Flying during the monsoon in Nepal?

Domestic air passengers in Nepal faced massive delays and cancellations during April and May because of poor visibility due to wildfire smoke, but things have improved with pre-monsoon showers clearing the air.

However, monsoon flying comes with its own challenges – especially in remote areas airfields serviced by short take-off and landing planes. The trunk routes are less susceptible to delays due to clouds, but spells of heavy rain can also limit airport operations and in some cases have even submerged air fields in the past.

Flights between Kathmandu and Pokhara’s new and old airports were cancelled for more than a week earlier this month because of thick smoke from forest fires in central Nepal. Visibility fell to below 1,000m, when the new airport needs a runway visibility range of at least 3.5km.

At Buddha Air’s Flight Operations Control in Kathmandu, Upendra Lal Shrestha is busy looking at the weather map for Nepal, and seeing if there are any critical visibility issues or cloud buildup. 

“Before every flight, we at the Operation Control Centre provide flight crew with a detailed overview of enroute and destination weather. The main reason for flight delays and diversions are due to weather factors,” Shrestha explains. 

When the visibility is good, domestic flights into Kathmandu usually enter the Valley through mountain passes to the east or west. However, when the visibility goes to below 3km due to smog or heavy rain, pilots have to make instrument landing from the south following strict descent profiles.  

What this means in Kathmandu is that delays are inevitable as planes have to maintain at least a 1,000ft vertical and 3 nautical mile horizontal separation. This means planes, no matter if they are Airbus 330s or Twin Otters, can land only every 7 minutes.

Planes then have to circle, sometimes for hours, while waiting for their turn. If they run low on fuel, they divert to alternative airports. So far this month, more than 80% of all daytime flights were landing on standard instrument approach, which led to long delays for passengers. 

The Civil Aviation Authority of Nepal (CAAN) is trying to more strictly implement flying only under Visual Flight Rules (VFR) in flights to and from airfields in the mountains without navigational aids. This simply means pilots are not allowed to fly into clouds in remote areas.

Since Kathmandu and most major airfields in the Tarai or Pokhara have navigational aids, planes can fly under Instrument Flight Rules (IFR) in poor visibility. 

“No doubt, flying in Nepal is the most challenging in the world because of terrain and weather, but our pilots are trained in simulators for IFR arrivals or departures and they strictly follow rules and follow procedures,” explains Manoj KC, an instructor captain with Buddha Air. 

Interestingly, pilots regard the pre-monsoon season as being more challenging to fly in because of afternoon cloud buildup, updrafts causing turbulence and wind shear. In the monsoon, the weather is more stable and less windy although visibility can sometimes be poor on runway thresholds. 

“The pre-monsoon period, where the weather is windy and stormy can significantly impact flights which can get bumpy,” says Upendra Lal Shrestha. “We have to monitor the weather radat to fly around weather, and sometimes have to reroute.”

Even the slightest delay of one flight leads to a chain effect to the delay of the next flight. The schedule of one flight disruption leads to the disruption of all schedules with a domino effect. 

At the same time, airports in Nepal, including runway and airport lounge facilities, were designed decades ago when air traffic was significantly lower. With the exponential increase in flight frequency, these ageing facilities struggle to accommodate the increasing demand, resulting in more and more delays. 

Despite having a fleet of 17 ATR-72 and -42 aircraft, Buddha Air acknowledges that flight delays can also occur due to technical issues. The carrier provides various channels for travellers to stay informed about flight status. These include a call centre, SMS service, and a mobile app with real-time updates on flight delays and revised departure times. The best way to prepare for delays is to keep plans flexible and keep a buffer for important business.

The pre-monsoon months of May till mid-June have towering cumulus clouds fed by updrafts from the hot plains rising up the mountains. These are chracterised by strong up and downdrafts and turbulence. However, during the monsoon months of July-August-September clouds and heavy rain can reduce runway visibility as well as make them slippery or water-logged. 

Buddha Air has a special briefing for all pilots before the start of the rainy season to remind them of safety measures and forecasts. Climate change is also making weather events more extreme, as was seen this week on a Singapore Airlines 777 flying from London Heathrow to Singapore which encountered severe turbulence while near Burma. 

Buddha Air’s Flight Dispatch Centre at Kathmandu airport also monitors weather at and between airports around the country at all times, and provides pilots with go or no-go information. 

“We have a Japanese software that helps us live track our planes, but also brief us on weather conditions,” explains Buddha Air’s flight dispatcher Umesh Khadka.