Plane & Pilot
Tuesday, September 6, 2011

When Airplanes Collide: Avoiding The Unexpected


With midair collisions showing no sign of decreasing, “See and Avoid” is more important than ever



10 Avoidance Techniques

Once pilots understand the limitations of their eyes, they can employ other methods to reduce the likelihood of a midair collision. In today’s world of visually compelling electronic displays, it takes a concerted effort to divert our eyes from the cockpit to the outside world, though that’s one of the keys to “see and avoid.” There are a number of other traffic-avoidance techniques pilots should work into their normal procedures:

1 If under IFR control or on flight following with ATC, don’t rely on ATC to keep you away from other aircraft. Traffic avoidance is the most basic and irrevocable responsibility of a PIC.
2 Fly at proper VFR cruising altitudes (when above 3,000 feet AGL, fly at odd thousands + 500 feet on headings of 0 to 179, and even thousands + 500 feet on headings of 180 to 359).
3 Use any and all exterior lights to make yourself more visible. Turn on strobes and nav lights, and turn on landing lights within 10 miles of an airport.
4 Navaids, approach fixes and checkpoints still attract crowds. Fly to the right of course at these points along your route, and stay extra vigilant.
5 Maintain a “sterile cockpit” within five to 10 minutes of approach and departure. This allows you to concentrate on traffic avoidance without distraction.
6 Always use flight following (radar traffic advisories). Though separation remains the PIC’s responsibility, a second set of eyes looking out for traffic is useful.
7 Follow correct communication procedures. Use standard phraseology and ask for clarification if you don’t understand the controller or lose sight of traffic that has been called out to you.
8 Fly with sunglasses. Professional-grade sunglasses (as opposed to cheapie plastic sunglasses) reduce glare and eye fatigue. Know that polarized lenses can block the glint off a conflicting airplane’s wing, making it difficult to see.
9 At nontowered airports, report your position 10 miles out and again on each leg of the pattern. Have radio frequencies predialed to keep your eyes outside the aircraft. Follow AIM-suggested entry/exit procedures to the field, and give position reports outbound (most pilots don’t).
10 Check for traffic behind and below you at least once when on final. Have passengers look for traffic near the airport and in the pattern.

TCAS

Research began in the early 1950s on an airborne-collision-avoidance system. After decades of development and evaluation, the FAA introduced an early form of a traffic-collision-avoidance system (TCAS) in November of 1993, which was officially recognized by the International Civil Aviation Organization (ICAO).

Further technical development brought TCAS where it is today. The Airport and Airway Safety Expansion Act and ICAO now require all civil air carrier aircraft to be equipped with TCAS.

TCAS works independent of air traffic control, and monitors the airspace around an aircraft by looking for signal returns from other aircraft equipped with a transponder. TCAS-equipped aircraft scan in a predetermined range using the 1030 MHz radio frequency, and look for returns on the 1090 MHz frequency. The interrogation response occurs many times per second and creates a three-dimensional map of the airspace. The system warns pilots when it senses another transponder-equipped aircraft in close-enough proximity to induce a possible midair collision. Three components make up TCAS: a set of two or four antennas, the TCAS processing unit (computer) and a cockpit display.

There are two levels of TCAS systems. TCAS I was created for general aviation and regional carrier aircraft, and issues traffic advisories (TAs) to help pilots see conflicting traffic. TCAS II is the current generation, and is more sophisticated in that it analyzes the projected flight path of conflicting aircraft and issues resolution advisories (RAs) to pilots to resolve midair conflicts. Today, TCAS II is required internationally in aircraft with more than 30 seats or weighing more than 15,000 kg. The latest revision of TCAS II standards are referred to as “Version 7” in the United States.



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