EASA Part-21.J Design Services

KNSI is a EASA Part-21.J Design Organisation based in the Diamond Hangar in Stansted Airport, authorised to provide design services for modification and repair to the aircraft structure and cabin interior.

Why do you need a DOA


As an aircraft operator, owner or repair station the last thing you need is to pay the huge costs involved in getting setup and maintaining yourself as a Design Organisation for approving changes to your aircrafts. We know from experience that this is too costly and has a negative return on investment. Instead by leveraging KNSI's design expertise and outsourcing your design needs, you can save money and ensure your aircraft changes are completed and to EASA standards.

Modification kits

As well as the Design of Modifications, KNSI is able to leverage its Production capabilities to provide full modifications kits with EASA Form 1 release certificates to reduce the time and cost when implementing a Modification Package. Read more about our Production capabilities.

Easy route to upgrade your aircrafts

Upgrading your aircrafts to modernise the performance and capabilities can seem like a daunting task. With our experienced personnel you can get your aircrafts improved through our Design Services and Supplemental Type Certificates (STCs). From simple changes like the addition of noise-cancellation headphones to complete cabin changes to avionics upgrades, KNSI can help you develop and implement these changes you need on your aircrafts.

Typical projects

Some of the projects we have completed in the past include:

  • Wiring changes
  • Partition and closet installations
  • Placards and sign changes
  • Seat covers/trim/cushion changes and overhauls
  • Galley equipment changes
  • IFE changes
  • Cabin reconfiguration - LOPA changes
  • Decal installations
  • Repairs for skin damage, crack,
  • Fastener replacements
  • Carpet and curtain changes
  • Paint changes

Aircraft upgrades through STC

KNSI provide engineering and project management services for clients to upgrade their aircraft capabilities, performance and facilities though the development and application of Supplemental Type Certificates (STC). This could include fleet modernisation through improved cabin layouts, In Flight Entertainment (IFE) system upgrades, avionics upgrades, noise-cancellation headset additions and many more. Our most recent STC involves the modification of Economy Class Cabin seats on A320-300 aircrafts. Get in touch with us to get your aircrafts upgraded and your fleet modernised.

Design Approval


FAA validation

Supplemental Type Certificates (STC)

   Modification of Economy Class Cabin
(Filesize : 384 KB)

DOA Approval Categories

  • Small and large aeroplanes
  • Small and large rotorcraft
  • Engine and APU

DOA Approval Certificate

   EASA Part-21.J Approval
(Filesize : 80 KB)

   EASA Part-21.J Terms of Approval
(Filesize : 47 KB)

Approved partners

   Azerbaijan CAA DOA Recognition
(Filesize : 137 KB)