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Aircraft Prepurchase/Prebuy Inspection and Magnetos – Buyer Beware!

The purchase of an aircraft isn’t as simple as kicking the tires and taking a test flight.  Most aircraft have a significant dollar value to the buyer and seller.  The value of the airplane is directly affected by the sum total of the state of repair of all of the airframe, powerplant, and a myriad of installed equipment.  To verify the value of the airplane, dozens of “good-bad” assessments of the operating condition of the plane must be made.  These assessments are based upon not only the physical inspection of major components but also the condition of the supporting accessory components.

Buried in the powerplant package are the magnetos.  A simple observation may be to run the engine, flip the mag to left and right to see what the RPM drop is and how the engines run on the individual magnetos.  If the magnetos are working, they are working, if the engine runs, it runs.  Right?

Well, maybe not so simple.  While the magnetos may pass a basic engine run-up inspection, there are lots of not so obvious logbook records for required maintenance which keeps the magnetos in good operating condition.  New airplane owners may get hit with “catch up maintenance” to the tune of thousands of dollars if the inspection and Airworthiness Directive compliance of the magnetos require attention.

It is a certainty that various maintenance issues will be identified during the inspection.  Repairs will either need to be done or inspections may be due at some point after the purchase of the plane.  These issues are not likely to substantially affect the purchase price of the airplane unless particularly expensive or of negative impact on the operation of the aircraft or engine. 

Ultimately, the prepurchase inspection benefits the buyer to know what maintenance requirements are upcoming for the purposes of budgeting and scheduling maintenance.  If money needs to be spent after buying an airplane to correct maintenance issues, better to know this upfront.  As the saying goes “better to be advised than surprised!”

LOGBOOK DIVE

The very first step is to confirm that the magnetos installed on the engine match the logbook entries.  No surprise, but logbook records can be messy and entries to record installation and removal of magnetos may be incomplete.  

A common scenario is that a magneto was installed in a hurry and the work was never recorded in the logs.  The result is that the serial numbers of the installed magnetos actions of Airworthiness Directive compliance and 500-hour inspection in the logbook will not match the unrecorded, but installed, magneto.  Verify the installed part number and serial number and then review the logs to match to required or recorded maintenance events.

Regarding maintenance events, magnetos will have some fundamental inspection points which should be recorded in the logbook:

  1. Airworthiness Directive Compliance
  2. Service Bulletin Compliance
  3. Calendar Time Overhaul 
  4. 500 Hour Inspection

AIRWORTHINESS DIRECTIVE COMPLIANCE/SERVICE BULLETIN COMPLIANCE

The logbooks may have a list of Airworthiness Directive AND Service Bulletin compliance, but is the list complete and accurate?   The ADs and Service Bulletins on Bendix and Slick mags are too numerous to list in this discussion and should be researched for current effectiveness (Powerup magnetos do not have any Airworthiness Directives, so a much shorter discussion!).  

Surprisingly, a complete listing for ADs for both Slick and Bendix may not be found by searching the FAA or magneto manufacturer databases.  Some ADs are only found when searching on the engine model, and in some cases, the magneto AD is against the airframe (!!).  Of note, one Slick Airworthiness Directive, AD 88-25-04, is applied against the airframe and requires instrument panel placards and Airframe POH amendments.  A great example is that the deep dive into records may extend beyond the logbooks.

The bottom line with logbook AD records:  Trust but Verify.  It is likely that the previous mechanics have done the required work.  But, any mechanic working on an airplane and engine new to them will need to research and review that the magnetos match the records.

CALENDAR YEAR MAINTENANCE

All magneto manufacturers require an overhaul of magnetos based on calendar time, regardless of hours.  The idea is that a magneto that is not operated frequently is perhaps even more likely to experience service issues than a magneto operating 1,000 hours in one year.  

Bendix has a detailed Service Bulletin SB643C that details how some Bendix magnetos are subject to either a 5-year overhaul or 12-year overhaul, depending upon the serial number and model number specifics.  Both Slick and Powerup detail 12-year overhaul requirements in their manuals.  

The basic idea here is that, when purchasing an airplane with a low-time engine, the date when the engine was overhauled, may have some unforeseen implications.  The magnetos may have low operating hours.   But, the low operating hours’ overtime may trigger manufacturer requirements for inspections that could potentially incur a substantial expense for the new owner.   

THE 500 HOUR INSPECTION

The record of the 500-hour inspection may be the single most important record in the logbook.  The 500-hour inspection is a routine maintenance event that can be performed at any time during the service history of the magneto.  This inspection can be used to remedy Airworthiness Directive compliance and other inspection requirements if the magneto has an unclear service record. If the logbook shows no record of 500-hour inspections and the magnetos have more than 500 hours, then the inspection is due.

Consideration at the prepurchase inspection is to negotiate with the seller to complete the magneto inspection as part of the sale. Or, perhaps split the cost?  It is a relatively low-cost inspection, but the benefit is that both the seller and buyer are assured that the magnetos are back to a known baseline.  For the seller and buyer, the Powerup Aero 500-hour inspection provides a warranty for the magnetos and simply removes any post-sale liability concerns for the ignition system after the aircraft purchase.

If the seller is not willing to provide the 500-hour inspection, then the buyer should consider spending the money to get the inspection done.  Once again, the benefit is that the new owner can have Powerup Aero baseline the magnetos to a known condition.  With one less thing to worry about, the new owner can fly their new airplane with greater confidence that unplanned magneto maintenance will not keep them grounded.

Have Fun and Fly!

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