Design and Testing for Lightning Strike Tolerance of the new AH-64 Apache Composite Main Rotor Blade

Boeing is currently developing a new Composite Main Rotor Blade (CMRB) for the AH-64D Apache Longbow Attack Helicopter. The qualification of the CMRB is funded under the Apache Longbow Block III modernization contract. One requirement for the qualification of the CMRB is a full scale demonstration test for direct lightning effects. In addition to the aggressive cost and performance goals, the CMRB was designed to meet the Apache Block III system performance specification for many specific operational requirements including tolerance to a direct lightning event. The blade must be capable of receiving a direct lightning strike without resulting in catastrophic damage to the blade, rotor system or aircraft. One of the goals of the CMRB development effort was to provide a design solution that would minimize the resulting damage from a direct lightning strike and allow for safe operation and landing following the occurrence of this event during flight. Since this area of capability on the CMRB had not been demonstrated by analysis or testing prior to the qualification, Boeing decides to perform a series of risk reduction lightning strike tests on representative full-scale segments of the CMRB structure. The tests were performed to provide the CMRB integrated product team (IPT) with the opportunity to evaluate the resulting damage to the structure after a direct lightning strike. If the results of these risk reductions tests had indicated that the design was deficient with respect to its ability to withstand a lightning strike, improvements to the design of the CMRB could have been implemented prior to the qualification testing. Based on the results of the risk reduction testing, the design of the CMRB has shown to be more than adequate for providing lightning strike tolerance. No additional features or changes were implemented to the design of the CMRB to alter or improve the lightning strike tolerance prior to the fabrication of blades for production qualification.