Maintaining electrical protection on the 777

A scheduled maintenance program is essential for aircraft protection against high-intensity radiated fields and lightning.

Advances in electrical and electronic systems technology have been incorporated into the Boeing 777, and especially significant is the implementation of fly-by-wire technology, which is used to perform critical functions such as control of flight surfaces and engines. These types of systems are susceptible to induced electrical currents and voltages produced by high-intensity radiated fields and lightning (HIRF/L). Induced transient currents and voltages can degrade electrical and electronic system performance by damaging components and/or upsetting system functions. System designers have considered grounding components and installing shielded cables. Degradation of the protective features due to in-service factors could result in equipment damage or erroneous signals.

A high-intensity radiated field (HIRF) is electromagnetic interference generated outside the airplane by manmade ground or airborne emitters. Increased power from transmitters including radar, radio, and television produce large amounts of electromagnetic waves that contribute to the HIRF environment, the frequency range of which is 10 kHz to 18 GHz.