"Low bus voltage" warning light
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"Low bus voltage" warning light
Hi guys,
Today was my second solo cross country navigation flight. Route planned was bankstown - orange - cowra - bankstown. Scheduled flight time of 2.9 hours.
Flight plan submitted, signed out by the instructor and I was off down to the runup bays... completed. After given a clearance to line up rwy 29R the "Low bus voltage" light illuminated on the annouciator panel. I looked at it and wasn't sure whether I should go through with the flight. The tower transmitted me with my takeoff clearance. I thought for a minute then decided to contact the tower again and request instructions to exit the runway, I decided I was not going to risk flying with this warning light on.
I can't seem to find any info about this light, I have never seen it before and my instructor had gone on another flight when I returned so I will have to wait to see him on monday before referring on the problem with him.
Could somebody please shed some light on the nature of this warning light and let me know if I did make the correct decision to cancel the flight, or was it something minor and the flight could have been completed?
All replies greatly appreciated,
M-E'd
Today was my second solo cross country navigation flight. Route planned was bankstown - orange - cowra - bankstown. Scheduled flight time of 2.9 hours.
Flight plan submitted, signed out by the instructor and I was off down to the runup bays... completed. After given a clearance to line up rwy 29R the "Low bus voltage" light illuminated on the annouciator panel. I looked at it and wasn't sure whether I should go through with the flight. The tower transmitted me with my takeoff clearance. I thought for a minute then decided to contact the tower again and request instructions to exit the runway, I decided I was not going to risk flying with this warning light on.
I can't seem to find any info about this light, I have never seen it before and my instructor had gone on another flight when I returned so I will have to wait to see him on monday before referring on the problem with him.
Could somebody please shed some light on the nature of this warning light and let me know if I did make the correct decision to cancel the flight, or was it something minor and the flight could have been completed?
All replies greatly appreciated,
M-E'd
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one other thing I forgot to note when I was completing my run ups that I didn't get a drop in rpm when I was checking the L and R magnetos.
Aircraft was also a Piper 28 Archer III
Aircraft was also a Piper 28 Archer III
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Multi
Did the light stay on when you increased revs (eg at run up)?
If not - low voltage at low alternator rpm - probably minor
If so -
Worst case - major problem with aircraft electrical system leading to flat battery, not radios, navaids, transponder.
You did the right thing. Better sure than sorry. Can always fly another day and if it turns out to be minor - you have learned something.
Cheers
R
Did the light stay on when you increased revs (eg at run up)?
If not - low voltage at low alternator rpm - probably minor
If so -
Worst case - major problem with aircraft electrical system leading to flat battery, not radios, navaids, transponder.
You did the right thing. Better sure than sorry. Can always fly another day and if it turns out to be minor - you have learned something.
Cheers
R
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first off, good decision not to continue with the flight, but did you write up the warning light on in the Maintainence release?
as for what the light means...... no idea. but is the answer in the POH?
as for what the light means...... no idea. but is the answer in the POH?
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Likely something amiss with alternator/voltage regulator/battery.
That light has nothing to do othing to do with magnetos.
Someone will probably turn up here to give you a better explaination.
I just fly'em - don't fix'em.
R
That light has nothing to do othing to do with magnetos.
Someone will probably turn up here to give you a better explaination.
I just fly'em - don't fix'em.
R
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Originally Posted by multi_engined
Would it have been safe to fly though or could there have been a chance of a power failure? or another in flight emerg?
R
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yeah I know that it wouldn't have effected the engine but just curious if I could cause any other serious problems for a fairly new solo PPL student
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Originally Posted by multi_engined
curious if I could cause any other serious problems for a fairly new solo PPL student
Multi goes off on second solo with "low bus voltage" light on. Hour or so later - no radios, navaids, transponder, fuel guages etc. Multi says "Oh ****"! Lands PA28 on airstrip he just flew over out in sticks and shuts down. Now PA28 and Multi are stuck there until retrieved by CFI and LAME with spare battery etc
Serious problem for Multi?? Me thinks maybe!!
R
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Happened to me also on about my second or third solo nav. I got a red ALTERNATOR (or could have been generator) light. Voltmeter / ammeter showed zero, so I turned around and went home before I ran out of batteries. Although I was also in a PA28, and gear and flaps would not have been affected, I would have lost radios, transponder, fuel pump etc etc... so decided to head for home rather than continue and have people think that I had crashed.
I am still alive, so it was a GOOD decision... whether or not it was the BEST decision, will never be known.
Many years later I had to make another decision, which was maybe not in the best interests of the company. I was in an outport and due to fly back to capital city on a THURSDAY evening, with all the freight and mail. Probloem was that when I got to the aircraft, it was covered in snow. the OAT guage read -2C, and there was overcast cloud at about 300' AGL. I needed to climb to about 6000' (3000' AGL) for MSA / LSALT. I made the call to NOT go, even though it would be HUGELY unpopular with the client, hence also the company. The chief pilot was very supportive.... and I thank him for that! but being a fresh CPL, it kept me second guessing for a while as to whether I would still hacve a job or not. After a while I decided that I would rather be alive and unemployed, than dead... for the sake of a couple of LATE mailbags!
I heard later that people in piston twins were having to climb to FL140 to get out of ice!!!!, and they were on the coast.
My advice ??? Make a decision, to the best of your informed knowledge, and stick to it! (unless circumstances change). you will ALWAYS beat yourself up about it for a while afterwards, but... it is a learning game, and you will learn MUCH from the experience. Do some research, and tell me what components you would have lost IF the batteries went flat. Then tell me how they would have affected your flight IF you had continued. The tell me what you would have doen IF you had of continued, and lost power, and the items mentioned, and try to predict the outcome.
not very nice ????
then maybe you made the RIGHT decision!
Now imagne you had pax on board! or were going to leave a wife and kids behind, with no life insurance - not to mention parents, brothers , sisters etc.
and tell me that you made a WRONG decision!
some things are NOT worth dieing for!
I am still alive, so it was a GOOD decision... whether or not it was the BEST decision, will never be known.
Many years later I had to make another decision, which was maybe not in the best interests of the company. I was in an outport and due to fly back to capital city on a THURSDAY evening, with all the freight and mail. Probloem was that when I got to the aircraft, it was covered in snow. the OAT guage read -2C, and there was overcast cloud at about 300' AGL. I needed to climb to about 6000' (3000' AGL) for MSA / LSALT. I made the call to NOT go, even though it would be HUGELY unpopular with the client, hence also the company. The chief pilot was very supportive.... and I thank him for that! but being a fresh CPL, it kept me second guessing for a while as to whether I would still hacve a job or not. After a while I decided that I would rather be alive and unemployed, than dead... for the sake of a couple of LATE mailbags!
I heard later that people in piston twins were having to climb to FL140 to get out of ice!!!!, and they were on the coast.
My advice ??? Make a decision, to the best of your informed knowledge, and stick to it! (unless circumstances change). you will ALWAYS beat yourself up about it for a while afterwards, but... it is a learning game, and you will learn MUCH from the experience. Do some research, and tell me what components you would have lost IF the batteries went flat. Then tell me how they would have affected your flight IF you had continued. The tell me what you would have doen IF you had of continued, and lost power, and the items mentioned, and try to predict the outcome.
not very nice ????
then maybe you made the RIGHT decision!
Now imagne you had pax on board! or were going to leave a wife and kids behind, with no life insurance - not to mention parents, brothers , sisters etc.
and tell me that you made a WRONG decision!
some things are NOT worth dieing for!
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Low Voltage Light "ON", one thing it tells you for sure is that the light bulb works, what it is suggesting to you is the Alternator is not charging the Battery, i.e. read the other instruments, for example.
if the instruments reads:
*13 odd volt and +1 amp or more, the electrical system is fine, therefore the warning system is broken.
* less than 13 volt and less than 0 amps ( or negative ) the alternator or regulator is U/S.
No magneto drop at check: usually means the magneto earthing wire or associated wiring / switches is broken, thing to note here is that the propellor is live, if you turn the propellor by hand and there is fuel in the engine, it will start, and the aeroplane will eat you.
if the instruments reads:
*13 odd volt and +1 amp or more, the electrical system is fine, therefore the warning system is broken.
* less than 13 volt and less than 0 amps ( or negative ) the alternator or regulator is U/S.
No magneto drop at check: usually means the magneto earthing wire or associated wiring / switches is broken, thing to note here is that the propellor is live, if you turn the propellor by hand and there is fuel in the engine, it will start, and the aeroplane will eat you.
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As someone wiser than me once said, "take-offs are optional, landings are compulsory".
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground.
OK, I'll stop now.......
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground.
OK, I'll stop now.......
This is from memory, have not flown a light aircraft for around 12 yrs, and last aircraft with the "little red light"was around 17yrs, so don't take this as gospel.
Low voltage light procedure in C172 was to turn both the battery and alternater switch off for a second or two and then back on. OR maybe it was turn the alternater part of the switch off then on???
I think it means the voltage from the alternater is outside limits, and I have no idea what the limits are. That light may possibly come on at low revs and go out when revs are increased. not unusual. Hence the question earlier about whther it went out whilst doing runups.
My major concern with a flat battery, (being the final result) would be no engine indications(oil temp/press). I assume you keep a fuel log, so the fuel gauges won't kill you, and they are invariably innacurate anyway, no radio flaps etc well that won't kill you either. A flapless landing, and follow no radio/radio failure procures, not ideal but keep your eyes open for other aircraft, look for lights from the tower (if there is one) and again shouldn't be a major problem. I'm not sure landing at the first runway/strip you see is advisable?
Having said that i reckon you did the right thing. if your not sure DON'T GO.
maybe a closer relationship with your POH would be a good idea as well.
Low voltage light procedure in C172 was to turn both the battery and alternater switch off for a second or two and then back on. OR maybe it was turn the alternater part of the switch off then on???
I think it means the voltage from the alternater is outside limits, and I have no idea what the limits are. That light may possibly come on at low revs and go out when revs are increased. not unusual. Hence the question earlier about whther it went out whilst doing runups.
My major concern with a flat battery, (being the final result) would be no engine indications(oil temp/press). I assume you keep a fuel log, so the fuel gauges won't kill you, and they are invariably innacurate anyway, no radio flaps etc well that won't kill you either. A flapless landing, and follow no radio/radio failure procures, not ideal but keep your eyes open for other aircraft, look for lights from the tower (if there is one) and again shouldn't be a major problem. I'm not sure landing at the first runway/strip you see is advisable?
Having said that i reckon you did the right thing. if your not sure DON'T GO.
maybe a closer relationship with your POH would be a good idea as well.
Last edited by RENURPP; 4th Aug 2006 at 09:52.
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Hypothetical situation, The alternator fails, then in a short time following, the batteries fail completly, you are approaching 2RN inbound point to YSBK, what do you do? consider Hoxton park unserviceable. do you continue to fly as normal into YSBK and land? how do you notify the tower of your problem?
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If you had no battery at all you could phone the tower or a mate to call the tower with your intentions. But afterr the alternator fails you still have some batttery power left, how much you have left depends on the condition of the batter and many electrical items you have on. The name of the game is to reduce electrical load, and make a call to ATC tell them that you have had an alternator failure and are inbound to Bankstown with an ETA of what ever, and even throw in that you have recieved their atis. ATC will let the tower know about it. And you never know, with the reduced electrical load, you still may have some battery to contact the tower at one of the approach points.
The point is an alternnator failure is not the end of the world, the engine still runs fine, and you still have some battery to play with, i think a ball park figure is about 30 mins after failure.
I had a complete electrical failure once battery and all. It was no problem, Just did a flapless, kept a good lookout at the CTAF, and had to navigate with out the GPS. Worse things can happen.
The point is an alternnator failure is not the end of the world, the engine still runs fine, and you still have some battery to play with, i think a ball park figure is about 30 mins after failure.
I had a complete electrical failure once battery and all. It was no problem, Just did a flapless, kept a good lookout at the CTAF, and had to navigate with out the GPS. Worse things can happen.