ABNORMAL EVENTS-LIGHTENING STRIKE

Lighting always has two or more attachments points (One entry and one exit) one the aircraft skin. Lighting moves back along the surface of the aircraft (swept stroke zone). This can cause a chain of scattered attachments points along a line in the direction of travel of the aircraft.Lighting hits some areas more frequently than others.

Aircraft Zoning :

The aircraft is divided into three zones related to the probability of lighting strike:

Zone 1 : Surfaces where there is high probability of initial lighting attachment entry or exit (leading edge, trailing edge, nose)

Zone 2 : Surfaces where there is high probability of a “swept stroke zone”. The lighting has its initial point of attachment in zone 1 and moves into zone 2.

Zone 3 : All zones of aircraft that are not zone 1 and zone 2, i.e. low probability of attachment of a lighting strike.

Effect Of Lightening :

There are two types of possible risks to aircraft:
1: Indirect effect
2: Direct effect

Indirect Effects :

Electromagnetic fields related to the lighting attachment can cause unwanted transient voltages and currents in the aircraft wiring systems. In some conditions (low intensity strike, high protection) the effect can be temporary and the system can operate correctly again after the strike.
In other conditions (low protection, no circuit protection devices) the damage can be permanent requiring L.R.U replacement.

Direct Effects :

1)    Pitting / melt through
2)    Magnetic forces
3)    Resistive Heating
4)    Acoustic shock wave

INSPECTION REQUIREMENTS:

 1)Aircraft are designed to keep the effects of lightning to a minimum and make sure it can continue its flight and land safely after a lightning attachment.

2)It is necessary to do a full inspection after a lightning strike to make an estimate of the damage and then to judge through MMEL aircrafts can continue to service or not.

INSPECTION PREPARATIONS:

 1) Before you start, you get information from the crew about the flight condition.
 
2) All events reported by the crew must be checked in addition/conjunction with this inspection
 
3) Take all safety precaution/safety devices are installed.
 
4) Extension of flight control surfaces (Flaps,slats,spoilers & speed brakes)

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