Lightning Strikes

[FormationFlyer]

A few questions regarding lightning strikes:

Are a/c (esp large pax transport) hit very often?
If a/c are hit by stikes how do they survive - where is the electricity routed?

If you are on the ground ready for departure/takeoff and are hit by lightning, how is the electricity dissapted? Is this expected? Do you continue or return to the ramp for checks?

Any insight into company SOP on this would be real useful.

[Checkboard]

Air carrier aircraft (in the US) are hit by lightning on the average of about once every 3000 hours.

It has been suggested that aircraft showing symptoms of static electricity (P static on the radio, or St Elmos fire) may be leaving an ionised wake, it is also possible that the jet exhaust leaves a similar wake, even if the aircraft isn't being charged by the environment. This wake acts as a charge path, so aircraft actually trigger lightning.

If an aircraft is hit, the electricity flows through the airframe, and exits on the other side (the airframe becomes part of the lightning's "circuit").

What can happen if an aircraft is hit? The worst is a fuel explosion. Jet A is by far the safest fuel to use, it will not normally form a combustible mixture in the tanks at the temperature at which a lighning strike is possible. There has never been a verified lightning caused fuel fire or explosion with an aircraft using Jet A.

Lightning caused fuel explosions have bought down a Pan Am 707 (Dec '63), an Iranian Air Force 747 (May '76), a US Air Force C-130E ('78) an F-4, F-16 and a KC-135, although all of these aircraft were at least partially filled with Jet B (JP-4).

The next worse thing that can happen is flame out (engine failure). Single flameouts due lightning strikes are fairly common on aircraft with aft mounted engines, dual flameouts have occured, although no accidents seem to have been recorded.

Small electric shocks have been reported by pilots, but nothing incapacitating.

Beyond this, various types of structural, avionics, electrical and magnatizing damage is possible. I have pictures of radomes blown apart, wing leading edges peeled back at the rivet line and such. This type of physical damage is usually cased by the sudden heat expansion of air due to arcing within an enclosed part of the aircraft structure, but is fairly rare.

If the aircraft suffers a lightning strike, a post lightning inspection is specified by the manufacturer in the maintenance manuals - which the engineers would carry out before the aircraft took off. In some cases, where the aircraft is at a remote port, an initial inspection can be carried out by the pilot, in order to certify the aircraft safe to fly to an engineering port for a full inspection.

Most of this information can be found in the excellent "Severe Weather Flying" by Dennis Newton.

Have a look here:
www.avweb.com/articles/lightnin.html (http://www.avweb.com/articles/lightnin.html)
for a story & pictures of a typical strike in a GA aircraft (an Aerostar).

If you need a (free) password, visit the avweb home page:
www.avweb.com/ (http://www.avweb.com/)

[This message has been edited by Checkboard (edited 29 May 1999).]

[IBTheseus]

What are all the black dot singe marks on the nose cone? My little Bae146's all seem to have them. I always thought they were from lightning strikes. But that would not fit your every 3000 hrs. I've only had a lightning strike in a Baron though.

[Ex Bus Driver]

The only lightning strike that I experienced during my 31 year career occured about 15 years ago when flying a B-727-100 from Raleigh-Durham, North Carolina to Greensboro, N.C. Early morning departure, climbing thru 3000'. The thunder clap was awesome! After assuring the pax that the aircraft was not damaged in any way, and admitting that it scared us as well, we proceeded to GSO. The required mx inspection revealed a thumb-sized hole in the metal strap that retains the position light on the top of the T-tail. BTW, the FAA mandates a "Lightning Strike Report".
EBD.

[Le Pen]

OK here are a few basics......
If an a/c is hit in the air the charge takes the route to static discharge wicks on the wing/fin/stab trailing edge and is dissapated there.

If you are on the ground and get struck apart from the route through the ground engineers headset/ears/brain/boots! the charge earths through the u/c...but, I hear you say the tyres are rubber and this should insulate the a/c. Good point, but, the tyres have graphite in the rubber which conducts the charge to earth.

In the US I understand that if there is an electrical storm all personel are to stay away from the a/c.....No such luck in europe where we just dodge the lightning!!

Love

Le Pen

PS Yeah sorry about that... I should have said it takes the most direct route out through the skin...Residual charge is lost through static wicks why else do we replace them so frequently if they are not used.

Even 777s are not immune...I had a 2 inch hole in the lwr fuse at ORY a while back.

[This message has been edited by Le Pen (edited 27 May 1999).]

[This message has been edited by Le Pen (edited 29 May 1999).]

[DEFPOTEC]

Le Pen, Starting rumours? Static discharge wicks are not lightning strike dissipators. They are not always capable of dissipating static electricity much less a lightning strike.

I have been in aircraft that were hit by lightning in flight. One strike left a hole in the top of the rudder big enough for me to put my hand through. There were also about 20 small, pin prick, holes in the wing tanks and most of the avionics were damaged.

I saw a Beechcraft get hit by lightning on the ground. All the lights came on for a few seconds. The lightning came out of the propeller blade closest to the ground and blew a small hole in the asphalt. I was only about 50 feet away from it at the time.

Yes, in the US ground personnel are supposed to stay away from the aircraft when there is lightning in the area. The southeastern states, especially Florida, get a lot of lightning. The spring and summer months are the worst. People are killed by it every year.

[mallard]

I have only had the kind of lightning strike which leaves holes or melts a bit of windshield, hail is generally more dangerous.
However, my wife used to be a flight attendant and, while strapped in for anticipated turbulence, watched something akin to a glowing ball glide slowly down the centre aisle.
Spooky or what?
I haven't heard of other similar occurrences but am familiar with the term "ball lightning".
Over the tropical Atlantic last year I saw for the first time a plume of static shoot momentarily forward from the radome like dragon's breath.
You do this job for so long and there is always something round the corner to amaze you.
Anyone else with interesting electrical encounters?

[Skycop]

A few years ago a mate of mine was captain of a Nimrod going westbound across the Atlantic. They suffered a lightning strike causing my mate to be temporarily blinded. A ball of lightning appeared in the cockpit, hovered between the two pilots and then gently floated gently backwards through the aircraft. It then suddenly accelerated and disappeared up inside the tail with a loud bang. Most systems seemed to work normally but they diverted as a precaution. On the ground all appeared normal but on closer inspection the next morning they discovered the top of the fin was gone, along with the MAD boom.

[Checkboard]

Interesting to hear. Most scientists doubt that "Ball Lightning" exists. Lightning is just electricity, and electricity is just a bunch of electrons going somewhere in a hurry - that is you need a circuit.

In this model "Ball" lightning is impossible, as no ciruit exists. Some scientists have attempted to produce glowing plasma in the lab using electrical effects but so far (to my knowledge) have been unsuccessful.

The other theory is a retinal after effect, similar to glancing at the sun (don't do this!)

[redsnail]

I used to live in Kununurra, a small town in the East Kimberley in Western Australia. In teh Wet season many thunderstorms occur. During one, I was closing a metal gate when I saw a brilliant flash and my hands were locked onto the wet gate. I was pulled violently on to the gate and I felt an incredible pulsing senstion through my arms. It was all over in an instant, and I ran inside. My hands looked like they had been scalded and my muscles in my arm, chest and upper back ached for a week. Yep, the bruises took a while to heal too. I believe the fence had been hit some way up the street and it was conducted to me. Ouch was all I could say at the time.. It was raining heavily and I was wearing rubber soled running shoes at the time.

------------------
reddo

[pterodactyl]

Lightning strikes were common during the piston and early turbine powered era when weather radar was not available. Weather radar was required to be fitted to all RPT turbine aircraft in Australia in 1963 as an aftermath of the breakup of a Vickers Viscount over Botany Bay the previous year.

Once airborne in weather there was no way of locating and avoiding storm cells and adverse weather encounters with turbulence,icing,lightning and/or hail were not uncommon.

Evidence of this can be seen on the DC3 aircraft still flying today which have numerous indentations about the windshields and on the fuselage in line with the propeller plane of rotation.

Hail was by far the greatest worry. Fortunately the slower speeds of the era enabled survival from these encounters as with turbulence as well.The same encounters at four times the speed of today's aircraft would result in impact forces sixteen times as severe.

Weather radar helps avoid all these risk factors including lightning. Nevertheless lightning strikes still occur even well away from storm cells and modern aircraft cope well with this.

Lightning can be from cloud to cloud, cloud to ground, or vice versa, I am told by some experts.In practice it matters not which way it goes. What is of interest is if an aircraft is in it's path.

My impression gained from quite a few in the piston era is that cloud....aircraft....cloud are not as severe as and aircraft becoming betwixt the cloud...
ground or vice versa event. We have all seen lightning travel across the sky for long distances in a bluish spidery pattern and it is not surprising that encounters with this type is difficult to avoid and is relatively common.In my experience although spectacular they are a far cry from the other kind.

Strikes between ground and cloud seem to have more zing in them and are much more spectacular.The kind of thick orange tinged strike which moves vertically between ground and cloud when it transits through an aircraft leave a lasting impression on the optic nerve (hence keep a low profile) and memory, as well as significant damage to some parts of the airframe,generally at the exit points. This kind of strike generally resides beneath and in close proximity to the storm cell. Generally weather radar enables avoidance of these areas and so this kind are less frequent.

The principle of the Faraday's Cage protects the occupants of a hollow container (the aluminium tube);that is, that the electric charge travels to the outside of such a vessel.

Modern aircraft cope well with strikes overall especially when you consider all the electrics,glass screens etc. Being struck in a gasoline fuelled aircraft is not appealing although there are very few mishaps attributed to ignition to fuel vapours. There is some evidence that some turbine aircraft were lost in this way as a result of using JP4 fuel. This type of fuel is no longer used by airlines to my knowledge.

Static discharge wicks are just that and dissipate the static charge built up by the friction of air moving over the surfaces during flight.

All the above is based on personal observation and I do not lay claim to expert knowledge on the matter.


ON THE GROUND STAY INDOORS WHEN LIGHTNING IS ABOUT!!

[Checkboard]

In the US, on average, one golfer a week is killed or injured by lightning.

Of the people struck by lightning, men makes up two thirds, women one third (probably because more of them play golf in silly conditions!)

Around the world, lightning strikes are estimated to be occurring at the rate of one hundred per second.

A lightning bolt can exceed one hundred million volts, and reach temperatures hotter than the surface of the sun.

[spannersatcx]

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

[Mycroft]

I remember seeing an item on a program about lightning concerning problems with a light a/c. A/c (either a single engined Piper or Cessna; pilot only; extra fuel tank) was crossing Atlantic west to east and was just over half way when was struck by lightning and lost complete electrical system - no long range radio; no navigation and even had to use hand fuel with fuel system. Luckily had short range radio (handheld?) and was able to contact another a/c on similar track which anebled him to reach land safely. Same prog also had segment about NASA/NACA trials with small jet a/c (poss T38) heavily instrumented/camera fitted and flown into storm clouds to see what happened.

[This message has been edited by Mycroft (edited 03 June 1999).]

[This message has been edited by Mycroft (edited 03 June 1999).]

[mallard]

I remember seeing a TV documentary about investigation into "ball lightning".
The scientists had deduced that it could not happen following normal laws of physics and, sure enough, they could not produce it in the lab.
However, your jet airplane up in the sky is not in quite the same situation as a ground based lab.
By definition it is not earthed (grounded) so who knows what an electrical discharge or accumulation of static may do.
Imagine what their reaction would have been if they had a dose of St Elmo's on the car windshield during the ride home.

[mallard]

I remember seeing a TV documentary about investigation into "ball lightning".
The scientists had deduced that it could not happen following normal laws of physics and, sure enough, they could not produce it in the lab.
However, your jet airplane up in the sky is not in quite the same situation as a ground based lab.
By definition it is not earthed (grounded) so who knows what an electrical discharge or accumulation of static may do.
Imagine what their reaction would have been if they had a dose of St Elmo's on the car windshield during the ride home.

[Slasher]

Getting struck by sparks is a weekly event here in monsoon country in the Wet. The books are full of AVOID! AVOID! AVOID! but in real life its only 60% of the time you can dodge and weave sucessfuly. The other 40% is having to plow through it regardless.
The 2 aircraft Ive been electrically hit in regularly are the 747 and 737. In the 747 its been the tailfin/wings/D1L. In the 737 its ALWAYS been just under my sliding window!
Lightning packs a huge voltage but buggerall amps. Thus airframe damage tends to be minor but noticeable. But this reassuring model went tits up one night enroute to Bangkok when a bolt struck my radome and blew half of it to bits!
But genarally I found lightning strikes affects radio com/nav equipment. The ADFs in both types may play up and a genny might get knocked off line. Almost always youve lost one HF set. You lose the VOR if the bolt strikes the antenna square on.
All strikes Ive encountered have always been below 30000 feet.
Lightning strikes should be reported on arrival and entered in the tech log.
---------------------------------------
Slasher. Lightning magnet.

[TerraDactyl]

At Canadian airports there is a thunderstorm alert (known as THOR) when there is lightning within a few km of the airport as registered by a special sensor. So during a T-storm and for 15 min after the last strike the ramp area is shutdown - no ramp operations and, of course, no refuelling. (Who would want to be sitting on 80,000 gal of jetfuel in a T-storm?). Airports are equipped with strobe lights on the passenger bridges which alert the ground crew to go indoors. It happens sometimes that you land with t-showers around, taxi to the gate and then sit 100m out waiting for the ground crew - frustrating after a long trip, but understandable for the ramp rats.

[Diver]

Approximately four years ago, lightening struck the Delta ramp building at KMCO which zapped the flap computers on a Delta 767 and a Leisure 767 whilst parked on there respective stands. The electomagnetic energy from a nearby electrical storm can be detrimental to the functionality of computers. Neither aircraft had been directly struck.

[ATC Watcher]

While overflying India at night at FL240 in a CL44 in the late 70,s, we found ourselves suddenly in the middle of a nasty Cb. Besides the rather bad turbulence we got hit by lightning : extremely loud bang, funny smell in the cockpit, both VORs gone, HF gone . Only 1 NDB still working. Diverting in Bombay (was called like this in those days) was elected not to be a good option under the circumstances, and we finally found Muscat on the other side with the help of daylight.
On the ground we found HF antenna physically missing and VOR antenna ripped off its mountings but still hanging there (Good cables)Frightening experience though...

[blackink]

Had a bad experience on lightning strike yesterday.
An engineer sitting in a tow tug haedset on his lap, a lightning hit a MD11. His leg was severely burned and he had to be taken to hospital.

[Diver]

June 8, 1999: NASA Science News

Learning how to diagnose bad flying weather-
Scientists discuss what they know about lightning's effects on Spacecraft and Aircraft.
Full story: http://science.nasa.gov/newhome/headlines/essd08Jun99_htm

[gaunty]

Took a strike one night (C402C, solo, single pilot IFR S.E. Aust) thru the Stbd engine prop boss, engine stopped never to run again. It went out the top of the vertical stabiliser blew the placcy fairing off as I discovered later. Total elctrical failure did get most of the systems back. In and out of cloud, no moon, no TS activity apparent on the radar or forecast.
Major damage to pilots seat cushion with several large washer sized holes discovered later.
Fair thought I had died and gone to hell.
Major Flash instantaneous Boom followed by darkness and chaos whilst trying to work out what had happened and if in fact I was still alive. So much for Joe Cool pilot.
Took a whole bottle of Scotlands finest to stop the shakes, mind you that's what causes them nowadays

Hey Redders aren't the NW TS awesome we used to sit out the back with a slab on days off just watching them build 50 to 60K was not uncommon. On the ground by lunch or you were lunch for the TS.

[WINDY7C]

Statistically, commercial aircraft average two lightning strikes per year per aircraft.

I count myself lucky, in that I have only been in two aircraft struck by lightning.

The first was a C-124 Globemaster, at 8000 ft. over the South American jungle, at night. I have no idea as to when we were hit, however there were lightning flashes and thunder close by for over an hour. On the lightning inspection at Recife, several holes were found in the top of the verical stabilizer and rudder. These were thought to be exit burns. No other damage was discovered.

The second time was on a DC-9. After departure, we were vectored around several cells. We saw lightning flashes and heard thunder close by. We didn't think we had been hit. However, at the gate one of the rampers came to the cockpit and informed us that the taxi lights were broken -- both of them. Closer inspection showed that lightning had burned a hole in the nose gear door, arced to the landing gear through the taxi light assembly. One light bulb was completely gone, the other had only the base and filiments dangling by the wires. That cost us a two hour delay waiting for parts and a mech. to install them.

Not very exciting, but that's the way I like it.

[This message has been edited by WINDY7C (edited 23 July 1999).]

[Duckwing6]

Slasher: True the 737 seems to always get hit just below the sliding window .. BUT that's just the tip of the (damage) ice-berg.. for all those that think just because they have weather radar Airliners don't get hit by lightning often.. we had a 737-400 getting hit 2 times in a week grounding the a/C for more than a day each (well that was really bad luck).. both times the first look just showed burn marks below the sliding window but a closer look revealed several burned through holes in the lower fuselage just aft of the forward cargo door farme going further back towards the tail fin .. the lighning finaly went out of the airplane taking the tail fin static discharger aswell as a 2 x 2 inch big pice of the tail fin end cap. But that's just the easy to see things .. if you have a look at an airplanes upper fuselage section (crown area) during C or D checks you'll notice a lot of strike hits that just go unseen ...

Phil (DW6)

[DrSyn]

There are two distinct types of strike, namely, a full-blown lighting strike and, more commonly, a static discharge. Fortunately, most of us usually experience the latter, powerful as they may seem. Wise use of WX radar, and MK1 eyeball, avoids most of the former. To save space, I'll refer to them as LS and SD (sorry!).

Aircraft flying through charged cloud (St Elmo's etc) often trigger a SD even though the cloud itself is not producing a lightning storm. The damage is usually restricted to small holes or burn marks on some part of the airframe. This is akin to Slasher's "buggerall amps".

A real LS is millions of volts AND 30,000-200,000 amps and can register its mark on your beloved airplane in a significant way. Checkboard's examples of known lightning fatalities are not alone, as there are many more where, in flying into a fully-developed CB, the question remained as to whether the lightning or the turbulence broke the airframe first. That is why the WX radar has major significance in most company MELs.

Without wishing to tempt fate, I have not suffered a LS in the past 30 years, but I have had many SDs whilst making my best efforts to avoid either. I did, however, watch a Continental 747 take a direct hit, a few years ago, from my perch on the Surrey Downs, overlooking LGW.

There was an active TS/Cb lurking NE of the field and, looking out of my lounge window, I saw the 747 brushing the base of it. A bright bolt came out of the cloud and struck the nose. The aircraft was simultaneously "haloed" in light and a series of forks came off the wingtips and tail, continuing to ground. The aircraft landed back at LGW with serious damage to its nose and was on the ground there for days afterwards. Anyone out there remember this one?

It's the amps that do the damage and, I suspect, most of us only experience Slasher's amperage, thank heavens! There is an old book called "The Flight of Thunderbolts", by BFJ Schonland, FRS., (1950, OUP), which makes fascinating reading for those who are interested (No ISBN, I'm afraid). Although recent storm-chasers and meteorologists have made great inroads into why, when and where storms occur, the physics of lightning in this book remain valid.

There is even an interesting section concerning aviation in Ch3 which mentions tests carried out by NACA (pre-NASA), little if any of which seems dated.

(If anyone knows of an ISBN website, by the way, could you post it here? Thanks!)

[leading edge]

About 4 years ago,a Bristow 332 Super Puma helicopter got struck while cruising over the North Sea. The charge exited the helicopter at the tail rotor blade and caused one of the tip weights to detatch itself. The tail rotor vibration pulled the tail gearbox off of its mounting and the aircraft ditched successfully in quite heavy seas. Everybody got out ok. Eurocopter, the UK CAA and the company have done a lot of work on lightening strikes since to try to reduce the risk of another ditching.

I had a strike once on the North Sea in the same type of helicopter. Didn't know anything about it until the engineers discovered a hole the size of my fist in a main rotor blade. The main blades are composite with a metal leading edge. Just thought you'd like to know...

[Q80Pilot]

About 1 year ago, in an a300, I was flying out of Beruit heading to Larnaca. I was the PF, my wife was also sitting in the cockpit during the T/O. CBs were scattered around the Airfield. On passing 3000' we got hit by lighting, it struck us right underneath my sliding window with a loud bang. The first thing we did was to check engine parameters and the Magnetic compass, both were ok. The rest of the flight was uneventfull (My wife thinks otherwise!)

About 2 months later, the exact same thing happened except this time it was at 4000'. What struck me as odd (pardon the pun) was that the lighting struck at the excact same place, just under my sliding window?

Any insight to this phenomenon?

[CaptainSandL]

My only lightning strike in 15 years of flying also hit us just beneath the sliding window. It left 5 burnt spots about 2cm in diameter along the paintwork. See photo at: http://www.chris.brady.ukgateway.net/lightning.htm
S & L

[Dodgy One]

Long ago, I was taught that the route of lightning was normally wingtip to wingtip or nose to tail. My first three strikes mystified me when I could find the entry point but not the exit. Turned out that it went nose to wingtip on all three (2 on Cessna 400 series and third on Bac1-11).
Have had many flying around the tropics in 747s of all types without major damage - a few welded rivets, holes in GRP panels etc.
Grounding is now so good that there is often little to tell. Certainly in the modern glass jets, a compass check is a bit superfluous since, with the excption of the standby compass, all magnetic displays are generated by computer from the true track data from the IRS.
Biggest gotcha can be if the radar stops working - could have blown your radome off. Happened to a VC10 out of east coast USA many years ago and he barely made Shannondue extra fuel burn. Check those fuel flows!

[Dick Scraddock]

For those of you who are interested the report into the "ball lightning" strike on an ASK 21 glider is on the U.K A.I.B web site (sorry I don`t have the address).
It makes quite concerning reading!

[Blacksheep]

Some pilots above seem to think that they have only been hit once in a career. Actually those are only the times that they knew about. It also says somewhere above that the average strike rate is once every 3000 flight hours. I don't know where this figure comes from but it is clearly incorrect. In several years experience of routine inspections at "A" check intervals (usually about 500 to 600 hours) I can vouch that you NEVER find an aircraft without lightning strike evidence. Typically there is at least one static discharger blown off with evidence of flash/heat on the remains of the base plate. Pointy bits of the aircraft especially the fin cap and the tips of antennae have melted bits which we blend out and touch up. Most radomes have pin prick holes in them that need sealing and touch up. Then there are the "stich marks" along the fuselage sides that no-one but engineers notice. This is a long series of pin point strike marks in a long line. Of course, only us "sparkies" go peering really close at the aircraft looking for this evidence but next time you do a walkround, try looking more closely at what look like pin prick black marks. Go on -- frighten yourselves :)



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Info noted. Plse report further.

[Expert]

Sorry to go off at a tangent but the following concerns severe wx:

Years ago in my 737-200 days we were within 100 miles of TOD when our single wx radar failed. It was daylight, the forecast & actual for our destination were not indicating any adverse wx, the vis was good and there was a solid layer of cloud below us stretching across the horizon with a smooth top at approx. 10.000'.

We contacted the radar controller at our destination and also spoke to aircraft that had just got airborne climbing towards us and enquired if there was any wx painting on anyone's radar. All responses were negative so we continued cautiously to our planned destination.

During the descent we entered the cloud layer at approx. 10.000' and due to the requirement for engine anti ice and 55%N1 (so long ago, is that the correct figure?) speedbrake was required to maintain an appropriate rate of descent. Shortly after entering the cloud we hit what we later discovered to be a rapidly developing Cb that had been totally obscured by the surrounding cloud. With full speebrake extended and an IAS of 280 kts our ROD became a ROC of 1500ft/min and the noise of the hail hitting the ac was so intense that we could not hear one another across the flight deck. I kept thinking that the eyebrow windows would give in and even though the encounter only lasted approx. 30 secs it was one of the most frightening experiences of my flying career.

Upon reaching the stand the engineer's jaw dropped in amazement. Inspection of the a/c revealed that 2/3 of the nosecone had been punctured, the top and bottom anti-collision light structures were missing, the wing root landing light housings were destroyed, all the leading edges were dimpled and the spoilers looked as though someone had taken a hammer to them.

Having reported the encounter to ATC, within minutes of landing we were informed that the met office had earlier issued a hail warning and dispatched an airman (doing his national service, it was a joint civil/military airfield) with the information to pass on to ATC, but he was distracted en-route and never passed it on!!

[billovitch]

Dr Syn, Must have been quite a sight, the Conti getting in the way of a cloud/ground strike.

Must take issue about the two types of strike however, as a lightning strike is nothing other than a large static discharge between opposingly charged objects.

As perceived by the public these would be clouds and Earth or whatever were attached to/standing on it. An aircraft may gain a relative charge quicker than the wicks can discharge it under certain circumstances.

I have had four full blown strikes over 35yrs in Europe, depite taking pains to avoid obvious cells. The bang and the flash were probably the worst thing about them. Two were preceded by the most intense Elmo's I have ever seen with a huge cone of "fire" extending from the aircraft nose.

In the RAF, a compass "swing" used to be mandatory after such an encounter, as they reckoned the magnetism of the structure would be changed.

[Blacksheep]

billovitch,

RAF Compass swings were much more accurately done than civilian swings. Military aircraft must be able to get about without reference to ground based aids. In a war situation your enemy is not likely to leave the VORs operating or provide ATC to help you find your way :)

Before INS most RAF aircraft carried a navigator and used doppler updated Ground Position Indicator Systems to track the aircraft's position. The Doppler needed really accurate compass data and it was not unusual to spend a whole day swinging the compasses to get them accurate within a quarter of a degree. So, a lightning strike would be quite capable of putting the compasses out of calibration. When I got rid of my Blue Serge Suit, I was a bit taken aback by the casual civilian approach to compass swings, but IRS has sent the things to the museum now. Standby compasses are mostly only accurate to the nearest 3 or 4 degrees these days.

**********************************
Through difficulties to the cinema

[Spotter]

I had a ride on the jumpseat on a flight last year and we were struck by lightning about 10nm from touchdown. About 2 weeks later I tried to use a digitally truned portable vhf receiver which had been in my hand baggage. It had been working earlier in the day of the lightning strike, but I was unable to tune any station afterwards. Would that be attributable to the lightning strike or just coincidence?

[DrSyn]

Yet another Tech Log thread that has suddenly been revived from the past. Someone must have been trawling!

The point I think I was trying to make, billovitch, was that there is a difference in intensity between a full-blown 30-200ka "bolt" that is self-initiating, and a static discharge that is simply triggered by the presence of one's aircraft. The former has been known to blow radomes or panels off planes, while the latter leaves small scorches or pin-holes.

I am not sure if any scientists have ever actually defined the boundary between the two, and would be the first to admit that it is probably the last thing on one's mind when there is a blinding flash and a deafening bang! However, I seem to remember that, in general, where there is otherwise no electric storm in progress it would normally be considered a static discharge.

Meanwhile, if you can obtain it, Schonland's book is a fascinating read.

[Self Loading Freight]

Spotter--

It's quite possible that the lightning strike broke your radio even without any direct contact, and it's more likely if you had the antenna plugged in at the time. Do the digital bits still work -- can you still enter frequencies and move around the band? If so, the problem's most likely to be in the circuitry that's directly connected to the antenna, and that might not be so expensive to fix. If nothing seems to be working, it may not be worth getting it repaired. Some of the modern scanning radios are nightmares to work on...

R

[Spotter]

Self Loading Freight - Yes the antenna was connected at the time. The digital stuff does still work, just can't get anything other than static no matter what frequency it's tuned to. (not even any different pattern of static no matter what freq. which i thought was strange.)

Anyway I'm not too bothered as it was getting on a bit & I've bought a replacement now. I was just curious really as it stopped working so abruptly. It took me about 6 months actually before I connected the two events.

[Hudson]

Blacksheep mentioned pin-prick holes in the radome. Interesting follow on to this observation. We had an on-going problem with a B737-200 which regularly flew in the West and Central Pacific area. Lots of moisture. As anyone knows who flies in that area, Cb and lightning abound. We had Bendix RDR-1E radar - if I remember correctly. Problem was that we could only get returns within 80 miles during cruise. Guam, a island around 60 miles long, could easily be picked up at 180 miles on our other 737's - but not this particular 737.
Cruising in cloud, Cb returns would loom up at 80 miles, first as tiny returns, then full blown serious stuff as we got within 30 miles. Made long range assessment of typhoon clouds a bit late. Below around 8000 ft on descent or climb, returns were normal.
Despite snagging the radar numerous times, techs in Hong Kong (our servicing base)could not fault the radar.
In desperation, I took a series of photos of the radar picture of Guam from 180 miles in the 737 with normal radar returns, and again with the 737 with the dodgy radar (ie 80 miles if we were lucky). I sent these to Bendix in USA with a request for ideas.
They said that in all probability, the radome was letting in water through pin-point holes in the radome. The water would eventually freeze inside the honeycomb and form an ice barrier. The radar beam then becomes attenuated and very little energy gets through. Hence poor range at high altitudes. In warmer temperatures, the ice melts and the radar works normally. Hence, ground checked - serviceable at Hong Kong.
Bendix said bake the radome to dry out the trapped moisture, then repair the radome.
No problem after that.

[justfun]

For those flying the type of gear that means you do the pre and post flight inspections, i.e little ones..if you find evidence of a strike (entry or exit) look a bit harder and see if you can find its mate. Rostered to fly one once that had had a lightning strike written up ,which had been cleared as OK to fly three days previously. Went looking further and found a 25mm x 2mm piece missing from trailing edge of 1 prop blade. Result, prop change required.
Also different a/c PT6 overhaul strip report, reported evidence of arcing internally. Message being, in sparky conditions/time of the year, make the DI a good one, like you always do.

[Dodgy One]

When Lee Trevino was asked what to do when caught out on the golf course in an electrical storm, he replied "Take out your 1 iron and hold it up to the sky."
When someone said that they thought that this might be a teeny bit dangerous, the Tex-Mex replied "Nope - even God can't hit a 1 iron!!"

[Holdfast]

the aaib report into a lightning strike on a glider can be found at:
http://www.open.gov.uk/aaib/dec99htm/bga3705.htm

As well as being interesting in its own right the investigator includes an extensive discussion of lighning mechanisms and effects.

[This message has been edited by Holdfast (edited 23 March 2000).]

[Diver]

This article appeared a few weeks ago in not one of our most respectable newspapers.


CONCORDE CONTROLS KNOCKED OUT


EXCLUSIVE

By Andrew Buckwell

Daily Mirror


A Concorde came within seconds of plunging to disaster after vital controls were knocked out by freak weather.


The British Airways supersonic jet was preparing to land at Heathrow when it was engulfed in static electricity for a split second it was revealed last night.

The rare storm condition – known as St Elmo’s Fire- crippled the auto-pilot the altimeter and equipment that stabilises the aircraft.


None of the 29 passengers on board was aware of the seriousness of the problem but the crew were left "badly shaken".

The captain, co-pilot and flight engineer were forced to use manual systems to regain control.


A senior Civil Aviation Authority source said yesterday: "It appears from the report filed by the plane’s captain that for over two minutes the Concorde had no main controls and anything could have happened".


The pilot’s report said the St Elmo’s Fire had the effect of lighting up the sky around the plane in a luminous green colour.


Seconds after the static "fireworks and crew managed to regain partial control and the plane was then given clearance to land immediately at Heathrow.


"If one main system fails there is always a back-up but for all major controls to be lost at the same time is a million to one chance", said the source.


"The most important control lost was the trim, which keeps the aircraft balanced.


"Without it any plane becomes like a lead weight about to fall out of the sky. The crew were badly shaken by this experience but decided not to inform the passengers so that everyone remained calm".


Concorde has been flying commercially for more than 24 years and the jets have been hit by St Elmo’s Fire phenomenon before but previous incidents have not been serious.


A British Airways spokeswoman said: " The aircraft experienced static electricity.

"The auto pilot did disengage but this is not an issue as the aircraft is designed to fly manually. It was flown manually and landed normally"


The Concorde hit trouble as it joined the stack of planes above a section of the M25 motorway at Ockham, Surrey……………..


LIGHTNING ‘DANCES THROUGH SCREEN’


Captain Eric Moody, who has flown British Airways planes for over 20 years, told last night how terrifying it could be to fly through St Elmo’s Fire.


Captain Moody experienced the phenomenon himself while he was flying in the Philippines 18 years ago.


He said "St Elmo’s Fire is a small electrical discharge that occurs when a plane passes through the water content of a cloud. It ‘s like a series of lightning flashes, dancing through the centre of the pilot’s windscreen. It is quite spectacular." He added "In cases of this Concorde incident, I’ve never heard of St Elmo’s Fire happening so close to the ground".


A Civil Aviation Authority spokesman said: "Thankfully the pilot was able to land the plane at Heathrow".

[con-pilot]

Back in the days of iron men and wooden jets I was flying a new (well it was new then) Jet Commander and took a lighting hit. I was at FL 330 over the Central U.S. during early spring. I was IMC and the radar (the old green cathode-ray tube style) showed two cells about twenty miles on either side of the airplane. There was a very bright flash and a very hard jolt of turbulence. The number 1 engine flamed out, all the A.C. powered flight instruments on the left (my) side failed. When the switch to power the left side from the right side was pushed all the A.C. instruments on the right side failed. Guess what, this was before the days of standby battery flight instruments. All I could do was bring the number 2 engine to idle, raise the spoilers, put the gear down and hang on for dear life. After what seemed like two or three hours we fell out of the storm around 10,000 ft not quite inverted, rolled level and limpted into KMEM and landed. Tried to restart the #1 engeine many times with no sucess, found out why after landing. The lighting hit the #1 engine in the intake, fried both the DC gen/starter, the AC gen, burned all the wiring from the engine to the # 1 converter regulator leaving an open circuit that shorted out the #2 converter reglator when we tried to transfer power. The airplane had to be ferried back to the factory and be rewired. Thrity years and 19,000hrs later that is still my only real lighting hit. I did see a Sabreliner (T-39) land with no radar dome due to a lighting hit. Rember you can still be at the wrong place at the wrong time when it comes to T-storms.

Took a lot of scotch to get a buzz that night.

[Cornish Jack]

Aaaaaaaaarrrrrrrrggggggghhhhhh!

I stopped buying English newspapers about 25 years ago because of unmitigated rubbish like this!! I'm not sure which is worse; a public who keeps this rag and all the others in business by paying for them or a system which can allow such uninformed wazzocks to peddle their wares.

As for misusing Eric Moody's quote...

...and this apallingly awful collection of, otherwise, unemployables have the gall to call themselves the Fourth Estate :mad: :mad:

That's another layer of enamel gone from the teeth - grind, grind!

[Leonard]

hi wats this about? :confused:

[reverserunlocked]

I was on the jumpseat of a VS 747 into Newark when we had a lightning strike. What surprised me most was the noise it made - it was just like one of those old fashioned bulb cameras - a kind of 'thwump' sound.

[eng1170]

Have seen lots of lightning burns, most small strikes seen to leave a small raised tag of skin material where its entered and left the airframe (usually on top and bottom of the fuselage, but did have an exit burn on the bottom skin of the wing recently). Metal wing tip nav light housings are also good exit points, leaving deformed/melted areas and crazed or cracked light lenses.

Any one got any tales of severe hail damage!! I worked a 737 not that long ago that had all 6 l/e slats peppered with hailstone damage but no evidence anywhere else on the airframe of hail. A friend told me of a severe storm that hit a Spanish airfield where Bae ATP's were being stored/maintained, and that some of the damage was so bad that upper fuselage skin panels had to be changed !

[False Capture]

Dont confuse "ball lightning" and the "glowing ball" following a lightning strike as they are two different phenomena. The "glowing ball" following a LS is simply ionised gas with little current ( ******all amps). I have heard of experienced cabin-crew jumping over it on it's way down the cabin (it usualy occurs at floor level) with little fear of an electric shock!
However, my favourite remains the old-boy I flew with many years ago who had a great theory about WX radar and reducing lightning strikes. He swore he had more lightning strikes with the radar turned on than he ever did with it turned off. He believed the radar sent out a leader which attracted the main stroke. As a result he said " You're better off turning the bloody thing off when there's a thunderstorm around " .....and I thought he was joking:ugh:
Finally, anyone else seen lightning being discarged vertical upwards from a Cb? I thought lightning either went Cloud-Cloud or Cloud-Ground, this bolt just disappeared going upwards.

[Mattuk]

There are two sorts of lightning which ascend vertically from clouds. Watched a program on it the other day...one sort called "jets" i think and dont remember the other one...maybe"sprites"?? dont know! They apparently reach thousands of feet into the atmosphere and there was something else about ozone gas i think. sorry to be so vague but guess it sorta answers the question!

[Loose rivets]

I've been interested in sprites since they were first observed, and one night phoned a physicist at the BBC who was there to answer questions about the phenomenon. I put it to him that there was enough energy in the core of a "bolt" to have a collapsing field energizing the gas/vapor stem in a manner similar to lasers. He said some word that sounded like rollocks, but after some argument, went sort of thoughtful but non-committal after I protested that there was such a surfeit of energy that the lens could be very primitive; made up of rain drops or ionized gas. There has to be some answer for these jets reaching the outer limits of the atmosphere. I have often wondered what it would be like to have one hit the belly of an aircraft....just when you were feeling smug about being way above the storm.

Sorry to be alarmist, but any assurance you may get from thinking there are no amps around in lightning, is unfounded. To do work you need power, the product of volts and amps. There is a lot known about the voltage sheer across a large bolt. The core can be only 4 inches across, with zero to multi thousands of volts per inch of radius typical. Where plasma is created...well, how hot is a welding arc?

I would guess, to get real current flow and do damage, the conducting path has to be optimized, that is, take the worst possible route, say cloud - aircraft - ground. In the worst possible scenario, there is no real reason why the aircraft should not be very seriously damaged; that sort of energy is certainly available. Thank God, the conditions are hardly ever met to do more than spray out of typical hot-spots, with minor burning.

As a young Viscount F/O I got such a thrashing one night (pre-radar days ) that I almost quit flying. Horizon bar off the dial, down below MSA over the Pyrenees, and so much hail noise that it drowned I/C and R/T totally. It just seemed to go on forever...but had a funny ending. After popping out into post frontal air somewhere near Toulouse, the skipper said he was shattered and asked me to fly. He put a cigaret in his mouth and held his Zippo up to his face before lighting it. The very instant he spun the wheel, there was the most horrendous bang and the aircraft shook violently. That was in the mid sixties, and I still have this clear image of his bulging eyes, beautifully illuminated by the little flame, staring over a crumpled cigaret.

There was a four inch hole in the wing, and the odd thing was that the energy went round the fuel bags and out through the bottom surface in line with the entry point. It seems that there is a very definite path laid out by the pre-curser charge line.

It seems that several people are convinced about lightning balls. I recall an incident on a Courtline BAC 1-11 circa 1970, very similar description. There was one guy in the UK who had a stack of submarine batteries and shorted them out for a second on a huge pendulous knife switch, in an attempt to replicate a ball. It looked very unconvincing. I think that they still remain a mystery.