Fixes Elusive For Unstable Airport Approaches

By John Croft
Source: Aviation Week & Space Technology
November 11, 2013
Credit: EPA/Landov File Photo

How pilots decide when and where to abandon a faulty approach or landing is the topic of intense research and study in the aviation community as accidents in that phase of flight continue to dominate all others.

While new procedures and better training and monitoring are high on the list of near-term interventions, there is a growing consensus that a technology solution that removes much of the sometimes-murky decision process should be part of the long-term fix.

In 2011, the approach-and-landing phase accounted for 65% of all airline accidents, with 13 accidents in the approach phase, 46 in the landing phase and four as part of a go-around maneuver, according to data from the International Air Transport Association. Last year was “almost identical,” says Bill Curtis, an airline pilot and co-chairman of the Flight Safety Foundation's (FSF) go-around decision-making and execution project, adding that the numbers have been fairly consistent since 2001. “We're not moving the bar at all.”

This year will be consistent with previous ones, judging by three high-profile crashes already in 2013: the undershoot crashes of a Lion Air 737-800 in Bali and Asiana Flight 214, a Boeing 777-200ER, on a visual approach to San Francisco; and the collision with terrain of a UPS Airbus A300-600 freighter on short final to the Birmingham, Ala., airport.

Experts say many of these crashes could be avoided by simply abandoning an “unstable” approach with a go-around maneuver. The FSF says failure to perform a go-around was a factor in 83% of approach-and-landing accidents in jets and turboprops in 1980-96 and the leading cause of landing runway excursions in those accidents. Curtis calls go-arounds the “largest, lowest-hanging piece of safety fruit” available to the aviation industry.

Several independent analyses, however, reveal that pilots rarely perform a go-around at pre-defined “approach gates” if stabilized approach criteria are not met. hile the criteria and gates vary between airlines, the generally accepted rule is that instrument flight rules (IFR) approaches must be stable by 1,000 ft. above runway height, and visual flight rules (VFR) approaches must meet stable criteria by 500 ft. If the approaches later become unstable below those altitudes, guidance by the FSF calls for an “immediate” go-around.

According to Honeywell, an approach is generally considered stable at the IFR or VFR approach gate if the landing gear is down, landing flaps are set, aircraft speed is within +10 kt. or -5 kt. of the final approach speed and descent rate is less than 1,000 fpm.

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