LH3431 B737 lightning strike?

[ManaAdaSystem]

Local media reports of possible lightningstrike followed by fire in both (!) engines, severe turbulence and bits and pieces of the tail missing after landing.

Supposedly happened just after departure from Sofia, B 737.

[XPMorten]

Anyone have any info on this?

Can only find the norwegian article on it;
http://www.dagbladet.no/dinside/2008/04/06/531684.html

Quick summary;

Passenger tells story from last night over Sofia, Bulgaria
LH3431, B737 classic headed for Frankfurt.

Big flash, possibly lightning. Engine instantly on fire.
possibly both.
Aircraft started shaking, hysterical passengers, crying
flight attendance.

On the ground again, the pilot took a mobile photo of the tail
showing that a piece had fallen off and hanging down....

Cheers,

M

[FinalVectors]

Hi!

There is a story in norwegian paper "Dagbladet" today http://www.dagbladet.no/dinside/2008/04/06/531684.html about Lufthansa B737 having big problems after departure from Sofia yesterday.

Been searching for it on the net, but can't find anything else.

Fast translation of story the passenger is telling (a former SAS employee):

3-4 minutes after departure we got into clouds and did see a big flash, must have been lightning. I was sitting by the wing and did see the engine catch fire at once. According to a collegue on the other side, that engine was on fire too. Aircraft started shaking like I never experienced before, atleast one of the stewardesses was screaming and crying...................

....... After landing the captain said it was 1 in a billion chance this would happen, and the picture he did show mef rom his mobile taken on the runway revealed clearly that something had fallen of the tail and also something was hanging down.

-------------

Find it strange that I can't find anything else about this on the net.

Regards
Final vectors
Norway

[captplaystation]

Fire in both engines sounds like a fairly severe case of St Elmo's fire ( wholly possible in an active CB) if it really was both engines on fire I doubt anyone would be telling the story.
Could also of course be a surge caused by ingesting vast quantities of water.
In any case I don't dispute the seriousness of it, sure all will become public in due course.

[keltic]

Wowwww, I am not a pilot and thought that lightening was not a severe danger for a plane. I had myself a lightening strike (on the left wind where I was sitting). landing in VCE on a Iberworld A320. Just a bang, a bit of a shaking, reflection on the cabin ceiling, but continued landing with no problems, no turbulence.....

Sounds a terrifying scene indeed. :\

Just a question. Wouldn´t the weather screens or whatever they are called, have indicated that they were approaching a tricky area?.

[Patuta]

Some pictures (http://forum.bgspotters.net/viewtopic.php?p=33734#33734) in a Bulgarian spotter forum showing the damaged elevator. Might have been a lightning strike. Looks severe! Reg: D-ABXM (http://www.airfleets.net/show/81032), a 737-3.

[Roy Bouchier]

In response to Keltic - no, not necessarily. En route back from Mexico City once we were flying through what seemed to be soup, nothing showing on radar, when we had a lightning strike. Blew a hole in the radome and, according to the pax, they saw the fireball exiting by way of the starboard wing.

[boredcounter]

Would that be the exit point on the trim tab?

Are the pics of the type sent to the manufacturer to assess 'within limits?'

Cheers,

Bored

[HotDog]

A more than usual exit damage on the elevator trim tab. You wouldn't see any pictures of "engine fire" as there was no engine fire. It would have been coronal discharge called St.Elmo's fire. I have experienced a lightning strike on the nose in a thunderstorm which sent a ball of fire from beside the first officer's left knee, out of the cockpit, rolling down the aisle and exiting with a big bang in the tail cone. No serious damage though and nobody hurt except a few soiled undies.:E

[VNAV PATH]

Could have been engines stall due to massive hail ingestion.

[Roy Bouchier]

Highly unlikely to have any effect on the engines but it does tend to make you spill your coffee!

[steelfo]

I was a passenger on the plain. If anyone like to hear my story (and not from a journalist point of view...) just e-mail me at [email protected] . It was a pretty rough tour, and I haven't managed to get over it yet. The eninges was not at fire but some of us (not me) saw flames bursting out. If that was right after the lightning i am not sure...
The turbulence (lasted app. 5 min) was not normal turbulence but heavy "shaking". It was caused (told by the captain) by the loose part making heavy turbulence and a terrible sound. When the part was "thrown away" the turbulence stopped as sudden as it arrived. We turned around and landed a "normal" landing. The problem was that the captain didn't get any alarms and didn't know what caused the turbulence. We therefore made the landing with NO information. So..... we were safe when the plane stopped. So it was 15 (app.) terrible minutes. People crying (also the airattendent), praying to God, some turned on their phones to get a last call and goodbye.....
Once again if anyone are interested just e-mail me... I am not an expert but a passenger that got to speak to the captain...

[flying brain]

Steelfo

Would you consider it possible to share your experiences with the Forum members?

I believe that the professional comments of some members to such a post might help.

Hope you are recovering OK

FB

[Swedish Steve]

For those that don't know, the B737 has a trimable horizontal stabilisor and hydraulically actuated elevators. It also has a trim tab on each elevator. In normal hydraulic control this tab is locked and in line with the elevator. With no hydraulics in manual control, it is unlocked and works as a trim tab. The pictures show that the trim tab actuating rods and attachment on the trim tab is missing, so the trim tab would have been flapping. This would have ben the exit point for the lightning, wonder where the entry point was?

[steelfo]

Of course I am willing to share my experience. I have told the short story but right now I am having problems with flashbacks. The actual flying part is not the big problem but the flashback of the peoples reaction and panic and most of all my own thoughts and feeling are the worst. It gets better and better so i hope everything turns out good.
What really pisses me off is that i feel that Lufthansa is trying to "smothen" up the incident. Like they are trying to say that this was not that bad.... Well... I cant as a normal passanger tell how bad it was by seeing the pictures (that I know is the right ones because the captain showed us on his mobile phone). So... today we got an offical statement from Lufthansa that shortly tells:
"...hit by lightning shortly after take-off. The captain was handling this by the Lufthansa strict manual and called an emergency landing so that he could immidiately could go back to Sofia. Every captains is trained on this in a simulator. For you as passangers I have no doubt that this was seen as dramatic, but we have to say that there never was a danger for neither the passangers, the rest of the people on board or the aircraft. After landing it was obtained damages on the left hight-? and therefore the aircraft could not be in traffic before this was repared by technicians"

The problem is that the captain told us that he to was afraid, and this was nothing near what they had trained on in a simulator because this was to severe. He had no idea what caused the "shaking" and turbulence before he was on the ground.

So I have some questions:
1. What could have happened if not the part that was causing the shaking was thorn away? I have to say that it had to be very hard to control the aircraft in such a turbulence. How long could the aircraft stand such turbulence before it affected other parts/instruments?
2. How bad was it for you expert that has seen the pictures? Are they trying to make this better then it was? Or am I just to "close" the incident to see things clear?
3. How crusual are the part that was hit and how difficult is it to fly without it?
4. Shouldnt this be more official than it is?

Just some questions from me.

If you have any more questions about the incident dont hesitate to contact me.

Best regards
Steelfo

[hetfield]

http://img241.imageshack.us/img241/6993/bild2ew2.jpg


Hit by a missile.

All 3 hydraulic systems gone, so no steering anymore!

Landed successfully.
;)

[llondel]

Hetfield:

I assume that's the DHL Airbus at Baghdad?

[flying brain]

Many thanks steelfo for facing up to the 'memories' and sharing with us .

May I suggest that subsequent posts stick to the subject.

It is clear that professionals on the type out there can make a significant contribution to steelfo's recovery by helping him/her understand what happened and the level of real danger he/she was / was not in.

FB

[CityofFlight]

This is a classic time for the "Pros" of this forum to help someone who's obviously distressed over a harrowing experience.

Perhaps someone here can help explain that it wasn't as bad as it seemed for Steelfo?

[hetfield]

@llondel

Yes, unbelievable performance of the DHL-crew.

[hetfield]

ok

1. What could have happened if not the part that was causing the shaking was thorn away? I have to say that it had to be very hard to control the aircraft in such a turbulence. How long could the aircraft stand such turbulence before it affected other parts/instruments?

I'm not current on 737 but most airliners are certified for 0/+2.0 g with flaps extended. They can withstand more.

2. How bad was it for you expert that has seen the pictures? Are they trying to make this better then it was? Or am I just to "close" the incident to see things clear?

There is always a backup system in commercial airliners. If the elevator would fail completely, the aeroplane can be controlled by the trimmable horizontal stabiliser.

3. How crusual are the part that was hit and how difficult is it to fly without it?

See above.

4. Shouldnt this be more official than it is?

Didn't get this one.


:)

[ManaAdaSystem]

Look at the pictures, mate. This was no ordinary lightning strike.

[steelfo]

So... briefly one can say that this was no danger? :hmm:
Well... I can say that I have no problems if it wasnt and nothing would be more good than that. I just dont want LH to try to "smothen" things up if it was more bad...
I just can say that the 5 minutes with the shaking was terrible and i had plenty of time to think bad thoughts...
I am not sure if it helps to know that things really was under control or not. The 5 minutes I really felt that I should die. I dont think it is really possible for someone that has not been in a similiar situation to really know what its like. Well.... it gets better and better. I just think i need to speak to some professionals to prevent any after-damage ;)
Thank you for your replies and understanding.

[Bumpfoh]

In normal hydraulic control this tab is locked and in line with the elevator. With no hydraulics in manual control, it is unlocked and works as a trim tab.

I think you speak of the NG elevator tab system, this is a -300 (classic, I hate that term) and acts only as a balance tab.

The "trim" of the tab is mechanically set and fixed by the two burnt control rods you can see in the photos and is critical to longitudinal trim control in a loss of hydraulic power situation.:ok:

It's late and I'm on my third wine so apologies if not quite correct.

[The Bartender]

An interesting piece on similar incidents... (http://findarticles.com/p/articles/mi_m0UBT/is_42_20/ai_n16808920)

To quote from a TSB of Canada report (A95P0272 ) (http://www.tsb.gc.ca/en/reports/air/1995/a95p0272/a95p0272.asp?print_view=1) on a trim-tab induced flutter on a 737-200, in which a 24-inch section of the right elevator trim tab separated from the aircraft in flight: "The failure of the right trim tab did not endanger the aircraft from the standpoint of a loss of control; control surface flutter, however, can lead to further aircraft structural damage. The outboard section of the tab was attached to the elevator without any restriction to its movement, and it oscillated uncontrollably. This in turn caused the elevator to oscillate, which resulted in the severe airframe vibration felt by the crew."

[Starbear]

What should have happend:

All parts of the aeroplane structure should be bonded (connected) either via direct metal to metal contact at joints or via bonding jumper leads to connect moving parts such as tabs. This should allow any electrical current from a strike to travel through the structure, harmlessly, and find an exit path via the line of least resistance to one or more of the static wicks" at the a/c extremities; wing tips; ailerons; elevator and rudder etc. and discharge to atmosphere due to the potential differece.

I there is a breakdown or even complete abscence of this bonding for any reason then the current will attempt to jump this gap and arcing/burning can or will occur and can be severe in some cases causing physical damage.

In this case if the tab end is damaged and no longer aerodyamically clean then airflow breakdown will occur with ensuing vibration and possibly flutter as described earlier and perhaps being apparent through the whole airframe. Probably the vibration was such that the damaged portion eventually broke free allowing reasonably clean airflow once more.

Composite structures such as the tab and elevator in this case often have some metal embedded into them to assist with this very point. I confess to being fairly ignorant for now about this achieved on the very modern and very large composite structures.


New aeroplanes are at design stage subject to enormous electrical discharges to prove their viability and there are some amazing photos of this somewhere.

apologies to any granny readers.

[Collmac]

We were also passengers on the flight out of Sofia on Saturday evening and would like to tell how we experienced the events of that evening.

While still in the departure lounge we observed a line of cloud approaching - which appeared to be a front sufficiently active to be worthy of comment. When we were on the aircraft the rain had started and it increased as we taxied to the runway.

We were sitting in seats next to the over-wing exits on the starboard side. About 5 minutes after take off, in cloud, we were struck by lightning. I was reading but saw a flash of lightning from my right followed immediately by a loud bang and sparks or flashes across the upper wing surface. We did not witness any flames.

Immediately this happened there was vibration. This increased in severity in a stepped manner at about 4 minutes after the strike and again after a further minute. The vibration was severe enough to cause the cabin windows to be moving in and out approximately 10 – 12mms. It was frightening for all on board and particularly so for those with children.

The sensation and type of vibration in the aircraft, and the photographs published since, suggest that a similar situation has arisen as has been described by The Bartender. The inboard trim tab has been destroyed and disconnected from the control system. In this configuration any loose panel or debris will cause oscillation of the trim tab and set up violent vibration.

The plane was flown very gently back to Sofia, so much so that we were hardly aware we were descending until we broke cloud – and not at all aware we had completed a circuit. We truly thought we were landing straight ahead and wondered where that might be. It was a surprise to be back at Sofia.

At no point during this very unpleasant experience were there any announcements from either flight crew or cabin crew, although many people on board were obviously distraught. While we fully appreciate the pilots were likely to be occupied, we are surprised that the cabin crew did nothing to calm the situation since this is their job - and we completely understand the fears expressed by Steelfo. We were probably a little less inclined to panic than some on board because we have some knowledge of aircraft but we were still scared, so to suggest this experience was either exaggerated or the result of some ‘rogue activity’ is disingenuous.

The lack of information and communication was really appalling. Some people on the aircraft were approaching hysterical, others were tearful and yet more were quietly anxious but all would have welcomed – and expected – some explanation and reassurance.

We are also interested to discover from Steelfo that Lufthansa has issued a statement. It hasn’t reached us.

Collmac and Chris

[Green Guard]

Can anybody provide METARs and TAFs for that hour of departure in Sofia.

That may give more light on a "mistery"

[captplaystation]

Don't think there is any "mistery" (sic).
Took off into sh@t weather got hit by a bolt from Big G, knackered the tail due to Boeing inability to bond the A/C ( thought that was only an 800 prob, obviously not ) came back landed.
As stated by my fellow Jock, a reassuring P.A. might have been a good idea, but, I guess if tail was trying to shake itself loose they maybe needed some reassurance themselves.

[easy1]

It may be the cabin crews 'job' to calm and reasure but keep in mind they may never have had this happen to them before.
I am not saying you are wrong, and i know what i am talking about, have been through a similar situation, and i dont mind admitting that i was scared s:mad:less!!!

[The Bartender]

Can anybody provide METARs and TAFs for that hour of departure in Sofia.

20 minutes before, and 10 minutes after departure:

LBSF 051800Z 09001MPS 7000 -RA OVC036 08/06 Q1005 NOSIG
LBSF 051830Z 13002MPS 100V170 4500 RA OVC017 08/06 Q1005 NOSIG

[steelfo]

Hi Collmac and Chris.

Thank you for your description of the situation. It is good to hear another statement that this was an horrible experience. We were a group of 18 so of course it could have been the possibility to "scare" up each other, but as I read your story it is similar of what we experienced.

The statement from Lufthansa we got from the country manager of Norway. Probably and surely because the story ended up in one of Norways largest newspapers. It was a letter that didnt calm me, but just a very brief explanation of the incident. I was a little pissed because I felt it didnt say anything about what really happened. Thats why I seeked more information in among others this excellent forum.

Lufthansa did not at any time appologized either the lack of information on board or after. I surely understand the lack of time the pilots had and the fearfull experience of the other working on board. But if the captain had so much control and if the situation was not as bad as Lufthansa say I find it strange that we did not get more information.

Well anyway.... I now have much more information about this and how serious it was. Much thanks to this forum. So I feel calm about the physical situation. I am more concerned about the phsycical reaction the situation caused. Much of that could after my opinion been reduced by more information both on board and at least after.

Best regards
Steelfo

[VortexGen300]

Well thank you to all the information on the so-calles Bonding of all surfaces - there is no way to prevent damage caused by a direct strike of lightning on anything.

The damage may be limited by all sorts of precautions like bonding etc . . . .

However the only way to prevent damage is to stay away from CB's and other sources of imbalance in static electrical charge -

If there are indications of static on the stormscope go left or right to avoid - If you can't you are in grave danger - It becomes not if but when you are going to be struck - being a foreign object with a different electrical charge than the surrounds and lots of static activity.

So my opinion is the pilot took a calculated risk to take off with the weather as reported - but we all do as schedules require etc . . .

Maybe a better monitoring of the cockpit instruments (Radar & Stormscope) and alternative routing requested from ATC could have prevented the terrible experience.

This is one of the last issues that the aviation world have not really had an answer for - Lightning!

VG300

[Starbear]

Vortex Gen said:

there is no way to prevent damage caused by a direct strike of lightning on anything.
The damage may be limited by all sorts of precautions like bonding etc . . . .However the only way to prevent damage is to stay away from CB's and other sources of imbalance in static electrical charge -


Surely that is a very misleading not to say inaccurate posting and alarmist to boot.

Of course there is protection.

It is true that scientists and meteorology experts are still discovering new phenomena about such events. It doesn't seem all that long ago that it was discovered that lightning can and does strike upwards from cloud to aircraft.

But an enormous amount of work is done at the certification stage including placing a full size production aircraft into what is effectively a wire cage and then subjecting the aircraft to electical discharges of at least the same magnitude as measured or calculated from actual lightning. I have as alluded to earlier seen some excellent photos of this process at one of Boeing's facilities, I believe, and it would, I am sure allay lots of people's fears or misunderstanding to see such a picture or even better a video of this. Link anyone?

But nothing is perfect or remains perfect as the aeroplane gets older and goes through a variety of maintenance checks and suffers general wear and tera which may reduce some of this protection.

And isn't every lightning strike a "direct strike"?

[Jabawocky]

Starbear

Take note, not all lightning strikes are direct, some are strays, and let me just qualify something, most things in this world if hit by lightning are :mad:ed, wheteher it be a small hit or large hit.

Commercial airliners are one of the few things on the planet that survive most with little or no damage. Note the word "most" as in not all.

Bloody lucky that it was a modern B737 (even a classic is modern) compare to many other earlier a/c.

J

[keltic]

My sympathy for all the people who have experienced such an distressing event.

Will you fly again?. After my lightening strike, when I check there´s a storm in my route, I cancel my flight. It wasn´t such dramatic, but I do understand you quite well.

And of course I share your feelings. :D

[Collmac]

Thank you for asking.

Firstly we had to fly on the day following the incident, first to Frankfurt and then on to Edinburgh and, as fairly frequent flyers with our work as well as for pleasure, we really don't have much choice in the matter. However, we are both quite accepting of it being just one of those things and will have no trouble flying again.

Chris flew to London on Monday; I am off to the islands next week. Alternative transport is not convenient for us and cancellation is not usually an option but we'll not be losing sleep over it.

Collmac

[keltic]

Well done. I suppose this is like the lottery. One never gets the price again for the second time.

I am surprised at the lack of information given by the crew.

[BeeBopp]

Vortex-gen300 is not misleading or being alarmist, bonding is only a protective measure and the only way to be totally safe from lightning is total avoidance. It is not common but quite possible to see bonding leads and strips blown apart or off by severe lightning overload. When this happens the lightning will find another path. Composite structure often has copper mesh laid into the subsurface layers. If it does not the lightning will track through the water content of the composite and cause severe damage as it vapourises.

Certification tests on aircraft structure are with simulated lightning. I have considerable experience of dealing with real world results and can tell you that there is no such thing as a standard lightning strike. Every aircraft can expect to be struck a few or maybe several times a year depending where it is operated. The vast majority of strikes leave no damage apart from a tiny pitting mark where they enter and possibly some very minor burning at the exit point. The crew may well be unaware they have been struck in some cases and in most events even experienced engineers may have difficulty in finding the entry & exit points.

My point is lightning is like waves at sea, in the vast majority of cases no big deal but like the sea with rogue waves there are rogue bolts of lightning that will render all certification testing pointless. Aircraft undergo bonding testing during maintenance to ensure the integrity of the bonding path but in some very rare cases a lightning strike will overwhelm this and cause damage.

Anyway if I could reassure Steelfo by stating that every commercial aircraft flying has or will be struck by lightning at some point. It is [U]very[U] rare for that damage to be severe enough to loss of control or a crash. In fact I can think of only 1 case off the top of my head and this involved small commuter aircraft.

http://www.airdisaster.com/photos/ln-hta/photo.shtml

[ribt4t]

Not terribly exciting - I was flying back from LGW to MSP on a Northwest DC10 a couple of years ago (Mid April).

The approach to MSP was a little rough through low cloud. I was seated by the left wing and was looking out the window when the wing was struck near the tip. Other than being closer to a lightning strike that at any other time in my life it was basically uneventful - just a big spark and a loud bang.

Nobody said a word until we touched down then everybody was like "Did you see that !!!".

I couldn't even see a mark on the wing from where I was sitting.

[Starbear]

Bepopp

In what way is:
there is no way to prevent damage caused by a direct strike of lightning on anything.
etc

not erroneous or alarmist?

I repeat that there is protection and of course certification uses simulated lightning but it is nonetheless very intensive testing.

My point is quite simply that there is protection and I also added it is not perfect and yes it is vital to stay away from lightning but you can never guarantee to be clear even when avoiding the apparent sources.

You actually give a fair assesment but also alternate between the no protection argument but then say how often aircraft are struck with very minor results. The link to the accident a/c mentions it was struck by lightning just before landing; did the accident report actually blame that as the cause?

I speak from at least a point of interest if not apparent knowedge as I also am a LAME (and a pilot) and have been struck by lightning on more than one occasion (twice on one occasion, in an arrival holding pattern with very limited scope to avoid on that day) and yes it can be very frightening.

I have seen and am aware of some very significant damage occurring to a whole range of aircraft types, so I am certainly not suggesting that pilots can ignore lightning generating clouds simply because the aircraft is protected but it is wrong to say thay have no protection. Indeed many of the clouds producing lightning are the same as those that will produce significant turbulence (though not always) and pilots do or should strive very hard indeed to avoid those anyway.

[BEagle]

Lightning is not always predictable!

I was instructing a student pilot (he was in the LHS) in a VC10. In that aircraft the ancient weather radar is down by the LHS pilot's left knee and there is another display at the navigator's (yes, really!) station.

CBs had been predicted, but the weather radar showed only a few small returns about 15 miles away at 45 deg left.

Then we entered cloud in the descent - it had an unusual colouration and something made me suspicious. "Anything on the weather radar, nav?", I asked. "Nope"..... BANG!!

Lightning hit the AAR probe about a foot in front of the root end. The exit hole was later found on the radome; when the radome was removed, it had severe delamination.

So don't necessarily assume that the pilots took any 'risk' taking off in such conditions; more modern weather radars are vastly better than the orange porridge I used to work with - but when Big G decides to point the electric finger at you, it can come from seemingly nowhere!

[Collmac]

Are there any structures experts out there that would like to comment on our perception of the effect, rather than the cause, of this incident.

As we said before, the effect was severe vibration which caused the cabin sides to move in and out approx. 10-12mm (incidentally, I have moderated this from what I was saying when I first got off the aircraft to allow for the fear factor). I would guess the vibration frequency to be between 20Hz and 40Hz.

If we assume the cause to be flutter in the trim tab causing a vertical oscillating load at the horizontal stabiliser my interpretation of what we experienced is that the fuselage was actually ovalising where we sat in the overwing position. If this is the case would it be right to assume those to the front and rear of us experienced greater vibration, particularly vertically, than we did.

If this is the case my sypathies are with them.

[lomapaseo]

Are there any structures experts out there that would like to comment on our perception of the effect, rather than the cause, of this incident.

As we said before, the effect was severe vibration which caused the cabin sides to move in and out approx. 10-12mm (incidentally, I have moderated this from what I was saying when I first got off the aircraft to allow for the fear factor). I would guess the vibration frequency to be between 20Hz and 40Hz.


Some limited comments not necessarily conclusions about this event.

What the passenger sees and feels are vibratory modes in the soft non-structural cabin structures (between the cabin interior and the outside pressure vessel walls. This includes the interior window pane shields, as well as seat backs and tray tables. I had spent some time analyzing passenger videos of visible oscillations of interior fittings in somewhat similar events (to the passenger). The worst that I have seen is that the pretty looking panels in the loo fell off their attachments and made it difficult to open the door and take a pee

The aircraft structure (that holds the plane together) is quite resilient to forced vibration modes mostly due to dampening of the vibratory stresses across attachment points or joints not visible to the passenger. One might even see large amplitude oscilations in a surface albeit at low stresses.

The concern is always for an undamped oscillation like flutter outside the normal operating speed range. Also I would have some level of concern if the pilot was concerned that he could not control the level of felt vibration by controlling airspeed.

[VortexGen300]

Dear Starbear and others

Fortunately everyone is afforded the opportunity to express their opinion.

Please call me an alarmist - but please explain how bonding can "prevent" several thousand megavolt from damaging the intricate electronics of modern aircraft?

I have experience in the field of trying to protect electronic equipment from electrical surge such as lightning and other transient voltages.

Let me re-state : "Bonding (and earthing on the ground) does help to limit damage but the idea that it will protect? - I think that opinion is as alarming as my opinion as it might lead to people thinking they don't need to be as vigilant."

There is just too much we still have to learn - while a lot has been learned over the past century - we are still only seeing the tip of a humongous ice-berg floating accros the northern sea waiting to cripple and sink another Titanic.

So sorry for being an alarmist - but I'd rather be safe than sorry - and have to explain to investigators why something has occurred?

Greetings
VG300

[Starbear]

Ok Vortex you asked:

but please explain how bonding can "prevent" several thousand megavolt from damaging the intricate electronics of modern aircraft?


So I will have a go but this is definitely my last input because it seems pointless now. My original post was intended to give some comfort to passengers that even lightning strikes have been considered by the manufacturers and authorities AND pilots. You seem determined to suggest that an aeroplane cannot cope with a lightning strike at all. No, I know you didn't actually say that.

Here is the kicker, I suspect that you are probably a whole lot more knowledgeable than me on this topic but what I have said is correct. Aircraft are protected from the effects of lightning strikes but nothing is foolproof.

Here goes:

Bonding prevents damaging those intricate electronics by, providing a least resistance path for that megavolt strike to pass through the structure and exit to atmosphere And this CLEARLY works otherwise we would have numerous cases of serious damage to said electronics and the facts are that we don't (nope, don't have stats but any number of thousands of strikes versus examples of serious damage). Yes now and again there is rogue example of significant damage to tertiary structure and even primary flying controls such as an elevator (probably a result of poor or failed bonding) I am very aware of a very serious one in my own company.

And finally:
Nowhere has anyone and certainly not me suggested that:

"........ I think that opinion is as alarming as my opinion as it might lead to people thinking they don't need to be as vigilant."




out.

[cockney steve]

Not an A/c engineer, nor an Electronics one, but surely ,the big tin bird is fundamentally a jocking-great flying Faraday Cage....as such the charge will dissipate over the skin and leave the electronics untouched......I've never heard about queues of pax claiming a replacement for their frazzled watches, cellphones,i-pods and laptops....therefore I've a hunch that the A/c's heavily RF-shielded systems are extremely low vulnerability.

the flight concerned would appear to confirm.

I don't know enough about Plasma-balls (except you can make them in a microwave ,using half a grape :) ) but suspect that they don't present much threat , electronically....I wouldn't want to get in the way of one though!

[llondel]

The electronics attached to a properly-installed radio or TV mast is capable of withstanding a direct lightning strike, and the tower itself usually survives, albeit with an entry hole if there's a radome involved. So, correct bonding and proper electronics design and installation is going to keep most things working. The greatest danger on an aircraft is that the bonding along the preferred path proves inadequate and there's associated structural damage where the heating effect of the lightning has had an impact. The LH 737 demonstrated this by the damage to the parts at the rear where it was torn apart. The effect can be compounded if there's water in the path, given that the water will be turned to steam fairly quickly and so expand.

NASA did a whole series of tests deliberately flying aircraft into storm clouds to encourage lightning strikes so they could determine the effects. You get to see the benefits of that research today.

[RobboJon]

Interesting examination of what lightning will do to a composite aircraft in this AAIB investigation www.aaib.dft.gov.uk/cms_resources/dft_avsafety_pdf_500699.pdf of a lightning strike to a ASK-21 Glider from Dunstable. Interesting to note that a new CFI had reinforced the wearing of parachutes shortly before this incident.

Own experiences (both as SLF) include a strike in falling snow on final into Boston (Logan) in a BA 777. I was sitting in front of the wing next to the window and saw the reflection of the bolt striking the nose in the engine cowl. Apart from a loud popping noise, no other effect and a pleasant and informative explanation from the flight deck after landing.

By contrast, on an earlier flight departing the same airport in a fairly ancient BA 747 on a hot and hazy day at (I am guessing) 3-5,000ft a loud bang and a lurch to starboard (I wondered if an engine or the end of the starboard wing had departed) followed by about 15 seconds vibration and (apparently) laboured efforts to regain the climb. As I was seated in the middle of the cabin, I couldn't see what was going on at all. No announcements from the flight deck and - when pressed - the flight attendant informed me that the event had been caused by the air conditioning (at which point I decided he would not be my advisor of choice if any full blown emergency developed - or even if I wanted another gin & tonic). We flew to London with no explanation and there was considerable anxiety among the passengers - to the extent that on arrival at LHR the previously unknown to me lady on one side grasped my arm and said "made it". Seven hours or so of totally unnecessary tension that could have been resolved with a 10 second announcement. BA's attitude to its source of revenue did not endear the company to me that day!

My own inclination now is not to worry too much about lightning while traveling in the big silver birds - they seem robust enough to take most that is typically thrown at them (it's low on the list of potentially fatal risks compared with other - human and natural - ways of meeting your maker). Even the extreme LH experience that started this thread had a happy outcome, apart from an apparent disregard of the psychological well-being of its passengers that was reminiscent of my first BA lightning srike experience.

While flying around in the smaller stuff, steer well clear seems the only sensible maxim.

[BeeBopp]

RobboJon,

Thanks for posting the AAIB link on the Dunstable accident, very informative. Although the glider had no lightning protection and was destroyed the report interestingly determined by test and calculation that the lightning bolt was of a magnitude 8 to 9 times the level that which commercial aircraft and helicopters are built and tested to withstand. The 1995 Super Puma accident involved lightning intensity 3 times the certification standard. This is exactly what I was referring to when I previously mentioned rogue lightning bolts. I am not out to be alarmist but I frequently hear people discussing lightning strikes & going on about stringent certification standards, faraday cage blah, blah, etc. It is not that simple as the reports explains in great detail.

[PickyPerkins]

Photo of the damage here:
http://www.flightglobal.com/articles/2008/04/09/222837/pictures-dramatic-images-of-lufthansa-737-elevator-after-lightning-strike.html http://pickyperkins.home.infionline.net/pi.gif

[Basil Seal]

BeeBopp,

Without having even Googled it to find out but asking nonetheless, was there not an Iranian 747 on approach into Madrid quite a few years ago that came to grief and a lightning strike was suspected?

Unfortunately I cannot remember any of the details or even how a "routine" strike would have led to a loss of the airframe, but something about this makes me wonder. Did it even happen? Was it in Madrid? Was it Iran Air that was involved?

[lomapaseo]

Without having even Googled it to find out but asking nonetheless, was there not an Iranian 747 on approach into Madrid quite a few years ago that came to grief and a lightning strike was suspected?

Unfortunately I cannot remember any of the details or even how a "routine" strike would have led to a loss of the airframe, but something about this makes me wonder. Did it even happen? Was it in Madrid? Was it Iran Air that was involved

I believe that it was the TWA800 sister ship in the production line.

Operated by the Iranian AF

believed to have ignited the fuel in the wing due to poor static wicking. I suspect that IGH will produce a cut and paste of all the pertinent details when he discovers this post :)

[doncas]

I have extensive experience with lightning strikes on aircraft and I can safely say that lightning strikes on aircraft are very common. Lightning damage can vary from very mild (no damage) to very severe (as we have seen). Lightning strikes are so common in fact that there are entire chapters in aircraft Structural Repair Manuals to deal with each incident.
Typical lightning strike damage looks like a small burn mark or crater on the aircraft skin or on a rivet.

There are obviously limits to the size and dimension of the damage that is outlined in the SRM and these are strictly adhered to when inspecting an aircraft for lightning strikes. If there is a scorch, this material is generally blended out, inspected for cracks and then reprotected. If there is a crater, the damage is drilled out and a fastener is installed as a permanent repair. Very often one can see the extremities of an aircraft such as wingtips / winglets, trailing edges, static wicks and any other 'sharp' point of the aircraft most affected by 'exit points'. Protection from these exit points usually come in the form of the aforementioned static wicks. They are made of a high reistance material >10 MOhms. This allows for a gentle 'leaking' of static electricity from the aircraft and lightning strikes. In unusually high energy bursts of lightning these can be effectively blown off.

Getting around to our subject aircraft... The area that was blown off is a composite structure. It has no static wicks on it as they are fitted more outboard. It is possible that this lightning bolt was particularly powerful. This would have caused such a surge of electricity to pass through the composite structure that it heats rapidly and is liberated, as you can see.

Hope this answers some general questions, however if anyone has specific questions, please feel free to ask away and I'll help as much as possible.

[Basil Seal]

Thanks Lomapaseo, I am relieved to know that I was not imagining things! I think there was another 747 that crashed going into Madrid on a non-precision approach a number of years ago and I wanted to make sure that I was not confusing the two.

Doncas,

Something that I should know, but have alway been perplexed about, how great is the difference in damage susceptibility between the aircraft in the air (non-grounded) and being on terra firma such as in having the back stairs of the 727 touching the ramp (e.g., not just on the ground on the rubber tyres but an actual touch point). Have there been reports of severe aircraft damage from strikes whilst on the ramp? In my years I have not heard of any, but since you repair them you may well know.

[cjam]

Info for Steelfo, not sure if it is relevant but it sounds like the more info you're getting the better you feel about flying.
I fly the 737-300.
Pilots do practice different scenarios in simulators.
At my airline we have two four hour simulator sessions each six months. Two months ago I did one that focused on flight control problems. We departed and at about 10,000feet the airlerons jammed. The ailerons are a very important flight control that roll the aircraft in order to turn. We could control the aircraft through limited use of the spoilers and mainly by using rudder and landed with no problem. Then we did another flight where the horizontal stabilzer jammed, this makes it a bit tricky to make the nose go up and down but like the ailerons, there are built in systems that allow us to control the aircraft and get it back on the ground, albeit with a bit of sweat on the brow.
One thing that happens in situations like this is that you become quite busy re-organising the flight deck ,and the instruments, and your own brain (which checklists have been done? which need doing? what have we forgotten?)for a completely new plan with new problems and things to consider. In both these cases we made PA's to the passengers but these cases were not the same as your situation. For a start we were in a simulator, and secondly we had no major vibrations. My opinion is that.... If the pilots didn't know what sort of damage they had, and suspected severe structural damage as indicated by the vibration, they may have concluded (and fair enough too) that there was a real possibility of structural damage and further control difficulties and that landing the aircraft as soon as possible was the highest priority. That being the case they may well have been completely occupied with the tasks of flying the aircraft back to the field for landing. I wasn't there and don't know how much time elapsed but I can imagine this happening.
If that was the case then it is unfortunate for the passengers not to get the info they craved at the time but it is neccessary to prioritise your attention to what is most important when doing the job of flying.
Many pilots use a saying to remind themselves of the order of things, the saying is "aviate, navigate, communicate" as you can see, communicate comes third on the list of things to do and will only get done after both the aviating (flying the aircraft)and the navigating (are we clear of the ground ? heading to the right runway?) have been completed. And even then, communicating with the passengers is secondary to communicating with air traffic control and the cabin crew.
I hope this helps you feel better about the flight, there is every possibility that the crew did a fantastic job under the circumstances and that focusing on flying the aircraft to the landing was the most responsible and professional thing to do.
Cheers, cjam

[DC2 slf]

<quote><snip>
Anyway if I could reassure Steelfo by stating that every commercial aircraft flying has or will be struck by lightning at some point. It is very rare for that damage to be severe enough to loss of control or a crash. In fact I can think of only 1 case off the top of my head and this involved small commuter aircraft. <snip><close quote>

I believe that in the early days of the B707 a crash of a PAA flight in Maryland was blamed on a lightning strike.

[Robert Campbell]

In over 40 years of flying, I've been struck 4 times by lightning -- once in a Beech D-18 and 3 times in DC-3s.

The only problem I ran into was that the D-18 strike fried ALL of the electronics, and this was because the operator of this 1970s commuter airline decided to run all of the electrical circuits through one big 75 Amp fuse (well, why run a bunch of little fuses or breakers when one BIG mother will do?).

The 3 strikes to the DC-3s left nothing more than small entry and exit holes.

In the 1990s I was involved with a company that produced promotional videos for kitplane manufacturers. I shot the air to air video.

When we were working with Glasair in Arlington, Washington State, USA, I asked about lightening strikes and was told that a strike would cause a composite aircraft to explode, so they ran wires in the resin layers to conduct the current.

They were also experimenting with a wire mesh layer embedded into the composite to carry the charge through the structure more effectively.

I know that they were doing contract work for Boeing at the time and some of that work was lightning strike related.

[Pegasus77]

Steelfo:

Aerodynamic vibrations can seem very severe in the cabin, but as Lomopaseo stated, the aircraft is built to cope with them and is still very well able to fly. A small piece of the elevator missing, like in this case, causes no big problem(just look at the photo of the missile-hit Bagdad-DHL-aircraft; even they were able to land safely).
This amount of damage after a lightning strike is huge, but still relatively harmless; I've been struck with lightning (that is: the aircraft I flew in) a few times, sometimes nothing happend, once we found 2 small black burn spots.

I do however understand how you must have felt; it is too bad that there was no PA-announcement from the cockpit. A standardletter from the LH-PR-department does not make you feel better, that is for sure. My guess is that the cockpitcrew had to set priorities. Flying the aircraft with structural damage is a priority. I hope you're able to believe me and my fellow pilots here on this forum that the actual danger on this flight was very very low.

Don't worry about any flashbacks or other symptoms of stress; they're perfectly normal if you were in a situation of great fear. Relax, take your time to recover, and book your next holiday by air :-) !


One last remark for the spotters & people who always readily pull out/google the latest METAR from the time of any incident: get a real hobby. It is soooo non-interesting to know what registration this or that aircraft has (besides, a REALLY COOL airman would describe a 737-300 as B733 and not as a 737-3, it only shows you're not part of our little world). "FEW CB" is something one reads sooooo often, and has soooo little meaning. A lighting strike can also come from clouds which don't even yet count as CBs. And a CB is not automatically a raging thunderstorm that burns trees and houses down.

P77

[CityofFlight]

Well said....I was hoping to see a response like this from someone who can talk the talk--including that weather doesn's have to be ominous in order to produce lightning.

I hope this helps Steelfo and any other SLF's who may need some reassurance after reading this thread. :D

CoF

[Knife-Edge]

The video of the Nippon 747 getting struck on climb out has no doubt been seen by most.... but how about this strike on a Qantas 767:

http://www.youtube.com/watch?v=036hpBvjoQw

[Robert Campbell]

In my post above, I referred to a strike in a Beech D-18. This happened in the
San Joachin Valley in California around 2:30AM local on a mail flight. The air was very clear under a few scattered clouds. There was no rain or turbulence. We could see lightning in the distance. It was what we in California call dry lightning.

Suddenly there was a blinding flash and then nothing electrical worked. It took a good 2 -3 minutes to get our night vision back. We were near our destination of Fresno. The tower was closed for the night so we just landed, offloaded the mail and slept until we could find someone to fix the machine.

[llondel]

Rain is often quite electrically charged. I noticed this several years ago when I had a long wire antenna strung down the garden. It was raining and I could hear an irregular 'tick....tick' It turned out to be the antenna sparking across the metal plates of a tuning capacitor to ground. What's more, it can change polarity, as I discovered when I connected a neon bulb between the antenna and ground - at the start of the shower one electrode was glowing, by the end, the other one was. I guess it's not beyond the bounds of probability that an aircraft could collect a significant charge and then fly into a cloud of opposite polarity. Whether it would quietly discharge or whether you'd get a sudden lightning type discharge I don't know. It may be that the dissipaters on the trailing edges would stop it ever getting to that stage.

The action of the leading edges slicing through the air can knock electrons off of atoms to create ions (in the same way that it happens with the water molecules), so if there's enough potential around, the mere passage of an aircraft can actually cause lightning even if otherwise it might not have happened. There was a North Sea helicopter that took a strike to the tail rotor (and subsequently ditched) that was attributed to this mechanism.

[cwatters]

> All the fibres of the shaggy garment were sticking out - standing on end.
> Something to do with the raindrops making contact with me. I was in
> Wellys, so I would have been insulated from the ground.

Not too hard to explain. The -ve electric charge on the underside of the cloud causes +ve charge to accumulate in the ground and on objects under the cloud (eg your head). This is because opposite charges attract and alike repel. Your feet would have been -ve if insulated from the ground. These +ve charges are attracted to the cloud and repelled by each other causing hair and fiber to be pulled up and out.

http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/estatics/u8l4e1.gif

There are several demos on Youtube using a Van de Graaf generator to produce the high voltages needed...

http://www.youtube.com/watch?v=2rSYcKtBxZw&feature=related
http://www.youtube.com/watch?v=46tjusrl6Yw&feature=related
One with an explanation..
http://www.youtube.com/watch?v=Ah2DuXGzGGc

[lomapaseo]

I picked this off another forum today


http://fromtheflightdeck.com/Al/HighPowerWorker.wmv

[DonLeslie]

The "aviate, navigate, communicate" principle has already been mentioned and one might add that Sofia is surrounded by high hills with a 7500 ft peak immediately south of the field. I've been there many times and remember this airport as extremely terrain critical; you really want to know what you're doing even under the best of conditions.

I'd hate to be in that basin with thunderstorms all over the place and an airplane "trying to shake its tail loose", as somebody put it. I imagine stress levels skyrocketed for the crew and they were extremely busy with the "aviate" and "navigate" parts. Add to that an ATC environment with lots of room for improvement, and you get a situation where they probably did not have any capacity left to tell the passengers what was going on.

Anyway, they did a great job in putting it down safely and deserve to be saluted for it. :ok:

[steelfo]

Tnx again for all great answers. It was a very good "recovery" for me first to get all the physical "evidence" . I now know extremly much more of what happened, why and what could happen. I surely understand the situation the pilots was in and I never thought that they didnt do the best. We met the pilot at the hotel and I am sure that if he had the time he would have communicated better. All honours to them getting the plain down as safely and smooth as it went.
As for the phsycical situation I am now feeling much better. The worst was the thoughts af the panic situation and the thoughts that went through my head about my family. We had a debriefing at our company that helped a lot, and I know can say that I am 99,9 % recovered :)
Actually I am travelling to Vienna on thursday, and it is difficult to go there with another transport than a plane... :)
I guess that I probably will be a bit more tenced, but I think I will have no problems flying again.
Again....a lot of thanks for all the answers :D