High Altitude Gust Criteria for Aircraft Design
Final rept. 17 Mar 69-16 Sep 70,
LOCKHEED-CALIFORNIA CO BURBANK
Pagination or Media Count:
The report consists of analysis of measurements made in HICAT flight program and described in reports issued in 1967 and 1968. Clear air turbulent regions in the altitude range 45,000 to 65,000 ft. varied in length from 1 to 115 nm. Power spectral density curves computed from data from the longer turbulent regions had slopes and scale lengths that varied over a relatively wide range. Composite spectra for altitude and topographic categories for the long turbulent regions had slopes of -1.25 to -1.55 for the vertical component, -1.50 to -1.70 for the lateral component, and -1.45 to -1.60 for the longitudinal component. The scale lengths were all above 8,000 ft. The standard deviations of the root-mean-square gust velocities increase significantly with increase in roughness of underlying terrain. The range in values is 0.9 to 3.4 ftsec. for the vertical component, 1.5 to 4.6 ftsec for the lateral component and 1.2 to 4.6 ftsec. for the longitudinal component. There was relatively little change with altitude. The minimum root-mean-square velocity to be considered turbulence varied 0.95 to 3.02 ftsec. if truncated spectra were used to establish basic definitions of turbulence.
- Atmospheric Physics