In flight alternator failure=Low Oil pressure

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hankrausch

Pre-takeoff checklist
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GoodbyePOA
Hello,

Just thought I would share my experience this weekend. I lost the alternator in flight but did not notice alternator amps going to zero. What I DID notice though was oil pressure going to near zero--apparently it is an electric indicator that needs voltage to run. And then the gas gauges started dropping to empty as well, also a victim of the low bus voltage. I am sure that in the calm of a written test if someone asked " you lose the radio, the oil pressure goes to 10 pounds, the gas gauges start dropping to empty", what has happened?" that I would correctly figure out it is a bus voltage problem, but when it is happening in flight that low oil prssure sure seems to monopolize your attention!
 
I remember as a youngster in a 172 being midway across the deepest Great Lake and noticing I was completely out of fuel. "WTH??", I exclaimed to myself as I turned to shore. Took longer than I wanted to figure out it was a charging system failure.
 
i never would've thunk of that, thank for sharing!
 
Wow, guess I need to spend more time studying the POH and aircraft systems! Good lesson learned.
 
Let'sgoflying! said:
I remember as a youngster in a 172 being midway across the deepest Great Lake and noticing I was completely out of fuel. "WTH??", I exclaimed to myself as I turned to shore. Took longer than I wanted to figure out it was a charging system failure.
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I have two independent electronic gauges and after reading this I'm really glad I can look out my window and see the manual tank gauges :yes:
 
Know thine gauges: My PA-28 140 has an electric oil temperature gauge, but its oil pressure gauge is a bourdon tube. So if I see a low pressure indication, it is a low pressure indication.
 
That's good to know. We noticed the transponder had lost altitude encoding when the alternator went out.
 
Good observation and good reminder!

I was flying the V Tail Bonanza last fall and noticed the startup was sluggish. Checked the Ammeter -- 0 (as expected). Checked the battery -- it was low.

Replaced the battery -- Startup as expected.

Then one day I'm flying a bit longer -- everything checks out. Ammeter still pegged at 0.

Slow down, start to enter the pattern, gear down -- gear down?

Nope.

Flaps?

None.

Transponder green light?

Faint.

Ammeter?

Still indicating 0 (no charge or discharge).

Out of the pattern with eyes wide open (I was announcing, but no one would have heard me), manually crank down the gear, back in the pattern, land about 8 knots faster (no flaps).

The ammeter was bad -- and had been bad -- while the alternator was slowly dying.

Moral? Check the ammeter immediately after startup -- it should be indicating a recharge (will be - building back to 0). If it's always "in the green," it's lying.
 
dmccormack said:
Good observation and good reminder!
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Yes!
Moral? Check the ammeter immediately after startup -- it should be indicating a recharge (will be - building back to 0). If it's always "in the green," it's lying.
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Second Moral: Know your plane. If you have a loadmeter installed, engine running and battery and alternator switches on, zero on the loadmeter is always a sign of trouble.

-Skip
 
Skip Miller said:
Second Moral: Know your plane. If you have a loadmeter installed, engine running and battery and alternator switches on, zero on the loadmeter is always a sign of trouble.
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The Zodiac's start checklist has turning on the battery only for start, then the alternator field after checking oil pressure and setting idle. I look at all of the engine and electrical gauges when I check the oil pressure, to make sure that it's showing a discharge before turning on the alternator field and a charge afterwards.
 
smigaldi said:
How does your oil pressure gauge show a discharge or charge indication?
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Based on what he wrote--it reads to me like this--The Zodiac checklist calls for this:
1.) Battery On
2.) Start airplane
3.) Check Oil Pressure, Set idle
4.) Alternator On

He said that he also checks the electrical gauges during step 3 to make sure it's indicating a discharge. Then he turns the alternator on to verify that it is charging.
 
smigaldi said:
How does your oil pressure gauge show a discharge or charge indication?
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Read the WHOLE sentence, Scott... ;)

jmaynard said:
I look at all of the engine and electrical gauges when I check the oil pressure, to make sure that it's showing a discharge before turning on the alternator field and a charge afterwards.
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flyingcheesehead said:
Read the WHOLE sentence, Scott... ;)
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I did.

jmaynard said:
The Zodiac's start checklist has turning on the battery only for start, then the alternator field after checking oil pressure and setting idle. I look at all of the engine and electrical gauges when I check the oil pressure, to make sure that it's showing a discharge before turning on the alternator field and a charge afterwards.
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I was being a grammar Nazi.

The correct sentence is
I look at all of the engine and electrical gauges, then I check the oil pressure, to make sure that they're showing a discharge before turning on the alternator field and a charge afterwards
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Subject/verb agreements are important!
 
smigaldi said:
I was being a grammar Nazi.

The correct sentence is
Quote:
I look at all of the engine and electrical gauges, then I check the oil pressure, to make sure that they're showing a discharge before turning on the alternator field and a charge afterwards
Subject/verb agreements are important!
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Well, to continue on in the oberfuhrer grammar Nazi gig, the comma after "oil pressure" is redundant, THEY cannot show a discharge, only the ammeter can show a discharge.

"I look at all of the engine and electrical gauges, then I check the oil pressure and make sure that the ammeter is showing a discharge before turning on the alternator field and a charge after turning on the field."

:yes:

Jim
 
smigaldi said:
The correct sentence is
I look at all of the engine and electrical gauges, then I check the oil pressure, to make sure that they're showing a discharge before turning on the alternator field and a charge afterwards
Click to expand...
Subject/verb agreements are important!
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Yeah, but so is reading what I wrote...I look at all of the engine and electrical gauges when I check the oil pressure. It's all one check. :)
 
I think the symptoms of all of the gauges going to zero can have two causes:

1) electric failure
2) engine failure :rolleyes:
 
mikea said:
I think the symptoms of all of the gauges going to zero can have two causes:

1) electric failure
2) engine failure :rolleyes:
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In an engine failure the ammeter would pass through zero and read dishcarge, and the oil temp would still read warm. If the engine is windmilling the tach would also read.
Now, if the engine fell off the airplane, they'd all read zero. But with the CG so far aft we wouldn't notice it.

Dan
 
smigaldi said:
Good observation. I will have to file that one into the grey matter.

Did you also have an 'ALT' light somewhere on the panel light up?
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Sorry for the long delay, been travelling--yes, there is a light, and yes, I did manage to not notice that either! I suppose I mentioned this because it really brought me up short that things were going on with indications right in front but not noticing, I have mid-level experience, about 1800 hours, and it really made me re-evaluate the whole complacency thing.
 
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