• Version
• 109 Downloads
• 1.46 MB File Size
• 1 File Count
• January 31, 2017 Create Date
• January 31, 2017 Last Updated

National Advisory Committee for Aeronautics, Technical Notes - Effects of Airplane Flexibility on Wing Strains in Rough Air at 5,000 Feet as Determined by Flight Tests of a Large Swept Wing Airplane

A flight investigation has been made on a large swept—wing bomber
airplane in rough air at 5,000 feet to determine the effects of wing
flexibility on wing bending and shear strains. In order to evaluate the
overall magnitude of the aeroelastic effects on the strains and their
variation with spanwise location, amplification factors defining the
ratio of the strains in rough air to the strains expected for a "rigid"
and "quasi-rigid“ airplane were determined. The results obtained indi-
cate that the aeroelastic effects are rather large, particularly at the
outboard stations. The effects of dynamic aeroelasticity appear to
increase the strains from O to 170 percent depending upon the spannise
station. 0n the other hand, the relieving effects of static aero-
elasticity appear to reduce the strain amplification in rough air by a
significant amount.

The stresses that develop in aircraft structures in flight through
turbulent air are, in many cases, strongly influenced by aeroelastic
effects. In the study of these aeroelastic effects, flight-test studies
have been made on several unsweptawing airplanes that have been classified
from "rather stiff" to "rather flebele" (refs. 1 to 1+) . Analytical
methods have also been developed in references 5 to 7 for calculating the
structural response of unswept—wing airplanes to atmospheric turbulence.
The results obtained in such calculations show good correlation with the
results of flight—test studies for the unsweptdwing airplanes so far
considered.

The response of sweptswing airplanes in rough air involves a number
of complications not present in the case of unsweptewing airplanes. These
complications are due principally to the increased importance of torsion
for swept-wing airplanes. This torsion in turn results in significant
effects on both the airplane aerodynamics and stability.