Static in headset with left rudder

M

MLC@PTK

Filing Flight Plan
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Jul 7, 2017
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MLC@PTK
I get static in my headset when we push the left rudder. It only happens on the ground and it does not seem to matter if it is pilot or co-pilot rudder pedal being pushed. It happens if I push rudder pedal with our without the brake above the pedal - makes no difference.

Anyone ever experienced this before? I am not sure where to start looking.
 
I would look for a loose wire in the vicinity of the rudder linkage. Something that gets pinched or moved when the pedal is depressed.
 
There should be a braided jumper wire between the rudder and vertical stabilizer. If that is missing, broken, or corroded, airflow over the rudder when turned to one side could cause static buildup.
 
You guys are super helpful, LOL!! I looked for the left brake switch but was unable to locate it!! Not sure if i can effect the Coriolis effect either!
I looked under the panel but could find nothing that looked suspicious. The Cherokee will go down for an owner assisted annual in the next couple of weeks. I am wondering if we will find something under the floor or in the tail as mentioned by Norman. Thx
 
Norman said:
There should be a braided jumper wire between the rudder and vertical stabilizer. If that is missing, broken, or corroded, airflow over the rudder when turned to one side could cause static buildup.
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Real hard to get static buildup when (as the OP said) did this on the ground only.

More to the point, and perhaps a bit more serious, is to inspect CAREFULLY the rudder cable from the left pedal all the way back to the rudder horn. I think that you will find that the rudder cable is scraping on a fuselage metal surface somewhere along the line. Why not in the air? Perhaps air loads on the rudder run the tension up JUST THE TINIEST BIT and now the cable doesn't hit that metal surface.

The order of engineering estimates: WAG (wild @$$ guess), EWAG (Educated WAG), SEWAG (Scientific EWAG), Rectorandom Estimate (just pulling an idea/value right out of your @$$). This is one of the latter.

Jim
 
Having a Cherokee myself, I'm interested. When you figure it out please update us on what you found. I'm assuming it happens while you're taxiing as you're not going to move the rudder very far sitting still.
 
weirdjim said:
Real hard to get static buildup when (as the OP said) did this on the ground only.

More to the point, and perhaps a bit more serious, is to inspect CAREFULLY the rudder cable from the left pedal all the way back to the rudder horn. I think that you will find that the rudder cable is scraping on a fuselage metal surface somewhere along the line. Why not in the air? Perhaps air loads on the rudder run the tension up JUST THE TINIEST BIT and now the cable doesn't hit that metal surface.

The order of engineering estimates: WAG (wild @$$ guess), EWAG (Educated WAG), SEWAG (Scientific EWAG), Rectorandom Estimate (just pulling an idea/value right out of your @$$). This is one of the latter.

Jim
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I defer to your superior knowledge of avionics. I was only suggesting he take a look at the jumper.
 
Does it do this at all headphone stations?
If you turn off the radios and only have the intercom on does it still do it?
If it does it with the radios on, does changing the squelch a bit higher have any effect?

Or perhaps some PoA style help:
Does it still do it if you press the left rudder pedal with your right foot :)
 
weirdjim said:
Real hard to get static buildup when (as the OP said) did this on the ground only.

More to the point, and perhaps a bit more serious, is to inspect CAREFULLY the rudder cable from the left pedal all the way back to the rudder horn. I think that you will find that the rudder cable is scraping on a fuselage metal surface somewhere along the line. Why not in the air? Perhaps air loads on the rudder run the tension up JUST THE TINIEST BIT and now the cable doesn't hit that metal surface.

The order of engineering estimates: WAG (wild @$$ guess), EWAG (Educated WAG), SEWAG (Scientific EWAG), Rectorandom Estimate (just pulling an idea/value right out of your @$$). This is one of the latter.

Jim
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Damn. That’s brilliant. I never even thought of passive intermod from a stupid cable rubbing on aluminum, and yet I’ve fought that crap on towers before. But what would be exciting it with RF such that he’d hear it in the receiver sitting on a ramp?

(Beating on crap on the tower with a broom stick seeing what makes noise in the receiver while trying to find someone’s broken piece of crap fiberglass covered vertical antenna — usually a colinear design that has decided to disassemble itself internally — is fun. Not.)

If they turns out to be his problem, I’m giving you a high five at OSH next year. Passive intermod is the devil’s snack food.
 
denverpilot said:
Damn. That’s brilliant. I never even thought of passive intermod from a stupid cable rubbing on aluminum, and yet I’ve fought that crap on towers before. But what would be exciting it with RF such that he’d hear it in the receiver sitting on a ramp?

(Beating on crap on the tower with a broom stick seeing what makes noise in the receiver while trying to find someone’s broken piece of crap fiberglass covered vertical antenna — usually a colinear design that has decided to disassemble itself internally — is fun. Not.)

If they turns out to be his problem, I’m giving you a high five at OSH next year. Passive intermod is the devil’s snack food.
Click to expand...

My first thought would be the transponder. It is the only semi continous RF emitter I can think, of other than TCAS, on the aircraft. The next time it is heard, might try putting the transponder in standby to see if it goes away.

If it is RF detection across a galvanic diode the bursts of energy from and the PRF of the transponder may be such to make it sound like static.
 
Well, the static is gone. The only thing the mechanic found is a loose hand held microphone jack. The nut was missing so i guess it was just flopping around. My guess is that left rudder was causing some sort of a short.
 
MLC@PTK said:
Well, the static is gone. The only thing the mechanic found is a loose hand held microphone jack. The nut was missing so i guess it was just flopping around. My guess is that left rudder was causing some sort of a short.
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Left rudder on the ground would cause sideways acceleration. A skid. That loose jack might have been shifting sideways and rattling in the panel a little, causing the static. In flight, while in coordinated turns, maybe not.

Maybe. Wild guess. Might be much more to the story.
 
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