Mechanical Failure - PA-44

Lands Like Brick · Post by **Lands Like Brick** » Sat Sep 24, 2005 7:47 pm

Would any AME's or pilot in general have any idea to what the following probelm would be:
everything was normal. after a brief shutdown for lunch. went back to fly home and the master wouldn't ever turn on. after further inspection the positive Post on the battery melted. there were no circuit breakers that popped. all guages were green...the plane was running fine prior to the malfunction.

any insite would be helpful

FREEFALL · Post by **FREEFALL** » Sat Sep 24, 2005 7:52 pm

Maybe a squirell or chipmunk chewed a wire?

bizjet_mania · Post by **bizjet_mania** » Sat Sep 24, 2005 7:55 pm

Had a problem with the PA44 in Quebec City today. Battery was dead when I turned on the master to check fuel quantity gauge. (overnight in Quebec City). Tried doing an external start but the power supply didnt have enough juice. Had AeroPro charge the battery and we got the engines started, but when doing the runup at 1800RPM the left alternator circuit breaker popped out and the right spiked to 60. Eventually after the third time trying to start the engine with the mechanic the battery was dead so we finally got a proper external power to start and then he pulled out each alternator circuit breaker (one by one) and i let it sit at 1500RPM for about 5 minutes until the alternator was at normal levels and properly charging the battery. We did seem to have alittle corrosion on the battery posts, that maybe one of the factors to ur melting, but im not sure

Lands Like Brick · Post by **Lands Like Brick** » Sat Sep 24, 2005 8:00 pm

we had spoken to a AME, he wasnt much help he said just to pull the battery, and have it recharged. that didnt happen because we couldnt even get the positive lead off. it was surrounded with the metal from the post around it. had to boost it with an esso truck and just taxi it over to the nearest hanger and have the AME look at it on monday, also the started on the left engine wouldn't disengage. took about 45 mins just to start the left engine. nothing like .7 on the round and .3 on the air

Pratt Punk · Post by **Pratt Punk** » Sat Sep 24, 2005 8:14 pm

Have you had a AME look at it? Any battery problems in the past? Could be a simple fix or something more serious. Kind of hard to determine without seeing the aircraft or knowing the history. Good luck.

Demosthenes · Post by **Demosthenes** » Mon Sep 26, 2005 11:47 am

I thought the PA-44 needed 2000 RPM to produce full amperage with the alternators?

D.

Bede · Post by **Bede** » Mon Sep 26, 2005 12:10 pm

Could be an internal short in the battery. Also check diodes (if there are any in a PA44)

Mitch Cronin · Post by **Mitch Cronin** » Mon Sep 26, 2005 4:21 pm

"the positive Post on the battery melted"
"also the started on the left engine wouldn't disengage."

...could be a relationship here, no?

CID · Post by **CID** » Mon Sep 26, 2005 6:09 pm

A short circuit severe enough to melt a battery post would have to be somewhere between the battery post and the first contactor it hits, or like mentioned before, through a shorted high current device like the starter or an internal battery short.

Don't bother looking at stuff that is protected by a circuit breaker until you look at the primary distribution circuit.

It might be right at the battery box. check to see if the battery wire has been stressed. If it's nice and pliable then its OK and it may indicate the battery box which is isolated from the wire with a grommet. If the wire shows signs of stress, like stiffness and a crackling sound when you bend it or discolouration, then it might be downstream from the box.

Make sure all the stressed wire is replaced. If not, it is more prone to corrosion and increased resistance and will make the entire electrical less efficient.