Military P-51 BATT/GEN

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PonyDriver
Airman First Class
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Joined: 04 Feb 2015, 11:47

Military P-51 BATT/GEN

Post by PonyDriver »

So last night I was getting my MIL mustang ready to taxi. It now has accusim, so I am still learning. Silly me, let the RPM's get to low and it stopped running.

I attempted to re-start it, but I think I killed the battery doing so..Ok fine, well, this is why accusim is cool, right?!?

I then hooked up the GPU and everything seemed to become more alive. Great! I was able to start the engine. YAY!

Then, I thaught, well, heck, the engine's running, Ill dissconnect the GPU. When I did that, the engine stayed running, but the cockpit went dark (it was night) and all the indicaters went out.

Perplexed, I looked around and tried to find out what I did wrong. A few moments later, TADA!everything came back! It worked fine after that, so I was able to go about my way.

(Funny thing, after ALL that...i did not see the Piper Cherokee holding short at the runway. DOH!)

So my question is did the mustang act like was supposed to? Will it take a while for the generator to put enought juice on the battery to bring back the eletrical? Should I have left the GPU connected longer?

Thanks for reading my post!

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gulredrel
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Re: Military P-51 BATT/GEN

Post by gulredrel »

The generator kicks in at around 1300 rpm(? or in that range). Not like in the newer GA planes or in a car, where alternator load is present even at low rpm.
So if battery is weak or empty, there's not enough electricity to keep the instruments working. You need more rpm and with more rpm your battery will be charged too.
In the runup checklist there is a point where you can see load change on the ampere meter with rising rpm.
"Give me a ping, Vasili. One ping only, please."

A-26Invader
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Re: Military P-51 BATT/GEN

Post by A-26Invader »

Generator VS Alternator

The downside to an aircraft generator is that there must be enough rotations within the generator to create electricity that will completely power the entire airplane and its systems. Yes, as the generator is spins it creates electricity but not nearly enough to power anything. The higher the RPM, the more electrical output of the generator.
Alternators on the other hand will produce practically the same power output at any RPM which is why GA aircraft went from generator's to Alternators. Airliners (jet engine) use starter-generators ( yes I said generators) because of one main idea, that a generator can rotate clockwise and counter-clockwise while a alternator can only spin in one direction. Think of the starter in the P-51. By flipping that switch you are allowing electricity to flow from the battery to the starter. In an airliner, hitting the starter switch allows the starter to spin at a high torque (series wound) and once the engine is started, the starter now becomes a generator supplying the aircraft with electrical power. A 2 in 1 system as it happens automatically in a turbine engine. I think the same idea in a military jet engine is the same but I do not pretain to those pesky jet engines! :D Piston pounders bring life to a party!! Sorry about the long explanation of something you probably did not want to hear or read BUT this type of stuff is right up my alley and I love to teach mechanics to anyone who wants to learn :lol:
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n421nj
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Re: Military P-51 BATT/GEN

Post by n421nj »

I think around 1 500fpm the generator kicks in and charges the battery. Best advise is turn on only what you need until right before take off.
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NAA551WB
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Re: Military P-51 BATT/GEN

Post by NAA551WB »

Actually I would leave the generator on from the moment of start up or at the very least turn it on before you do your engine run up to ensure that it's working correctly!
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robert41
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Re: Military P-51 BATT/GEN

Post by robert41 »

The generator takes a long time to fully recharge the battery. I always use the GPU when starting and during warm up.
With the Civ version, without a GPU, I start and warm up without any extra electrical loads on. Sometimes in cooler weather, with extended cranking, pulls the battery down to 22 volts or so, it take a good flight, 15-20 minutes, to get the volts back up to 26.

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taildraggin68
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Re: Military P-51 BATT/GEN

Post by taildraggin68 »

This is why I love Accusim, if you pull it down, it will take time to charge back up. It will behave as the real thing.

joe bob
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Re: Military P-51 BATT/GEN

Post by joe bob »

NAA551WB wrote:Actually I would leave the generator on from the moment of start up or at the very least turn it on before you do your engine run up to ensure that it's working correctly!
As an aside, I was reading a story from a Mediterranean based P-47 pilot who started off on a mission and one by one all things electrical started to fail, he was thinking what a big maint. writeup he was going to have for the crew chief when he got back, then he noticed that the Generator switch was off. He was baffled as to why anyone would turn the Gen switch off and in fact his Group safety wired their switches to the on position after this incident.
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n421nj
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Re: Military P-51 BATT/GEN

Post by n421nj »

In the civ mustang I turn the generator on but turn off all lights except the beacon and nav if at night, I leave the gps off until right before entering the runway. I leave just the com1 radio on until just before entering the runway.
Prior to taking the runway I turn everything on to ensure its working then take off as to minimize the load on the battery for as much as possible.
Andrew

ASUS ROG Maximus Hero X, Intel i7 8770K, Nvidia GTX 1080, 32GB Corsair Vengeance 3000 RAM, Corsair H90i liquid cooler.

All Accusim Aircraft
Accu-Feel, 3d Lights Redux

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