The present invention relates to an impact-absorbing, load-limiting connection device, especially for connecting components or modules of a rotary-wing aircraft, as well as to a rotary-wing aircraft having such a connection device.
Over the past 30 years, major efforts have been made in automotive as well as aviation technology to improve the crash safety of automobiles and airplanes in order to protect the passengers in case of an accident, a hard emergency landing or a crash. Especially high demands are made of the crash safety of airplanes since, in comparison to automobiles, this type of machine is exposed to far greater loads in case of an accident. Developments in aviation so far have been aimed primarily at designing the undercarriage structures of passenger airplanes and helicopters so as to be more crash-safe. Here, fiber composite techniques are being used more and more often, especially carbon fiber composites with Kevlar composites as surface protection.
Among the various types of aircraft, the rotary-wing aircraft such as, for example, helicopters, are especially at risk in case of a crash due to their design and flight-specific attributes in comparison to conventional fixed-wing airplanes.
Whereas in case of a crash, fixed-wing airplanes generally follow a relatively flat angle of impact relative to the horizontal, the angle of impact of rotary-wing aircraft or helicopters is usually quite steep and can be at a value of 90° (vertical impact). Consequently, the main stress directions or main impact directions are very different with the above-mentioned types of aircraft. Unlike fixed-wing aircraft, rotary-wing aircraft or helicopters, for example, have massive and heavy structural components, such as gears, engine(s) and rotor(s) located at or on the top of the passenger cabin. In a crash, high accelerations and forces are exerted on these upper structural components, which thus greatly endanger the cabin and the passengers seated in the cabin. The high loads generated in case of a crash have to be transmitted and absorbed by the cabin structures such as, for example, the frame, which are subjected to far less of a load during normal operations. For this purpose, massive structural reinforcements are needed which, in turn, lead to unwanted high weights of these structures. Therefore, it would be desirable to be able increase the crash safety while reducing the structural weight.
Moreover, it should be taken into account that, in conventional airplanes, especially rotary-wing aircraft, even in case of a minor crash, quite considerable damage is done to so-called primary structures such as, for example, the cabin, or to other components that are not directly involved in a direct impact or the like. As a result, these components likewise have to be replaced after the crash, which leads to extremely high repair costs or ultimately even to a total loss. Hence, it would be desirable, also in the case of a fairly minor crash, to be able to reduce the severity of the damage or to limit this damage.