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Lightening Diverter Strips  
User currently offlineHAWK21M From India, joined Jan 2001, 31712 posts, RR: 56
Posted (9 years 10 months 2 weeks 4 days 21 hours ago) and read 7439 times:


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Do other Aircraft have Lightening diverter strips similiar to the B737.
regds
MEL


Think of the brighter side!
27 replies: All unread, showing first 25:
 
User currently offlineJetstar From United States of America, joined May 2003, 1665 posts, RR: 10
Reply 1, posted (9 years 10 months 2 weeks 4 days 16 hours ago) and read 7330 times:
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Because fiberglass is an insulator, not a conductor all fiberglass radar domes have metal diverter strips to form a path for the electrical current to flow into the metal frame of the radar dome and then into the airframe in case of a lightening strike to the radar dome. Some of these metal strips are more readily visible on some aircraft than others.

On the JetStar, they were molded directly into the radar dome and hardly visible unless you were real close to the radar dome. But to repair or replace them required the radar dome be removed and unless you had a spare radar dome the airplane was out of service until the repair was finished.

On this photo of the 737, it appears the metal diverter strips are on the surface and can be replaced or repaired very easily without removing the radar dome.


User currently offlineTroubleshooter From Germany, joined Feb 2005, 423 posts, RR: 4
Reply 2, posted (9 years 10 months 2 weeks 4 days 16 hours ago) and read 7320 times:

The ERJs use the same system. The stripes are bolted to the outer radome surface. I think this is the most common type of installation.


This job sucks!!! I love this job!!!
User currently offlineHAWK21M From India, joined Jan 2001, 31712 posts, RR: 56
Reply 3, posted (9 years 10 months 2 weeks 3 days 23 hours ago) and read 7269 times:

How frequent are they replaced on the B737.I've never seen one done for over 13 yrs now.
regds
MEL



Think of the brighter side!
User currently offlineTbanger From Australia, joined Jul 2004, 266 posts, RR: 0
Reply 4, posted (9 years 10 months 2 weeks 3 days 22 hours ago) and read 7264 times:

How frequent are they replaced on the B737.I've never seen one done for over 13 yrs now.

When they fail there resistance check I guess. If power wont flow through them, then they change them.




User currently offlineHAWK21M From India, joined Jan 2001, 31712 posts, RR: 56
Reply 5, posted (9 years 10 months 2 weeks 3 days 14 hours ago) and read 7238 times:


Quoting Tbanger (reply 4):
When they fail there resistance check I guess. If power wont flow through them, then they change


That would need a Severe Lightening strike to have occured  Smile
regds
MEL



Think of the brighter side!
User currently offlineAirplay From , joined Dec 1969, posts, RR:
Reply 6, posted (9 years 10 months 2 weeks 3 days 7 hours ago) and read 7210 times:

How frequent are they replaced on the B737.I've never seen one done for over 13 yrs now.

Lightning diverter strips are typically subject to periodic visual inspection. The strips are usually comprised of a row of segments of diamond shaped or slot shaped conducting surfaces.

A common inspection criteria calls for replacement if any 2 adjacent segments are missing or if a certain amount are missing in total.

The replacement is normally specialized maintenance that is done by an authorized facility, normally a radome repair facility. Even if you've never seen diverter strips replaced in 13 years, chances are quite probable that the radome has been replaced or repaired at which time the diverter strips were either maintained or replaced.

Because fiberglass is an insulator, not a conductor all fiberglass radar domes have metal diverter strips to form a path for the electrical current to flow into the metal frame of the radar dome and then into the airframe in case of a lightening strike to the radar dome. Some of these metal strips are more readily visible on some aircraft than others.

Just like anything in the unpredictable world of airplanes...there are exceptions. A great many smaller aircraft that use fibreglass radomes are not fitted with lighting diverter strips.


User currently offlineHAWK21M From India, joined Jan 2001, 31712 posts, RR: 56
Reply 7, posted (9 years 10 months 2 weeks 2 days 19 hours ago) and read 7178 times:


Quoting Airplay (reply 6):
Even if you've never seen diverter strips replaced in 13 years, chances are quite probable that the radome has been replaced or repaired at which time the diverter strips were either maintained or replaced.


Something which I suspected too.  Smile Thanks.
regds
MEL



Think of the brighter side!
User currently offlineCRJ200Mechanic From United States of America, joined Feb 2005, 204 posts, RR: 2
Reply 8, posted (9 years 10 months 2 weeks 1 day 21 hours ago) and read 7150 times:

Quoting HAWK21M (reply 3):
How frequent are they replaced on the B737.I've never seen one done for over 13 yrs now.


The strips on the CRJ are the same as they are on the ERJ. I have to inspect them every night at my job. We only replace them when parts of the strip are missing. Segments tend to separate during a lighting strike (which it should). We they have to be replaced it's generally easier to replace the entire radome. The CRJ's are glued down and a pain in the rear to remove. I don't know how it is done on other aircraft



Always remember the responsibilies you hold with an A&P license
User currently offlineHAWK21M From India, joined Jan 2001, 31712 posts, RR: 56
Reply 9, posted (9 years 10 months 2 weeks 1 day 15 hours ago) and read 7139 times:

Quoting CRJ200Mechanic (reply 8):
The CRJ's are glued down and a pain in the rear to remove.

You mean The strips are glued down in addition to Hardware,or only Glued down.
regds
MEL



Think of the brighter side!
User currently offlineCRJ200Mechanic From United States of America, joined Feb 2005, 204 posts, RR: 2
Reply 10, posted (9 years 10 months 2 weeks 1 day 4 hours ago) and read 7115 times:

HAWK21M

They do have two screws on each end of the strip, but glue is the primary means of holding them down

Thanks for bringing that to my attention, I forgot about the screws



Always remember the responsibilies you hold with an A&P license
User currently offlineCRJ200Mechanic From United States of America, joined Feb 2005, 204 posts, RR: 2
Reply 11, posted (9 years 10 months 2 weeks 1 day 1 hour ago) and read 7105 times:

I need to correct myself

I looked at the strips closer and they only have one screw on the aft section of the strip



Always remember the responsibilies you hold with an A&P license
User currently offlineBsergonomics From United Kingdom, joined Jan 2002, 462 posts, RR: 0
Reply 12, posted (9 years 10 months 2 weeks 1 day ago) and read 7104 times:

For the uninitiated:

If you think that a lightning strike on an aircraft is a 'minor' occurrence, check out:

http://www.fugly.com/media/download....869&sort=&order=&rating=&per_page=

(In case the link doesn't work, do a Google search on "Plane_fast", which will give you the link)

It's a .gif 'movie' file that shows the strike in real time. There's also a slow version that show's the strike at a slower speed (do a search for, "plane_slow" and you should find it).

I should add that we design both military and civil aircraft for such an occurrence and normally the only damage is to the pilots' underwear....



The definition of a 'Pessimist': an Optimist with experience...
User currently offlineHAWK21M From India, joined Jan 2001, 31712 posts, RR: 56
Reply 13, posted (9 years 10 months 2 weeks 22 hours ago) and read 7099 times:

Quoting CRJ200Mechanic (reply 11):
I looked at the strips closer and they only have one screw on the aft section of the strip


Odd to have it at the Aft end rather than the Front [To avoid Peelback].
Is there a special mounting slot that the Diverter stips slides into & held locked by the Screw at the Aft end.
regds
MEL



Think of the brighter side!
User currently offlineCRJ200Mechanic From United States of America, joined Feb 2005, 204 posts, RR: 2
Reply 14, posted (9 years 10 months 2 weeks 22 hours ago) and read 7100 times:

All I could find in the manuals, (I have limited access to the SRM's) was a temporary repair

I have pasted portions below. It sound like the only slot they slide into would be the edge created by the paint.
If you would like more I will send. I just don't want the message to get too long. It's a pretty lengthy process

NOTE: THE INFORMATION PROVIDED IS FOR INFORMATION ONLY

1. General
This subject contains approved specific repairs for replacing and bonding of the nose radome lightning diverter strips.
2. LimitationsA. Temporary Repair is limited to 450 Flight hours maximum
B. All edges of each lightning strip must be completely bonded to the radome with no gaps, separations or pinholes.
C. The work area must be clean and well ventilated, with ambient temperature 20°C to 30°C (70°F to 90°F), and humidity not more than 75%.
D. Do not use power tools to abrade resin or surface of radome.
E. Use clean wax-free containers to mix the adhesive.
F. The adhesives must not be thinned.
A. Remove the nose radome, refer to the Aircraft Maintenance Manual (AMM).
B. Remove the hardware at the lightning strip termination, at the aft end.
C. Peel off the lightning strip from the surface of the radome.
D. Remove the old adhesive with a clean cloth dampened with methyl ethyl ketone.
E. Use pressure-sensitive mylar tape to mask off the area where the lightning strip is to be bonded. NOTE: The area must extend 0.125 inch (3.175 mm) beyond the edges and the ends of the lightning strip to form a fillet.

CAUTION: INSTALL THE LIGHTNING STRIP DIRECTLY ONTO THE PRIMED SURFACE OF THE RADOME ONLY.
F. Remove all the polyurethane topcoat in the lightning strip recess faying surface area by abrasion with #400 grit abrasive paper.
G. Lightly abrade the primer in the radome faying surface area using Scotchbrite pads to remove the glaze. NOTE: Damaged or missing primer must be replaced with one coat of primer CMS565-01 (refer to Chapter 51).

CAUTION: DO NOT ABRADE THE CENTER PORTION OF THE LIGHTNING STRIPS.
H. Abrade the faying surfaces of the lightning strips with #80 grit abrasive paper to remove all resin or paint glaze.
I. Clean the faying surfaces with a clean cloth dampened with methyl ethyl ketone. NOTE: The cleaned parts must be handled with clean white cotton gloves.

J. Mask off the external surface of the lightning strip with pressure-sensitive tape.
K. Prepare the Amicon CT-5047-2 A/B conductive adhesive by mixing one hundred parts by weight of A with six parts by weight of B. Part B shall be fully mixed into Part A in a clean, wax-free container. Do not thin the adhesive. NOTE: Mixed conductive adhesive remaining must be discarded after 45 minutes.

CAUTION: MAKE SURE THAT THE ADHESIVES ARE NOT APPLIED TO THE SEGMENTED SURFACES OF THE DIVERTER STRIPS.
L. Apply conductive adhesive to the strip termination attachment and the radome faying surfaces. Make sure that the faying surfaces are fully covered with a 0.005 inch (0.127 mm) layer of conductive adhesive, 0.360 inch (9.144 mm) forward of the termination attachment end, as shown in



Always remember the responsibilies you hold with an A&P license
User currently offlineCRJ200Mechanic From United States of America, joined Feb 2005, 204 posts, RR: 2
Reply 15, posted (9 years 10 months 2 weeks 21 hours ago) and read 7093 times:

HAWK21M
I found a good picture of the strips for you. I'm not sure if I can get it attached to message right. I have the pic saved if I screw up



Here are some pictures of the tail skid


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Photo © Airwim



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Photo © Freight-Dawg



Its just a small bumber on the seam of the tail cone. I apologize for the pics, it was the best I could do. Maybe someone else has some better pictures



Always remember the responsibilies you hold with an A&P license
User currently offlineCRJ200Mechanic From United States of America, joined Feb 2005, 204 posts, RR: 2
Reply 16, posted (9 years 10 months 2 weeks 21 hours ago) and read 7092 times:

HAWK21M

Sorry I can't figure it out. here is the link

http://www.jetphotos.net/viewphoto.php?id=149906



Always remember the responsibilies you hold with an A&P license
User currently offlineAirplay From , joined Dec 1969, posts, RR:
Reply 17, posted (9 years 10 months 2 weeks 16 hours ago) and read 7070 times:

Odd to have it at the Aft end rather than the Front [To avoid Peelback]..

The screw(s) are not there to hold the strips in place. They provide the path for the lightning to conduct to the primary airframe. In other words, they electrically bond the strips to the rest of the airplane.

If the screws were on the forward end, there would be no airframe to screw to.


User currently offlineCRJ200Mechanic From United States of America, joined Feb 2005, 204 posts, RR: 2
Reply 18, posted (9 years 10 months 2 weeks 8 hours ago) and read 7047 times:

Airplay

thanks for info, I didn't think of that. I don't really mess with the things doing line maintenance.



Always remember the responsibilies you hold with an A&P license
User currently offlineHAWK21M From India, joined Jan 2001, 31712 posts, RR: 56
Reply 19, posted (9 years 10 months 2 weeks 1 hour ago) and read 7026 times:

Quoting Airplay (reply 17):
If the screws were on the forward end, there would be no airframe to screw to.


Are you saying the radome on the CRJ cannot be screwd tight on the front but only on Aft,because of Airframe.Cant it be Connected from the Airframe to radome by bonding Jumpers.
regds
MEL



Think of the brighter side!
User currently offlineSanthosh From India, joined Sep 2001, 545 posts, RR: 1
Reply 20, posted (9 years 10 months 1 week 6 days 18 hours ago) and read 7015 times:

What sort of a metal is used to make the Diverter strips?

George



Happy Landing
User currently offlineCRJ200Mechanic From United States of America, joined Feb 2005, 204 posts, RR: 2
Reply 21, posted (9 years 10 months 1 week 6 days 17 hours ago) and read 7013 times:

Quoting HAWK21M (reply 19):
Are you saying the radome on the CRJ cannot be screwd tight on the front but only on Aft,because of Airframe.Cant it be Connected from the Airframe to radome by bonding Jumpers.



The screws are connted to bonding jumpers on the inside of the radome. I guess if they were connected up front they would get in the way of the radar. Just a guess though



Always remember the responsibilies you hold with an A&P license
User currently offlineAirplay From , joined Dec 1969, posts, RR:
Reply 22, posted (9 years 10 months 1 week 6 days 16 hours ago) and read 7013 times:

Are you saying the radome on the CRJ cannot be screwd tight on the front but only on Aft,because of Airframe.Cant it be Connected from the Airframe to radome by bonding Jumpers.

You guys are overthinking this one a bit...

 Smile

Of course there are an infinite amount of ways to do this. However, you are killing two birds with one stone if you use the radome mounting screws to bond the lightning diverter strips to the airframe.

Can it be done any other way? You bet. And chances are someone can present us with evidence that it is done differently on some airplane somewhere.

As alluded to in another post, you really want to avoid as much metal as possible in front of the radar antenna.


User currently offlineHAWK21M From India, joined Jan 2001, 31712 posts, RR: 56
Reply 23, posted (9 years 10 months 1 week 4 days 14 hours ago) and read 6956 times:

Why not just use bonding cables.
regds
MEL



Think of the brighter side!
User currently offlineAirplay From , joined Dec 1969, posts, RR:
Reply 24, posted (9 years 10 months 1 week 4 days 12 hours ago) and read 6948 times:

Quoting HAWK21M (reply 23):
Why not just use bonding cables.


If you had the choice between using a screw to bond the strips that you would have to install anyway to secure the radome or using bonding cables, why would you chose the latter?


25 Avt007 : I worked on an aircraft where the customer complained that the radios completely failed in clouds. Obviously they had a P-static problem, so I checked
26 Airplay : Avt007, Isn't it incredible, how a very small defect in the bonding has such a huge and serious effect on the airplane? I've had similar experiences w
27 Avt007 : Yes, something small and innocent looking can really mess up your day! On another occasion, a Falcon operator reported the loss of ADFs, Omega/VLF, an
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