September 2005 
Volume 04, Issue 5 
Integrated Defense Systems

Sweet 16

Boeing continues the C-17's excellence with Block 16 upgrades


If it ain't broke, don't fix it, right? Not if you're talking about the C-17 program.

Building blocks

Here are some of the upgrades in C-17 aircraft equipped with Block 16, the latest series of improvements.

• A state-of-the-art weather radar system
• An improved Onboard Inert Gas-Generating System (OBIGGS II). This system quickly and efficiently inerts gases in fuel tanks, preventing them from exploding if hit by enemy fire
• An improved stabilizer strut system
• A suite of modernized avionic boxes

Working in conjunction with the U.S. Air Force and suppliers worldwide, Boeing has continued to design improvements to the C-17, making it even more capable and reliable. Boeing marked the debut of its latest set of upgrades to the C-17 Globemaster III with the Aug. 9 delivery of the Air Force's 138th C-17. The aircraft will be based at March Air Reserve Base, Calif.

This latest series of improvements to the C-17 fleet is dubbed Block 16. All Block 16 aircraft will have a state-of-the-art weather radar system; an improved Onboard Inert Gas–Generating System called OBIGGS II; a new, more reliable and stronger stabilizer strut system; and a suite of modernized avionic boxes, the latest in avionics technology. Previously delivered aircraft will have the upgrades retrofitted beginning in 2007 at Boeing Logistics Support Services in San Antonio. "We continually work with the U.S. Air Force to improve the C-17 to add increased capability and reliability while reducing the customer's maintenance and operating costs," said Pat Kelley, Block 16 program manager.

State-of-the-art safety

Imagine piloting a C-17 on a humanitarian aid mission and being able to see a hazardous thunderstorm on your flight path well before running into it. Now pilots will be able to plan a course around the hazard much earlier, thanks to the new weather radar system installed with Block 16.

C-17 cockpitDesignated the APS-150 by the Air Force, this weather radar system allows pilots to see weather systems up to 320 nautical miles (593 kilometers) ahead—up from the 160 to 200 nautical miles (296 to 370 kilometers) on the previous system. Boeing worked with Honeywell, based in Redmond, Wash., to add military modes to an advanced commercial-based system.

The system "lets pilots plan ahead and plot their courses with a much higher degree of accuracy and efficiency," said David Dodge, C-17 Weather Radar project manager. This new radar, Dodge said, is markedly more reliable, weighs nearly half as much and uses one-third the power. "And ultimately," he added, "it'll keep passengers and crews safer."

The OBIGGS II system is another upgrade that will enhance the safety of U.S. airmen. OBIGGS II is a new system that quickly and efficiently inerts gases in fuel tanks, preventing them from exploding if hit by enemy fire. Pilots activate the system with the push of a button, which pumps
nitrogen-enriched air into the fuel tanks. The tanks are inerted in less than one hour—much less than the four to eight hours previously needed. In addition, the new system cuts the aircraft's weight by almost 500 pounds—"always a crucial element for any airplane customer," said Jack Little, OBIGGS II project manager—because the equipment is lighter and there's less of it.

Getting ready for a big test

The Block 16 upgrades for the C-17 presented unique challenges to the Flight Test crew at Edwards Air Force Base, Calif.

The team, featuring Boeing and U.S. Air Force crew members, required more than 330 test hours—175 flight hours and 155 ground hours—to review the numerous avionics system changes and new state-of-the-art weather radar system on their two flight-test aircraft and loaned production aircraft.

"We chased severe weather and convective cells for weeks on end," said Bob Davey, C-17 ground- and flight-test senior manager. Davey noted that at one point, the team had to fly to Newfoundland in far eastern Canada to find the appropriate weather.

The flight-test crews flew the C-17s directly into severe weather to determine the reliability and predictability of the weather radar system—in other words, to ensure that "the convective weather identified is accurately represented to the aircrew," Davey said.

Initial testing began in fall 2004 on the two in-residence test aircraft. Testing will continue through December on the first two Block 16 aircraft, P-138 and P-139, at Edwards, where crews will conduct flight testing on the new OBIGGS II system, which quickly and efficiently inerts gases in fuel tanks.

"The OBIGGS II system tests will be performed on an actual production aircraft, not our test aircraft," Davey said. "It didn't make sense from a program management standpoint to upgrade the planes assigned to Flight Test, because the inerting system is very complex and built into the airplane and its wings."

Despite numerous challenges with late developmental issues, the combined test force came through, Davey said. The test team was able to integrate all of the test requirements and successfully complete the program days before first flight of P-138.

But Davey and his teammates won't have much time to rest. Continuous improvement is the name of the game.

"Block 17 flight testing began in August," Davey said. "We've got our sights on the delivery of P-153 in June 2006."

—Debby Arkell

When flight testing is complete later this year and capability is released to the fleet, OBIGGS II is expected to provide pilots with a significantly more reliable system.

Strut your stuff

Boeing also has redesigned the C-17's stabilizer struts. The stabilizer struts balance and support the airplane during loading of heavy cargo such as tanks, helicopters or large containers onto the aircraft. The struts also are used to jack the aircraft, allowing Air Force maintenance crews to change the main landing gear tires anywhere in the world.

The new struts are a simpler design than earlier versions and are much easier for the customer to use and maintain, and using them requires less training.

One notable aspect of the strut system upgrade is that the computer control has been removed. This eliminates the risk of uncommanded stabilizer strut deployments. "There is no substitute for 'hands on' control of the struts," said Todd Arney, C-17 Stabilizer Strut project manager.

Finally, Block 16 changes include an extensive upgrade to the C-17's avionics, touching nearly all of the subsystems. The complex avionics system controls flight and monitors fuel and other navigational elements. Said Kelley: "It's the brains of the airplane."

Kelley said some of the avionics being upgraded in this block could no longer be built because parts are obsolete. The new state-of-the-art computers are interchangeable with the legacy units. However, since many of the computers were completely redesigned, they required extensive lab and in-flight testing prior to the first delivery (see story at right).

Block upgrades like this one ultimately improve the reliability of the parts, and the mean time between failures increases as newer technology is incorporated. That creates increased value for the customer.

"We knew that this Block was the most complex, wide-ranging set of changes to be delivered since the C-17's introduction. The Boeing team worked closely with us and delivered this Block on schedule, within budget and fully capable," said John Slye, U.S. Air Force C-17 chief engineer. "I couldn't be more pleased with the Boeing team and their commitment to excellence."

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