The January 2009 Hudson River miracle, where “Captain Sully” safely landed after his A320 was hit by a flock of birds, revealed to the public the hazard that birds represent for airplanes. Bird strikes in helicopters are less famous as they are not always reported and given so much media coverage. Yet the danger exists and, once more, the solution is to be sought in stringent certification requirements.
If a collision with our feathered colleagues can lead to serious problems for airplanes, then what about the helicopter plastic windshields? And more importantly, what can be done to improve safety?
This issue has concerned me since the beginning of my aviation career, when I read the accident report of a Cessna hit by a small bird thatpenetrated the windshield. Normally the windshield should have resisted the impact of this bird. However, wrong maintenance with unapproved cleaning agents had modified the physical characteristics of the plastic, and the windshield had therefore lost its stability and flexibility.
To understand why birds continue to damage helicopters, we therefore looked at the requirements. Surprisingly enough, there is no requirement at all for small helicopters (Certification Specifications 27), whilst larger helicopters (Certification Specifications 29) must be capable of continuing safe flight and landing following impact with a single 1 kg bird. Not mentioning that some manufacturers try to deviate from these already low requirements to avoid weight penalty and are approved to do so by the authorities.
As these requirements seemed quite low, we directly asked the European Aviation Safety Agency (EASA) for explanations. The first reason given was that “historically, due to the relatively low speed of helicopters, their visibility and noise signature, birds were able to avoid collisions and bird strikes incidents were therefore low and not identified as an immediate safety concern.” This is no longer true. Helicopters fly faster and are less noisy. This, combined with more night operations, makes the probability of helicopter bird strikes higher.
Furthermore, EASA explained that these requirements are based on a study carried out by the Agency in 2008, which concluded that requirements for CS 29 aircraft were sufficient. The most interesting is the recommendation about small rotorcraft: it is recognised that requirements are necessary, but, given the high cost that this modification would mean and that “a change in the regulations may take some time to be effective, the use of helmets and visors might therefore represent a more practical and timely option.”
Fortunately, this “solution” is the not the Agency’s final word, who confirmed that new rules for CS 27 helicopters will be drafted, but the start date has not been set yet. Although the ECA Helicopter Working Group welcomed this initiative, it can only encourage the Agency to launch it as soon as possible and advised that requirements should be based on speed rather than weight given that heavy helicopters do not mean faster ones.
By Thomas Rueder, helicopter pilot at the German HEMS company ADAC.