oSIST prEN 4888:2022
(Main)Aerospace Series - Commercial aircraft passenger seats - Reliability testing
Aerospace Series - Commercial aircraft passenger seats - Reliability testing
Luft- und Raumfahrt - Fluggastsitze für die zivile Luftfahrt - Zuverlässigkeitstests
Série aérospatiale - Sièges passagers d’avions commerciaux - Essais de fiabilité
Le présent document spécifie les exigences minimales des essais de fiabilité pour les sous-composants des sièges passagers des aéronefs commerciaux. Des procédures d'essai comprenant des cas de charge en service concernant le comportement des passagers pour les sous-composants de sièges sont définies. Les charges excessives sont exclues. Ce document est applicable aux sous-composants de sièges tels que, sans toutefois s'y limiter, le dossier, l’appuie-tête, les accoudoirs, la tablette, la pochette à documentation et les organes de commande.
Le présent document ne s’applique pas aux ceintures, systèmes de divertissement à bord, housses et rembourrages de siège.
D'autres éléments environnementaux tels que la température, les rayonnements, les gaz et les liquides peuvent également avoir un impact sur la fiabilité des sièges passagers d’aéronefs et de leurs sous-composants au cours de leur vie, mais ils ne sont pas pris en compte dans le présent document.
Des essais d'abrasion et de durabilité des surfaces sont définis dans l’EN 4860, l’EN 4864 et l’EN 4876.
Aeronavtika - Potniški sedeži v komercialnih letalih - Preskušanje zanesljivosti
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
oSIST prEN 4888:2022
01-december-2022
Aeronavtika - Potniški sedeži v komercialnih letalih - Preskušanje zanesljivosti
Aerospace Series - Commercial aircraft passenger seats - Reliability testing
Luft- und Raumfahrt - Fluggastsitze für die zivile Luftfahrt - Zuverlässigkeitstests
Série aérospatiale - Sièges passagers d’avions commerciaux - Essais de fiabilité
Ta slovenski standard je istoveten z: prEN 4888
ICS:
49.095 Oprema za potnike in Passenger and cabin
oprema kabin equipment
oSIST prEN 4888:2022 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN 4888:2022
DRAFT
EUROPEAN STANDARD
prEN 4888
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2022
ICS
English Version
Aerospace Series - Commercial aircraft passenger seats -
Reliability testing
Série aérospatiale - Sièges passagers d'avions Luft- und Raumfahrt - Fluggastsitze für die zivile
commerciaux - Essais de fiabilité Luftfahrt - Zuverlässigkeitstests
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee ASD-
STAN.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 4888:2022 E
worldwide for CEN national Members.
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Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Abbreviated terms . 7
5 Reliability testing of aircraft sub-seat components . 7
5.1 Failure behaviour . 7
5.2 Reliability characteristics and their conversion . 8
5.3 Aspect test cycle time versus flight time and range . 8
5.4 Determination of reliability characteristics . 9
5.5 Degradation . 12
6 General test conditions . 12
6.1 General. 12
6.2 ATD . 12
6.3 Loading devices . 14
6.3.1 Loading device for applied loads. 14
6.3.2 Loading device for impact . 14
6.3.3 Loading device for literature pockets . 15
6.3.4 Loading device for backrest . 15
6.3.5 Loading device for seat pan . 16
7 Reliability testing of backrest . 18
7.1 Test requirements . 18
7.2 Test procedure . 19
7.2.1 General. 19
7.2.2 Test procedure for load case A. 19
7.2.3 General note for test procedure for load case B to H . 20
7.2.4 Test procedure for load case B. 20
7.2.5 Test procedure for load case C and D . 21
7.2.6 Test procedure for load case E . 22
7.2.7 Test procedure for load case F . 23
7.2.8 Test procedure for load case G . 24
7.2.9 Test procedure for load case H . 25
7.3 Failure criteria . 27
8 Reliability testing of moveable headrest . 27
8.1 Test requirements . 27
8.2 Test procedure . 29
8.2.1 Test procedure for load case A. 29
8.2.2 Test procedure for load case B. 29
8.2.3 Test procedure for load case C . 30
8.2.4 Test procedure for load case D1 and D2 . 30
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8.2.5 Test procedure for load case E . 32
8.2.6 Test procedure for load case F . 33
8.3 Failure criteria . 34
9 Reliability testing of armrest. 35
9.1 Test requirements . 35
9.2 Test procedure . 36
9.2.1 Test procedure for load case A . 36
9.2.2 Test procedure for load case B . 37
9.2.3 Test procedure for load case C . 37
9.2.4 Test procedure for load case D . 38
9.2.5 Test procedure for load case E . 38
9.2.6 Test procedure for load case F . 39
9.2.7 Test procedure for load case G . 40
9.2.8 Test procedure for load case H . 40
9.2.9 Test procedure for load case I . 41
9.2.10 Test procedure for load case J . 42
9.3 Failure criteria . 43
10 Reliability testing of table . 44
10.1 Test requirements . 44
10.2 Test procedure . 45
10.2.1 General . 45
10.2.2 Test procedure for load case C . 47
10.2.3 Test procedure for load case D . 48
10.3 Failure criteria . 49
11 Reliability testing of literature pocket . 50
11.1 Test requirements . 50
11.2 Test procedure . 50
11.2.1 Test procedure for load case A . 50
11.2.2 Test procedure for load case B . 51
11.3 Failure criteria . 51
Annex A (informative) Random failure behaviour rate . 53
Bibliography . 54
3
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European foreword
This document (prEN 4888:2022) has been prepared by the Aerospace and Defence Industries
Association of Europe — Standardization (ASD-STAN).
After enquiries and votes carried out in accordance with the rules of this Association, this document has
received the approval of the National Associations and the Official Services of the member countries of
ASD-STAN, prior to its presentation to CEN.
This document is currently submitted to the CEN Enquiry.
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Introduction
A well-organized reliability management process is very important for manufacturers in order to
achieve the reliability requirements set by the customers and to continuously maintain market position.
The prediction of the failure behaviour of a product in the field should be accomplished as early as
possible. An optimized reliability management process contains qualitative and quantitative reliability
methods based on fatigue damage calculations, test data, condition monitoring, field failure data and
warranty cost analysis, which have to be fused to a closed loop failure analysis system in order to
consider all lessons learned in the analysis tools used in product development.
Customers expect a reasonably priced product for reasons of time and costs, which has a high level of
quality and reliability at the same time.
The determination of the reliability of products is an essential component in the development and
manufacture of products. The reliability of these technical products describes the property of not failing
within a specified time period and to keep the failure rate on an acceptable rate until the end of life in
given functional and ambient conditions.
The reliability and its characteristics are described via the confidence level and confidence range. An
important contribution concerns the analysis of service life information resulting from corresponding
tests or reported from the service by customers.
Reliability testing involves the definition, implementation and analysis of tests that are to represent the
use of seats in aircraft.
Furthermore, the second largest task of reliability testing involves analysing field data provided as
feedback from airlines. In this way, the data are validated based on previously conducted tests and
prognoses for future seat models are compiled.
5
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1 Scope
This document specifies minimum reliability test requirements for sub-components of commercial
aircraft passenger seats. Test procedures including in-service load cases regarding passenger behaviour
for sub-seat components are defined. Abuse loads are excluded. This document is applicable to the sub-
seat components such as but not limited to backrest, headrest, armrest, table, literature pocket and
control elements.
This document does not apply to belts, Inflight-Entertainment, seat dress cover and cushions.
Additional environmental influences like temperature, radiation, gases and liquids may also alter the
reliability of the aircraft passenger seats and their sub-components over their lifetime but are not taken
into consideration of this document.
Tests on abrasion and surface durability are defined in EN 4860, EN 4864 and EN 4876.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN 1728:2012, Furniture - Seating - Test methods for the determination of strength and durability
1
SAE J826, Devices for Use in Defining and Measuring Vehicle Seating Accommodation
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
reliability
probability, that a product will not fail during specified time period under given functional and
environmental conditions
1
Available at www.sae.org
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4 Abbreviated terms
For the purposes of this document, the following abbreviated terms apply.
A/C aircraft
ATD anthropomorphic testing device
CTR centre
DWD downward
FOLD-EXT fold extant
FC flight cycle
FH flight hour
FWD forward
LAP load attack point
LH left hand
LR long range flight
MTBF mean time between failure
MTBUR mean time between unexpected/unscheduled repair/removal
MTTF mean time to failure
RH right hand
RWD rearward
SR short range flight
SWD sideward
TTL taxi – take off – landing
UWD upward
5 Reliability testing of aircraft sub-seat components
5.1 Failure behaviour
The failure behaviour of a product is recorded by the reliability and is, additionally to the functional
properties, an essential criterion for the product assessment.
Decorative is to be interpreted as a cosmetic addition to the substrate materials functionality.
During the tests, occurrence of defects will be separated in four different categories:
a) minor: defects or cosmetic findings, which have no or only a minor effect on the functionality of the
seat or a component and may be repaired or exchanged easily if necessary; depending on the
occurrence, these defects may be considered for the MTBF evaluation; test will be continued;
b) major: defects which have a direct effect on the functionality of the seat or a component; these
defects will be considered for the MTBF evaluation; test has to be stopped;
c) safety: defects which have a direct effect on the safety of an occupant, these defects will be
considered for the MTBF evaluation. The test shall be stopped and a safety evaluation shall be done.
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5.2 Reliability characteristics and their conversion
The following reliability characteristics are usually taken as a basis from the customer viewpoint:
a) in case of non-maintainable units: mean time to failure (MTTF);
b) in case of maintainable units: mean time between failure (MTBF);
c) mean time between unexpected/unscheduled repair/removal (MTBUR).
These values are usually given in flight hours (FH) and shall be converted for the tests in the load
spectrum. Assuming that a load spectrum corresponds to the use of the component during a flight
cycle (FC), it is necessary to determine how many flight cycles an aircraft undergoes during the given
MTBF time in flight hours.
This results from multiplication of the requirement in flight hours by the ratio of flight cycles per flight
hour:
FC
day
MTBF MTBF⋅ (1)
Load collective FH
FH
day
where
MTBFLoad collective is the mean time to failure load collective;
MTBF is the mean time to failure in flight hour (h);
FH
FC is the flight cycle per day;
day
FH is the flight hour per day (h).
day
The MTBF values determined from tests are converted into flight hours by transposing the equation
according to MTBF :
FH
FH
day
(2)
MTBF MTBF⋅
FH Load collective
FC
day
where
MTBF is the mean time to failure per flight hour (h);
FH
MTBF is the mean time to failure load collective;
Load collective
FC is the flight cycle per day;
day
FHday is the flight hour per day (h).
Failure and degradation parameters are defined in each individual testing criteria.
5.3 Aspect test cycle time versus flight time and range
To define scenarios, representing the daily usage of aircraft sub-seat components, different types of
commercial aircraft shall be considered. Single aisle aircraft mainly used for short and medium-range
flights and twin aisle aircraft used for mid-, long- and ultra-long range flights. As the flight hours per
flight cycle ratio differs between these two categories of commercial aircraft, different load scenarios,
occurring during one flight (e.g. repetition of a specified load case per flight), shall be considered.
As a minimum utilization of the aircraft, the data from Table 1 shall be used for the transformation of
MTBF values from load collectives into flight hours and vice versa according to 5.2. Deviation from
these values shall be justified by statistical data.
8
=
=
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Table 1 — Data for short range and long range
Value
Short range
Average flight duration 1,5 h
Average daily utilization 8,5 h
Average flight cycles per day 5,8
Long range
Average flight duration 8,0 h
Average daily utilization 13,0 h
Average flight cycles per day 1,6
5.4 Determination of reliability characteristics
The systematic failure behaviour rate, i.e. failure rate shall be calculated according to Formula (3).
β−1
β t
λ t ⋅ (3)
()
TT
where
is the failure rate (per load collative);
λ t
()
T is the characteristic lifetime (number of load collectives);
t is the running time (number of load collectives);
β is the Weibull shape parameter.
The MTTF can be calculated according to Formula (4).
1
MTTF T⋅Γ +1 (4)
β
where
MTTF is the mean time to failure (number of load collectives);
T is the characteristic lifetime (number of load collectives);
t is the running time (number of load collectives);
β is the Weibull shape parameter;
Γ is the Gamma function.
If the characteristic lifetime T is unknown, it can be calculated according to Formula (5).
9
=
=
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1
n β
β
t
i
T= (5)
∑
x
i=1
where
T is the characteristic lifetime (number of load collectives);
t is the running time of each test (number of load collectives);
i
β is the Weibull shape parameter;
x is the number of failure found;
n is the number of samples.
The MTTF can then be calculated according to Formula (6).
1
n β
β
t 1
i
MTTF ⋅Γ +1 (6)
∑
x β
i=1
where
MTTF is the mean time to failure (number of load collectives);
t is the running time for sample i (number of load collectives);
i
β is the Weibull shape parameter;
x is the number of failure found;
n is the number of samples;
Γ is the Gamma function.
Typical Weibull shape parameters for different materials are shown in Table 2 and shall be used.
Table 2 — Typical Weibull shape parameters
Material Weibull shape parameter β
Aluminium alloys (2024/3.1355), (7075/3.4365) 4,0
Titanium alloys (Ti6Al4V/3.7164) 3,0
Steel (R ≤ 1 655 MPa) 3,0
m
Steel (R > 1 655 MPa) 2,2
m
For other materials an estimation of the shape parameters should be compared to fixed values and if no
other proven data are available a conservative choice should be selected by using a Weibull shape
parameter of β ≥ 2,2.
The method in 5.4 is representing non-random failure behaviour and is therefore more accurate as the
simplified method shown in Annex A.
EXAMPLE 1 Five aluminium armrests (β = 4) of a long range seat were tested according to loads given in
Clause 8 until occurrence of a failure. The results of these 5 tests are shown in Table 3.
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Table 3 — Example test results
Repetition Running time Findings
(load collectives)
1 5 961
2 2 761
Armrest structure
3 3 301
cracked
4 4 536
5 3 305
1
4 44 4 4
4
5 961 + 2 761 ++3 301 4 536 + 3 305 1
MTTF ×Γ+1 4 462×0,9064 4 044 load collectives
54
According to 5.2, 4 044 load collectives at a long range seat are representing a MTTF of 32 350 flight
hours.
It may happen, that after a reasonable time, no failure will be found and the test is stopped. In this case
the method above cannot be used for the evaluation.
If no failure is found, only statistical minimum values can be determined with the formulas below:
1
MTTF T⋅Γ +1 (7)
min min
β
where
MTTF is the minimum mean time to failure (number of load collectives);
min
T is the characteristic lifetime (number of load collectives);
β is the Weibull shape parameter;
Γ is the Gamma function.
with
1
β
n
β
2∗ t
∑ i
i=1
(8)
T =
min
2
Χ
α
2 x+−1 ;1
( )
2
where
T is the minimum characteristic lifetime (number of load collectives);
min
t is the running time of each test (number of load collectives);
i
β is the Weibull shape parameter;
x is the number of failure found;
2
is the Chi-Square distribution;
Χ
α is the statistical level of significance (1 % to 99 %).
EXAMPLE 2 The armrest from the example above was improved and tested again. Each test was stopped after
6 000 load collectives equals 48 000 flight hours equals 10 years without any failure.
11
=
= = =
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1
4
44444
2× (6 000 ++++6 000 6 000 6 000 6 000 ) 1
MTTF ×Γ +1 8 913 load collectives
min
2
Χ 4
0,5
2(0+−1);1
2
According to 5.2, 8 913 load collectives at a long range seat are representing a MTTF of 71 300 flight
min
hours.
5.5 Degradation
This document only covers mechanical wear and tear on new parts. Degradation due to environmental
influences e.g. chemical ageing of plastic parts are not part of the scope of this document and neither
shall it be applied on anything then new parts.
6 General test conditions
6.1 General
All sub seat components should be tested with the pertinent seat. Any sub seat components not
pertinent to the relevant load paths do not need to be installed.
If the seat is used for the test, the seat shall be fixed via seat tracks or equivalent fixation to the test
bench.
Unless otherwise specified, the seat shall be stored in indoor ambient conditions for at least 24 h
immediately prior testing.
The test shall be carried out at indoor ambient conditions with a temperature of 23 °C ± 10 °C and
should be carried out with a relative humidity of 50 % ± 20 %.
Applied loading shall be maintained for at least 0,5 s.
After initial calibration of test equipment the equipment shall be kept in good working order to
maintain pertinent test results.
The following tolerances shall be used for the tests:
a) forces: ± 1 % of the nominal force for 100 N and above; ± 5 % of the nominal force below 100 N;
b) velocities: 0 % to 5 % of the nominal velocity;
c) masses: ± 1 % of the nominal mass;
d) dimensions: ± 3 mm of the nominal dimensions;
e) angles: ± 2° of the nominal angle.
The speed for cycle testing shall not be higher than 3 600 cycles per hour.
6.2 ATD
An ATD according to SAE J826 shall be used for the following test in this document.
The ATD device shall be representing
...
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