M20J A3B6D -> A3B6 conversion considerations, Slick magneto maintenance + MT props

[Martin S.]

Gents,

does anybody know the overhaul and maintenance intervals for the A3B6 slick 4370/4372. The bendix dual mag (on my A3B6D) needs overhauls every four years. Do the slicks need less maintenance? (Trying to evaluate whether the conversion will lower my magneto maintenance bills in the long term)

As far as I understand there should be no issues running an MT three blade prop on the A3B6 after conversion. Am I overlooking something?

Many thanks,

Martin

[EricJ]

In the US there is generally no difference between the Slick and Bendix or Bendix dual mags for maintenance intervals.   Broadly speaking, for Part 91 (our private general aviation use), there are no maintenance intervals other than "on condition".    Many/most people observe the 500-hour and overhaul intervals just because they're generally a good idea with magnetos.    I don't know of any four-year time interval requirements or even guidance for any magneto.

 

[KSMooniac]

The dual mag needs inspections every 500 hours, not overhauls every 4 years. Big difference.

Slicks are generally throw-away after 500 hours, if they last that long.

You might investigate electronic ignitions instead, although I doubt many have been installed for a full 2000 hour run thus far.

MT props are STC'd for our engines and I've been very happy with mine.

Sent from my motorola edge plus 2023 using Tapatalk

[Martin S.]

18 minutes ago, KSMooniac said:

The dual mag needs inspections every 500 hours, not overhauls every 4 years. Big difference.

Slicks are generally throw-away after 500 hours, if they last that long.

You might investigate electronic ignitions instead, although I doubt many have been installed for a full 2000 hour run thus far.

MT props are STC'd for our engines and I've been very happy with mine.

Sent from my motorola edge plus 2023 using Tapatalk
 

As far as I understand the overhaul requirement originates from SB643B.

[KSMooniac]

Nothing in that SB indicates you must overhaul it every 4 years, only when the engine is overhauled.  There are periodic INSPECTIONS, but not overhauls.  Big difference.

[EricJ]

13 hours ago, Martin S. said:

As far as I understand the overhaul requirement originates from SB643B.

Also, Service Bulletins are not required to be followed in the US for Part 91 unless they're part of an Airworthiness Directive.

[philiplane]

Compliance with all manufacturer's instructions, including SB's, is required by many authorities outside the US.

From SB643B:

1. In addition to the requirements listed above, magnetos must be overhauled or replaced at the expiration of five years since the date of original manufacture or last overhaul, or four years since the date the magneto was placed in service, whichever occurs first, without regard to accumulated operating hours.

Edited Thursday at 03:27 PM by philiplane

[Guillaume]

1/ SB643B is obsolete and has been replaced by SB643C many years ago (D2000 / D3000 mags are no longer included) 

2/ For European aircraft maintained under Part-M light, aircraft owners may choose to deviate from TCH recommendations (including SB).