Flight Test Measurement of Ship Airwake Disturbances Using Small-scale Rotorcraft

Open Access
Author:
Schafer, Sylvie Ann
Graduate Program:
Aerospace Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
May 07, 2015
Committee Members:
  • Joseph Francis Horn, Thesis Advisor
Keywords:
  • flight test
  • airwake
  • helicopter
  • gust identification
Abstract:
The maritime environment is one of the most challenging operating environments for helicopters. The vertical takeoff and landing capability that helicopters possess make then uniquely suited to operations based on ships, but there are many factors that make these operations complex. One of these factors is air flow variability, including winds near ships and over their flight decks. Currently, before helicopters can be considered safe to operate on specific types of ships, they must be rigorously tested to ensure that no problematic aerodynamic interactions between the two bodies are observed. Recent research on Virtual Dynamic Interface (VDI) seeks to use computational tools to mitigate the need for this flight testing. However, these computational tools must be validated. Current methods of validation include wind tunnel testing and full scale at-sea testing. This thesis presents a method of validating the VDI process and characterizing the ship airwake using a gust identification method. The thesis begins by considering a Linear Kalman Filter approach to gust identification. By utilizing an accurate model of the vehicle dynamics and several simple onboard measurements, the gust identification algorithm can be used to estimate the airflow. This research uses indoor testing of a small-scale rotorcraft to verify the performance of the algorithm. A nonlinear simulation model of the test helicopter vehicle dynamics is developed, and the model is verified using system identification flight tests. After the model is developed, the algorithm is tested by conducting indoor flight experiments using a fan for flow generation. The setup and results of the experiment are presented. The algorithm is partially successful: in some cases, the algorithm is able to adequately capture the fan gusts, but in other cases it grossly overestimates them. Future work includes improvements to the algorithm and testing setup, and ultimately testing of the algorithm using a small-scale rotorcraft at sea.