MC Explains | Are bird hits to planes dangerous and what is DGCA doing about it?

As per India's aviation regulator Directorate General of Civil Aviation (DGCA) data, there was an increase of 27.25 percent in bird hits in 2021 — from 1,152 incidents in 2020 to 1,466 in 2021.

Ironically, one of the reasons for the increase in bird hits was that airports last year were quieter than usual due to limited flights in the wake of Covid-19 restrictions on both domestic and international air traffic.

Quiet airports attract more birds as well as animals — there was a 93.33 percent rise in animal strikes last year as against 2020.

Why are bird hits an issue?

A survey by the International Civil Aviation Organization (ICAO) of data from 91 countries found that airlines face an average of 34 bird strikes in a day.

Another survey by National Business Aviation Association (NBAA) showed that 97.5 percent of wildlife strikes involve birds. In contrast, strikes involving terrestrial mammals account for 2.1 percent, followed by bats and reptiles at 0.3 percent and 0.1 percent, respectively. Collisions between birds and aircraft can occur at any point, from take-off to landing, resulting in damage to aircraft windshields, engines and fuselages.

The majority of airplane scares involving birds do not result in substantial damage to the aircraft or danger to the passengers. Yet more than 200 people have been killed worldwide as a result of wildlife strikes since 1988. The most dangerous form of bird strike is one in which a bird is ingested into the aircraft’s engine; this event is referred to as jet engine ingestion.

According to ICAO, damage to aircraft by bird hits amounts to more than $1 billion annually. However, almost 92 percent of the air strikes are without any damage.

Most modern engines are required to be capable of ingesting birds that weigh about 1.8 kilograms while running at full power. They are required to do it within the initial climb speed without catching fire or making the engine impossible to shut down.

They are also required to operate at minimum 50 percent power for up to 14 minutes after the strike. This means that even if both the engines are hit by large birds, they can provide a combined thrust output of at least one engine, which is more than enough to return to the airport.

Smaller planes would generally be more susceptible to the dangers of bird strikes than larger ones.

How can airplanes avoid bird hits?

After the recent incidents of bird hits in India, the DGCA on August 13 issued guidelines to airports across the country to check incidents of collision of planes with birds and other animals.

The DGCA has asked airport operators to follow a set of instructions aimed at mitigating bird strikes and other wildlife encounters with aircraft. These include drawing up and implementing a habitat management programme to reduce the number of hazardous wildlife, performing risk assessment procedures and recording bird activity around airports.

The DGCA guidelines also include carrying out routine patrols in random patterns and informing pilots whenever there is any wildlife activity.

Internationally, airports use three main ways to minimise the attractiveness of the airport environment to birds, including modifying the habitat of birds, controlling bird behaviour and adapting flight times and paths.

Modifying the habitat of birds

Several methods can be used to modify birds’ behaviour to keep them away from airports, including removing food sources such as seed-bearing plants and insects from the airport property.

Methods such as covering ponds with netting can prevent birds from landing near airports. Destroying bushes and trees that offer attractive nesting sites can also reduce bird visits to airports.

Airports also use sonic cannons, recorded predator calls and other noise generators to disrupt birds. Lasers are also used at dawn and dusk to simulate predators and scare birds away.

In some countries, falcons are trained to disrupt birds over roosting areas before they nest. Dogs are also trained to track bird movements across airports to scare away birds.

Controlling bird behaviour

Some airports use pyrotechnics daily to drive birds away, says Michael Begier, national coordinator of the airport wildlife hazards programme at the US Department of Agriculture.

"The flash, bang kind of stuff immediately gets their attention and pushes them away." Bangers and screamers make a loud explosion, others make a whistling sound, while some emit sparks - different birds respond to different things and some even take flight at the mere sight of the wildlife vehicle.

A banger shot from a pistol cartridge can travel 30-40 yards before exploding, while a 12-gauge shotgun can reach 70-100 yards.

Another way to avoid bird strikes was provided by a study from Purdue University; officials found that planes painted in dark colours attract more birds. Hence, brighter shades should be used to help birds avoid aircraft.

Adapting flight times and paths

Learning to work with birds by modifying flight paths and schedules can help minimise bird strikes. While these methods may not be feasible at all airports, they can be used to help the airport work in harmony with the wildlife surrounding it. Adjusting flight times to avoid the busiest hours for bird activity, such as early morning and late evening or during peak migration periods is also a suggestion.

According to the US Federal Aviation Administration's wildlife strike database, about 63 percent of bird strikes happen during the day, 8 percent during dawn and dusk, and 29 percent at night.

The landing phase of flight is when 61 percent of bird strikes occur, and the take-off run and climb phases are when 36 percent of strikes occur, with the remaining 3 percent occurring when the aircraft is en route.

Another suggestion to prevent such incidents is that engines should be covered with a grill. But this isn’t as easy as it sounds. The main issue is that to effectively block the bird at 800km/h, the grid has to be significantly sturdy and thick, but this will disrupt the air flowing into the engine.

Training spotters with binoculars and scopes to pinpoint hazardous birds and directing planes to different runways or approaches is also adopted by some airports.