Sink or swim

Land based aircraft have been forced to use water as an emergency ‘runway’ for almost as long as there has been powered flight.

While instances of ditching airliners are relatively rare, aircraft from Super Constellations to Convairs have ultimately ‘landed’ on water. In 2002, a Garuda Boeing 737- 300 was forced to ditch near Java, while closer to home a chartered DC-3 put down in Botany Bay in 1994 after both engines failed after takeoff out of Sydney.

What made the Hudson River episode so intriguing was the relatively unscathed appearance of both man and machine as it became evident that the ditching had been made with minimal or no thrust. In such a time critical emergency, there were so many factors at play working against the crew.

However, US Airways flight 1549 proved that sometimes the planets can align.

Against the Odds

The variables confronting a crew in any ditching situation are enormous. The available aircraft systems, the water’s swell, aircraft design features, time of day and proximity to landfall are just a mere handful of considerations that compete for the pilot’s attention when the nightmare of a ditching looms.

Achieving clarity of thought under such intense pressure is a key achievement in itself and is critical to a successful outcome.

As in all emergency situations, the overwhelming priority must be to fly the aeroplane. Even so, there will be factors beyond the crew’s control with which they will have to deal on the day.

Perhaps the most critical consideration in a ditching is whether or not the aircraft is still under power. A variety of aircraft have ditched over the years due to a lack of thrust. The reasons are varied, from flameouts in ice and heavy rain, to the serial offender of fuel starvation. Of those that have exhausted their fuel supply, some have done so unwittingly while attending to a lesser inflight emergency. Once again it gets back to the cardinal rule of aviation: fly the aeroplane Whether a ditching is to take place with or without power determines if the crew can afford the very critical component of time. The powerless Airbus on the Hudson had no such luxury as inertia and gravity dictated its timeframe once its engines had ingested that flock of geese.

Even when an aircraft’s remaining power may not be sufficient to maintain level flight it may provide enough time for the crew to limp closer to landfall, sustain various aircraft systems, or control the rate of descent in the final stages prior to impact.

Meanwhile in the cabin, this time can afford the flight attendants an opportunity to prepare the passengers and equipment for the ditching.

The availability of power will also determine the availability of aircraft systems, from hydraulics to electrics. While most airliners have 30 minutes of battery time to power minimal electrical systems, the resultant loss of hydraulic pressure may limit the amount of flaps and powered controls that are available to the pilot, depending on the particular system. A number of types, including the A320, are equipped with a ram air turbine, or RAT, that extends into the airflow and spins to provide an alternate source of power and pressure.

Aircraft design can also play a hand – whether the wings are mounted high or low and if the engines are under-slung on the wings, or aft-mounted on the fuselage.

All of these design features play a part, particularly in how the aircraft first contacts the water and decelerates. Once on the water, the low wing may assist egress,as the images of passengers standing on the wing in the Hudson so starkly illustrate, or hamper it in such types as Cessna singles where the door lies below the wing.

Whether the selected water body is a river, lake or ocean will also greatly influence the outcome of a ditching. While this can determine the proximity of the aircraft to landfall and rescue, it also can also dictate the water surface conditions. The prevailing swell is a major consideration in the execution of a ditching and, generally speaking, the ocean is the home to big swells. The American Great Lakes may have phenomenal seas, but generally a river or lake will present a more level surface for the aircraft to land on.

If an aircraft is forced to ditch at night, many of the visual cues may be lost unless a bright full moon can illuminate the whitecaps.

Early assessment of the water surface and swell may be impossible and a ‘best guess’ plan must be devised on the planned prevailing winds at a lower level. Descending in the darkness will also make the actual approach and touchdown far more difficult to judge as there will be no runway lights in the peripheral vision and no horizon ahead to assist in assessing the rate of closure. Flight instruments and radio altimeters will be critical in guiding the aircraft in the final moments, and support calls from the ‘pilot not flying’ (PNF) will free the flying pilot to divert some attention out the windshield to catch the first glimpse of the waves in the landing lights.

Similarly, poor weather and a low cloud base will greatly reduce the visual information available to the pilot to execute the manoeuvre. Breaking out beneath the cloud base at low level with rain thrashing against the windscreen may leave the pilot with less than a minute of poor visibility to guide his aircraft to the surface.

The crew of US Airways flight 1549 had daylight, reasonable weather and a relatively smooth water surface working in their favour. But – and it’s a BIG ‘but’ – they had lost both engines and were effectively in control of a 60 tonne glider. The crew had only minutes from losing the engines to touching down on the Hudson, during which they had to decide, plan and execute their course of action.

A Landing with a Difference

Landing on water is not the natural environment for aircraft not equipped with floats or a hull. Each manufacturer will make recommendations on how to best ditch its aircraft, though thankfully it is often not from the voice of experience. The advice may stem from computer models, similar past ditchings or pure hypothesis.

Generally speaking and where possible, the goal is a controlled touchdown at the minimum safe speed, with the wings level, landing gear retracted and a minimal sink rate. Healthy conjecture will always arise among pilots as to the best means to achieve this. Thankfully, it will remain a theoretical discussion for the great majority.

To achieve the lowest speed over the water, a landing into wind would normally be the prime choice. However, the swell also needs to be considered as landing head-on to a rolling wave will exclude the chance of a smooth touchdown. Hence, landing parallel to the swell is advisable.

The selection of flap is also often debated. While the ditching procedure in certain manuals calls for the use of full flap to minimise the speed and afford better visibility at touchdown, these checklists are also predicated on having thrust available to control the rate of descent. (And enough time to carry out the checklist. ) Often a mid flap setting is suggested to offer a compromise between reduced speed, sink rate and wing configuration on first contact with the water, particularly if the approach is without power.

The flare, holdoff and touchdown is critical. Judging the flare over water is void of the normal cues associated with landing and can prove difficult, particularly over calm, glassy water. Similarly, not too many pilots have to routinely judge the landing flare with their wheels retracted and the associated changes in height and ground effect. Keeping the undercarriage retracted is designed to prevent the wheels ‘digging in’ on touchdown and pitching the aircraft violently into the water.

Maintaining a wings level attitude will also guard against one wing striking the surface first and slewing the aircraft around in an uncontrolled manner. This was graphically illustrated in the case of the widely circulated footage of the Ethiopian Airlines 767 off the Comoros Islands in 1996.

Approaching touchdown, at around 500ft, the flightcrew will warn the cabin to brace for impact. Dependent on the aircraft type, the ideal nose attitude is typically in the order of 10-12 degrees as the water looms close and contact with the surface is imminent.

A smooth, single touchdown on the aft fuselage is the goal, though often not the reality. ‘Skipping’ along the surface will expose the aircraft to a series of impacts, but in reality, touching down in a relatively ‘clean’ configuration means a high chance of more than one contact.

In the end, on the day there will be compromises and judgement calls based on the remaining aircraft systems, time available and prevailing conditions. If it all comes together successfully, there will be somevery grateful passengers and the possibility of a slot on the talk show circuit.

Being Prepared

As with all emergencies, sound training before the event is vital. In the case of ditching, the training provided varies widely between operators, with the degree of overwater operations often being a determining factor. While ditching training may be a core component of emergency training for offshore helicopter operators, the same may not be true for those flying Ayers Rock scenic flights.

It will always be impossible to train for absolutely every contingency in every emergency situation. While budgets and time constraints may play a part, the varying scenarios of each emergency offer much too broad a spectrum to cover. As such, all emergency training is designed around regulatory requirements, training budgets and probability.

Airline training departments and aviation authorities design their syllabi against risk management principles to ensure that a wide range of non-normal situations are covered. In turn, beyond the initial training, a recurrent program will provide ongoing training for the entire career of both flight and cabin crew.

The focus of training is linked to likelihood, and by all accounts for multi-engine jet transport operations ditching falls into the ‘remote’ category. This is not purely a function of aircraft and their engines’ everimproving reliability, but the regulations for over water operations are stringent and seek to ensure that the aircraft can at all times divert to an alternative airfield in the event of a critical systems failure (catastrophic events like that which evidently befell Air France flight 447 notwithstanding).

Even so, it is a case of double jeopardy to lose ALL available engines and be forced to land on the water. The Hudson River case also proves that the aircraft doesn’t need to be over the middle of the Pacific Ocean to end up floating – indeed, for the crew of flight 1549, ditching was far preferable to landing on densely populated land.

To this end, ditching training at airlines falls into a category of its own. The process of ditching is discussed at length in the manuals, and crew training in emergency equipment, liferafts, evacuations and subsequent survival is ‘hands on’. Crews are scrutinised on these skills annually by both theoretical and practical examination. A failure to meet the CASA set standards results in the crew member receiving further training before being allowed to return to line flying.

Yet in this stringent training environment, the training of pilots to fly the actual ditching manoeuvre in the simulator is not mandated by the FAA or CASA, due in part to the difficulty in accurately modelling aircraft behaviour in a ditching.

Nonetheless individual operators do include it in their syllabus of training, and some flightcrews take it upon themselves to rehearse for the eventuality during simulator training sessions.

Once, the thought of losing all four engines and their associated systems on a Boeing 747 was previously thought to be virtually impossible. Then in 1982, British Airways flight 9 encountered volcanic ash over Indonesia with the subsequent loss of thrust on all engines. Again, the crew performed admirably in a situation beyond the scope of their training and manuals to ‘adapt, improvise and overcome’. Subsequently, the books were rewritten, simulator training was updated and checklists modified.

Today, pilot education of volcanic ash and its effects is routine.

This may well prove the case with ditching as well. Simulator exercises frequently ‘reverse engineer’ the data from such incidents and use the lessons learnt to train pilots. With the data generated from US Airways flight 1549, it is quite possible that a change in the training requirements in this area will be forthcoming.

Getting Out

So many factors came in to play in the case of the Hudson River ditching, not the least of these being an experienced and well trained crew on both sides of the flightdeck door. The two pilots had over 35,000 hours experience between them, while the three flight attendants had a total cumulative service in excess of 80 years! For a successful outcome, the entire crew had to perform their designated roles to the best of their ability and, seemingly in this instance, at a level above. This was critical, not just in executing a successful ditching, but in safely evacuating 150 passengers.

Evacuations are generally described as prepared or unprepared, depending on whether the crew has had enough time to ready the cabin, its contents and passengers for the evacuation. It is also an opportunity to call for the donning of life jackets. The flight attendants would have had some advanced warning on flight 1549, but it would have been minimal. Fortunately, as the aircraft had just lifted off, the catering carts were likely still secured away.

On coming to rest, the cabin crew is now faced with assessing the available exits, launching the rafts or slide rafts, and evacuating the passengers with a minimum of time and panic. It is a fine balance to maintain order in the cabin while they undertake their duties, and voicing loud, concise commands is central to organising the potential chaos. These are the very scenarios and drills that cabin crew train for year after year throughout their career.

A water landing presents the additional challenge of available exits. Notwithstanding fire, damage and extreme aircraft attitudes, in a land evacuation most exits are generally available. This is not necessarily the case when the aircraft is afloat. The attitude with which an aircraft settles on the water may preclude the use of certain exits, particularly the rear doors if the aircraft sits tail low and the door sill lies below the water line.

To further aid in keeping the hull watertight, the A320 also has a ‘ditching’ pushbutton on the overhead panel. When activated, the guarded switch automatically closes valves and inlet doors which lie below the waterline.

The A320 is certified so that all doors and overwing exits can be used in a ditchnoting and accordingly are equipped with escape slides. Despite this certification, it is a primary task of the crew that the viability of the exit is assessed before opening the door, as a door below the waterline will allow the water to come flooding in and further impede the stricken aircraft struggling for buoyancy. Preventing over-zealous passengers from cracking these doors open in haste is another critical duty for the crew.

Opening the door will result in differing scenarios depending on aircraft type.

For some aircraft, the escape slides double as liferafts, while others call for the crew to manually launch rafts that are stowed elsewhere in the cabin. Similarly, distress beacons can be integral to the rafts, or launched independently. The evacuation is only started at an exit when these rafts are inflated and ready to accept passengers. It is also imperative that the lifejackets are only inflated when clear of the aircraft. Another tragedy associated with the Ethiopian Airlines 767 ditching was the death of passengers within the aircraft having survived the impact. With their jackets already inflated, they floated to the aircraft ceiling and were unable to escape via an exit.

With doors open and the slides or rafts inflated, the passengers are shepherded towards the exits in a speedy manner to clear the aircraft before it can submerge. The crew will check the cabin again to ensure that all of the passengers have evacuated before being the last to exit.

Once clear, survival and rescue become the next priorities. Again, the crew have been trained for contingencies varying from desert survival and dehydration to arctic hypothermia. The crew of flight 1549 fortunately ditched close to land with a readily available flotilla to ferry the passengers to safety. Facing any significant time in the sub-zero waters may well have resulted in a different outcome.

It is said that cabin crew are there to provide the passengers with life saving assistance in an emergency, and that when the emergencies are not taking place, they are available to provide cabin service. This is not only a truism, but a very healthy mindset for all those involved with air transport.

The crew of flight 1549 and their wealth of experience emphasised the critical role to be played by those in the cabin in case of an emergency.

In the Wake

Being confronted with a multiple engine failure is one of the greatest fears of any flightcrew. To be further confronted with ditching the aircraft with only minutes to react is the stuff of worst case scenarios.

Yet events such as US Airways 1549 and the British Airways 747 left powerless by volcanic ash have proven that ‘worst case’ can on occasions become reality. For flight 1549, the investigators will seek out the facts, volumes will be written and procedures modified – as proactive as aviation safety endeavours to be, sometimes lessons have to be learnt from experience. Undoubtedly this will be the case again in the wake of the Hudson River ditching.

Fortunately, landing a jet transport aircraft on water is a rare event. Despite the mass of variables that can confront a crew and the time constraints that may be imposed by fate, the crew’s training, experience and measured, appropriate responses can make the seemingly impossible survivable. It is a credit to the entire US Airways crew that all of the passengers went home to their families.

Safety briefing cards in the seat pockets and preflight presentations are provided with the hope that the actions described primary duty It is said that cabin crew are there to provide the passengers with life saving assistance in an emergency, and that when the emergencies are not taking place they are available to provide cabin service. (Paul Sadler) are never required. In the same way flight and cabin crew train for most conceivable eventualities year after year, crossing their fingers that simulations are as close as they get. Yet time and again when the unthinkable has occurred, training has kicked in and the crew prove that they are up to the task.

The ability for a crew to ably fulfil their roles when confronted with an emergency is a function of both thorough training and the correct mindset under pressure. The landing of US Airways flight 1549 on the Hudson River is testimony to this. These are invisible intangibles to the passengers as they board yet another routine flight, yet are possibly the most valuable component of the ticket price.

Should the unthinkable occur and their aircraft is faced with ditching, it will be the crew’s training, preparation and mindset that dictates whether they sink or swim.