Simulation Model Development for Icing Effects Flight Training

ABSTRACT A high-fidelity simulation model for icing effects flight training was developed from wind tunnel data for the DeHavilland DHC-6 Twin Otter aircraft. First, a flight model of the un-iced airplane was developed and then modifications were generated to model the icing conditions. The models were validated against data records from the NASA Twin Otter Icing Research flight test program with only minimal refinements being required. The goals of this program were to demonstrate the effectiveness of such a simulator for training pilots to recognize and recover from icing situations and to establish a process for modeling icing effects to be used for future training devices. INTRODUCTION In response to a 1997 White House Initiative to reduce aviation accidents, NASA formed the Aviation Safety Program (AvSP) in 1999. The seven-year program has been tasked to reduce aviation accident rates by 80% by 2007 and by 90% by 2017. Accident and incident reports were analyzed to focus efforts on areas of highest return. These studies showed that 13% of all weather-related accidents were due to airframe icing. To address the icing hazard, NASA has developed a number of tools to supplement pilot training. To date, these tools consist of educational & training videos and computer-based training CD-ROMs. However, a task within the System Wide Accident Prevention Project of AvSP is currently underway to develop a flight simulator that incorporates icing effects for pilot training applications. The purpose of the Pilot Simulator Training for Aircraft Icing Effects (PSIM) activity is to provide pilots with ground-based training facilities that provide a realistic simulation of in-flight icing encounters. This capability will provide pilots a pre-exposure to the adverse effects of icing on airplane performance, stability and control. It will serve as a tool for initial and recurrent pilot training to provide awareness of the consequences of an icing encounter and the knowledge of how to best manage potential adverse maneuvers that may result from icing-induced loss of control. In order to establish this icing effects flight training capability, NASA Glenn Research Center teamed with Bihrle Applied Research and the Wichita State University in 1998 to develop a flight simulation demonstrator. The work also establishes a methodology for developing flight simulators that incorporate icing effects that can be used by flight training organizations, operators, airframe manufacturers, and pilots in safety training programs. A typical application for such a flight modeling process would be to add the capability to existing flight trainers. In such a case, a baseline flight model would already exist. This effort focuses on the steps needed to augment a baseline model with appropriate data to model the effects of icing. In the case of the Twin Otter, no appropriate baseline simulation was available; therefore, as an additional step, one was developed and validated as part of the effort. It was important to have both baseline and iced simulations from a pilot training standpoint, so that a pilot could be exposed to the juxtaposition of both conditions. Starting from the baseline simulation also allowed researchers to assess, in an incremental fashion, the level of modification and steps required to implement icing effects to an existing baseline. To accomplish this, the PSIM effort was designed to proceed in three phases, a baseline model development and validation (BASELINE), a horizontal tail icing model development and validation (ICE01), and a full aircraft icing model development, assessment, and validation (ICE02). Once a baseline simulation structure was established, each phase of the flight model development focused primarily on the development of aerodynamics models and control system models. The basis for each of the developmental aerodynamics and control models was low speed wind tunnel data. These data were used to populate table driven models of aerodynamics forces, moments, and hinge moments. The models were then validated with flight data. To complete the validation, physics-driven modifications are made to the raw wind-tunnel data and then reintroduced to the simulation. The revised model is then reevaluated against an independent data set until appropriate acceptance criteria are met. In this effort, modifications applied to the