LIGHTNING DIVERSION STRIPS

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4 Generations of Diverter Strips are currently available for the complete requirements of Aircraft, Rotorcraft and Wind Turbines.

Lightning Diversion Systems was the Pioneer of Segmented Diverter Strips, and has stayed at the forefront of development to meet the needs of the full range of frequencies that today’s antenna’s operate at.

In addition, robust and durable strips have been developed specifically to meet the demand of Wind Turbines to ensure maximum up time.

Segmented Diverter StripsInstallation Guide ApplicationRF Path Loss Data ApplicationPart Number ListRequest A Quote

LIGHTNING PROTECTION SYSTEM • AIRCRAFT APPLICATIONS

Lightning Diversion Systems is the market leader in the design and manufacture of lightning protection devices that divert lightning strokes from aircraft nose Radomes and other sensitive areas. The protection system consists of a segmented diverter strip which provides maximum multiple-strike protection with negligible effect on RF pattern characteristics. Attached to an aircraft’s radome or other structure, the system allows a lightning stoke to travel safely and directly to ground in an ionized channel created in the air above the diverter strip. It combines permanent protection with low drag aerodynamics and has a negligible effect on radar antenna radiation patterns. The electrostatic shield created by the system provides a new source of streamers outside the radome wall to the fuselage. The resistance material in the strips help initiate the ionized channels and provides a bleed-off path for P-static. The small diameter of the disc segments makes the strips compatible with radar system including Ku and Ka band, and disc size can be modified for optimum antenna patterns at higher frequencies.

ADVANTAGES OF LIGHTNING DIVERSION SYSTEMS MULTI-STRIKE LIGHTNING PROTECTION

      • R.F. Transparency – Compatible with Ku and Ka Band Antennas
      • Multi-Strike Capability
      • Weight
        • .012 Material Thickness
          Measured: 8.2 grams per 3 ft. section
        • .005 Material Thickness
          Measured: 5.4 grams per 3 ft. section
      • Ease of Installation and Maintenance Cost
      • No holes drilled for installation to radome – Can eliminate moisture problems
      • Savings realized because of number of parts needed for solid diverter installations
        • Drill holes – Install inserts – Seal inserts
          Install Solid Diverters – Install Bolts and seals
      • No current flow in LDS strips as opposed to solid diverters

 

Segmented diverters offer significant advantages whereby you do not have electromagnetic effects from current flow as you do in solid diverters. Further, high current making right turn from solid diverter to bolt causes physical damage, whereas current traveling in an ionized path above the buttons makes a smooth transfer to airframe.

The p-static channel created by the resistance material in the Lightning Diversion Systems diverter strip eliminates the problems inherent in the design of the foil strip, solid metal diverter bar and internal rod systems.
Sophisticated technology requires congruent safety devices. Pitot boom installations on a nose radome increase the possibility of lightning damage. Damage from lightning striking this type of installation can cause malfunctions of adjacent instrumentation systems. Diverter strips placed on the Radomes and other antenna enclosures allow lightning to travel in an ionized channel above the strip without harm to vital instruments and cockpit personnel.

Extensive testing indicates that the Lightning Diversion Systems strips will withstand current transfer greater than 200,000 amperes with little or no damage. (More than 99.5% of natural lightning strokes measured display peak current of less than 150,000 amperes.)

APPLICATION NOTE • AN10007

GENERAL GUIDELINES FOR INSTALLATION OF SEGMENTED LIGHTNING DIVERTER STRIPS

Following are some general guidelines for installation of Lightning Diversion Systems’ Segmented Lightning Diverter Strips.


GENERAL

Segmented diverter strips consist of a series of critically spaced metal segments mounted on a thin dielectric substrate. The strips are designed to withstand multiple lightning strikes and to have a negligible effect on RF pattern characteristics.

The diverter strips are bonded to the exterior surface of radomes, dielectric enclosures, and composite parts and once properly grounded they provide an electrostatic lightning shield for antennas and other equipment contained in the radome, and will protect wind turbine blades in the event of a lightning event.

PLACEMENT

Diverter strips should be positioned and installed so that any antennas, pitot tubes, heater wires, air data lines, tuning wires, and other equipment installed under the radome are protected from lightning strikes from all possible directions.

There are no hard and fast rules on spacing, but generally the spacing between strips should range from 12 to 24 inches. Where applicable, spacing is dependent on the size and dielectric strength of the radome and the shape and proximity of metal objects beneath the radome.

BONDING

The bonding process for diverter strips is established by the manufacturer of the radome/mounting structure or by the maintenance installation facility.

The following information describes some successful processes for positioning and bonding diverter strips.

Bonding methods fall into two general catagories: 1. bonding using a pre-applied pressure sensitive adhesive and 2. bonding using conventional epoxy adhesives.

Bonding Using Pre-applied Pressure Sensitive Adhesive (PSA)

The latest generation diverter strips are supplied with a pre-applied pressure sensitive adhesive (3MA10 Acrylic Adhesive No. 9473 tape).

Ideally these strips should be applied at temperatures between 70ºF to 100ºF. Application at temperatures below 50ºF is not recommended. Bond strength is dependent upon the amount of adhesive-to-surface contact and depends on having a clean, dry and well unified substrate.

Suggested installation steps are as follows:

  • Clean the substrate with a suitable solvent. Some typical surface cleaning solvents are isopropyl alcohol or heptane (Note: Be sure to follow the manufacturer’s precautions and directions for use of solvents).
  • Allow the substrate to dry completely.
  • Mark the location of the strip with a pencil or marker.
  • Apply masking tape the full length of the strip on both sides of the strip location using your marks as guidelines.
  • Lightly scuff the area between the masking tape with 320-400 sandpaper or scotch brite pad.
  • Re-wipe the mounting area with solvent and allow to dry.
  • Apply a thin coat of 3M Promoter 86A to mounting area in accordance with manufacturer’s instructions.
  • Remove the protective paper from the back side of the diverter strip.
  • Carefully place the diverter strip in its proper location on the substrate being careful not to let the strip touch the substrate until the diverter strip is in the proper position.
  • Apply firm, even pressure to the strip using a firm (not hard) roller to assure complete adhesive-to-surface contact.

 

Workmanship: There shall be a continuous bond of the diverter strip to the substrate surface with no voids or separation along the diverter edge.

Bonding Using Conventional Adhesive (PSA)

Diverter strips supplied without pre-applied adhesive are installed using a conventional adhesive selected by the user. Choice of bonding adhesive should be based on compatibility with the diverter strip, the substrate and the operating environment. Some adhesives that have been successfully used are:

  • Hysol EA 956 Epoxy Paste Adhesive
  • Hysol EA 960F Epoxy Paste Adhesive
  • Hysol EA 9330 Epoxy Paste Adhesive
  • 3M 847 Rubber & Gasket Adhesive
  • 3M 2216 Epoxy Adhesive

 

To insure a compete and secure bond, installation is generally done using vacuum bagging.

Suggested installation steps are as follows:

  • Prepare the bond surface of the substrate.
      • Clean the substrate with a suitable solvent. Some typical surface cleaning solvents are isopropyl alcohol or heptane (Note: Be sure to follow the manufacturer’s precautions and directions for use of solvents.).
      • Allow the substrate to dry completely.
      • Mark the location of the strip with a pencil or marker.
      • Apply masking tape the full length of the strip on both sides of the strip location using your marks as guidelines.
      • Lightly scuff the area between the masking tape with 320-400 sandpaper or scotch brite pad.
      • Remove the masking tape.
      • Re-wipe the mounting area with solvent and allow to dry.

 

  • Prepare the bond surface of the diverter strip
      • Clean with suitable solvent.
      • Lightly scuff the back side using a fine scotchbrite pad (Note: For strips with a black resistive strip on the back, take particular care not to damage the black strip.)
      • Re-clean the surface with suitable solvent.
      • Allow the strip to dry completely.
      • Avoid handling the bond surface of the strip.

 

  • Apply masking tape to the mounting surface on both edges of the diverter strip location the full length of the diverter strip. The tape will limit the spread of the adhesive and help with positioning the diverter strip (See illustration below).1
  • Mix the adhesive in accordance with the manufacturer’s instructions and apply it to the back side of the diverter strip.
  • Position the diverter strip and tape it in place.
  • Vacuum bag the diverter strip and allow adhesive to cure in accordance with manufacturer’s instructions.
  • After cure, remove bagging material and masking tape and clean off excess adhesive using Teflon or phenolic tools to preclude damaging the nickel segments.

 

Workmanship: There shall be a continuous bond of the diverter strip to the substrate with no voids at the edges. The bonded strip shall be free of excessive adhesive and other surface defects.

PAINTING

The metal segments on the surface of the diverter strips must be kept free of paint and coatings.

For Installations to be Painted after Strip Application

Select a masking/striping tape the same width as the nickel segments and apply it over the segments the length of the strip.

2

Paint the radome or mounting surface as normal. The paint will serve as additional fairing material for the strip.

3

Remove the masking tape from the segments and clean off any tape residue

4

Paint on the outside edges of segments is permissible. Remove any paint on the surface of the segments or in between the segments. Use of Teflon or phenolic tools is suggested to prevent damage to the segments.

For Installations with No Subsequent Painting

Apply an adhesive fillet along the diverter strip to fair the strip to the radome surface. The adhesive fillet is to be approximately 0.12±0.06” wide along the strip. The adhesive fillet should not extend up onto the strip such that it covers the nickel segments.

5

ELECTRICAL BONDING (GROUNDING)

The diverter strip must be electrically connected (grounded) to the metal mounting structure of the radome.

Some typical methods of grounding the diverter strips are shown below.

6

Figure 1 – Grounding of diverter strip through a bleeder resistor – no special connector required at the end of the strip.

7

Figure 2 – Grounding of diverter strip using a #10 bolt through the termination. (Note: Many termination styles, both flat and countersunk, are available.) Lightning attaches directly to the grounding bolt.

8

Figure 3 – Grounding of diverter strip using Grounding Clip (LDS P/N LDS10-10 & LDS10-07). Diverter strip is installed under the indentation in the grounding clip. Lightning attaches to the clip.

RESISTANCE MEASUREMENTS

Ground Connection Resistance

Resistance between the lightning strip termination pad and the attachment flange should be 0.01 Ohm or less.

Where a resistor is used to ground the diverter strip as in Method A, the resistance to ground shall be as specified in the radome detail specification or the diverter installation drawing.

Lightning Strip Resistance

Normally, lightning strip resistance is not measured in the field. However, when measurement is required by the radome specification, resistance values should be in accordance with the radome spec.

As a point of interest, electrical resistance of the strip is measured as part of the normal production process. Values vary by lightning strip type and are specified in Lightning Diversion Systems Material Specifications LDS10-01 and LDS10-02.

Diverters with a resistance strip on the back have a specified resistance value of between 0.5 and 100.0 megohms per inch when measured with 500 volts applied.

Measurement requires the use of a “Megger” insulation tester. Normal practice is to measure resistance from end to end of the diverter and divide the value by length to get an average per inch value.

APPLICATION NOTE • AN10002

SEGMENTED DIVERTER EFFECTS ON RF PATH

Tests were conducted to determine path (transmissivity) loss due to lightning diverter strips. Diverters were positioned three to four inches in front of and centered on a 12” antenna transmitting at 9.345 GHz.

Tests were conducted with the diverter strips in several orientations relative to the polarity of the antenna.

Some comparison measurements were made with the strip 12” from the antenna to determine the effect of distance from the transmitting antenna. There was no measurable difference in path loss.

Test* results in dB and percentage loss are presented below.

Diverter Type Diverter Parallel to Polarization Diverter at 20˚ to Polarization Diverter at 40˚ to Polarization Diverter Perpendicular to Polarization Voltage to Ionize 40″ Strip
0.42” Wide, Heavy Duty Aluminum 0.95 dB 19.6% 0.7 dB 14.9% 0.7 dB 14.9% 0.5 dB 10.9% N/A
¼” Wide Aluminum 0.7 dB 14.9% 0.7 dB 14.9% 0.3 dB 6.7% 0.5 dB 4.5% N/A
0.060 X 0.200” Oval Segment 0.5 dB 10.9% 0.5 dB 10.9% 0.2 dB 4.5% 0.0 dB 0.0% 20 – 30 KV
0.125” RND Segment 0.1 dB 2.3% 0.1 dB 2.3% 0.1 dB 2.3% 0.0 dB 0.0% 30 – 40 KV
0.100” RND Segment 0.1 dB 2.3% 0.1 dB 2.3% 0.1 dB 2.3% 0.0 dB 0.0% 40 – 50 KV
0.060” RND Segment 0.0 dB 0.0% 0.0 dB 0.0% 0.0 dB 0.0% 0.0 dB 0.0% 40 – 50 KV

*Tests performed by a major radome manufacturer.

Losses reflect worst case application which is with the diverter extending completely across the maximum diameter of the antenna.

SEGMENTED DIVERTER STRIPS

Part Number Type Width Length Terminal Segment Type/Size Color
LDS10-01 Series
LDS10-01-01 Lightning Strip 0.400 CR 0.650 Round, Dimpled 0.125 Large Round CR
LDS10-01-02 Lightning Strip 0.400 CR .400 tab .195 hole 0.125 Large Round CR
LDS10-01-03 Lightning Strip 0.400 CR None 0.125 Large Round Black
LDS10-01-04 Lightning Strip 0.400 CR None 0.125 Large Round Natural
LDS10-01-05 Lightning Strip 0.400 CR 1.25 tab 0.125 Large Round White
LDS10-02-05 Lightning Strip 0.400 CR Custom 0.125 Large Round White
LDS10-01-06 Lightning Strip 0.400 CR .500 Round, Dimpled 0.125 Large Round White
LDS10-01-07 Lightning Strip 0.400 80 0.400 (2) ends 0.125 Large Round Black
LDS10-01-08 Lightning Strip 0.400 120 0.400 (2) ends 0.125 Large Round Black
LDS10-01-09 Lightning Strip 0.400 36 None 0.100 Round Black
LDS10-01-10 Lightning Strip 0.400 48 None 0.100 Round White
LDS10-01-11 Lightning Strip 0.500 CR Custom 0.100 Round N/A
LDS10-01-12 Lightning Strip 0.400 CR None 0.125 Large Round CR
LDS10-01-13 Lightning Strip 0.400 22 – 28 .400 Tab 0.125 Large Round Natural
LDS10-01-14 Lightning Strip 0.400 48.5 .400 Tab 0.125 Large Round Natural
LDS10-01-15 Lightning Strip 0.500 16 None 0.100 Round Natural
LDS10-01-16 Lightning Strip 0.400 46.7 Custom 0.100 Round Natural
LDS10-01-17 Lightning Strip 0.400 CR .400 Tab 0.100 Round White
LDS10-01-18 Lightning Strip 0.400 120 0.400 (2) ends 0.125 Large Round Gray
LDS10-01-19 Lightning Strip 0.400 CR .500 Round, Flat 0.125 Large Round CR
LDS10-01-22 Lightning Strip 0.400 CR 0.5 Rnd & 0.195 Hole 0.125 Large Round CR
LDS10-01-23 Lightning Strip 0.400 CR None 0.125 Large Round Black
LDS10-01-24 Lightning Strip 0.400 CR None 0.125 Large Round Natural
LDS10-01-25 Lightning Strip 0.400 330.74 0.400 (2) ends 0.125 Large Round Black
LDS10-01-26 Lightning Strip 0.400 CR None .060/.200 Oval Green
LDS10-01-27 Lightning Strip 0.400 CR .500 Round, Flat 0.100 Round Green
LDS10-01-29 Lightning Strip 0.400 CR .500 Round, Flat 0.125 Large Round Black
LDS10-01-30 Lightning Strip 0.400 15 .500 Round, Dimpled 0.125 Large Round White
LDS10-01-31 Lightning Strip 0.400 CR .500 Round, Dimpled .060/.200 Oval CR
LDS10-01-32 Lightning Strip 0.400 CR None 0.060 Small Round CR
LDS10-01-33 Lightning Strip 0.400 CR None .060/.200 Oval CR
LDS10-01-34 Lightning Strip 0.400 CR None 0.125 Large Round CR
LDS10-01-35 Lightning Strip 0.400 330.47 0.400 Tab & 0.195 Hole .060/.200 Oval Gray
LDS10-01-36 Lightning Strip 0.400 CR .500 Round, Dimpled 0.125 Large Round White
LDS10-01-37 Lightning Strip 0.400 CR .500 Round, Dimpled 0.100 Round Black
LDS10-01-38 Lightning Strip 0.400 CR 0.650 Round & 0.33 Hole 0.060 Small Round CR
LDS10-01-38 Lightning Strip 0.400 CR 0.650 dia, 0.250 Hole 0.060 Small Round Black
LDS10-01-39 Lightning Strip 0.400 CR 0.500 Round, Dimpled 0.060 Small Round CR
LDS10-01-40 Lightning Strip 0.400 CR 0.500 Round, Dimpled .060/.200 Oval CR
LDS10-01-41 Lightning Strip 0.400 CR 0.400 Tab & .156 Hole .060/.200 Oval CR
LDS10-01-42 Lightning Strip 0.400 CR 0.500 Round, flat 0.060 Small Round White
LDS10-01-43 Lightning Strip 0.400 CR 2.00×0.4 Tab & 1.87 Hole .060/.200 Oval CR
LDS10-01-44 Lightning Strip 0.400 CR 1.25×0.4 Tab & 0.2 slot .060/.200 Oval Black
LDS10-01-45 Lightning Strip 0.400 CR 1.25×0.4Tab & 0.2 Hole 0.060 Small Round CR
LDS10-01-46 Lightning Strip 0.400 CR 1.25×0.4 Tab & 0.2 slot .060/.200 Oval N/A
LDS10-01-47 Lightning Strip 0.400 CR 0.5 Round & 0.2 Hole 0.125 Large Round CR
LDS10-01-48 Lightning Strip 0.400 CR 0.500 Round, flat .060/.200 Oval CR
LDS10-01-49 Lightning Strip 0.400 CR 0.4 Tab & 0.195 Hole 0.125 Large Round CR
LDS10-01-51 Lightning Strip 0.400 CR 0.65 Round & 0.25 hole 0.125 Large Round CR
LDS10-01-52 Lightning Strip 0.400 CR 0.4 Tab & 0.2 Hole 0.060 Small Round CR
LDS10-01-53 Lightning Strip 0.400 CR 0.4 Tab & 0.2 Hole .060/.200 Oval CR
LDS10-01-54 Lightning Strip 0.400 CR 0.5 Round & 0.24 Hole .060/.200 Oval CR
LDS10-01-55 Lightning Strip 0.400 CR None 0.060 Small Round CR
LDS10-01-57 Lightning Strip 0.400 332 0.4 Tab & 0.95 Hole .060/.200 Oval White
LDS10-01-58 Lightning Strip 0.400 CR 0.65 Round & 0.25 Hole .060/.200 Oval CR
LDS10-01-59 Lightning Strip 0.400 CR 1.875×0.4 Tab & .45 Hole .060/.200 Oval CR
LDS10-01-60A Lightning Strip 0.400 18 & 36 1.875×0.4 Tab & .45 Hole .060/.200 Oval CR
LDS10-01-60B Lightning Strip 0.400 36 1.875×0.4 Tab & .45 Hole .060/.200 Oval CR
LDS10-01-61 Lightning Strip 0.400 CR 1.125 dia, .8125 dia hole .060/.200 Oval CR
LDS10-01-62 Lightning Strip 0.400 CR 0.650 dia, 0.250 hole .060/.200 Oval CR
LDS10-01-63 Lightning Strip 0.400 CR 1.73×0.4 Tab & 0.28 Hole .060/.200 Oval CR
LDS10-01-64 Lightning Strip 0.400 CR Various Various CR
LDS10-04-01 Series Wind Turbine
LDS10-04-01 Lightning Strip 0.600 CR Type 00 Call For More Information CR

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