GB869864A - Method and apparatus for determining characteristics and mounting of rotor blades onrotary wing aircraft - Google Patents

Abstract

869,864. Rotary wing aircraft. UNITED AIRCRAFT CORPORATION. July 2, 1958 [July 25, 1957; Sept. 3, 1957], No. 21164/58. Class 4. Apparatus for ensuring that all blades of a rotary wing aircraft shall track uniformly comprises a rig 10 containing an engine 12 driving a rotor head 14 through a transmission 15. The rotor head includes conventional root sleeves 92 for the rotor blades, the sleeves being rotable about their axis in known manner by pitch-charging horns 94 and connecting rods 100, swashplate mechanism 28, 30 and pitch control rods 17. Each rod 100 comprises an internally threaded sleeve 102, a lower ball-ended extension 104 and a similar upper extension 106 which, together with the cooperating end of the sleeve is graduated to form a micrometer adjusting scale. Both extensions may be locked to the sleeve, the lower one being used for coarse adjustment of length, the upper one for fine adjustment in the manner to be described. A tool 150 which comprises two arms at right angles having connections respectively for attachment to the blade atatchment points on sleeves 92 and the connection of rods 17 with the swashplate non-rotatable element 28 is used to ensure that all sleeves 92 have the blade root attachment fittings set at the same incidence. This is done by setting the micrometer reading on the rods 100 at zero and adjusting the extensions 104. The rotor blades to be tested are then assembled on the rotor head and the rig set in motion to enable the blades to aerodynamically and dynamically balance, any variation of pitch required on individual blades to ensure uniform tracking being provided by adjustment of the micrometer element of rods 100. The resulting variation from zero of micrometer reading is marked on the individual blades so that when assembled on a production rotor head they may be given the same pitch setting as that determined on the test rig. In an alternative embodiment, the micrometer elements on rods 100 and the tool 150 are dispensed with and instead a protractor incorporating a spirit level is used to determine the pitch of each sleeve 92 after the blades have been tracked. The variation from a level or zero reading is marked on each blade and the pitch of individual blades is adjusted on the production rotor by rods 100 to set the blades at their appropriate pitch settings. Specification 713,352 and U.S.A. Specification 2, 759, 359 are referred to.