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Is an aviation component workshop allowed to release a line-replaceable unit (LRU) without going through a Final Test, if the LRU passes the pre-testing procedure and is found to be a No Fault unit?

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    $\begingroup$ Welcome to aviation.SE! Because you want to know if something is "allowed" or not, it would be best to say which country you're in and which aviation regulations apply to the aircraft (FAA? EASA?). $\endgroup$ – Pondlife Apr 20 '17 at 12:22
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    $\begingroup$ As Pondlife said, the question cannot be answered and should be closed as too broad unless you specify the jurisdiction which you are asking about. Different countries have different rules and the answer will change depending on where you are asking about. Please update your question and add a tag for the appropriate regulatory authority which you want to know about (faa-regulations, etc.) $\endgroup$ – Lnafziger Apr 20 '17 at 13:48
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I'm assuming by Pre-Testing procedure you are referring to a physical inspection and downloading the fault history.

If there are no logged faults in the fault history, it means that the built-in test (BIT) of the LRU did not detect any faults. BIT is not capable of 100% test coverage. It is also possible that BIT results are inaccurate. A lack of recorded faults is not sufficient to declare a unit airworthy.

Once an LRU is tagged and sent to the service center/shop, it can only be returned to service (RTS) after it has passed the RTS tests specified in the component maintenance manual. After passing the RTS tests, a 'maintenance release document' can be prepared and the unit returned to the spares pool.

In the US, the maintenance release document may be an FAA Form 8130-3, Form 337, or other document containing the information required by 14 CFR Part 43, sections 43.9 and 43.11. The maintenance release document must be signed by an authorized person who is certificated under 14 CFR Part 65. Though not legally required many shops will affix a "yellow tag" to the unit to indicate it's serviceable status.

EASA has similar rules, the primary difference being the required content of the documentation.

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  • $\begingroup$ What is "yellow tagged"? Are you assuming a particular jurisdiction? $\endgroup$ – Simon Apr 20 '17 at 14:34
  • $\begingroup$ @Simon Thanks for the reminder. Edited answer to better describe documentation and jurisdiction. $\endgroup$ – Gerry Apr 20 '17 at 17:16
  • $\begingroup$ Hi Sir lets say that the Pre-Test is the same as the Final test. Our process is something like this "If the unit fails the pre-test , it goes on the trouble shooting to figure out the defective part then repair then final test (RTS) then certification.. But if the unit passes the PRE-TEST , the unit goes directly to certification process." This is what I want to know if there is any reference documentation that an LRU should go through a Final Test. $\endgroup$ – Boy-Z May 3 '17 at 12:54
  • $\begingroup$ @Boy-Z If your 'Pre-Test' meets the requirements for RTS and the LRU passes, it can be released to service. Any LRU that is 'approved' - that is it is built under a TSO or a PMA must have documentation that provides "Instructions for Continued AIrworthiness" or ICA. In many case this will be in the form of a Component Maintenance Manual (CMM). This ICA or CMM will specify the return to service operating limits that must be met. A test must be performed to verify that it operates within these limits. It doesn't matter what you call the test as long as you document compliance. $\endgroup$ – Gerry May 3 '17 at 19:02
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to add on to the above answer (since i do not have enough points to comment yet), usually after installing the LRU on board the aircraft, there will be BIT and operational/functional tests to be done to confirm the unit is working.

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