Safety experts call attention to prevalence of unstable approaches

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Safety executives at many airlines underestimate dangers posed by unstable approaches, and airline policies do little to ensure pilots follow company procedures for unstable approaches.

That is the message from aviation safety experts and academics who spoke today at the Flight Safety Foundation’s International Air Safety Summit in Washington, DC.

“The risk of approach and landing accidents is too high,” Ewout Hiltermann, safety manager at KLM Cityhopper, tells attendees at the summit. “Too many accidents are happening every year... [Current] risk control is not effective enough.”

Hiltermann points to industry data showing that between 3% and 4% of approaches are unstable — meaning there are roughly 1,000 unstable approaches every day — but pilots abort landing and execute go-arounds in only 3% of unstable approaches.

Those statistics are concerning because 65% of commercial aviation accidents in 2011 occurred during the approach and landing phase of flight, Bill Curtis an advisor to social science research company Presage Group, tells attendees.

The data also shows that 83% of those accidents could have been prevented had the pilots executed a missed-approach, says Curtis.

So far this year there have been three notable accidents in the US that occurred during approach and landing.

Those include the Asiana Airlines Boeing 777 that smashed into a seawall at San Francisco International airport on 6 July, the crash landing of a Southwest Airlines 737 at New York’s LaGuardia airport on 22 July and the crash of UPS Airbus A300-600F near Birmingham-Shuttlesworth International airport on 14 August.

The UPS crash killed both pilots and the Asiana crash led to the deaths of three passengers. The Southwest crash did not cause fatalities.

Another speaker, Presage Group’s chief executive Martin Smith, says airlines’ safety managers sometimes do not know or appreciate the extent of the problem.

Data from a recent survey shows that 68% of managers did not know the industry-wide rate at which pilots comply with unstable approach procedures, and 55% did not know the compliance rate at their own companies, says Smith, whose company predicts human errors and non-compliance with procedures.

In addition, 22% of safety managers said their company’s procedures for unstable approaches and go-arounds are ineffective, Smith says.

‘[There] is a... disavowal of empirical evidence. It’s stark. It’s wrong,” says Smith.

A number of factors lead pilots to continue with an unstable approach, such as “perceived punctuality pressure,” misperceptions of flight conditions like height above the runway and the perception that landing is safer than a go-around, says Hiltermann.

He recommends airlines take advantage of flight data to help identify unstable approaches and find solutions, a technique used by Cityhopper.

The data can show the prevalence of unstable approaches and help pinpoint contributing factors, such as the speed and configuration of the aircraft, Hiltermann says.

Cityhopper assesses unstable approach data and reviews the data with crews, which often reveals that pilots’ perceptions of the landing differ from the data, he adds.

Stable Approaches

Data also shows that many runway excursions occur despite a stable approach, says Scott Winter, president of Flight Safety Foundation’s student chapter at Purdue University.

Winter says a study conducted by students shows that 35% of 520 runway excursions between 1995 and 2010 followed a stable approach. The excursions were caused by factors like runway contamination and landing outside the touchdown zone.

“We were somewhat surprised to see that... a stabilised approach doesn’t guarantee you have a safe landing,” Winter tells attendees. “Even though the approach is stabilised... its still necessary for the flight crew to fly the aircraft all the way through the landing.”