Stc Twenty One Limited

STC Twenty One Limited is an EASA approved Design Organisation based in the Midlands. We specialise in the approval of after market design changes for medium to large air transport aircraft/rotorcraft. Our EASA terms of approval includes changes to aircraft- Interiors - Structures - Environmental Systems - Hydro-Mechanical Systems - Avionic Systems - Electrical System - Repairs - Performance - Aerodynamics We also hold a privilege to issue Flight Conditions and Permit to Fly approvals. We have extensive experience in- VIP and VVIP installations - Flight Test & Evaluation - Aircraft Role Change - Freighter Conversions - Specialist conversions e.g. Carriage of Horses & Grooms - SATCOM (Iridium Ku-Band, Inmarsat)- Link CPDLC - TCAS Change 7.1 - GPS - ADSB - FANS + For details visit