To enable moderate-to-large helicopter rotor system testing in the National Full-Scale Aerodynamics Complex (NFAC), NASA and the U.S. Army have recently completed the development of a new research test capability. The Large Rotor Test Apparatus (LRTA) was designed and built by Dynamic Engineering, Inc. to operate helicopter rotors at thrusts up to 52,000 pounds. Similar to the Rotor Test Apparatus the LRTA is a special-purpose drive and support system for operating helicopter rotors.
The primary design features of the LRTA include the following: a) a drive system powered by two 3000 horsepower motors, b) a five-component rotor balance to measure steady and unsteady rotor hub loads, along with an instrumented flex-coupling to measure rotor torque, c) a six-component fuselage load-cell system to measure steady fuselage loads, d) a complete rotor control system (including console) with primary and higher harmonic control, and e) an output shaft assembly with a replaceable upper shaft for mating with a multitude of different rotor systems. Details on some of the design and operational aspects of the LRTA can be found here.
The current maximum capabilities of the LRTA are as follows:
Normal Force - 52,000 lb
Shear Force (Resultant) - 15,000 lb
Moment (Resultant) - 125,000 ft-lb (at the balance moment center)
Torque - 165,000 ft-lb
Rotational Speed - 320 RPM
Power - 4500 HP (an NFAC MG set limit; LRTA limit is 6000 HP)
Actuator Loads - 5000 ± 6000 lb
Note that the maximum resultant hub moment is dependent upon the installed hub height above the balance moment center. Also note that these maximum capabilities represent the limits of the primary LRTA structure, with the exception of the replaceable upper shaft . For most rotor test programs, this upper shaft will have significantly less load-carrying capability than the rest of the LRTA.
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