On the evening of September 30, an Airbus aircraft landed at Noi Bai Airport (Hanoi) with a dented nose, necessitating a halt in operations for repairs. According to Vietjet Air, the A320 aircraft with registration VN-A650, flying from Buon Ma Thuot to Hanoi, landed at 7:22 PM on September 30 after colliding with a bird. The airline had to suspend operations to repair the damaged nose. So, why can birds cause such significant damage? Let’s explore.
Understanding Why Bird Strikes Can Cause Severe Damage
Bird strikes occur daily around the world, but not all incidents result in accidents. Since 1988, over 200 people have died in animal-related aviation accidents, resulting in more than $600 million in damages each year. In the United States alone, the Air Force reports an average of over 5,000 bird strikes annually.
Image of the Vietjet Air aircraft with a dent caused by a bird strike.
Theoretically, large aircraft can continue to fly after colliding with birds weighing up to 2 kg. However, there are 36 bird species in North America that average more than this weight, and even small birds like starlings can damage powerful aircraft engines. The greater the speed difference between the aircraft and the bird, the more severe the impact on the aircraft. The weight of the bird is a factor, but speed difference plays a more significant role. A flock of birds becomes more dangerous if they collide with the aircraft multiple times.
Dale Oderman, a professor of aerospace engineering at Purdue University (USA), stated that birds pose a significant threat to aircraft, especially during takeoff. “Geese and larger birds are more dangerous than smaller ones. When a bird strikes an aircraft, it can be sucked into the engine, causing the blades to break. A broken blade is then pulled deep into the engine, damaging other components,” he explained. To counter the lurking danger from wildlife, airports implement various measures to minimize the risk of bird strikes. For instance, fewer trees are planted near airports to prevent birds from nesting or resting in them.
Mr. Oderman provided an example and calculated theoretically as follows:
Assuming a pigeon weighing an average of 1 kg faces a Boeing 747 taking off at a speed of approximately 330 km/h or 92 m/s. We assume the aircraft is stationary relative to the pigeon; at this moment, the takeoff speed of the aircraft is the relative speed between the two objects, meaning the pigeon is flying at 92 m/s.
From there, we can calculate the kinetic energy of the bird using the formula:
Kinetic Energy = 0.5 x mass x velocity^2 = 0.5 x 1 x 92^2 = 4232 Joules.
Next, assuming after the collision, the bird dents the aircraft’s nose by 5 cm at the impact point, we can calculate the force exerted by the bird that this area absorbs. Here, the dent in the aircraft’s nose corresponds to the distance traveled by the impact point:
Force absorbed = Kinetic Energy of the bird : Depth of the dented area = 4232 : 0.05 = 84640 Newtons.
This means the aircraft’s nose absorbed a force equivalent to the weight of an object weighing up to 8464 kg.
Next, we calculate the pressure the aircraft’s nose experiences during the impact. Here, we assume the impact area is half of a sphere with a radius of 5 cm (with the center at the impact point). Thus, we can calculate the area of the dented area on the aircraft’s nose:
Impact Area = 0.5 x 4 x 3.14 x 0.05^2 = 0.0157 square meters.
Finally, we calculate the pressure the aircraft’s nose must withstand during the collision. The impact force is the force the aircraft absorbs:
Pressure = Impact Force : Impact Area = 84640 : 0.0157 = 5391082.8 pascals.
Additionally, Mr. Oderman noted that transport aircraft similar to the Boeing 747 are designed to withstand an average pressure of about 7300 pascals, meaning that a pigeon in the above example becomes an extremely dangerous object for aircraft, including the Airbus A320 mentioned at the beginning of this article.
