What’s the best way to really test a mag?

I often hear from U.S. mechanics that in their opinion the only way to really test a mag is to do it while flying. They say that’s because you can really get the highest rpm, say 2,550, and then do a left/right check as I normally would do at 1,700 on the ground.

I’m not sure about this. Please comment.

Ken Tomsett

London, England

Ken, it’s nice to hear from someone from London. I’ve spent many pleasant trips in the UK and would enjoy a lovely dish of Bubble and Squeak right now.

The subject regarding magneto drop-off is well covered in Lycoming Service Instruction 1132A, which is dated Feb. 2, 1968. As you can see it’s been around for a long time and is still an active and current publication today.

To my knowledge, this Service Instruction is recognized and used by all airframe manufacturers unless their specific Pilots Operating Handbook (POH) states something different. If that’s the situation, then the airframe manual or POH always takes precedence over the engine manufacturer’s publication.

Regardless of what you may have heard, it’s always best to read and follow the manufacturer’s publication that addresses the subject if for no other reason than you can always refer to it should anyone ask where you got your information. You’ll have to admit that’s a lot better than trying to explain to someone that you heard it from some guy while sitting around enjoying coffee or tea at the airfield on a rainy afternoon.

Should you require a copy of Service Instruction 1132A, contact CSE Parts Supply Ltd. at the Oxford Aerodrome. I’m certain they could provide a copy for your reference.

I have a new HIO360A1A engine in a helicopter. Is there a procedure to follow to correctly run the engine in or break the engine in? Someone told me that with the blades engaged, starting with a low rpm, run the engine for so many minutes through max rpm and then reverse the procedure. It sounded complicated enough to me to email you and get the right answer.

Wayne Moore

via email

Wayne, this may sound somewhat complicated to you, but if you take advantage of the current publications from Lycoming regarding this subject it may not be as difficult to do it properly as you might think. The current Lycoming Service Instruction 1427B, Part II, covers the subject quite well for horizontal engine installations only. From the engine model you provided this would apply to you.

I’d also suggest you check your airframe manufacturer’s recommendations regarding this subject. I’d also recommend if you do not have the Lycoming Operator’s Manual Part Number 60297-12 you give serious consideration to getting a copy of it. It’s got excellent information in it and provides specifications for several individual 360 series engines.

Any publication like operator’s manuals, parts catalogs, etc., may be ordered directly from Lycoming by calling 570-323-6181 between 8 a.m. and 5 p.m. Eastern time. Be advised that Lycoming does not provide individual copies of Service Letters, Service Instructions or Service Bulletins. You can access some of them at Lycoming.Textron.com.

Paul McBride, recognized worldwide as an expert on engines, retired after almost 40 years with Lycoming. Send your questions to: AskPaul@GeneralAviationNews.com.

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