Planes' safety system causes near-miss

By Matthew Brelis, Globe Staff, 6/10/2000

Two commuter airplanes being handled by air traffic controllers at the Boston Center in Nashua nearly collided in flight Sunday morning when their computerized, on-board safety equipment brought them to within 600 vertical feet.

A US Airways Express aircraft with 10 people on board and a Jetlink plane were flying over upstate New York near the Pennsylvania border when the traffic collision avoidance systems, known as TCAS, put them on a collision course.

''We had a TCAS event leading to a loss of separation,'' the minimum safe distance between aircraft, said Federal Aviation Administration spokesman Jim Peters.

Peters said both planes were flying level when TCAS on the plane at the higher altitude instructed the pilot to dive, while TCAS on the plane at the lower altitude ordered the pilot to climb.

Paul McCarthy, safety chairman of the Air Line Pilots Association, said such a scenario ''would surprise me greatly.''

If two planes were nearing each other and one was already climbing and the other was in a descent, then TCAS would issue instructions for the ascending plane to continue to climb and the descending plane to keep diving, McCarthy said.

The FAA has turned the investigation over to ARINC, a Maryland-based company that is owned by domestic and international airlines and aircraft operators. ARINC supports communications and information processing for the aviation industry and provides guidance for establishing standards for aviation equipment.

A company spokesman said he had no information on the investigation or how frequently TCAS commands result in near-misses.

TCAS is required on all planes with 10 or more seats and has been praised by pilots as a safety tool. Since it came into wide use more than a decade ago, the number of reported near-collisions has dropped dramatically, even as the number of flights has increased.

The US Airways Express Flight 3865, a Dash-8 aircraft which seats 37, was flying from New York's LaGuardia Airport to Syracuse and was at 14,000 feet about 15 miles south of Hancock, N.Y., traveling to the northwest. Jetlink Flight 3641 was north of Hancock flying at 13,000 feet, on a southeastern course.

Hancock is about 50 miles east of Binghamton, N.Y. The origin and destination of the Jetlink flight and the number of people on board could not be determined yesterday.

The FAA's Peters said the following then occurred:

A controller in the Boston Center noticed that the Jetlink's altitude reading on the radar screen was intermittent and asked the airplane's pilot to verify its altitude. The pilot radioed that he was at 13,000 feet.

The controller then advised the US Airways flight that traffic was in the area. Within minutes, the US Airways pilot told the controller that ''he received a [TCAS warning] and was told to descend by TCAS.'' Radar readouts show the plane descended from 14,000 feet to 12,200 feet.

The Jetlink flight advised the controller that TCAS had instructed his aircraft to climb and that he flew from 13,000 feet to 13,200 feet.

FAA analysis shows that the two aircraft came within 600 feet vertically and about 11/2 miles horizontally. In that airspace, a safe distance is considered to be no less than 1,000 feet vertically and 5 miles horizontally.

Peters said that because the incident was not the fault of the controller - a so-called operational error - the agency has not investigated. He said the FAA does not keep track of the number of incidents in which there is a TCAS-generated loss of safe separation.

But 18 months ago, the same thing happened to a Northwest Airlines jet flying from Detroit to Bradley Internatioanl Airport in Connecticut and an Air Ontario commuter plane en route from Providence to Toronto. That incident happened in roughly the same airspace - about 30 miles south of Albany - as Sunday's TCAS malfunction.

In the Northwest-Air Ontario incident, TCAS told one plane to dive and the other to climb, and they closed to within 300 feet. An air traffic controller working in the Boston Center alerted the two flight crews to the danger by shouting, ''Traffic!

http://www.boston.com/dailyglobe2/162/metro/Planes_safety_system_causes_near_miss+.shtml

-- Martin Thompson (mthom1927@aol.com), June 10, 2000

Answers

"Two commuter airplanes being handled by air traffic controllers at the Boston Center in Nashua nearly collided in flight Sunday morning...." And, halfway through the article, it mentions "yesterday." What's going on? It's 2015 MDT, Saturday, June 10 right now.

-- Rachel Gibson (rgibson@hotmail.com), June 10, 2000.

Reporter probably didn't check the story. Like me spelling Japanese as Jabpanese.

-- Martin Thompson (mthom1927@aol.com), June 10, 2000.