THE EH101 - AN ALUMINIUM - LITHIUM HELICOPTER

Lithium additions were first made to aluminium in the early 1900's, but the first such commercial alloy, designated X2020 and designed to exhibit high compressive strength and elastic modulus, did not emerge until the late 1950's. Although successfully incorporated into the US Navy's RA-5C Vigilante aircraft at that time, certain technical difficulties prevented the alloy's use on other projects and production subsequently ceased in 1969. However, resulting from significant aviation fuel price increases, together with inroads being made into traditional aluminium markets by organic based composite materials, the mid-to-late 1970's saw revived interest in aluminium-lithium based alloys. Unlike alloy X2020, initial emphasis was upon density reduction due to the presence of lithium, the lightest metallic element, as a major alloying addition, although more recent alloys have been developed in which this addition is made to enhance certain other properties. This paper describes the pioneering use of light weight aluminium - lithium alloys on the new EH101 helicopter and discusses their advantages as well as disadvantages. Related areas such as material specifications are also covered and, finally, perceived areas for further research and development to fully exploit these new materials are indicated.