4.4 Certificate of Release to Service (CRS), EASA Form 1 & Record-Keeping

The Certificate of Release to Service (CRS - 145.A.50)

The Certificate of Release to Service (CRS) is the primary statutory instrument that authorizes an aircraft or aeronautical component to return to operation following maintenance. Under 145.A.50, an aircraft cannot be flown, and a component cannot be installed, until a formal CRS has been issued by authorized certifying staff on behalf of the approved organisation.

Legal Prerequisites for Issuing a CRS

Before signing a CRS, the certifying staff member must positively verify that:

1. Full Scope Execution: All maintenance tasks ordered by the customer (operator or CAMO) have been properly completed in accordance with the procedures specified in the approved MOE;
2. Approved Maintenance Data: All maintenance has been performed using current, applicable maintenance data (AMM, CMM, SRM, SBs, ADs);
3. Tool and FOD Clearance: All tooling, ground equipment, staging, and temporary access equipment have been completely removed, and an inventory check confirms no tools or foreign objects remain inside aircraft cavities;
4. Independent Inspections: All critical maintenance tasks have undergone documented independent inspections per 145.A.48(b);
5. Airworthiness Confirmation: There are no known non-compliances, outstanding defects, or unairworthy conditions that endanger flight safety.

Incomplete Maintenance and Defect Deferral

If ordered maintenance cannot be completed (e.g., due to parts shortages or operational dispatch imperatives):

• The incomplete maintenance must be explicitly agreed upon with the aircraft operator or CAMO;
• If the incomplete task involves an inoperative defect, it may only be deferred if permitted by the operator's approved Minimum Equipment List (MEL) or Configuration Deviation List (CDL);
• The certifying staff must record the deferred maintenance and any operational flight limitations in the aircraft technical logbook and explicitly annotate the limitation on the CRS statement.

Mandatory Phrasing and Content of the Aircraft CRS

Under AMC 145.A.50(b), the Certificate of Release to Service on an aircraft must contain specific, unalterable statutory language:

"Certifies that the work specified, except as otherwise specified, was carried out in accordance with EASA Part-145 and in respect to that work the aircraft/aircraft component is considered ready for release to service."

In addition to the standardized release statement, the CRS entry must record:

• The EASA Part-145 approval certificate number of the organisation;
• The date and time of release, total aircraft flight hours, landing gear cycles, and engine flight cycles;
• The full signature, printed name, and unique Company Certification Authorisation (CCA) number of the certifying staff member;
• Detailed cross-references to the work package, job card numbers, technical logbook entry, and specific revision levels of the maintenance data used.

Differences Between Line CRS and Base CRS

The regulatory mechanism for issuing an aircraft CRS depends heavily on whether the maintenance event is line or base maintenance:

• Line Maintenance CRS: Issued directly in the aircraft technical logbook. It can be signed by Category A certifying staff (for minor scheduled line tasks and simple defect rectifications personally performed within their authorization limits) or by Category B1 / B2 certifying staff (for line maintenance troubleshooting and LRU replacements within their mechanical or avionic scopes).
• Base Maintenance CRS: Issued following the completion of heavy base maintenance checks (e.g., C-checks, structural modifications). It must be signed by Category C certifying staff as a single release covering the entire aircraft. The Category C engineer signs the CRS only after receiving verified task sign-offs and concurrence from all Category B1 and Category B2 support staff who oversaw the physical work packages.

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Component Release via EASA Form 1

While an aircraft is released to service via an entry in the aircraft technical logbook, aeronautical parts, engines, and auxiliary power units (APUs) maintained off-wing in specialized workshops are released via an EASA Form 1 (Authorized Release Certificate).

Dual Nature of EASA Form 1

The EASA Form 1 fulfills two fundamentally distinct statutory functions depending on the issuing organisation:

1. Production Conformity (Part-21 Subpart G - Block 13): Issued by an approved Production Organisation Approval (POA) holder to certify that a newly manufactured component was produced in conformity with approved type design data (signed in Block 13b).
2. Airworthiness Release following Maintenance (Part-145 or Part-CAO - Block 14a): Issued by an approved maintenance organisation to certify that maintenance work on an in-service component was carried out in accordance with approved continuing airworthiness data (signed in Block 14b).

Important Legal Fact: An EASA Form 1 is an official airworthiness certificate, not a commercial delivery note, invoice, or shipping bill. It confirms that the work detailed in Block 11 and Block 12 was executed to statutory airworthiness standards.

Anatomical Structure of EASA Form 1

Block 11 Standardized Status Terms

Under Appendix II to Part-145, certifying staff must enter one of only four standardized terms in Block 11. Using non-standard terminology invalidates the certificate:

1. Overhauled: Restored to the full overhaul standard specified in the Component Maintenance Manual (CMM). Involves complete disassembly, chemical cleaning, non-destructive inspection, replacement of 100% mandatory replacement parts (seals, bearings, hardware), reassembly, and testing to "new-limits" or overhaul tolerances.
2. Repaired: Rectification of a specific defect to restore the component to an airworthy condition in accordance with approved repair data (e.g., welding a bracket, replacing a damaged pin).
3. Inspected / Tested: Examination, dimensional measurement, calibration, or functional bench-testing to verify serviceability without extensive teardown or overhaul.
4. Modified: Incorporation of an Airworthiness Directive (AD), manufacturer Service Bulletin (SB), or approved design modification altering the component's configuration.

Dual Release (EASA / FAA) under Bilateral Agreements

Under the Bilateral Aviation Safety Agreement (BASA) between the European Union and the United States, an EASA Form 1 may be issued as a Dual Release certifying compliance with both EASA Part-145 and FAA 14 CFR Part 145. To issue a dual release:

• The European organisation must hold an FAA FAR-145 Repair Station Certificate under the Maintenance Annex Guidance (MAG);
• Maintenance must comply with FAA special conditions (e.g., testing to US standards, reporting unairworthy conditions directly to the FAA within 96 hours);
• Block 12 must contain the specific dual release statement referencing both the EASA Part-145 approval number and the FAA Repair Station Certificate number, while Block 14a is signed.

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Suspected Unapproved Parts (SUP) and Bogus Parts Interception

A Suspected Unapproved Part (SUP)—commonly termed a "bogus part"—is any aeronautical part or material that does not meet approved design or maintenance standards. SUPs pose an existential threat to aviation safety. Categories of SUP include:

• Counterfeit parts produced by unauthorized manufacturers;
• Stolen parts, or parts retrieved from scrapped or crashed aircraft that have been cosmetically refurbished without approved overhaul;
• Parts accompanied by forged or falsified EASA Form 1 / FAA 8130-3 certificates;
• Parts reworked beyond published CMM repair limits or produced using unapproved materials.

Interception and Quarantine Protocol

1. Incoming Inspection: Receiving stores inspectors must check physical part tags, serial numbers, finish, packaging, and accompanying documentation against approved data.
2. Immediate Quarantine: If a part is suspected of being unapproved, it must be quarantined immediately in the locked quarantine store. It cannot be released to production under any circumstances.
3. Mandatory Occurrence Reporting: Under 145.A.60 and Regulation (EU) No 376/2014, the organisation must notify the Competent Authority and the Type Certificate holder within 72 hours using EASA Form 44 or the national occurrence reporting portal.

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Maintenance Records and Document Retention (145.A.55)

Under 145.A.55, an approved maintenance organisation must record all details of maintenance work carried out. The legal standard requires that maintenance records provide an unbroken, tamper-evident audit trail demonstrating that every action complied with approved data.

The 3-Year Retention Rule

The organisation must retain a copy of all detailed maintenance records and any associated maintenance data (including job cards, dimensional logs, NDT reports, EASA Form 1 certificates, and CRS releases) for at least 3 years from the date the aircraft or component was released from the organisation.

Storage Safeguards and Electronic Records

• Protection Against Hazards: Records must be stored in archives protected from fire, flood, humidity, pestilence, and theft.
• Electronic Record Safeguards: Where digital maintenance record systems are utilized, the software must incorporate robust access authentication, role-based cryptographic permissions, write-once audit logs preventing unauthorized alteration or retroactive editing, and daily off-site backups stored in a geographically distinct, secure facility.
• Handover to Operator: The organisation must supply a complete copy of each CRS, along with copies of all specific detailed repair and modification records, to the aircraft operator (CAMO). This ensures the owner can fulfill their lifelong aircraft record-keeping obligations under Part-M (M.A.305).

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Safety Management System (SMS) Integration (Regulation (EU) 2021/1963)

In December 2022, Commission Regulation (EU) 2021/1963 fully entered into force, transposing ICAO Annex 19 standards into EASA Part-145. This landmark reform transitioned Part-145 from traditional, purely reactive Quality Assurance (QA) to an integrated Management System combining compliance monitoring with a proactive Safety Management System (SMS).

Key Components of the Integrated Management System

1. Safety Policy & Objectives: The Accountable Manager establishes measurable safety objectives, visible safety leadership, and an active safety culture.
2. Safety Risk Management (SRM): Proactive hazard identification, risk assessment using 5x5 probability-severity risk matrices, and risk mitigation to As Low As Reasonably Practicable (ALARP).
3. Safety Assurance & Compliance Monitoring: Replaces the old quality manager with an integrated Compliance Monitoring function that performs independent audits of all maintenance bays, stores, and procedures on an annual audit cycle.
4. Safety Promotion: Comprehensive human factors and safety training, safety bulletins, and sharing lessons learned.

Internal Safety Reporting Scheme (145.A.202) & Just Culture

Under 145.A.202, every Part-145 organisation must establish a confidential Internal Safety Reporting Scheme:

• Scope: Enables all employees to report safety hazards, near-misses, maintenance errors, tooling deficiencies, or procedural ambiguities without fear of retribution.
• Just Culture Protection: In accordance with Regulation (EU) No 376/2014 (Article 16), the organisation must enforce a formal Just Culture policy. Personnel who report safety occurrences or human errors are legally protected from disciplinary action, provided the event does not involve gross negligence, wilful misconduct, or deliberate criminal violation.
• Investigation and Mitigation: Reports are analyzed by the Safety Manager to identify root causes and implement corrective organizational changes, rather than assigning individual blame.

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Practical Maintenance Scenario & Module 10 Exam Tips

Maintenance Practical Scenario: A component workshop receives a CFM56 engine high-pressure turbine nozzle guide vane assembly for overhaul. Following complete disassembly, chemical cleaning, fluorescent penetrant NDT inspection, thermal barrier coating re-application, and airflow bench calibration per the CMM, an authorized component certifying technician prepares the EASA Form 1. In Block 11, the technician enters the term "Overhauled". In Block 12, the technician lists the CMM revision number, certifies compliance with all applicable EASA Airworthiness Directives, and documents the accumulated flight hours and cycles. In Block 14a, the technician signs the Part-145 maintenance release statement, notes their CCA number in Block 14c, and dates the release in Block 14e. The Form 1 is attached to the component in protective packaging.

Module 10 Exam Tips:

• An aircraft CRS is issued under 145.A.50; a component release certificate is the EASA Form 1.
• Block 11 of EASA Form 1 permits only four terms: Overhauled, Repaired, Inspected/Tested, Modified.
• Block 13 of Form 1 is used for Part-21 Production Conformity; Block 14a is for Part-145 Maintenance Release.
• Maintenance records must be retained for at least 3 years from the date of release (145.A.55).
• Occurrence reporting under 145.A.60 / Reg 376/2014 must be submitted within 72 hours.
• Just Culture (145.A.202) protects employees from discipline for honest errors, but does not protect against gross negligence or wilful misconduct.