FURTHER INVESTIGATIONS ON PRIMARY HELICOPTER CONTROL USING TRAILING EDGE FLAPS

Open Access
Author:
Duling, Christopher Thomas
Graduate Program:
Aerospace Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
March 23, 2009
Committee Members:
  • Dr Farhan Gandhi, Thesis Advisor
  • Farhan S Gandhi, Thesis Advisor
Keywords:
  • trailing edge flaps
  • swashplateless rotors
Abstract:
Integrated trailing edge flaps on a torsionally soft rotor show considerable promise for use in primary control of helicopters. This design enables the elimination of current swashplated designs, which are complex, subject to high drag in forward flight, heavy, and require considerable maintenance. One of the main obstacles facing the implementation of this concept is achieving trimmed flight within the actuator stroke and authority. Many of the current studies of this design predict required flap deflections that are beyond actuator capabilities. This study focuses on the effects of variable main rotor RPM on both flap input and power requirements to trim the vehicle. Expanding on previous work, this study uses a 2-DOF flap-torsion rigid blade model with a CFD database used to model the flapped blade section, a prescribed wake geometry for inflow modeling, and advanced UH-60 rotor and fuselage geometry in addition to variable main rotor RPM. The CFD database is analyzed by means of comparison to wind tunnel data and Thin Airfoil theory predictions. A parametric study of rotor pre-pitch and vehicle gross weights is performed in order to determine feasible rotor designs for achieving trimmed flight at a range of advance ratios and gross weights. The incorporation of CFD and the prescribed wake enables an analysis of main rotor power in comparison to a conventional UH-60 rotor. Variable main rotor RPM is explored as a means of reducing prediction trailing edge flapped deflection. Increased RPM is shown to reduce flap input requirements for the full range of gross weights for low and moderate airspeeds at the cost of increased main rotor power.