Static Dischargers
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Static Dischargers
Does anyone have any info on when (and how) static dischargers are inspected. I see some 'functionality check' that occurs at long intervals. Also of course visually at preflight and postflight (etc.) checks.
Are they generally checked for being attached properly / securely at any maintenance check?
I am talking about commercial airplanes - I Googled but found little or no info.
Long story, had one fall off an airplane and it was found on an airport FOD check......
Thanks for any input (be nice now...)
Are they generally checked for being attached properly / securely at any maintenance check?
I am talking about commercial airplanes - I Googled but found little or no info.
Long story, had one fall off an airplane and it was found on an airport FOD check......
Thanks for any input (be nice now...)
I think they are On Condition during routine operations with scheduled bonding checks during heavy inputs. The CDL will allow several to be missing, but for instance Airbus advise replacing any missing wicks asap.
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static wick inspections on the airbus were carried out during C check inputs. These could be up to 24 months apart. Inspections included a visual check for obvious damage, an insulation resistance check from tip to structure and a bonding check from base to structure. Replacing wicks or bases that failed these tests.
I remember a check item for bonding, i.e. 0.003 ohms from the base plate to the mounting surface, and then a Megger check from the base to the metal tip. Failure of either was a replacement as required.
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Typical wick needs some resistance to work. 6 -100 Meg Ohms is the norm from its base up thru the wick or tip. This allows buildup and rapid discharge of static charges.
They are for P-Static (radio crackle noise) dissipation, not lightning protection even though they usually get the brunt of lightning exit point.
They are for P-Static (radio crackle noise) dissipation, not lightning protection even though they usually get the brunt of lightning exit point.
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Remember several years back (A300), much radio static was written up and some type of 'skin mapping' was carried out. Not 100% in the loop (obviously...
), but seems like there was talk of some huge amount of electricity being somehow passed over the skin in the test. Surely wicks were involved in this test. I know, I know - if all else fails - Google it - just talking out loud. 
), but seems like there was talk of some huge amount of electricity being somehow passed over the skin in the test. Surely wicks were involved in this test. I know, I know - if all else fails - Google it - just talking out loud.
slowto280.
An A300 we had a Channel Express had a lot of precipitation static particularly on No.2 VHF com. Lots of work was done to try and fix the problem including bonding checks, new static wicks, re-paint of composite panels and fairings, new antenna.
It got better but I don't think it went away completely.
An A300 we had a Channel Express had a lot of precipitation static particularly on No.2 VHF com. Lots of work was done to try and fix the problem including bonding checks, new static wicks, re-paint of composite panels and fairings, new antenna.
It got better but I don't think it went away completely.
Several years ago, we had a Citation 550 in our fleet that experienced a complete loss of COM radio functionality whenever flying in visible moisture. (Especially snow). A loud hissing noise was heard in the radios that would drown out all incoming transmissions.
We replaced all static wicks, reworked the mounting plates etc, all to no effect. We finally took the aircraft to the Citation service center at KSWF, who had a machine to emulate the static charge conditions found in flight. It was a high-voltage generator, that connected to an insulated wand that was passed over the skin of the aircraft from nose to tail, while a tech inside of the aircraft monitored the COM radios.
The test quickly pinpointed the radome as being the source of the problem. The aircraft's original radome had been damaged in a towing accident, and a rebuilt radome fitted, shortly before we took delivery. It turned out that when the radome was rebuilt, the overhaul facility missed a critical step, and as a result, the 6 static diverter strips embedded in the fiberglass had no physical electrical connection to their airframe bonding pads. Once that was corrected, never had a problem with p-static again.
The skin mapping machine at the service center required a great deal of care and training in operation, as it apparently generated lethal amounts of high voltage.
At my current employer (Part 91 corporate) our aircraft have a 12-month inspection requirement for static wick bonding and resistance checks. It's not unusual to find one or two (out of 16) that fail the resistance checks during the inspections.
We replaced all static wicks, reworked the mounting plates etc, all to no effect. We finally took the aircraft to the Citation service center at KSWF, who had a machine to emulate the static charge conditions found in flight. It was a high-voltage generator, that connected to an insulated wand that was passed over the skin of the aircraft from nose to tail, while a tech inside of the aircraft monitored the COM radios.
The test quickly pinpointed the radome as being the source of the problem. The aircraft's original radome had been damaged in a towing accident, and a rebuilt radome fitted, shortly before we took delivery. It turned out that when the radome was rebuilt, the overhaul facility missed a critical step, and as a result, the 6 static diverter strips embedded in the fiberglass had no physical electrical connection to their airframe bonding pads. Once that was corrected, never had a problem with p-static again.
The skin mapping machine at the service center required a great deal of care and training in operation, as it apparently generated lethal amounts of high voltage.
At my current employer (Part 91 corporate) our aircraft have a 12-month inspection requirement for static wick bonding and resistance checks. It's not unusual to find one or two (out of 16) that fail the resistance checks during the inspections.
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Sometimes when a radome is painted, the paint in the attaching screw holes insulates the diverter strips to the airframe. Removing the paint restores the bonding. In Papua New Guinea it was easier to replace all the static dischargers at one time to get rid of static. And of course , correct anti-static paint.
