How to handle a bad magneto?

[JDHelicopterPilot]

The noise/shuddering and yawing is one or more dead cylinders. It's common and the fix takes 10 minutes tops and is pilot level maintenance. Step 1, pull plugs, Step 2 clean plugs, Step 3, reinstall plugs IAW maintenance manual. Your CFI's should be able to do this. If they can't they should be ashamed of themselves when they ask the mechanic to do it for them. If cleaning the plugs does not solve the problem then the aircraft should be grounded and inspected to find out what is going on as it will be a very serious problem if ignored.

 

That may be a preventive maintenance function. Of which you would be correct a pilot can perform. However, most companies, including flight schools do not allow pilots to perform preventative maintenance. Those that do, limit it to perhaps adding oil.

 

Once you get into Part 135 the pilot can not do anything. In fact, the FAA just started to allow pilots to remove, update and install GPS FAA cards. In the past this had been thought of as a maintenance function.

[JDHelicopterPilot]

The differences are plenty between car and aircraft/helicopter spark plug replacement. Aircraft have delicate screw-on plug leads that can crack easily if over tightened, the 'cigarette' of the lead should be cleaned with MEK and then a very thin coating of dielectric grease applied during assembly. The plug itself has a copper gasket that should either be annealed B4 re-use or discarded and a new one installed. Cleaning of the plug requires de-greasing, any lead deposits 'chipped' out, and then media blasted, gap re-set and checked on a spark plug testing machine. Then upon installation a very thin coating of anti-sieze compound or spark plug lubricant applied----keeping in mind that this compound will most likely contain graphite and will short out the plug if any is allowed to get near the electrode, then there is the final installation at the correct application of torque with a recently calibrated torque wrench.

 

 

I would not recommend a pilot take on this task without haveing done it a few times under supervision of a mechanic, and it is not a 10 minute job,, more like 2 hours, and then there is the operational check and the logbook entry.

 

Oh, and i forgot to mention to keep track of which cylinder and position each plug came from, this is for 2 reasons, (1) any abnormality of color/oil/condition can be easily traced to the problem cylinder/lead/magneto. (2) the magneto is an AC generater and fires different polarity thru it's rotation, so to get optimum life out of the plugs, we will want to 'rotate' the plugs (reverse their polarity) every 50-100 hours or thereabouts, so that the electrodes wear evenly.

 

I am glad you posted this. Changing the plugs is a much bigger thing than what most would think. I used to work along side the mechanic at the flight school I worked at. Mostly so I could learn a little more but also to give him a hand.

[Guest pokey]

 

And, if you drop a spark plug, it is scrap, marked and disposed of!

 

and the popular plug for helicopters are the Champion iridium at a cost of just about one hundred bucks each ! & your 4 cylinders use 8 of these, so don't drop them.

[Rogue]

Not only that but most often I've found spark plugs in cars normally torques to 15 or so foot-pounds while aircraft are around 35 foot-pounds.

 

Retired mechanic's two cents worth... I wouldn't want most CFI's I've met even changing a light bulb on an aircraft.

[Counterrotate]

Not only that but most often I've found spark plugs in cars normally torques to 15 or so foot-pounds while aircraft are around 35 foot-pounds.

 

Retired mechanic's two cents worth... I wouldn't want most CFI's I've met even changing a light bulb on an aircraft.

That s