SAFETY & SECURITY Last modified on July 6, 2012

Happy landings

Alexander Kandt and Fabrice Villaumé consider the dangers of airfield excursions and the development of new technology designed to prevent runway overruns.

The most frequent and costly cause of aviation accidents is  runway overruns, with 33% of hull losses (accidents after which the plane is written off) in the last 25 years occurring during the landing process.

Taking predicted air transport growth into account, Airbus and leading aircraft insurance broker, Willis, believe that these cumulated hull losses will top $9.2 billion by 2020.

And the total will be even higher in reality, as this figure only considers claims above $10 million and does not include the impact accidents have on airport infrastructure and airport/airline operational continuity.

There are, of course, many reasons for runway overruns during the landing phase. These include no realistically defined operational landing distance; destabilisation at low altitude (wind shift; runway conditions/friction being lower than reported (slippery runways; the misuse of retardation means (late selection of engine thrust reversers, late/weak pedal braking, inadequate auto-brake level selection; and failures affecting landing distances.

However, one of the major contributors remains ‘unstable’ approaches, to which the industry has responded by emphasising the need for training and procedures.

The need to avoid the scenario cannot be overstated,  because being in an unstable condition, and without having information on the risk of a consequent runway overrun, crews may be tempted to continue an approach in the belief that they may recover the situation or that they have sufficient landing distance margins.

In terms of the development of Runway Overrun  Prevention Systems (ROPS), Airbus has concentrated its  efforts on technology designed to significantly reduce runway overruns at landing.

In fact, its potential ROPS solution is based upon European Aviation Safety Agency (EASA)-certified technology that was first developed at Airbus in the late 1990s and entered into service in 2009 with the A380.

In essence, the simple objective of the technology is to assist flight crews during the approach and then on the ground, up to the moment when the aircraft stops.

The first phase of the potential solution involves the utilisation  of a Runway Overrun Warning (ROW) function during the final  landing phase.

It automatically detects the landing runway during the final approach, and then provides a real-time and continuous inflight landing distance assessment based on the actual aircraft’s  energy level.

If the system finds that the runway is too short for a safe landing, it gives a clear textual and aural alerting so the pilot can decide not to land but to make a go-around.

The second phase is a Runway Overrun Protection (ROP) system, which is automatically activated if the pilot decides to continue the landing after the ‘committed-to-stop’ point.

Indeed, if the remaining braking distance overtakes the remaining Landing Distance Available, the function advises the pilot with clear textual and aural alerting to set and/or keep the thrust reversers and to apply and/or keep full pedal braking.

ROPS constantly takes into account factors such as weather and runway conditions to compute landing and stopping distances and uses on-board system databases to compare them with the distances that are actually available.

And it is coupled to the mandatory Terrain Avoidance Warning System (TAWS) with a worldwide runway database fitted on most aircraft, effectively meaning that it works at all airports.

The new technology is designed to improve airfield safety by preventing runway overruns at airports.

EASA tests during the certification process for ROPS technology on the A380 back in 2009 demonstrated that in a realistic operating domain – as emphasised in the approved Aircraft Flight Manual – such a system would mean that it is highly unlikley that an aircraft could overrun the runway without triggering at least one alert.

Each alert also suggests a clear and simple course of action for the pilot to follow to avoid a possible runway excursion, ranging from ‘go-around’ and ‘maximum braking’ to the application of ‘reverse thrust’.

André Clerc, chairman of Willis, is certainly in no doubt about the importance of ROPS technology when it comes to runway safety at airports.

He says: “Airbus has demonstrated that with ROPS you can minimise one of the biggest safety risks to aircraft at landing. It is an extraordinary development in aircraft safety and will have a global impact.

“It is a technology which can be adopted by any type of commercial jet aircraft at a cheap price. This goes far beyond the European aviation industry and will be of interest to all commercial airline operators worldwide.”

While IATA director general, Tony Tyler, is quoted as saying: “There is a great deal of interest in making this one of the standard features of the industry.”

And the word appears to be spreading, as airlines such as Air France, Lufthansa, Emirates and Korean Air have already adopted ROPS and it will be installed on more than 80% of the A380s currently on order from Airbus.

It has also become standard for Airbus A350 XWB definition,  while for the Airbus A320 Family and A330/A340, a retrofit solution will be available that can be installed during a one-night stop  thanks to simple and cost-effective software upgrades of existing avionics equipment.

So what does all this mean for airports? In short, ROPS offers airports another source of immediate and tangible risk mitigation against one of their main sources of business interruption – runway excursions.

Most of you will already be aware of the tried and tested solutions to runway excursions such as crushable concrete arrestor beds or engineered materials arresting systems (EMAS) at runway end safety areas.

To these we can now add the name of the Airbus Runway Overrun Prevention System (ROPS).

About the authors
Alexander Kandt works for Munich-based technology supplier  EADS, and Fabrice Villaumé is business development director and ROPS co-inventor at Airbus.

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