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MATTER OF SURVIVAL

Accident numbers were up in 2013, but fatalities fell to a new low as the improved survivability engineered into modern hull designs brought casualty figures down

By: David Learmount

Last year, the world’s airlines proved that they could not maintain safety at the all-time high level they achieved in 2012. To put that in context, however, the 2012 figures had broken safety records by such a big margin that Flight International predicted at the time the figures would probably be a one-year spike.

Maybe 2012 was a spike, but not a dramatic one given that the results for 2013 are still good when looked at as part of a longer-term trend (see chart, below right). The global total of airline fatal accidents in 2013 was 26, up by five from the previous year’s record low of 21, but the number of fatalities in those accidents established a new record low at 281 – less than two-thirds of the previous lowest figure of 425.

The figures quoted here include accidents to cargo flights as well as passenger, and all types of genuine airline operation whether scheduled or chartered, including commuter airline commercial operations using aircraft like the single-turboprop Cessna Caravan.

Visible risk levels

Meanwhile, among large commercial passenger jets (5.5t and above), there were only four fatal accidents worldwide last year, killing 105 people. Nowadays, the majority of fatal accidents involve smaller commuter aircraft, usually powered by turboprops. However, two more big jets – a Boeing 747-400 and an Airbus A300-600 – suffered fatal accidents last year flying as pure freighters (see accident listings).

The extremely low fatal casualty figure in 2013 makes it look as if there were no serious accidents involving high capacity twin-aisles, but this is not true. It could be argued that the impressive survivability engineered into today’s hulls distorts visible risk levels when only fatal accident figures are used as a safety indicator. For example, in 2013, a Lion Air Boeing 737-800 and an Asiana 777-200 were involved in the sort of serious accidents calculated to give their passengers nightmares for the rest of their lives, but there were no fatalities in the first and only three in the second.

Fatal accident rate

The Lion Air aircraft, on a non-precision instrument final approach to Denpasar in stormy weather, crashed into the sea short of the runway and broke up, but all 83 people on board survived. The Asiana 777, also on a non-precision final approach but in excellent visibility, hit the sea wall short of San Francisco’s runway, broke up and cartwheeled across the airfield, but only three of the 323 occupants died.

Hull loss – rather than fatal accident – figures would paint a truer total risk picture, but neither is a perfect indicator. To obtain the precise risks from all angles, readers can consult the 2013 Safety and loss report from Flightglobal’s consultancy business Ascend.

The Ascend 2013 report is slightly different from this study in terms of which aircraft and operational categories are included, and prepares its data to inform the aviation insurance industry rather than the public.

Nevertheless, it comes up with an understandably similar verdict on last year’s safety performance: “2013 was another good year for safety with a fatal accident rate of one per 1.9 million flights. This was not as good as the 2012 rate of one per 2.3 million flights, but is still considerably better than all other previous years [see chart, below top]. The rate in 2011 was one per 1.4 million and the average over the last five years is one per 1.6 million flights.”

Providing a longer-term context, the Ascend report explains: “Although some years have been better than others, the fatal accident rate has been improving for many years. At the start of the 1990s, the rate was about one per 0.6 or 0.7 million flights.

Therefore, based on this metric, airline operations are now almost three times safer than they were 20 years ago.”

Ascend’s safety director Paul Hayes points out that an obsessive concentration on the few serious accidents each year can blind the observer to the modern industry’s unprecedented safety levels. He adds that with so few accidents now in each 12-month period, a year is even less of a reliable indicator of general standards than it used to be. The comparison between the last two years is a good example of the limitations of a one-year assessment: an exceptional 2012 was followed by an apparently much worse 2013, but the latter is actually more representative of the present reality as measured using a five-year rolling average.

In 2013, happily, there was only one example of the dramatic loss of control in-flight (LOC-I) accidents that have become the single biggest cause of aviation fatalities in recent years: the Tatarstan Air 737-500 which crashed at Kazan, Russia, during a mishandled go-around.

In fact, it appears to be one of those LOC-I accidents which the Flight Safety Foundation has labelled “lack of control”, on the basis that the aircraft was controllable, but the pilot failed to exercise appropriate control for some reason.

TRAINING SHORTFALL

Over the last five years or so, pilot failure to manage go-arounds well – even if they do not end in an accident – has become a serious worry at the airlines and with both the major big-jet manufacturers. In recurrent training, pilots never face an all-engines go-around, they only have to demonstrate competency in an abandoned approach with an engine failure.

In the latter, the aircraft’s climb rate and pitch-up tendency are both gentle, whereas if pilots apply take-off/go-around thrust to terminate an approach, the pitch-up tendency is strong and the climb rate dramatic – which they are not accustomed to.

The crash of the National Air Cargo 747-400F at Bagram, Afghanistan, was a real out-of-control accident in the sense that the aircraft was clearly outside its flight envelope well before it hit the ground, and pilot attempts to recover were likely to have been futile. Although no formal information has been made available, the suspicion is that the freight shifted aft during the take-off run or after rotate, because video footage of the early climb clearly shows that pitch-control was lost.

Among the other jet crashes, there have been some more traditional accident scenarios, particularly the SCAT Bombardier CRJ200 crash in January 2013 on an instrument landing system (ILS) approach in fog at Almaty, Kazakhstan. This appears to have been a classic poor visibility accident in which the crew either failed to monitor glidepath and speed or deliberately ignored the glidepath guidance in hope of making visual contact with the runway lights.

The same appears to be true of the Lion Air 737-800 approach at Denpasar, except it was on a non-precision approach using VOR/DME guidance. The crew clearly elected to continue the approach through their decision height without having sight of the runway, and eventually paid the price for it with a broken aeroplane. Similarly, the UPS A300F crew at Birmingham, Alabama, was carrying out a non-precision localiser/DME approach at night when the aircraft hit rising ground on short final approach. It did not help that the runway had only edge lighting and no approach lights.

Human error

The Asiana accident – the first-ever fatal accident for a 777 – was in a category that is becoming more common: the pilots’ failure to monitor or control the aircraft’s airspeed and rate of descent on approach. It was disclosed at the routine public hearing on the accident that the National Transportation Safety Board’s interview with the pilots revealed another factor – the pilot’s admitted unhappiness with carrying out an approach with the ILS glideslope inactive, even in daylight and good visibility.

It became clear in the interview that the pilot flying, a new captain under instruction by the examiner in the right-hand seat, did not completely understand the autopilot and autothrottle modes, but was also reluctant to trip them out.

A manual selection of the throttle levers to idle because the aircraft was too high on the early approach did not disconnect the autothrottle, but put it in “hold” mode, so the engines remained at idle and the aircraft gradually dipped below the approach path, simultaneously slowing the 777 to an airspeed far less than the commanded 136kt (252km/h).

The pilots did not know about the “hold” mode and assumed that the autothrottle would work as normal. This is not the first time the autothrottle mode has confused pilots: it confused EASA test pilots when they were testing the 777 and 787, but they were monitoring the aircraft’s behaviour so no ill came of it. The Asiana pilots failed to recognise that the power levers did not move again and did not monitor the aircraft’s speed or descent profile until it was too late.

It has taken around 1,300 deaths from LOC-I accidents in the last 20 years for the industry to recognise, formally, that highly automated cockpits are de-skilling pilots in subtle but dangerous ways, and that they are not taught properly how to make best use of the sophisticated flight management systems. Finally, however, the US Federal Aviation Administration has -published its long-awaited study by the Commercial Aviation Safety Team (CAST) Flight Deck Automation Working Group (dubbed FltDAWG) entitled The operational use of flight path management systems.

This FAA-led work is a seminal report and it is the first attempt by an aviation authority anywhere in the world to define the problem rather than treat the symptoms.

Yet the FltDAWG has not proposed solutions, it has just defined what needs to be solved. The FAA has handed the task of deciding what should be done over to the Air Carrier Training Steering Group. When solutions have been agreed, airlines would then be under pressure to adopt the recommendations voluntarily. The agency cannot impose regulatory solutions because, with safety in the USA as good as it is, new regulation would fail the cost-benefit analysis test even if it would, one day, save lives.