VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics


Go Back   VAF Forums > Main > Safety
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 11-30-2017, 11:38 PM
lndwarrior lndwarrior is offline
 
Join Date: Mar 2015
Location: Cloverdale CA
Posts: 133
Default Help me understand the correct battery failure in flight response

So I started thinking about emergency procedures and realized something.

I have all the typical emergency procedures documented and carried in the airplane such as Engine Fire in Flight, Engine Failure, etc.. These are all the worst case scenarios - something has already gone horribly wrong.

However they don't deal with "something is starting to go wrong, so what should I do right now?".

These standard emergency procedures don't really address all of the issues and, more importantly, they don't really address incipient issues where you have an indication that something is going wrong and you need to make a decision.

This thought process lead me to the conclusion that I was unprepared for the more likely scenario of, "something is starting to go wrong. What do I do right this minute?"

I decided that the best way to address this in my linear mind was to go instrument by instrument, indicator by indicator and list:

1. System
2. Risk Level to safety of flight (High/Low)
3. Symptom
4. Response

So I'm creating a spreadsheet based on the above. It is a different way of looking at in-flight problems from what I have seen in the past.

I will look at each instrument and indicator in my analogue panel and asses the possible symptoms, what the risk level is for each item and what is the appropriate response.

I think this will be a good exercise to help ensure that I really understand my aircraft.

I decided to do this going from right to left on my panel and assessing every indicator and instrument. The very first one was the EarthX battery fault light.

And right off the bat I realized I did not know the correct response if the light went off in flight.

This light has two indications, one flashing and one solid. The EarthX manual explains what they mean but neither explanation made it clear whether the battery was at risk for immediate failure.

Presumably the solid light would indicate that, but I have emailed EarthX for a clarification. In this case I want to know if it's a "possibility of imminent failure". I haven't heard back from them yet.

Which finally leads me to the question I wanted to post here.

I have an electrically dependent engine due to electric fuel pumps (no engine driven pump). Mags are standard Bendix.

I have an electrical system based on the Aero Electric Z-11 diagram with an e-bus and all the related components on the diagram.

I have a B&C alternator with a VR-166 regulator.

My question is, if the battery fails (and assuming there is no catastrophic damage to the electrical system (ie: the battery electronics safely shut the battery down), will my alternator continue to power my electrical system?

I have heard various discussions about the alternator field wire needing battery power for the alternator to function. I don't know if this is true in my case or not. Is there some other reason why the alternator would not be able to power the system with an off-line battery?

I'm trying to get to the decision point of:

If my EarhtX battery is in danger of imminent failure (fault light is on solid, for example, don't know this for a fact yet). And understanding my plane is electrically dependent,

THEN

A. Do I need to set up for an emergency landing right now, without delay?
B. Am I able to fly another few minutes to a nearby airport and land?

TIA
Gary

Last edited by lndwarrior : 11-30-2017 at 11:40 PM.
Reply With Quote
  #2  
Old 12-01-2017, 05:58 AM
slngsht slngsht is offline
 
Join Date: May 2016
Location: Purcellville, VA
Posts: 173
Default

Your engine has no mechanical fuel pump?
Reply With Quote
  #3  
Old 12-01-2017, 07:04 AM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 7,225
Default

Quote:
Originally Posted by lndwarrior View Post
I have an electrically dependent engine due to electric fuel pumps (no engine driven pump). Mags are standard Bendix.

I have an electrical system based on the Aero Electric Z-11 diagram with an e-bus and all the related components on the diagram.

I have a B&C alternator with a VR-166 regulator.

My question is, if the battery fails (and assuming there is no catastrophic damage to the electrical system (ie: the battery electronics safely shut the battery down), will my alternator continue to power my electrical system?
Z-11 will allow the alternator to continue output, even if the battery (any battery) is disconnected without pilot command, i.e. BAT/ALT master remains ON. The quality of that output (voltage stability, ripple, etc) is an open question and may vary depending on the alternator and regulator choices. I suspect DC electric motors (the fuel pumps) won't care.

That said, Z-11's split or progressive BAT/ALT switch does not allow the pilot to command a battery disconnect and keep alternator output. Opening the master switch in flight will shut down the engine due to lack of fuel.

Wild card; IF a commanded or uncommanded battery disconnect spikes system voltage (I don't know if it will, for sure), the OV module may take the field offline. You'll have a glider.

(Warning: opinion) I think electrically dependent airplanes should meet the same basic criteria as old-school airplanes with mags and an engine-driven pump. You should be able to shut down the airframe electrical without killing the engine. As such, Z-11 as drawn is not suitable for your pump choice.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
Reply With Quote
  #4  
Old 12-01-2017, 11:49 AM
Bicyclops Bicyclops is offline
 
Join Date: Oct 2012
Location: LA, California
Posts: 95
Default

That's the one thing that bothers me about the EarthX - it does have the capability of removing itself from the circuit and to cease providing electrons. With an electrically dependent engine, that is a scary thought. If the battery goes away, will the alternator continue to work? Don't know.

We like to think that 2 failures on a single flight are too rare to happen, but here's one is designed to happen. If you lose your alternator, you transition to battery power only. In theory, you should know how long that will last. But what if you have miscalculated/not checked the reserve capacity or didn't sufficiently reduce demand? Any battery, lead acid or LiFe, will give up the ghost if you keep drawing from it. The lead acid battery will let you know it's coming via falling voltage. The EarthX?

I agree with Dan. You need a backup with an electrically dependent engine, or for that matter with an electrically dependent panel. Some people have backup batteries, some backup alternators, some even do both. Having neither could put you into a bind at some point.

So, as to your checklist item - EarthX battery light on steady - Monitor and prepare to enable battery #2 (which has had its capacity checked recently).

Ed Holyoke
Reply With Quote
  #5  
Old 12-01-2017, 06:01 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 1,138
Default

Gary,

I offer that your system demand exceeds the capability of the Z-11 type power distribution scheme. Your engine must have power to keep running. Any single battery design fails to achieve a risk tolerance acceptable for this criteria.

Carl
Reply With Quote
  #6  
Old 12-01-2017, 07:59 PM
scsmith scsmith is offline
 
Join Date: Jan 2008
Location: Ashland, OR
Posts: 1,705
Default

If the solid light comes on, or any other indication of failure on any Li-ion battery, I suggest you land ASAP.

I agree that with electric-only fuel pumps, you need a backup battery system.
__________________
Steve Smith
Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet"
Hobbs 470 in 8 years
also LS-6-15/18 sailplane
Reply With Quote
  #7  
Old 12-01-2017, 11:48 PM
jwilbur jwilbur is offline
 
Join Date: Dec 2010
Location: Culpeper, VA
Posts: 589
Default EarthX Manual

In my opinion, the EarthX light is not really a fault indicator. It's really a "pay-attention-to-me" indicator.

You can boil down the EarthX manual to this:

1.... If your voltage is in the normal range (below 15 volts) and your current draw is also within normal range, nothing is urgent. A flashing light just means the cells are balancing. The flashing will stop in a few minutes. A solid light means there's a problem with the BMS (not necessarily the cells) and you should land when you can - not really an emergency.

2... If the pay-attention-to-me light goes on and your current or voltage are high, kill the alternator and land.
__________________
-Joe Wilbur (N520LW)
Phase II - 11/2017
First flight - 8/2017
Pink slip - 7/2017
RV-10 Build Log
Reply With Quote
  #8  
Old 12-02-2017, 01:11 AM
rv8ch rv8ch is offline
 
Join Date: Feb 2005
Location: LSGG
Posts: 2,131
Default Battery choice

I plan to put a lifepo4 battery in my aircraft, leaning towards the earthx. I have a mechanical fuel pump and 2x pmags, so I'm not electrically dependent, like you are.

I agree with Carl and Dan that you may want to rethink your design. There are solutions with one battery and two alternators that have been successful (Z-12, Z-13), but these are designed around a "dumb" lead-acid battery that won't turn itself off, no matter what. Yes, it can fail, but it's rare.

I'm not aware of anyone flying with an electrically dependent aircraft with one alternator and one battery, as shown in Z-11. That's probably a bit too risky. I'd go with either Z-12, Z-13, or Z-14. I think today Z-14 with lifepo4 batteries would be fine, not sure I'd use a lifepo4 with Z-12 or Z-13. My personal comfort with them is not quite there.
__________________
Mickey Coggins
http://rv8.ch
Reply With Quote
  #9  
Old 12-02-2017, 10:23 AM
n82rb's Avatar
n82rb n82rb is offline
 
Join Date: Jan 2007
Location: fort myers fl
Posts: 643
Default

Quote:
Originally Posted by rv8ch View Post
I plan to put a lifepo4 battery in my aircraft, leaning towards the earthx. I have a mechanical fuel pump and 2x pmags, so I'm not electrically dependent, like you are.

I agree with Carl and Dan that you may want to rethink your design. There are solutions with one battery and two alternators that have been successful (Z-12, Z-13), but these are designed around a "dumb" lead-acid battery that won't turn itself off, no matter what. Yes, it can fail, but it's rare.

I'm not aware of anyone flying with an electrically dependent aircraft with one alternator and one battery, as shown in Z-11. That's probably a bit too risky. I'd go with either Z-12, Z-13, or Z-14. I think today Z-14 with lifepo4 batteries would be fine, not sure I'd use a lifepo4 with Z-12 or Z-13. My personal comfort with them is not quite there.
I havent looked at the z-11, but I have one battery, one alternator and two lightspeed ignition systems. so I am totally electrically dependent. I don't see the big risk in this system. I have never had a battery go from operating to zero volts. so I think the odds of having a total battery failure and a total alternator failure are pretty slim. I will add a small backup to run the ignitions, but have not gotten around to it, it is a risk but in my option a very, very small one.

I do however run a lead acid battery, i have no confidence in the lithium batteries at this time. there have been to many problems, and they seem to be a tricky system to keep running happy. I will gladly ive up the weight for the simplicity and reliability of a lead acid battery.

bob burns
RV-4 N82RB
Reply With Quote
  #10  
Old 12-05-2017, 04:07 PM
bret's Avatar
bret bret is offline
 
Join Date: Feb 2010
Location: Gardnerville Nv.
Posts: 2,686
Default

I installed a 20 AH back up battery, if I get a primary EarthX battery problem or alternator problem, I shut down the field, then Aux battery On and then master Off. This gives me theoretically 2 hours to run the EFII system but I will land within 30 min and the Dynon backup batteries should keep the EFIS running for 45 min.
__________________
7A Slider, EFII Angle 360, CS, SJ.
2017 gladly supported
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 04:50 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.