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Aircraft Response to Turbulence Including Wakes

  • John C. Houbolt

Abstract

The nature of atmospheric turbulence and the means for establishing aircraft response is reviewed, both from discrete-gust and spectral interpretations. Application is then made to the situation of wake turbulence encounter to show the nature and magnitude of the loads that result. Specific cases are treated, with encounters perpendicular to and parallel to the wake, to bring out the main parameters that are significant. General relations are also developed to show how the wake “gust” forces on the encountering airplane are related to the lift on the aircraft generating the wake. It is shown that normal loads in excess of 2 g’s may be produced by a perpendicular encounter of a wake vortex, and that uncontrollable rolling moments may be caused by encounters along the axis of a vortex.

Keywords

Vortex Core Core Radius Rolling Motion Wake Vortex Horseshoe Vortex 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Symbols

a

slope of the lift curve also radius of vortex core

A

aspect ratio also structural response parameter as used in σx = Aσw

b

wing span

c

wing chord

CL

lift coefficient

eA

moment arm to centroid of aileron lift

H(ω)

frequency response function

I

rolling moment of inertia

Kg

gust alleviation factor for discrete gust

spectral gust alleviation factor

Kv

alleviation factor for vortex

L

lift

m

aircraft mass

△n

incremental load factor

r

radial distance

so

nondimensional core radius, so = 2a/c

S

wing area

t

time

v

flight velocity

w

tangential velocity in vortex, also vertical gust velocity

wm

maximum tangential velocity

W

aircraft weight

z

vertical displacement

β

aileron deflection

Г

vortex strength

ε

aileron efficiency factor

μ

mass ratio, μ $=\frac{2w}{\text{apcgS}}$

ρ

air density

σ△n

r.m.s. value of incremental load factor

σw

r.m.s. value of vertical gust velocities

φ

roll displacement

φx(ω)

power spectrum of variable x

ω

circular frequency

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References

  1. 1.
    Houbolt, John C.: Gust Design Procedures Based on Power Spectral Techniques. Technical Report AFFDL-TR-67–74, August 1967.Google Scholar
  2. 2.
    Houbolt, John C.: Design Manual for Vertical Gusts Based on Power Spectral Techniques. Technical Report AFFDL-TR-70–106, July 1970.Google Scholar
  3. 3.
    Houbolt, John C. and Kordes, Eldon E.: Structural Response to Discrete and Continuous Gusts of an Airplane Having Wing-Bending Flexibility and a Correlation of Calculated and Flight Results. NACA Report 1181, 1954. (Supersedes NACA TN 3006; also contains essential material from TN 2763 and TN 2897.)Google Scholar

Copyright information

© Plenum Press, New York 1971

Authors and Affiliations

  • John C. Houbolt
    • 1
  1. 1.Aeronautical Research Associates of Princeton, Inc.USA

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