Beyond the piano keys…

Airports and airlines alike devote considerable resources into developing contingency plans that enable an effective response to an aircraft accident or incident. These plans differ considerably and vary to cope with the degree of seriousness of the event. However, both are designed to focus on the human welfare aspects of any event and also to cope with the intense media focus that arise as a result of any sizable event, even if there have been no injuries or loss of human life. Fortunately accidents involving loss of life are not common events, but there are non-fatal incidents that are still occurring in excess of one a week.

There were 68 non-fatal incidents recorded throughout 2007. Regardless of the type of event, when they happen the various emergency response plans are activated without hesitation. It is clearly understood that no one can change what has occurred, but how the situation is handled does affect the outcome. Whilst both the airline and airport operator are dealing with the real time events of the incident, the airport operator has the added problem of having its business and that of its customer airlines either suspended or seriously disrupted.

Once the affected passengers needs have been dealt with and they are away from the aircraft and the site of the incident has been stabilised by the emergency services, the aircraft accident investigators are clear to proceed. The time they need to understand the cause varies, dependant on the nature of the event, but only they can authorise the removal of the aircraft from its current position. When this clearance is given, the airport operator is now confronted with what is referred to as a disabled aircraft.

A disabled aircraft is an aircraft that can no longer move under its own power, or that of a normal tow truck. It might be that only one set of landing gear has sunk in soft ground, or it might be a complete excursion from the runway or taxiway. The aircraft may also be seriously damaged, in addition to other structural failures that may have occurred as a result of the incident. In the worst case scenario, it may not fly again. However, given its location within the airport, it will probably be obstructing a runway or taxiway which in turn could be causing considerable operational disruption to that airport and its users.

The responsibility of recovering a disabled aircraft is normally considered to be that of the aircraft operator, although there are many operators that do not have any capability to handle such a task. Limitations such as lack of equipment and experienced personnel within the engineering and maintenance departments might be the factor for a large number of operators, but then there are possibly as many operators who do not have an engineering and maintenance department at all. Therefore, the task of an aircraft recovery could be outsourced to a third party, as are so many other functions within aviation.

ICAO Annex 14 recommends that an airport operator has a plan for the removal of a disabled aircraft. Therefore, it is important that it is understood who will take charge of the situation, should it arise and be responsible for removing the stricken aircraft. It may be that the airport is the home and main base of an operator and they have all the resources to deal with such a task. For others there might be an agreement in place for another operator within the region to handle this need on their behalf. There are also some airport operators that have invested in having their own aircraft recovery capability and so will take care of their own needs and not be reliant on others. Irrespective of where the recovery team and their equipments are coming from, one thing that can be guaranteed is that the moment the accident investigators give clearance to remove the aircraft, the expectation is that the aircraft will be removed immediately. The reality is that it normally takes longer than estimated and sometimes it can actually take days.

One factor for this is that aircraft recovery is not an exact science and things can and often do go wrong or do not work as planned. Unlike the normal maintenance and servicing tasks of an aircraft, which are tried and tested from start to finish, aircraft recovery has so many variables. If, for maintenance purposes, there was a requirement to raise an aircraft clear of wheels, then this would normally be done in the sterile environment of a maintenance hangar, using purpose designed jacks on a stressed and level concrete floor. Now put the same aircraft 50 metres off the end of a runway, on a 15 degree nose down slope, on soft ground, in inclement weather. The raising and levelling of the aircraft will then be achieved by using pneumatic airbags. This now becomes a completely different challenge.

In addition to this, for any aircraft recovery, one of the highest priorities of the recovery team will be not to damage the aircraft any further than it has been as a result of the incident. It could be that the aircraft will be beyond repair and classified as a ‘hull loss’, but it is only the insurance surveyors who can make that statement. Until that statement is made from a recovery aspect, the aircraft is considered as repairable and will be treated as such. Even if the aircraft is declared to be beyond repair, it can still have a considerable value in terms of the salvage of sub-assemblies and components. Therefore damage incurred during the recovery process, referred to as Secondary Damage, will be avoided at all cost.

The insurance surveyors or loss adjustor representing the interest of the operator and the underwriters obviously have a vested interest in the actual incident and the recovery process. With new generation aircraft price tags exceeding USD 300 million depending on the aircraft type, there can be a large sum of money at stake. There are just three companies globally who provide this service and there are benefits from having close relationships with their representatives who are on site. They can authorise the financial aspects of an action plan, which will expedite the recovery process.

The reparability of the aircraft will be based upon the extent of the damage incurred versus the age and value of the aircraft. If repair is not a viable option, then the aircraft will be decommissioned and there will be a lot less to consider when recovering the aircraft. If the aircraft is to be returned to an airworthy condition, then the situation is far more complex.

For the post event inspection criteria to determine the return to service repairs, the analysis has to incorporate what the aircraft has been subjected to during the recovery process. Therefore all loads and forces exerted onto the airframe or any of the aircrafts major components must be known. If these are not known and therefore not evaluated, then stresses could be induced that could cause structural failure at a later date.

To provide the recovery team with the required technical data in terms of knowing the allowable load limits, the major aircraft manufacturers produce an Aircraft Recovery Manual (ARM). These are very comprehensive documents which outline the maximum load and forces that can be applied when lifting or pulling the aircraft. It provides data on centre of gravity calculations, moment arms for both longitudinal and lateral axis and allowable skin pressures, as well as any other data deemed necessary to cope with that particular aircraft.

It is from these documents that the data is extracted and applied to the situation that the recovery team are confronted with. If it is possible, some of this work will be accomplished before the aircraft is cleared for recovery by the accident investigators to optimise every minute available. In addition to the load calculations, it is at this time that recovery will be planned and the techniques to be employed will be decided and thus what equipment will be required to achieve this. Before any attempt to move the aircraft is made, there are two factors that must first be evaluated; the condition of the ground that the aircraft has come to rest on if there has been an excursion and the weight of the aircraft.

It may well be that groundwork will be needed to stop the aircraft from sinking any further and to provide stability. In addition to this, there would probably be a requirement to lay either temporary roadway, or something more permanent to return the aircraft back to the taxiway or runway. This is not uncommon and whilst the laying of temporary roadway which many recovery teams have as part of their recovery equipment is fairly straightforward, anything else would require assistance from the airport operator.

Whilst evaluating any groundwork required, it is important to assess the impact to the environment. This is becoming far more high profile in certain regions of the world and any waterways such as rivers, streams or surface water drainage systems, must be protected from leaking fluids. Precautions need to be taken to protect wildlife and consideration given for the removal of all soil contaminated by liquid or solid hazardous materials, such as aviation fuel, hydraulic fluid or carbon fibre fragments.

As for the weight of the aircraft, it would almost be a certainty that the load would need to be reduced before any lifting or pulling took place. It is standard practice to off-load any freight, catering and fuel onboard to achieve the Operating Empty Weight (OEW) of that aircraft. The fuel loads on certain aircraft, being so large, will take a considerable time to off-load, but the storage of this fuel is the bigger problem. Very few fuel companies have sufficient capacity to store the fuel load of today’s wide bodied aircraft if they have rejected take-off.

The growth of new aircraft, in size and payload, has naturally caused concern for airport operators in the event of any mishap. With the ICAO classification of New Large Aircraft (NLA) indentified as Code F, Circular 305 was issued in preparation and the concerns regarding one of these aircrafts becoming disabled were redirected to the IATA Aircraft Recovery Working Group for guidance material.

The Aircraft Recovery Working Group was formed in 1970, when a group of like minded individuals met to discuss similar concerns as the ones we face today regarding disabled aircrafts. It was at the same time as aviation entered into the wide-bodied era, with the introduction of the Boeing 747. This group later operated, as it continues to do so today, under the organisation of IATA and structurally little has changed, except it is now referred to as a task force as opposed to a working group.

The task force members consist mainly of representatives from aircraft manufacturers, airlines, recovery equipment manufacturers, airline recovery teams, airport operators and insurers and specialised groups involved with aircraft recovery. The diversity of the group makes it unique, as it brings together a wealth of experience and knowledge on a subject that very few people actually get exposure to.

Collectively, some excellent results have been achieved by the task force for the benefit of the aviation community. The response to ICAO Circular 305 was in the form of a complete re-write of the airport services manual Pt 5, to address the issues of today’s new aircraft and is now available through ICAO. The task force has been actively involved in all aspects of aircraft recovery and has numerous action items in work. Over the past three years, the focus of the group has been on NLA, particularly the A380. Working closely with Airbus, the data was made available to allow all recovery scenarios to be studied, to explore practical techniques and develop tooling solutions.

The task force also provides a good forum to analyse any recent events and understand the lessons learned from what worked and perhaps what did not. The professionalism of the membership allows open and transparent discussions to take place and our relationships extend beyond that of business acquaintances. When confronted with a disabled aircraft we will call upon all the means available to expedite the recovery.

The support offered by all of the organisations concerned, particularly the major aircraft manufacturers, such as Airbus and Boeing, is to be commended. On-site assistance is available regardless by such organisations, but for task force members when that option is accepted, we are working with fellow colleagues and friends.