Grounding of control tubes/cables

On Mar 5, 3:53*pm, Andy wrote:
On Mar 2, 8:38*pm, jcarlyle wrote:

Steve, Mike,

Again, I appreciate your answers. It's strange, though - the grounding
in my 1984 ASW19 is clearly home-made. I wonder why Schleicher would
do the -20s, and not the -19s.

I have no reason to think the bonding in my 19b (19356) was not
factory original. *The bonding on my 28 certainly is. *Some Schleicher
factory stuff looks home made. * Don't let that make you think it's
not factory original. Glider manufacture is a cottage industry. Didn't
you notice the German garden hose fittings in the water ballast
system?

How Schleicher got away with joining ballast valve control cables
with *electrical terminal blocks in the 28 is beyond me.

I may have some photos that show the bonding in 19356. *I'll check
tonight.

Andy

I have a photo of 19356 rudder cable bonding. Email me and I'll send
it to you.

Andy

Questions:
1. *What is the purpose of such bonding? Would it help at all with
lightning protection, or is it intended only to lessen static
discharge noise in the radio and other electrical systems?

All the metal parts should be grounded to prevent static noise in your
radio receiver (which you will get any time an ungrounded control is
moved).

2. *If bonding is useful, shouldn't all of the glider's control tubes/
cables be bonded?

Yes


3. *What would be the recommended method to effect a bond to aileron

The control tubes are usually grounded with a wire that goes to one of
the mounting bolts that hold the stick in place, the electrical
connection is then made through the stick into the aileron and
elevator pushrods.

Hope this helps,
JJ

Hi, Andy,

My 19b is 19397, so if yours was bonded by the factory then mine
probably was, too. I appreciate the offer of a photo, I'll write you
off-line about that issue.

Reiterating, I'm talking about a wire that leads from the battery
negative side bus bar to the rudder assembly. This is probably not the
bonding that you and others are talking about. Now, I know for a fact
that the battery was put in by the previous owner. And the reason I
think the bonding was homemade is because the ring connector to wire
junction has been made the the mother of all cold solder joints! We're
talking ugly, dull and lumpy, to the nth degree.

-John

On Mar 5, 5:53 pm, Andy wrote:
I have no reason to think the bonding in my 19b (19356) was not
factory original. The bonding on my 28 certainly is. Some Schleicher
factory stuff looks home made. Don't let that make you think it's
not factory original. Glider manufacture is a cottage industry. Didn't
you notice the German garden hose fittings in the water ballast
system?

Andy

Hi, JJ,

Your input is very much appreciated - thanks!

-John

On Mar 6, 9:13 am, JJ Sinclair wrote:
Questions:
1. What is the purpose of such bonding? Would it help at all with
lightning protection, or is it intended only to lessen static
discharge noise in the radio and other electrical systems?

All the metal parts should be grounded to prevent static noise in your
radio receiver (which you will get any time an ungrounded control is
moved).

2. If bonding is useful, shouldn't all of the glider's control tubes/
cables be bonded?

Yes

3. What would be the recommended method to effect a bond to aileron

The control tubes are usually grounded with a wire that goes to one of
the mounting bolts that hold the stick in place, the electrical
connection is then made through the stick into the aileron and
elevator pushrods.

Hope this helps,
JJ

Radio receive performance is important and the benefit arising from
bonding the controls would undoubtedly be a sufficient reason for
doing it. But the most compelling reason relates to crew safety and
airframe protection. FAR 23-867 requires bonding specifically for
lightning protection. See

http://www.risingup.com/fars/info/part23-867-FAR.shtml

Everyone knows that you should not fly a kite in a thunderstorm. It
would similarly be unwise to float your body near a thunderstorm with
your feet attached to one large electrode and your hands connected to
another large electrode. Any lightning that happens upon those
electrodes would want to flow through you, the gooey dielectric --
much better to have most of that current jolt going through a low
impedance bond wire.

On Mar 6, 4:06 pm, Steve Koerner wrote:
Radio receive performance is important and the benefit arising from
bonding the controls would undoubtedly be a sufficient reason for
doing it. But the most compelling reason relates to crew safety and
airframe protection. FAR 23-867 requires bonding specifically for
lightning protection. See

http://www.risingup.com/fars/info/part23-867-FAR.shtml

Everyone knows that you should not fly a kite in a thunderstorm. It
would similarly be unwise to float your body near a thunderstorm with
your feet attached to one large electrode and your hands connected to
another large electrode. Any lightning that happens upon those
electrodes would want to flow through you, the gooey dielectric --
much better to have most of that current jolt going through a low
impedance bond wire.

Steve:

No composite glider can comply with the FAR you quote nor would any
such plane survive a severe lightning strike. The bonding straps and
their connections are also clearly not robust enough to conduct
lightning currents. Lightning protection is generally only required
for IFR rated aircraft. Risks of lightning strikes while operating
VFR are small (although not zero).

The straps are clearly there to equalize potentials, but from what
source is anyone's guess.

My guess is atmospheric potentials resulting from wire cables during
winch launching.

Mike

On Mar 6, 12:39*pm, jcarlyle wrote:
We're talking ugly, dull and lumpy, to the nth degree.

-John


Awww John, you're not THAT bad...

P3

Is it GCup season yet?

First, the FAR that I quoted is not restricted to IFR aircraft, it is
generally applicable to certified airplanes in the normal category.

Mike is a noted expert in lighting and he can quote expert knowledge
as regarding the distribution in the intensity of lightning energy.
The distribution of lightning intensities is very wide. So when Mike
prefaces his discussion as relating to a severe lightning strike his
points are exactly right. A severe lightning strike is probably a
death sentence to one of us in a composite glider regardless of
bonding wires.

But my writing did not pertain to a severe lightning strike; quite the
opposite, in my 2/29 post I restricted the applicability of my remarks
to the case of lower energy levels.

Anyone who has ever seen a nice photograph of a lightning strike knows
that there are branches and tentacles of differing brightness. The
varying brightness of those lightning tentacles and their distribution
in 3-space must indicate that for an arbitrarily positioned glider
there is a very good chance that the lighting that he is most likely
to encounter will not be the main bolt but rather a lower intensity
tentacle.

Many gliders have survived lightning hits. Clearly lower intensity
lightning is a matter of interest and concern. My premise is that
bonding the controls in a glider is a low cost measure intended to
slide the survivability point in the spectrum of lightning intensities
that could be encountered. It is further my premise that the most
sensitive component in the airframe is the pilot and that bonding the
controls that the pilot is touching goes a long way towards protecting
that sensitive component. Even if the wings were to explode, the
pilot may have an opportunity to bail out if he is protected to a
degree that he is able to do so.

The bond wires in my glider look to be maybe 14 gauge which would
certainly fuse if the lightning energy is very great. But it would
be pointless to give the bond wires a lot more current handling
ability than the steel control cables and steel drive tubes. All the
bond wires need is a little bit more current handling ability than the
drives to be effective. Since copper is 10 times more conductive
than steel, that is probably what is being accomplished.

Mike is undoubtedly right that bonding will help to protect against
atmospheric potentials during a wire ground launch. JJ is surely
correct that bonding will make the radio work better in receive. I'm
still convinced that the foremost equation that gets the bond wires
installed in the first place is the lightning protection equation. As
I have pointed out, it is lightning protection which is the express
reason that the FARs require electrical bonding in certified aircraft.

Oh, thanks, Erik! Thanks very much. My seconds will call upon your
seconds. Or......you can let me fly your LS-8 once....8-)

-John


On Mar 6, 10:52 pm, Papa3 wrote:
On Mar 6, 12:39 pm, jcarlyle wrote:

We're talking ugly, dull and lumpy, to the nth degree.

-John

Awww John, you're not THAT bad...

P3

Is it GCup season yet?

......and I should add I have seen a couple of gliders survive minor
lightning discharges, including an ASW-27. This suffered a strike
from nose to tail, the exit point leaving a little hole in the upper
rudder area, but no major structural damage. I spoke to the pilot and
he suffered no injury, but his electronic instruments were damaged.

I'll bet the requirement for bonding is in the German regulations.
Perhaps one of our readers over there could help us?

Mike