Robot ‘N-Ray’ to Rescue : Air Force Neutron Gun May Probe Jetliner Innards for Corrosion

In a concrete fortress, a huge military robot with a neutron ray gun in its claw is looking through metal like Superman to spot deadly corrosion in fighter jets. Its creators say it could do the same for commercial airliners.

The potential of the unique new machine at McClellan Air Force Base has added a major element to the federal government’s search for ways to make commercial air travel safer after a series of problems with aging jetliners.

The Federal Aviation Administration has commissioned a study on high-technology structural testing methods that will focus in part on whether versions of the $7.3-million robot and hangar at McClellan would be practical for use on airliners.

The report on the corrosion-detection system took on greater significance with word the government is preparing orders that will force airlines to regularly strip the interiors of aging jetliner fuselages, which have failed in some cases, for corrosion inspections.

In interviews, airline industry representatives said there are major drawbacks to the system. But engineers who created the machine said it could be applied to the private sector and would fill a gap in airline testing.

Doug Froom, who designed the device, which is the first neutron-ray or “N-ray” system in the world to move and scrutinize an intact aircraft, said he hopes airlines will adopt the technology.

There’s no reason for structural failures that have hit aging airliners, Froom said. “You’ve got to find that Achilles heel. That’s what this system is good at.”

Private engineers who build the machine said larger versions of the system could be designed to scan entire airliners within hours, ending the time-consuming process of dismantling and visually inspecting for corrosion.

Airline industry representatives, however, said there would be multimillion-dollar costs to each of the competing airlines. Practical complications include coping with the radiation it gives off and adapting the machinery so that it could quickly scan airliner fuselages, they added.

Air Transport Assn. spokesman Dave Lotterer said that although airlines rely heavily on visual checks, X-rays, electrical currents and sound are being used more frequently to test portions of planes.

Consumer groups, which criticize the efforts as outdated and inadequate, said they want to make sure the controversy over N-ray centers on the effectiveness of the device rather than solely on cost.

“Any device that detects . . . evils that come with aging aircraft is certainly desirable to have available,” said Richard Livingston of the International Airline Passengers Assn. “If it reveals corrosion in the places in which traditionally it’s been hard to find, then what price safety? It’s hard to imagine anything costing too much to safeguard human life.”

Experts said corrosion can weaken essential aircraft components or the fuselage itself, causing major damage or possible crashes.

Recent airline accidents have been linked largely to metal fatigue and government directives have focused on that problem, but the latest federal orders are expected to require carriers to set up their own anti-corrosion programs with periodic inspections on various sections of each airliner.

Corrosion is more closely related than metal fatigue to age, the care the airliner is given, the environment in which it is flown, and conditions within the aircraft. Frequent coffee spills in the galley, for example, can accelerate corrosion.

The corrosion-detector at McClellan shoots neutrons, a particle in atoms, through an aircraft to a receiver on the other side.

Neutrons penetrate metal but are absorbed by the hydrogen in the dust produced by corrosion. The neutron flow is translated into a “real time” television image--one that can be watched live and recorded.

The scanner is held by a flexible arm that hangs from a moving overhead beam in a hangar with concrete walls thick enough to contain errant low-level radiation. The machine is operated from a remote-control center.

N-ray operators are programming the system to automatically scan jets, including the F-111 fighter-bomber, the largest in the Air Force. The facility, just big enough to take in an F-111, is scheduled to be in regular operation by mid-1990.

Adjacent facilities use X-rays, a longtime tool that is better at revealing structural damage such as cracks but less efficient at showing problems such as corrosion.

“With X-rays you can’t find the cancer. With N-rays you can, and when you find problems in the early stages, you go in, doctor it up and extend the life of the plane,” Froom said.

The X-ray facilities include a unit that, for the first time, will scan intact aircraft and provide a television image rather than just taking pictures that must be developed.

In addition, by March, the Air Force will be able to inspect flawed parts with a separate, stationary N-ray system at McClellan powered by a small, 1-megawatt reactor.

Together the systems, known as “non-destructive inspection” devices because they check planes and components intact, will cost $28.7 million. But Air Force officials say they should pay for themselves in reduced maintenance costs in up to two years.

The N-ray, for example, can do in 16 hours what human inspectors would need several months to do if they had to dismantle the aircraft.

Earlier this year, the FAA, which oversees commercial air transportation, awarded a New Jersey-based research firm, Galaxy Scientific Corp., a $47-million contract to study the N-ray and other inspection techniques.

“We’re seeking information for commercial application,” said Galaxy Scientific’s vice president, Bruce McCoy, who agreed with those who say the technology is excellent at detecting corrosion and could be used on airliners.

“But you can see where we’re in the middle, trying to bring technology through the gap” between expensive testing technologies and financially competitive airlines, he said.

From the military’s viewpoint, the expense of the N-ray is less than that of losing one aircraft.

The firm that built the N-ray robotics, Cimcorp Robotic Systems of St. Paul, Minn., said it could construct a machine big enough to scan the largest commercial airliner for roughly $30 million, not including the radiation-shielded building itself.

“You look at that cost against the cost of one airliner and that number (for N-ray) becomes small again,” said Ken Bucher of Cimcorp. A commercial jetliner can cost more than $100 million.

Industry representatives said N-ray appears impractical for several reasons, with cost near the top of the list. The military depends on tax revenue, while the profit-seeking airlines compete with one another, they said.

Airlines, unlike the Air Force, would each have to own a facility and perhaps several of them so they were handy, industry officials said.

Jack Gamble, a Boeing Co. spokesman, when pressed for the industry’s other complaints about N-ray, said: “I’m not going to give 10 reasons why we don’t want to use it. It’s a technical question.”

Many of the technical hitches cited by the industry are discounted by engineers who created McClellan’s N-ray.

Industry representatives said the materials in airliners are so different from jet fighters that N-ray would not be as effective as it is for the military, but N-ray engineers reject the objection as unfounded.

Industry officials noted that the machine does not swiftly scan fuselages now. Instead film is placed inside and exposed. But N-ray engineers said a receiving device could be designed to track inside an airliner’s passenger compartment, providing the “real time” scan that already is possible on areas such as wings.

It would be difficult for the private sector, which has to deal with workers’ unions, to manage a plant that involves radiation, according to the industry. But N-ray engineers said they use low-level radiation that is not difficult to manage.

Although N-ray proponents believe airlines should adopt the technology, they are skeptical that will happen anytime soon.

Froom believes it would take government pressure to force the airlines to widely employ N-ray: “The point of it is, the FAA’s got to drive them to it.”