HPC MSU

HPC² Events

Determination of UH-1N Helicopter Flight Loads

When:February 8, 2013

Where:Seminar Room #2200, CAVS Building, Research Park

Seminar on February 8th- 3:00 PM
Speaker: Dr. Robert D. McGinty, Mercer University, Chief Mechanical Engineer- Mercer Engineering Research Center


Mercer Engineering Research Center (MERC) has been tasked to update and maintain the H-1 (“Huey”) Aircraft Structural Integrity Program (ASIP).  This involves update of the UH-1N ASIP and Force Management Plans, general engineering support in the form of structural and damage tolerance analyses (DTA), and the determination of flight loads in order to support the above programs and DTAs.

In order to determine flight loads, MERC instrumented a UH-1N aircraft with accelerometers and strain gages and executed a baseline flight loads survey, during which 50GB of data was gathered.  A finite element model (FEM) of the UH-1N was also developed and validated against static and dynamic loading data.  Together, the flight data and FEM permit the determination of cyclic flight loads that drive UH-1N vibrations and are primarily responsible for the initiation and propagation of cracks in the aircraft structure.

MERC combined Fourier analysis of the flight data with FE based modal analysis of the UH-1N structure to determine the driving cyclic loads at each vibration frequency, and it is this new method of determining flight loads that is the focus of this presentation.

The analysis procedure permits the determination of magnitude and phase (at each vibration frequency) of the driving forces at the main and tail rotors on a second-by-second basis.  The derived force data can then be combined with FEM modal analyses to predict load and stress oscillations for any point in the structure.  The time-based loads calculated for each maneuver can be used to derive load spectra for the aircraft, supporting damage tolerance analyses. It has been found that the loads oscillate most strongly at the second main rotor harmonic (10.8 Hz) and at the primary tail rotor harmonic (27.7 Hz).  The predicted aircraft vibration levels based on the computed loads are in excellent agreement with the measured data, having correlation coefficients of R2 = 0.90.

If you would like to arrange time to meet with Dr. McGinty, please contact Dr. Tom Lacy via e-mail at: Lacy@AE.MsState.edu.