doctornigel
Active Member
Is anyone bothered with bonding straps and static wicks? Any problems without them. Thanks
Van's Air Force
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Bonding straps and static wicks
- Thread starter doctornigel
- Start date
Norman CYYJ
Well Known Member
Bonding is a good thing especially if you are installing a VOR. Sometimes the control surfaces can cause scalloping in the needle of the CDI. This is caused because sometimes the signal will be reflected off of the control surface and arrive at the antenna at a different time causing a problem. It is easier to bond now then later when the plane is completed.
Just curious...I thought about bonding straps then figured I wasn't using wicks so didn't do the straps. Isn't the control surface bonded (I know not to the Milspec definition) through the bearings and bolts that hold the control surface to the aircraft? It seems that it's an all metal path from the hinge and even the pushrod right?...What am I missing?
I know I am because I have removed bonding straps from H*LL on fighters but then they had wicks and much heavier metal to metal contact through hinge and actuators. Is it to "hopefully" carry the charge around those points to eliminate arc welding the bearing/hinge in a lightning strike? Static charge I assume would not do damage to them.
I know I am because I have removed bonding straps from H*LL on fighters but then they had wicks and much heavier metal to metal contact through hinge and actuators. Is it to "hopefully" carry the charge around those points to eliminate arc welding the bearing/hinge in a lightning strike? Static charge I assume would not do damage to them.
Gary 40274
Well Known Member
If you are relying on the hinges to carry the static electrical charge, you may find that you have welded the bearings solid at a most inopertune time. The bonding strips are to provide the path of least resistance for dissapation of P-static.
I certainly am not an athority on this but I have bonded and wicked all my planes.
Gary Specketer
I certainly am not an athority on this but I have bonded and wicked all my planes.
Gary Specketer
jjconstant
Well Known Member
Bonding and Grounding
Someone who knows what they're talking about, please jumpt in but, I was told that the difference between bonding and grounding had to do with the difference between dealing with AC and DC currents. Is this right?
If I recall correctly, I was told that bonding (as I understand it, the braided/woven metallic fabric like stuff) was used to deal with AC, which is associated with RF. Apparently this travels across metallic surfaces more readilly than through the core of the metal. Grounding was associated with DC and tended to travel through the the core of the metal and not so much on the surfaces. Hence the braided straps with LOTS of "surface" for AC/RF and wires for DC.
Unless I've made a complete hash of this, which is certainly possible
I'm hoping to learn more...from those who know...
Jeremy
Someone who knows what they're talking about, please jumpt in but, I was told that the difference between bonding and grounding had to do with the difference between dealing with AC and DC currents. Is this right?
If I recall correctly, I was told that bonding (as I understand it, the braided/woven metallic fabric like stuff) was used to deal with AC, which is associated with RF. Apparently this travels across metallic surfaces more readilly than through the core of the metal. Grounding was associated with DC and tended to travel through the the core of the metal and not so much on the surfaces. Hence the braided straps with LOTS of "surface" for AC/RF and wires for DC.
Unless I've made a complete hash of this, which is certainly possible
I'm hoping to learn more...from those who know...
Jeremy
Static wicks are used to disipate the "static" electrical charge that builds up on the surface of the skin of an aircraft as it moves through the air. The faster the aircraft, the more likely the probability that a static charge can be generated. Different atmospheric conditions can accelerate the accumilation of the static charge, such as temperature, humidity, dust, clouds, rain, etc.
Spinning turboprop and helicopter blades are excelent generators of a static charge even when sitting on the ground...
The instalation of static wicks helps to encourage the disapation of the static charge buildup before it reaches very high levels i.e. thousands of volts. If the static charge is allowed to build up, it will eventually discharge...at a time and place of its own choosing...into the surrounding air. Although the discharge may not be visually seen, it does occur and has the same properties as its big brother, the lightning bolt. The only difference is the power density. The generated EM field is extremily large for the lightning bolt and small for the static wick discharge. I would expect some of my electronic nav aids to hickup with nearby lightning bolts, but not when I only have aircraft generated static charges being disipated through the static wicks.
So, without the static wicks installed, and a large static charge being built up, the discharge is going to happen. The wings and fuselage are the biggest static generators, and the charge is happy to stay right there on the surfaces. But then the A/C has control surfaces, and they have somewhat sharp trailing surfaces (relative). The static charge tends to be concentrated around these sharp surfaces and when the voltage exceeds the breakdown voltage of air (or whatever we happen to be flying through at the time), a static discharge will occur. If static wicks are present, the static discharge occurs at a much lower voltage level. No wicks...a higher level.
The discharge path from (say) a wing to an aileron would be through whatever bearing / hinge material connects the two. This hinge may not be a perfect conductor, so it is possible that the charge will generate a small static spark in the hinge material and cause a small microscopic pit. Do this thousands of times and you may end up with a bad /binding bearing.
So, how do you provide a low impediance path between the wing and the aileron? Answer: We provide a bond wire between the two. This provides a desireable discharge path to the static charge that does not pass through the aileron hinge.
The bond wire is usually a braded wire, but it does not have to be. It does not need to be insulated. The use of a braded wire allows for flexability, plus the many, many strands of individual wires provides a large surface area (skin) to take advantage of the skin effect related to any high frequency components within the static discharge event.
(skin effect relates to the ability of a conductor to transfer high frequency electrical energy along the conductor. DC current can be thought of as traveling through the entire cross section of the conductor. Low frequency AC signals (60Hz in U.S homes) / currents also travel in the entire cross section of the conductor. As the frequency increases, say 50 to 100 Mhz, then the currents move away from the entire cross section and towards the outer surface of the conductor. The higher the frequency, the more pronounced this becomes. So for a given wire size, the wire can carry more DC current than a high frequency signal of the same power delivery without power loss.) This is why "fat" braded wires are sometimes used as the bonding "wire" of choice. This is also why VOR's use one type of coax, and txponders use another, and GPS's use yet another...depending on how long the coax wire run needs to be.
Hope this helps...
Spinning turboprop and helicopter blades are excelent generators of a static charge even when sitting on the ground...
The instalation of static wicks helps to encourage the disapation of the static charge buildup before it reaches very high levels i.e. thousands of volts. If the static charge is allowed to build up, it will eventually discharge...at a time and place of its own choosing...into the surrounding air. Although the discharge may not be visually seen, it does occur and has the same properties as its big brother, the lightning bolt. The only difference is the power density. The generated EM field is extremily large for the lightning bolt and small for the static wick discharge. I would expect some of my electronic nav aids to hickup with nearby lightning bolts, but not when I only have aircraft generated static charges being disipated through the static wicks.
So, without the static wicks installed, and a large static charge being built up, the discharge is going to happen. The wings and fuselage are the biggest static generators, and the charge is happy to stay right there on the surfaces. But then the A/C has control surfaces, and they have somewhat sharp trailing surfaces (relative). The static charge tends to be concentrated around these sharp surfaces and when the voltage exceeds the breakdown voltage of air (or whatever we happen to be flying through at the time), a static discharge will occur. If static wicks are present, the static discharge occurs at a much lower voltage level. No wicks...a higher level.
The discharge path from (say) a wing to an aileron would be through whatever bearing / hinge material connects the two. This hinge may not be a perfect conductor, so it is possible that the charge will generate a small static spark in the hinge material and cause a small microscopic pit. Do this thousands of times and you may end up with a bad /binding bearing.
So, how do you provide a low impediance path between the wing and the aileron? Answer: We provide a bond wire between the two. This provides a desireable discharge path to the static charge that does not pass through the aileron hinge.
The bond wire is usually a braded wire, but it does not have to be. It does not need to be insulated. The use of a braded wire allows for flexability, plus the many, many strands of individual wires provides a large surface area (skin) to take advantage of the skin effect related to any high frequency components within the static discharge event.
(skin effect relates to the ability of a conductor to transfer high frequency electrical energy along the conductor. DC current can be thought of as traveling through the entire cross section of the conductor. Low frequency AC signals (60Hz in U.S homes) / currents also travel in the entire cross section of the conductor. As the frequency increases, say 50 to 100 Mhz, then the currents move away from the entire cross section and towards the outer surface of the conductor. The higher the frequency, the more pronounced this becomes. So for a given wire size, the wire can carry more DC current than a high frequency signal of the same power delivery without power loss.) This is why "fat" braded wires are sometimes used as the bonding "wire" of choice. This is also why VOR's use one type of coax, and txponders use another, and GPS's use yet another...depending on how long the coax wire run needs to be.
Hope this helps...
jjconstant
Well Known Member
Thanks!
Very clear explanation Noel. Thanks. I love this site and the continuing education from generous, knowledgeable folks.
Jeremy
Very clear explanation Noel. Thanks. I love this site and the continuing education from generous, knowledgeable folks.
Jeremy
zkvii
Well Known Member
Re-activated old thread. Myself and another 7A are finding our 430 is fine in normal weather, but if in cloud or rain we get significant static on the coms side. Static wicks would seem the 'obvious' solution, a few questions:
Any body else having rain/cloud related static issues on a 430?
How many / which surfaces make sense? Ailerons, Elevators, Rudder? All - that is 5+ wicks
Any home made wicks - at US$60 each from spruce seems pretty high for us non-certified users
Thanks,
Carl
Any body else having rain/cloud related static issues on a 430?
How many / which surfaces make sense? Ailerons, Elevators, Rudder? All - that is 5+ wicks
Any home made wicks - at US$60 each from spruce seems pretty high for us non-certified users
Thanks,
Carl
