BBC News
December 17, 2021
This is the time of the year when Lahore Airport, one of the busiest airports in Pakistan, has become almost impossible to operate due to heavy fog. Thus, the flights of many foreign airlines, including Pakistan Airlines, have to change routes.
Between Wednesday and Thursday this week, only PIA had to divert 17 flights from Lahore. Each such diversion costs the airline millions of rupees.
However, is it not possible to land the plane on the runway in heavy fog? According to aviation experts, this is not the case. The plane can land safely in heavy fog. For this, there should be a system at the airport called Instrument Landing System (ILS).
The ILS works with the aircraft's autopilot system to make the aircraft land safely during fog. However, it requires a Category III ILS system. This system is available at Lahore Airport.
So why don't flights land here during fog? Why do airlines have to bear the financial loss and passengers have to bear the hardship of travel?
A PIA official, speaking on condition of anonymity, told the BBC that the reason was that the system did exist but was not working because of the oversight of Pakistan's airports and aviation system. The Civil Aviation Authority (CAA), the agency responsible for this, did not "calibrate" it.
CAA spokesman Saif Khan told the BBC that the CAA had begun work on calibrating the ILS. The work has been completed at Islamabad Airport while the rest of the airports will be completed within a week.
The reason for the recent delay in the calibration of the ILS, he said, was that the calibration planes were damaged due to untimely maintenance work, which took time to repair because the factories were shutting down due to the code. ۔ '
How does this ILS system make an aircraft land in fog when the pilot cannot see the runway? And what is calibration and why is it necessary?
How does a ship land in fog?
Under normal circumstances, the pilot of an aircraft usually takes control of the aircraft by shutting down the automatic 'auto-pilot' system before landing and makes the landing manually. This requires the pilot to have a clear view of the runway.
But when it is foggy, the pilot cannot see the runway. In this case, the aircraft's autopilot system has to be used. The ILS system installed along the runway automatically lands the aircraft while working in conjunction with the aircraft's autopilot system.
With the help of a good ILS system the aircraft can land even when the visibility is only 75 meters or less.
What three things must be in such a landing?
There are three things you must do to land a ship in fog. First of all, the aircraft must have an auto-pilot system. A good ILS system is required at the second airport and the pilot of the third aircraft must be trained for such landings.
Even if one of these components is missing, landing a plane during fog is not without risk, and no airline can take that risk.
The aircraft's auto-pilot and ILS handle the fog landing, however, it is important for the pilot to be constantly monitored throughout the process so that if there is a possibility of a technical error at any point. He immediately took control of the plane.
A CAA official, speaking on condition of anonymity, told the BBC that the pilot had a key role to play because "such a landing is decided long in advance and preparations are made for it. This requires a trained pilot. "
Do you have the necessary equipment at Lahore Airport?
Category III LS system is available at Lahore Airport. Therefore, if the landing aircraft has a modern autopilot system and the pilot is trained, then the aircraft can easily land in Lahore during fog.
However, in order to secure this system, it is necessary to calibrate the ILS system every six to eight months, ie to ensure that the radio signal it sends towards the ship reaches the correct level. have been.
A Civil Aviation Authority official told the BBC that the state-of-the-art ILS Category 3 system was provided to Pakistan by Qatar Airways and installed by the CAA.
So the question is why flights are not able to land at Lahore Airport in these foggy days? Could delay in calibration be the reason?
Why can't planes land at Lahore airport in fog?
According to a CAA official, the state-of-the-art ILS system at Lahore Airport is installed along the main runway. The main runway has been closed to all types of flights for the past year or so due to maintenance work.
Meanwhile, another relatively small runway at the airport is being used. "The ILS system installed on this runway is Category One and has not been calibrated for some time now. That is why the plane cannot land on it in fog."
It is to be noted that out of the three major international airports of Pakistan namely Lahore, Karachi and Islamabad, Lahore Airport is prone to fog every year. According to a PIA official, the airlines have been suffering losses for the last several years.
Why can't ILS be calibrated?
According to a Civil Aviation Authority official, the issue arose when the international civil aviation audit body, IQ, asked the CAA for the documents required for calibration.
At that time it was found out that calibration has to be done every six to eight months whereas in our country it was not done for three years.
According to a CAA official, the agency then decided to withdraw from the ILS until new calibration took place.
According to a CAA spokesman, If the weather improves, the calibration work at the airports (ILS) will be completed within a week."
Is there no alternative?
According to CAA spokesman Saif Khan, there is more than one system at the country's airports that assists in landing aircraft. They can be used in the absence of ILS.
They have two systems called VOR and DME. There is also the RNP approach.
However, a CAA official told the BBC that both VOR and DME systems were outdated. "Most airlines no longer use them. But the RNP approach is used for landing.
He said that RNP approach also has categories. For landing in fog, it is important that the lights installed on the runway required for the RNP approach are of very good quality so that they can produce better signals.
"Our main runway has the same good quality lights but that runway is closed. The quality of the lights installed on the alternative runway is not good.
He said the CAA should ensure timely calibration of the replacement ILS system so that until the main runway is restored, it will be easier for aircraft to land.
