Experimental study of the aircraft forced vibrations while the engine blade break-away

Аuthors

Pronin M. A.^*, Ryabykina R. V.^**, Smyslov V. I.^***

Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI), 1, Zhukovsky str., Zhukovsky, Moscow Region, 140180, Russia

*e-mail: pronin_m@pochta.ru
**e-mail: regina.leontjeva@gmail.com
***e-mail: smysl@mail.ru

Abstract

The presented article is a generalization of works relating to the ground reproduction of the force impacts on the aircraft structure, on the part of the engine with imbalance in case of the blade loss.

While ground testing the engine rotor does not rotate, and rotating force is formed by the fixedly installed vibration exciters. The immediate purpose of the experiment consists in frequency characteristics measuring, which associate the aircraft vibrations with the excitation force from the engine rotor imbalance. These characteristics are necessary for the computational dynamic scheme correction of the structure employed in loads computing in flight, possibly prolonged, while the blade break-away over the water surface. These computations are used for the aircraft safety evaluation while the blade loss.

The article presents the testing technique and facilities. The estimates of the modelling method applicability and its trustworthiness are given for the first time. The text is supplemented by the examples of real data of the tests.

The quantitative confirmation for the case of the ground experiment is given in the applicability esteems of the rotating inertial force reproduction by the harmonic forces stationary in space. At the same time, it was noted that the loads calculation while flight fluctuations, with a high level of the engine overloading, can not be based on either use of only relative acceleration of the blade, or the approximate theory of the gyroscope.

The circumstance of the experiment performing while the compulsory routine tests prior to its first flight was considered separately as practically the only possible for the experiment under consideration. The domestic tests on the aircraft with the engine blade loss modelling performed for the first time revealed the feasibility and possibility of their realization in conditions of dire time deficit prior to the first flight.

The presented details and features of the technique allow apply them in the future in the practice of such tests by the design bureau itself.

The main result is substantiation and practical confirmation of the possibility of reproducing on the ground the forced oscillations of an airplane after the blade loss, and while the mandatory regular modal tests.

Keywords:

aircraft vibrarions, blade loss, engine imbalance, experimental study

References

1. Kuznetsov O.A., Smyslov V.I. Trudy TsAGI, issue 2714, Moscow, Izdatel’skii otdel TsAGI, 2013, 34 p.

2. Aviatsionnye pravila. Chast’ 33. Normy letnoi godnosti dvigatelei vozdushnykh sudov (Aviation regulations. Part 33. Airworthiness standards of aircraft engines), Moscow, Aviaizdat, 2004, 48 p.

3. Normy letnoi godnosti grazhdanskikh samoletov SSSR (Airworthiness standards of the USSR civil aircraft), Moscow, Mezhduved. komis. po normam letnoi godnosti grazhd. samoletov i vertoletov SSSR, 1984, 464 p.

4. Aviatsionnye pravila. Chast ’ 25. Normy letnoi godnosti samoletov transportnoi kategorii (Aviation regulations. Part 25. Airworthiness standards of transport category aircraft), Moscow, Aviaizdat, 1994, 267 p.

5. Engine Windmilling Imbalance Loads - Final Report, dated 1 July 1997. Aviation Rulemaking Advisory Committee (ARAC) recommendations to the FAA.

6. Certification Specifications and Acceptable Means of Compliance for Large Aeroplanes CS-25. Amendment 8, 18 December 2009.

7. JAA NPA 25E-306: Sustained Engine Imbalance, published for consultation from 1 February – 1 May 2002NPA 2007-15 24 Oct 2007 Engine & Auxiliary Power Unit (APU) failure loads and sustained engine windmilling, 157 p.

8. Vibratsiya i udar. Izmerenie obshchei vibratsii i otsenka ee vozdeistviya na cheloveka. Chast’ 1. Obshchie trebovaniya. GOST 31191.1-2004. ISO 2631-1:1997 (Vibration and shock. Measurement and evaluation of human exposure to whole-body vibration. Part 1. General requirements. State Standard 31191.1-2004. ISO 2631-1:1997), Moscow, Standartinform, 2008,  28 p.

9. Ivanteev V.I., Kuznetsov O.A., Emel’yanov V.I., Politov V.V., Steba M.A. Rukovodstvo dlya konstruktorov, vol. 3, book 1, issue 7. Moscow, RDK TsAGI, 1980, p. 73.

10. Kuznetsov O.A., Orlova T.I. Trudy TsAGI, issue 2675. Moscow, TsAGI, 2007, pp. 85-90 (351 p.).

11. Kuznetsov O.A. Dinamicheskie nagruzki na samolet (Dynamic loads on the aircraft), Moscow, Fizmatlit, 2008, 264 p.

12. Kuznetsov O.A., Leontieva R.V. Dynamic loads on aircraft due to engine imbalance at blade off. Report IF-S5B. International Forum on Aeroelasticity and Structural Dynamics IFASD-2013 (Bristol, United Kingdom, 24-27 June 2013). Curran Associates, Inc. 2014, vol. 1, pp. 326-338.

13. Kuznetsov O.A., Smyslov V.I. Tekhnika Vozdushnogo Flota, 1996, no. 3-4, pp. 18-24.

14. Kuznetsov O.A., Smyslov V.I. Uchenye zapiski TsAGI, 1999, vol. 30, no. 3-4, pp. 139-150.

15. Lubrina P. Ground vibration experiments on large civil aircraft for engine imbalance purpose. International Forum on Aeroelasticity and Structural Dynamics IFASD- 2003 (24-27 June 2003, Amsterdam).

16. Leont’eva R.V. Procedure of ground vibration experiments on aircraft with simulating forces due to engine imbalance at blade loss. 29^th Congress of the International Council of the Aeronautical Sciences, St. Petersburg, September 7-12, 2014. Paper 0859.

17. Leont’eva R.V., Smyslov V.I. Uchenye zapiski TsAGI, 2016, vol. 47, no. 6, pp. 61-74.

18. Prodera modal analysis systems and software. Technical articles. URL: http://www.prodera.com/uk/prodera_ articles.htm

19. Lur’e A.I. Analiticheskaya dinamika (Analytical dynamics), Moscow, GIFML, 1961, 824 p.

20. Strelkov S.P. Mekhanika (Mechanics), Moscow, Nauka, 1975, 560 p.

21. Kolesnikov K.S. (ed.) Kurs teoreticheskoi mekhaniki (The course of theoretical mechanics), Moscow, MGTU im. N.E. Baumana, 2002, 736 p.

22. Vibratsii v tekhnike. T. 5 “Izmereniya i ispytaniya” (Vibrations in engineering. Vol. 5 “Measurements and testing”), Moscow, Mashinostroenie, 1981, pp. 330-348.

23. Entsiklopediya “Mashinostroenie”. T. IV-21 “Samolety i vertolety”, kn. 1 “Aerodinamika, dinamika poleta i prochnost’”” (Encyclopedia “Machine building”. Vol. IV-21 “Planes and helicopters”, book 1 “Aerodynamics, flight dynamics and strength”), Moscow, Mashinostroenie, 2004, 800 p.

24. Heylen W., Lammens S., Sas P. Modal Analysis. Theory and Testing. Leuven, Belgium, KUL Press, 1997.

25. Bykov A.V. III Nauchno-prakticheskaya konferentsiya molodykh uchenykh i spetsialistov “Issledovaniya i perspektivnye razrabotki v aviatsionnoi promyshlennosti”. Sbornik statei, Moscow, OKB Sukhogo, 2005, p. 527.

26. Bykov A.V., Parafes S.G., Smyslov V.I. Hardware and software tools for computational and experimental investigations of aircraft aeroelastic stability. Aerospace MAI Journal, 2009, vol. 16, no. 5, pp. 56-63.

27. LMS International, http://www.lmsintl.com/

28. Zharov E.A., Smyslov V.I. Trudy TsAGI, issue 2219, Moscow, TsAGI, 1984, pp. 60-74.