AIRWORTHINESS DIRECTIVE (AD) - A LEGAL DOCUMENT

In aviation industry, we often hear the term “Airworthiness Directive (AD)”. So, what actually is an AD? What triggers the issuance of this document? Who issues this document? What is the importance of this document? Why is it mandatory to comply to this document?

In this short article, I have tried to answer above questions by giving the overview of the AD and have illustrated the overall “Macro-level process” (without getting in to the details of every step) for AD issuance and compliance.

DEFINITION & BACKGROUND:

Any event, identified on aircraft, engine, propeller or appliances, which leads to or will lead to the hazardous and catastrophic results, is known as UNSAFE CONDITION as per EASA Part-21.A.3B. The existence of the unsafe condition compromises the level of safety of aircraft or components. The State of Design (SoD) analyses the data whether the identified unsafe condition is likely to exist in other aircraft or component of the same “Type Design”. If this is the case, the SoD issues Mandatory Continuing Airworthiness Information (MCAI) to address the identified unsafe condition in order to restore the level of safety. This MCAI is issued in the form of Airworthiness Directive (AD) which actually is, an amendment in the associated “Type Design”. The issued AD is a LEGAL DOCUMENT (enforceable rules) and compliance of such AD is mandatory for safe operation of aircraft.

CONTENTS OF AIRWORTHINESS DIRECTIVE:

The contents of AD should at least cover following minimum information:

1.??? The effective date of AD (when will the AD come in effect).

2.??? Identification of the Unsafe condition.

3.??? Identification of the affected aircraft, engine, component.

4.??? What actions must be done.

5.??? The compliance time of required actions.

RESPONSIBILITIES OF THE STATE OF DESIGN:

Once the AD has been issued by the State of Design (SoD), it is mandatory for the SoD to transmit the issued AD to the State of Registry (SoR) as per the requirements of ICAO Annex-8, Part-II, Ch-4.2.1.1.

RESPONSIBILITIES OF THE STATE OF REGISTRY:

The SoR shall either directly adopt the received AD (from SoD) without any further actions OR may assess the received information and take appropriate actions (i.e. issues its own AD on the basis of received MCAI from SoD) as per the requirements of ICAO Annex-8 Part-II Ch-4.2.4.1.

The aircraft operators / owners receive ADs from their State of Registry (National Aviation Authority) and are not allowed to operate an aircraft until all applicable ADs have been complied on the affected aircraft, engine, propeller, appliances.

SPECIFIC EXAMPLES:

1.??? European Union Aviation Safety Agency (EASA) is the “State of Design” for Airbus aircraft. Whenever, “unsafe condition” (Such as loss of oxygen supply system OR cracks on Main Landing Gear door actuator fittings on the keel beam etc.) is detected in Airbus aircraft, EASA will issue AD as per Basic Regulation (EU) 2018/1139 and Initial Airworthiness Regulation (EU) 748 / 2012. If a new aircraft is rolled out from Production, the compliance of all ADs can be checked from the issued EASA Form-52 (Certificate of Conformity) and associated Aircraft Inspection Report (AIR). If the aircraft is already in service, the compliance of ADs can be reviewed from record maintained by organizations approved under EASA Part-M, Part-CAMO, Part-CAO or Part-ML (as the case may be).

2.??? Federal Aviation Administration (FAA) is the “State of Design” for Boeing aircraft. Whenever, unsafe condition is detected in Boeing aircraft, FAA will issue AD as per FAA Order 8040.1 and associated 14 CFR Part-39.

CONTENT SOURCES & REFERENCES:

• ICAO Annex-8.
• EASA Rules & Regulations.
• FAA Rules & Regulations.
• Skybrary.aero.