Thursday, April 13, 2006


Tuesday night, MS and the IFR Pilot meet at the hangar to take 78S out for another flight. (It appears that possession of the 396 has inspired MS to stop spending time with his son and spend time with his new baby -- the 396, of course.) MS begins the preflight and almost immediately announces that something is wrong. The IFR Pilot, always attuned to MS's BS, denies the condition . . . until he checks for himself. See if you can spot what's wrong in these pictures, taken after we removed the cowl for a "closer inspection."

Needless to say, 78S is grounded until the mechanic replaces the alternator bracket arm and the carb heat brace. He reports that the bracket securing the alternator to the engine block also broke. He says he's never seen anything like it before.

Thank goodness for the safety wires, which seem to be all that was holding the alternator in the vicinity of the engine. Had it fallen out, the IFR Pilot's Monday evening flight could have become quite an adventure. Perhaps it's time to hire the CFI for an afternoon of emergency procedures refresher training.

One concern was that the alternator belt has been damaged or stretched-out and needs to be replaced. That, of course, requires that the spinner and prop be removed. While the mechanic -- who gets paid by the hour -- would no doubt like that, none of us -- who pay those hourly bills -- really wants that. Thankfully, in this morning's phone call, the mechanic report that he didn't think replacing the belt would be necessary. And, the new bracket arm is only .5 AMU. (AMU = "Aviation Monetary Unit" = $100. Didn't think you could get a new aviation part for less than 1 AMU. Go figure...)

JS was there with us, checking out the 396. So, MS took advantage of the flight cancellation to hold an little impromptu seminar on the features of the 396. Here they are in all their glory:

(Yes, I know, neither of them are as handsome as the IFR Pilot. But whatcha gonna do?)

Stay tuned tomorrow (hopefully) for videos of MS's landings at BKL and the Home Base from last Sunday evening -- when we still had a working alternator!


John said...

I scheduled maintenance for a flying club for nearly 3 years and I learned quite a bit in the process. I can't resist kibitzing here.

A good question to be asking is "What is the source of the vibration that caused these cracks and failures?" I hate to say it, but the prop may be the culprit. I'd check the prop spinner very carefully and even remove it and check the spinner bulkhead. You might find more signs of unwanted vibration.

If it were my plane, I'd consider removing the prop and having it balanced while the alternator belt is replaced. Weigh the cost of this versus doing more vibration-related repairs down the line.

Of course it's easy for me to say this because it will have no financial impact on my finances.

IFR Pilot said...

Funny you should mention that, I asked the mechanic at annual to have it done. Said someone else on the field was having it done and ours would be done at the same time. Well, clearly it wasn't. So now we're gonna get it done at a shop that's not too far from the Home Base. We'll keep you all updated on the results.

Anonymous said...

With modern technology, they can balance the prop dynamically on the aircraft, so no removal necessary, unless you want to balance it statically, which is not as good.

Aaron DeAngelis said...

Aviation Monetary Unit. That is so cool. That is my word(s) of the week.

I hope '78S has a speedy recovery!

jsparks said...

We had the prop balanced on our Cherokee at your/our home base for $150.00 and it really does make a difference. The guy comes out and does it right there. I think I told you about it, but noone got back with me to set it up for you.