Wind Tunnel Tests and Further Analysis of the Floating Wing Fuel Tanks for Helicopter Range Extension. Volume 4. Coupled Wing-Fuselage Forced Vibration Analysis 45 Degrees Skewed Hinge
Abstract
Forced response calculations are performed on the H-21 helicopter equipped with floating fuel wings for the 0 and 100% fuel configurations. Using third harmonic shaft loads measured on an H-21 helicopter, and a deflection test obtained analytical model of the H-21 fuselage, the Associated Matrix method is employed to calculate the fuselage forced response. Results are presented as modal time histories of the fuselage for third harmonic azimuth positions of 0, 45, 90, and 135 degrees, and the resultant vertical and lateral responses at the cockpit floor during an rpm sweep. At 0% fuel, vertical response compares closely to that of the standard helicopter. Laterally, response increases with rotor speed, having an acceptable level at the lower range and higher amplitude at 268 rpm. For 100% fuel, the forced response calculations indicate a lateral natural frequency close to, but below, the 3 omega excitation at 250 rpm. In both the lateral and vertical directions, the calculated undamped vibration levels are high at lower speeds, but appear satisfactory at 268 rpm. Past experience indicates that predicted vibration levels near resonance are reduced by damping.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1961
- Accession Number
- AD0267343
Entities
People
- R. Gabel
- R. Ricks
Organizations
- Boeing Rotorcraft Systems