nozzle
according to the size shown in Figure 1. First, the tire
body is fixed to the apparatus tightly and the blowout
nozzle is sealed with a pair of plate valves. When the
tire is charged to working pressure, deflagration power
system is connected to plate valves to turn on the plate
valves synchronously to simulate the jet field from the
blowout of bias tires realistically. Its physical maps and
three-dimensional (3D) diagrams are shown in Figure
3. This set can efficiently avoid the shortcomings of
previous tests:
Figure 1. A recommended model for tire burst pressure effect
mode of bias tires blowout: (a) JAA TGM/25/8 and (b) EASA
NPA 2013-02.
2Advances in Mechanical Engineering
1. The jet flow field model prescribed in JAA and
EASA standards is realized with the proposed
apparatus, which increases the reliability of the
dynamic analysis of the main gear cabin
accessories.
2. No tire fragments are produced in the tests,
which enables the closer locations of sensors so
that dynamic pressure data within 500 mm could
be obtained. This is of great significance to
exploring the pressure distribution rules of the
jet field and further studies.
3. The flow field nozzle produced with this set of
equipment is fixed, which facilitates the test and
allows a stable flow field, making it convenient
to repeat the experiment.
Structure and working principles
Deflagration dynamical system
The deflagration dynamical system is mainly comprised
of a piston cylinder (No. 11 in Figure 4), a piston (No.
12 in Figure 4), gunpowder (No. 10 in Figure 4), and
so on. Both the standards of JAA and NPA do not reg-
ulate the exact time when the blowout nozzle should be
turned on. In order to stimulate the blowout process,
the opening time of the plate valve (No. 7 in Figure 4)
is supposed to resemble that of the real blowout.
According to the blowout process recorded by a high-
speed camera, the opening time of blowout nozzle is
less than 5 ms under all circumstances. As shown in
Figure 1(a), the diameter of the jet flow nozzle is
80 mm, and it takes about 100 ms for solenoid plate
valves to be turned on whereas the time needed for
Figure 2. A test diagram of tire blowout of Michelin and Cie: (a) photos of blowout spot and jet blast field and (b) layout of sensors.
Figure 3. Diagrams of test apparatus: (a) physical map of test
apparatus and (b) 3D map of test apparatus.
Figure 4. An assembly diagram of test apparatus.
Wang et al. 3
pneumatic plate valves being longer, therefore, neither
solenoid valves nor pneumatic valves can meet the time
requirement. The turning-on of the nozzle in this appa-
ratus is powered by high-pressure air let out in the pro-
cess of high-performance gunpowder detonation. To
overcome the reactive force of the explosion, a symme-
trical plate valve structure is utilized. However, the syn-
chronism problem has to be solved in the proposed
design. For the purpose of satisfying both opening time
and synchronism requirements, various gunpowders
are tested, and an electric detonator is innovatively
employed simultaneously, which makes two symmetri-
cal plate valves opened at the same time. As the test
results show, it only takes about 3.8 ms to turn on plate
valves. And there is a time synchronization error for
the operating the dynamical system of less than 0.3 ms
for the whole process of turning-on.
Sealing system
This type of aircraft tire has a tire pressure of 1.73 MPa,
which requires an extremely high sealing standard to
simulate the blowout process. The sealing system of this
apparatus is comprised of the seal between the appara-
tus and the tire body as well as the seal of plate valve’s
structure. The seal between the elastomer and the rigid
body is a worldwide problem. In order to reach a reli-
able seal between the apparatus and the round hole on
the surface of tire (No. 2 in Figure 4), a bowl-shaped
clamping ring (No. 5 in Figure 4) is designed in this arti-
cle, the structure of which is shown in Figure 5. To seal
the apparatus and tire effectively, the bolt and tire body
are sticked together with AB glue for aviation and then
bowl-shaped clamping ring is employed to compress
them. The seal of plate valve’s structure is completed by
compressing the seal ring (shown in Figure 6) at the
joint and lower parts of the plate valves (No. 6 and No.
8 in Figure 4). The results show that this hermetic
method satisfies the design needs which require at least
five times of repeated tests.
Test system
The test apparatus consists mainly of pressure sensors,
a DH5927 dynamic high-speed data collecting instru-
ment, a bearing and a bracket (as shown in Figure 7),
and so on. To ensure the measurement of the jet field is
accurate enough, a layout scheme of sensors is pro-
posed in this article as follows:
1. Employ thin-polished sensor bearings so that
the potential influences from the array of sen-
sors to the jet field could be reduced.
2. Dispose all sensors in a 3D way so that the jet
field test could be run in three dimensions.
3. Try to match the test spots with key parts in the
main gearing cabin in the following tests.
4. Alternatively, test the spots multiple times where
they could possibly interfere with each other.
Figure 5. Bowl-shaped clamping ring.
Figure 6. The seal ring for plate valves.
4Advances in Mechanical Engineering
5. Sensors near the boundaries are adjustable so that
boundary values of the jet field could be exact.
Test scheme
1. According to the requests for blowout spots
from the aircraft tire blowout test, a round
through-hole should be cut at a specified place
on the tire surface. The size of the hole should
follow the principles of fluid dynamics, the
actual sizes of the tire, and the JAA standard.
The water jet cutter is harnessed for processing
the jet hole and the bolt hole, and the method of
milling is employed for processing the counter-
bores for the sealing rings and the bowl-shaped
clamping rings. Both techniques are used for the
sake of leakproofness and in order that walls of
holes could be free from any damage possible.
2. Metal boards (No. 1 in Figure 4) should be
closely connected to the body of the tire (No. 2
in Figure 4) with bolts. To ensure the airtight-
ness, the bowl-shaped clamping rings mentioned
above and the AB glue for aviation are utilized.
The test apparatus is tightly attached to the metal
board (No. 4 in Figure 4) via whorl threads.
3. As shown in Figure 8, the apparatus is fixed on
the test bearing, and the array of sensors and the
data collecting system are all laid out as planned.
4. Set the electric detonator and gunpowder in the
piston body of No. 12 shown in Figure 4.
5. Use the adjusting board (No. 13 in Figure 4),
which is fixed at the bottom of the piston cylin-
der (No. 11 in Figure 4), and rotate simultane-
ously the two adjusting bolts (No. 14 in Figure
4) so that the two plate valves (No. 7 in Figure
4) can connect and seal with each other. This
sealing hereby could withstand a pressure of no
less than 4 MPa. The airtightness of the flow
field nozzle during the tire pressurizing process
is realized via the sealing system.
6. Pressurize the aircraft tire till 0.5 MPa, and
remove No.13 and No.14 shown in Figure 4,
then, continue to pressurize till the pressure
reaches 1.75–1.76 MPa.
7. Ignite the gunpowder block with the electric
detonator (No. 10 in Figure 4). With the push
from the gunpowder, the piston (No. 12 in
Figure 12), together with the plate valves, moves
to the opposite direction in the slideway, thus
turning-on the jet filed nozzle to simulate tire
burst. Meanwhile, data could be collected via
the test systems for further references.
Test results and analysis
Figure 9 shows the time–overpressure relation at differ-
ent position. All the pressure values given below are the
difference between real pressure and standard atmo-
spheric pressure. The data obtained at S2, S3, S4, S5,
S6, and S7 are depicted in Figure 7, which represent the
relation between time and overpressure.
Figure 7. The layout of sensors: (a) the sensor distribution in
real application and (b) the schematic diagram of sensor
distribution.
Figure 8. Apparatus of the jet blast field test system.
Wang et al. 5
It can be concluded from Figure 7 that, despite the
fact that S2, S3, and S4 share a same distance to the
center axis of the detonation, the maximum overpres-
sure value is reached at S2. S3 and S4 are symmetric
from the center axis, and ergo has a similar overpres-
sure maximum value as well as a time–overpressure
relation diagram. Same theory is also applied to S5, S6,
and S7.
Since the ultimate goal of the research is to find out
the influence of jet flow upon the security of key parts
in the cabin, the focus of the research should be drawn
to the maximum overpressure at the axis. The analysis
of the changes of overpressure condition and time can
be used as reference for following tests. The tested val-
ues at different spots along the axis are listed in
Table 1.
According to the statistics from the selected test
points, the overpressure peak value decreases appar-
ently as distance increases. S23 is 537 mm from the
detonation axis and has a similar peak value with the
tested value at a distance of 20 inches (508 mm) by
Michelin and Cie, which indicates that the apparatus in
this article can satisfy the design needs well.
From Figure 9 and Table 1, it can be concluded that
the jet flow field created by this apparatus attenuates as
the distance from axis increases. And at the same dis-
tance, the value at inner side is larger than that at outer
side. The above conclusions are in accordance with the
classic theories of jet flow field of tire blowout. It is also
proved that this apparatus can develop a cone jet flow
field stipulated by standards of JAA and NPA. In addi-
tion, results from multiple tests show that overpressure
at all spots is less than the maximum allowable value,
while overpressure in previous tests varies drastically.
Therefore, it is proven that the proposed apparatus can
be used to create stable jet flow field.
The standard by NPA is based on the foundations
of that by JAA. In comparison to the latter, the former
has more conservative standards on fragment sizes,
velocity, and so on, yet the two standards specified dif-
ferent cone angles under the tire burst pressure effect
mode. According to the standard by JAA, the cone
angle 2aequals 36°, whereas in terms of the NPA stan-
dard, that is 18°. Time–overpressure relation diagram is
plotted in Figure 10 as J2. The included angle between
J2 and the vertex of the cone angle is 18.7°. It has been
confirmed through tests that the vertex angle is 36°–38°
approximately, which shows, by contrast, the standard
of JAA corresponds more to reality than that of NPA
does.
In this article, the commercial software FLUENT is
used to stimulate the blowout process. The blowout
simulation is shown in Figure 11.
Figure 12 depicts the relation between distance in
axial direction and overpressure when the nozzle
becomes the biggest. It is obvious from the figure that
the pressure at the axis matches those peak values back
in Table 1. For further research, S5, which is 142 mm
from the nozzle, is selected in our research. Figure 13
gives the overpressure diagram at the distance of
142 mm in the radial direction.
The time–overpressure relation diagram which is
144 mm from the detonation axis by FLUENT is
shown in Figure 14. For comparison, Figures 14 and 9
are redrawn as Figure 15. As is observed from
Figure 15, the simulation result agrees well with tested
result, which proves the reliability of the proposed
apparatus.
Conclusion
Failure of aircraft tires is a common cause for
aviation accidents. Therefore, it is of vital significance
to conduct an authentication of dynamic responses of
key parts in the main gear cabin. A new set of test
apparatus has been established for stimulating the
blowout of aircraft bias tires, and the test process has
accordingly been designed. After comparing the experi-
ment data of Michelin and Cie and the simulation data,
it is proved that bias aircraft tire blowouts can be simu-
lated. The statistics within 500 mm from the jet flow
nozzle have been collected for further research. In
designing the apparatus, the following three aspects are
researched:
Table 1. Overpressure peak value at the axis.
Test spot Distance from the
sector axis (mm)
Distance from the
detonation axis (mm)
Angle (°) Peak value of
overpressure (MPa)
S1 224.4 72 0 1.16
S2 259.4 107 0 0.86
S5 294.4 142 0 0.68
S8 329.4 177 0 0.59
S11 364.4 212 0 0.51
S14 399.4 247 0 0.35
S17 489.4 337 0 0.31
S23 689.4 537 0 0.20
6Advances in Mechanical Engineering
1. To simulate the real aircraft tire blowout pro-
cess, a new detonation-powered device has been
established. An electric detonator lighting
method has been put forward so that the plate
valve opening time could resemble that of the
tire blowout, which makes opening time and
synchronism time less than 5 and 0.3 ms,
respectively.
2. To satisfy the leakproofness needs of the device,
explorations into the airtightness of elastomer
and stiffener have been made, and several test
methods are designed. Eventually, the bowl-
shaped clamping ring with aviation AB glue
way is adopted, which is in line with the
standards.
3. To overcome the drawbacks of previous test
methods, sensors in the proposed method are
located at different places in 3D space. The
pressure distribution within 500 mm of the tire
leakage is obtained, which is important for the
Figure 9. Six time–overpressure relation diagram.
Wang et al. 7
Figure 10. J2 time–overpressure relation diagram.
Figure 11. Sketch map of the transverse section of the
simulation.
Figure 12. The distribution of the overpressure in the axial
direction.
Figure 13. The distribution of the overpressure at 142 mm in
the radial direction.
Figure 14. S5 time–overpressure relation diagram (simulation).
8Advances in Mechanical Engineering
analysis of dynamic response of the key parts in
the main gear cabin. In addition, the shape of
jet field is investigated.
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with
respect to the research, authorship, and/or publication of this
article.
Funding
The author(s) received no financial support for the research,
authorship, and/or publication of this article.
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Figure 15. S5 contrasts between simulation and test.
Wang et al. 9
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