MODUK - DEF STAN 59-113
Lightning Strike Protection Requirements for Service Aircraft
|Publication Date:||14 October 2019|
The aim of this standard is to define the design, evaluation and testing requirements, with risk assessment procedures, to be used for ensuring the safety and suitability for service of UK Military Aircraft when exposed to a lightning threat.
These Standard states the minimum requirements for the design of aircraft in order to protect them and the crew from the effects of lightning strikes. It shall apply to all fixed and rotary wing aircraft which are procured against Def Stan 00-970. It does not apply to air launched weapons and weapon systems; the requirements for which are given in NATO STANDARD AECTP-500 - Category 508 Ordnance/Munitions Verification and Testing but it does apply to the aircraft pylons and launchers.
The standard covers the cases of both a direct strike, where the lightning channel attaches to the aeroplane, and a nearby flash, where, although there is no contact, the aeroplane is near enough for it or the crew to possibly be affected by the electromagnetic fields or the aerodynamic shock wave.
Far field effects, are the effects of exposure to the radiated electromagnetic field of a distant lightning flash. The effects are not addressed in this Def Stan as protection is automatically provided by indirect effects hardening.
Direct effects arise directly from the passage of lightning current and are therefore present only in direct strikes. Possible hazards include puncture of the aeroplane skin, including that of fuel tanks, and fire or explosion due to sparking or hot spots. Indirect effects are due to coupling with the electromagnetic fields of the lightning current flowing in the aeroplane or in the lightning flash itself. These effects may therefore arise as a result of either a direct strike or a nearby flash. Possible hazards include malfunction of electronic equipment, or permanent damage to it, due to induced transient voltages or currents. Leader phase effects, such as corona or dielectric puncture, are the effects due to the high electrical stress that occurs as a lightning leader attaches to the aircraft.