Orlando, FL--CAD and finite element analysis were critical to the Navy's integration of the LANTIRN (Low Altitude Navigation and Targeting for Night) system onto the F-14. Software enabled engineers at Lockheed Martin to retrofit a version of the system, used on the F-15E and F-16C and D fighters, to the F-14.
The original LANTIRN, a two-pod navigation and targeting system, allows fighter pilots to operate in daylight or in total darkness, and at altitudes beneath enemy radar detection for precision attack. For the F-14 system, engineers decided to use only the targeting pod.
The new pod design features a fully stabilized FLIR (Forward Looking InfraRed) imaging system for navigation and target recognition and a laser designator to guide smart weapons (see figure). Engineers also wanted to incorporate a related satellite positioning and Inertial Navigation System (GPS/INS) into the pod without rearranging existing components or interfering with installed wiring.
To accomplish this, they turned to engineering software packages--Pro/ENGINEER(reg) 3D modeling from Parametric Technology Corp. (PTC; Waltham, MA); I-DEAS(TM) Master Series by SDRC (Cincinnati) for most of the detailed modeling; and the Micro Cadam(TM) 2D design package from MICROCADAM (Los Angeles) to produce supporting documentation.
Subcontractor Litton supplied CAD drawings of its GPS/INS systems to engineers at prime contractor Lockheed Martin. These include the Inertial Targeting System, which consists of two units--the Inertial Measurement Unit (IMU), for measuring rates and attitude of the aircraft, and the processor. From these, engineers confirmed if the units would fit into the pod in accordance with clearance specifications.
"The only critical area of concern was mounting the IMU into the pod," says Ian Dyer, Lockheed Martin project engineer for the F-14 LANTIRN program. He adds, there were tight tolerances to adhere to because all pod "pointing" functions are referenced back to the IMU and, in turn, supplied to the pilot. "If any of that is wrong," says Dyer, "information to the pilot would be wrong." Pro/ENGINEER let engineers accurately position the IMU in respect to what the pilot sees. According to Dyer, the software halved the design-process time compared to making a metal mock-up of the unit.
In addition, engineers used I-DEAS Master Series finite-element modeling software for safety-of-flight analysis and stress modeling. They modeled the stresses based on existing airframe information and used flight data to make design iterations. "Taking the recorded data and applying it to the models allowed us to validate and certify that the pod could survive the environment," says Dyer. When design and testing was complete, Lockheed Martin engineers used the Micro Cadam 2D design package to produce documentation for construction approval.
Incorporating the system onto the aircraft did not require operating software changes. As a result, engineers were able to speed integration time and decrease cost. "The aircraft doesn't really know it's carrying the pod," says Dyer.
"Integrating the targeting pod allows the pilot and backseat Radar Intercept Operator (RIO) to recognize, track, and deliver ordnance on a specific target," says Jerry Garman, Lockheed Martin program director for the LANTIRN F-14 program. "There is no navigation pod, but the FLIR provides situation-awareness and the GPS/INS provides an accurate navigation capability."
The GPS/INS provides aircraft status and location data. For example, navigational waypoints loaded into the system's monitor are translated by the GPS/INS system into directions to the target. These are provided to the RIO and pilot on high-resolution displays.
Launching with LANTIRN. "I believe the LANTIRN has given the F-14 a new life," says Gary Kessler, program manager for the Navy. He notes that "with the scenario in the Gulf War being primarily air-to-ground combat, the F-14 could never really be a player until LANTIRN was installed."
Lockheed Martin is looking to incorporate components such as an improved laser that can be used at 40,000 ft altitude and a laser spot tracker into LANTIRN systems. "The whole purpose of this product improvement of course is to take advantage of the technologies as they evolve and have application to our system, to maintain the state-of-the-art of our pod," says Garman.
"I think we've broken the ice here," comments Dyer. "In fact, one thing that has come out of this is that other companies are being asked why they can't integrate the same way the LANTIRN program did on the F-14. This program has set a standard that this can be done."