The consequences of many runway excursions, especially overruns, are made much more serious because the aircraft end up beyond the confines of the ICAO-defined Runway End Safety Area (RESA): the aircraft may be catastrophically damaged because of major obstructions or terrain changes encountered soon after this protected area has been exceeded. Suddenly down-sloping terrain and low but substantial ground obstructions, which are of no concern to aircraft in flight, may take on considerable significance in determining the damage to an aircraft following a major overrun. The example of the Air France Airbus 340-300 which ended up in a ravine at Toronto in 2005 illustrates this well.
Under ICAO SARPs, the recommended extent of a RESA is considerably greater than the requirement for one. However, worldwide and even in the USA, there are still large numbers of runways used by air carrier aircraft which do not yet have even the ICAO required RESA, or satisfy the more stringent ICAO Recommended Practice, or meet the equivalent (for overrun purposes) FAA ‘Standard’. State AIPs do not always include specific reference to the extent of RESA provision.
The RESA for some runways is surrounded by dangerous features, usually on the runway extended centreline. Raised prior awareness of flight crew to these dangers might influence their subsequent decision to make or complete a landing rather than initiate a go around (including ones commenced as Rejected Landings). Similar considerations might influence a decision to attempt a Rejected Take Off from a speed above V1. There is some circumstantial evidence that flight crew who do not have sufficiently detailed knowledge of significant terrain or obstacle challenges beyond the immediate confines of a runway are more likely to be involved in overruns which lead to major airframe structural damage.
Although Aerodrome Obstacle and Precision Approach Terrain Charts published in the AD section of State AIPs can identify notable terrain changes, this information is not normally transcribed to the documentation available to Flight Crew, unless it refers to terrain awareness which is relevant to safety in flight. In the case of notable non-terrain ground obstructions, these will only be recorded in an AIP - and therefore capable of transcription to flight crew documentation - where they are relevant to safety in flight.
The safety case for an EMAS (Engineered Materials Arresting System) has generally been made as a substitute for a fully-established RESA. Any application of EMAS to reducing the risk of occasional overrun on take off or overrun on landing which extends beyond RESA may be problematic, unless there have been studies to define an appropriate lateral extent, taking into account the tendency to increasing divergence from the runway centreline as distance from the runway end increases.
Some Examples of Sudden Terrain Change beyond defined RESAs
The following are examples of sudden down-sloping terrain change beyond the existing RESA provision at ICAO Annex 14 Code 3/4:
Bristol UK Runway 27
At 60 metres from the end of the runway i.e. at the end of the Runway Strip, the terrain suddenly begins to drop steeply at a gradient of around 14%, continuing at a similar gradient for over 150 feet vertically. This is evident from the AIP Obstacle Chart
Jersey Channel Islands Runway 27
At approximately 100 metres from the stop end of this runway, there is a sudden and continuous drop in terrain of about 200 feet. This is evident from the the AIP Obstacle Chart
London Luton UK Runway 26
The terrain beyond the stop end of this runway initially slopes gently downwards at a gradient of about 3% for about 225 metres; the downward slope then increases to about 5% for a further 115 metres at which point an almost sheer drop of over 50 feet suddenly occurs. This is evident from the the AIP Obstacle Chart and in slightly more detail on the Precision Approach Terrain Chart for Runway 08