TCM 1 392-1-9 LISI Aerospace [Bestas] Gazemir (TR) EN4071-120

Conditions for approval required by:  Julien Gauther

3 Replies to “TCM 1 392-1-9 LISI Aerospace [Bestas] Gazemir (TR) EN4071-120”

  1. On FAIR, MAX thread major diameter = 12,000 mm. As per EN4071, table 1, note a: “In accordance with ISO 5855-2. except the thread major diameter “d max.” which shall be equal to D1 min. – 0,025.”
    So, max thread major diameter shall be equal to 12 – 0,041 – 0,025 = 11,934 mm.
    Test results are compliant, but for future mfg batches, this shall be taken into account.

    On FAI, in column “Ref. location”, why do we have “EN4130” written against some dimensional characteristics? EN4071 and EN4130 bolts are similar, but not identical.
    On FAI, in column “Character. Designator”, it is written “minor” for all characteristics.
    How do we interpret “minor”?
    If we consider ISO9152, table 3, dimensional characteristics have not the same category of defects.
    Some dimensional characteristics are considered major with AQL = 1%, other dimensions are ranked as minor with AQL = 2,5% or 4%.
    So, for acceptance, do we have sample size for dimensional inspections as per ISO9152, tables 3 and 4? On FAI, sampling was done as per ANSI/ASQ Z1.4 general control level II and WI-SYS-30, but we do not have AQL applied.
    ISO9152 sampling (tables 3 and 4) is based on ISO2859-1, table II-A, single sampling, normal inspection. ISO2859-1 and ANSI/ASQ Z1.4 are really similar. From my point of view, this is the same way of sampling. Could you please confirm on your side?

    On FPI report, batch size is 249 bolts.
    32 bolts were FPI inspected.
    However, as per ISO9152, tables 3 and 4, AQL = 0,065% for discontinuities detection.
    Thus, in ISO9152 table 4, column AQL 0,065%, we have a down arrow marked against production batch size “151 to 280”. This down arrow means: “Use sampling plan below (sample size and Ac)”. In the case of sample size is equal to or greater than the batch size, a 100% inspection shall be performed.
    In this case, down arrow leads to sample 200 parts (with Ac = 0). So, 200 bolts should have been FPI checked instead of 32.
    This topic was already discussed in ASD-CERT Mechanical Workshop minutes (released in March 2019).
    These QTR was done before March 2019 since it is dated November 2018. This might explain why there is this sampling issue for FPI. If it is, could you please confirm that actions have been taken to apply right sampling plans?

    Tensile test on bolts: it seems that there are typos since minimum tensile requirement in QTR is 10,7 kN instead of 107 kN and actual values are around 11,6 or 12,1 kN. In statement of inspection and conformity, we have 10700 daN minimum, which is in line with ISO9152.

    For fatigue test on bolts, could you please precise which loads and frequency were applied?

    Hydrogen content on bolts: in QTR, table 1, it is stated that 5 bolts were tested and results are recorded in Annex 4 (CoC). However, in Annex 4, we have only 3 results.
    As per ISO9152, for qualification, 3 bolts shall be tested for hydrogen content. For Acceptance, 1 bolt has to be hydrogen content tested.
    On micrographic cuts, we can see some crevices on the crests of thread. Could you please confirm that these surface irregularities are within the tolerances specified in ISO9152, table 10?
    Maybe this is in relationship with manufacturing process (reduction used for forming the thread roll diameter by forging, as indicted in manufacturing route).

    Many thanks in advance for replying.

    1. Please see “EN4071 comments” file under additional documents section.

      Best Regards

  2. Thank you for replying. So, after reading your answers (additional documents section), the only remaining topic that needs to be clarified, for me, is sampling plans for non-destructive testing.
    This topic will be processed later.
    Best regards,

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