May 14, 2021, ©. Leeham News: The certification rules for different aeronautical vehicles are specific for each airworthiness jurisdiction. It means each country has its own rules for all the categories we listed in the last article. However, with the support of the International Civil Aviation Organization (ICAO), there is harmonization in many areas, especially around airport and airline operations. For airworthiness rules, most originated from dominant jurisdictions like the US FAA, whose rules have inspired the Canadian and European rules as well as many others.
As new technologies come to market, or new safety information is learned through testing, accidents, and incidents, the major regulatory agencies of the world constantly adapt with some rules harmonizing across jurisdictions and other rules diverging in different directions. It is an ever-evolving regulatory landscape that supports some of the safest transportation in the world, but it comes at a cost for companies as what was done in the past cannot always be expected to be accepted in the future, and the more global your desired market the more rules you need to understand and the more constraints your design will need to satisfy.
We use FAA as the example for how certification rules are partitioned and distributed and we show how the EU has transposed these into their ruleset, focusing on those areas with greatest impacts to an aircraft manufacturer.
|FAA Part||EASA||Subject||Type of Impact||Example|
|23, 25, 27, 29||23, 25, 27, 29||Initial Airworthiness for small airplanes, transport airplanes, small helicopters, and transport helicopters respectively||These sections (with only one typically applicable to any single product) govern the majority of the design safety rules to ensure design airworthiness at the time of initial type certification.||25.571 – Damage Tolerance – “An evaluation of the strength, detail design, and fabrication must show that catastrophic failure due to fatigue, corrosion, manufacturing defects, or accidental damage, will be avoided throughout the operational life of the airplane. […]”|
|33, 35||E, P||Initial airworthiness of major sub-products (engines and propellers respectively)||As with the aircraft level rules, these parts govern the airworthiness of sub-products considered significant & specialized enough to warrant their own full airworthiness certification.||33.49 – Endurance Test – “Each engine must be subjected to an endurance test that includes a total of 150 hours of operation […]”|
|TSO||ETSO||Minimum performance specifications for aircraft articles||These rules establish minimum performance standards for aircraft articles from cockpit recorders to seats. While not a full certification (meaning they cannot be installed on a specific aircraft without additional airworthiness approvals) these standards support suppliers of aircraft parts/systems with product approvals that help streamline their incorporation onto various products.||C63e – Airborne Weather Radar Equipment – This allows for the use of RTCA Document DO-220A to establish the minimum performance standards for such equipment.|
|21||21||Procedures||This is the part that explains what a Type Certification means, which rules need to be applied to receive one, how to control production to achieve airworthiness approval, what your obligations are as a TC/PC holder, and a myriad of other important information. It also governs issues such as when new or changed regulations do/don’t have to be incorporated into a product’s design.||21.17 – Designation of Applicable Regulations – “Except as provided in §§25.2, 27.2, 29.2, and in parts 26, 34, and 36 of this subchapter, an applicant for a type certificate must show that the aircraft, aircraft engine, or propeller concerned meets […]”|
|34, 36||34, 36||Environmental||These parts contain rules for emissions and noise, two key public interest areas for all aircraft designs.||A126.96.36.199 – Noise Certification Test and Measurement Conditions – “ This section prescribes the conditions under which noise certification must be conducted and the measurement procedures that must be used. […]”|
|91, 107, 121, 135||Air Operations
(965/2012), Unmanned (945/2019)
|Operational Rules (general aviation, unmanned systems, airline operations, small commuter operations respectively)||These parts contain rules that the operators must comply with depending on how they intend to use aircraft. Many of these rules can only be met with specific equipment or provisions on the aircraft, so while failure to meet these rules won’t prevent receipt of the type certificate, it may result in a failure to meet customer expectations.||91.715, no person may operate a civil aircraft unless it has within it the following: […]”
121.313(b) – “A windshield wiper or equivalent for each pilot station.”
135.364 – Maximum flying time outside the United States – “[…] no certificate holder may operate an airplane, other than an all-cargo airplane with more than two engines, on a planned route that exceeds 180 minutes flying time (at the one-engine-inoperative cruise speed under standard conditions in still air) from an Adequate Airport outside the continental United States unless the operation is approved by the FAA in accordance with Appendix G of this part, Extended Operations (ETOPS)”
This list is not exhaustive, but it is a useful place to start our coverage.
Other areas that impact product design/production include Part 5 for Safety Management Systems; Part 11, which includes rules on how to seek exemption from the regulations, Part 39 governing airworthiness directives when an immediate safety concern is identified in the current fleet, Parts 43/45 addressing maintenance and part marking, Part 61 covering type ratings for pilots (the influence of which everyone will remember from the 737 MAX), and Part 139 for airports, which can influence everything from wingspan due to separation & gate requirements (ref. the 777X folding wingtip) to takeoff performance requirements and vibration loads induced by runway quality.
In the next Corners, we will dive a bit deeper into the most important rulesets for an air vehicle project.