Aircraft landing using Instrument Landing System (ILS)
As a pilot, I’m often asked, “How do pilots plan flight routes?” My answer is always “Meticulously.” There are numerous factors to consider when planning a flight route, and all safety requirements must be met in order for a route to be approved. And rest assured, regulations are nothing less than stringent when it comes to the safety of flights over vast stretches of land or water.
Let’s take for example an Airbus A330 flight from Kuala Lumpur, Malaysia, to Melbourne, Australia. The total travel distance is approximately 3,500 nautical miles (or about 6,500km), with a flight time of around eight hours, depending on wind conditions at the time of travel.
A plane must always carry sufficient fuel for the flight, and in this context, ‘sufficient’ means enough fuel for a safe flight, bearing in mind that extra fuel, on the other hand, adds to the cost of the journey. So typically, a plane flying from Kuala Lumpur to Melbourne would load up to about 55,000kg of fuel. For the sake of convenience, pilots generally refer to measurements of fuel in kilogrammes, instead of in litres or gallons, as they need to ensure that the plane does not exceed the maximum takeoff weight limit of 235,000kg, and that it is able to burn off any extra fuel to enable it to land safely at the maximum landing weight of 187,000kg.
Regulations require that the pilot not only carry the trip fuel from Kuala Lumpur to Melbourne, but an additional buffer as well for safety considerations, such as a diversion to an alternate airport in Adelaide, as well as an extra half an hour’s worth of holding fuel there. On top of that, if the flight’s arrival at Melbourne coincides with a busy period at the airport, an additional 15 or 20 minutes’ worth of fuel must be carried in case there is a holding period there as well. The captain also needs to review the weather forecast for the destination, and if not satisfactory, the captain must then nominate a second alternate airport like Sydney, in addition to Adelaide. In this scenario, the plane must carry enough fuel to divert to the farthest alternate airport planned for the flight route.
In every flight plan, numerous airports are planned along the route to cater for any unforeseen medical, technical or weather diversions. If the flight is on a southeasterly direction to Melbourne for instance, Singapore, Jakarta and Bali in Indonesia, and Darwin, Alice Springs, as well as Sydney or Adelaide in Australia, might be included in the route for any potential diversion.
When considering alternate locations for diversions, the captain must ensure that the selected airport is ‘adequate’, which in aviation terms means that the airfield must meet designated safety criteria, such as the necessity for the runway to be long enough for landing. Appropriate fueling facilities, emergency services and technical maintenance services are also necessary safety considerations. And it is crucial that the alternate airport must also have proper navigational aids for the plane to land.
It is noteworthy that these considerations only make up the lowest benchmark by which the captain fulfills the ‘adequate’ standard. The airport must also be technically ‘suitable’, which means that visibility must be good enough for the plane to land.
There are still more considerations that apply when flying over vast stretches of land or water. One such consideration is ETOPS (Extended Twin Engines Operations), which has recently been extended to planes with more than two engines. In a nutshell, ETOPS is an operation whereby aircraft are allowed to fly an extended range over places where airports are limited, such as over the ocean, when previously, they may have been restricted; essentially, ETOPS is an exemption from the rules that may have restricted the flying range of an aircraft in the past.
Since 1936, pilots were required to ascertain that there were suitable landing fields at a minimum of every 100 miles along their flight route. As the aviation industry grew, this requirement was adjusted, whereby aircraft were allowed a 60-minute diversion period, meaning the pilot had to ensure that for every 60 minutes over the course of a route, there was an appropriate possible landing site. This basically applied to two engine planes, and not three or four engine aircraft.
Today, aircraft that have more than two engines like the three-engine (MD11) and four-engine (A380) jets, necessitate a new equivalent to ETOPS – the EDTO (Extended Diversion Time Operation).
The first ETOPS approval was granted to the now defunct TWA in 1985, the same year that the Federal Aviation Administration (FAA) in the US also began allowing twin engine aircraft an extension from a 60-minute diversion period to a 120-minute diversion period. In 1988, this was then further extended to a maximum 180-minute diversion period, which is still operative today.
Regulations require that the pilot not only carry the trip fuel, but an additional buffer as well for safety considerations
Pilots love good navigational landing aids, especially the Instrument Landing System (ILS), which enables aircraft to land if the pilot is unable to establish good visual contact with the runway on a normal day without automation. Currently, the airport with the most advanced version of ILS, which enables planes to land automatically with very low visibility, is only in Melbourne, Australia.
The ILS can provide the Airbus A330, for instance, with precise automatic horizontal and vertical guidance during landing and can indicate the real-time distance to the runway. Due to its complexity, the centre line alignment sensor of the ILS in the plane is highly sensitive to any kind of obstruction such as buildings or vehicles in the surrounding area that can cause unwanted needle deflections. As such, when a plane is carrying out an automatic landing, no aircraft or vehicle should be present (mobile or otherwise) nearby.
So, the next time you are enjoying your meal in the air, travelling at many hundreds of miles an hour to your destination, you can be sure that your captain has already painstakingly planned your journey far ahead of time, taking into account unforeseen possibilities, as well as potential emergency stops along the way. If only drivers put in as much effort on road trips, there would be far fewer instances of vehicle breakdowns and people being stranded on their journey, as they would be well-prepared with extra fuel on a route that would necessarily have service stations, motor garages, suitable hotel accommodations and Starbucks along the way!
If you like what you read, more stories are found in my book LIFE IN THE SKIES (Preview here) and you can purchase a copy here. To check for any latest updates or postings, you can follow my Twitter at @CaptKHLim or Facebook here