Aircraft safety is of paramount importance in the aviation industry. To ensure its high level and to obtain a type certificate confirming compliance with the standard design, aircraft undergo a series of comprehensive tests. In the case of the regional SJ-100, this procedure includes more than two hundred different types of tests of the aircraft structure and units, onboard electronic equipment, and software.
Design tests are aimed at confirming the technical characteristics of individual units and aircraft systems that were laid down at the design stage. Laboratory tests allow to investigate the properties of materials and components under controlled conditions. One of the most complex and demanding tests are strength and life tests.
Strength bench tests are carried out to test the limits of strength and integrity of the aircraft structure. Their peculiarity lies in the fact that in the course of testing, the airframe is successively subjected to loads exceeding the design loads at which the structure, in particular the wing, may fail. And in this way the safety margin or its insufficiency is checked. Now in the Siberian Aviation Research Institute named after Chaplygin. Chaplygin Siberian Research Institute of Aviation SibNIA such tests are undergoing one of the prototype aircraft SJ-100, designed for bench testing.
In Novosibirsk, certification static tests of the fuselage, wing, mechanisation, main and front landing gear attachment units, horizontal plumage and engine pylon are being carried out. According to Dmitry Smirnov, Deputy Director for Science of the Institute, about 40 per cent of the total volume of strength and static tests have already been completed. SibNIA employees have tested the main and nose landing gear supports, pre-inflated the fuselage and pressurised it to check its tightness. In 2024 wing and plumage strength tests will take place, and preparations are underway for engine pylon tests.
In Zhukovsky, near Moscow, at the Zhukovsky Central Aerohydrodynamic Institute. Zhukovsky Central Aerohydrodynamic Institute in Zhukovsky near Moscow is another stand copy of the SJ-100. TsAGI specialists are carrying out resource tests on it, which in 2023 have been completed in the volume of 36 thousand flight cycles, which allows to perform the first flight of the aircraft in the updated form. In general, TsAGI provides scientific support of the work in terms of aerodynamics, strength and service life.
In the course of tests on “iron bird” and “electronic bird” stands, modes that are impossible or very dangerous to test in real flight are tested.
If static copies of the aircraft are used for bench tests, a functional model called “iron bird” is created to test the functioning of systems and their interaction with each other. The hydraulic system and mechanisms bench with semi-natural modelling of the complex control system and the control system of general aircraft equipment is characterised by a high degree of similarity to a real aircraft. The “Iron Bird” is a power frame equipped with actuators, wing mechanisation drives with real units of the complex control system, as well as the landing gear system. Those systems that involve hydraulics are represented here.
If an aircraft is created from scratch and there are many new solutions in its design in terms of layout and control system, then the creation of an “iron bird” is justified. For the SJ-100 it was not made, as the aircraft layout has not changed much in comparison with the previous imported version, but for the SSJ100 such a stand has existed at the State Research Institute of Aviation Systems (GosNIIAS) since the noughties.
The components of the SJ-100 aircraft’s on-board equipment complex (AEC) are being tested at the GosNIIAS on the semi-natural test stand “Electronic Bird”. The stand was created in close co-operation with PJSC Yakovlev and is designed to integrate and work out the interaction between the BWC and its software. The simulation environment is implemented on the stand, which allows linking the aircraft model with real on-board equipment and, if necessary, replacing any of the aircraft systems with a simulator. Thus, it is possible to work out individual components and systems in a complex, accelerating the processes of creating a new aircraft.
The state of modern technology allows the use of computer simulation to assess the behaviour of aircraft design under various conditions. Mathematical models (digital twins) help to predict and analyse aircraft performance and loads, complementing the results of full-scale tests. At present, individual nodes and units of the SJ-100 aircraft exist in digital form, which makes it possible to carry out modelling of certain processes. In the future, a digital twin will be created for the import-substituted aircraft, and Yakovlev is working in this direction.
The digital twin will not replace real aircraft testing, as many factors are difficult to take into account in virtual modelling, but in the world practice of modern aircraft construction a combination of digital and real modelling is used. Structural design and calculations are carried out digitally, which increases the probability of the design’s performance. Mathematical modelling allows to accurately and adequately simulate real loads in laboratory conditions, conducting tens, hundreds and thousands of loading cycles before flight.
The pinnacle of all described tests, inspections, modelling and tests are flight tests. They are conducted by experienced test pilots and on-board instrumentation operators, and flights are conducted under real operating conditions, but without passengers. Flight tests include checking all aircraft functions, evaluating its controllability, take-off and landing characteristics, as well as its overall reliability and safety.
Separately, for the extension of the type certificate, tests are carried out to verify the aircraft’s compliance with ICAO ground noise requirements, to check the aircraft’s de-icing system, and to operate the aircraft at low ground temperatures and at high latitudes to confirm that the piloting and navigation equipment operates reliably, without errors or malfunctions, even above the Arctic Circle. Such tests have already been carried out on the SSJ100 aircraft, but after the replacement of foreign equipment, engines and avionics, such tests will have to be repeated on the SJ-100.
The SSJ100 aircraft, developed by Sukhoi Civil Aircraft in the mid-2000s, has undergone a full range of tests. Now more than 160 aircraft of this type perform a huge number of commercial flights, carrying more than 40 million passengers by the beginning of 2023.
The new version of the Superjet is undergoing the import substitution process and preparing for the start of flight tests in a fully import substituted guise, including airframe, engines, landing gear, avionics, control system, as well as hydraulic, air conditioning and air supply systems. The import substitution procedure takes place within the framework of the current type certificate, but the volume of tests is comparable to the creation of a new aircraft. At the same time, tests of the new systems are conducted in parallel with their inclusion in the aircraft.
In 2024, an aircraft with partial import substitution will undergo flight tests, in particular, its engines are installed French-Russian SaM146, it is flight 97021 (s/n 97001). The machine made its first flight on 29 August 2023.
Next year it is expected to complete strength tests of the airframe in SibNIA, as well as the beginning of certification flight tests of two prototype aircraft: 97012 (s/n 95157) and aircraft with s/n 97003, its flight number is still unknown, as the aircraft is under construction.
