Hopefully following this is the 1st 2 pages of Maint manual for 747-400 Lighning strike inspection. Just to give you some idea of where we have to start. Could take as long as 4 hrs to complete.
LIGHTNING STRIKE CONDITION (CONDITIONAL INSPECTION) - MAINTENANCE PRACTICES ____________________________________________________________ _______________
1. General _______ A. This procedure has these three tasks: (1) Examine the External Surfaces for Lightning Strike (2) Examine the Internal Components for Lightning Strike (3) Inspection and Operational Check of the Radio and Navigation Systems B. The airplane has all the necessary and known lightning strike protection measures. Most of the external parts of the airplane are metal structure with sufficient thickness to be resistant to a lightning strike. This metal assembly is its basic protection. The thickness of the metal surface is sufficient to protect the internal spaces from a lightning strike. The metal skin also gives protection from the entrance of electromagnetic energy into the electrical wires of the aircraft. The metal skin does not prevent all electromagnetic energy from going into the electrical wiring; however, it does keep the energy to a satisfactory level. If lightning strike strikes the airplane, you must fully examine all of the airplane to find the areas of the lightning strike entrance and exit points. When you look at the areas of entrance and exit, examine this structure carefully to find all of the damage that has occurred. C. Lightning strike entrance and exit points are usually found in Zone 1 (Fig. 201), but can also occur in Zone 2 and 3. D. You can usually find signs of a lightning strike in Zone 1 (Fig. 201). However, lightning strikes can occur to any part of the airplane which includes the fuselage, wing skin trailing edge panels, wing-body fairing, antennas, vertical stabilizer, horizontal stabilizer, and along the wing trailing edge in Zone 2 (Fig. 201). E. In metal structures, lightning damage usually shows as pits, burn marks or small circular holes. These holes can be grouped in one location or divided around a large area. Burnt or discolored skin also shows lightning strike damage. F. In composite (non-metallic) structures, solid laminate or honeycomb damage shows as discolored paint. It also shows as burned, punctured, or delaminated skin plies. Damage you cannot see can also be there. This damage can extend around the area you can see. Signs of arcing and burning can also occur around the attachments to the supporting structure.
G. Airplane components made of ferromagnetic material may become strongly magnetized when subjected to lightning currents. Large current flow from the lightning strike in the airplane structure can cause this magnetization. H. A lightning strike usually attaches to the airplane in Zone 1 (Fig. 201) and goes out a different location in Zone 1. Frequently a lightning strike can enter the nose radome and go out of the airplane at one of the horizontal stabilizer trailing edges. The external components most likely to be hit are listed below: (1) Nose Radome (2) Nacelles (3) Wing Tips (4) Horizontal Stabilizer Tips (5) Elevators (6) Vertical Fin Tips (7) Ends of the Leading Edge Flaps (8) Trailing Edge Flap Track Fairings (9) Landing Gear (10) Water Waste Masts (11) Pitot Probes I. Zone 2 (Fig. 201) is where an initial entry or exit point is not usual, but where a lightning channel may be pushed back from an initial entry or exit point. As an example, the nose radome may be the area of an initial entry point, but the lightning channel may be pushed back along the fuselage aft of the radome by the forward motion of the airplane. J. Lightning strikes can cause problems to the electrical power systems and the external light wiring. The electrical system is designed to be resistant to lightning strikes. But, a strike of unusually high intensity can possibly damage the electrical system components below: (1) Fuel Valves (2) Generators (3) Power Feeders (4) Electrical Distribution Systems K. Frequently, a lightning strike is referred to as a static discharge. This is incorrect and may cause you to think that the static dischargers found on the external surfaces of the airplane prevent lightning strikes. These static dischargers are for bleeding off static charge only; they provide no lightning protection function. As the airplane flies through the air, it can pick up a static electrical charge from the air (or dust/water particles in the air). This static charge can become large enough to bleed off the airplane on its own. If the charge does not bleed off on its own, it will usually result in noise on the VHF or HF radios. The static dischargers help to bleed the static charge off in a way that prevents radio noise.
L. The static dischargers are frequently hit by lightning. The dischargers have the capacity to carry only a few micro-Amps of current from the collected static energy. The approximate 200,000 Amps from a lightning strike will cause damage to the discharger or make it fully unserviceable.
2. Examine External Surfaces for Lightning Strike Damage _____________________________________________________ A. References (1) AMM 23-61-01/201, Static Dischargers (2) AMM 28-11-00/201, Fuel Tanks (3) AMM 28-11-03/401, Door - Access, Wing Surge Tanks (4) AMM 23-11-00/001 HF, Communications System (5) AMM 23-12-00/001 VHF, Communications System (6) AMM 27-11-00/201, Ailerons (7) AMM 27-21-00/501, Rudder (8) AMM 27-31-00/501, Elevators (9) AMM 28-41-00/501, Fuel Quantity Indicating System (10) AMM 34-22-00/201, Standby Magnetic Compass (11) AMM 34-31-30/201, ILS Navigation System (12) AMM 34-32-00/501, Marker Beacon System (13) AMM 34-33-00/501, Radio Altimeter System (14) AMM 34-43-00/501, Weather Radar System (15) AMM 34-51-00/501, VOR System (16) AMM 34-53-00/501, ATC System (17) AMM 34-55-00/501, DME System (18) AMM 34-57-00/501, Automatic Direction Finder (ADF) (19) AMM 53-52-01/201, Nose Radome (20) SRM 51-70-14/001 Allowable Damage and Repair of Flame-Sprayed Aluminum Coatings (21) D6-7170 Nondestructive Instrumental Tests for Structure