Runway Overrun on Landing
Runway Overrun on Landing
Definition
Overrun. An event when an aircraft passes beyond the end of the runway during an aborted takeoff or landing operation. The overrun distance is described by the longitudinal distance traveled beyond the departure end of the runway.
Source: ACRP Report 3: Analysis of Aircraft Overruns and Undershoots for Runway Safety Areas
Description
A runway overrun on landing is type of runway excursion that happens when a landing aircraft is unable to stop and departs the end of a runway. This occurrs when the (current) landing distance required exceeds the (current) landing distance available. The former is a function of the aircraft position relative to the runway and the latter depends on a number of factors (some of them dynamic) such as aircraft speed, use of retardation methods (brakes, spoilers, reverse thrust), runway surface conditions, etc.
Effects
The outcome of a runway overrun on landing depends mostly on the speed at the time of the overrun and the surface after the end of the runway. Depending on the circumstances, the event can result in:
- Casualties or injuries. These are more likely in the extreme scenarios (e.g. collision with a structure, steep slope or a body of water after the runway end, etc.).
- Aircraft damage. This can range from none or minor (e.g. deflated tyre) to a hull loss.
- Aerodrome damage. This includes damage to elements of the lighting system, antennas (e.g. ILS localizer), perimeter fence, etc.
- Impact on aerodrome operations. Depending on the damage to the aircraft and the aerodrome it is possible that a runway is rendered out of service for a prolonged period of time.
Causal Factors
The following is a (non-exclusive) list of causal factors for runway overrun on landing events:
- Unstable approach. This (often combined with other factors) is arguably the most commonly cited causes for an overrun.
- Late touchdown. This reduces the landing distance available.
- Touching down with speed being too high. This can be caused by a variety of reasons (unstable approach, tailwind, system malfunction, etc.) and in general increases the landing distance required.
- Ineffective use of retardation methods increases the required distance for decelleration.
- Erroneous calculation of required landing distance could cause the pilots to not make optimal use of the retardation methods available.
- Landing on a wrong (shorter) runway. If this remains undetected, the pilots could have a false impression that they have longer landing distance available than they actually do.
- Aircraft system malfunction, e.g. hydraulic system, brakes, flight control surfaces (flaps, slats, spoilers, etc.) often results in higher than normal speeds or reduced decelleration capacity.
- Over-consideration for comfort. This sometimes leads to prolonged flare, reducing the landing distance available.
Contributory Factors
The following factors, while not normally being the leading cause, could aggravate the situation depending on the circumstances:
- Tailwind increases the touchdown speed and results in longer landing distance required.
- Runway surface contaminated by water, snow, slush, ice, etc. reduces braking effectivenes and results in longer runway distance required.
- Runway slope.
- Increased pilot workload. Landing is one of the busiest phases for the flight crew. Any (unexpected) increase of the workload could distract them and contribute to a runway excursion.
- Reduced situational awareness. Oftentimes a landing can be safely completed even though one or more of the causal factors listed above are present. For example, touching down at high speed due to tailwind could be compensated by more aggressive use of retardation methods. However, if the situation is not properly recognized, the necessary remedial action would probably not be performed.
- Pressures (either real or perceived) could influence flight crew's decision making into continuing the approach and landing.
Defences
The following measures could either reduce the risk or mitigate the consequences of a runway overrun on landing:
- Flying a stabilised approach and performing a go-around if necessary greatly reduces the likelihood of a situation that can develop into an overrun.
- Using an onboard system such as ROPS could enhance the pilot's situational awareness so that they could react promptly and adequately to a change of the situation.
- Installing an EMAS, while not being able to prevent it, could mitigate the consequences of an overrun.
- In case EMAS is not installed, correct maintenance of the RESA would similarly mitigate the effects of an overrun. A soft surface would have reduced bearing capacity which, in turn, would increase drag and improve decelleration. It should be nothed however, that if the ground is too soft, this could result in landing gear damage.
- Making the aerodrome lights frangible is a standard defined in ICAO Annex 14 and reduces the damage to aircraft.
Accidents and Incidents
On 25 November 2022, a Boeing 737-800 landing at Kitchener/Waterloo Airport, Ontario, with the left thrust reverser inoperative overran the runway before stopping approximately 500 feet beyond the runway end. The captain had unintentionally selected the takeoff/go-around switch instead of disconnecting the autothrottles and then removed his hand from the left thrust lever to select reverse thrust on the right engine. The captain was experienced but new to type, and the first officer was a recently employed inexperienced pilot who had just completed his type rating. The left thrust reverser had been intermittently defective for the previous six months.
On 5 December 2022, a Boeing 737-800 overran the end of the runway at Dortmund despite making a normal wet runway touchdown after a stabilised Cat 2 ILS approach with low visibility procedures in force. The unexpected continuation onto the clearway was followed by a stop within it. The most recent runway condition measurements gave good braking action on the entire length of the runway. However, after the overrun, it was found that new precipitation had covered the middle section of the runway with wet snow. The report concluded that this had been the cause of the overrun.
On 23 October 2022, an Airbus 330-300 failed to complete three night approaches to runway 22 at Mactan-Cebu due respectively to adverse weather, a low height ‘SINK RATE’ warning and a system fault. Touchdown followed the fourth approach but the aircraft failed to stop on the 3,300 metre-long runway and sustained major damage before coming to a stop 235 metres beyond the runway end. All occupants successfully evacuated without serious injuries. The lack of braking was found to have been caused by damage during brief aircraft ground contact just before the beginning of the runway during the second approach.
On 12 March 2022, an ATR76-600 captain made an unstabilised approach to Jabalpur, India, leading to a first bounce more than halfway along the runway and a final touchdown 400 metres from the runway end. The first officer took control but did not commence a go-around, and the aircraft overran the runway before stopping. The captain had just over four months command experience and had made six similar "high-severity long-flare" approaches in the previous five days. These had gone undetected because although such exceedances were supposedly being tracked by company flight data monitoring, this event was not being tracked.
On 27 January 2020, an MD83 made an unstabilised tailwind non-precision approach to Mahshahr with a consistently excessive rate of descent and corresponding EGPWS Warnings followed by a very late nose-gear-first touchdown. It then overran the runway end, continued through the airport perimeter fence and crossed over a ditch before coming to a stop partly blocking a busy main road. The aircraft sustained substantial damage and was subsequently declared a hull loss but all occupants completed an emergency evacuation uninjured. The accident was attributed to the actions of the Captain which included not following multiple standard operating procedures.
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