The S-3 Viking was described as the Swiss Army Knife of Naval Aviation for good reason. Throughout its nearly four decades of frontline service with the US Navy, the S-3 took on many roles ranging from carrier-based antisubmarine and antisurface warfare; to carrier onboard delivery; to tanking; and, finally, to an intelligence, surveillance, and reconnaissance asset.
The S-3 also served as a test aircraft. Over its career, special projects with names like Outlaw Viking, Gray Wolf, Beartrap Viking, Orca Viking, and S-3B Surveillance System Upgrade were tested on the Viking.
The Navy retired the S-3 from fleet service in 2009, but a trio of the remaining Vikings has once again donned lab coats—only now the research takes place at the NASA Glenn Research Center in Cleveland, Ohio, which has been conducting all manner of aeronautical research since 1942.
“The S-3 was designed to track and kill a submarine, with the ability to get on station quickly and have long endurance. The combination of two powerful, efficient, turbofan engines and a large-capacity electrical system makes the Viking a really good platform for us,” said James Demers, one of two S-3 project pilots at NASA Glenn. “This aircraft works particularly well in scenarios that call for us to loiter and go low and slow.”
Early last decade, the Navy decided to retire the S-3 and, accordingly, started to draw down the Viking fleet. Around 2006, officials at NASA Glenn recognized the Viking’s potential as a research platform and worked with the Navy to get three S-3Bs transferred to the center.
The first aircraft, Navy Bureau Number 160607, is the prime test aircraft at NASA Glenn. This aircraft, which rolled off the assembly line in 1978 as the last of the 187 S-3s built, is now known as NASA 601. Flight testing is not a new tasking for this particular Viking as it had been assigned to VX-20, the S-3 test squadron at NAS Patuxent River, Maryland, for much of its career. After undergoing full depot-level maintenance and extensive modification that took nearly two years at NAS Jacksonville, Florida, NASA 601 was flown to Cleveland in January 2008.
Much of the military-specific equipment on the Viking was removed to reduce weight and maintenance costs. Other equipment was removed simply because it was not needed. “We fly this aircraft to collect data for a researcher. We need to get airborne, get the data, and get back on the ground,” noted Demers. “And we have to do that safely and reliably.”
To prepare the S-3 for its new role, the aircraft underwent a significant interior change. “We have eight aircraft at this center, and they all have standardized cockpit instrumentation,” said Demers. “For instance, the center has a commercial GPS navigation system in our T-34s, our Learjet, the Twin Otter, and in the S-3. That system is very effective for the type of flying we do, typically operating from commercial or general aviation airports. The spare parts for our cockpit instrumentation are all interchangeable. Our two center avionics technicians don’t have to know how to maintain multiple systems. Pilots can easily go from aircraft to another.”
Aircraft-specific equipment now only takes up about the first third of the S-3’s main avionics bay. The additional space provides room for a set of nineteen-inch wide avionics racks that can be fitted with test-specific gear, such as sensor controls and recording equipment. What had been the two crew stations in the aft cockpit now houses a computer keyboard with a connection that allows data from the aircraft’s two independent data systems to be loaded directly onto a researcher’s computer through a 1553B high-speed data bus.
Orange grab handles, Plexiglas covers over aircraft avionics and electrical systems, and new LED lighting were also installed in the avionics bay. “The center’s Safety Committee said we had to ‘baby proof’ the jet,” noted Demers. “Non-regular flyers, such as the researchers, may only make several flights over the course of their research project, but we have to be able to accommodate them.” Part of that accommodation involved deactivating the ejection seats.
Through early 2011, NASA 601 had accumulated about 100 test hours on aeronautical research and earth sciences projects. The Great Lakes Environmental Assessment Mission, or GLEAM, is a good example. “This project is designed to measure—from the air—algae growth found in the Great Lakes. We first tested the sensor on the T-34 and then took the sensor to altitude on the Learjet. Later this year, we’ll conduct an operational test with it on the S-3,” said Alan Micklewright, NASA’s chief S-3 pilot. “The S-3 will enable more data collection than from either of those other two aircraft.”
One of the other two NASA S-3Bs serves as a fit-and-function ground test vehicle. The role of the other Viking, now a spare, could soon grow. The Glenn Center has obtained several of the large underwing cargo pods used on the US-3A carrier onboard delivery aircraft in the 1970s. Rather than modifying the aircraft for a future test, the NASA team wants to modify the pods to carry sensor equipment that can easily be switched out for future tests.
Potential future projects for the S-3 include next-generation airspace communications research, propulsion research, swept wing icing, and atmospheric science projects. The aircraft may also be used in the FAA-sponsored Unmanned Aerial Systems in the National Airspace System research.
“The S-3 operates in a niche part of the flight envelope, and it’s very cost-effective for NASA to fly,” observed Micklewright. “But the reality is that this aircraft has to earn its keep. We’re always looking for new projects or to team with other agencies, like with the Air Force Research Lab, on their projects.”
“We don’t fly our S-3 from a carrier; we don’t have nugget pilots; and we don’t beat the aircraft up in daily shipboard operations. We do research flights under controlled conditions and then put the aircraft to bed in a hangar. We have experienced maintainers and a large supply of spare parts,” concluded Micklewright. “The S-3 is going to be a valuable research platform for the foreseeable future.”