AFRL's Total In-Flight Simulator (TIFS), a Convair C-131 Samaritan aircraft, entered service on March 22, 1955. The C-131 aircraft had performed various transport operations for approximately a decade up to that point, and the Air Force (AF) Flight Dynamics Laboratory—now AFRL— subsequently chose it for a very special mission: developing next-generation air vehicles.

Performing extensive modification, AFRL transformed the airplane into TIFS, a one-of-a-kind simulator that engineers can program to simulate virtually any type of air vehicle, in flight, with six degrees of freedom. When most other C-131s left the AF's active fleet in the late 1970s, TIFS was just beginning to support programs such as the space shuttle, B-1 and B-2 bombers, and numerous private sector tests and development efforts.

Figure 1. TIFS simulation cockpit configuration

AFRL owns TIFS, and Calspan Corporation operates it through a Cooperative Research and Development Agreement. Mr. Norman Weingarten, Calspan's in-flight simulation operations manager, began his involvement with this airplane while working as a project engineer during the extensive modification effort that produced TIFS. "It's more realistic than a ground simulator, because you are flying an actual airplane in real-world motion with realworld visuals," Mr. Weingarten explains.

In fact, pilots moving from TIFS to an actual aircraft frequently remark that the aircraft handles exactly the way that TIFS simulated its handling. Further, because TIFS allows pilots to operate during simulated failures, it provides them the opportunity to study and react to dangerous situations in a safe vehicle that can instantly revert to normal control. Mr. Weingarten recognizes the advantage this provides: "Often, you don't want to fail a system on an [actual] airplane, even in a test mode, because it might be too dangerous to fly [as a result]. Our airplane can do that safely."

Figure 2. TIFS ASTTA configuration

TIFS' many benefits extend to engineers as well. Normally, a test aircraft will accumulate several hundred hours of flight data, but "on the ground, all engineers [can] do is look at computer outputs, time histories, graphs, and displays. But actually being up there and experiencing all of the little oscillations and responses brings a sense of reality to the test. Flying helps engineers to appreciate the problems that they are investigating," Mr. Weingarten asserts.

Highly versatile, TIFS uses two interchangeable noses to perform a variety of tests. Depending upon the type of research, engineers can switch between a simulation cockpit nose (see Figure 1) and an avionics nose (see Figure 2) called the Avionics System Test and Training Aircraft (ASTTA) configuration. In the simulation cockpit configuration, a test pilot flies TIFS, which duplicates the characteristics of a simulation model programmed into its computer. During flight tests, the computer adjusts TIFS' handling characteristics by hydraulically actuating the plane's extra control surfaces, including its side-force surfaces and direct-lift flaps. The ASTTA configuration lets TIFS perform avionics testing using onboard radar, infrared electrooptical detection systems, inertial navigation, and a Global Positioning System. For both configurations, TIFS retains its safety cockpit, located above and behind the nose. A pilot stands by to take control and override the simulation, if necessary.

TIFS has supported a variety of programs. For instance, it aided National Aeronautics and Space Administration (NASA) researchers in developing a cost-effective, next-generation supersonic transport. Essentially, it helped the NASA team evaluate the feasibility of landing without forward visibility and relying on sensors and displays alone. In addition, AFRL scientists used TIFS to evaluate an autonomous guidance and control system for Boeing's X-40 Space Maneuvering Vehicle.1 Recently, TIFS supported an ITT Industries technology known as ANGEL: Airborne Natural Gas Emission LiDAR (Light Detection and Ranging). ANGEL uses LiDAR lasers to detect natural gas pipeline leaks and identify their location within 10 ft of the source, from a distance up to 1,000 ft in the air. (See inset for a listing of other TIFS-supported programs.)

TIFS' flexibility significantly expands its capacity to support a wide variety of programs. In addition to changing nose configurations, engineers can easily modify TIFS to carry project-specific test components such as sensors, computers, or displays. Each project is different; further, the evolving requirements unique to this type of research have proven the need for implementing continuous updates. TIFS' simulation cockpit configuration most recently gained a new nose cap and canopy, adding room to accommodate additional test equipment comprising a new instrument panel, side and center consoles, a rudder pedal, throttle feel systems, additional sensors, and displays including a Silicon Graphics® computer and a high-definition television camera.

Major Vincent Raska, TIFS project manager, summarizes the resource: "It's not as expensive as flying a jet airplane, and its availability for testing is often better than [that of] other aircraft such as the C-17, C-5, or KC-135. Competing for a test range can be a costly and time-consuming ordeal, but Calspan is already approved by the Federal Aviation Administration to fly in many test areas." Maj Raska hopes TIFS will be around for many years to come. "I am all about recycling and reusing," he states. "Despite being older, [TIFS] has a lot of capability. It is very versatile and flexible. It is one of a kind." Based in Niagara Falls, New York, TIFS frequently makes trips to different test locations and is available to anyone in government or industry requiring specialized in-flight test capabilities.

Ms. Melissa Withrow (CACI), of the Air Force Research Laboratory's Air Vehicles Directorate, wrote this article. For more information, contact TECH CONNECT at (800) 203-6451 or place a request at http://www.afrl.af.mil/techconn/index.htm. Reference document VA-H-05-04.

Reference

  1. Doman, D. and Withrow, M. "Integrated Adaptive Guidance and Control." AFRL Technology Horizons®, vol 5, no 6 (Dec 04): 47-48.