The E-3 Sentry airborne early warning and control aircraft, or AWACS, is a linchpin of United States air power. With its powerful radar and communication systems, the E-3 can patrol vast swaths of territory for aerial and maritime adversaries, and direct friendly forces to respond.
However, like a lot of older military hardware, the Sentry's 1970s and 80s-era electronics lack many capabilities we take for granted in modern computers.
So it makes sense that the Air Force has been working to upgrade its AWACS fleet to the new E-3G Block 40/45 variant with modern open architecture computers that can be updated on the fly. The Air Force has already refitted nine E-3s to the new standard.
However, plans to upgrade 18 more have been delayed after the Block 40/45 dramatically flunked a series of performance tests in 2016. Ironically, the downside to having modern computers lies in their vulnerability to that most contemporary of threats — hacking.
The E-3 Sentry was first deployed in 1977, replacing the older EC-121 Warning Star which served in Vietnam. Basically a 707 airliner with a nine-meter diameter APY- 2 radar rotating on top, the E-3's 13 to 19 crew members can track aircraft and ships from as far as 250 miles away.
The Sentry is particularly useful for detecting aircraft flying below the effective altitude of surface-based radars. The E-3's 20 high- and ultra-high frequency radios allow the crew to communicate with and direct friendly forces.
Today the US Air Force operates a fleet of 32 E-3s across the world, while European NATO countries share a fleet of 16 Sentries based in Geilenkirchen, Germany. Smaller numbers also serve in the air forces of France, the United Kingdom, and Saudi Arabia.
The E-3G Block 40/45 upgrade replaces the Sentry's antiquated computers with a Red Hat Linux-based system for the main flight computer, and Windows-based operator workstations, which are connected to each other via a local area network. These will provide a new user interface and application for 15 crewmembers.
The open-architecture operating systems are easy to update, and have "spare computing power for future capabilities" an Air Force spokesperson told War Is Boring.
Furthermore, the E-3G's computers are designed to fuse air, sea, and land tracks into a single integrated sensor display, which should save time and reduce the likelihood of target identification errors. New ground-based computer terminals enhance mission-planning and post-mission data analysis.
The Block 40/45 also incorporates a satellite communication system and digital upgrades that increase the flow of data to the E-3G, allowing it operate in more congested airspace and lower the number of communication technicians needed onboard the plane.
The E-3G's Link 16 and 11 datalinks have also been optimized to decrease latency when transmitting targeting data for priority targets. Finally, there are modifications to improve the troublesome electromagnetic sensors—or Electronic Support Measures—added in the preceding Block 30/35 variant.
All these advancements haven't come cheap. A 2014 spending and acquisitions report estimates that R&D and procurement expenditures on the E-3G program, which began well over a decade ago, would total more than $2.6 billion by 2016.
Two E-3Gs were first operationally deployed in support of anti-narcotics operations in the Caribbean, and in November 2015 the new Sentries began flying combat missions over the Middle East.
By 2016, Boeing had converted nine aircraft to the Block 40/45 standard, most using older 32-bit hardware. However, the Air Force wished to conduct additional testing before converting the remaining aircraft to a more powerful 64-bit configuration with an improved ground support system. But the program's annual report reveals that the new trials didn't go smoothly.
First of all, a cold weather test mission in Fairbanks, Alaska, literally failed to get off the ground because of problems with the radar and airframe unrelated to the new computer systems.
Then, that summer, a Block 40/45 plane underwent competitive maritime surveillance trials versus an older Block 30/35 E-3 over the Gulf of Mexico. Both aircraft reportedly had "deficiencies" tracking the position of ships at sea, but the new Block 40/45 airplane proved "less effective." Furthermore, the E-3G's ground-based 1.0 operating systems overheated repeatedly.
Finally, two Block 40/45 aircraft were deployed for the Red Flag 16–3 exercise conducted from Nellis Air Force Base in Nevada. These planes benefited from newer 3.0 Deployable Ground Support systems which continued to function despite sweltering heat, requiring only one restart during the three week-long exercise. However, the E-3Gs demonstrated "inaccurate track quality data processing and inconsistent IFF [Identify Friend or Foe] response displays to the operator."
The Air Force also noted that the upgraded Electronic Support Measures system remained "not reliable."
Prior to Red Flag, however, the Block 40/45 had already failed a critical test—a three-week long Cooperative Vulnerability and Penetration Assessment to determine how easy it was to hack the E-3G and its ground support system under realistic operational conditions.
"E-3G version 3.0 and supporting Block 40/45 ground systems are highly vulnerable to cyber threats and not survivable," the report tersely states.
That result finally led the program executive officer to decline to certify the E-3G as ready for follow-on operational testing, bringing the trials to a temporary halt. They are slated to recommence in two years once the software has been revised to address the demonstrated shortcoming.
What lay behind this disappointing performance? Though unable to comment on cyber-vulnerabilities, an Air Force spokesperson clarified the problem with the E-3's sensors in an email:
"The primary cause of errors is traceable to legacy analog sensors, which were not upgraded as part of the Block 40/45 modification. Block 40/45 integrates data inputs from multi-sensor on-board and off-board systems, which provides the operator with a "single target-single track" capability. The current version of AWACS, Block 30/35, does not integrate its information to provide a single track, so the mission crew must take the information provided and manually create tracks from different sensor and communications datalinks."
The Block 40/45 upgrade has a reasonable objective—to equip the Sentry with the kind of adaptable, networked computing capabilities that we take for granted in modern home computers. However, those networked systems may also leave the aircraft vulnerable to hacking.
Indeed, both Russia and China have repeatedly demonstrated their ability to break into sensitive American military systems in the past few years.
The two nations have also invested heavily in electronic countermeasures to reduce the effectiveness of the sensors and networked systems so integral to the US military's way of war.
The program's annual report notes that the Air Force and Boeing should spend the next two years tweaking the software and hardware to reduce the Block 40/45's cyber vulnerabilities, prepare new training materials, and get the new operating systems to fuse tracking data effectively and accurately.
Meanwhile, many of the Air Force's E-3 crews may have to make do with the most sophisticated computer technology the 1970s and 80s had to offer.