EN 9138:2019

SLOVENSKI STANDARD
01-januar-2020
Aeronavtika - Sistemi vodenja kakovosti - Statistični proizvod - Zahteve za sprejem
Aerospace Series - Quality Management Systems - Statistical Product - Acceptance
Requirements
Luft- und Raumfahrt - Qualitätsmanagementsysteme - Statistische
Produktannahmeanforderungen
Série Aérospatiale - Système de management de la qualité - Exigences d'acceptation
statistique des produits
Ta slovenski standard je istoveten z: EN 9138:2019
ICS:
03.120.10 Vodenje in zagotavljanje Quality management and
kakovosti quality assurance
49.020 Letala in vesoljska vozila na Aircraft and space vehicles in
splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 9138
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2019
EUROPÄISCHE NORM
ICS 03.120.10; 49.020
English Version
Aerospace Series - Quality Management Systems -
Statistical Product - Acceptance Requirements
Série aérospatiale - Systèmes de management de la Luft- und Raumfahrt - Qualitätsmanagementsysteme -
qualité - Exigences d'acceptation statistique des Statistische Produktannahmeanforderungen
produits
This European Standard was approved by CEN on 10 December 2018.

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. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists 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, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 9138:2019 E
worldwide for CEN national Members.

Contents
Page
0.1 Paradigm of quality requirements and product acceptance plans . 11
0.1.1 Engineering . 11
0.1.2 Operations . 12
0.2 Acceptance method considerations . 12
1 Scope . 15
1.1 Purpose . 15
1.2 Application . 15
2 Normative references . 15
2.1 International Aerospace Quality Group publications . 15
2.2 American National Standards Institute publications . 16
2.3 International Organization for Standardization publications . 16
2.4 Japanese standards . 17
2.5 Published books and periodicals . 17
2.6 SAE International publications . 18
2.7 Standardization Administration of China publications . 18
2.8 United States Military standards . 18
3 Terms and definitions . 19
4 General requirements . 30
4.1 Introduction to general requirements . 30
4.2 Trained personnel . 30
4.3 Safety/critical characteristics . 31
4.4 Quality requirements and parameters . 31
4.4.1 Quality parameter . 31
4.4.2 Quality parameter value . 31
4.4.3 Alternative quality plans . 32
4.4.4 Regulatory requirements . 32
4.5 Selection of samples . 32
4.6 Consideration of product and process characteristics . 32
4.7 Evaluation systems . 32
4.8 Non-conformances (within the sample) . 33
4.9 Statistical product acceptance plans and records . 33
4.10 Alternate statistical techniques for product acceptance . 33
4.11 Auditing of statistical techniques for product acceptance . 33
5 Required information to be documented . 34
5.1 Documented procedure requirements . 34
5.2 Initial Reliability Requirement or quality parameter values for product acceptance . 34
5.3 Assigning responsibilities . 34
5.4 Assigning where applied . 34
5.5 Establishing a training program . 34
5.6 Controlling non-conformances . 34
5.7 Monitoring performance and effectiveness . 34
5.8 Defining adjustments to inspection frequency . 35
5.9 Customer approval of procedures and plans . 35
6 Requirements for accepting product by individual lots . 35
6.1 General requirements for individual lot sampling . 35
6.2 Quality parameters for individual lot sampling . 35
6.2.1 Delivered product conformance probability parameters . 35
6.2.2 Probability of acceptance parameters . 35
6.3 Sample sizes for individual lots . 35
7 Requirements for accepting product under switching rules . 35
7.1 General requirements for switching rules . 35
7.2 Background information for switching rules . 36
7.3 Quality parameter with switching rules . 36
7.4 Requirements for accepting product with switching rules . 36
7.4.1 Sampling documentation . 36
7.4.2 General conditions . 36
7.4.3 Sampling plan criteria. 37
7.4.4 Qualification criteria for sampling . 37
7.5 Requirements for accepting product by variables sampling plans using switching
rules . 37
7.5.1 Variable sampling application limits . 37
7.5.2 Evaluating lot quality . 37
7.5.3 Related requirements . 37
8 Requirements for accepting product produced under process controls . 38
8.1 General process control requirements . 38
8.1.1 Data . 38
8.1.2 Reducing inspection with process controls . 38
8.1.3 Measurement systems . 38
8.1.4 Training program . 38
8.1.5 Process control points . 39
8.1.6 Process control acceptance plans and records . 39
8.1.7 Unbiased sampling . 39
8.1.8 Time or production order sequence . 39
8.1.9 Data retention plan . 39
8.1.10 Periodic internal audits . 39
8.1.11 Retrievability system . 39
8.1.12 Limiting errors in measurement and recording . 39
8.1.13 Evaluating effects of corrective actions . 39
8.2 Statistical Process Control . 39
8.2.1 Methods . 40
8.2.2 Location and dispersion . 40
8.2.3 Basis for control limits . 40
8.2.4 Basis for stability . 40
8.2.5 Investigation . 41
8.2.6 Violation of stability . 41
8.2.7 Re-evaluation of stability and capability . 41
8.2.8 Capability and process control . 41
8.2.9 Process monitoring frequency . 42
8.3 Variation restrictions . 42
8.4 Process parameter controls . 42
9 Additional requirements for accepting products based on continuous sampling,
skip-lot sampling, or methods for special cases . 43
9.1 Continuous sampling . 43
9.1.1 Quality parameters for continuous sampling . 43
9.1.2 Inspection sequence . 43
9.1.3 General conditions . 43
9.1.4 Supply Chain Management Handbook continuous sampling tables . 43
9.2 Skip-lot sampling. 44
9.2.1 General conditions for skip-lot sampling . 44
9.2.2 Quality protection equivalency . 44
9.2.3 Considerations for subsequent lots . 44
9.3 Sampling strategies for special cases . 44
9.3.1 Special sampling customer approvals . 44
9.3.2 Special case statistical validity . 44
9.3.3 Predicting quality from correlated variables . 45
9.3.4 Continuous manufacturing process – First and last unit for a lot produced . 45
9.3.5 Sequential sampling . 45
9.4 Other methods for special cases . 45
Annex A (informative) Guidelines for assigning Initial Reliability Requirement quality
levels . 46
A.1 Introduction . 46
A.2 Assigning quality levels . 46
A.3 Initial Reliability Requirements . 46
Annex B (informative) Acronym log . 49
Annex C (informative) Mathematics for accepting product under lot-by-lot inspection . 52
C.1 Yield estimation . 52
C.1.1 Yield estimates . 53
C.1.2 Confidence limits on yield estimates . 53
C.2 Probability of acceptance mathematics . 55
C.2.1 Hypergeometric probability of acceptance . 55
C.2.2 Legacy Pa lot acceptance mathematics . 56

C.2.3 Yield rates, discrete units, and conformance probabilities . 57
C.2.4 Impact lot sampling methods on delivered yield . 58
C.3 Controlling the probability of conformance for delivered product . 60
C.3.1 Average Outgoing Quality Limits . 60
C.3.2 Average Outgoing Quality Limit sample sizes . 61
C.3.3 Outgoing Quality Confidence Limit sample sizes . 62
C.3.4 Lot sampling with deliveries from the sample of failed lots . 63
C.3.5 Probability of acceptance sample sizes . 64
C.3.6 Lot sampling with destructive tests . 64
C.4 Mathematics to control clustering . 65
C.4.1 Formulation for cluster control . 65
C.4.2 Fixed number of maximum escapements . 66
C.4.3 Controlling clusters in increasing lot sizes . 66
Annex D (informative) Guidelines and recommendations for successful implementation of
statistical product acceptance methods . 67
D.1 Guidelines for 4.2 — Trained personnel. 67
D.1.1 General training . 67
D.1.2 Training for lot sampling . 67
D.1.3 Training for product acceptance based on process controls . 68
D.1.4 Training for continuous sampling, lot sampling with switching rules, skip-lot
sampling, or process control methods . 68
D.1.5 Non-published statistical methods . 68
D.2 Guidelines for 4.3 — Safety/critical characteristics . 68
D.3 Guidelines for 4.4 — Quality requirements and parameters . 69
D.3.1 Guidelines for Initial Reliability Requirement assignment . 69
D.3.2 Guidelines for quality parameter measures . 69
D.4 Guidelines for 4.5 — Selection of samples . 69
D.4.1 Sampling recommendations . 69
D.4.2 Simple random sampling . 70
D.4.3 Stratification sampling . 70
D.4.4 Systematic sampling . 70
D.4.5 Cluster sampling . 70
D.4.6 Representative sampling without randomization . 70
D.5 Guidelines for 4.6 — Identification of product characteristics . 71
D.6 Guidelines for 4.7 — Evaluation systems . 71
D.6.1 Measurement devices . 71
D.6.2 Non-Destructive Testing . 71
D.6.3 Destructive testing . 72
D.7 Guidelines for 4.8 — Non-conformances (within the sample) . 72
D.7.1 Non-conformance risks . 72
D.7.2 C = 0 sampling . 72
D.7.3 Retrievability in reduced, continuous, or skip-lot sampling . 73
D.8 Guidelines for 4.9 — Statistical product acceptance plans and records . 73
D.8.1 Statistical product acceptance plans . 73
D.8.2 Acceptance records . 73
D.8.3 Training records . 74
D.9 Guidelines for 4.10 — Alternate statistical techniques for product acceptance . 74
D.10 Guidelines for 4.11 — Auditing of statistical techniques for product acceptance . 74
D.11 Guidelines for 5.3 — Assigning responsibilities . 75
D.12 Guidelines for 5.4 — Assigning where applied . 75
D.13 Guidelines for 5.5 — Establishing a training program . 76
D.14 Guidelines for 5.6 — Controlling non-conformances . 76
D.15 Guidelines for 5.7 — Monitoring performance and effectiveness . 76
Annex E (informative) Discussion on the technical rationale and history of the relationship
of quality parameters to reliability . 77
E.1 Technical rationale for quality — Reliability relationship in quality parameters . 77
E.1.1 Minimum probability of conformance . 78
E.1.2 Probability of non-conformance . 78
E.1.3 Reliability . 78
E.2 History of quality — Reliability relationship in quality parameters . 78
E.2.1 Acceptable Quality Level . 79
E.2.2 Average Outgoing Quality Limit . 79
E.2.3 Short run sampling . 80
E.3 Recommended quality parameter choices . 80
E.4 Consideration of cluster effects . 81
Annex F (informative) Guidelines for choosing a statistical product acceptance technique
and quality parameter . 82
F.1 Guidance for choosing a method of statistical product acceptance . 82
F.1.1 General guidance . 82
F.1.2 Clause-specific guidance . 83
F.2 Directions to match a quality parameter to a statistical acceptance technique . 84
F.2.1 Guidelines for applying quality parameters . 84
F.2.2 Overview of quality parameter relationships to Initial Reliability Requirement . 84
F.2.3 Quality parameters for individual lot sampling . 84
F.2.4 Quality parameters for lot sampling with switching rules . 84
F.2.5 Quality parameters for product acceptance using process controls . 85
F.2.6 Quality parameters for continuous sampling and special methods . 85
F.3 Assigned by feature and tolerance. 85
Annex G (informative) Guidelines and recommendations for accepting product by
individual lots . 86
G.1 Introduction . 86
G.1.1 Process steps for evaluating individual or isolated lots . 86
G.1.2 Selecting an appropriate sampling model . 87
G.1.3 Screening lots . 88
G.2 Guidelines for 6.1.2 — Delivered product conformance probability parameters . 89
G.3 Guidelines for 6.2.2 — Probability of acceptance parameters . 89
G.4 Guidelines for relating AQL to a quality parameter . 90
G.5 Guidelines for 6.3 — Sample sizes for individual lots . 90
Annex H (informative) Guidelines for some special acceptance methods . 91
H.1 Continuous sampling extensions . 91
H.1.1 Guidelines for skip-lot sampling plans . 91
H.1.2 Guidelines for variables continuous sampling . 91
H.1.3 Poisson continuous sampling . 92
H.2 Process characterization . 93
H.2.1 Guidelines for 9.3.3 — Predicting quality from correlated variables . 93
H.2.2 Guidelines for 9.3.4 — Lot acceptance by first and last unit inspections . 94
H.2.3 Guidelines for Expected Outgoing Quality . 95
H.3 Probability Outgoing Quality Limit. 97
H.4 Validation of special acceptance methods — Simulation . 97
H.5 Guidance for small production volumes . 97
Annex I (informative) Guidelines and recommendations for accepting product produced
under switching rules . 98
I.1 Guidelines for Clause 7 — Requirements for accepting product produced under
switching rules . 98
I.2 Guidelines for 7.4 — Requirements for accepting product produced in repetitive lots
by attribute sampling plans . 98
I.3 Guidelines for 7.5 — Requirements for accepting product produced in repetitive lots
by variables sampling plans . 99
Annex J (informative) Guidelines and recommendations for accepting product produced
under process controls . 100
J.1 Guidelines for 8.1 — General process control requirements . 100
J.1.1 Guidelines for 8.1.12 — Limiting errors in measurement and recording . 100
J.2 Guidelines for 8.2 — Statistical Process Control. 100
J.2.1 Guidelines for 8.2.1 — Methods . 100
J.2.2 Guidelines for 8.2.3 — Basis for control limits . 101
J.2.3 Guidelines for 8.2.5 — Investigation . 101
J.2.4 Guidelines for 8.2.6 — Violation of stability . 102
J.3 Guidelines for 8.3 — Variation restrictions . 102
J.4 Guidelines for 8.4 — Process parameter controls . 102
J.5 Step-by-step summary . 103
Annex K (informative) Guidelines and recommendations for accepting product based on
continuous sampling . 104
K.1 Applicability of continuous sampling . 104
K.1.1 Conditions necessary for continuous sampling plans . 104
K.1.2 Conditions when continuous sampling inspection might be desirable . 105
K.1.3 Conditions when sampling plans require approval . 105
K.2 Types of continuous sampling plans . 105
K.3 Implementing continuous sampling . 106
K.3.1 Guidelines for 9.1.1 — Quality parameters . 106
K.3.2 Guidelines for 9.1.2 — Inspection sequence . 106
K.3.3 Submission of product . 106
K.3.4 Sample selection . 106
K.3.5 Corrective action indications . 106
K.3.6 Example continuous sampling plan . 106
Bibliography . 109

Figures
Figure 1 — Engineering and operations inputs into product acceptance plan . 11
Figure 2 — EN 9138 clause selection guide . 13
Figure 3 — Typical Statistical Process Control chart depicting control limits, warning limits, and
zones . 40
Figure C.1 — Average Outgoing Quality Operating Characteristic curve with Average Outgoing
Quality Limit and Initial Reliability Requirement limit . 62
Figure C.2 — Average Outgoing Quality Operating Characteristic curve where failed lots are
scrapped . 63
Figure C.3 — Points on Average Outgoing Quality Operating Characteristic curve for meeting
Initial Reliability Requirement when salvaging sample units from failed lots . 64
Figure G.1 — Flowchart for identifying lot sampling method . 88
Figure H.1 — Example graphic Confidence Level to match Initial Reliability Requirements . 94
Figure K.1 — Illustration of CSP-1 continuous sampling . 107
Tables
Table 1 — Acceptable Quality Level to Average Outgoing Quality Limit conversion . 32
Table 2 — True C requirements . 41
pk
Table A.1 — Minimum probability conformance values . 47
Table C.1 — Table of mathematical variables . 52
Table C.2 — Minimum sample sizes needed for a yield Confidence Level when no non-conformities
are detected . 55
Table C.3 — Expected escapements and delivered units . 59
Table C.4 — Average Outgoing Quality formulas for lot sampling categories. 60
Table C.5 — Average Outgoing Quality formulas for examining lot size limits . 61
Table C.6 — Expected escapements delivered units when tests are destructive . 64
Table E.1 — Formulas for converting quality parameter specifications into an Initial Reliability
Requirement . 80
Table E.2 — Conversion of Acceptable Quality Level specification to Average Outgoing Quality
Limit . 81
Table F.1 — Guidelines to determine inspection logistics . 82
Table F.2 — Quality parameter value to Initial Reliability Requirement value comparisons . 84
Table H.1 — Example computations for Expected Outgoing Quality . 96
Table I.1 — Example Acceptable Quality Level values to use to meet a required
3 % Average Outgoing Quality Limit . 99
Table K.1 — Values "i" for choice of "f" and Average Outgoing Quality Limit . 108

European foreword
This document (EN 9138:2019) 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 Standard has
received the approval of the National Associations and the Official Services of the member countries of
ASD, prior to its presentation to CEN.
This European Standard shall be given the status of a national standard, either by pub
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