STC Twenty One Ltd has extensive experience in all aircraft types (fixed wing and rotorcraft) for aircraft environmental control systems.
We examine every aspect such as cooling, heating, ventilation, humidity/contaminant control and pressurisation in compartments that are occupied, used for cargo applications as well as electronic equipment. Our engineers improve efficiency, decrease weight as well as volume, and optimise energy consumption.
Environmental Control Systems
Why Choose Us?
STC Twenty One build systems designed and manufactured to maintain comfortable environments in the cockpit, passenger cabin and cargo hold throughout ground operations and flight modes. They are tailored to specific aircraft that comply with existing sources of compressed air.

Environmental Control Systems
Services & Approvals
In support of our wide ranging design capability, we design and certify services consisting of : Bleed Air, Air Conditioning & Pressurisation, Ice Protection, Water & Waste and Oxygen Systems.

Speak To The Team
Our CAA approved CVE’s have over 80 years combined experience in this sector.
UK CAA Approved Design Organisation
STC Twenty One
All aircraft modifications and aircraft repairs are managed by our UK CAA approved Design Office represented by STC Twenty One (UK.21J.0198).
What We Offer
Services
STC Twenty One Limited holds a Part 21 Subpart J DOA enabling it to certify UK CAA approved STCs and Major Repairs. Additionally, where a design change or repair is classified as minor, STC Twenty One Limited is authorised to approve them under the DOA using approval reference UK.21J.0198 through CAA.
Our employees are spread across our Avionics, Mechanical, Quality and Commercial Teams with a high level of experience and certification enabling the company to perform specialised services on engines and aircraft. Read more about our Services.