C 172 aileron cable rattle =RFI ?
 

We have a problem with our Cessna 172.... In the climb, under full power, the radio is all crackles, which can be stopped momentarily by waggling the ailerons. During the cruise, at reduced power, the RFI is not present.


I am used to doing positive rigging checks on gliders, where someone holds the opposite aileron whilst you push and pull the aileron on your side.
Whilst doing this to our Cessna, there appears to be about 1 inch of slack between the pair.


What I think is causing this Radio Frequency Interference is the aileron cables chattering against the airframe, or each other.


Has anyone encountered this problem before, and what is the solution?

Get your maintenance to re-rig and retension your aileron cables

Sounds like you have two problems....low control cables tensions and bad bonding (probably broken bonding leads). Stop flying and get it fixed as it could be indicative of a more serious flight control issue such as cables off pulley etc.

If you have the removable strip in the headlining you should be able to access the centre part of the aileron cables. get a tensiometer and measure the tension. It should be around 30lbs. That's a ball park figure, you will have to compensate for temperature and adjust the turnbuckles accordingly. If it overly slack, you will have to check the pulley runs. Does it have an autopilot? The servo is on the right wing and there are extra cables from the servo to bell crank.

With regards to your radio interference, you should also be able to access the coax plugs to the VHF com antennas through the same access panel. Have a look, disconnect and squirt some contact cleaner. Failing that, it could be a bonding problem as mentioned earlier.