February 1, 2004
GATM-izing Galaxy: New C-5 Avionics
Modernizing the U.S. Air Force's C-5 transport
has proved to be a complex project, reusing technology from various commercial
programs and integrating application software from multiple companies. Equipped
with Global Air Traffic Management avionics, however, the aircraft will stay on
course in the changing ATM environment.
By Charlotte Adams
The
U.S. Air Force plans to gut most of the analog electronics in its giant,
30-year-old C-5 Galaxy transports and install highly integrated, digital
avionics. After that, there is a plan, still being matured, to install modern,
commercially derived engines, full-authority digital engine controls (FADECs),
updated fault monitoring and recording systems, and much else. With this avionics
and propulsion overhaul, the service hopes the airplanes not only will hold
their own in modernized, civil-controlled airspace, but exact a significantly
lower outlay to operate and maintain.
Preserving the airplane's vast cargo capacity—roughly two
C-17s' worth per C-5—is important. But the Galaxy is one of the most expensive
aircraft to operate in the Air Force inventory. Their mission capability rate
hovers at 60-odd percent, driven mainly by the aging powerplant. The two-part
upgrade aims to lift the mission capability rate to better than 75 percent.
Lockheed Martin, lead contractor for C-5 modernization, also claims the twin
upgrades will reduce the Air Force's total ownership cost fleet-wide by 34
percent over the remaining life span.
The digital avionics to be installed in the C-5 Avionics
Modernization Program (AMP) will enhance reliability only slightly but will lay
the foundation for the major improvements that are expected in a follow-on
Reliability Enhancement and Re-engining Program (RERP), says Dave Rycroft,
chief engineer, strategic airlift, with Lockheed Martin Aeronautics. RERP has
been funded as a development program. The Air Force plans to "RERP" two C-5Bs
and one C-5A to verify the hoped-for performance and reliability boost. A production
decision on the re-engining program is expected in FY2007.
If the service proceeds with the powerplant upgrade, the B
models, used by the active forces, will be RERP'd first, a process that would
not be completed until 2012. At that point, however, the average C-5A would be
more than 40 years old—perhaps too old to justify a costly makeover. Air Force
leaders would have to consider the changing C-5 role, ongoing C-5A "teardown"
analyses, and (future) RERP field experience before making a decision on the
C-5A. All of the upgraded aircraft will be designated C-5Ms.
On the other hand, new engines will be important to achieving
air traffic management (ATM) compliance in areas where "you need to climb to a
certain altitude within a certain time," says Col. Kevin Keck, C-5 development
system manager at the Aeronautical Systems Center. The two sides of the
modernization effort are connected, in that new engines will require new
displays. But AMP's main purpose is to equip the aircraft to fly by the most direct
routes, at the most advantageous altitudes—with the most efficient fuel usage
and cargo loads—in civil airspace. AMP also provides an avionics architecture
flexible enough to meet future communications, navigation, surveillance
(CNS)/ATM requirements, which in the U.S. military, are filtered through the
Global Air Traffic Management (GATM) program.
Key GATM avionics include:
- Future Air Navigation System (FANS) data link,
- Aeronautical operational communications (AOC) data link,
- VHF com, 8.33-KHz spacing,
- Multimode receiver (MMR) with protected ILS, VOR, microwave landing system
(MLS) and marker beacon,
- Dual, embedded inertial navigation system (INS)/GPS,
- Identification, friend or foe (IFF)/Mode S transponder,
- Traffic alert collision avoidance system II (TCAS II), Version 7, (added
earlier),
- Enhanced ground proximity warning system (EGPWS),
- Backup air traffic control (ATC) data link printer, and
- Versatile Integrated Avionics (VIA) system, with six primary "partitions"
or applications, such as: flight management, com/nav/surveillance/identification
(CNSI), com management, display services and all-weather flight control.
In addition, each C-5 will be fitted with an easier-to-fly
glass cockpit. All told, in an AMP'd aircraft, 12,000 wires are removed and
4,000 are installed, a reliability improvement in itself, says Blair Marks, C-5
AMP program manager with Lockheed Martin Aeronautics.
New Capabilities
The new avionics systems will allow the aircraft to
comply with reduced vertical separation minimum (RVSM) requirements as outlined
by Advisory Circular (AC) -91-RVSM, says Rycroft. The airplane also will have
an automatic dependent surveillance (ADS) 1A data link with a growth option for
automatic dependent surveillance-broadcast (ADS-B). C-5 pilots will be able to
fly AMP'd aircraft to required navigation performance (RNP) 4.0 en route with
successive growth options of RNP 1.0 and 0.3 in the terminal area, Rycroft
says. The aircraft also will have controller pilot data link communications
(CPDLC) electronic messaging.
The C-5B models are now equipped with a flare-dispensing
system, but only one C-5A version has countermeasures, says Keck. The Air
Mobility Command recently identified self-protection as a high priority, but
installation of such equipment is outside of the AMP baseline. The C-5 is a
candidate aircraft for the Large Aircraft IR Countermeasures (LAIRCM) program,
but no funding has yet been provided against that need.
Glass Cockpit
The most obvious part of the avionics upgrade is the new
glass cockpit, with seven 6-by-8-inch color, flat-panel, multifunction display
units (MFDUs) that integrate information from a large number of analog "steam
gauges." Across the front panel are six displays—three for the pilot and three
for the copilot. The flight engineer monitors the seventh display from a
station in the rear cockpit.
The pilot's and copilot's secondary flight displays can
present information on radio states, moving maps, weather radar, terrain,
traffic—"any information you wish," says Joe Schwendeman, C-5 modernization
program manager for Honeywell Defense and Space Electronics Systems, Lockheed's
key avionics partner. Flight crewmen interact with the MFDUs via a cursor
control device, although flight plan information is fed to the flight
management system (FMS) through a traditional multifunction control and display
unit (MCDU).
The crew can tailor the display presentations. Typically the
center pair would show information such as cautions and warnings, engine
data—such as turbine inlet temperature, speed, fuel flow—and built-in-test
data.
A major benefit of the glass cockpit is increased situational
awareness, says Keck. Crews like the ability to integrate a lot of the displays
and overlay different views on a single display, he says. "You can toggle
through your options easily," reducing workload.
The Heart of AMP
The heart of the avionics upgrade is Honeywell's
Versatile Integrated Avionics architecture, which replaces nine or 10 black
boxes in what previously was a highly federated architecture. (There are two
VIAs, operating simultaneously, for redundancy. If the second VIA determines
that the first is defective, the second takes over.) The VIA computer combines
flight management, flight control, the management of the communications and
navigation radios and the displays, com/nav/surveillance and identification
processing, built-in-test monitoring, and mission integrity management, fault
logging and bus control.
"The VIA architecture makes GATM compliance on a 30-year-old
aircraft possible with a minimum number of LRUs [line replaceable units]
because it has the maximum amount of flexibility," Schwendeman says. "The
performance is all in the software and it can be changed—so you don't have to
change the LRUs." Although weight savings wasn't the motivating factor for the
choice, integrating the architecture saved 120 pounds (54.4 kg), Keck says.
Off-the-Shelf
The hardware risk of the VIA architecture is low. The
hardware already has been certified on the Boeing 737-700 aircraft, the B717
and, as a retrofit, on FedEx Express' MD-10 fleet. VIA hardware also is used on
the U.S. Navy's E-6 command and control aircraft and will be certified on KC-10
tankers. VIA repackages the Airplane Information Management System (AIMS) architecture
originally certified on the B777.
Even in the software area, there is significant reuse.
Honeywell's communications management function (CMF) software, which handles
radio and data link operations, "is a direct port from a commercial
application," Schwendeman says, referring to the Mark 2 com management module
that Honeywell developed for the business/regional market. The FMS software,
likewise, is based on Honeywell's commercial Pegasus technology and "the
preponderance of software is identical" to that used in the KC-10 development
program, Schwendeman says. Honeywell is bearing the cost for more than 95
percent of the applications code it is writing for VIA, which it is using on
other programs.
Probably about 90 percent of the VIA software is based on
prior Honeywell implementations and about 75 percent of the hardware is either
directly off the shelf or derived from a commercial product, Schwendeman says.
"The beauty of this acquisition is that there is very minimal hardware
development cost paid for by the Air Force or Lockheed because we managed to
make use of a maximum amount of our commercial product."
The AMP architecture specifies dual-redundant VIAs, plus a
backup processor by BAE Systems. Each VIA includes two black boxes—the second
known as the auxiliary interface unit—that operate as a single logical unit, a
"virtual LRU." Not all of the software applications run on both boxes. The
first box includes one processor, known as a core processing module (CPM), plus
a currently unfilled growth slot, identified as CPM 2. (CPM 2 is slated to be
added with the engine upgrade.) Each CPM is based on a commercial AMD 29050
processor. The second box contains another CPM, identified as CPM 3. Each 29050
has a throughput of 23 Vax MIPS (millions of instructions per second) and can
be upgraded to about 40 Vax MIPS. The "backup integrating processor" by BAE is
based on the company's design for the mission processor of the C-130J.
VIA Software
Key to VIA is Honeywell's time line concept, Schwendeman
says. Honeywell's proprietary VIA operating system—backed up by hardware
elements in the processing chips—ensures the separation of applications, or
"partitions"—living on the same processor and the execution of each
application's tasks in the processor at the correct time in the right place, as
dictated by an overall schedule. That schedule determines the priority and
frequency of each software task in the VIA system.
VIA hosts some 1.75 million lines of applications source
code. This includes partitions written by Honeywell, Lockheed Aeronautics and
Lockheed Systems Integration-Owego, but executed under Honeywell's operating
system.
C-5 AMP includes four software iterations, each successive
block of which adds features, functions and fixes to the base code. Initial
work focused on the basic ability to aviate, navigate and communicate, says
Marks.
The first chunk, block 1.1, focused on the digital flight
control system, basic displays and basic airworthiness. Based on feedback from
flight tests, changes were made and folded into the next software build. The
second block, 1.2, contained a more refined autopilot, as well as FMS flight
planning and lateral guidance, and all the flight control functions except
vertical navigation (VNAV) and autoland.
The last two blocks, 2.1 and 2.2, focus more on the
communications and navigation systems. Block 2.1 adds Category IIIa autoland,
EGPWS, TCAS, weather radar and other functions. It contains full flight control
functions, full CMF functions, and all FMS functions, except vertical guidance
and performance calculations.
The final software increment adds VNAV, performance
calculations, military radios, military flight planning and MLS. And it
completes the functionality of all the major software applications. After the
final software build has been flight-tested and a "block 2.2.1" has been
created, there will be a four-week functional qualification test.
Schedule
As of January, all of the applications software had been
written, and the first two blocks had been flight-tested. Flight testing of the
third block had begun and was expected to conclude by February of 2004. The
final software block was in Lockheed's laboratory and was expected to enter
flight test in March or April of 2004.
After flight test, the software will go into verification
testing against the system specification requirements. Operational test and
evaluation (OT&E) is to begin at the end of 2004 and culminate early in
2005.
"The risk is in software integration, and the risk is
principally schedule-driven," Keck says. The first aircraft modifications will
begin this summer, and AMP'd C-5s are to start reaching the field in January
2005. By that time, the Air Force expects to have completed verification
activity, but OT&E still will be going on.
"We accept that kind of schedule risk, "Keck says, "and we
believe that, with the verification activity being conducted this summer, the
concurrency with our initial installs is manageable." While there's a "distinct
likelihood" that fielded software will need to be tweaked, the phasing and
sequencing of the installs was designed with that in mind.
In a project this big, integrating blocks of application code
by multiple companies, and using algorithms and code developed on other
programs, glitches are expected. The iterative software development process was
designed to successively identify and correct these problems and feed in
changes as the program proceeds. In Block 2.1 flight tests, for example, issues
had to be addressed with the flight management and flight control functions. At
press time, Honeywell had delivered a fix for the flight management problem,
which was being readied for flight test.
Modernized Support for C -5
A key part of the U.S. Air Force's planned C-5
Reliability Enhancement and Re-engining Program (RERP) is to replace the
airplanes' malfunction detection, analysis and recording system (MADARS).
MADARS records and detects information such as built-in-test (BIT) failures and
structural and engine exceedances.
The new embedded diagnostics system (EDS), a combination of
hardware and software, is intended to "optimize [aircraft] availability and
mean time to repair," says Lt. Col. Darrel Watsek, RERP program manager. "EDS
not only records data but allows the continuous monitoring of aircraft systems,with
readily available troubleshooting and diagnostics."
EDS interfaces with the propulsion, environmental, secondary
power, mechanical, flight control, selected cockpit instrumentation,
diagnostics, radar, communications and navigation systems. It is to record
engine trend information, structural exceedances and flight data, among other
things.
A subset of EDS will be hosted on Honeywell's Versatile
Integrated Avionics (VIA) computer, the C-5's electronic brain. BIT data,
evaluated largely at the subsystem level, is transferred to the VIA, which
makes "high-level fault declarations."
Part of EDS, the
auxiliary maintenance computer (AMC) will further processs fault data to
pinpoint the cause of detected failures, Watsek explains. Developed by Demo
Systems, the AMC is a relatively off-the-shelf computer, running the Windows
operating system. The box is intended for ground-based maintenance, allowing
technicians to see what faults have occurred during a flight, says Dave
Rycroft, chief engineer, strategic airlift with Lockheed Martin Aeronautics.
AMC acts as a "server" in relationship to "clients," such as VIA or other
devices, Watsek says. It may, for example, be "requested" to route data for
reports to printers or data links. The
AMC also will host and manage a fault history database.
The U.S. Air Force's Air Mobility Command, meanwhile, is
looking at data linking logistics trend information to the ground as an option
for all of its mobility aircraft under the Mobility 2000 (M2K) concept. The C-5
will have the necessary pieces in place to make this possible, if the Air Force
decides to do so.
Back to this month's issue
|