Dangers at airports

Dr. Ruwantissa ABEYRATNE

BUSINESS: Not many industries face the same challenges with regard to combining social responsibility and business as the airport industry.

One of the challenges faced by airports is to cope with adverse weather conditions and ensure that the airport industry remains a safe place to work in. The success of an airport depends on a delicate balance between safety and punctuality and always remains a critical operational challenge for airports.

There are two major types of danger at airports: adverse weather and runway incursions. There is a popular misconception that risks to crew, passengers and staff cease to exist once the aircraft engines are turned off. This is simply not so.

One commentator has remarked that it is a common feature at airports that injury and death is caused to ground handling staff during thunderstorms. Adverse weather also portends a serious threat to activities such as refuelling, de-icing and baggage handling operations.

There is an increasing burden cast on meteorological information providers to give accurate weather information to airports and many airports re known to have established policy that requires the shut-down of ground handling operations when lightening strikes within three miles of the airport.

Other hazards that might seriously affect those working on the air side are windstorms which have sometimes lifted baggage containers off the ground and ice and snow which pose a serious threat of injury to passengers climbing aircraft steps who could slip on accumulated black ice.

Catastrophic events such as tsunamis tropical cyclones, snow storms, floods and dust and sand storms are real threats to airports, requiring vigilance and responsibility of both the State concerned and the airport authorities.

Early warning systems and emergency and contingency response plans have to be in place, which have to be implemented with precise communications.

Aerodrome emergency planning is addressed in detail in Chapter 9 of Annex 14 to the Convention on International Civil Aviation, signed at Chicago on December 7, 1944 which provides that every aerodrome must have established an aerodrome emergency plan commensurate with aircraft operations and other activities conducted at an aerodrome.

One of the most critical functions of airports is de-icing of aircraft, since if aircraft have ice on their wings they must be de-iced and protected with anti-icing fluids. An insignificantly small accumulation of ice on the upper structure of the wing could considerably reduce the lift of that surface and all ice must be removed before take off.

Airports providing ground handling services have to constantly monitor the de-icing process as the fluids applied to de-ice an aircraft are only effective in holding off re-icing for a limited time, after which ice could accumulate again, requiring de-icing.

The period between de-icing and re-icing is called the holdover time and would be critical, particularly in the case of a departing aircraft delayed on takeoff.

There are also attendant problems for aircraft stemming from extreme cold temperatures. These could include fuel and hydraulic leaks; difficulty starting the Auxiliary Power Unit(APU); difficulty starting the engines; landing gear tire "cold set"; and difficulty in opening doors.

To counter these problems, State regulation and accurate weather forecasts which are now provided in many States through computer aided forecasting systems.

These modern weather observation systems help the air navigation service provider to improve the quality of weather data and partly replace the human observer in the weather forecasting process.

Most aviation accidents occur at airports or in their immediate vicinities. However, unlike en-route accidents, those involving airport control occur at slow speeds posing less of a risk to passengers and crew.

The survival rate in an accident at an airport or in its vicinity could therefore depend on the airport emergency services provided. Adverse weather is one of the most ominous threats in this regard, and some airports have now equipped crash trucks with forward looking infra red systems (FLIR) and global positioning systems (GPS) to counter low visibility caused by fog and ice.

Wind shear is yet another deadly weather phenomenon that could affect aircraft on take off or landing. Wind shear is a difference in wind speed and or direction between two points in the atmosphere.

Depoending whetehr the two points are at different altitudes or at geographically different locations, shear can be either vertical or horizontal.

Wind shear can affect aircraft airspeed during take off and landing in disastrous ways. Strong low-level outflow from thunderstorms causes rapid changes in the wind character just above ground level.

Initially, this outflow causes a headwind which causes the plane's acceleration, and causes a pilot to reduce engine power if they are unaware of the wind shear.

As the plane passes into the region of the downdraft, the localized headwind disappears, suddenly dropping the plane's airspeed, perhaps too much if the pilot has reduced engine power.

Then, when the plane passes through the other side of the downdraft, the previous headwind becomes a tailwind. These sudden switches from headwind to downdraft to tailwind can cause a plane to crash if these switches occur too close to the ground. A pilot can correct for this wind change by increasing engine power, if there is enough time to react.

The second type of danger at many airports is runway incursion. A runway incursion is defined by the International Civil Aviation Organization(ICAO) as any occurrence involving the incorrect presence of an aircraft, vehicle or person on the protected area of a surface designated for the landing and take off of aircraft.

ICAO considers that information pertaining to the proximity of aircraft and/or the vehicle; geometry of the encounter; evasive or corrective action; available reaction time; environmental conditions, weather, visibility and surface condition; and factors that affect system performance are all necessary to properly classify the severity of a runway incursion.

The official definition of the Federal Aviation Administration of the United States is that a runway incursion is "any occurrence at an airport involving an aircraft, vehicle, person or object on the ground that creates a collision hazard or results in a loss of separation with an aircraft taking off, intending to take off, or intending to land".

The FAA definition envisions various types of occurrences such as a pilot deviation - which is any action on the part of the pilot that results in violation of a Federal Aviation Regulation - an operational error, which is an occurrence attributable to an element of the air traffic control (ATC) system which has two results, the first being two or more aircraft coming within less than the minimum separation minima or between an aircraft and obstacles (vehicles, personnel and equipment on runways) and the second being an aircraft landing or departing on a runway closed to aircraft after receiving air traffic authorization - and a vehicle or pedestrian deviation - an occurrence resulting from a vehicle operator, non-pilot operator of an aircraft or pedestrian deviating onto the movement area including the runway without ATC authorization.

There are five key players involved in a runway incursion: the State; the pilot; the controller; the airport operator; and employers of the pilot and the controller.

In the employer category are the airline (in the case of the pilot) and the service provider (in the case of the controller). The airport operator comes within the realm of liability particularly if signage, markings and lights on the runway or taxiway are not provided in accordance with set standards.

In some instances runway incursions have resulted in serious accidents with significant loss of life. They are increasing in number as traffic volume increases at airports.

Statistics indicate that runway incursions of a serious nature that lead to accidents occur at complex, high volume airports which have characteristically parallel and intersecting runways with multiple taxiway intersections which necessitate aircraft crossing active runways.

As far back as 2000 runway incursions posed the most serious threat to air travel in the United States where they increased by 75 per cent from 1993 to 2000.

The world's worst airline disaster occurred on a runway when in 1977,582 persons were killed as a KLM Boeing 747 which was taking off slammed into a PAN AM 747 in the Canary Islands.

There have been numerous incidents and accidents relating to runway incursions both before and after that fateful event.

One of the more recent was the Comair accident which sent flight 5191 onto a wrong runway sending 49 people to their deaths. A similar incident occurred in 1993 where a pilot who was cleared for take off on a particular runway, accidentally chose a shorter one.

In March 2006, the Federal Aviation Administration investigated three close calls at Chicago's O'Hare Airport. The first involved a Lufthansa jet and Delta Airlines plane that came within 100 feet of each other after both were cleared for take off from intersecting runways.

The second incursion involved a United Airlines plane two days after the Lufthansa - Delta incident, which was instructed to take off from a runway already assigned to another carrier.

The third incursion took place in mid March 2006 when a regional jet was cleared for take off on a runway moments before an Airbus A320 was cleared for take off on a runway that would have connected to the one to be used by the regional jet.

Another incident, which occurred on Febraury 1 involved USAir Flight 1493 operated with a Boeing 737-300 commercial jet en route from Syracuse Hancock International Airport, New York to Los Angeles International Airprot, California via Columbus International Airprot, Ohio.

Immediately after landing on runway 24L, it collided with Sky West Flight 5569, a twin-engine turbo-prop Fairchild Metro III plane en route to Palmdale, California.

The pilot of the USAir plane was cleared to land on runway 24L. Six minutes later, Skywest 5569 was directed to move onto runway 24L for take off and hold in position.

The SkyWest flight was at taxiway 45, some distance down the runway from the threshold, since it did not need the entire length of the runway for takeoff. Three minutes later the 737 touched down, then ran into the SkyWest Metro, which was still holding in position.

The two planes slid down the runway, then off to the side, coming to rest against an unoccupied firehouse, and burst into flame. All 12 people on the Metro were killed (10 passengers and 2 pilots), and 22 of the 99 aboard the 737 perished (20 passengers, 1 pilot and 1 flight attendant).

Such instances are too numerous to mention and have prompted the United States FAA to issue an Order in November 2005 banning air traffic controllers from working alone. On December 28, 2006 the FAA updated guidance to the controller workforce on taxi into position and hold (TIPH), effective February 5, 2007.

While most of the TIPH changes will be transparent to pilots, two changes of note are: ATC may withhold the landing clearance when another aircraft is holding on the runway, and there will be increased traffic advisories for TIPH operations on intersecting runways.

According to the FAA Advisory, ATC will issue traffic advisories to aircraft holding in position and to aircraft holding, arriving or departing the intersecting runway.

The FAA Flight Plan 2006-2010, is developing a range of initiatives from airport design concepts to surface movement procedures. Related efforts address the errors committed by pilots, air traffic controllers, and airport-authorized vehicle operators and pedestrians. The Administration has set performance targets and is holding itself accountable for meeting those targets.

In this regard, the FAA has been testing equipment that is capable of both detecting potential airport surface incursions and collisions and at the same time warning pilots of impending risks and danger.

The Norris Airport Runway Incursion Prevention System (ARIPS) detects moving aircraft and other vehicles by using ultraviolet rays emitted from runway and taxi lights which have been modified for the purpose, along with detectors installed that provide "trip wires" at key runway intersections and thresholds.

The challenges ahead are vast. With the advent of new large aircraft (NLA) such as the Airbus A380, awareness of runway safety becomes an even more compelling factor.

The largeness of the A 380 aircraft, and indeed others of its kind, poses some questions to the aviation industry, particularly to the air transport and airport sectors.

Apron space restrictions may require dedicated parking areas for such large aircraft, thus imposing a strain on aerodrome space. On a basic comparison of the A380 and B747-400 aircraft, one sees that there are differences between the two aircraft.

For instance the A380 has a maximum takeoff weight of 560 tonnes while that of the B 747 is 395 tonnes - a difference of 41.7 per cent. The maximum landing weight of the two aircraft are 386 tonnes and 286 tonnes which has a difference of 35 per cent.

The wingspan of the A380 is 79.8 meters while that of the B747 is 64.4 meters. The length of the two aircraft are 73 meters and 70.7 meters respectively.

The latter two statistics, i.e. length and breath of the two aircraft are critical comparisons in terms of parking, loading and unloading passengers and cargo.

New large aircraft may be limited to operating along specific taxiway routes, which may need to be identified by additional information signs to facilitate air traffic control instructions to the pilot.

Furthermore, additional signs may be required along service roads that run adjacent to or across the designated taxiing route of a new large aircraft in order to alert drivers or vehicles to the potential exposure to jet blast.

In the instance of two NLA or NLA and other aircraft operations in an aerodrome, there will be a need for air traffic control procedures to control and guide such air traffic movement. These procedures may require signs to indicate positions for aircraft to hold.

Additional information and mandatory instruction markings may be required to identify taxi routes into which NLAs are permitted. These signs would also be required to mark speed restriction areas, prohibited movement areas and specific NLA holding positions and they will need to be easily distinguishable to obviate confusion between NLA and other aircraft.

Also, where taxiways have been widened to allow for NLA operations, additional stop bar lights and intermediate holding position lights may be required at runway-holding and intermediate holding positions. This may also apply to runway guard lights.

What is most required now is guidance, firstly for States and secondly for airlines and air navigation service providers. In this regard, ICAO has developed a manual for preventing runway incursions. This is a step in the right direction.