Therefore, for all aircraft operations, irrespective of aircraft type and the number of engines, it is necessary, for reasons of sound operational practice, that airlines take into account the availability and suitability of emergency alternative airports along the planned route of the aircraft.
ICAO Annex 6 defines an adequate alternative airport as being an airport which there is a sufficient runway length to meet aircraft landing (and take-off) performance requirements, an airport that is available as and when required, and an airport that has the necessary support facilities and services such as air traffic control, lighting, communication, metrological services, navigation aids and rescue and fire fighting services. Published regulations governing the availability of alternative airports (for example, opening hours, military restrictions), the facilities at these locations, fuel management in perhaps extreme weather conditions, and many other issues have to be carefully looked at.
Diversions are generally caused by a number of events, including:
- Medical alerts
- Engine failure
- Cargo-hold smoke warning
- In-flight entertainment system smoke warning
- Avionics smoke warning
- De-pressurisation at cruising level
- Dual hydraulic failure
Although aircraft operations across remote continental regions have been undertaken for many years now, subject to limitations imposed by the availability of ground-based navigation aids and on-board navigation systems, new routes are now possible with the additional availability of GPS and the development of extreme long-range aircraft.
Of particular interest are trans-polar flights linking the eastern seaboard of North America with South East Asia and the Arabian Gulf with the western seaboard of North America (for example, Dubai <> San Francisco, 7041nm). Another extreme example might be a flight between Australia (Perth) and Buenos Aires (6814nm). Flying a great-circle trans-polar route has the advantage of reducing trip distance and flight time thereby reducing direct operating costs and also enabling new routes to be developed that are within the mission capability of current and projected long-range aircraft.
For this reason, the FAA has developed specific requirements regarding en-route diversion (and alternative ETOPS airports) for aircraft on trans-polar operations. FAA guidance for polar operations requires airlines to define a sufficient number of alternative airports, such that one or more could reasonably be expected to be available in varying weather conditions. Air carrier operations for emergency alternatives are covered by FAR 121 and for ETOPS (twin-engine operations), en-route alternatives are covered by FAA AC 120-42A and JAA GAI-20. Polar operations have additional guidance, cited in FAA Order 8400.10 (OPESPEC B055).
The requirements are based on the following capabilities at alternative airports and in line with FAA rules:
- A diverting aircraft can land and take-off safely at the airport given the existing runway length, width and load-bearing capacity.
- The diverted / disabled aircraft can be cleared from the runway so that another aircraft can land with maintenance personnel or depart with the passengers; otherwise, more than one suitable runway at the airport would be required.
- Passengers and crew are able to deplane in a safe manner.
- Facilities at or near the airport can provide passengers and crew with shelter and food while the aircraft can be repaired, or until alternative transportation can be provided.
- It should be possible to extract passengers and crew safely and as soon as possible. Execution and completion of the recovery would be expected within 12 to 48 hours of the diversion.
The basic questions that should be posed when determining the feasibility of an airport as an en-route alternative airport are as follows:
- Does it meet the minimum airport standards as outlined in FAA Advisory Circular (AC) 120/42A and relevant JAR-OPS Directives?
- Can the aircraft safely land given the existing runway length, width, pavement strength, etc.?
- Can the reason for the aircraft being diverted be dealt with, i.e. medical emergency, system failure, fire, etc.?
- Can the aircraft clear, or be cleared from, the runway so that another aircraft can land with maintenance support or to fly the passengers out?
- Can the passengers be provided with basic shelter and food, either while the aircraft is repaired or until alternative transportation is provided?
National civil aviation authorities world-wide have based their regulatory requirements for airport design and operation on ICAO Annex 14 - Standards and Recommended Practices - Aerodromes. From this Annex are derived the planning requirements for minimum runway dimensions, pavement strength, and other equipment such as navigation aids. The airport's physical infrastructure is designed to at least match the largest aircraft that would be expected to normally operate at that airport.
In some cases, operators engaged in Polar flights have been permitted to designate en-route alternative airports that do not comply with the specific equipment and training requirements. It has been suggested by manufacturers that using such airports without appropriate equipment and training may increase the risk element of diversion to a particular airport; this would have to be considered against the risk of a longer diversion time to an approved airport.
Notwithstanding the capabilities of individual airports, the Polar region has a poor operational environment. The climate can be harsh, and during the winter the temperature can be extremely low. One of the coldest airports, if not the coldest, Yatkutsk in Siberia has minimum temperatures approaching minus 60 degrees Celsius. Snow fall and possibility of high winds in some of the regions makes landing of an aircraft more complicated and ice and snow removal equipment is necessary to create acceptable conditions for aircraft operations.
The catchment population around airports in the Polar region is typically small with settlements being scattered around a large area in relatively small communities. Consequently, there are only a few airports large enough to serve as an ideal alternate airport for those airlines operating trans-Polar routes. Greenland is a good example of this. It is the world's largest island, covering 2.2 million square kilometres, yet on such a large island there are only three airports with sufficient runway length to accommodate large jet aircraft. Alaska, Siberia and northern Canada are also sparsely populated albeit with larger communities but scattered over a similar geographic area.
The population of these areas generates mainly short-haul domestic traffic. Airports have relatively few daily movements, and these are undertaken by short to medium range aircraft. These types of operation do not require the same level of facilities and services, as would a busy international airport in the more populated regions of the world. In addition, regional airports serving small communities do not usually have sufficient hotel facilities in the vicinity of the airport. Note that a diverted long-range aircraft such as the B777-200LR or A340-500 would need accommodation for 300 or more passengers and crew.
The infrastructure in the Polar region will vary from one country to another. The population, air traffic, airport design, the level and type of services and facilities, and weather will all vary from location to location.
To illustrate this, consider a notional flight operated along a Great Circle route between the Gulf States and the west coast of North America. At least 30 airports along the route have been identified as potential en-route alternative airports. Of these airports, 10 airports have been identified as having specific Polar environmental characteristics (location, climate). These are Murmansk, Longyearbyen (Svalbard), Banak (Lakselv), Tromso, BodÃ¸, Kangerlussuaq (formerly Sonderstrom AB), Thule AB, Churchill, Yellowknife and Resolute.
Of these, one airport is located in Russia, four in Norway, two in Greenland and three in Canada. Two of these airports are eliminated from further consideration as potential alternative airports. Thule AB is only available for a commercial carrier in an extreme emergency, but does have sufficient infrastructure capability for military services operated by a DC8. Resolute Airport has insufficient runway length (1900 metres) for A340-500 / B777-200LR operations.
The remaining eight airports might then be each assessed for suitability as an alternative diversion airport based on a number of different parameters, as follows:
[a] Compatibility of aircraft performance with published runway lengths: The runway length requirements are linked, but not limited, to aircraft landing weight, altitude, temperature, wind, and runway surface conditions. By the time the Polar region is reached, under the scenario considered, a significant proportion of fuel payload will have been consumed. Modern aircraft are also fitted with fuel-jettison systems. Of the eight airports, the shortest runways are at Longyearbyen and Tromso (2323 and 2392 metres respectively). Under most circumstances this would be sufficient for long-haul aircraft to both land and take-off.
[b] Pavement strength: The airport operator calculates the pavement (runway) strength, expressed as the pavement classification number (PCN). The aircraft manufacturer calculates the bearing pressure of the aircraft undercarriage system (at maximum ramp weight) on the runway surface. This is the aircraft classification number (ACN) and ideally should not exceed the PCN of the airport runway that the aircraft is landing on. In the situation of a single emergency landing, at less than maximum weight, the runway pavement strength for all eight airports would probably be sufficient to bear the weight of a wide-bodied aircraft.
[c] Rescue and fire fighting service: There are specific recommendations in ICAO Annex 14 regarding the provision of rescue and fire fighting service (RFFS) equipment and personnel. For airports with regular wide-bodied operations, RFFS category 9 is required. The eight airports listed above have a RFFS category of between 5 and 7, the exception being Churchill that has no RFFS capability at all. As of 2003, Churchill (as with many other Canadian regional airports) depends on the local volunteer fire department, which usually responds to the airports request.
[d] Airport services and facilities: Small airports tend not to have a range of tow-bars for wide-bodied aircraft. Thus, there are limited handling and servicing facilities for wide-bodied aircraft such as the A340-500 and B777-200LR. This may be an issue that needs to be resolved through ICAO / IATA to enable some mechanism for dealing with diversions of 'unexpected' aircraft types. All eight airports have sufficient capability for ice and snow removal and have Jet A-1 fuel available
[e] Air traffic and meteorological services: Generally available 24 hours a day. Five airports have ILS but otherwise ground based navigation aids are limited to a combination of non-precision NDB / VOR / DME.
[f] Airport opening hours: Not all airports have 24-hour operations. There are ongoing discussions at IACO / IATA level to find a mechanism by which airlines would pay service charges to airports that are nominated as en-route alternatives. This may help some airports to generate sufficient revenues to allow 24-hour operation with full RFFS coverage at an appropriate level.
[g] Passenger accommodation: Hotels for passenger and flight crew accommodation are available off-airport in towns close to each of the airports. However, it seems unlikely that sufficient accommodation would be available to cater for 300 passengers plus crew, especially during the summer when the hotels have few vacancies.
[h] Medical facilities: None of the airports have airport medical treatment facilities but there are local medical centres in nearby towns that have equipment for basic emergency needs. The number of, potentially, available beds in the local hospitals are limited. The hospitals take part in the airport emergency exercises. Medical evacuation by air (subject to runway availability) is possible to larger regional hospitals.
To conclude, an increased use of trans-Polar routes offers the potential for cost savings, reduced technical stops, and new routes utilising current aircraft types. However, there are attendant risks. There are few airports in the Polar region that are capable of providing logistical support in the event of an emergency, for example, RFFS, medical / hospital facilities and hotel accommodation.
Current ETOPs regulations allow twin-engine aircraft to continue their journey providing that anacceptable alternative airport is within the specified maximum flying time (for example, 120 / 180 minutes) after engine failure. However, there may be other emergencies that would require the flight crew to make a decision on the risk of continuing the flight weighed against the risk of landing at an airport that is lacking in the level of logistical support normally expected at international airports.