On June 10 of this year, flight certification testing of the SJ-100 aircraft began at the M. M. Gromov Flight Research Institute. Developed by Yakovlev and approved by aviation authorities, the flight and ground testing program envisions a steady increase in work intensity. Currently, the first prototype, aircraft number 97021, is participating.
Andrey Boginsky, Deputy General Director of UAC for Civil Aviation and General Director of Yakovlev, stated: “Flight intensity will increase with the addition of two more prototypes, currently awaiting installation of PD-8 engines in Komsomolsk-on-Amur.”
Aircraft 97021 has SaM146 engines and import-substituted onboard equipment. The planes with domestic PD-8 engines are currently undergoing bench testing and will join trials later. The prototypes’ components align with the testing plans and demonstrate component readiness. The main goal is to replace foreign systems entirely with those developed by Russian companies.
The SJ-100 certification timeline shifted due to delays in PD-8 engine development. UAC emphasizes that timeline adjustments are necessary to ensure a comprehensive testing program of domestic systems and components. “Safety is one of the key priorities in creating this new modification of a civil aircraft,” Boginsky noted.
Flight testing is the visible portion of extensive certification work. Similar to an iceberg, a large portion of certification work remains unseen to the public. It includes engineering analyses, calculations, testing on isolated and complex stands, strength testing at industry institutes, and extensive qualification work on materials, components, and software.
Kirill Kuznetsov, the Chief Designer of the SJ-100, recently explained the certification process and challenges. He was asked how the certification test volumes of the SJ-100 compare to those of the SSJ-100.
I would break down the assessment into two areas: “the aircraft as a flying vehicle” and “the aircraft and its systems.”
The first area requires about 30 to 40% of the tests conducted for SSJ-100 certification. This relatively smaller volume is due to retaining the same theoretical designs, aircraft and system architecture, and most system interfaces in the new model. Therefore, many tests, especially those related to aerodynamics, stability, and controllability, do not require revalidation.
For the second area, the SJ-100 will need to replicate 90% of the SSJ-100’s testing, mostly on stands.
He went on to explain the stand testing:
The main document defining certification procedures is the domestic aviation regulation AP-21. For transport-category aircraft, the developer adheres to AP-25. This document establishes the project’s certification basis, detailing how to meet safety requirements. For this modification, the primary document is the Certification Basis RRJ-95, known as the SSJ-100, certified in 2011.
The certification basis requirements cascade from the lead developer to system, component, and subcomponent developers. The developer creates a certification program after finalizing the requirements.
The structure is designed to resemble a pyramid, with full-aircraft tests at the top, large integration stands below, followed by system and component testing stands, and laboratory tests at the base.
Explaining the stand tests, he said,
Integration stands include “Electronic Bird” at GosNIIAS, the comprehensive control system stand at the Moscow Institute of Electronics and Automation, and the air conditioning system stand at the “Teploobmennik” facility in Nizhny Novgorod. These large integration stands, introduced in 2021-22, enabled comprehensive testing, ensuring safety and support for aircraft 97021 during its first flight and refinement testing.
He explained the main challenges in integrating new domestic systems into the aircraft.
First, many participating companies are relatively new to technology, and second, many lack extensive experience in qualifying components for system integration into aircraft. Significant efforts have been made to develop prototype components, which now need to be tested, incorporated into the design, and documented for qualification and certification.
The absence of repeatable experience affects the rhythm and timelines for qualification tests. Adjusting and standardizing processes requires a structured approach despite challenging conditions. The PD-8 engine is a particularly complex issue, affecting our plans.
There are two main impacts: first, the demonstration of aircraft characteristics, such as takeoff and landing, and second, engine-system interaction, which we evaluate during flight and ground tests on aircraft 97021. We anticipate no major issues, as our approach to fixing intersystem interfaces allows much of this testing to be conducted on stands.
Due to engine delays, the flight test program has been extended and revised. We aim to maximize testing of systems and components on the first prototype equipped with SaM146 engines, allowing our co-developers to complete their qualification work and “freeze” the design. This approach minimizes adjustments needed for production in Komsomolsk-on-Amur.
He responded to the question, “Why are strength tests required on TsAGI and SibNIA stands if the airframe remains nearly unchanged?”
Over 15 years, substantial knowledge has been gained about structural performance, leading to updates in the airframe. Testing these changes is essential.
The certification process includes a hierarchy for verifying compliance. At the top are two primary stands: the static strength stand at SibNIA and the endurance stand at TsAGI. Both facilities have built and assembled new SJ-100 airframes.
The stands differ primarily in loading systems. The system at SibNIA focuses on static strength, while TsAGI’s technique ensures the required number of loading cycles for the targeted airframe life of 54,000 takeoffs and landings. Additionally, isolated stands are used to test mechanisms, specific structural components, and materials.
Speaking of the overall assessment of the SJ-100 certification status, he said,
We are confident in progressing toward an achievable goal while complying with all current certification standards. Technical risks exist, but that’s why we conduct tests. A key example is the engine, which involves significant innovation.
No matter the circumstances, it’s vital to maintain direction and complete the work. We’re not just developing an aircraft; together with Russian companies, we’re establishing a new system, gradually transforming challenging cooperative processes into stable, repeatable operations. Only by going through this process can we create a system capable of developing technology for large-scale use.
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