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Web posted Friday, December 28, 2001


photo: pplplaces

  Seated in one of the Autonomous Formation Flight Simulators is Anthony Thomas, a computer engineer, who works for the Simulation Hardware group of the Research Facilities Engineering Directorate. Some of the key team members to assist with the AFF simulator are, front row from left, Mike Najera, Barbara A. Smith, and Roger Felipe (Sparta, Inc.). In the back row, from left, are Jay Fantini, Marlin Pickett, and James Hernandez.
NASA Photo / Carla Thomas

Simulating safety:
Simulated cockpits help mitigate real problems before they occur

By Jay Levine
X-Press Editor

It's rare for a project to include two highly instrumented aircraft flying at the same time, but that is exactly what the Autonomous Formation Flight (AFF) Project does - in close formation.

For the project, a unique simulation was developed that allows the pilot "flying" the trail aircraft to "see" the wingtip of the lead aircraft in a 170-degree view of the sky.

The AFF Simulation System consists of two F/A-18 simulators that are connected to each other through the use of ScramNet. ScramNet is a shared memory technology used to transfer data between various devices at very fast speeds. Items built in-house such as the Cockpit Interface Unit (CIU) and the Simulation Electronic Stick (SES) are key to the operation of our simulators, said Anthony Thomas, a computer engineer working in the Simulation Hardware group of the Research Facilities Engineering Directorate.

The CIU is used to interface the cockpit to the simulation computer. If the pilot deploys the speedbrake, it is sensed at the CIU and sent to the simulation computer. The simulation computers then calculate the effects that the speedbrake has on the present state of the aircraft and respond accordingly.

The reverse also is true. The increased drag of the speedbrake would cause the airspeed of the aircraft to decrease, among other things, so the airspeed indicator should reflect the decrease. The SES simulates the flight stick and rudder pedals and electric motors are used instead of hydraulics. Because the simulator stick and rudders are electric, the force and damping can replicate the "feel" of a number of different aircraft while using the same design.

Although the wide screen graphics capability isn't new, its use in the AFF simulation is a first at Dryden.

"In the simulation, both aircraft can fly, with the trail aircraft able to see the lead aircraft and determine its position relative to that of the lead aircraft. In the actual aircraft, Global Positioning System (GPS) data is relayed back and forth between the two F/A-18s to help maintain the desired spacing of the two vehicles," Thomas said.

"The AFF simulation will be expanded to use a GPS constellation simulator to mimic the actual GPS satellites. The GPS data received from the constellation simulator will be relayed between each F/A-18 simulator in the same manner as the actual aircraft. The simulation will be very realistic because we will be using the exact same equipment as that onboard the two aircraft. The only difference is that the simulator will use simulated GPS satellites instead of the actual GPS satellites. Today's GPS simulators are very accurate, which makes them very well suited for the task," he explained.

Jeff Ray, who works graphics issues for the simulators, first was interested in the wide screen graphics capability when a unique proposal for an X-31 simulation arose. The proposed X-31 simulator had requirements for out-the-window views during high-angle-of-attack maneuvers. Basically, the pilot needed to see out the sides of the aircraft as well as out over the nose.

"During our search for solutions to the X-31 graphics requirement we discovered the GVR-120E, a specialized graphics system, manufactured by Panoram Technologies in Sun Valley, Calif. The system was very close to what we needed but unfortunately the X-31 simulation requirement went away and we dropped the idea. About three years went by before the AFF project arrived with requirements for two F/A-18 simulators to be flown in formation," Thomas said.

"One of the first things that popped into my head that would enhance the capability of the AFF simulation was to use a wide field-of-view graphics system for visual tracking. Being kind of a packrat, I was able to pull up the information from the X-31 graphics system research from my files and present the information to Rob Binkley, my branch chief, and the AFF Project Manager Gerard Schkolnik and AFF Chief Engineer Brent Cobleigh. After further research with all the vendors I could find, it was determined that Dryden's new GVR-120E graphics system was the right tool for the right job," he explained.

"The beauty of the GVR-120E system is the software and hardware basically take care of the graphics system. What we do is pipe in the video from our simulation computer and the graphics system does the rest. As far as the simulation computer is concerned it just has a desktop that is 3200 pixels by 1024 pixels in size. The hardware and software of the GVR system itself does the actual visual blending. There is a 25 percent overlap in the graphics of the three projectors. The family jewels of the system are how that blending is accomplished so you can't see that overlap. We do not have to deal with the constant physical aligning of components as we saw on other systems. It keeps the operation quite smooth. It's very nice," Thomas said.

Most of what the pilots see in the simulated cockpit is very similar to what they see in the real aircraft. The F/A-18 is well simulated. The basic F/A-18 simulator consists of actual digital display indicators, heads-up display with upfront controller and engine monitoring instruments. The digital data indicator (DDI) displays items like airspeed, altitude, alpha and Mach numbers. Real mission computers and control converters also are used, Thomas said.

In addition, the simulator has hardware-in-the-loop capability and can be connected to the F/A-18 Ironbird. The Ironbird is an aircraft that does not fly, but responds to commands sent to it through the hardware-in-the-loop simulation. In other words, when the simulator inputs that actuators are moving, the corresponding flight control surface on the Ironbird moves too.

For example, during testing of electro-mechanical actuators on another project, the Ironbird aided in detecting behavioral issues of the actuators while on the ground that would not have been seen until the actual flight research mission. It was only because the actuator thought it was flying under the actual aerodynamic loads that the behavioral issues surfaced.

And the simulations can do a number of items.

"The simulation can be utilized to test new flight control computers, test modifications to the control laws and actually change the flight characteristics of the aircraft by allowing the researcher to change gains and scaling parameters on the fly. It's nice to be able to make modifications and see the results quickly and safely," Thomas said.

Simulations meet a number of needs.

"A main purpose is safety. If the researcher collects data to improve systems through simulation, he or she is making it safer when researchers get to the real world situation. Simulation duplicates the research environment without risking lives or equipment," he said.

Production Support Flight Control Computers (PSFCC) are research flight control computers that allow us to change characteristics of how the airplane behaves. The minute something goes wrong it reverts back to the standard control laws, Thomas explained.

Some of Thomas' team members have played important roles in the development of the AFF simulators. Dryden civil servants include Brian Barr, Jay Fantini, James Hernandez, Mike Najera, Marlin Pickett, Barbara Smith, Jeff Ray and Rao Vanguri. Contractor contributors include Jeremy Gebro, Mike Guajardo, Emil Machac, Don Peddicord and Craig Schultz, all Woodside Summit Group employees.

 

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Modified: May 31, 2001

 

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