Analysis of the Helicopter Emergency Ditching System Attachment Elasticity Effect on the Work Capacity and Splashdown Process Parameters

Aeronautical and Space-Rocket Engineering


Аuthors

Gontsova L. G.1*, Nedelko D. V.1, Safiullin A. F.2

1. Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI), 1, Zhukovsky str., Zhukovsky, Moscow Region, 140180, Russia
2. Kazan Helicopters, 14, Ulitsa Tetsevskaya, Kazan, 420085, Russia

*e-mail: lg1617@mail.ru

Abstract

A helicopter emergency ditching is an event requiring thorough analysis and preparation. To enhance rescue operations safety and effectiveness, detailed studies of the helicopter-water surface contact dynamics are essential. This article examines the of finite element analysis application to this process modeling, with emphasis on the effect of elastic properties of the emergency ditching system ballonets.
The authors consider the possibility of creating a combined model incorporating both finite volume method for simulating a two-media (air-water) problem and finite element method for attachment modeling of the emergency ditching system structure to the helicopter fuselage. The study examines a helicopter with two cylindrical emergency ditching system ballonets.
For the ditching full-fledged analysis the helicopter model was integrated into the water pool model discretized into the Euler volumetric elements. This approach allows accurate accounting for the water hydrodynamic effect on the helicopter.
Two models were developed to study the emergency ditching system elements impact on the ditching dynamics:
1. A model with rigidly mounted rigid ballonets. In this model, the balloons were considered as completely rigid bodies, incapable of deformation or rotation around their attachment points under the impact of hydrodynamic forces. This simplified model allows evaluating the impact of the other factors, but does not account for the actual behavior of elastic balloons.
2. A model with elastic mounting of elastic balloons. This model is much more realistic. The ballonets are being modeled as elastic elements capable of deformation (compression) and rotation around their attachment points under the impact of hydrodynamic loads. The pressure inside the ballonets is being accounted for in the model as well, which affects their rigidity and deformation upon contact with water. This model allows for a more accurate evaluation of the emergency ditching system behavior while a ditching.
The overloads analysis demonstrates that with the elastic ballonets elastic mounting, the overload is slightly higher than that for the rigid ballonets with rigid mounting. However, in the case of the elastic mounting, only one overload peak was being observed, while in the case of rigid mounting, two peaks were recorded. This difference is stipulated by the ditching dynamics of both options. With the first option, an initial peak in g-force is being observed when the rigid ballonets touch the water, and a second peak occurs during their further submersion and the fuselage impact with the water surface. With the second option, due to the mountings and the ballonets themselves elasticity, they rotate around the connection axis upon entering the water, preventing the impact of the balloons on the water, as occurs in the first option. However, after the elastic balloons interaction with the liquid, the velocity keeps on increasing, and the peak g-force occurs upon the fuselage impact with the water. This explains the higher g-force in the option with elastic mounting of the elastic ballonets.
It was found that the simulation results obtained by the model with the elastic mounting of the elastic ballonets are more accurate and allow for the design optimization of the emergency ditching system to enhance safety of the crew and passengers in the emergencies. Further research efforts may be directed at refining the material models, with account for the effect of waves and other factors that increase the simulation realism.

Keywords:

helicopter emergency ditching, finite volume method, elastic ballonets, rigid ballonettes, finite element method

References

  1. Nedel’ko DV. Calculation assessment of the helicopter hydrodynamic loading level at ditching. Aviation Industry. 2012(4):13–17. (In Russ.).
  2. Nedel’ko DV, Mukhametshin TA, Safiullin AF, et al. Investigation into the possibility to employ finite element method to solve applied problems of a helicopter hydrodynamics. Aviation Industry. 2014(2):7–11. (In Russ.).
  3. Nedel’ko DV, Safiullin AF, Gontsova LG. The use of finite element method for calculation of aquaplaning of the aiframe similar to tilting plate shape. Aviation Industry. 2018(2):8–11. (In Russ.).
  4. Nedel’ko DV, Safiullin AF. Finite element method application for determining water landing parameters of airplanes and helicopters of various types. Aerospace MAI Journal. 2018;25(2):61–72. (In Russ.). URL: https://vestnikmai.ru/publications.php?ID=92991
  5. Dytran 2016 Theory Manual. MSC.Software Corporation user documentation. р. 161. 
  6. Bensh L, Shigunov V, Beuck G, et al. Planned ditching simulation of a transport airplane. KRASH Users’ Seminar (07-10 January 2001; Phoenix/Arizona).
  7. Hua C, Fang C, Cheng J. Simulation of fluid-solid interaction on water ditching of an airplane by ALE method. Journal of Hydrodynamics, Ser. B. 2011;23(5):637–642. DOI: 10.1016/s1001-6058(10)60159-x
  8. Kozelkov A, Pogosyan MA, Strelets DYu, et al. Application of mathematical modeling to solve the emergency water landing task in the interests of passenger aircraft certification. Aerospace Systems. 2021;4(1):75–89. DOI: 10.1007/s42401-020-00082-7
  9. Qu Q, Hu M, Guo H, et al. Study of Ditching Characteristics of Transport Aircraft by Global Moving Mesh Method. Journal of Aircraft. 2015;52(5):1550–1558. DOI: 10.2514/1.c032993
  10. Wang J, Lyle K. Simulating Space Capsule Water Landing with Explicit Finite Element Method. 48th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference (April 23-26, 2007; Honolulu, Hawaii). DOI: 10.2514/6.2007-1779
  11. Hammani I. Improvement of the SPH method for multiphase flows application to the emergency water landing of aircrafts: application to the emergency water landing of aircrafts. PhD thesis. L'école Centrale De Nantes; 2020. 145 p.
  12. Seddon CM, Moatamedi M. Review of water entry with applications to aerospace structures. International Journal of Impact Engineering. 2006;32(7):1045–1067. DOI: 10.1016/j.ijimpeng.2004.09.002
  13. Hughes K, Vignjevic R, Campbell J, et al. From Aerospace to Offshore: Bridging the Numerical Simulation Gaps—Simulation Advancements for Fluid Structure Interaction Problems. International Journal of Impact Engineering. 2013;61:48–63. DOI: 10.1016/j.ijimpeng.2013.05.001
  14. Karman TH. The impact of seaplane floats during landing. Report No. NACA-TN-321, 1929.
  15. Wagner H. Über Stoß- und Gleitvogänge an der Oberfläche von Flüssigkeiten. ZAMM (Zeitschrift für angewandte Mathematik und Mechanik) - Journal of applied mathematics and mechanics. 1932;12(4):193-215. DOI: 10.1002/zamm.19320120402
  16. Mayo WL. Analysis and modifications of theory for impact of seaplanes on water. Report No. NACA-TR-810, 1945.
  17. Leigh BR. Using the momentum method to estimate aircraft ditching loads. Canadian Aeronautics and Space Journal. 1988;34:162-169.
  18. Soding H. Berechnung der Flugzeugbewegung beim Notwassern. Thecnische Universitat Hamburg-Harburg Arbeitsbereiche Schiffbau, Bericht Nr. 602. 1999.
  19. Shigunov V. Berechnung der Flugzeugbewegung beim Notwassern. Thecnische Universitat Hamburg-Harburg, Arbeitsbereiche Schiffbau, Bericht Nr. 608. 2000.
  20. Bensh L, Shigunov V, Soding V. Pressure distribution during water impact for A340 and A3XX // CRAVHI Reference number EDB-1675/01, 2001.
  21. Safiullin AF. Calculation of hydrodynamic loading of airplanes and helicopters in the process of driving using the finite element method. PhD thesis. Kazan: KNRTU-KAI; 2018. 172 p. (In Russ.).
  22. Katsuno ET, Tödter S, Neugebauer J, et al. Investigating Helicopter Ditching and Flotation Stability Using CFD: Analysis of Mass Configurations, Door Openings, and Floater Conditions. 50th European Rotorcraft Forum (10-12 September 2024; Marseille, France). 

mai.ru — informational site of MAI

Copyright © 1994-2026 by MAI