The Logan test is one of four run by the Federal Aviation Administration around the country. If the systems turn out to be better than the human eye, usually watching from behind the windshield of a car, the F.A.A. intends to publish standards for such systems. Then airports could apply for federal money to buy them.  The exact cost is not clear yet, and the airlines are not eager to see an airport spend money on anything that could increase landing fees. But others see obvious benefits.  “Anytime we can keep an engine as near pristine as we can, it adds to the safety factor,” said Thomas J. Kinton Jr., chief executive of the Massachusetts Port Authority, which operates Logan.  Jet engines are extremely reliable, one of the reasons that air travel is so safe. But they are vulnerable to foreign objects, and F.O.D. sucked into engines can cause failure or expensive damage. And even in cases with little safety risk, the cost of the repairs and of lost time for the aircraft runs into the billions of dollars a year, according to estimates by Boeing and the F.A.A..  Part of the problem is birds, but a major cause is debris that could be cleaned off a runway if it were located promptly.  Jim Patterson Jr., an airport safety specialist with the F.A.A., is running a program to determine how reliably a mechanical system can detect small objects. The Concorde crash added urgency to the effort but F.O.D. has been a problem for years, he said.  Experts say the Concorde was more vulnerable than most airliners, but so are military planes, many of which have only one engine, only one tire on each landing gear, and engines that are very close to the ground.  One of the four systems being tested by the F.A.A., built by Xsight Systems, of Rosh Haayin, Israel, uses both a camera and a radar, and is installed adjacent to runway edge lights, one every 200 feet.  F.A.A. rules prohibit anything tall next to the runway, and the runway is crowned like a road, to help water drain, so the Xsight system being tested at Logan needs one on either side.  In the current test, there are seven monitors, covering about 1,000 feet at the northwest end of the runway. Both the camera and the radar compare their data to an image of a clean runway, and look for changes. Software developed by Oded Hanson, the co-worker in the tower during the system test, helps the computer ignore things that are supposed to be there, like airplanes.  A few miles away, in Providence, R.I., the F.A.A. is testing a competing system built by QinetiQ, of Farnborough, England, which uses radar alone, on pylons near the runway. It has been used at Vancouver International Airport in Canada for two years.  On March 12 the Vancouver system found a 30-foot long steel grounding cable, the type used to dissipate static electricity in fueling operations. The system has previously found everything from paper bags to feathers, but the cable was “potentially very hazardous,” said Brett Patterson, director of aviation operations there. Damage that it could have caused might have exceeded for the cost the system, he said.  Mr. Patterson said he could not give an exact figure, but the system sold for $2 million to $3 million a runway.  And in March, at Midway in Chicago, the agency began testing a system built by the Trex Enterprises Corporation of San Diego that is mounted on top of a truck and can be driven down the runway, and also over taxiways and into ramp areas in front of the gates. . It uses a radar and an infrared camera.  At O’Hare in Chicago, the F.A.A. is testing a fourth system, by Stratech Systems Ltd. of Singapore that uses a high-resolution camera mounted at a central location.  For all the systems, the F.A.A. uses a set of test objects that includes fuel tank caps, chunks of concrete and pieces of airport signs. At Logan, testers have painted dots on the runways where they drop the test objects, so they can run the evaluation the same way on successive days, to see how it works in direct sun with shadows, in rain and snow, and shimmering heat.  They also put objects at various angles, to see how that affects the ability of each system to see them. More testing may be needed for objects peculiar to particular airports; at Logan, for example, sea gulls drop clams on the runway; other airports have problems like tumbleweed.  One question is whether the probability of detecting an object mechanically is higher than with the human eye. Current practice is for airport personnel to drive down the runway every two hours or so. But an automated system has another advantage over the human eyeball, because sending a truck out to look raises the risk of runway collision.  An inspection every two hours is not nearly frequent enough to head off a chain of events like the one in the Concorde crash. A system that detects debris within seconds gives the airport a chance to warn the airline that one of its planes has shed parts, said Alon Nitzan, president and chief executive of Xsight.  It would also help establish liability. In the Concorde case, that could turn out to be criminal; a judge in Paris is expected to decide this summer whether to proceed with involuntary homicide charges against two employees of Continental, one official of the company that built the Concorde and one French air safety regulator. The legal issue is whether the four men did everything they should have to assure safety.  Xsight hopes to mass-produce an inexpensive system by using radar already in production for cars and trucks, and used in advanced cruise control. In that application it slows the car down if it senses traffic ahead.  When it spots debris, it uses a laser pointer to guide an airport worker to its location. In contrast, pilots often report runway debris to the tower, but their description of the location is less reliable, because it is often given as they speed down the runway at over 100 miles an hour.  F.O.D. is a hazard all over the airfield but damage can be larger at the beginning of the runway , which is where the Boston system is being tested, said Brad Bachtel, manager of airport technology at Boeing.  That is where pilots open jets to full throttle, so they can suck in as much air as possible and thus are “at maximum Hoover factor,” he said.
A sensor is being tested by the Federal Aviation Administration to detect debris that can damage airplane engines on takeoff or even lead to plane crashes.