Loose starter

[TomJ]

Last Sunday, my DA40 wouldn't start when when I was set to return from KHIO in Oregon to San Jose, CA. Instead, the starter just made a horrible noise. The FBO where I was parked couldn't initially get a response from any of their mechanics late on a weekend, so I looked for any other mechanics on the field, while simultaneously looking for Southwest flights and wondering whether to fly back that night or to stay until the next morning to deal with this problem. Luckily there were two people at Northwest Aircraft Maintenance who just happened to be in on Sunday doing paperwork. They came over and diagnosed the problem, and this is what they found:

The starter (Skytec LS), which I had replaced just last June (10 months ago) is suspended below a mounting plate with four bolts. All four bolts had come loose (!) and one of the forward ones had actually fallen off somewhere! This caused the starter and its pinion gear to drop enough to not properly engage the toothed flywheel on the engine. The maintenance guys tightened the remaining bolts enough to give me "two good starts", and I was off.

The main purpose of this flight was to fulfill one of the commercial certificate experience requirements: the “solo 300 nautical mile with three stops" requirement. Luckily, there was a massive 30-50 kt tailwind almost all the way back so I landed at Redding and Livermore without shutting down the engine and made it back to San Jose before dark at an average ground speed of 155 kts.

There was no damage to the starter but some slight abrasion/shininess on the engine flywheel gear teeth, which has been cleaned off.

To be clear, this wasn't a safety risk, just a nuisance issue. It's also comforting (somewhat) that this wasn't a design or manufacturing flaw but most likely an oversight by my mechanic who installed the starter last year, although he said he would be really surprised if he had not tightened those bolts. He also said that when he first installed the starter, he had noticed that the star washers that came with the starter were a type he had not seen before, and these have now been replaced with the lock washers he normally uses.

Other than simply forgetting to tighten those bolts during installation, what else could cause all four of them to get loose? Anyone have a different hypotheses?

Thanks.

[Steve]

Reviewing the photos from my starter exchange, there are 3 nuts (studs in the crankcase) and one bolt affixing the starter to the engine. They all have lock washers, but I can't tell what type. Additionally, there is a safety-wired bolt attaching a bracket to the drive housing on the front of the starter. I would bet that they weren't torqued to spec to loosen that much that fast...

Steve

[dafzero]

That is a seriously clean engine. Well done.

[Steve]

That is a seriously clean engine. Well done.

Well, that was in 2009...



Steve

[Charles]

Maybe it just happens?

In this year's annual, they found that one of the screws on the starter had become loose so they removed it, changed the brushes and plastic housing, and put it back in. No explanation as to why a screw that had been in place for 14 years and 1600 hours came loose this year...

[TomJ]

Thanks, Steve, for the pictures. The configuration of three studs and one bolt (that fell off) is quite different than I'd envisioned.

I was curious - what made you take the pictures - is this something you do routinely? This makes me convinced that I should be doing this too, and in general staying more informed about the state of my airplane. Indeed, I hadn't seen the airplane with its cowling off since Chris B (also on D.A.N.) helped me with an oil change more than two years ago after we flew the airplane here from North Carolina.

Chris - whom I met on this this forum - coached me through aircraft selection and the pre-buy inspection, and even flew the aircraft back here with me as eager co-pilot/new-owner trainee! And as we all know, Chris is a frequent contributor of useful and well documented information here as well.

Charles, it doesn't seem likely that *three* nuts and a bolt all coming loose in such a short time was just ordinary wear. I should add that my airplane mechanic, who has an excellent reputation on this airfield, took ownership for these fasteners coming loose.

[Steve]

Tom:

I do most of the mechanical work on my airplane, with appropriate oversight (and sign-offs) by my A&P/IA (who works from the hangar around the corner from mine). I do take "close out" photos on a routine basis to document the configuration/condition of the airplane. This is something that is done routinely in the aerospace industry, and I think it is a good idea even for our puddle-jumpers.

Steve

[smoss]

Pics are also helpful after replacing something to prevent the dreaded next day, after the cowling is back on, "uh oh, did I remember to put that little thingamajiggy back on?!"

[creativewebz]

I had the exact same issue with my plane today! 2 out of the 3 nuts were loose, andthe bolt is missing. where did you get a new bolt, or did you have the part number?

[Steve]

Grant:

Was yours the original starter, or had it been replaced? There was some intimation in the earlier thread that the replacement starters were shipped with a different type of lock washer. I cannot recall on mine whether they were different. I may be putting a stripe of witness paint on my starter hardware next time I have the cowling off...

Steve