Air passengers at mercy of winter delays

Last week, Nepal’s digital media highlighted the news that a Buddha Air flight from Kathmandu to Nepalganj ended up landing in Dhangadi.

Many readers did a double-take because they were misled by a sensational title which suggested that somehow the crew had got the destination wrong. Not that such mistakes have not happened in the past, but this was a simple diversion due to poor visibility at Nepalganj.

Many Nepali media outlets lack aviation literacy, mistaking aircraft models, getting technical details wrong, or using incorrect aviation terminology, for example calling a normal ‘go around’ procedure an ‘overshoot’ which is actually a runway excursion by an aircraft.

The Kathmandu-Nepalganj flight U4451 was operated by one of Buddha’s ATR-72s and was approaching Nepalganj after a 40 minute flight from Kathmandu when the runway visibility dropped to below minima. The flight crew then decided to land at the alternate airport, Dhangadi which had better visibility and was only 20 minutes away.

A Shree Airlines CRJ700 from Kathmandu to Nepalganj also diverted to Dhangadi for the same reason. Both aircraft returned and landed in Nepalganj after the visibility improved there after a few hours.

As winter sets in, flights are sometimes cancelled due to poor visibility, but more common are delays due weather conditions. This also leads to traffic congestion at Kathmandu airport, as domestic and international flights have to make instrument approaches, thus leading to mounting delays in arrivals and departures throughout the day.

Read also: Onset of winter leads to flight delays, Nepali Times

In winter, visibility below minimum at airports is caused by temperature inversion that traps polluted air at ground level. Inversion is especially pronounced in the mornings in Kathmandu, Pokhara and Tarai airports. In fact, at the peak of winter, the entire Indo-Gangetic plains including the Tarai is blanketed by thick fog that does not lift for days.

“Passengers are understandably inconvenienced for having to wait for hours at the airport because of the congestion caused by bad weather, but the airlines have to stick to safety protocols and it is beyond their control,” explains Buddha Air’s Dipendra Karna.

It is when Kathmandu has to operate under instrument flying rules (IFR) when visibility falls below 2km that the delays have a domino effect throughout the day. Incoming flights have to hold for an hour or more, and this means outbound flights are also delayed.

Under IFR procedures, incoming flights to Kathmandu can only land from the south on the airport’s only runway, and since the taxiway does not extend till the threshold of the 02 end of the runway, incoming planes have to be spaced up to 7 minutes apart.

International flights sometimes have to divert to alternate airports like Delhi or Kolkata because Bhairawa and Pokhara airports is not yet open for diversions.

Read also: Domestic aviation flies into headwind, Nepali Times

Biratnagar, Bhairawa and Nepalganj also face cancellations and delays in winter because of the north Indian fog mixed with smog. Sometimes flights from Kathmandu to Nepalganj will not be able to fly even if it is clear at the destination because visibility at the alternate airport is below minima.

“Biratnagar may be open, but if Janakpur or Rajbiraj are closed due to visibility, the flight cannot take off from Kathmandu,” says Karna. Domestic flights on trunk routes now have a better chance of flying on time if it is a night flight. 

Weather-related delays are unavoidable because safety comes first, but operations could be improved with better navigational aids like Instrument Landing System (ILS) or RNAV satellite-based approach guidance.