Engine start on batteries

[kneighbour]

It seems possible to start the engines on battery - the thing is to put them in series and not parallel. The manual mentions the Series/Parallel Relay (pg 61) but it does not mention how to set this relay.

 

How do we start just using the battery?

 

I tried - by simply not plugging in External Power. This does something funny that I hope there is an answer for. You hit the START switch and one engine starts to rotate, but I guess it does not go fast enough to trip the ignition system or something. The thing is it will do this now forever. I currently have the battery down to 10V and it is still turning! I can even turn the batteries off and then on, and it is still turning!

 

Is there anyway to stop this?  I ask - not just in this situation - but a few times a start has not worked and I can see no way of getting out of it except to reload the aircraft.

 

I just did a night landing and was surprised to see that there were no landing lights - made things a bit awkward! Only later did I work out that you only get landing lights if you have HDR turned on (which I can't)....

[pict]

The relay should be automatic.

 

Ensure parking brakes on (v key)

 

Turn on both batteries (to the on position), then turn on the battery temperature display, ensure its showing <56C for BOTH batteries (maybe the max is higher, cant remember off the top of my head).

 

Set the volts/amps switch to right gen.

 

Move the condition lever for #2 to start and feather, then move the start switch to #2, hold it for 2 seconds.

-at this point the engine should catch and stabilise with the prop feathered after a few seconds.

 

Turn on #2 generator by first moving thr switch to the RESET position, after ~3 seconds you should see the volts/amps meter showing a load.

-allow the battery to charge for a few minutes (indicated by the amps load gradually dropping).

 

When the battery temp drops below ~39-42C:

-turn on avionics/inverters **(you can choose to wait until after #1 engine has started)

 

Repeat start procedure above for engine one.

 

After both engines have stabilised with gens on + avionics on, bring both props out of feather together, pausing at each point until the engines have stabilised before moving to another, until you get to the 'max' detent.

 

--Xavier

Edited June 25, 2015 by pict

[kneighbour]

Excellent information! Just what I am looking for. Thanks for that.

 

It is interesting that you put the Condition lever in the 'Start and feather' position. Not the Start bit obviously, but that the thing is feathered. It is obvious when you say it - just never thought of it that way before.

 

I am trying to document an Engine Start Procedure, so the more information I can work out the better.

 

If I can trouble you for two other small questions I had in this area?

 

1. The Checklist (and the start video I watched, frame by frame) puts this step

     R BLD VALVE - move to reset and then AUTO  (or left of course)

 

BEFORE starting the engine. It does not seem to do anything at this time as there is no bleed air.

 

It makes more sense to me to place this operation AFTER the engine has started and stabilised. Which is correct?

 

 

2. The start video I watched turns on L AVION and R AVION just after connecting external power and turning on the batteries. Then, just before starting the engines, it gets you to turn them off again.

 

I am not sure why this is done or even if it should be done. I see why ESS AVION is turned and left on (to show the fuel gauges for one thing). But cannot see the point of turning on the Avionics for such a short period of time.

 

 

Thanks for any information. It would be lovely if I could get my hand on a POH or similar!

[pict]

If I remember right, the CT7's bleed air in Auto position will shut them off automatically during start to keep maximum airflow into the combustors' drums during the initial lightoff (keeps down the temperature spike), then enable them after the engineis self-sustaining, hence the resetting them then placing them in the auto position.

 

Regarding the second question, turning off the avionics before start reduces the power spike that occurs on the ESS electrical busbar during the first few seconds of engine start. At any rate, the avionics are "kicked off" the ESS busbar during start up until the engine(s) is/are self-sustaining, then brought back online.

 

The Saab and other CT7 powered props (like the CN235) are a bit unusal in that you out the condition lever in start/feather BEFORE you hit the start switch (the lever position in start/feather arms the igniters if I recall correctly) - with them in the off position, you'll just be "dry motoring" the engine.

 

Hope this helped.

-Xavier

 

(edited for better viewing on desktops - looked good on tapatalk )

Edited June 26, 2015 by pict

[kneighbour]

At any rate, the avionics are "kicked off" the ESS busbar during start up until the engine(s) is/are self-sustaining, then brought back online.

Yes, I see why you would turn the Avionics OFF before engine start. Just cannot see why you would turn them ON at the very start. They would hardly have had time to warm up before you have to turn them off again.

 

Thanks for the bleed air description. Love this level of detail....

[mmerelles]

Yes, I see why you would turn the Avionics OFF before engine start. Just cannot see why you would turn them ON at the very start. They would hardly have had time to warm up before you have to turn them off again.

 

Thanks for the bleed air description. Love this level of detail....

 

 

That is because this is simming. You turn on electricity, engines, systems and your are on the air in 5 minutes. You can asume all systems are operational, you can assume nothing will fail, and there is no lives involved. If something goes wrong you start over.

 

 

On real life, you are required several steps prior to engine startup & takeoff

 

1. Pre-flight, you need all the systems running to test them properly. This process is critical and takes time.

2. Communications, atc clearance, you need the radio systems working and tested as well. you need to perform all atc communications to get your clearance and authorization

 

you do not turn on the engines, if you are not sure you are ready and authorized to make the flight.

 

3. Once you are authorized you put the engines up & running. note you turn the avionics off momentarily not to get them fried on a voltage spike. this aircraft does not have an APU like big jets to keep electricity going and smooth during engine startup.

Edited June 26, 2015 by mmerelles

[kneighbour]

Of course! Stupid me...I should have thought of the clearances, required, etc. Good - all cleared up. Thanks again.

[Cameron]

To further this, there is a time limit after turning the avionics off that they will not have to warm up again. I forget the time, but this IS simulated in our product.

[kneighbour]

I followed your battery start procedure and it worked perfectly. I don't know what I did the first time. The only small issue is that the batteries take a fair time to cool down after a battery start. Perhaps being a simulator, I am not keen to hang around while they cool! But they cooled down ok once I was in the air, so no problem. They charged very quickly - a few minutes.

 

Anyway, got that bit all worked out now. Did a few very nice touch and goes tonight. It drops like a rock on finals if you don't watch it, but that is fine. Just need to finesse the technique there a bit! Once you get used to it, it is very nice to fly.

[JGregory]

The only small issue is that the batteries take a fair time to cool down after a battery start. Perhaps being a simulator, I am not keen to hang around while they cool! But they cooled down ok once I was in the air, so no problem. They charged very quickly - a few minutes.

I love it when a simulator actually simluates real life, don't you?

[Ben Russell]

If the duration wasn't accurate to real world specs people would post bug reports.

[pict]

In real life (at Seabourne and Eagle at least) they use the time charging/cooling the batteries to sort out any last minute paperwork, weight and balance issues, flight plan and other miscellaneous issues that pop up).

So the wait actually doesn't seem too long, of course it'll feel long when you're watching a computer monitor. :-)

Edited June 26, 2015 by pict

[JGregory]

The overheating of batteries and lengthy cool-down is also one of the reasons they do external GPU starts whenever possible.

Edited June 26, 2015 by JGregory

[kneighbour]

The overheating of batteries and lengthy cool-down is also one of the reasons they do external GPU starts whenever possible.

I'm impressed that it is modelled at all. Very impressive minor detail that few would notice, I am guessing.

 

Is there a solution to the case where the engine starts motoring. but never stops?  Even if batteries turned off, then on again? Even if batteries down to 10v?

[kneighbour]

I love it when a simulator actually simluates real life, don't you?

Brilliant, if you ask me. I doubt very few people would even do a battery start, let alone know about battery temperatures if they did.

[JGregory]

Is there a solution to the case where the engine starts motoring. but never stops?  Even if batteries turned off, then on again? Even if batteries down to 10v?

Give me a list of repeatable steps that I can take to recreate this, and I will look into it.