Jump start PA30B

[Robert Solymossy]

As a recent new owner of a 1967 PA30B, I am wondering what is the best way to jump start in case of dead battery. From what I found so far, I was told the nose cowling plug only powers the instruments and bus (bypassing the battery) and should not be used to try to jump start. Is this true? Well, in that case, how do you jump start?
Thanks in advance.

[Charles Schefer]

I have a 1968 PA-30B. In my aircraft the external power port on the nose cowl has a positive lead that ties directly into the main solenoid such that when the master switch is turned on the solenoid connects the battery and external power port to the main bus. This means you can start your aircraft using a Ground Power Unit (GPU) thru the external port on the nose (your AFM should have procedures for starting with ground power) but... in order for the that aux port to connect to the bus there must be at least a little juice in the battery to activate the solenoid to make the connection. The solenoid can only be powered thru the battery.

So... if you had a completely flat battery then you would have to take the nose cowl off, open the battery box and charge (or replace) the battery directly on it's terminals. However if you had a least a little juice in the battery you could turn on the master switch and if you hear the "click" from the solenoid in the nose then the Aux power port is now tied to the bus and a GPU can be applied and used to aid starting. You'd obviously want to start your right engine first as the Aux port is very close to the swing of the left prop. Start the right, get the generator or alternator going on that side then have line guy remove the GPU get clear and start the left.

I've heard some Comanche owners say their planes are wired such that a GPU applied thru the Aux port goes directly to the bus without the master switch being turned on (I fly a Cessna 340A that is wired this way). If that is the case then you could in theory jump start (I think) even with a totally flat battery but I do not think that wiring set-up is correct for a PA-30B (it's not in mine).

Here is how you can test your set-up... Connect a 12-14V GPU (12V battery but it's a 14V system really) to the Aux power port. If all the sudden things come on in the cockpit and Gyros start spinning up as if you flipped on the master switch then your Aux port is tied directly into the main bus not thru the master solenoid. However if your plane is wired as my PA-30B is (and this is what I would expect) then when you apply Aux power nothing will happen... not until you flip on the master switch. At that point you will probably see something like 14.2 volts on the bus (with a voltmeter) instead of 12 since the GPU will put out more like 14.2v at peak... like an alternator vs just 12.X volts from your 12V battery...

Here are some pics of the wiring on the inside of the nose cowl. Took these last year after installing the STC Bogert copper wiring kit. I'd done the Bogert battery box already. Hope these pics help...

- Charles

[Robert Solymossy]

Charles,

Thanks very much for enlightening me on the jump start issue. Your comments and photos are very useful and informative, especially for a novice like me.

Robert

[Charles Schefer]

Robert quite welcome.... And we're all novices to one extent or another

[N3322G]

Sure do enjoy photos of Charles maintained plane.

[Charles Schefer]