Bird strike: how to design bird impact resistant glass

06/07/2022

 

The aerospace industry is full of phenomena and hazards that pilots need to pay close attention to. One of these is bird strike, meaning the impact between an aircraft and a bird, often causing considerable damage both to the aircraft and to the crew.

On 22 November 2021, Leonardo AW169 air ambulance N307TC of STAR Flight (Travis County Emergency Medical Services) suffered a bird strike from a Turkey Vulture  near Austin, Texas.

The flight was not part of an aerospace exercise, but was carrying injured passengers. Both extraordinary and dangerous, the impact was mitigated by the certified strength of the Isoclima glass mounted on the Leonardo AW169.

 

The dynamics of the bird strike involving the Leonardo air ambulance

 

Prior to impact, a member of the medical crew noted the presence of the bird, which maintained its flight path.

To avoid bird strike, the pilot manoeuvred the aircraft to the left so as to prevent the bird from crashing directly into the middle of the front right windshield. This minimised the severity of the impact, which occurred a few seconds later with the vulture hitting an area less dangerous for the crew. Having ascertained the incident, the pilot in command decided to divert from the intended point of landing at Seton Main Hospital, and land at the STAR Flight Hangar Helipad (TE94) as it was just over 1 minute away from the site of the incident with the vulture.

 

The damage reported and the protection offered by Isoclima’s glass

 

The helicopter landed safely with no injuries to the passengers or to the crew.

This happy outcome was guaranteed, not only by the pilot’s prompt actions, but also by the glass that prevented the bird from entering the cockpit.

When inspected on the ground, the damage to the Leonardo AW169 reportedly consisted of:

-                     Cracked front right windshield

-                     Cracked windshield support beam

-                     Cracked greenhouse window

-                     Undetermined main rotor blade surface damage.

To be resistant to bird strike, the windows on the AW169 must be certified on the basis of CS-29 Amendment 2, dated 17 November 2008. This requires the aircraft being designed to assure capability of continued safe flight or safe landing after impact with a 1 kg bird.

Vultures are much larger as they range from 0.8 to 2.41 kg in weight, thus far exceeding the weight required by CS-29.

Our surfaces withstood a violent impact and exceeded the certification requirements.

An important success for us, as it made a real difference in saving people's lives.

Leonardo AW169 Air Ambulance
Leonardo AW169 helicopter