Low-visibility landing explained
Exclusive report on Dubai Airports’ meticulous low visibility operations — from early preparations to disruption response
It’s 5am on a foggy morning and the Dubai Airport Operations Control Centre (AOCC) is on full alert. Visibility along the DXB runways has dropped to below 600 metres and the cloud base under 300 feet. Fifteen of the 70 AOCC staff are on duty, coordinating the activities of hundreds of others and assessing, among other things, the real-time feed of flight movements, airfield traffic and passenger flow across terminals, down to the exact numbers standing in the immigration or security queues.
The situation is fluid, the forecast gloomy. As Low Visibility Operations (LVO) start, movements of aircraft and vehicles on the airfield are restricted, lighting is provided to the taxiway and distance between arriving and departing airborne aircraft doubled from five to 10 nautical miles (nm). AOCC staff are in constant communication with airlines, including home carriers Emirates and flydubai, to adjust schedules and coordinate movements of flights and passengers.
Protocol escalated
Should visibility drop further, as it drastically did to 50 metres on Christmas Eve last year, the LVO protocol is escalated and full disruption response activities swing into action.
One of the foggiest days in recent history, December 24, 2017 saw significant disruption to flights and passenger journeys, with 105 flights being delayed across T1, T2 and T3. Some outbound passengers were delayed for over 10 hours as departures were grounded and flights diverted to Dubai World Central (DWC), Fujairah and Al Ain.
“Fog in Dubai can be thick, persistent and disruptive,” said Damian Ellacott, vice president AOCC, giving Gulf News an exclusive lowdown on the actual sequence of events that takes place every time fog (or other disruptive weather) sets in. This could well be every other day in the coming months.
According to the National Centre of Meteorology (NCM), the heavy fog season in Dubai, which typically extends from mid-October to March, has already seen 108 fog days this year, compared to 156 last year.
A complex atmospheric phenomenon, fog often reduces visibility to less than 1,000 metres, even below 100 metres sometimes. The airport receives the fog forecast from the Met services a day earlier. “Usually, the fog starts to form between 4am and 5am, which coincides with the start of one of our daily traffic peaks. As our LVO protocols kick in, the AOCC has many activities to coordinate.”
Reduced flow-rate
Preparations for the fog begin when the visibility falls below 4,000 metres and is forecast to deteriorate to below 1,500 metres, and/or the cloud base is below 1,000 feet.
Ellacott said: “Runway capacity is split between departures and arrivals, depending on schedule requirements. For example, if many aircraft are inbound and holding for landing when flow-rates have been reduced due to weather conditions, then arrivals will be prioritised to get aircraft, passengers and crew safely on the ground.”
The flow-rate or number of arrivals and departures ranges from 66 aircraft per hour at peak periods and in good weather, to as low as 20 aircraft per hour during LVO.
Ellacott is quick to add that the allocation of arrival, departure slots during reduced flow-rate is managed dynamically. “Reduction from high to low flow-rate may not be linear and it’s impossible to say over how long a period it will reduce; it depends on many reasons — intensity and persistence of fog, time of day, day of week, holiday or non-holiday, airport restrictions, outside factors and other considerations. As we manage the operation out of disruption, the increase in flow-rate may not be linear or in a fixed format.”
He said: “DWC is the preferred diversion airfield for aircraft inbound to DXB in the event of a dense fog. If aircraft are holding at DXB and cannot land, they are diverted to DWC if it has capacity. If aircraft are inbound from far away and are still outside the UAE, they will be asked to divert farther away — into Muscat, Bahrain or other airports, if the weather is not forecast to improve and/or diversion airfields in the UAE are full.”
Ellacott said aircraft can be told not to get airborne from outstations if the weather forecast is very bad and diversion capacity is unlikely to be available in the UAE. “Priorities are safety and passenger comfort, and to recover from any schedule disruption ASAP.”
He said a fog-related disruption can take up to 24 hours to recover from. “Passengers should understand we take the protection of their journeys through Dubai Airports very seriously and place every effort to minimise the impact during what can be very difficult circumstances.”
Passengers should understand that we take the protection of their journeys through Dubai Airports very seriously and place every effort to minimise the impact during what can be difficult circumstances.”
Damian Ellacott | Vice-president, Airport Operations Control Centre