An introduction to Certification Specifications and Instructions for Continued Airworthiness - Edgevarsity Blog Edgevarsity
An introduction to Certification Specifications and Instructions for Continued Airworthiness

An introduction to Certification Specifications and Instructions for Continued Airworthiness

Flight safety begins with the design of the aircraft. This means not only that the structures, systems, flight performance, flight qualities, etc. must comply with the applicable requirements, but they also need to provide instructions for maintenance of the aircraft for repairs during the operational life. 

JAR/FAR 21/ EASA Part 21 might use different wordings while providing instructions for maintenance, but intent is the same. They provide Instructions for Continued Airworthiness (ICA).

The Design Approval Holder (DAH) is responsible for ensuring there is enough information in the ICA to maintain the continued airworthiness of the product.

ICAs are developed during the Type Certification (TC) process of an aircraft in accordance with relevant Certification Standards (CS)/ Federal Aviation Regulations (FAR). ICAs are usually provided through Aircraft Maintenance Manual (AMM), Structure Repair Manual (SRM), Service Bulletin (SB), Service Letter (SL), Maintenance Planning Document (MPD), Aircraft Flight Manual (AFM), Minimum Equipment List (MEL), etc or as an amendment to these manuals during Supplemental Type Certification (STC) process.

What are Certification Maintenance Requirements? 

Certification Maintenance Requirement abbreviated as CMR is a required scheduled maintenance task established during the design certification of the airplane systems as an operating limitation of the TC or STC.

The CMRs are a subset of the instructions for continued airworthiness identified during the certification process. A CMR usually results from a formal, numerical analysis conducted to show compliance with the requirements applicable to catastrophic and hazardous failure conditions. Compliance may also result from a qualitative, engineering judgment-based analysis.

A CMR is intended to detect safety-significant latent failures that would, in combination with one or more other specific failures or events, result in a hazardous or catastrophic failure condition.

So, what is an Airworthiness Limitation item?

Airworthiness Limitation item abbreviated as ALI is defined as a mandatory-maintenance action identified in the Airworthiness Limitations section of a design-approval holder’s Instructions for Continued Airworthiness.

These items contain mandatory modification or replacement times, mandatory inspection thresholds, intervals, and inspection procedures. 

What is Airworthiness Limitations section?

The Airworthiness Limitations section abbreviated as ALS is related to the Instructions for Continued Airworthiness.

ALS is a collection of mandatory-maintenance actions required for airplane structure and fuel-tank systems. For structural-maintenance actions, the ALS includes structural-modification times, structural-replacement times, structural-inspection thresholds and intervals, and structural-inspection procedures.

The ALS is part of the certificated product (aircraft, engine, propeller) type design that contains the mandatory scheduled maintenance items and the limitations for part replacement, necessary to maintain compliance with that type design. For each individual aircraft, an approved Aircraft Maintenance Programme (AMP) must be created, initially containing the ALS at the revision level applicable at the time of the aircraft’s first certificate of airworthiness.

Any change to the ALS is approved by EASA. In view of the nature of the tasks contained in the ALS, failure to comply with an ALS / or its revision leads to an unsafe condition. 

What are Certification Specifications?

Certification Specifications abbreviated as CS are the non-binding technical standards adopted by the EASA to meet the essential requirements of the Basic Regulation. 

These standards (EASA Airworthiness codes) are derived from Joint Aviation Requirements (JAR). JAR denomination has been changed in CS (Certification Specification).

Examples are below.

CS Definitions are derived from JAR 1.

CS-22 pertains to Sailplanes and Powered Sailplanes are derived from JAR22

CS-25 pertains to Large Aeroplanes derived from JAR 25.

CS-E pertains to Engines derived from JAR-E.

CS-ETSO pertains to European Technical Standard Orders derived from JAR-TSO.

Aeronautical engineers and Aircraft Maintenance Engineers are expected to read and understand Certification Specifications (CS 22, 23, 25, 26, 27, 29, 31, 34, 36, APU, E, ETSO, LSA, P, VLA, VLR, STAN, ACNS, AWO and OSD).

Below is the link from the EASA portal on CS-25. 

https://www.easa.europa.eu/sites/default/files/dfu/cs-25_amendment_26_0.pdf

Online aircraft maintenance engineering programs are expected to teach these certification standards.


by Sumanth Eswar

Ex Assistant Manager-Technical Services, Jet Airways

14 years of industry experience in various sections under Engineering and Maintenance department such as Engineering Planning, Technical Services Engineering including Structures, Cabin Maintenance, Airframe and Systems, Base Maintenance, Powerplant, Reliability, Aircraft Weighing, Rotable Management. Years of Safety Office experience and was a surveyor for Aircraft Insurance