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[37th TFW F-117A's undergoing depot maintenance and upgrades at Site 7, USAF Plant 42.(LMSW)]

F-117A Upgrades I

Configuration Updates

The F-117A fleet has received a succession of minor updates, usually aimed at improving maintainability and reliability, and consisting of minor wiring changes and similar small "fixes". They include the following:

Configuration Update 1:
Applied to 11 aircraft between October 24, 1983 and January 8, 1986.

Configuration Update 2:
Applied to 8 aircraft between July 7, 1985 and October 28, 1986.

Configuration Update 3:
Applied to 12 aircraft between July 7, 1986 and January 15, 1988.

Configuration Update 3+:
Applied to 3 aircraft between September 10, 1987 and May 3, 1988.

Configuration Update 4:
Applied to 26 aircraft between January 8, 1988 and October 25, 1990.

Configuration Update 5:
Applied to 54 aircraft between June 21, 1990 and March 8, 1995.

Configuration Update 5+:
Applied to 11 aircraft between October 1994 and December 1996.

Configuration Update 6:
Began in November 1996


The first major upgrade was the Weapons System Computational Subsystem (WSCS) upgrade and the integration of the new GBU-27. The GBU-27 would become the primary weapon of the F-117A used extensively in Desert Storm. It marked the first phase of the Offensive Capability Improvement Program (OCIP) modification and was authorized on April 1, 1984. Deliveries of WSCS-modified aircraft took place between November 1987 and June 1992. The WSC upgrade replaced the three Delco M362F mission computers (also fitted to the F-16) witha single AP-102, a repackaged version of the computer NASA uses on the Space Shuttle.


[OCIP II Cockpit. (LMSW)] The F-117A gained a new cockpit layout under OCIP phase II. The original, centrally mounted FLIR/DLIR display was replaced by a Harris Corporation digital moving map display, with the IR imagry now displayed on one of the two Honeywell color, multifunction LCD screens. These replaced the original monochrome, Texas Instruments Multifunctional Displays (MFDs) on the left and right hand sides of the main panel. The liquid crystal display data entry panel allows the pilot to select from 256 avionics functions. The new cockpit equipment is designed to minimize the chance of pilot disorientation at nighttime, which was the primary cause of three accidents involving operational F-117s.

OCIP II also introduced a four-dimensional flight management system, adding autothrottle (computer control of the throttles to meat specific waypoints at specific times during the mission) as well as autopilot. The first test flight of an OCIP II aircraft was conducted on December 1, 1988 in ship #831. Ship #831 was bailed back from the USAF and currently serves as the only production airframe used for testing with the 410th FLTS at Plant 42, Palmdale . The first modification kit was installed in April 1990, and modification of the last aircraft was completed on March 8, 1995.


[RNIP+ logo. (F-117A SPO)] Despite the accuracy of its Internal Navigation System (INS), the F-117A was extremely weather dependent. With no ability to use ground-mapping radar or terrain-reference navigation systems, the F-117A relied on clear skies for precision navigation to its initial point (IP) and target. The main feature of the OCIP III program thus lay in the final replacement of the specially selected and calibrated B-52 Honeywell SPN-GEANS INS. Under this Ring Laser Gyro Navigational Improvement Program (RNIP), the original INS was replaced by new Honeywell H-423/E laser INS. Although accurate, the SPN-GEANS took more than 40 minutes to align and was becoming increasingly difficult to support. The new INS aligns rapidly, is more accurate and offers a much improved mean time between failures (MTBF) factor. The subsequent integration of a Rockwell-Collins GPS with low observable antennas brought a program redignation from RNIP to RNIP+, and marked significant improvement again in navigational accuracy. RNIP+ also included a Weapons System Computer (WSC) upgrade.

[Covert RNIP patch.] The RNIP+ upgrade started as a classified program. The covert patch on the right was developed during this period. As with many previous F-117A patches, because of the covert nature of the program, only abstract symbols were used in the design of the emblems. This design was derived from a far side cartoon representing the old systems that would be used to defeat the stealth and what the new upgrade would do to it.

The following was published on January 27, 1997 by the USAF/LMSW.

"On January 24, 1997 Capt. David Toomey departed Palmdale Plant 42 on his way to RNIP+ delivery ceremonies at Holloman AFB, NM. Lockheed Martin Skunk Works delivered - on time and under budget - the first F-117A stealth fighter equipped with a vastly improved navigation system. (From the January 24, US Air Force News".)
"RNIP+ was a $100 million modification and upgrade program to the F-117A. "The upgrade improves both the supportability and accuracy of the navigation system," F-117A Program Manager Ross Reynolds said. "A Skunk Works-developed low-observable antenna enables our newly incorporated global positioning system to provide continual aircraft position accuracy within 30 feet, anywhere in the world, without the use of ground navigation aids."
The Ring Laser Gyro Navigation Improvement Program (RNIP) began in 1991 when the decision was made to replace the original F-117A navigation system with a ring laser gyro to improve supportability. In May 1993, the Air Force expanded the program to upgrade the aircraft's weapon system computers with increased memory and processing speed, while at the same time replacing the navigation control display in the cockpit and incorporating the global positioning system. This resulted in the plus (+) being added to the RNIP acronym.
The first development aircraft flew in December 1994, which began an 18-month flight test program conducted by the 410th flight test squadron at Plant 42 in Palmdale. Retrofit of the F-117A fleet is under way at the Skunk Works, with completion currently scheduled for the last quarter of 1999.
Program officials at Aeronautical Systems Center, Wright-Patterson AFB, Ohio, said the new system is three times more reliable and requires 100 times less maintenance than the current system. Additionally, the time needed to calibrate the equipment before takeoff dropped from 43 to 15 minutes. Pilots also have the option to take off within 90 seconds and complete the navigation alignment in about five minutes while airborne using GPS.""
The following was published on February 11, 1997 by USAF News.

"by Tech. Sgt. Anne Proctor
Air Combat Command Public Affairs

HOLLOMAN AIR FORCE BASE, N.M. (AFNS) -- A new and improved F-117A Nighthawk stealth fighter touched down here Jan. 22.
The Lockheed Martin Skunk Works delivered the first F-117A configured with a new navigation system to the 49th Fighter Wing. Dubbed "RNIP-Plus," the Ring Laser Gyro/Global Positioning System Navigation Improvement Program reduces the drift pilots experience during flight.
Drift is when an aircraft's navigation system wanders off its intended flight path -- a computer problem in the older Inertial Navigation Systems.
The 49th FW commander, Brig. Gen. Dennis Larsen, is impressed with the RNIP-Plus. He noted that in a recent mock-bombing mission before the upgrade he experienced a drift of 1,500 feet; a sharp contrast to fellow pilot Capt. David Toomey's encounter of zero feet using the new RNIP-Plus.
"It blew my mind," said Larsen. Toomey is a pilot in upgrade training with 9th Fighter Squadron at Holloman.
The new system uses computer technology to integrate the INS and Global Positioning System -- a group of more than 22 satellites the Air Force uses to provide navigation data to its aircraft. The net result is the pilot gets continuous updates to the plane's altitude and overall position, said Maj. Brian Foley, F-117A special projects manager at Air Combat Command, Langley Air Force Base, Va.
Not only does the RNIP-Plus boost navigation, it also strengthens the F-117A's targeting capability. Foley said Nighthawk pilots have more precision with RNIP-Plus because the aircraft's "cross hairs" are aligned closer to the target than with previous navigation and targeting systems.
The configuration includes a new control display navigation unit in the cockpit allowing the pilot to quickly reference and check flight data. The control display also collects and stores maintenance data on the INS and GPS, a plus for post-mission maintenance.
Retrofit of the F-117A fleet is currently under way by Lockheed Martin Skunk Works with a planned completion in October 1999. (Airman 1st Class Aaron Cram, 49th Fighter Wing Public Affairs, contributed to this article). "


A comprehensive midlife upgrade (MLU) for the F-117A was formally studied under the Midlife Improvement Study (MIPS) launched in early 1995. This was planed to investigate further signature reduction measures (though these were trimmed from the study in the 1996 budget) together with the integration of new weapons. The MIPS looked closely at integrating weapons with GPS guidance (including JDAM and JSOW) via a MIL STD-1760 digital data bus. This measure was also proposed for the proposed A/F-117X variant. Some sources suggest that other features from the various proposed F-117A variants (including a transparent F-22 type cockpit canopy) were also examined under MIPS.

The MIL STD-1760 data bus was actually installed in F-117As from September 1994 onwards, and developement will be completed during FY00. A smart weapons-integration contract was awarded to the Skunk Works in September 1998, which will see full integration of the JDAM and WMCD.


[F-117A IRADS Components. (Texas Instruments)] The F-117A's original IRADS targeting system was completely reliant on clear weather, and the aircraft was subject to a high abort/DNCO rate due to less than ideal conditions. The IRADS itself was the subject of a Block 1 modification (replacing curcut boards, providing heavier stops and rerouting wiring) between 1986 and 1988, and an F3 turret modification that comenced in 1993. The original FLIR and DLIR sensors were replaced by new Texas Instruments thermal imaging sensors. The F3 turret was first flown on Augest 14, 1992, and flight-testing was completed on February 12, 1993. Production turrets were retrofitted between October 1, 1994 and October 1996.

[F3 Upgrade logo. (F-117A SPO)] Modifications in this area are currently under way. The second generation Raytheon Systems Company Integrated Acquisition and Designation System (IADS) ioncorporates the addition of a new video tracker and system controller in the existing F3 turret. This will allow more accurate "painting" of the target. The IADS will integrate an imaging IR sensor into the system, providing high-quality imagery that can be transmitted to otheraircraft or stations on the ground using a low-probability-of-intercept, encrypted datalink. This link will not comprimise stealth characteristics. A $10 million contract for 50 sets (43 new production units and seven refurbished development sets) was placed by the USAF Aeronautical Systems Center (ASC) at Wright-Patterson AFB in September 1998. Installation should begin in December 1999.

Diagnostic Imaging Radar

From October 1999 USAF Airman Magazine:
Story by Tech. Sgt. George Hayward

[DIRS logo. (F-117A SPO)] At Holloman Air Force Base, an innovative radar system helps make stealth even stealthier.
The flaw can be so subtle you can't see it with the naked eye. But that's all it might take. A layer just too-thin enough that an enemy radar will reflect off it and reveal the aircraft hidden beneath.
Unless our radar sees it first.
Contrary to many a layman's belief, the F-117 stealth fighter is not comletely invisible to radar. It's what experts call "low-observable." Due to its shape and a special radar-absorbent coating, the aircraft is all-but-undetectable by radar. Maintainers at Holloman Air Force Base, N.M., home of the stealths, keep the Nighthawk stealthy with constant upkeep on that coating. And a new radar system there tells them exactly where to add an extra touch of "invisible ink."
With the Diagnostic Imaging Radar, Holloman maintainers take photos of stealth birds that reveal not only if the aircraft will show up on radar scopes, but also what - a certain seam or particular panel - the radar sees.
"This is a tool to let us see how our job can impair or improve the aircraft's stealth capability," said Staff Sgt. Chad Brown, a program technician. "It's done a lot more than what we thought it would do."
[Master Sgt. Tony Garza (left) and Staff Sgt. Dan Jeffries prep an F-117 for a photo shoot with Holloman's Diagnostic Imaging Radar. The panels
around the jet's landing gear also are coated with radar-absorbent material, so the aircraft's radar signature is the same as it would be in flight. (Photo by Staff Sgt. Andy Dunaway)] The program uses a Mark V radar to shoot almost 100 images of a parked aircraft, from a variety of angles. Special panels of the radar-absorbent material are wrapped around the airplane's landing gear, so the aircraft looks to the radar like it does when flying. The images are fed through a diagnostic analysis computer, which reveals not only if the aircraft is visible to the radar, but where specifically "Martian magic" is needed to make it stealthier.
The "Martians" are maintainers who lay on the radar-absorbent coating in Holloman's Material Application and Repair Section. It's meticulous work, gluing sheets and strips of radar-absorbent material to the aircraft with a paste that is equally radar-absorbent. "From a Martian's standpoint, it shows you what little things can impact the aircraft," said Brown, a former Martian.
Those "little things" are invisible to the naked eye, but not to a radar. Not enough glue here, an imperceptible gap in material there, and the aircraft may show up on enemy radar screens. Holloman's system pinpoints those little things for the Martians, who then do some patchwork. It's like touching up a paint chip on your prized sports car.
"There's one specific goal - to be sure the pilot has a safe, low-observable airplane to go into any combat zone or contingency. So he can do his mission and come back alive," said the radar's manager, Master Sgt. Tony Garza.
[DIRS rail system being tested at SIte 7, Plant 42. (F-117A SPO)] The $36 million program started about three years ago, and Holloman has two fully deployable systems. Each stealth fighter squadron has a team of trained maintainers, and Garza and Brown - along with Staff Sgt. Dan Jeffries - have been with it since conception. "We've been with it from paper to reality," Garza said. "And we've seen tremendous results. The program has already paid for itself."
Currently, aircraft usually get "shot" before and after unscheduled maintenance. But the staff members hope to eventually use it to extend the stealthiness and service life of each F-117 by imaging them on a regularly scheduled basis.
Just like the performance differences and quirks between two automobiles - or even aircraft - of the same model, each F-117 has its own stealth traits. "We want to use the system to image the entire fleet so we know what every aircraft looks like," Garza said.
"As each airplane gets older, we'll be able to keep it stealthy," added Jim Crawford, one of the program's contractor engineers.
Not only keep it stealthy, but make it stealthier. "When you get a plane out here and don't see anything on the radar, you feel good," Brown said.

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