Series start, bleed air circuit breaker pops

[schrambow]

Just curious if anyone here has had this happen.
Doing a Series start on either engine, about 80 percent through the spool up.  The bleed air circuit breaker pops, and then i can feel a rush of air in the ventilation system.  I push it back in after the engine is running and the starter is disengaged and it works fine. I then use the parallel on the last engine and the start on the second engine is normal and the bleed air system works fine.
Pretty much every time i do a series start it does this now.  Obviously, this isn't normal and it needs some attention, just wondering if someone ever had this happen?

[donv]

That sounds to me like some 48v electricity is getting to where it shouldn't, and I would be very concerned about that.

According to my 980 book, the bleed air valves are powered through distribution bus #1.

I'd be worried about a short somewhere.

Did you train with Barry Lane? I would ask him what he thinks. Of course, asking Barry is my default answer for any question, these days!

[donv]

At 60%, I believe the electrical system should return to normal-- the series start relay opens. So I would guess you are getting a surge of power right then for some reason. I would certainly look into it.

[Bruce Byerly]

Hi Corey,

Unsure of the issue though we are seeing more voltage leaking from bad cannon plugs these days but I guess I would ask why do series starts unless you’re stuck outside and extremely cold soaked in the frozen tundra?

[schrambow]

that true, i just did a parallel start yesterday and it was 90 degrees outside and the ITT's were basically the same as a 70 degree day during the start sequence.  I always thought in the above 85 degree day to use the series start but after yesterday's parallel start,  that appears to be a waste on the batteries and system for no benefit.  Therefore, i should wait until the Tundra gets frozen up here before using the series start again.