As part of the process of replacing foreign components and systems in the new medium-range MC-21 aircraft, another unit made from Russian materials—the stabilizer—has proven its strength and reliability during tests at the Central Aerohydrodynamic Institute (TsAGI).
The stabilizer is a part of the aircraft’s tail assembly that ensures balance and stability in all flight modes. The purpose of the research was to confirm the static strength of the stabilizer’s torsion box, made from domestic polymer composite materials, under maximum load conditions.
The experiments were conducted on a stand that had previously been used to study the properties of a similar foreign-made component. The complex testing program included not only general strength tests but also localized strength assessments, particularly focusing on the stress levels in the hinge nodes, elevator, and stabilizer adjustment mechanism.
Additionally, the torsion box was subjected to loads exceeding 150% of the calculated levels, surpassing the load that caused the failure of the foreign-made composite component.
“The stabilizer torsion box made from Russian composite materials withstood maximum load levels and impact damage that simulated real aircraft operating conditions, demonstrating high structural strength and rigidity,” said Mikhail Limonin, Deputy Head of the Static and Thermal Strength Division at TsAGI.
The test results have been passed on to the MC-21 developer—PJSC “Yakovlev”—to prepare a certification report.
Additionally, strength tests of the imported replacement materials for the passenger cabin windows are currently underway at TsAGI. In the near future, tests will begin on cockpit windows and Russian-made floor elements.
A fully import-substituted version of the medium-range MC-21 aircraft is set to take to the skies this year, according to Anton Alikhanov, the head of the Ministry of Industry and Trade.
So what do we know about the stabilizer?
Back in 2017, the Ulyanovsk aircraft manufacturing enterprise Aviastar-SP, in cooperation with Irkut Corporation, produced the stabilizer for the fourth MC-21 passenger aircraft. The stabilizer was shipped from Ulyanovsk to the Irkutsk Aviation Plant for further assembly of the aircraft.
This component is almost entirely made of composite materials, with carbon fiber accounting for nearly 90 percent. The use of such materials significantly reduces the weight compared to a similar metal stabilizer.
– “Currently, several units are in different stages of assembly at Aviastar,” Mikhail Chuvashlov, head of the assembly shop for MC-21 components and units had said. “The production schedule is very tight. In the coming days, fuselage panels for the fifth aircraft will be shipped to Irkutsk. The underbelly section and doors are under assembly. The fuselage panels for the sixth aircraft are also being assembled,” he added.
As per a 2016 article, TSAGI was scheduled to use a multi-channel loading system developed in-house with the Italian company Atos to test the stabilizer.
In 2017, TSAGI Specialists conducted the resource tests of the stabilizer of the MC-21-300 passenger aircraft in the volume of one design resource – 60 thousand flight cycles.
Before the start of the test, the institute’s engineers applied standardized impact damage to the stabilizer box, which could occur during the operation of the aircraft. Then the structure was subjected to cyclic loads in a volume equivalent to 60,000 typical flights. Upon completion of the tests, no development of existing or formation of new defects was detected on the stabilizer box, which demonstrates the high reliability of the product at the initial stages of its operation.
The endurance tests of the stabilizer torsion box are currently ongoing. To ensure a high level of design reliability, it is necessary to implement about 120 thousand more flight cycles. According to preliminary estimates in the same year, this process would take about two more years.
However, this process took about 8 years to finish.
Aviastar-SP is one of the key participants in the MC-21 aircraft production cooperation. The Ulyanovsk plant manufactures sets of panels for all fuselage sections; the underbelly section and the auxiliary power unit (APU) compartment; all doors (11 doors for each aircraft); and the tail assembly (including the fin and stabilizer, complete with rudder and elevators).
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