C-5 Modernization, Step-by-Step

By James Ramsey | August 1, 2000
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The U.S. Air Force’s C-5 aviation modernization program (AMP) is a long-term project just getting underway, with fleet-wide installation of an advanced traffic alert and collision avoidance system (TCAS).

But TCAS is just the tip of the iceberg. The AMP program is viewed as a trial for a much larger, more ambitious program to follow, according to Marty Broadwell, Lockheed Martin’s C-5 AMP program manager.

First, TCAS

Following the $120-million AMP development contract granted by the Air Force in January 1999, Lockheed Martin launched an accelerated program to have a suitable TCAS ready for installation in just nine months. The pressing need to meet air traffic management (ATM) requirements, particularly beyond U.S. borders, dictated the program’s speed. The first system was installed in December 1999; flight test began in January.

"The idea was to very quickly get one piece of the global air management requirement on the aircraft," says Broadwell. "The good thing is it exercised our [primary] AMP teammates: Honeywell; Lockheed Martin Federal Systems, in Oswego, N.Y.; our own integration and testing here, and our flight test organization. All were involved in working out a lot of the processes, wiring requirements, controlling interfaces, and the validation effort."

Lockheed Martin chose Honeywell’s commercially available TCAS 2000, which was introduced in late 1997. More than 1,000 units have been delivered to commercial customers to date. On the C-5, the TCAS 2000 interfaces with the Raytheon APX 100 transponder. (Of note: Honeywell was required to divest itself of its TCAS product line as a result of its merger with AlliedSignal; Honeywell still has the former AlliedSignal TCAS family, but the old Honeywell line was sold to L-3 Communications of Sarasota, Fla.)

TCAS installation for the 126-aircraft C-5 fleet will take two years and be performed at various C-5 bases by Lockheed Martin’s field modification teams from its Greenville, S.C., facility. Lockheed is scheduled to install the system on four aircraft monthly, with each installation taking 20 days.

Advanced TCAS (ATCAS) hardware includes Honeywell’s (now L-3’s) top-mounted directional antenna and TCAS receiver/transmitter along with a Sensor Systems’ bottom-mounted omni-directional antenna, Raytheon Mode S transponder, Sextant’s vertical speed indicator/traffic resolution advisory (VSI/TRA) stand-alone TCAS displays, and an Emteq mounting tray. Modification work to the C-5 cockpit also includes changes to the flight management system, for control of the TCAS. The TCAS 2000 can track 24 aircraft within 5 nautical miles (nm). It can handle 1,200-knot closing speeds and 10,000 feet-per-minute permitted vertical rate.

In the C-5 AMP program’s following stages, the most visible piece of the cockpit modernization will be the six 6-by-8-inch (15.2-by-20.3-cm) flat-panel liquid crystal displays (LCDs) mounted in front of the pilot and copilot and a seventh display at the flight engineer’s station. Provisions have been made for an additional display at the navigator’s station when special missions may require a fourth crewmember.

Lockheed Martin selected Honeywell (now L-3) to provide the displays. One unit already has been delivered and is running in a Lockheed Martin laboratory, where pilots are evaluating viewing angles. Interspersed in the C-5’s large cockpit, other instruments–including standby flight instruments and G-force meters–have not changed but have been rearranged.

Two 4-by-5-inch (10.2-by-12.7-cm) ARINC standard 739 color multifunction control display units (MCDUs), with keyboard, are mounted at the front of the C-5’s pedestal below the throttles; the engineer’s station contains another unit. Primarily, pilots select or change displays and formats by maneuvering two cursor-control devices mounted just behind the MCDUs.

For C-5 navigation, Lockheed Martin will add a Honeywell enhanced combination ring laser gyro/inertial reference system (IRS) with a GPS receiver–an off-the-shelf commercial product

777 Brand of Processing

The heart of the cockpit display system is Honeywell’s Versatile Integrated Avionics (VIA) 2000 processor designed for the Boeing 777 and later repackaged for Boeing’s MD-10, B717 and new generation B737s. VIA 2000 integrates the display electronics and related software, flight management, communication management, and mission software. The C-5 will use the same chassis, processor module and power supplies, although it has unique interfaces because of some remaining military systems, including radios.

The VIA 2000 replaces some 13 separate boxes or redundant computers, Broadwell says, reducing maintenance costs and improving reliability.

Lockheed Martin also swapped the C-5’s old analog (auto) flight control panel–located between the MCDUs on the pedestal–for a digitized version. The Air Force asked for mode changes to coincide with commercial flight control modes–in part because some Reserve C-5 pilots also fly commercial airliners. Mechanical tapes in the center of the cockpit that show engine status on current C-5s will change to dials–also consistent with commercial jetliners.

New Philosophy

"It looks a lot like the 767 or new commercial airplanes," says Broadway of the planned C-5 cockpit. "So, fundamentally, we are recreating the avionics that was 1960s and 70s vintage and, where we can, making it more like our commercial counterparts.

"The main reason is to meet global air traffic management [GATM] standards while flying in commercial airspace by using modern commercial avionics," Broadwell explains. "The Air Force has guided us to choose as many commercial black boxes as possible. If that’s not possible, we choose one that is on a number of military aircraft.

"We are following two themes in this program: be as commercial as possible… and secondly, integrate–put as many things as possible in a single box, to reduce cost and increase reliability."

Broadwell counts on receiving new commercial upgrades, such as an expected TCAS update, at minimal expense. "Manufacturers must keep upgrading to meet FAA requirements, which allows us to get upgrades at much reduced cost," he reasons.

"The Air Force doesn’t have to pay for new development, only for integration into their aircraft," says Chuck Smith, Lockheed Martin’s deputy C-5 AMP program manager. "The commercial [avionics] equipment suppliers are paying for development to stay competitive. This is a real change in philosophy that we are using on this program."

USAF Certification

"Another real change," he points out, "is that because we’re trying to meet ICAO [International Civil Aviation Organization] international airspace requirements, the Air Force is going to certify the equipment on our aircraft, instead of having FAA certify it–a first for this program. Air Force must develop its own certification process to do this, and we’re working closely with [the Federal Aviation Administration]."

Lockheed Martin also is borrowing from its other programs for the C-5 AMP. For example, it takes the same cursor control device and same commercial sensors, including combined UHF/VHF radios, from the C-130J program (see Avionics Magazine, July 2000, page 20). Likewise, when the full AMP upgrade is accomplished, the small (3-inch or 7.6-cm) TCAS indicators will be replaced by a TCAS overlay on the pilot’s navigation display, as is done on the C-130J.


The C-5 AMP program schedule still calls for installation to begin on the first two aircraft in mid-2001, followed by developmental test and engineering. But because the Air Force has requested that changes be made in flight control modes, the schedule is being reevaluated. First flight of the new system now is proposed for the first part of 2002 and flight test will consume most of that year. Deliveries of completed aircraft would begin in 2003. Total value of the AMP program could exceed $450 million.

Following AMP, the USAF is studying an extensive re-engining program, which would include a number of system and structural upgrades, referred to as a reliability enhancement re-engining program (RERP). Broadwell sees AMP as a first phase of this broader program and is helping to set up the aircraft for new engines by putting a growth partition in the VIA for the full authority digital engine control (FADEC). The digital boxes and spare capacity built into the computing system will allow integration of more sophisticated systems, such as engines and APUs when they come along. This may include some additional electronic box replacement, Broadwell says.

So, to Broadwell, AMP plays only a minor role in helping to improve the C-5’s known, dismal mission reliability rate.

The C-5’s original computers were "never major hitters," Broadwell admits. "If they were 1% of the problem, we are reducing that to 1/10 of a percent. The intent of AMP is first and foremost to quickly get the aircraft up to global air traffic management standards."

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