Starter - IO-470

[455 Bravo Uniform]

I was AOG for about an hour due to no-start. Solenoid/contactor on firewall. Simple starter motor (no Bendix) attached to accessory case.

Symptom - contactor pulled in as hard as usual, but prop didn’t even try to budge. One of my trusted A&Ps suggested I tap the starter lightly with a hammer. It worked.

On old cars this worked usually because the solenoid or Bendix was sticking. Do you guys think it’s the starter motor? Broken winding or stuck/worn brush? And it just happened to stop at the perfect location?

I’ve removed the starter and sent to Aerotech in Louisville for rebuild.

By the way, a few years ago I replaced the contactor based on meter diagnosis, and a few years later the feed cable from it to the starter, again based on my meter.

 

[MountainDude]

Happened to me. Replaced the solenoid and no issues any more.

 

[Tools]

Usually that firewall mounted solenoid. Same thing here on the road with a o-470. Tractor supply and courtesy car to the rescue…

Sticking brushes in the starter are second on the list. Easy fix.

 

[bonefishpete]

Just jump wire the solenoid to test.
Stay away from prop. Sounds like the brushes are sticking worn out. 1950 technology.

 

[Tools]

I know it’s only 12v, but remember to clench your teeth.

 

[Dan Thomas]

Sounds like the brushes are sticking worn out. 1950 technology.

I have not yet seen a brushless DC motor in any starter. All of them are series-wound or permanent magnet affairs, meaning they have brushes.

Unless someone has come out with one since I retired eight years ago.

 

[Tools]

Well, to be fair there is a Conti 65 stc that uses a DeWalt cordless… ha!

To be fairer, don’t know if THAT uses the cool brushless ones… how do that even work?!!

 

[Bell206]

Do you guys think it’s the starter motor? Broken winding or stuck/worn brush? And it just happened to stop at the perfect location?

Can't offer much with no volt readings at time of failure and the starter gone, but yes their can be a "dead" spot on a DC motor. However if you also wiggled a few wires or tapped the solenoid prior to it starting there could be other issues out there that caused this. Perhaps while waiting for the starter to come back, connect the starter wires to a landing light bulb or other device that can pull a slight load and check your voltage drops, etc to see if anything amiss? And don't forget the ground side as well.

 

[Dan Thomas]

And don't forget the ground side as well.

Yes. Often overlooked in starting issues is poor engine-to-airframe grounding. When oneis dealing with hundreds of amps, a tiny resistancemeans a big voltage drop.

Another factor here might be a slipping clutch in the engine. It's part of the reduction gearing in the accessory case.

 

[GeorgeC]

Tractor supply and courtesy car to the rescue…

IYKYK