While cases of ‘ramp rash’ featuring GSE colliding with aircraft on the apron are by no means unheard of, there are other – rarer but perhaps even more serious – examples of accidents at airports that see aircraft leave or overshoot a runway during landing or take-off. National regulatory agencies and industry bodies work hard to minimise the occurrences of these extreme incidents
The International Air Transport Association (IATA), the industry body that supports the aviation industry through the maintenance of global standards for airlines, describes a ‘runway safety event’ as one that take places on take-off, during a rejected take-off, on approach, during a go-around or on landing.
It believes that runway safety has become a significant area of interest for the industry due to the frequency of accidents in the runway environment; these include runway excursions, runway collisions, undershoots/overshoots, tail strikes and hard landings.
The most numerous of the accidents of these various types are runway and taxiway excursions, according to IATA data. Such excursions – of which IATA recorded an average of 18 per year worldwide that involved commercial air transport aircraft over the 2010-14 period – can lead to loss of life or injury to people either on board the aircraft or on the ground. They can also result in damage to aircraft, airfield or off-airfield equipment and buildings.
IATA is playing its role in dealing with the issue through the implementation of a data-driven approach to the evaluation of aviation safety risks and the development of potential solutions. Despite IATA’s and other efforts from regulatory and industry bodies, the runway excursion rate has shown only slight improvement in recent years.
Between January 2010 and December 2014, IATA recorded a total of 415 accidents worldwide. Of these accidents, 90 were classified as runway/taxiway excursions, the sort of incident that frequently requires specialised aircraft recovery equipment and specialists. Typically, a runway excursion takes place in two forms:
Veer-off: A runway excursion in which an aircraft leaves the side of a runway
Overrun: A runway excursion in which an aircraft leaves the end of a runway
Technically, the term excludes both accidents in which an aircraft did not initially land on a runway surface, and take-off excursions that did not start on a runway (for example, in cases of inadvertent take-offs from taxiways).
Runway excursions and all the other runway safety events that are seen at airports around the world can always be attributed to one or more causes, and it is by addressing these various issues that agencies and regulatory bodies strive to improve performance and achieve as near to perfect safety records as are possible. Just some of the contributory factors in veer-offs and overruns, the most common accidents, are:
Deficiencies in areas such as safety management, regulatory oversight, flight operations, maintenance, training, standard operating procedures (SOPs) and pre-flight or in-flight checks
Environmental factors such as wind shear, other bad weather factors or a contaminated runway surface
Aircraft factors such as malfunctions, poor brakes, malfunctions in engine performance or flight controls
Undesired aircraft states such as crabbed landings, directional or speed deviations or loss of control when on the ground
Errors relating to factors such as on-board communication, failure to go around or poor flight control
The role of national regulatory agencies
National aviation regulatory bodies have their part to play in minimising incidents of runway excursion and veer-off. Furthermore, most airports have well-developed, and well-rehearsed, procedures in place to deal with runway excursions, involving rescue and fire fighting services (RFFS), ground handlers and airport and airline staff. In the UK, for example, these procedures are contained in airline and airport safety management systems (SMS), which are approved by the Civil Aviation Authority (CAA).
In the UK, any airline involved in a runway excursion would be expected to file an official Mandatory Occurrence Report with the CAA. This places an obligation on the airline to investigate how the incident happened and to file a follow-up report with the UK’s civil aviation regulator and overseer within three months. Any such incident may also be subject to an investigation by the Air Accidents Investigation Branch, a CAA spokesperson confirms.
In the US, the National Transportation Safety Board (NTSB) – an independent Federal agency charged by Congress with investigating every civil aviation accident in the US (as well as significant accidents in other modes of transportation) – recorded just three events between 2012 and 2016 as runway excursions carried out by commercial aircraft at certificated airports: one at New York La Guardia in 2015, one at Alaska’s Bethel Airport in 2013 and one at Anchorage also in Alaska in 2012.
The US Federal Aviation Administration (FAA) has regulations in place to minimise the frequency of such incidents, as well as guidance on how aircraft can be recovered when they do leave the safety of a runway.
FAA Advisory Circulars are in place to minimise the likelihood of an aircraft leaving the runway in the first place, with the Administration providing:
Strict criteria for the longitudinal profile and the cross-slope grade (crowned about the centreline) of any runway
Set standards for runway grooving (to prevent hydroplaning)
Requirements for rubber removal (where runways can be slick when wet due to accumulated rubber build-up from tyres on the runway)
Standards for runway distance remaining signs (so pilots know when they are approaching the runway end)
The FAA also provides standards pertaining to runway safety areas (RSAs) for grading and clearing objects, and to engineered materials arresting systems (EMAS) to minimise the consequences (in terms of both injuries and aircraft damage) when a runway excursion does occur.
As for the recovery of an aircraft in the US, this must take place in accordance with CFR (Code of Federal Regulations) Part 139. The Airport Certification Manual for Part 139 – Airports has a section that describes the removal of disabled aircraft and this applies to aircraft excursions.
Whether an investigation into a runway excursion takes place depends on the circumstances surrounding that runway excursion. If the FAA issues a letter of investigation (LOI), then it will investigate the runway excursion.
However, confirms an FAA spokesperson: “The FAA is more focused on excursion prevention than consequences after they occur. Expectations associated with the prevention efforts are addressed across multiple lines of business to include the office of airport, air traffic, and flight standards. Plus, an FAA webpage is dedicated to runway excursion prevention, whereby best practices and other guidance information are provided to highlight the FAA’s initiative to addressing excursion.”
Finally, the FAA very recently implemented a new tool described as a Runway Condition Assessment Matrix (RCAM) to be used by airport operators and aircraft operators to standardise how contaminants are identified and reported. With this information, aircraft operators are able to align a particular aircraft braking performance capability with identified contaminants. “The FAA views this as another tool in the toolbox to assist with our excursion prevention efforts,” the spokesperson adds.