Explained: How bird strikes take planes down

The Delhi-bound Spicejet aircraft from Patna had to make an emergency landing after a bird struck the engine and damaged three blades. Bird strikes, unfortunately, pose a real threat to passenger planes. Let's look at the statistics around birds that strike aircraft.

A 2006 study on bird collisions conducted by the University of Nebraska showed that most strikes happen at an altitude lower than 500 feet. Almost 70 per cent of collisions happened during the initial stages of take-off or the final phase of landing and affected mostly the frontal aircraft regions like wings, jet engines and windshields.

Collisions keep increasing

The number of bird collisions with aircraft has substantially increased. According to UK Civil Aviation Authority data on bird strikes, 1,835 confirmed hits were reported in 2016. In India, this number was 839, a DGCA report showed. Both these numbers were the highest in the five years from 2012 to 2016.

Also Read: Delhi-bound SpiceJet flight catches fire after take-off from Patna; all 185 occupants safe

DRDO data has been gathered on bird strikes (for IAF from 2010-2018) and has been categorised as per the locations where the hits occurred. The strikes in the sanitised zone, where dedicated personnel are deployed to observe, report and scare away birds (runway area and approach path) were observed to be 25.46 per cent and hits outside the sanitised zone were found to be 13.97 per cent. The most strikes were revealed to be in unknown locations with 60.55 per cent.

Most collisions take place during daylight when bird movement is particularly strong.

Why do collisions occur?

An International Civil Aviation Organization-backed 2014 study lists several reasons for bird strikes. Habitat features like open grass areas, water, etc. and the presence of shrubs and trees can act as bird attractants. Many airports have considerable grass areas within their perimeters. Landfills and waste disposal sites near airports can increase the influx of birds. Airport locations can also influence increased bird movement. Airports in coastal regions have much more uncontrolled bird activity than inland airports.

Also Read: DGCA audits 30 flying training organisations, finds multiple safety violations

What happens in a bird strike?

Certain bird strikes pose a serious threat to aircraft. Flight deck windshields are made of three layers of glass-faced acrylic. Between them, there is a thin urethane layer and each panel has an anti-fog and anti-ice system. While small birds are not a serious problem, the outer layers can suffer cracks if a heavy bird hits the aircraft. The presence of multiple layers ensures that the aircraft remains pressurised during bird collisions. The pilots are also trained to turn on window heating before take-off, which makes windows softer and less fragile.

Plane engines, however, are vulnerable to disruption in the movement of the rotatory blades when a bird hits the turbine and gets caught in the engine. This can damage blades and cause a partial or total engine failure. The good news is that plane engines are generally robust and can withstand some bird strikes. In case one engine is lost, the thrust from the remaining engines can be increased to limit the problem. Most aircraft can continue to fly even if one engine ceases to function.

As of today, there is no solution to the problem of bird strikes. More research and analysis are required to come up with practical and cost-effective ways to tackle the challenge.