Never Jump Start a CTLS with a Weak or Dead Battery ???

[Steven]

Why does the CTLS maintenance manual warn never to jump-start an aircraft with a weak or dead battery ??? Can it cause damage to the battery or electrical system ? I successfully jump started my plane on several occasions (with an 1800 amp auto jump starter) due to a weak battery or other problem (I'm trying to find the root cause).

 

Here's the quote from page 10-4 of the maintenance manual -

 

Never “jump-start” an aircraft that has a “dead” or discharged battery. It takes approximately three hours

to recharge a fully discharged battery with the aircraft generating system or external power.

http://documents.flightdesignusa.com/CTLS%20MM%20rev.4.pdf

[Jim Meade]

It doesn't say weak. It says dead. If you look online, there is quite a bit of discussion, most of it of dubious credibility, about jumping a car with a dead battery. Most of the instances seem to be concerned with the chances of injury, especially eye injury, due to an explosion caused by a spark.

 

One thing I think I know is that if a battery is dead, it can't excite the alternator and thus it won't charge by itself. I can't say if that is the case with a Rotax alternator, but it is the case with one found on a C150, I can attest from personal experience. So, don't jump a dead battery and expect it to properly charge itself.

 

As far as a weak battery, the manual doesn't talk about a weak battery and I think we should be careful to not extrapolate from the manual to include weak when the manual doesn't. See above for why dead is no good, but weak? I don't know.

 

I'm not sure why the manual says the aircraft charging system can recharge a fully discharged battery. Maybe it can, but how does it do it if it can't excite the alternator? I look forward to some more discussion on the topic.

[GlennM]

I interpret that statement about the aircraft electrical system to mean that you should not count on jumping a dead battery to get the engine started, go fly somewhere, and expect it to restart. Chances are, you would probably not charge the battery enough since many people do not typically fly three hours at a time and people probably think an hour flight will do it.

[sandpiper]

Darn, with all the cars I've jumped using the battery terminals on both ends, howcum I'm still here?

[chanik]

The only bad thing here is the possible damage to the battery. Once running, the generator will try to charge that battery at 12Amps or so if you throttle up. A dead battery wants to be nursed back with small current, in our case just an amp or two. Otherwise, in the discharged state the battery is highly resistive and gets damaged with high charge current

[Roger Lee]

Which battery do you have? The standard Odyssey (SBS8 Hawker) or the Lithium Ion? The Lithium could be an issue. the Odyssey shouldn't be. we do it all the time all over the US. If you can charge it it should be an issue to jump it so long as you don't overload it with a high amp starting charger. Just hooking up another simple battery should not be an issue. It's possible it's more of a liability statement so you don't blow it up in your face from the high amp starter charge?

[sandpiper]

I think liability is at least a big part of it. Any country that puts a warning on irons saying don't iron clothes that you are wearing - what more needs to be said to sum up a sorry state of affairs.

[FastEddieB]

Darn, with all the cars I've jumped using the battery terminals on both ends, howcum I'm still here?

 

Luck?

 

Seriously, I think many of us have routinely used jumpers to battery terminals our whole lives with nary a problem.

 

But lots of people have been seriously injured by exploding batteries over the years. Hydrogen gas plus a spark is all it can take.

 

I have had two batteries explode in the last 7 or 8 years. Both batteries were on chargers but unattended, and neither was in a vehicle, but it can and does happen, and can make quite a mess. You would NOT want it to happen to a battery in a plane, or any vehicle for that matter.

 

So, the most conservative action is to always remove batteries for charging, and if "jumping" an installed battery, the ground connection should be the last and should not be to the battery terminal, but to a chassis ground.

 

Ignoring the above advice will probably never cause a problem. But the key word is "probably".

[FastEddieB]

The only bad thing here is the possible damage to the battery.

 

Well, the other bad thing might be an inability to restart if the engine quit.

 

That's not so much a problem with direct drive engines, in that the propeller will generally keep windmilling, ready to restart if the problem is corrected. Our geared engines are very likely to stop dead, and I don't know if, once stopped, they can be made to windmill to get the engine going again.

 

As far as alternators needing to be "energized", that's true, and can be a problem when hand propping a plane with a totally dead battery. But on a jump start, the jump battery will provide the juice to get the alternator charging as soon as it starts, which it will continue to do even after the jump battery is disconnected.

[Jim Meade]

So, none of us came up with a reason for the Rotax admonition except that it mimics what car makers say. That is, there is the possibility with a car to have an explosion in rare circumstances. Is the Rotax battery type such that that possibility still exists?

[FastEddieB]

So, none of us came up with a reason for the Rotax admonition except that it mimics what car makers say.

 

I thought I just did.

 

The fact that, once jump started, the battery will take a long time to charge to a usable level.

 

In that time, if you have a problem, you may not be able to restart the engine if it stops.

 

In addition, if you lose your charging system you have minimal electrical reserve. The engine will keep running no matter what, but you may lose a LOT of stuff in a very short order, which could adversely affect safety of flight.

 

BTW, both of my battery explosions were conventional lead acid flooded cell batteries. I don't know if other battery types are less likely to have explosion "issues".

[Roger Lee]

Rotax doesn't provide batteries. These warnings usually come from the aircraft Mfg.

Once a Rotax engine starts it generates it's own electrical power and so long as it isn't shut off then you could be good to go any where. Most of our batteries do end up taking a flight charge, but there are some times there are dead cells in the battery and your done. One way to hedge your bet away from home to have have one of those small jump starting units or just carry an small motorcycle set of jumper cables. They are light and small and even then you can usually find someone at an airport with a car with jumper cables or a charging/starter charging unit because other aircraft get dead batteries too.

 

I see it more as a liability isse with most Mfg's. since we have been jumping our batteries for decades.

 

We also use sealed batteries where others may have standard lead acid batteries that can have the cell tops removed to add fluid and then this exposes the hydrogen hazard.

[FastEddieB]

All my caveats and warnings notwithstanding...

 

...I have a connector installed on my Sky Arrow for charging or jumping:

 

 

And I carry this to hook up for jumping in the field, if required:

 

 

Finally, this is one of my exploded batteries:

 

 

Made quite a mess - battery acid is nasty stuff. Imagine that happening as your jumper cable sparked or with the battery in your plane.

[Roger Lee]

The CT has connections built in. You leave the cowl on. Protection if you like. You clamp the negative to the exhaust and the positive to the wire that hangs out the bottom that goes directly to the positive of the battery. It's there just for charging and works just fine for jumping.

[FastEddieB]

It's nice when a manufacturer provides things like that.

 

Good job, Flight Design!

[Doug Hereford]

I agree with the responses. I would underscore the point about electrical reserve. In general, the primary purpose of an aircraft battery (we call them storage batteries in many cases) is emergency power. They store energy to be used in the event of failure of the primary electrical system (alternator). A deeply discharged battery (no matter what type) will have different charging or recovery needs than one that has had a partial discharge (like normal engine start). Normally, aircraft electrical systems are not designed to recover a dead battery, and support the normally expected electrical loads encountered during flight operations. I'm not saying that a person cannot "get away with it", but if there is and electrical failure during flight, the emergency power supply (battery) that was designed to provide a certain amount of continuous power for electrical loads needed to return and land, may not be there.

My opinion is that if you operate an aircraft where dispatch is critical such as flight training, have a second battery on a maintenance charge condition and R&R the batteries instead of jump starting. Otherwise cancel the flight, and remove and recover the battery (if possible) IAW proper procedures.

I realize Jim that this does not answer the question as to why the M/M warning. Maybe that's one for the bean counters.

[FastEddieB]

From the Cirrus SR22 POH:

 

 

"If the battery is not properly charged, recharge it starting with a rate of four amperes and finishing with a rate of two amperes in accordance with Airplane Maintenance Manual (AMM) procedures. The battery should be removed from the airplane for charging, and quick charges are not recommended."

 

The Cirrus does have a receptacle for an APU, and can be started from there if a 24v source is available. My battery in the photo that exploded was one of two 12v's in series that I used for that purpose if necessary. As a side note, it cannot easily be charged from that receptacle without modification, unless the master is on - it must activate a relay, also rendering it unusable for charging if the battery is completely dead.

[Doug Hereford]

Fast Eddie,

The SR22 is a very "electrical" airplane, but your comparison is very valid in my opinion. From a purely economical stand-point, one cannot properly recover a dead (or charge depleted) lead-acid battery without utilizing constant current charging (which the aircraft system cannot do). This is probably the reason for the POH recommendation. If you simply "jump started" the Cirrus aircraft, and dispatched, the battery performance would very likely suffer in the long run leading to premature replacement. More importantly, if you had an electrical system failure, and a jump started battery, you may not have sufficient reserve power to keep stuff on the line ( I realize SR22's have a #2 battery). Dark screens are one thing, but no fuel boost pump could be a problem in a missed approach or other situation close to the surface.

 

Doug Hereford

[Jim]

The CTLSi has a redundant charging and power system:

• Larger amperage alternator (dual)
  
• Lighter Li Ion battery with quick charge capability (dual)
  
• Battery Charger Included
  

 

Completely irrelevant to this discussion.

[FastEddieB]

More importantly, if you had an electrical system failure, and a jump started battery, you may not have sufficient reserve power to keep stuff on the line...

 

A Diamond TwinStar suffered total engine loss after a "jumped" start.

 

Found this after a quick Google search:

 

"The scenario unfolded thus - the battery died and the aircraft had to be jump started. Takeoff went OK but raising the gear caused an electrical drop which normally a charged battery would have masked. The result was, both ECU's shut down, and therefore both engines.

 

Probably the pilot could have restarted the engines given airspeed and altitude (the two things you cant get back).. but not with a dead battery."

 

Different beast than a CT, to be sure, since the ROTAX is self-energized once running, but it drives home the point that a weak battery can cause real headaches, sometimes in unforeseen ways.

[Steven]

Fast Eddie - that's an interesting scenario about the Diamond TwinStar engine power loss due to a jump start -

 

I read that the new Rotax 912 also has an ECU (engine control unit). Would the Rotax engine still run if the ECU shut down due to electrical problems such as low current (amps) ?

 

Here's the article -

 

http://www.rockwellcollins.com/sitecore/content/Data/News/2012_Cal_Yr/CS/FY12CSNR21-ECU.aspx

[FastEddieB]

Would the Rotax engine still run if the ECU shut down due to electrical problems such as low current (amps) ?

 

 

I don't know. Roger might.

 

Hopefully there's a "fail safe" or "limp home" mode if power to the unit is lost, but clearly that was not the case in the TwinStar.

[paul m]

from the 912iS owners manual:

 

1) If Alternator A fails, ECU automatically switches to B. (no power drop is recognizable)

2) Failure of both EMS power supplies result in engine stoppage

Remedy: Switch "On" the backup battery switch. In this case, power supply is provided by the aircraft batttery.

3) Land the plane at the next available opportunity.

[paul m]

Also, Rotax Owner produced a video on 912iS redundancy. Note sure if its free to view or not.

 

http://www.rotax-owner.com/all-videos/rotax-minute/412-912is-redundancy

[Ed Cesnalis]

Wrong. The fact that the FD CTLSi has largely solved the problem of the older aircraft in regard to battery and electrical components is to be celebrated and applauded. If those owning older aircraft want to alleviate the problems of lead acid batteries and single point of failure. One answer is to upgrade aircraft.

 

Wrong yourself. The iS solved a problem that is unique to itself. If I loose all electrical power my panel will go dark but I can continue to fly all the way to my destination. Your iS in the same condition would result in engine stoppage. One answer is to buy an [ab]used CTSW