02 Sep Going beyond minimum compliance to keep table top runways safe
The Air India Express accident at Kozhikode, India (IATA: CCJ /ICAO: VOCL) on 7 August 2020 is still being investigated and speculation without access to the full facts is something that To70 leaves to the media and certain, often poorly informed parts of the internet. However the fact remains that we do know the following:
- the aeroplane landed in heavy rain;
- the runway is located on a raised area that gives a drop of about 10 metres above the surrounding land when landing on runway 10, and
- the aeroplane landed with a tailwind.
The reason for the choice of the tailwind landing is an important part of the investigation that is ongoing. However, with or without the rain and the tailwind, the runway’s design makes runway excursions more serious events than at other runway designs.
The issue that may be addressed independently of the accident investigation relates to the so-called table-top runway design, a popular design in India. Without a formal definition of what a table-top runway is we consider that India has seven such runways; runways that are raised above the surrounding land beyond one or both runway ends. There may be other airports that are similar in profile with lesser slopes. Additionally, a steep slope at the end of the runway is not unique to India. The ravine at the end of runway 24L at Toronto’s Pearson Airport in Canada (IATA: YYZ / ICAO: CYYZ) is of note. The overrun accident there in 2005 to an Air France Airbus A340 was also a landing made in heavy rain. That runway was not ICAO compliant regarding Runway End Safety Areas (RESA). The airport at Kozhikode is – it must be stressed – ICAO Annex 14 compliant. The RESA is the recommended longer distance of 240 metres and not the minimum prescribed 90 metres long.
Other table-top runway accidents are noted at two airports, both in India: the airport at Mangalore (IATA: IXE / ICAO: VOML) also experienced a fatal accident following a runway overrun (Air India Express flight 812, 22 May 2010) and a number of non-fatal overruns since 2012. The earlier fatal accident killed 158 people. Lengpui (IATA: AJL / ICAO: VELP) experienced a non-fatal overrun accident in 2011 (NE Shuttle Service flight, 4 May 2011).
An airport might be ICAO compliant and still not have adequately addressed the risks associated with its use. The Annexes to the Chicago Convention are minimum standards and States and airports may choose to implement stricter measures. The combination of a table top runway in a region that experiences very heavy seasonal rainfall may justify additional measures.
One engineering solution may be the installation of an arrester bed. Properly known as an engineered materials arrestor system (EMAS), this material, placed in the RESA would prevent runway overruns from leaving the table top and descending down the side of the slope. A estimate made by Rob van Eekeren at Safe Runway GmbH (a company that works with To70 on occasion) calculated that EMAS systems have saved 1.9 billion US dollars after only 11 events. This sort of cost benefit analysis is an essential part of any business case.
A longer than recommended RESA may also be a solution as is the reduction of the slope from the runway’s end to the surrounding land. The runway top surface (slope and grooving) contributes to runway overrun risk reduction as well. Operational measures may also be part of the strategy; a robust rubber removal policy, for example.
Whilst we wait to see the outcome of the accident investigation into the Air India Express accident, airports with similar characteristics can already start considering whether their design and operational policies are sufficient to address the risks posed by table-top runways.
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 Calicut International Airport, CCJ / VOCL; Kannur International Airport, CNN / VOKN; Kullu–Manali Airport, KUU / VIBR; Lengpui Airport, AJL / VELP; Mangalore International Airport, IXE / VOML; Pakyong Airport, PYG / VEPY, and Shimla Airport, SLV / VISM
 Annex 14 Volume I, Chapter 1, Introductory Note para 3
Image source: ANI