A Typical Simulation Development
by Chris Sweeney

October 17, 1997

My job involves putting different pieces of an aircraft together on a computer. If we are working with an aircraft that has not been simulated at the Vertical Motion Simulator (VMS), a brand new architecture, we receive a mathematical description of the model. This includes an aerodynamic database from wind tunnel tests, block diagrams describing the flight control system, equations describing the guidance and navigation system of the aircraft, and models of whatever means of propulsion the aircraft has, an engine for an airplane, or a rotor in the case of a helicopter.

We take all the information and write, in FORTRAN computer language, the software code to describe the aircraft, flight controls, guidance system, navigation systems, and propulsion system. We reformat the aerodynamic data to read out during the real-time simulation. We check the correctness of each separate system first, then integrate the code of all the systems for the aircraft. We do a full closed-loop test of the entire aircraft to make sure the computer model works the way the real aircraft or the potential aircraft is designed to work. This part of the project can take 6-8 months for a new aircraft and 2-3 months for an aircraft we have already simulated.

Next, we integrate the model into the lab and the cab, the VMS "cockpit" or flight deck, of our aircraft making sure the controls the pilot will use work correctly in our model, so when the pilot moves the stick, the aircraft responds correctly. We make sure we have simulated the sound the pilots would hear and the out-the-window scene the pilots would see if they were looking into the real world. We check the displays the pilot looks at in the flight deck and the Head Up Display (HUD) if the aircraft has one. When all of these parts of the simulation have been integrated, we run some more flight checks, then the pilots come in and fly. They check the model to ensure it represents the real aircraft, and then for six weeks we run the simulation itself.

Pilots and researchers come and fly various tasks depending on the research goals for the project, and we collect data for the researchers to analyze. Post simulation documentation is the next step. This includes report writing and collecting all the pertinent information on how and why we did certain things in the model. This documentation fills a couple of binders and is available in case the same aircraft needs to be simulated again. Another flight simulation engineer can then reuse the applicable parts of the model.