[Boxkite]

just to add if the battery is very flat on something like a Cirrus running all its equipment will require the alternator to work hard and it would take quite a while to recharge a battery while using all the equipment at the same time, with a short flight you may well find the battery flat again after landing.

Further to that, it should be noted that you should never try to start a Cirrus using a Ground Power Unit with a flat battery. During annual, the service centre ran the battery down whilst chasing an issue with the EHSI and an inexperienced tech decided to fire my bird up by using ground power. Net result: melted starter, melted battery, destroyed solenoids in the MCU.

Fortunately, I didn't pay for the repairs, got a new battery and better starter to boot

What a ridiculous design. It wouldn't be difficult to build in a system to prevent that happening.
Didn't Cirrus consider that almost everybody would naturally think you could start from ground power when the battery is not up to it.

[Paul_Sengupta]

I think that applies to most aircraft, I personally would get the battery properly charged or replaced rather than risk trying to fly with a flat battery and relying on an alternator to change it in flight.

Good advice if you can do it. Lead acid batteries don't like being charged from flat with tens of amps, as if flattening them in the first place wasn't bad enough! It'll shorten the life. Trickle charging will extend the battery life - but it can take a while! Tens of amps from, say, 80% full to full isn't so much of an issue.

[Waveflyer]

AIUI. The alternator will not charge until it is excited.

Are we married?

Yep, for 55 years and she's never charged but I sometimes wished she had, it would have been a whole lot cheaper

[stevelup]

AIUI. The alternator will not charge until it is excited. When the engine is running with 1000 or so revs you simply switch something on to draw electricity, landing lights, taxy lights etc. (not low powered items or expensive nav kit) and that will excite the alternator which will start charging.

This is not necessarily the case. An alternator (any alternator - this isn't aviation specific) needs a voltage across the field windings in order to generate a charge.

If the battery is completely dead, or dead below a point where there isn't enough voltage to adequately excite the field windings, then it will just sit there doing nothing at all.

It won't matter how long you leave it, what you have turned off or on, and what the RPM setting is. Nothing will happen - so there's no way of charging a totally dead battery in flight after hand-propping.

On the other hand, if you have ground power connected and start the engine, the ground power will excite the field windings and that should then be self-sustaining as long as the engine stays running. But that is very risky because if you suddenly switch on a large load, that may then cause the battery voltage to drop below the minimum level again and the alternator will drop off line not to return.

So all in all, it's a really bad idea to 'bump start' an aircraft with an alternator where the battery is in an unknown state.

[Miscellaneous]

So all in all, it's a really bad idea to 'bump start' an aircraft where the battery is in an unknown state.

We're okay in the little Jodel, we have a dynamo.

[MichaelP]

The batteries were flat.
The Master solenoid would not turn on.
No problem, used the ground power plug and started the engine... Separate system, no connection to the Master solenoid or the batteries, and so even with the engine running there would be no charging as the solenoid would not activate.
Took the batteries out and charged them.

So check that there’s enough power left in the battery(s) to activate the Master solenoid, otherwise no juice will flow.

Diamond aircraft have an EPU switch and an external start procedure.

Older aircraft have dynamos, and I personally don’t mind them. I am not one of those people who would replace a dynamo with an alternator.
‘Had many more failures with alternators, and they cost money!
But dynamos need to be properly set up.
Took the three Condors dynamos off, had them overhauled, put them back on, set them up and end of troubles for a long time.

IIRC TNS 8 mandated hand swinging the propeller first start of the day. Rollasons noted the number of sprag clutches required by the O 200 engines; the lighter wood Evra propellers allow for more damaging back fires.
So I’d get the comment “...the radio only works above fifteen hundred RPM...”, “Turn the Master Switch On”

The dynamo in the Cessna 120 needed overhaul, took it to the approved place here in Vancouver and they did a very poor job... This as well as a few other trials taught me that I could not rely on anything overhauled or repaired by a shop in Canada. Not anything!
Took my Hasselblad in for repair in Vancouver, cost me, didn’t work. Took it in to a company in Redhill who charged me £45 (a quarter of what I had paid in Vancouver), and they fixed it, plus presented it back to me properly with obvious pride and quality.

Swapped my overhauled twice, still dirty, dynamo in Canada for one that a homebuilder had restored. Beautiful job, flashed the field, and it worked perfectly.
Many homebuilders are better quality workers than some of the so called professionals.
I would never put a less reliable alternator in my 120.

[stevelup]

We're okay in the little Jodel, we have a dynamo.

As does our DR250! I've tweaked the sentence you quoted

[Full Metal Jackass]

It should be noted that you should never try to start a Cirrus using a Ground Power Unit with a flat battery. During annual, the service centre ran the battery down whilst chasing an issue with the EHSI and an inexperienced tech decided to fire my bird up by using ground power. Net result: melted starter, melted battery, destroyed solenoids in the MCU.

Fortunately, I didn't pay for the repairs, got a new battery and better starter to boot

What a ridiculous design. It wouldn't be difficult to build in a system to prevent that happening.
Didn't Cirrus consider that almost everybody would naturally think you could start from ground power when the battery is not up to it.

I'll agree with you there. It is the most stupid design aspect of the aircraft.

[flyingeeza]

What a ridiculous design. It wouldn't be difficult to build in a system to prevent that happening.
Didn't Cirrus consider that almost everybody would naturally think you could start from ground power when the battery is not up to it.

I'll agree with you there. It is the most stupid design aspect of the aircraft.

I bet it generates (sorry) loads of nice spare parts revenue for Cirrus...

[Pilot H]

What a ridiculous design. It wouldn't be difficult to build in a system to prevent that happening.
Didn't Cirrus consider that almost everybody would naturally think you could start from ground power when the battery is not up to it.

Perhaps they considered that almost everybody would naturally read the POH; as we have all been trained to do...

A ground service receptacle, located just aft of the cowl on the left side of the airplane, permits the use of an external power source for cold weather starting and maintenance procedures.

• Caution •
Do not use external power to start the airplane with a 'dead' battery or to charge a dead or weak battery in the airplane. The battery must be removed from the airplane and battery maintenance performed in accordance with the appropriate AMM procedures...

[Dave W]

Best practice in design is not to rely solely on information in the POH, but rather to provide an intuitive, robust and fail-safe design that considers potential human factors through-life.

Also:

• Caution •
Do not use external power to start the airplane with a 'dead' battery or to charge a dead or weak battery in the airplane. The battery must be removed from the airplane...

Best practice in POH design would be to describe the consequences of failing to follow the POH, otherwise an operator does not know if the result would be that the action simply doesn't work or whether (as in this example) significant damage will result.

[MichaelP]

Read the POH?

Used to be you got in the aeroplane and flew...
Then they produced a short flight manual of some kind with the knowledge that people who flew were not so stupid.
Then they produced more complex manuals because people wanted to prepare to fly airliners.
Now they produce super complex manuals, and all sorts of placards, you might die!, because lawyers and insurance companies have determined that most people are bloody stupid these days, no common sense whatsoever, won’t know how to fly an aeroplane considering the risks, and therefore the words, lots of words are there because stupid pilots and other legally challenging persons will try to lay the responsibility on the manufacturers for producing death traps for stupid fools.

All aircraft bite fools.

[Waveflyer]

The mighty C172T was certainly not over “frilled” but when you plugged in ground power using a big NATO plug, powering that circuit simply tripped the starter circuit so that you could not start on the key.
In the early days if the G1000 I sat there for hours getting used to the new systems when there were very few people around who were able to offer training.
Very simple solution.

[stevelup]

There’s some slightly selective quoting of the Cirrus POH going on there... the paragraph before makes it clear that it’s entirely acceptable to start the engine with ground power applied.

The advice in the manual is because of the reasons I already explained, not because it will self destruct. And it applies to any aircraft with an alternator. God knows how the tech burned out FMJs starter motor. I suspect there was far more at play here...

In full...

Application of External Power

A ground service receptacle, located just aft of the cowl on the left side of the airplane, permits the use of an external power source for cold weather starting and maintenance procedures.

• WARNING •
If external power will be used to start engine, keep yourself, others, and power unit cables well clear of the propeller rotation plane.

• Caution •
Do not use external power to start the airplane with a ‘dead’ battery or to charge a dead or weak battery in the airplane. The battery must be removed from the airplane and battery maintenance performed in accordance with the appropriate AMM procedures.

[VRB_20kt]

24v or 48v into a 12v system?

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