In his own words - BWB and the OMABP

My understanding is that the purpose of the mesh is to prevent the strike by
draining the pre strike static accumulation, much like a lightning rod on a
house will prevent the lightning strike. As someone else commented, that got
them certified. Beyond that - I don't know. It has been way too many years
since I worked with high voltage systems.

"Capt.Doug" wrote in message
news
"frank" wrote in message The IFR certified models have a fine metal
mesh
layers embedded in selected
areas to provide a path for the electrical charges.

How many strikes can the mesh layer take before you throw away the plastic
airplane?

D.

On Mon, 12 Jul 2004 11:50:00 -0500, frank wrote:

My understanding is that the purpose of the mesh is to prevent the
strike by draining the pre strike static accumulation, much like a
lightning rod on a house will prevent the lightning strike. As someone
else commented, that got them certified. Beyond that - I don't know. It
has been way too many years since I worked with high voltage systems.


Not quite that simple. If you can make the surface conductive, you make
it similar to an all-metal aircraft. All-metal aircraft get hit with
lightning with great regularity, if they are in the right place at the
wrong time.

A type-certificated composite aircraft seeking IFR approval would have to
undergo the same sort of engineering evaluation as a metal aircraft.
Ground testing with simulated lightning strikes would likely be required.

See the picture of the Glasair III under test near the bottom of this page
for an example of the type of testing I mean:

http://oea.larc.nasa.gov/PAIS/Concep...lightning.html

FAA Advisory Circular 20-107A, COMPOSITE AIRCRAFT STRUCTURE says:

Lightning Protection.

(1) Some composites are susceptible to lightning damage, and do not
dissipate Pstatic electrical charges or provide electromagnetic shielding.
Therefore it should be demonstrated by analysis support by test evidence
that the structure can dissipate P-static electrical charges, provides
electromagnetic protection where required and provides an acceptable means
of diverting the resulting electrical current (as a result of a lightning
strike) so as not to endanger the aircraft.

(2) Consideration should be given possible deterioration and undetected
damage to the lightning protection system.

--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
e-mail: khorton02(_at_)rogers(_dot_)com

"Kevin Horton" wrote in message (1) Some composites are susceptible to
lightning damage, and do not
dissipate Pstatic electrical charges or provide electromagnetic shielding.
Therefore it should be demonstrated by analysis support by test evidence
that the structure can dissipate P-static electrical charges, provides
electromagnetic protection where required and provides an acceptable
means
of diverting the resulting electrical current (as a result of a lightning
strike) so as not to endanger the aircraft.

(2) Consideration should be given possible deterioration and undetected
damage to the lightning protection system.

That spells out the requirements. Other than the thin copper mesh already
mentioned, how are manufacturers meeting these requirements?

D.