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.

Our Capabilities

Scope of Approval

Our EASA Part-21.J Approval covers Modifications and Repairs on Small and Large Aicrafts and Rotorcrafts, in the areas of:

  • Interiors
  • Structures
  • Avionics and Electrical
  • Engines and APU
  • Damage Tolerance & Fatigue
  • Flight conditions


We cover Major and Minor Cabin reconfigurations on all types of aircraft from Boeing, Airbus, ATR, Embraer and many others. From simple Emergency Equipment Layout (EEL) or Layout of Passenger Arrangement (LOPA) changes to full scale cabin refits with major modifications to galleys, lavatories and other large equipments and monuments


Our experienced team can cover composite and metalic repairs and changes to the aircraft structure and components. AOG repairs on the structure due to corrosion, ground equipment damages, lightning strikes and bird strikes are routinely carried out by our engineers. Major modfications such as antenna installations and demodifications, custom monument installations and EASA AMOC support on Airworthiness Directives are well within are capabilities.

Avionics and Electrical

We can cover a large number of electrical and avionics changes, for example involving cockpit systems, communication equipment and In Flight Entertainment (IFE) systems. Our Production Facility is also able to provide full modification kits and aircraft wiring looms to our own or your specs, to Airbus and Boeing standards with laser wire marked wires. Major modifications such as TCAS, ADS-B, CPDL and IFE introductions are within or capabilities.

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

End of Lease and Re-delivery support

We have many years of experience supporting leasing companies and operators during the aircraft Lease Return phase. From reconfigurations for the next operator, modification and repair revalidations, to demodifications, document verfication, and on-site support. We also provide Airworthiness Review Certificates (ARC) and FAA approvals through partner companies.

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)