What are those tips on the wings my friend asked/...and I f

[Victoroos 205]

HI all

 

I was flying while a friend of mine came in. He looked at the sim, was wowéd, but then asked : whata re those pointy things for at the wing..

 

I ready it, somewhere. but I don't remember.

 

Can anyone help?

 

Cheers

Vic

[in2tech 588]

2 minutes ago, Victoroos said:

HI all

 

I was flying while a friend of mine came in. He looked at the sim, was wowéd, but then asked : whata re those pointy things for at the wing..

 

I ready it, somewhere. but I don't remember.

Almost sure it is for lighting strikes on the aircraft?

[Farlis 2,299]

Those are the static dischargers.

https://en.wikipedia.org/wiki/Static_discharger

Edited June 5, 2021 by Farlis

[Andreas Stangenes 1,628]

They are static charge ports for discharge of static electricity. Ie when getting hit by lightning, flying in st elmos fire or otherwise when the airplane creates static electricity from air friction. They are part of the MEL (minimum equiptment list) and you cannot fly if any or a certain number of them are broken. 

Edited June 5, 2021 by Andreas Stangenes

[Moria15 950]

3 minutes ago, Victoroos said:

HI all

 

I was flying while a friend of mine came in. He looked at the sim, was wowéd, but then asked : whata re those pointy things for at the wing..

 

I ready it, somewhere. but I don't remember.

 

Can anyone help?

 

Cheers

Vic

Are you talkijng about the static dischargers?   the little thin cord like things?

 

They dissipate static electrical buildup caused by the friction of air flowing over the surface of the aircraft. The air friction tends to separate electrons from their atoms just as rubbing a balloon tends to do, causing an imbalance of electrical charge on a body. The wicks work by providing a pointed surface where airflow separates from contact with the aircraft body. The excess charge tends to flow into the air and is swept away from the aircraft.

 

Graham

[in2tech 588]

4 out of 5 Dentist agree, lighting or static discharge ports 🙂 Dang I am old to remember that commercial 🙂

[bobcat999 8,489]

The explanations here are generally correct.  More to do with the accumulation of static electricity due to the aircraft flying through the air than lightning really, as lightning will just strike and then jump off the airframe at any convenient point really, as the charge levels between static and lightning are vastly different as you would imagine.

They are also referred to as 'static wicks'.  In one of my previous jobs I worked with systems covering this type of protection.

It is surprising how much static electrical charge builds up on an airframe just by it 'rubbing' through the air.  This natural effect can vary due to moisture content in the air.

The large EH101 helicopter windscreens I helped to produce had to be covered with a transparent metallic film just a few atoms thick to discharge the static generated from the downwash of the rotors over the screen, and then was drained to a fly lead, otherwise, as the windscreens were isolated by various 'plastic / rubber materials' from the airframe, a massive charge would build up and zap the first poor engineer who tried to clean the windscreen after landing! 😄

There is so much we take for granted with aircraft systems.  I worked on bird impact, ice protection, anti nuclear flash, and radar defeating technology on something that just looks like a simple piece of glass that you look through.  Just the one half of the front windscreen on an EH101 helicopter would cost many tens of thousands of pounds. A lot of this is classified for military applications of course.

Those rainbow coloured patterns you see on aircraft windscreens arent due to cleaning chemicals as some people think, they are actually inside the layers of the windscreen and there for a reason.  They are also very thin metallic layers and will also drain static if needed. Their main purpose is anti ice heating though, and they are very powerful for what is basically transparent metal just a few Angstroms/atoms thick.

Edited June 5, 2021 by bobcat999

[Moria15 950]

1 minute ago, bobcat999 said:

The explanations here are generally correct.  More to do with the accumulation of static electricity due to the aircraft flying through the air than lightning really, as lightning will just strike and then jump off the airframe at any convenient point really.

They are also referred to as 'static wicks'.  In one of my previous jobs I worked with systems covering this type of protection.

It is surprising how much static electrical charge builds up on an airframe just by it 'rubbing' through the air.  This natural effect can vary due to moisture content in the air.

The large EH101 helicopter windscreens I helped to produce had to be covered with a transparent metallic film just a few atoms thick to discharge the static generated from the downward of the rotors over the screen, and the was drained to a fly lead, other wise, as the windscreens were isolated by various 'plastic / rubber materials' from the airframe, a massive charge would build up and zap the first poor engineer who tried to clean the windscreen after landing! 😄

There is so much we take for granted with aircraft systems.  I worked on bird impact, ice protection, anti nuclear flash, and radar defeating technology on something that just looks like a simple piece of glass that you look through.  Just the one half of the front windscreen on an EH101 helicopter would cost many tens of thousands of pounds. A lot of this is classified for military applications of course.

Those rainbow coloured patterns you see on aircraft windscreens arent due to cleaning chemicals as some people think, they are actually inside the layers of the windscreen and there for a reason.  They are also very thin metallic layers and will also drain static if needed. 

When in the Navy (Royal)  it was always interesting when a Heli came in to land on the deck of a ship to discharge it, but just as important, if it hovered and lowered people or a cargo, getting a crewman with a 15ft pole to discharge the cable from the heli before the cargo or people touched the deck..  if it was people and the cable was not earthed, you were probably going to severely injure or kill the people when they touched the deck 🙂

 

Graham

[jon b 2,050]

20 minutes ago, bobcat999 said:

They are also referred to as 'static wicks'.

A very interesting explanation, thanks.

I remember being  told to check the static wicks after a suspected lightning strike as some maybe missing after discharging the lightning to the atmosphere. Does that sound reasonable to you or nonsense?

This carbon fibre machine I’m on now apparently attracts lightning like a magnet.

[bobcat999 8,489]

13 minutes ago, Moria15 said:

When in the Navy (Royal)  it was always interesting when a Heli came in to land on the deck of a ship to discharge it, but just as important, if it hovered and lowered people or a cargo, getting a crewman with a 15ft pole to discharge the cable from the heli before the cargo or people touched the deck..  if it was people and the cable was not earthed, you were probably going to severely injure or kill the people when they touched the deck 🙂

Graham

That's right Graham.  it can be hundreds or thousands of volts that drain to earth during the discharge.  Enough to cause burns or nerve damage!

Some RN helicopters had a 'Harpoon' system under the fuselage when landing on a mesh grid on the deck of a Frigate.  I believe the purpose was two fold, to 'grab' the helicopter to the deck after touchdown, and of course, it would also discharge the static when doing this.

I spent plenty of days down at a sister company, Westland Helicopers in Yeovil.  I was amazed and learned so much everytime I visited.  They were good days!

[bobcat999 8,489]

29 minutes ago, jon b said:

A very interesting explanation, thanks.

I remember being  told to check the static wicks after a suspected lightning strike as some maybe missing after discharging the lightning to the atmosphere. Does that sound reasonable to you or nonsense?

This carbon fibre machine I’m on now apparently attracts lightning like a magnet.

Yes, entirely feasible.  Lightning will jump off anywhere it can really, it doesn't want to stay isolated on the aircraft as it wants to earth itself, so it will just pass through the aircraft on it's way, but it will always take the path of least resistance. 

If that path is through the static wicks, it will use it!  But they are really just used for discharging static.  Any powerful lightning strike passing through them could frazzle them or even blow them clean off in a worse case! 

I have seen holes in nose cones of older airliners due to a bad lightning strike.  Lightning protection is much better now of course; technology moves on.

Composites and carbon fibre type materials used in aircraft such as the Boeing 787 have to be specifically designed for this, as they do not discharge or carry the charge away very effectively, like a typical metal (normally Duralumin) fuselage.  Sometimes metal meshes are bonded into the composite materials for this reason, or they don't take a lightning hit too well!  Of course, this can have the side effect of 'attracting' lightning, which is probably what you have heard.

The philosophy is, it's better to have some metal to conduct the lightning though and out of the fuselage with low resistance, rather than have a high resistance material that would possibly be destroyed/blown apart by a high power strike.

There is some footage on youtube of (I think) an A320 getting struck just after take off    Actually, I just checked, there are loads of them!  The bolt is seen going in though the front of the aircraft and exiting at the rear.  Entirely normal. Normally the passengers would just see a dimming/flickering of the lights! 

Edited June 5, 2021 by bobcat999

[bobcat999 8,489]

Actually, as a side subject of this topic, a static electricity effect known as 'Saint Elmo's Fire' is one of the most interesting static electricity effects on an aircraft.  It is basically a lightning storm dancing around on your windscreen!   An amazing sight.

See here from about 2m25s into the video.

 

Also, in MSFS, static wicks are particularly well done on the Carenado Seneca. As you look out left or right from the cockpit, you can actually see the static wicks animated and jiggling about in the airflow - quite impressive!

Edited June 5, 2021 by bobcat999

[mazelda 124]

Just to add to all this,there are a minimum number that must be installed dependant on aircraft type otherwise the aircraft can be grounded. While they are known for discharging static they are also very important to the aircraft radio systems, probably more so infact.

While nothing to do with this thread exactly on some older aircraft types at the bottom of the main gear legs you would find a strap attatched that would touch the ground just before the aircraft landed that would help ground the aircraft on touchdown.

[jon b 2,050]

@bobcat999 Again, most interesting thanks.

Ive not had a strike  on the 787 yet, but  they mentioned during training it seems to attract lightning more other types for some reason.

Ive taken a few lightning strikes on other types over the years, and as you say mainly there have been no ill effects, occasionally it’d trip a FMC Resync or a bus would isolate.

The most hair raising thing I had was actually on the ground in Havana with an electrical storm approaching the airport. During the walk round I noticed the refueller had attached his bonding wire to some random possibly ineffectual part of the undercarriage and not the proper bonding mast which is on the gear door on the 747. I asked him if he could attach it correctly , and shortly afterwards as the storm approached when I was back in the flight deck I asked twice for the refuelling to be Stopped, for obvious reasons. I could tell they were completely ignoring me as you can see the pre fuel number indicated on the EICAS whenever the underwing refuelling panel is open.  Suddenly as I looked out I saw a fork of lightning hit the control tower a couple of hundred meters away followed a fraction of a second later by a second fork which hit the ground less than 100 meters off the left wing. Luckily we still didn’t have passengers on board Yet but I ordered all the crew to immediately get off the aircraft and go back into the terminal. The station manager started jumping up and down I remember as it was going to ruin his on time performance.

 

[Moria15 950]

29 minutes ago, bobcat999 said:

Actually, as a side subject of this topic, a static electricity effect known as 'Saint Elmo's Fire' is one of the most interesting static electricity effects on an aircraft.  It is basically a lightning storm dancing around on your windscreen!   An amazing sight.

See here from about 2m25s into the video.

 

Also, in MSFS, static wicks are particularly well done on the Carenado Seneca. As you look out left or right from the cockpit, you can actually see the static wicks animated and jiggling about in the airflow - quite impressive!

Not unique to aircraft...  heres a modern day picture of a sailing ship with St Elmos Fire on it....  Not as impressive, but still fascinating.  Have seen it running up and down the rigging as well sometimes 🙂

 

 

Graham

Edited June 5, 2021 by Moria15