Lightning Strikes
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Lightning Strikes
A few questions regarding lightning strikes:
Are a/c (esp large pax transport) hit very often?
If a/c are hit by stikes how do they survive - where is the electricity routed?
If you are on the ground ready for departure/takeoff and are hit by lightning, how is the electricity dissapted? Is this expected? Do you continue or return to the ramp for checks?
Any insight into company SOP on this would be real useful.
Are a/c (esp large pax transport) hit very often?
If a/c are hit by stikes how do they survive - where is the electricity routed?
If you are on the ground ready for departure/takeoff and are hit by lightning, how is the electricity dissapted? Is this expected? Do you continue or return to the ramp for checks?
Any insight into company SOP on this would be real useful.
Air carrier aircraft (in the US) are hit by lightning on the average of about once every 3000 hours.
It has been suggested that aircraft showing symptoms of static electricity (P static on the radio, or St Elmos fire) may be leaving an ionised wake, it is also possible that the jet exhaust leaves a similar wake, even if the aircraft isn't being charged by the environment. This wake acts as a charge path, so aircraft actually trigger lightning.
If an aircraft is hit, the electricity flows through the airframe, and exits on the other side (the airframe becomes part of the lightning's "circuit").
What can happen if an aircraft is hit? The worst is a fuel explosion. Jet A is by far the safest fuel to use, it will not normally form a combustible mixture in the tanks at the temperature at which a lighning strike is possible. There has never been a verified lightning caused fuel fire or explosion with an aircraft using Jet A.
Lightning caused fuel explosions have bought down a Pan Am 707 (Dec '63), an Iranian Air Force 747 (May '76), a US Air Force C-130E ('78) an F-4, F-16 and a KC-135, although all of these aircraft were at least partially filled with Jet B (JP-4).
The next worse thing that can happen is flame out (engine failure). Single flameouts due lightning strikes are fairly common on aircraft with aft mounted engines, dual flameouts have occured, although no accidents seem to have been recorded.
Small electric shocks have been reported by pilots, but nothing incapacitating.
Beyond this, various types of structural, avionics, electrical and magnatizing damage is possible. I have pictures of radomes blown apart, wing leading edges peeled back at the rivet line and such. This type of physical damage is usually cased by the sudden heat expansion of air due to arcing within an enclosed part of the aircraft structure, but is fairly rare.
If the aircraft suffers a lightning strike, a post lightning inspection is specified by the manufacturer in the maintenance manuals - which the engineers would carry out before the aircraft took off. In some cases, where the aircraft is at a remote port, an initial inspection can be carried out by the pilot, in order to certify the aircraft safe to fly to an engineering port for a full inspection.
Most of this information can be found in the excellent "Severe Weather Flying" by Dennis Newton.
Have a look here:
www.avweb.com/articles/lightnin.html
for a story & pictures of a typical strike in a GA aircraft (an Aerostar).
If you need a (free) password, visit the avweb home page:
www.avweb.com/
[This message has been edited by Checkboard (edited 29 May 1999).]
It has been suggested that aircraft showing symptoms of static electricity (P static on the radio, or St Elmos fire) may be leaving an ionised wake, it is also possible that the jet exhaust leaves a similar wake, even if the aircraft isn't being charged by the environment. This wake acts as a charge path, so aircraft actually trigger lightning.
If an aircraft is hit, the electricity flows through the airframe, and exits on the other side (the airframe becomes part of the lightning's "circuit").
What can happen if an aircraft is hit? The worst is a fuel explosion. Jet A is by far the safest fuel to use, it will not normally form a combustible mixture in the tanks at the temperature at which a lighning strike is possible. There has never been a verified lightning caused fuel fire or explosion with an aircraft using Jet A.
Lightning caused fuel explosions have bought down a Pan Am 707 (Dec '63), an Iranian Air Force 747 (May '76), a US Air Force C-130E ('78) an F-4, F-16 and a KC-135, although all of these aircraft were at least partially filled with Jet B (JP-4).
The next worse thing that can happen is flame out (engine failure). Single flameouts due lightning strikes are fairly common on aircraft with aft mounted engines, dual flameouts have occured, although no accidents seem to have been recorded.
Small electric shocks have been reported by pilots, but nothing incapacitating.
Beyond this, various types of structural, avionics, electrical and magnatizing damage is possible. I have pictures of radomes blown apart, wing leading edges peeled back at the rivet line and such. This type of physical damage is usually cased by the sudden heat expansion of air due to arcing within an enclosed part of the aircraft structure, but is fairly rare.
If the aircraft suffers a lightning strike, a post lightning inspection is specified by the manufacturer in the maintenance manuals - which the engineers would carry out before the aircraft took off. In some cases, where the aircraft is at a remote port, an initial inspection can be carried out by the pilot, in order to certify the aircraft safe to fly to an engineering port for a full inspection.
Most of this information can be found in the excellent "Severe Weather Flying" by Dennis Newton.
Have a look here:
www.avweb.com/articles/lightnin.html
for a story & pictures of a typical strike in a GA aircraft (an Aerostar).
If you need a (free) password, visit the avweb home page:
www.avweb.com/
[This message has been edited by Checkboard (edited 29 May 1999).]
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The only lightning strike that I experienced during my 31 year career occured about 15 years ago when flying a B-727-100 from Raleigh-Durham, North Carolina to Greensboro, N.C. Early morning departure, climbing thru 3000'. The thunder clap was awesome! After assuring the pax that the aircraft was not damaged in any way, and admitting that it scared us as well, we proceeded to GSO. The required mx inspection revealed a thumb-sized hole in the metal strap that retains the position light on the top of the T-tail. BTW, the FAA mandates a "Lightning Strike Report".
EBD.
EBD.
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OK here are a few basics......
If an a/c is hit in the air the charge takes the route to static discharge wicks on the wing/fin/stab trailing edge and is dissapated there.
If you are on the ground and get struck apart from the route through the ground engineers headset/ears/brain/boots! the charge earths through the u/c...but, I hear you say the tyres are rubber and this should insulate the a/c. Good point, but, the tyres have graphite in the rubber which conducts the charge to earth.
In the US I understand that if there is an electrical storm all personel are to stay away from the a/c.....No such luck in europe where we just dodge the lightning!!
Love
Le Pen
PS Yeah sorry about that... I should have said it takes the most direct route out through the skin...Residual charge is lost through static wicks why else do we replace them so frequently if they are not used.
Even 777s are not immune...I had a 2 inch hole in the lwr fuse at ORY a while back.
[This message has been edited by Le Pen (edited 27 May 1999).]
[This message has been edited by Le Pen (edited 29 May 1999).]
If an a/c is hit in the air the charge takes the route to static discharge wicks on the wing/fin/stab trailing edge and is dissapated there.
If you are on the ground and get struck apart from the route through the ground engineers headset/ears/brain/boots! the charge earths through the u/c...but, I hear you say the tyres are rubber and this should insulate the a/c. Good point, but, the tyres have graphite in the rubber which conducts the charge to earth.
In the US I understand that if there is an electrical storm all personel are to stay away from the a/c.....No such luck in europe where we just dodge the lightning!!
Love
Le Pen
PS Yeah sorry about that... I should have said it takes the most direct route out through the skin...Residual charge is lost through static wicks why else do we replace them so frequently if they are not used.
Even 777s are not immune...I had a 2 inch hole in the lwr fuse at ORY a while back.
[This message has been edited by Le Pen (edited 27 May 1999).]
[This message has been edited by Le Pen (edited 29 May 1999).]
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Le Pen, Starting rumours? Static discharge wicks are not lightning strike dissipators. They are not always capable of dissipating static electricity much less a lightning strike.
I have been in aircraft that were hit by lightning in flight. One strike left a hole in the top of the rudder big enough for me to put my hand through. There were also about 20 small, pin prick, holes in the wing tanks and most of the avionics were damaged.
I saw a Beechcraft get hit by lightning on the ground. All the lights came on for a few seconds. The lightning came out of the propeller blade closest to the ground and blew a small hole in the asphalt. I was only about 50 feet away from it at the time.
Yes, in the US ground personnel are supposed to stay away from the aircraft when there is lightning in the area. The southeastern states, especially Florida, get a lot of lightning. The spring and summer months are the worst. People are killed by it every year.
I have been in aircraft that were hit by lightning in flight. One strike left a hole in the top of the rudder big enough for me to put my hand through. There were also about 20 small, pin prick, holes in the wing tanks and most of the avionics were damaged.
I saw a Beechcraft get hit by lightning on the ground. All the lights came on for a few seconds. The lightning came out of the propeller blade closest to the ground and blew a small hole in the asphalt. I was only about 50 feet away from it at the time.
Yes, in the US ground personnel are supposed to stay away from the aircraft when there is lightning in the area. The southeastern states, especially Florida, get a lot of lightning. The spring and summer months are the worst. People are killed by it every year.
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I have only had the kind of lightning strike which leaves holes or melts a bit of windshield, hail is generally more dangerous.
However, my wife used to be a flight attendant and, while strapped in for anticipated turbulence, watched something akin to a glowing ball glide slowly down the centre aisle.
Spooky or what?
I haven't heard of other similar occurrences but am familiar with the term "ball lightning".
Over the tropical Atlantic last year I saw for the first time a plume of static shoot momentarily forward from the radome like dragon's breath.
You do this job for so long and there is always something round the corner to amaze you.
Anyone else with interesting electrical encounters?
However, my wife used to be a flight attendant and, while strapped in for anticipated turbulence, watched something akin to a glowing ball glide slowly down the centre aisle.
Spooky or what?
I haven't heard of other similar occurrences but am familiar with the term "ball lightning".
Over the tropical Atlantic last year I saw for the first time a plume of static shoot momentarily forward from the radome like dragon's breath.
You do this job for so long and there is always something round the corner to amaze you.
Anyone else with interesting electrical encounters?
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A few years ago a mate of mine was captain of a Nimrod going westbound across the Atlantic. They suffered a lightning strike causing my mate to be temporarily blinded. A ball of lightning appeared in the cockpit, hovered between the two pilots and then gently floated gently backwards through the aircraft. It then suddenly accelerated and disappeared up inside the tail with a loud bang. Most systems seemed to work normally but they diverted as a precaution. On the ground all appeared normal but on closer inspection the next morning they discovered the top of the fin was gone, along with the MAD boom.
Interesting to hear. Most scientists doubt that "Ball Lightning" exists. Lightning is just electricity, and electricity is just a bunch of electrons going somewhere in a hurry - that is you need a circuit.
In this model "Ball" lightning is impossible, as no ciruit exists. Some scientists have attempted to produce glowing plasma in the lab using electrical effects but so far (to my knowledge) have been unsuccessful.
The other theory is a retinal after effect, similar to glancing at the sun (don't do this!)
In this model "Ball" lightning is impossible, as no ciruit exists. Some scientists have attempted to produce glowing plasma in the lab using electrical effects but so far (to my knowledge) have been unsuccessful.
The other theory is a retinal after effect, similar to glancing at the sun (don't do this!)
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I used to live in Kununurra, a small town in the East Kimberley in Western Australia. In teh Wet season many thunderstorms occur. During one, I was closing a metal gate when I saw a brilliant flash and my hands were locked onto the wet gate. I was pulled violently on to the gate and I felt an incredible pulsing senstion through my arms. It was all over in an instant, and I ran inside. My hands looked like they had been scalded and my muscles in my arm, chest and upper back ached for a week. Yep, the bruises took a while to heal too. I believe the fence had been hit some way up the street and it was conducted to me. Ouch was all I could say at the time.. It was raining heavily and I was wearing rubber soled running shoes at the time.
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reddo
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reddo
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Lightning strikes were common during the piston and early turbine powered era when weather radar was not available. Weather radar was required to be fitted to all RPT turbine aircraft in Australia in 1963 as an aftermath of the breakup of a Vickers Viscount over Botany Bay the previous year.
Once airborne in weather there was no way of locating and avoiding storm cells and adverse weather encounters with turbulence,icing,lightning and/or hail were not uncommon.
Evidence of this can be seen on the DC3 aircraft still flying today which have numerous indentations about the windshields and on the fuselage in line with the propeller plane of rotation.
Hail was by far the greatest worry. Fortunately the slower speeds of the era enabled survival from these encounters as with turbulence as well.The same encounters at four times the speed of today's aircraft would result in impact forces sixteen times as severe.
Weather radar helps avoid all these risk factors including lightning. Nevertheless lightning strikes still occur even well away from storm cells and modern aircraft cope well with this.
Lightning can be from cloud to cloud, cloud to ground, or vice versa, I am told by some experts.In practice it matters not which way it goes. What is of interest is if an aircraft is in it's path.
My impression gained from quite a few in the piston era is that cloud....aircraft....cloud are not as severe as and aircraft becoming betwixt the cloud...
ground or vice versa event. We have all seen lightning travel across the sky for long distances in a bluish spidery pattern and it is not surprising that encounters with this type is difficult to avoid and is relatively common.In my experience although spectacular they are a far cry from the other kind.
Strikes between ground and cloud seem to have more zing in them and are much more spectacular.The kind of thick orange tinged strike which moves vertically between ground and cloud when it transits through an aircraft leave a lasting impression on the optic nerve (hence keep a low profile) and memory, as well as significant damage to some parts of the airframe,generally at the exit points. This kind of strike generally resides beneath and in close proximity to the storm cell. Generally weather radar enables avoidance of these areas and so this kind are less frequent.
The principle of the Faraday's Cage protects the occupants of a hollow container (the aluminium tube);that is, that the electric charge travels to the outside of such a vessel.
Modern aircraft cope well with strikes overall especially when you consider all the electrics,glass screens etc. Being struck in a gasoline fuelled aircraft is not appealing although there are very few mishaps attributed to ignition to fuel vapours. There is some evidence that some turbine aircraft were lost in this way as a result of using JP4 fuel. This type of fuel is no longer used by airlines to my knowledge.
Static discharge wicks are just that and dissipate the static charge built up by the friction of air moving over the surfaces during flight.
All the above is based on personal observation and I do not lay claim to expert knowledge on the matter.
ON THE GROUND STAY INDOORS WHEN LIGHTNING IS ABOUT!!
Once airborne in weather there was no way of locating and avoiding storm cells and adverse weather encounters with turbulence,icing,lightning and/or hail were not uncommon.
Evidence of this can be seen on the DC3 aircraft still flying today which have numerous indentations about the windshields and on the fuselage in line with the propeller plane of rotation.
Hail was by far the greatest worry. Fortunately the slower speeds of the era enabled survival from these encounters as with turbulence as well.The same encounters at four times the speed of today's aircraft would result in impact forces sixteen times as severe.
Weather radar helps avoid all these risk factors including lightning. Nevertheless lightning strikes still occur even well away from storm cells and modern aircraft cope well with this.
Lightning can be from cloud to cloud, cloud to ground, or vice versa, I am told by some experts.In practice it matters not which way it goes. What is of interest is if an aircraft is in it's path.
My impression gained from quite a few in the piston era is that cloud....aircraft....cloud are not as severe as and aircraft becoming betwixt the cloud...
ground or vice versa event. We have all seen lightning travel across the sky for long distances in a bluish spidery pattern and it is not surprising that encounters with this type is difficult to avoid and is relatively common.In my experience although spectacular they are a far cry from the other kind.
Strikes between ground and cloud seem to have more zing in them and are much more spectacular.The kind of thick orange tinged strike which moves vertically between ground and cloud when it transits through an aircraft leave a lasting impression on the optic nerve (hence keep a low profile) and memory, as well as significant damage to some parts of the airframe,generally at the exit points. This kind of strike generally resides beneath and in close proximity to the storm cell. Generally weather radar enables avoidance of these areas and so this kind are less frequent.
The principle of the Faraday's Cage protects the occupants of a hollow container (the aluminium tube);that is, that the electric charge travels to the outside of such a vessel.
Modern aircraft cope well with strikes overall especially when you consider all the electrics,glass screens etc. Being struck in a gasoline fuelled aircraft is not appealing although there are very few mishaps attributed to ignition to fuel vapours. There is some evidence that some turbine aircraft were lost in this way as a result of using JP4 fuel. This type of fuel is no longer used by airlines to my knowledge.
Static discharge wicks are just that and dissipate the static charge built up by the friction of air moving over the surfaces during flight.
All the above is based on personal observation and I do not lay claim to expert knowledge on the matter.
ON THE GROUND STAY INDOORS WHEN LIGHTNING IS ABOUT!!
In the US, on average, one golfer a week is killed or injured by lightning.
Of the people struck by lightning, men makes up two thirds, women one third (probably because more of them play golf in silly conditions!)
Around the world, lightning strikes are estimated to be occurring at the rate of one hundred per second.
A lightning bolt can exceed one hundred million volts, and reach temperatures hotter than the surface of the sun.
Of the people struck by lightning, men makes up two thirds, women one third (probably because more of them play golf in silly conditions!)
Around the world, lightning strikes are estimated to be occurring at the rate of one hundred per second.
A lightning bolt can exceed one hundred million volts, and reach temperatures hotter than the surface of the sun.
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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
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
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I remember seeing an item on a program about lightning concerning problems with a light a/c. A/c (either a single engined Piper or Cessna; pilot only; extra fuel tank) was crossing Atlantic west to east and was just over half way when was struck by lightning and lost complete electrical system - no long range radio; no navigation and even had to use hand fuel with fuel system. Luckily had short range radio (handheld?) and was able to contact another a/c on similar track which anebled him to reach land safely. Same prog also had segment about NASA/NACA trials with small jet a/c (poss T38) heavily instrumented/camera fitted and flown into storm clouds to see what happened.
[This message has been edited by Mycroft (edited 03 June 1999).]
[This message has been edited by Mycroft (edited 03 June 1999).]
[This message has been edited by Mycroft (edited 03 June 1999).]
[This message has been edited by Mycroft (edited 03 June 1999).]
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I remember seeing a TV documentary about investigation into "ball lightning".
The scientists had deduced that it could not happen following normal laws of physics and, sure enough, they could not produce it in the lab.
However, your jet airplane up in the sky is not in quite the same situation as a ground based lab.
By definition it is not earthed (grounded) so who knows what an electrical discharge or accumulation of static may do.
Imagine what their reaction would have been if they had a dose of St Elmo's on the car windshield during the ride home.
The scientists had deduced that it could not happen following normal laws of physics and, sure enough, they could not produce it in the lab.
However, your jet airplane up in the sky is not in quite the same situation as a ground based lab.
By definition it is not earthed (grounded) so who knows what an electrical discharge or accumulation of static may do.
Imagine what their reaction would have been if they had a dose of St Elmo's on the car windshield during the ride home.
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I remember seeing a TV documentary about investigation into "ball lightning".
The scientists had deduced that it could not happen following normal laws of physics and, sure enough, they could not produce it in the lab.
However, your jet airplane up in the sky is not in quite the same situation as a ground based lab.
By definition it is not earthed (grounded) so who knows what an electrical discharge or accumulation of static may do.
Imagine what their reaction would have been if they had a dose of St Elmo's on the car windshield during the ride home.
The scientists had deduced that it could not happen following normal laws of physics and, sure enough, they could not produce it in the lab.
However, your jet airplane up in the sky is not in quite the same situation as a ground based lab.
By definition it is not earthed (grounded) so who knows what an electrical discharge or accumulation of static may do.
Imagine what their reaction would have been if they had a dose of St Elmo's on the car windshield during the ride home.
Guest
Posts: n/a
Getting struck by sparks is a weekly event here in monsoon country in the Wet. The books are full of AVOID! AVOID! AVOID! but in real life its only 60% of the time you can dodge and weave sucessfuly. The other 40% is having to plow through it regardless.
The 2 aircraft Ive been electrically hit in regularly are the 747 and 737. In the 747 its been the tailfin/wings/D1L. In the 737 its ALWAYS been just under my sliding window!
Lightning packs a huge voltage but buggerall amps. Thus airframe damage tends to be minor but noticeable. But this reassuring model went tits up one night enroute to Bangkok when a bolt struck my radome and blew half of it to bits!
But genarally I found lightning strikes affects radio com/nav equipment. The ADFs in both types may play up and a genny might get knocked off line. Almost always youve lost one HF set. You lose the VOR if the bolt strikes the antenna square on.
All strikes Ive encountered have always been below 30000 feet.
Lightning strikes should be reported on arrival and entered in the tech log.
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Slasher. Lightning magnet.
The 2 aircraft Ive been electrically hit in regularly are the 747 and 737. In the 747 its been the tailfin/wings/D1L. In the 737 its ALWAYS been just under my sliding window!
Lightning packs a huge voltage but buggerall amps. Thus airframe damage tends to be minor but noticeable. But this reassuring model went tits up one night enroute to Bangkok when a bolt struck my radome and blew half of it to bits!
But genarally I found lightning strikes affects radio com/nav equipment. The ADFs in both types may play up and a genny might get knocked off line. Almost always youve lost one HF set. You lose the VOR if the bolt strikes the antenna square on.
All strikes Ive encountered have always been below 30000 feet.
Lightning strikes should be reported on arrival and entered in the tech log.
---------------------------------------
Slasher. Lightning magnet.
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At Canadian airports there is a thunderstorm alert (known as THOR) when there is lightning within a few km of the airport as registered by a special sensor. So during a T-storm and for 15 min after the last strike the ramp area is shutdown - no ramp operations and, of course, no refuelling. (Who would want to be sitting on 80,000 gal of jetfuel in a T-storm?). Airports are equipped with strobe lights on the passenger bridges which alert the ground crew to go indoors. It happens sometimes that you land with t-showers around, taxi to the gate and then sit 100m out waiting for the ground crew - frustrating after a long trip, but understandable for the ramp rats.
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Approximately four years ago, lightening struck the Delta ramp building at KMCO which zapped the flap computers on a Delta 767 and a Leisure 767 whilst parked on there respective stands. The electomagnetic energy from a nearby electrical storm can be detrimental to the functionality of computers. Neither aircraft had been directly struck.
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While overflying India at night at FL240 in a CL44 in the late 70,s, we found ourselves suddenly in the middle of a nasty Cb. Besides the rather bad turbulence we got hit by lightning : extremely loud bang, funny smell in the cockpit, both VORs gone, HF gone . Only 1 NDB still working. Diverting in Bombay (was called like this in those days) was elected not to be a good option under the circumstances, and we finally found Muscat on the other side with the help of daylight.
On the ground we found HF antenna physically missing and VOR antenna ripped off its mountings but still hanging there (Good cables)Frightening experience though...
On the ground we found HF antenna physically missing and VOR antenna ripped off its mountings but still hanging there (Good cables)Frightening experience though...
