Phases of Aircraft Certification

1.  Certification

           Certification is defined as a process which provides possibility of making certain that any aircraft whether civil or military has acceptable levels of safety for a given future utilization within the defined flight load spectrum for a specified period.

2.   Phases of Certification of an Aircraft

          Certification is normally carried out in four levels as shown in figure -1 below:

Figure -1: Aircraft Certification Phases

a) Level 1: Requirement Finalization - The requirement of the aircraft or the technical specification, the design standards (like FAR, Mil etc) and the materials to be used (existing approved materials or new materials to be developed) are decided in this phase. 

b)  Equipment (LRU) and Component Qualification 

c)  System level Qualification and 

d) Aircraft level functionality and operability assessment.  

3.  LRU Qualification 

     The LRU development and Qualification is carried out in phases as follows:

a) Development of F-F-F Model (Form, Fit and Function) - It is a model unit and used for checking the installation, functioning and access for maintenance. 

b) Prototype Model - Based on the F-F-F model experience, a prototype model is built with the engineering material to check proper functioning in full environment. 

c) SOFT Model - SOFT (Safety of flight test) model is an model which is subjected to all those exposures which are felt in each flight, SOFT is a subset of QT and soft cleared items can be released for developmental flight tests. In parallel full QT are carried out on other models. 

d) Qualification Test  (QT) Model - The QT model is subjected to qualification tests as follows;

     - Functional test on test rig

     - Structural test as proof of structural integrity

     - System Integration and ground evaluation 

     - Environmental test 

     - Flight and ground test 

     - Endurance test for life cycle environment. 

4.  System Level Certification 

Aircraft consists of many systems like Airframe Structure, Mechanical, Electrical, Powerplant, Avionics etc. The configuration design is based on the aerodynamics considerations. The system level certification will consists of evaluation of the system: 

  - System level functional requirements and all environment

  -  System safety an hazard requirement as per airworthiness standards

  - System Reliability (Redundancy or Fault tolerance) requirements 

  -  Maintainability requirements and 

  -  Specified life 

System evaluations go in phases

 - Design evaluation as per airworthiness requirement

 - Functional evaluation on system integration rig/box

 - Performance evaluation on aircraft at ground test

 - Performance evaluation on aircraft during flight.

5. Aircraft Level Evaluation 

Aircraft level tests to verify each system functioning at various stages:  

  - System evaluation during engine ground run (EGR)

  - System evaluation during Low speed Taxi Test (LSTT) (speed limited to 50 knots) 

  - System evaluation during High Speed Taxi Test (HSTT) (speed limited below to Vrotation speed)

  - Flight test evaluation 

6. Flight Test and Evaluation 

The principal purpose of flight testing is to determine if the complex machine designed can safely accomplish the designated task with the pilot workload kept within the human limitations and natural instinct of human being.

The flight test include handling quality assessment and evaluation of airworthiness performance requirements as well mission performance requirements. The flight tests are also to establish the operational boundary of the aircraft, aero-elastic and other boundaries. The all weather assessment will involve tests and evaluations under various airport altitude and ambient conditions. 

However there are some hazardous tests like determination of stall and spin behaviours, engine relight in air, safety assessment during simulated failures etc. which are normally carried out only after gathering enough data on the aircraft behaviour through flight tests. 

Military aircraft needs to go through weapon firing trials. 

7. Certification 

Based on the satisfactory tests and evaluation aircraft is issued with 

  - Type Certification (Civil Aircraft) 

  - Induction to service (Military aircraft). 

Associated activity during certification stage is the preparation of ODM (Operational Data Manual) , AFM (Aircraft Flight Manual) and MM (Maintenance manuals).