Aircraft Lightning Protection
Aircraft Lightning Protection
(OP)
I am currently working on a secondary wing structure for a military aircraft. The structure will be primarily made of carbon fiber/epoxy. The mounting features to the aircraft are 7075 aluminum that will be bonded to the carbon and the fairings will be glass/epoxy which will be quarter turn connected or something very similar to the carbon main structure. I am wondering if anyone knows any good resources for handling lightning protection of such a structure or can offer any other potentially helpful information. Thanks





RE: Aircraft Lightning Protection
RE: Aircraft Lightning Protection
thread16-20511
RE: Aircraft Lightning Protection
good luck
RE: Aircraft Lightning Protection
As for the 7075 to carbon bond I believe that we are going to be using a phos anodize prep. The military also suggested PER MIL-DTL-81706A, CLASS 1A (ALODINE 1201) however I believe this detail is more for components that are not going to bond to the structure. All of the AL/Carbon contact areas we will have isolation plies of glass.
Thanks again to all that have offered there insight....
RE: Aircraft Lightning Protection
http://hyp
Even if your wing were solid metal, there probably would be localized damage after a strike. Your best approach is to determine how other people are dealing with this, e.g., they may be designing the wings to be modularly repairable.
TTFN
RE: Aircraft Lightning Protection
Modern aircraft designs, Boeing & Airbus, generally do not now use embedded mesh in panels and rely on the conductivity of CFC and lightning wicks bonded to prime structure through metal straps. Mesh is used to provide ground planes for radio antennas and EMC shielding where it is needed but not otherwise.
Protection of fuel tanks is another matter and there are specific requirements there.
The corrosion issue referred to by rb1957 is very important as 7xxx alloy is at the opposite end of the galvanic scale to CFC and Ti. This guarantees corrosion if any water gets into the joint - ever. The Al is sacrificial to the CFC so if the smaller part (eg a fastener) is the sacrificial one then it will slowly disintergrate. This is why Ti fasteners are used and thin fibreglass layers to seperate the materials at the join to break the electrical path for galvanic corrosion. Of course you now need to have a bonding strap on the now insulated panel to account for lightning.
I have listed a section taken from MIL-STD-464A below that shows where you can obtain guidance on lightning protection for military aircraft.
Society of Automotive Engineers, Inc.
ARP1870 Aerospace Systems Electrical Bonding and Grounding for Electromagnetic Compatibility and Safety
ARP4242 Electromagnetic Compatibility Control Requirements, Systems
ARP5412 Aircraft Lightning Environment and Related Test Waveforms
ARP5413 Certification of Aircraft Electrical/Electronic Systems for the Indirect Effects of Lightning
ARP5414 Aircraft Lightning Zoning
ARP5415 User’s Manual for Certification of Aircraft Electrical/Electronic Systems for the Indirect Effects of Lightning
ARP5416 (Draft) Aircraft Lightning Test Methods
ARP5577 Aircraft Lightning Direct Effects Certification
RE: Aircraft Lightning Protection
When I worked at Cessna as a structural liaison engineer, we had a lightning strike class. They brought in some composite Citation 10 panels that had been struck by a lightning generator. They were experimenting with differing the paint thickness to see what the effects were. The results were amazing. Thin paint caused only minor pits in the paint because the lightning didn't have to fight through the paint to get to the metal mesh (I think it was called Astrostrike - I know Scaled Composites uses it) embedded in the composite surface. A panel that had thick paint had a large hole blown through it. The point of this exercise is to not only control the paint thickness during manufacture, but to put into the maintenance manuals to control the paint thickness if a hole in the panel is patched or if paint is touched up in the field.
Chase
www.dropmaster.com
RE: Aircraft Lightning Protection
htt
This was accomplished by using a combination of fine wires in the first layer of composite skin and a ground-plane system to shield the electronics, allowing the lightning current to flow through and out, leaving only minor surface and cosmetic damage at the strike point.
If you plan on placing antennas in your structure, the lightning protection can affect them greatly.
kch
RE: Aircraft Lightning Protection
RE: Aircraft Lightning Protection
Several approches, screen (something like stainless or coated copper), or a spar along the outside edge of the part.
My experience is the strike will take the straightest path of least resistance to lowest potential.
My requirements are safe flight to land and repair.
Hope this helps.
RE: Aircraft Lightning Protection
RE: Aircraft Lightning Protection
Hence a simple wire is a poor lightning protection atop a house due to it's high inductance. 6" wide wire braid is 1000x better.
kch
RE: Aircraft Lightning Protection
RE: Aircraft Lightning Protection
RE: Aircraft Lightning Protection
My exgirlfriend had a lightning experience last summer whilst at her computer. Her keyboard caught fire in a lightning strike.
Her boss spent $50K in lightning protection and a recent lightning strike took out her computer last week (washington dc area). It did it without exploding her keyboard this time. I told her to buy a "wireless keyboard, wireless mouse" or put me in your will.
sorry, I diverged from air to ground lightning strikes.
kch
RE: Aircraft Lightning Protection
RE: Aircraft Lightning Protection
http://w
RE: Aircraft Lightning Protection
RE: Aircraft Lightning Protection
RE: Aircraft Lightning Protection
RE: Aircraft Lightning Protection
http://www.daytongranger.com/