Magneto overhaul

[mike newall]

It is a Service Bulletin, therefore is not a mandatory requirement.

I hear what others are saying and there are always logical reasons to consider it, however, if the magneto is in good condition, operating well and without indications of any problems, why add to the already extensive expenses we suffer from insurance, fuel, hangarage and fees various ?


If you conduct searches, there is much legal debate regarding this and more than one law firm has determined that a Service Bulletin, unless incorporating an Airworthiness Directive is not considered mandatory, however all caveats suggest that due diligence is observed.

[dmcnicholl]

Thank's Mike, I'll have a hunt though I have found and downloaded TCM SB643B.

I've owned my aircraft for 17 years and barely gave the magneto a thought since the engine usually started on first blade and ran well. 4 years ago that started to change and I eventually sent the mag off for overhaul, but it came back with a 'life', 4 years or 500 hours. That 4 years will be up in 2014 so it would be nice to be able to make the argument that pulling it off the engine and shipping it away for a £500 inspection is not necessary.

[Lewis]

Couple of things for others to consider. You won't know if your mags are failing if you do nothing! By failing I mean pitted contacts, worn cam, degrading coil, worn bearings, leaking seal, loose electrode, broken damaged gears, degrading condenser, damaged rotor, worn out impulse coupling pawl pins etc etc etc. Just because the engine is running "fine" it doesn't mean the mags are "fine"! Reference the "Official statement" in EASA land the manufactures word is the official one. Just because the LAA doesn't recognise the 500hr inspection on magnetos doesn't mean your mags will go on running forever. The mags don't know what they're fitted to either certified or permit aircraft. In the case of Slick 4001 series these should be replaced after 900hrs/10 years. For Slick 4200 series mags these should have had new distributor block assemblies by now as the carbon brush will be worn and coil tab will be showing signs of wear. Finally any Bendix mag, lots of parts, lots to go wrong especially ageing distributor gears. If they're getting darker in colour they're suffering heat degradation, end result breakage and loss of the mag. These are just a small proportion of issues with the common types of mags. when it comes to the older BTH mags, please keep a good eye on them. When was the last time you had the harness cap off the back of the mags or tested the resistance of your plugs? Simple inspections on an annual basis can help prevent a major failure.

[rogcal]

I've read this thread with interest over the last few months and agree totally with what Lewis has to say on the subject.

Condensers and coils degrade over time and although the falling off in efficiency is not usually detectable during operation over the years, they will eventually fail.

I often ask myself how much more attention people would give to a magneto fitted on their engine if it were the single means of ignition instead of having two!

[dmcnicholl]

I often ask myself how much more attention people would give to a magneto fitted on their engine if it were the single means of ignition instead of having two!

Like on my RF3, you mean, or indeed any of the Fournier singles? Not sure if the 2 seaters have one or two mags.

It's a point of view I suppose but for sure if I have a problem with my single mag there's a good chance I won't get it into the air to cause myself embarrassment. And before you berate me as a luddite, mine was overhauled 3 years ago.

[mike newall]

With any suggestions and guidance comes caveats.

If - you are doing 200 hours per year, as my Brother is in his Cub Cruiser, then a 500 hour overhaul/inspection is probably a waste of money.

If you are doing 20 hours a year, then common sense would say that at 500 hours - OMG, your mags would need some looking at.

I stated that the premise of a 500 hour inspection/overhaul was a service bulletin and not a mandatory occurrence assumed that logic would prevail.

Perhaps that was missed.......

[ThePipster]

With any suggestions and guidance comes caveats.

If - you are doing 200 hours per year, as my Brother is in his Cub Cruiser, then a 500 hour overhaul/inspection is probably a waste of money.

If you are doing 20 hours a year, then common sense would say that at 500 hours - OMG, your mags would need some looking at.

Sorry Mike I don't follow your logic, mags rotate, the more they rotate the more they wear, 500 hours is a finite number of rotations.

Phil

[Lewis]

Just to clarify that the 500hr inspection is by no means an 'overhaul'. Whether Bendix or Slick the general Inspection is the same. The rear case is removed, all items inspected and tested IAW the manufactures service manual then reassembled and tested. An overhaul requires a complete disassembly and specified parts replacement.