Singapore Technical Standard Order Certificate of Approval
Learn about the Singapore Technical Standard Order (STSO) Certificate of Approval required for designing articles used in aircraft.
Last updated 14 May 2026
What is a Singapore Technical Standard Order
A Singapore Technical Standard Order (STSO) sets the minimum performance standards for aviation articles such as life vests, aircraft seats and galley carts.
An STSO Certificate of Approval does not include approval for installation of the article on an aircraft. A separate aircraft modification approval is required to install the article on an aircraft.
Mutual recognition
CAAS has established bilateral agreements with other Civil Aviation Authorities on the processing of Singapore Technical Standard Order (STSO).
Application process
Who can apply
Applications may be submitted by CAAS Design Organisation Approval (DOA) holders with an approved scope to carry out article design activities.
How to qualify
The proposed article for the grant of CAAS STSO certificate of approval must meet the applicable airworthiness design standards stated in the Singapore Airworthiness Requirements Part 21 (SAR-21).
Further information on the requirements may be found in Subpart E of the SAR-21.
When to apply
Applications for CAAS STSO certificate of approval should be made when there is intent for an article’s design to be identified as approved by CAAS.
You are encouraged to engage CAAS early to facilitate planning and ensure sufficient time for the review and acceptance process.
What are the fees
The fees payable are stated in:
What is the processing time
Processing timelines vary by application type and are set out in IC 6/2025 Information circular on service standards for processing of aviation safety instruments related to airworthiness, flight operations and training organisations.
You are encouraged to engage CAAS early to discuss your STSO application to facilitate timely processing.
How to apply
Phase 1: Pre-application
The applicant meets with CAAS to provide details on the article design and better understand the application process.
Phase 2: Formal application
The applicant submits the application through eSOMS with all required supporting documents (as stated in SAR-21 AMC 21.455(a)), which includes:
the certification plan
details of the applicable certification basis
Phase 3: Document evaluation
CAAS reviews the application and supporting documents, and notifies the applicant on the level of CAAS involvement in compliance demonstrations.
Phase 4: Demonstration and inspection
CAAS verifies compliance with the relevant airworthiness design standards through participation in certification activities, such as conformity inspections and test witnessing.
Phase 5: Certification
Once compliance is confirmed, CAAS will issue an invoice and, upon receipt of payment, issue the STSO Certificate of Approval.
Application for STSO Certificate of Approval
To apply, submit your application on eSOMS.
If eSOMS is unavailable, download the application form and contact us. A CAAS officer will guide you through the manual application process.
What is the validity period
An STSO certificate of approval remains effective until it is surrendered by the holder or cancelled by CAAS.
STSO certificates of approval issued by CAAS
For a list of STSO certificates issued, download Singapore Technical Standard Orders issued.
Legislation, regulations and resources
Contact information
Flight Standards Division
Contact us using the Enquiries & Feedback Form.