TCAS has done a remarkable job of helping pilots avoid midair collisions, providing a last line of defense in those all-too-common instances when two aircraft are racing toward a single point in the sky at precisely the same moment.
Few collisions have occurred in the last several years, thanks to federal mandates for TCAS in large passenger-carrying airplanes. Now, air-cargo operators, which had been exempt from TCAS rules, are at long last being required to install traffic collision and alert systems as well.
Pilots who make the switch from smaller aircraft not fitted with TCAS to those that carry FAA-approved equipment are usually surprised to see just how many other aircraft are out there–concealed by the haze or lost in the bright sun, but easily identifiable on a cockpit display and, more important, by attention-grabbing traffic and resolution advisories, TAs and RAs for short.
Yet air-cargo operators have been arguing for years that it would be a waste of money to buy “old” TCAS technology for their fleets when new technologies such as automatic dependent surveillance-broadcast (ADS-B) have shown such promise. The FAA, while recognizing ADS-B’s importance to enhancing tactical situational awareness and making the future Free Flight environment possible, disagrees that cargo carriers should get a pass on TCAS.
Responding to congressional legislation passed in April 2000, the FAA ruled last month that many cargo-dedicated airplanes will be required to have TCAS installed by December 31 next year.
Under a previous rule, the TCAS requirement was based on passenger seating capacity and therefore excluded cargo-only airplanes. Since 1993 the FAA has required that airliners carrying 30 passengers or more be equipped with TCAS II. Two years later, it amended the rule to say that aircraft with 10 to 30 seats needed to have TCAS I on board. But the new rule uses airplane weight as the basis for collision avoidance system requirements. It applies TCAS II to cargo airplanes with mtow of 33,000 pounds or more. All piston-powered airplanes, regardless of weight, conducting operations under FAR Parts 121 or 125 will now also be required to carry TCAS I.
In anticipation of the new regulation, United Parcel Service (UPS) will soon add flight-deck displays to its Boeing 757s and 767s that are capable of simultaneously displaying the locations of all TCAS- and mode-C equipped aircraft, as well as the locations of ADS-B- equipped aircraft and ground vehicles, with each target showing its relative track and altitude and whether it is climbing or descending.
ATC facilities next year will begin using an ADS-B derivative called traffic information service-broadcast (TIS-B) to uplink data for aircraft that carry neither TCAS nor ADS-B, and these will also appear as targets in the UPS airplanes. The plan is to provide pilots with complete, real-time situational awareness of nearby traffic and a tactical view of more distant targets.
UPS subsidiary UPS Aviation Technologies (UPSAT) of Salem, Ore., developed the combined display, called a cockpit display of traffic information (CDTI). The FAA certified the system in February to provide both short-range TCAS alerts for immediate collision-avoidance guidance and the much longer- range picture of ADS-B traffic, in some cases out to more than 200 nm.
“This technology will give UPS pilots unparalleled visibility of traffic around them in the air, as well as on airport taxiways and runways,” said Capt. Rick Barr, vice president of airline operations at UPS. “The intent is to give pilots the best information possible, so they can make decisions safely, quickly and accurately.”
Most experts now agree that rather than serving as replacements for TCAS, newer technologies such as ADS-B and TIS-B will complement today’s onboard traffic alert systems and thereby provide extra margins of safety.
Some experts have argued that such long-range technologies could have helped prevent the midair collision of a Russian airliner and DHL freighter over Germany last July. Sixty-nine passengers and crew aboard a Tupolev Tu-154M owned and operated by Bashkirian Airlines were killed when it collided with DHL Flight 611, a Boeing 757-200 freighter. The two DHL pilots, the only occupants aboard the 757, were also killed. The accident has the distinction of being the world’s first midair collision involving two aircraft equipped with TCAS. It was also the first midair collision over Europe since 1976.
ADS-B to the Rescue
Adding to its hard-won prestige, ADS-B technology was recently credited with helping rescuers come to the aid of a downed pilot in the mountains in southern Alaska. Controllers at Anchorage Center last October used ADS-B to pinpoint the location of a Cessna 207 that had crashed at night in heavy turbulence soon after departing Marshall Airport in southwest Alaska for an intended 65-nm flight to Bethel, the airplane’s home base.
When the Cessna’s pilot was more than an hour late returning, the FAA and state troopers were notified and within 20 minutes a National Guard Black Hawk was in the air on its way to the downed Cessna’s last reported position, as reported by Anchorage controllers who had data from the airplane’s onboard ADS-B system. Aided by night-vision goggles, it didn’t take rescuers long to locate the pilot, who was huddled in the rear of the demolished airplane with a broken leg and ankle, but otherwise in good shape.
The Part 135 airplane was equipped with an ADS-B system as part of the FAA’s Alaska Capstone program, which provides special avionics to about 200 general aviation airplanes operating in the Yukon-Kuskokwim Delta. The goal is to reduce accidents in a region where there is no radar, the terrain is rough and weather can turn bad quickly.