Modern commercial aircraft utilize flammable fluids—such as fuel, hydraulic fluids, and oils—in their design. Equipment failures or loss of system integrity can lead to leaks, increasing the risk of fire in technical compartments. To mitigate these risks, each compartment is equipped with drainage ports that channel fluids outside the fuselage.
As part of an extended certification program, Yakovlev specialists conducted a series of drainage system tests on the MC-21-310 (tail number 73055) at the Flight Test and Development Complex in Zhukovsky. The objective was to validate the effectiveness of flammable fluid removal and ensure compliance with current aviation safety standards, according to the United Aircraft Corporation’s press service.
Civil aircraft certification standards require mandatory verification of drainage system performance to prevent flammable fluids from contacting ignition sources, including engine air intakes and hot engine components. To assess the effectiveness of domestic solutions, test flights were conducted on August 21–22 and 28–29 using specially colored fluids that simulate real-world operating conditions.
A dye solution with density and viscosity similar to aviation fuel was used to simulate emergency leaks. The delivery system included five tanks with the colored fluid, a nitrogen tank for pressure maintenance, and a separate tank with dye for system flushing. The operator controlled the process from a dedicated panel, while all parameters were recorded by the onboard measurement system. Three drainage points were tested: two in the aft section and one near the wing center section.
During various flight phases—taxi, takeoff, landing, level flight, sideslip, thrust reversal, and braking—the safety of flammable fluid removal from designated fire-prone and potentially hazardous zones was evaluated. After each flight, surfaces potentially exposed to the colored fluid were inspected, with special attention to areas where fluid presence could pose a fire risk. If traces of fluid were found on critical components, further analysis was conducted, and design or operational documentation was updated as necessary.
The use of colored fluids provided clear and accurate identification of fluid migration paths, enhancing the reliability of test results. The trials concluded with the collection of data for reports to be submitted to relevant certification authorities. Based on the analysis, specialists will determine whether the drainage systems meet safety requirements.
The results of these tests form the basis for an objective assessment of the MC-21’s operational reliability under intensive commercial service. Robust drainage systems minimize the risk of undetected flammable fluid migration within structural cavities, which is essential for maintaining required fire safety levels throughout the aircraft’s lifecycle.
The technical implementation of these domestic solutions demonstrates the ability to integrate modern approaches into next-generation aircraft architecture. This ensures resilience to emergency situations and compliance with international civil aviation standards.
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