Composites and lightning discussion (extracted from AF A330 thread)

[Bus429]

Speculation - even in some cases here, informed speculation - is just that. However, as a general comment - and not connected to this tragedy, journos - the TWA 800 tragedy in 1996 caused a review of aircraft designs related to fuel tanks, hence FTS/CDCCL (and SFAR 88). One of the considerations was/is, of course, lightning as well as on-board causes such as compromised or ageing sytems, bonding, wiring or tank components (it is a very complicated subject). Bonding is fundamental to protection against electrical faults and is sometimes more difficult to assure with composites.
SFAR 88 and equivalent JAA/EASA documents required TCHs to assess their designs with respect to ignition sources. This spawned a whole raft of ADs and requirements such as training for those involved in continuing airworthiness functions (including maintenance), the need to maintain design characteristics (in maintenance, maintenance documents and planning functions) and the need to adhere to approved data when maintaining and planning maintenance.
(For example, as part of the assessment required under SFAR 88, some arc-testing on fuel tank components related to FQIS revealed that components passing 2000v arc tests when new arced at less than 50v when over 30 years old).
To iterate: a general comment only. Let's wait for the official report.

[win_faa]

I've read some of the previous posts regarding the susceptibility of composite materials from lightning strike.

Because weight is a major consideration in aeronautic design, aircraft structures, like wings, flight controls are made of light-weight yet strong composite materials. These materials are made up of several layers of different composites, and in these layers the materials often have a different orientation to increase strength. But, because these modern composites exhibit strongly anisotropic electrical and thermal conductivities and because they have low conductivity compared to metals, when the high electric currents due to a lightning strike flow through them, they experience a high temperature rise and are vulnerable to heating damage. The heat flowing through the composite structure also has an effect on aircraft parts close to the location of the strike.

One probably cause maybe...

[stadedelafougere]

No IGGS on A330/340 as far as I know.

Last July (July 12th 2008 if I remember well), FAA made it compulsory on new programs to have "tank inerting systems" installed, so both B787 and A350 will be equipped.

I haven't heard of any commercial airliner being equipped apart from the 787 and A350.

[Lamyna Flo]

Does anyone know if the A340 is fitted with a similar system?

Not quite sure what the A340 has to do with this thread? A/c in question was a 330.

[Bandit FO]

It's coming soon on the 777.

[barrymung]

Reply to #203:

I hope it's not a fuel tank explosion either! :eek:

I have worked within the EMC field for some years and was only last week reading about the (theoretical) problems faced by aircraft designers with regards to lightning hitting carbon fibre sections.

Lightning Strike Protection For Composite Structures: COMPOSITESWORLD.COM (http://www.compositesworld.com/articles/lightning-strike-protection-for-composite-structures.aspx)

[parkaboy]

The 787 *must* have fuel tank inerting - along with two other EMI protection schemes - interference-fit fasteners and metallic earthing paths in the wing skin. It needs these because of the very poor electrical conductivity in CFRP and cannot be certified without them. This is not just a lightning strike issue, it is to cope with component failure currents also.

Airbus have the same requirements on the A350. Implying that Airbus have a more lax approach to limiting in-tank ignition is incorrect.

I also recall that hull losses attributed to lightning strike include two Boeing a/c and no Airbus airframes (Aviation Losses from Lightning Strikes - National Lightning Safety Institute (http://www.lightningsafety.com/nlsi_lls/avaition_losses.html))..

[Green-dot]

It's coming soon on the 777.


Recently incorporated on newly delivered 737NG.

[stadedelafougere]

Commercial aircraft with a lot of composites will probably be equipped with metallic grids within the composite material, to lead the current towards a metallic skeleton (though light) that is located within the fuselage to duct the heavy voltage current through the fuselage (and wings TBC) without damaging the structure of the aircraft.
http://www.flightglobal.com/articles/2007/09/28/217062/metallic-strips-will-ensure-electrical-continuity-in-a350s-carbon.html (One article on this subject)

[win_faa]

^^ but it depends on how well the structures are bonded with each other. When lightning hits a composite structure, which is the reason why lighting strikes cause burn marks on the skin. After a lightning strike, repairs must be done properly to regain the conductive path, but if this is not done correctly it may cause alot of problems to the structure.

[deSitter]

Just to clarify the physics - in a metal, the current must flow over the surface - so everything inside is completely protected in an all-metal airplane (assuming good corrosion maintenance). In CFC, a poor conductor, the current can penetrate into the body of the material and create tremendous heat, destroying the material through explosive fragmentation and vaporization. Once a tall tree in my front yard took a large lightning strike. The 100 ft tree was reduced to a 10 ft stump and pieces of it were found a block away. No piece larger than a football was found. The remaining wood fibers were splayed out like an old paint brush. The same thing can happen to CFC, completely disrupting air flow around the damaged area. My guess is that one way or the other, composites are involved here, either through direct structural failure or otherwise, and we're looking at an industry-changing event.

-drl

[slings]

Not completely true newer B737 also havd nitrogen systems in fuel tanks.

[Michael Birbeck]

Desitter wrote

My guess is that one way or the other, composites are involved here, either through direct structural failure or otherwise, and we're looking at an industry-changing event.


The lightning hypothesis still remains a possibility and will beg many questions about composite aircraft materials but any investigation requires the discovery and retrieval of the aircraft and more specifically any composite components that might have been compromised by a lightning strike.

Given the huge area that will need to be traversed and the likelihood of mid air disintegration, the chances of definitive component failure mode identification remain pretty low I think.

Given the Cb and turbulence hypothesis, other material failure modes e.g. failure under high bending moment will also, of course, feature as possible causes.

Truth is we just don't know and the thought that over 200 people have probably lost their lives is a very depressing one tonight.

[turtlehead]

A bit off the topic but as previosly mentioned the latest B737NG has Nitrogen Enriched Air pumped into the Centre Wing Tank Vent cavity. The flow varies with aircraft altitude and flight phase..........

No doubt they will collect more Data and the puzzle solved.............:confused:

I feel for the family and friends:sad:

[Jose22]

Technical concerns [related to] composite fuselage (http://en.wikipedia.org/wiki/Boeing_787):


Another concern arises from the risk of lightning strikes (http://seattletimes.nwsource.com/html/businesstechnology/2002844619_boeing05.html). The 787 fuselage's composite could have as much as 1,000 times the electrical resistance of aluminum, increasing the risk of damage during a lightning strike. Boeing has stated that the 787's lightning protection will meet FAA requirements. FAA management is planning to relax some lightning strike requirements, which will help the 787.

[barrymung]

QUOTE: "Remember, an airplane acts as a FARADAYS cage whereby the electronic loads stay on the outside of the cage!"

Not when it's got panels made of carbon fibre, it ain't!!

Lighning will jump through the carbon fibre and strike any piece of metal it can find behind!

The A330 has a horizontal tail made from carbon fibre which contains a huge fuel tank.

The wings, I believe have carbon fibre sections, these too contain fuel tanks!

The A330 doesn't have a "nitrogen fuel tank inerting" feature, that the carbon fibre boeings have, in order to reduce the risk of fuel tank explosion!

(I'm not saying that this is the cause.)

[Qatari515]

True about carbonfibre,


BUT


the carbonfibre in the tail or in any other part has a metal mesh inside for exactly this reason. Do you really believe authorities would certify an airplane with a possible explosive tailplane?

Dont think so....

[win_faa]

composites found on aircraft arent really that much of a concern during lightning strike as long as they are bonded properly particularly after doing composite repair...

[daikilo]

Whilst it is true that the A330 uses carbon fibre materials, where required they incorporate a conductivity network to cope with lighting strikes. This design principle has been used since the A310.

[IFIX]

Metal mesh or not, if there is any moisure within the composite, it will explode when struck by lightning.
The moisture will instantly expand to 800 times its normal volume causing it to fail.
The same mechanism caused the damage to the afore mentioned tree.

And finding moisture in a composite panel is not all that uncommon, especially if the panel has been damaged (impact) by tooling or other methods.

[rottenray]

Metal mesh or not, if there is any moisure within the composite, it will explode when struck by lightning.
The moisture will instantly expand to 800 times its normal volume causing it to fail.
The same mechanism caused the damage to the afore mentioned tree.

And finding moisture in a composite panel is not all that uncommon, especially if the panel has been damaged (impact) by tooling or other methods.


Not necessarily correct. Here's why.

First, although water is a fair conductor of electricity, it is also an unreliable one that tends to vaporize under high current - which creates your 800x expansion.

That's why the aforementioned tree exploded, it's why composite panels CAN explode when hit by large amounts of electricity, and it's how those $15 hot dog cookers where you put the dog in between 2 spikes work.


If there had been a 2-gauge copper wire running down the tree, it would have survived because the lightning would have followed that path instead. If you wrap your weiner in tinfoil before putting in your $15 hot dog cooker, it won't cook (don't do it, you'll blow the fuse) because the electricity will flow through it instead of the dog.


Lightning striking an aircraft is using the aircraft as a path because it conducts electricity better than the air around it - but these strikes are not typically at the "terminal current" of the lightning bolt. That's later, if/when it reaches the ground and explodes a tree.


LS micromesh under its intended application - providing a path for megavolts at low current - works just fine.

All it's doing is providing the path of least resistance from one part of "whatever" to another part of it.

And by doing so, it bypasses any moisture in the composite, thus the moisture doesn't heat because there is no current flow through it.


Repairs need to be done according to the mfr or there will be problems.

Not only does the physical integrity need to be maintained, the electrical continuity does as well or it's no longer a protected panel.


I've seen a fibreglass commercial pool filter housing literally explode when a loose 440 volt line contacted it - burned a tennis ball sized hole in the side and the steam blew the housing into shreds.


...

[The Deec]

I've seen lots of damage to composite components ,especially radome lighting damage. Much of the damage was superficial with clear signs of entry and exit holes which required removal of the bonding strips(radome damage) and the subsequent fibreglass repair but never anything that was outside the repair limits of the component . I cant imagine a composite component, be it fibreglass or carbon, being the cause of this accident.

[AIEXPATS]

Putting aside a catastrophic failure due to an explosion or structural failure due to turbulence experienced.
I find it very unlikely this A330 was operated (AF and it's very excellent training, maint. history and no doubt Crews) in any sort of unprofessional way! Aside from the A340 runway over-run and crash in Toronto on Aug. 2nd 2005, (which could have been avoided), AF has an excellent operational record.
So let us talk about electrical discharges.
Remember back in Jan. 19, 1995 when that Bristow heli was struck by lightning and ditched (successfully) in the North Sea?
The UK CAA realized later the electrical bolt was so powerful (>300,000 AMPS) it literally caused the partially composite tail rotor to explode (It was recovered from the Seabed and I believe the leading edge of the tail rotor was titanium metal which was the root cause of lightning attraction, transfer and melting). Tail rotors were redesigned after this.
I have read many articles that on the 787 there is a huge unknown risk of composite degradation and unpredictable reactions to very high temperature and Ampere lightning strikes.
So whether a possible HOT or COLD lightning strike were experienced by this aircraft with temps of 15-60,000 Deg. F and the related incredibly high AMPS, we may eventually see after recovery and analysis of debris another example of the unknowns of natural atmospheric conditions and the destructive effects it has on fly-by-wire and/or electronics and composite construction used in aircraft.
I believe the Los Alamos Laboratory FORTE satellite is still in low Earth Equatorial orbit , which makes several passes over that area and may if in the right spot had made measurements of tha area.
Of course we should assume that this aircraft may have been within or most likely many many miles away (the Crew would have used the radar returns and visual orientation to "pick their Track") from any electrically discharging Cell at the time and was just in the wrong place at the wrong time (assuming that a lightning strike was the or a contributing cause for this disaster).
I am confident the Crew was using all resources to maintain control of the a/c until the very bitter end.
Maybe even the ECAM or Non-normal Checklist were of no help in this final unwritten, untrained for or simulated situation? Think back to Lauda 004 on May 26, 1991 and their Nr.1 reverse thrust indication/deployment.
Maybe unlike CP Sully and his Crew, this was a no-win situation, then we Pilots will hopefully be given valuable information from the Investigation that will ensure for us, our Crews, Pax and cargo - safer operational levels.
Always very sad to hear of such events and condolences to all involved!

[bluesafari]

IFIX,
I find your comment regarding the effect of water in composite materials and lightning strikes very interesting, can you give me a reference for this information please, I am involved with aircraft that have carbon fibre and other composites in critical components.

[IFIX]

Bluesafari,
I'm sorry but I can't provide you with a straight reference to this effect of lightning srikes on an aircraft.

Several years ago the local church spire had a large hole blown into the side by lightning strike.
It had been raining for several days and quite some water had been absorbed by the bricks it was built from.
When it was struck by the lightning bolt, the water in the bricks expanded at such a high rate, a 6 by 4 meter hole was blown out.
It looked like the spire had been shelled by artillery except that all the debris was ejected outwards.

Logic would dictate most of the current should flow along the wet surface, but it did not, casing the damage.

At the heavy maintenance base I used to work we would use a thermal imaging camera to find water ingress in composite panels.
When viewing the a/c shortly after it touches down, the frozen water within the composites showed up clearly.

Pls remember the mesh which is applied to the surface of these panels, is very thin.
I have seen a/c being masked in the spraybooth where the masking was cut with a knife, unacceptable of course, but it does happen.
The mesh is easily damaged in this manner and after the a/c is painted this breech in lighning stike protection is undetectable.

To which extent this affects the lightning srike protection I do not know but it seems logical for temperatures in the composite to be at their highest value at these locations. (in the event of a lightning strike)

[Denti]

There was a fatal loss of a DA42 all composite piston twin last year in germany. Apparently it was hit by a lightning strike that caused explosive delamination of the elevator jamming it completely in the process.

That aircraft was relatively new, IFR approved and of course had metallic conductivity mesh inlaid into the composites. So it can happen that a lightning strike is too much for the relevant structure, however it seems to be rare given the large number of flighthours that part- or all composite airplanes have accumulated by now.

[IGh]

A comment from slot #24 above:
"... a possible HOT or COLD lightning strike were experienced by this aircraft ..."
? Can anyone provide any record of any airliner suffering a LIGHTNING strike while at 30,000 feet or above??

[Doors to Automatic]

This is surely consistent with a positive lightning strike?

Positive lighting is many more times more powerful than a standard negative strike but far rarer accounting for 5% of all strikes. It comes from the very top of the cloud sometimes striking through clear air many miles from the storm itself.

According to the Wikipedia article on lightning an average negative strkie carries 30 KiloApms of current whereas a positive strike averages around 300 with the strongest carrying 500 KiloAmps.

I have yet to establish whether modern aircraft can withstand the very strongest positive strikes (i.e those around the 500 KA mark).

Does anyone know what the maximum current a modern aircraft can withstand is?

[FullWings]

There's a lot of background information in this AAIB report (http://www.aaib.gov.uk/cms_resources/dft_avsafety_pdf_500699.pdf) from about 10 years ago. It's about a lightning strike to a composite glider just outside the London TMA but discusses a similar strike to a helicopter and the general theory and mechanics of electrical discharges. It also goes into why they thought aircraft protection standards were too low. Worth a read...

[barrymung]

If a composite structure gets hit by lightning, the charge will tend to make its way through the carbon fibre and spark towards the nearest metal structure WITHIN that part of the body. This is fact. Boeing apparently know of this issue, airbus apparently know of this issue.

The horizontal tail fin of an A330 is made of carbon fibre. The tail section also contains a huge fuel tank!

Boeing, knowing about this problem have added a "Nitrogen interter" system to the fuel tank. This removes any air from the top of the tank, replaces it with nitrogen and in theory reduces the risk of a fuel tank explosion.

Airbus A330/A340 planes do not feature this system but instead rely on metal strips on the tail to conduct the charge away. The fuel tank has air in the section above the fuel.

Carbon fibre does NOT act as a Faraday cage. It doesn't conduct electricity.

Obviously, if the plane in question were hit by lightning on the tail section, the rear fuel tank *might* have exploded. This would be consistent with current reports showing TWO distinct areas of debris, ie the plane came down in two parts.

This would also explain why the ACARS system was reporting massive power failures but continued to function for a few minutes. It'd also explain why the crew failed to communicate with ATC.

This is obviously only a theory but it *could* explain the events of Sunday/Monday.

[MrFixer!!!]

Guys......just trying to put bits and pieces of this jigsaw....I am sure there are quite a few guys here who know A330s well....( I AM ONLY ASSUMING).

I am no expert but just a few things which are bugging me from what I know about A330s and my experience on them.....

I am MORE interested in that ACARS message.....if that was sent that means there was power available in that system from the BUS2... that means there was full power supply from BUS2 feeding the other electrical buses......quoting from the 330 MM

Data Transmission (optional system)

The Data Transmission system comprises: (Ref. 23-20)

(1)
Aircraft Communications Addressing and Reporting System (ACARS) (Ref. 23-24)

The ACARS management unit allows management of the data transmitted to the ground (SDAC, FWC, AIDS, CMS, FMGEC) and entered by the crew. It also allows reception, printing and display of ground messages on the MCDU.
These data are transmitted through the VHF 3 system (or through the SATCOM system if installed).

(2)
Gate Link

The system allows a connection between the Aircraft Information Network System (AINS) and the airline ground based information system.

Its description is made in the Description/Operation of the AINS (Ref. 46-11).

Air-to-ground calls
When a call is initiated by an airborne subscriber, the AES sends signals to the GES, using the Rd-Channel. When the GES receives the call request, it assigns a pair of C-Channels, for a voice call, or reserves time on a T-Channel, for long-duration data transmissions. The call can then go through.
The assigned channels are reserved for as long as the call is in progress. The sequence used to initiate the call is automatic and transparent to both the originator and the receiver of the call.


ALSO......looking at the Power distribution schematic of this a/c everything essential is always powered (thats why its called essential)......


Cutting the crap.....I am looking at these units......

Electrical Contactor Management Unit (ECMU)
(Ref. 24-29-00)
The system consists of two separate equipment called ECMU1 and ECMU2.
Their functions are similar but the ECMU1 manages only side 1 contactors and ECMU2 manages only side 2 contactors.
Each ECMU receives the following signals:
-
orders from the GCUs and the GAPCU,


-
status of the main AC and DC generation contactors,


-
voltage of the main AC and DC busbars.


The two main functions of the ECMU are:

1
Operational function:

-
control of the AC/DC main contactors,


-
control of the galley shedding,


-
on ground, control of the transfer between the various electrical power sources (IDG, APU, EXT PWR) in order to avoid any break of power (NBPT),


-
control of AC/DC ground service busses,


-
control of Inadvertent Paralleling Trip (IPT).



2
BITE function

-
monitor and test the ECMU together with its peripheral circuits,


-
collect the failures and store the corresponding fault code in the Non Volatile Memory (NVM),


-
transmit the failure message to the Central Maintenance Computer (CMC) through an ARINC 429 bus.


In addition, in case of ECMU failure, a fault warning message is generated to the Engine/Warning Display (EWD).


(2)
Transfer circuit

(Ref. 24-22-00)
The Bus Transfer Contactors (BTC)s and the System Isolation Contactor (SIC) are automatically controlled by the ECMUs. They enable supply of all the aircraft electrical network or half of it.
The supply only depends on the availability of one of the five power sources: GEN1, GEN2, APU GEN, EXT PWR A and B.
The control of the BTCs also depends on the availability of these sources and the correct condition of each network.

(a)
Operation of BTC1

The BTC1 closes, if no interlock conditions exist on the GCU1:
-
when the GEN1 is not available, in order to supply the network 1 (AC BUS 1) from another power source (GEN2, APU GEN, EXT PWR A or EXT PWR B),


-
to supply the network 2 from GEN1 if the GEN2, APU GEN EXT PWR A and EXT PWR B are not available.



(b)
Operation of BTC2

The BTC2 closes if no interlock conditions exist on the GCU2:
-
when the GEN2 is not available in order to supply the network 2 from another power source (GEN1, APU GEN , EXT PWR A or EXT PWR B),


-
to supply the network 1 from the GEN2 if the GEN1, APU GEN , EXT PWR A and EXT PWR B are not available.



(c)
Latching logic of the BTCs

The BTC1 is latched open if a "GLC1 welded" failure or a short circuit not clarified by C/B tripping occurs at level of GEN1 channel.
The same latching logic is used for BTC2.

(d)
System Isolation Contactor (SIC)

The SIC closes automatically:
-
when the GEN2 and EXT PWR A are not available and APU GEN is available in order to supply network 2 from the APU GEN,


-
when the GEN1 and APU GEN are not available and EXT PWR A is available in order to supply network 1 from the EXT PWR A,


-
when the GEN2, APU GEN, EXT PWR A are not available and GEN1, is available in order to supply network 2 from the GEN1,


-
when the GEN1, APU GEN, EXT PWR A are not available and GEN2, is available in order to supply network 1 from the GEN2.



(e)
Priority order of power supply

Each network (1 or 2) is supplied in the following priority order:
-
1XP = IDG1/APU GEN/EXT PWR B/EXT PWR A/IDG2,


-
2XP = IDG2/EXT PWR A/APU GEN/EXT PWR B/IDG1.



(f)
Isolation of the two sides

The isolation of the two sides is possible by action on the BUS TIE pushbutton switch. This control is located on the ELEC control panel 235VU, cockpit overhead panel.


(3)
No Break Power Transfer (NBPT)

(Ref. 24-29-00)
This function is managed by the ECMUs. It prevents busbar power interruption due to electrical power supply source transfer on ground in normal configuration.
The ECMU receives information from the main AC contactors, each GCU and the GAPCU, to perform this function.
No break power transfer occurrences are permitted between:
-
any external power and the APU generator,


-
any IDG and any external power,


-
any IDG and the APU generator.



(4)
Distribution

(Ref. 24-50-00)
The alternating current distribution network comprises two independent sections.

(a)
Network 1

Network 1 mainly includes the AC BUS 1, the AC ESS BUS and the AC SHED ESS BUS which are three-phase, 115 VAC/400 Hz busses.
The AC BUS 1 supplies the essential busses in parallel. The AC ESS BUS also delivers 26 VAC/400 HZ power supply through a 115/26 VAC transformer.
In the event of the AC BUS 1 loss, the AC ESS BUS and AC SHED ESS BUS are automatically restored by the direct transfer of power supply from the AC BUS 2.
In case of loss of the AC essential busses, FAULT legend on the AC ESS FEED pushbutton switch comes on : this P/BSW enables to transfer the AC essential busses supply from AC BUS 1 to AC BUS 2, in particular when the loss of the AC essential busses normal supply does not result from AC BUS 1 loss.
If there is loss of AC BUS 1 and AC BUS 2 (emergency configuration), the AC ESS BUS and AC SHED ESS BUS are restored via the CSM/G driven by the Green hydraulic power. In case of RAT operation, the AC SHED ESS BUS is automatically shed.

(b)
Network 2

Network 2 comprises the AC BUS 2 which is a three-phase, 115 VAC/400 Hz bus.
The AC BUS 2 also delivers 26 VAC/400 Hz power supply through a 115/26 VAC transformer.





I am not a buyer of Lightening strike theory....having seen so many damages caused by them...however I would like to be proved wrong (After the investigation of this crash comes out).

According to Airbus......this is whats given regarding the A330s....

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

1
Zone 1:

-
surfaces where there is a high probability of initial lightning attachment (entry or exit).



2
Zone 2:

-
surfaces where there is a high probability of a "swept stroke zone". The lightning strike has its initial point of attachment in Zone 1 and moves into Zone 2.



3
Zone 3:

-
this zone includes all of the aircraft surfaces that are not in Zone 1 and 2. In Zone 3 there is a low probability of attachment of a lightning strike. However, high lightning currents can go through Zone 3 by direct conduction between 2 attachment points. Zone 3 currents will also go into Zones 1 and 2.




(b)
Zones 1 and 2 are divided into A and B areas related to the probability of continued attachment of the arc (hang on).

The probability of arc hang on is low in A areas and high in B areas.
1
Zone 1A:

-
area where there is a high probability of initial attachment and low probability of arc hang on, such as the forward-mounted pitot probes, the radome diverter strips and the nacelle leading edges.



2
Zone 1B:

-
area where there is a high probability of initial attachment and high probability of arc hang on, such as the wing, stabilizers and fin tips and some trailing edge areas.



3
Zone 2A:

-
a swept stroke zone with low probability of arc hang on, such as mid-chord regions of the wing surface, aft of an engine and the total fuselage surface.



4
Zone 2B:

-
a swept stroke zone with high probability of arc hang on, such as the wing trailing edge aft of Zone 2A.




(3)
Effects on the aircraft structure and systems.

There are two types of possible risks to the aircraft:
-
indirect effects


-
direct effects.


(a)
Indirect effects.

1
Electromagnetic fields:

-
the electromagnetic fields related to the lightning attachment can cause unwanted transient voltages and currents in the aircraft wiring and systems.

In some conditions (low intensity strike, high protection), the effect on the systems can be temporary and the systems can operate correctly again after the strike.

In other conditions (low protection, no circuit protection devices), the damage can be permanent and it will be necessary to replace parts.




(b)
Direct effects

The direct effects are the physical damage related to signs such as:
1
Pitting/meltthrough:

-
this is the action of the electrical arc formed when a lightning stroke attaches to the aircraft (arc root damage at the attachment points or damage caused by current flow which can appear also far from the attachment points).


-
signs of a lightning attachment are pitting and scorch marks and paint discoloration.

On composite components, in addition to paint discoloration and skin puncturing, some delamination of the fibers can occur. If there is skin puncturing, there can be damage to the grounded equipment below composite material fairings.


-
you must always compare the damage you find with the limits given in the Structural Repair Manual (SRM).



2
Magnetic force:

-
the damage usually occurs where a small area causes the density of the current to be high (e.g. a bonding lead installed at a control surface hinge).



3
Resistive heating:

-
when lightning currents flow through an aircraft structure, energy is changed to heat along its path.


-
resistive heating usually causes marks of the weld type, specially where the lightning current flows for some time.



4
Acoustic shock wave:

-
When a lightning strike occurs, there is an acoustic shock wave. If the intensity of this shock wave is high, it can cause deformation of thin metal skins or rupture of thin composite skins.







I also looked at the loss of power supply to the Cabin Pressure controllers CPC 1 AND 2....they are both powered by the Essential Bus and Normal Bus......loss of power to Outflow Valves???? they should have stayed in their near closed position anyway( as it was in cruise)...

Sounds more like a severe lightening strike in a bad weather (as we all know)...... PANIC ATTACK in the cockpit.( WHY there was no distress call....I dont know) .......

and aircraft lost in severe turbulence....

I would like to add I am not a crash investigation expert but would like to solve this jigsaw with the help of other 330 guys out there!!!!!

[413X3]

"and it will be necessary to replace parts"... not an easy task at cruise attitude I imagine. Finding out what caused this to learn and make corrections in the future is something we all hope can be done asap

[IGh]

Still comments about high-level LIGHTNING, from slot #29:

"... a positive lightning strike?..."

In the decades of aircraft-LIGHTNING literature, can anyone find any case of LIGHTNING-strike to an airliner while at or above FL300????

[Ex-RoNiN]

Dunno about FL300, but Positive Lightning is not "normal" lightning:

NWS JetStream - The Positive and Negative Side of Lightning (http://www.srh.noaa.gov/jetstream/lightning/positive.htm)
NWS Hastings, NE (http://www.crh.noaa.gov/gid/Web_Stories/2004/other/lightningsafety/intro/introduction.php)


An average bolt of positive lightning carries a current of up to 300 kA (kiloamperes) (http://en.wikipedia.org/wiki/Ampere) (about ten times as much current as a bolt of negative lightning), transfers a charge of up to 300 coulombs (http://en.wikipedia.org/wiki/Coulomb), has a potential difference up to 1 gigavolt (http://en.wikipedia.org/wiki/Volt) (one billion volts), and lasts for hundreds of milliseconds, with a discharge energy of up to 300 GJ (gigajoules) (http://en.wikipedia.org/wiki/Joule) (a billion joules)

Could this much energy have the effects described in the ACARS even if it wasn't a direct hit but merely in close vicinity?

[Doors to Automatic]

Here's a good example of high level positive lightning striking well out of the CB into clear air.

YouTube - Sideways (http://www.youtube.com/watch?v=8HecqSYslG0)

[Hans Peter]

A review on all composite aircraft can be found at lonelyscientist.com (http://www.lonelyscient) that provides a free download of draft text for comment of a book on all composite aircraft with the appropriate title 'an impoosible dream'

[slowaero]

Carbon does conduct electricity. Automobile spark plug wire cores are carbon.

From the pictures of the tail I don't think it exploded.

Didn't Airbus have vertical stabilizer failures on its first planes?

[muduckace]

Although I am not a great Airbus fan.

They have gone to great lengths to ensure electrical/static bonding between composite structures and electrically conducive airframes.

I do though have doubts in our ability to perform preventative maintenance/inspections on composite structures that are load-bearing. Aluminum structures crack externally and are easy to inspect.

Composite materials degenerate internally and prove much more difficult to see from the eye requiring expensive equipment to perform detailed inspections on. In my opinion I have not seen a proper response to this issue going back to the A300 incident over long island and possibly the air France A330 currently in the Atlantic drink.

[davionics]

Meteorologists have a major problem. Sure they acknowledge that the Earth's atmosphere acts like a leaky, self-repairing capacitor (condenser). However, they assume that this spherical capacitor is charged from within by thunderstorm activity because they have been told that the Earth is an uncharged body flying through an uncharged solar wind. But it has never been shown to most just precisely how the thunderstorm charging process works. I'd like to mention discoveries of discharge phenomena above thunderstorms, stretching up into space.

Earth is a charged body that continually transfers massive amounts of charge to maintain equilibrium with the solar system electrical environment. Electrical storms are hence generated by a variance of conductivity in the dielectric insulating layers of atmosphere between the Earth's surface and the ionosphere. Leakage currents and potential differences can CAUSE vertical winds in a thunderstorm and the charge build-up in the cloud. Occasionally, a bolt of mega-lightning streaks from the top of a large storm instead of its base. This 10-kilometres-high short-circuit throws the switch for a further powerful discharge to the ionosphere. The result is a towering diffuse discharge at very high altitudes - a "red sprite" or "blue jet.".


http://www.holoscience.com/news/img/leakycondensor.jpg

http://www.holoscience.com/news/img/Sprites.jpg

http://www.youtube.com/watch?v=jF2gW2g5qKM
http://www.youtube.com/watch?v=jF2gW2g5qKM

[avconnection]

I thought I'd dredge this up, to look at high cruising decision making with regards to super cells. I've been watching a few local thunderstorms the last week or so and have noted a lot of upper atmosphere discharges (sprites and jets). One particular storm I was diverting around, from where I was sitting in the mid 20s I could clearly see several blue jets and sprites, and frequently during the presuppose of the storm. These discharges were usually accompanied by intense rapid, explosion like lightning from within the cell before releasing into the atmosphere. The lightning was continuous (not essentially continuous, there were multiple strikes per second) with positive strikes every 10-30 seconds. Now this storm would have been impossible for most jets to out climb as it capped out at around 55,000ft, but it got me thinking; how many pilots are actually over flying these types of storms, especially in light of recent evidence that suggests the gamma radiation released from these discharges have the potential to cause serious harm to health.

It's also not the sort of thing I get to see ever day and to me, this sort of activity is pretty rare (up until recently had only seen a few sprites throughout my career) how often are these witnessed by others?

[Dimitris]

'carbon' conducts electricity, but 'carbon' in planes is in reality 'carbon fiber reinforced plastic' i.e. the binding material is non conductive, the fibers are, in total its not good conductor. Look for 'CNT doped CFRP' for improved conductivity (still not compared to metals).
(mentioned somewhere above about carbon being conductive in spark plugs)

CFRP structures should have some short of metal mesh or whatever to form faraday cage and/or conduct electricity, this in fact takes some of the weight savings that CFRP create (B787). Also creates 'problems' in grounding ('problems' = they have solutions). Look for references.

A350 has metal structure on which CFRP panels get integrated on, may not need so much extra metal 'mesh'.

Military aircraft have higher % of composites (CFRPs, GFRPs etc) for 'ages'. Ever wondered why B goes from metal to plastic planes in one go while A does it in steps (by steps I don't mean the A350 being plastic on metal frame)