Journal of Ornithology

, Volume 146, Issue 3, pp 191–199 | Cite as

Yaw stability in gliding birds

Original Article

Abstract

A new concept for describing the yaw stability in gliding birds is presented. This concept introduces dynamic stiffness in yaw as an appropriate indication of stability. Other than the conventional metric of static yaw stability given by the gradient of the aerodynamic yawing moment with respect to the sideslip angle, the dynamic stiffness does not only provide a qualitative indication of stability but also a precise quantitative measure of the restoring action in the yaw axis. With the use of scaling relations, it is shown that the dynamic stiffness of birds is sufficiently high though their static yaw stability may be very small. The underlying mechanism is that the yaw moment of inertia is more reduced with a decrease in size than the restoring aerodynamic moment. Reference is made to the yaw stability in aircraft and related flying qualities requirements. Thus, numerical values are derived which can be used as a standard of comparison providing a rating basis for the dynamic yaw stiffness in small flying objects, like birds. Furthermore, it is shown that the wings of birds produce yawing moments due to sideslip so large that a sufficiently high level of dynamic yaw stiffness can be achieved. From the results derived in this paper, it may be concluded that birds—unlike aircraft—need no vertical tail for yaw stability.

Keywords

Birds Gliding Stability Yaw 

References

  1. Brown RHJ (1963) The flight of birds. Biol Rev 38:483–487Google Scholar
  2. Brüning G, Hafer X, Sachs G (1993) Flugleistungen, 3rd edn. Springer, Berlin Heidelberg New YorkGoogle Scholar
  3. Bußmann K, Kopfermann K (1944) Sechskomponentenmessungen an Rechteckflügeln mit verschiedenem Seitenverhältnis. Zentrale für wiss. Berichtswesen, Berlin-Adlershof, TB 11, No. 8, pp 245–251Google Scholar
  4. Cvrlje T, Breitsamter C, Laschka B (2000) Numerical simulation of the lateral aerodynamics of an orbital stage at stage separation flow conditions. Aerospace Sci Technol 4:157–171CrossRefGoogle Scholar
  5. Etkin B, Reid LD (1996) Dynamics of flight—stability and control, 3rd edn. Wiley, TorontoGoogle Scholar
  6. Gronau K-H (1956) Theoretische und experimentelle Untersuchungen an schiebenden Flügeln, insbesondere Pfeil- und Deltaflügeln. Jahrbuch 1956 der WGL, pp 133–150Google Scholar
  7. Hafer X (1957) Untersuchungen zur Aerodynamik der Flügel-Rumpf-Anordnungen. Jahrbuch 1957 der WGL, pp 191–207Google Scholar
  8. Herzog K (1968) Anatomie und Flugbiologie der Vögel. Gustav Fischer, StuttgartGoogle Scholar
  9. Hummel D (1991) On the aerodynamics of the tail in birds. Proc Int Ornithol Congr 20(2):730–736Google Scholar
  10. Hummel D (1992) Aerodynamic investigations on tail effects in birds. Z Flugwiss Weltraumforsch 16:159–168Google Scholar
  11. Jiang L, Moelyadi MA, Breitsamter C (2003) Aerodynamic investigations on the unsteady stage separation of a TSTO space transport system. Forschungsbericht FLM-2003/34, Lehrstuhl für Fluidmechanik, Abteilung Aerodynamik, Technische Universität München, December 2003Google Scholar
  12. Kirkpatrick SJ (1990) The moment of inertia of bird wings. J Exp Biol 151:489–494Google Scholar
  13. Krus P (1997) Natural methods for flight stability in birds. AIAA Paper AIAA 97–5653Google Scholar
  14. MIL-F-8785C (1991) Flying qualities of piloted airplanes MIL-HDBK-1797 (1997) Flying qualities of piloted aircraftGoogle Scholar
  15. Nachtigall W (1985) Warum die Vögel fliegen. Rasch und Röhring, Hamburg-ZürichGoogle Scholar
  16. Norberg UM (1990) Vertebrate flight. Springer, BerlinGoogle Scholar
  17. Pennycuick CJ (1975) Mechanics of flight. In: Farner DS, King JR (eds) Avian biology, vol V. Academic Press, New York, pp 1–75Google Scholar
  18. Pennycuick CJ (1983) Thermal soaring compared in three dissimilar tropical bird species, Fregata magnificens, Pelecanus occidentalis and Coragyps atratus. J Exp Biol 102:307–325Google Scholar
  19. Rayner JMV (1988) Form and function in avian flight. Curr Ornithol 5:1–66Google Scholar
  20. Schlichting H, Truckenbrodt E (2001) Aerodynamik des Flugzeuges, 3rd edn, vol 2. Springer, Berlin Heidelberg New YorkGoogle Scholar
  21. Taylor GK, Thomas ALR (2002) Animal flight dynamics II. Longitudinal stability in flapping flight. J Theor Biol 214:351–370CrossRefPubMedGoogle Scholar
  22. Thollesson M, Norberg UM (1991) Moments of inertia of bat wings and body. J Theor Biol 158:19–35Google Scholar
  23. Thomas ALR, Taylor GK (2001) Animal flight dynamics I. Stability in gliding flight. J Theor Biol 212:399–424CrossRefPubMedGoogle Scholar
  24. Van den Berg C, Rayner JMV (1995) The moment of inertia of bird wings and the inertial power requirement for flapping flight. J Exp Biol 198:1655–1664 0 Weissinger J (1943) Ergänzungen und Berichtigungen zur Theorie des schiebenden Flügels. Jahrbuch der deutschen Luftfahrtforschung (Vorabdruck). Zentrale für wiss. Berichtswesen, Berlin-Adlershof, TB 10, No. 7, 6pGoogle Scholar

Copyright information

© Dt. Ornithologen-Gesellschaft e.V. 2005

Authors and Affiliations

  1. 1.Institute of Flight Mechanics and Flight ControlTechnische Universität MünchenGarchingGermany

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