Need Help, Please
 

I have a problem and would appreciate help: Flew to West Yellowstone, was struck by a fit of stupid, and left the master and mags on. Next day when I returned to the apt to fly home, naturally the system was dead. I had the service there give me a jump start, and after the front engine got going I told him to disconnect and back away. I noted that the rear engine wouldn't turn over and their was significant discharge when I tried to crank it. I shut down the front, had him reonect the external cable, and started both engines this time. I noted, however, that there was no reading on any gage. I couldn't get the electrical system to work. Switched votlage regulators, shut the master on and off, etc. I shutdown the engines, pulled the front cowling, and looked at the "gen" fuse, but it looked OK and I don't think it has anything to do with no electrical andyway although I don't know for sure.

Model: 1967 Turbo.

What could be wrong? Could both voltage regs be shot? What else could be wrong? I have to make some intelligent guesses and then steer A&P unfamiliar with Skymasters around the troubleshooting via phone, remote as it were, since I won't be there. I'd like to have him get to the bottom of things with the best guidelines.

Appreciate help from this always knowledgable group ASAP. Thanks.

Paul, I believe that the alternators need a minimal line voltage fro the batteries to kick in. There is in "exciter" inside the alternator that must be energized. The engines will start and run on a jump due to the magnetos but the alternators won't kick in. This would not happen if there was at least some juice in the battery. You need a new battery.

Someone correct me if I'm wrong.
Mike

Any A&P should be able to troubleshoot this one, it is not really Skymaster specific. I am not an A&P, but the things I would check first are:

1.) Is the battery holding a god charge? Can it be charged? Running it dead like that may have ruined the battery, you may need a new one. I would not necessarily replace the battery immediately, I would have them test it first. If you have no indication at all on your alternator guage, no lights, no fuel guages, etc. it almost (but not quite) has to be the battery, the alternators are not an issue yet.

2.) If the battery is good, I think other possible culprits are the battery contactor, and the battery (master) switch itself. But leaving the master on is not likely to hurt either of these, and would hurt the battery, so I still suspect that.

As you probably know, if the battery is completely dead, or failed, the alternators will not charge the battery (or power your electrical system) because there is no field current to get them started. I think your airplane is old enough to have a RUN/STANDBY switch (I think that is what it was called) that, when placed in the standby position, will power the alternator fields from dry cell batteries. You could try this. If it works, you've isolated the problem to the battery. If you go back to the RUN position after a couple of minutes and the electrical system dies again, it probably means the battery won't hold a charge.

However, if the RUN/STANDBY switch has no effect, it does not necessarily mean anything, because often the dry cell batteries are dead or sometimes completely missing in these airplanes. That should not be the case, they should be checked during the annual, but it gets missed frequently.

As always, I am sure the A&P's in the crowd can provide more knowledgeable input.

Kevin

(Thanks for the input.) The particular model I have doesn't have the "DC" field current backup system - it never did have, best I could research - even talking to Cessna's multiengine service department.

Meanwhile, neither the "Standby" or any other switch I tried would make any difference.

The reason I think something must be blown is because I was getting a working electrical system after the first jumpstart. It was only after the second that everything went dead.

Hi
The second item that Kevin has posted is your problem.
If you start the airplane with external power with a flat battery, the battery will not charge because the battery contactor is not pulled in. Unfortunatly the external power socket is not across the battery.

If you had jumpered directly across the battery you would have had no problem in bringing the alternator on line.

This is a reason for having the alternator restart system on the newer models.

Pete

Try taking the battery out, servicing it, and charging it. If, as other posters have mentioned, your problem is no exciter voltage, this should take cre of your problem. At the very least, if the battery will take a charge, you will have eleminated one variable.

Mark

Wow - that is encouraging because if all I need is a new battery I can get one locally, run back up there, switch it out myself, and fly home (having delivered the rental car back to the same place, etc. and everything in one shot).

Thanks to all for their input. I'll be planning my return trip ASAP.

Happy to report that you were all correct - replaced the battery, and everything worked as designed. Problem solved, plane back home, etc.

Thanks for the help. It was much appreciated.

Hurrah! Glad to hear you are airborne again Paul...

Kevin

Thanks to you and the board, and all those who helped. Nice place to know one can find friends.

You replaced the battery when that was not the problem. If you had done as Pete Somers indicated and jumped directly accross the battery, this would have brought the alternators on line and the battery would have charged up. Or you could have just recharged the battery. The initial problem was caused by leaving the master on and flattening the battery. Sunny sky.

Sunny Sky, I diasgree and think you are wrong. In over more than 50 years of flying, 90% of the time replacing the battery will solve all sorts of electrical problems (excepting CBs that continue to blow.) It can be done very quickly and cheaply (under $300) and at the most one might have to wait one night to get a new one by overnight delivery.

Many years ago, I was in the FBO busniess. Often customers would come in reporting various electrical problems. Our standing solution was to put in a new battery. If it worked, we charged only for the battery and no labor. If it didn't work (maybe 20% of the time) we removed it and started troubleshooting. With maintenance rates up in the $75 hour range, batteries are really cheap. One can keep the old one and if it's still good keep it as a spare. BTW, we got quite a few new customers that way.

You might ask Paul Sharp if he wishes that's what he had done.

I wonder if Pete Somers can expand a bit on jumping across the battery, rather than through the external power socket. The way I read it, you're suggesting doing it as in a car, where you use a pair of jumper cables to go from one 24V external battery (or two 12V batteries in series, for people like me in-out islands where there are no 24V batteries) directly to the posts of the aircraft's battery. In Paul's case, would a desirable prior step might have been to check water level in the cells and add distilled water first?

The way I read this, if you do it Pete's way, and keep the external battery on for a few moments after both engines have started, both alternators will start because they are seeing a healthy 24V (from the external battery). I assume that the real value of this procedure is when you have a totally dead battery (if you have a battery which is too weak to start the engines but still has some juice in it, I think the alternators will start, right?)

We would be grateful, Pete, for your comments and suggested procedure. For instance, do you remove the jumper cables and external battery, and replace the battery cover and front-engine cowlings with the front engine running? Or -- for safety -- do you shut off the front engine and, with the rear engine running to charge the battery, clean up the front-engine area? My concern with the safer approach, for a totally dead battery like Pauls', is that the 10-15 minutes of charging with the rear alternator may not put enough energy into the battery to start the front engine.

Thanks in advance for your views.

Ernie
(Hadn't lost interest in Skymasters, just been away for two months)

Ok Ernie and all.

If the ships battery is flat, ie you put on the master switch and nothing.
You go for the power cart and plug it into the external power socket, hey presto you have power (but the master is not on).
You carry out a start of both engines and disconnect the power cart, go to switch on the master and nothing, because the battery is flat.

However if you jumpered the battery and started the rear engine, disconnect and run the engine to enable the front to be started, the system would be online and charging the battery (at a high rate).

1. Some of the bus services are isolated with the external power connected including avionics.
2. The master relay and switch control the alternator field.
3. the 337G and above have ALT restart which (if the restart batteries are ok) should start up the alternators after start and bring the systems on line.

So the only way to get your Skymaster back into the air is to jumper the battery.

BTW, there is such a thing as removing the battery and charging up rather than replacing it due to it being flat.

Hope this answers your questions
Like to hear your comments?

Pete

ps Piper a/c external power sockets connect across the battery thru a contactor for starting, do'nt know why Cessna did not do this???.

Cheers

I would be happy to explain this further thru the wiring diagrams, however there are alot of variation to the Skymaster electrical systems thru it's days.
Please let me know if i can help.

Have a good day

Damn, I like this Board!

Good post and explanation Pete.

Thanks,

Keven
________
THE CIGAR BOSS

Pete, thanks so much for your answer. I would caution, however, that flight immediately following such a restart is not advised and may even be against regulations. Setting aside the regulations, let me suggest a couple of things before taking off.

First (and this is subject to Pete being in accord), I would check water level in the cells and add distilled water before jump starting the rear engine.

Second, I would run the rear engine 5-10 minutes after disconnecting the jump (external) battery and then (gasp!) turn it off to see if the battery accepted some charge. How close is the battery voltage to 24 volts with the master switch on (so that there are some loads connected). If there is no voltage meter on your panel, measure the voltage across the aircraft battery posts with an external voltmeter. You might also turn on some heavier loads (lights, maybe flaps, but not cowl flaps due to their sensitivity and cost) and see if the battery has juice to operate them. The purpose of this step is to determine whether the battery had drained down to nothing but is good (i.e., will accept a charge) or is totally gone, incapable of charging. Don't you want to know this before you get going? Even if you have to take off (after re-connecting the jump battery and following Pete's procedure for restarting both engines) don't you want to know whether there will be a) some or b) no battery on board? For instance, if you lose an engine or an alternator. Or, in my 337G, with a powerpack for the gear, I know my gear will hang up in mid-travel when there is little or no battery left (because the last few seconds of gear travel demands so much power that the alternators alone can't hack it), so, if I choose to go, I'm going to leave my gear down.

Third, once I have both engines going, look at your idiot lights to make sure that both alternators are putting out. I wouldn't take-off with a bad/dead battery and a bad alternator. If your idiot lights are bad or unreliable but you have a voltage meter on your panel, you can determine alternator output by looking at the meter as you turn each alternator off and then on.

Finally, depending on your findings as to the condition of the battery and the alternators, it would be most prudent if you had a hand-held aviation radio on board before take-off.

Ernie
(Sorry if the above was too obvious/detailed/pedantic for the savvy -- it's meant for the average owner or pilot.

Ernie
Yep, the procedure I gave is really a 'get home last resort' and if you are really stuck.

Now if you jumper the battery on the older Skymasters and do a start on the rear, and run it , from memory i do not think you will be able to start the front due to the small alternators on the older models (i am sure i have tried it).
The 60 amp systems are no problem.

And as you say Ernie, if you have to take off with a low battery, leave the gear where it is down, raising the gear uses a lot of power and it does not make all that much differance to the speed anyway.

Battery maintenace is just as important as the servicing of the engines. The UK CAA called for a capacity check on these batteries every 3 months until everyone complained that it was destroying the batteries rather than doing good, but that is one of many backward idea's of our system.

Just checking the water level and maybe put it on charge now and again will keep a battery good.

Remember a lot of the system rely on the electrics, so if you see or hear something you are not sure of get it looked at.

If you need any help on the electrics let me know!!

Good comments Ernie!!

Happy flying

Pete

Read the followup comments, and would like to add a couple of my own...

First, I'm glad I simply bought a battery and got on with it. I think that 3 years is around a good life-cycle for a battery - which is what I had gotten on the old one even though it hadn't been showing any signs of being done with - but due to that amount of life on it I'm not unhappy about putting in a new battery. Up in West Yellowstone, with no A&Ps and no shop available, it was much easier just to put a new one in and be done with it. Took less than a half hour to install, button up, and be doing the preflight for the trip home.

Second, on the idea of not being able to sart the front from the rear only running, that would be an interesting experiment to try some time with a known weak battery. I have been able to start the rear first and then the front when I tried it before, but that wasn't with a flat battery.

Third, I made myself a set of special jumper cables for starting the bird remotely where there might not be any 24V sources. What I did was to create a small jumper that can connect between the minus side of one 12V battery to the plus side of a second 12V battery. Then I have the standard 2 cables which can be connected from the one remaining plus post and one remaining minus post. So by connecting in series I can get 24 volts.

But - aha - for me that would only allow me to get them started; I'd have to do something else about getting alternators back on line, since my early model has no "restart" DC pack to do that. I guess I could simply connect to the battery posts instead of using the exterior connection cable, though.

Others might consider that little trick who are sometimes way out in the boonies. If there are any cars around you can probably beg/borrow 2 batteries long enough to get 24V with a series hookup.

Last, my plane has dual hydraulic pumps. I wonder if it needs to "borow" battery power to get the gear up (assuming they're both working)? Would be interesting to know.

On your last point, Paul, I don't think that models with gear hydraulic pumps (like my old 337D) have any significant electrical power draw (which models like my current 337G with a powerpack do). You probably need some electrical power for switching, but it's negligible.

Ernie