engine start mode in series/parallel

[lowleveljet]

my electrical theory is weak. what is the difference between starting engines in series versus in parallel mode? my SOP's say that all starts should be in parallel unless maintenance is consulted. any idea why?

[200hr Wonder]

Sounds like you fly a Metro,

Parallel uses 24V and uses both batteries to give the 24V so 1/2 as much draw. 2 24V batteries to provide the power. When you switch to Series you use 48V to start the engines. It spins the Garrett's up quite a bit faster however there are significant down sides. You have essentially once chance at a good start before your batteries are too weak and then your stuck in the middle of nowhere. You also can get some wonky indications when starting in series. Finally due to the quick draw of a lot of power out of the batteries it significantly reduces the service life.

That said Series is a good way to save a slow start and is even required when starting a stone cold engine at times. Though a GPU is the best way.

[Valkyrie_XB70]

You also can get some wonky indications when starting in series.

That's putting it mildly.....

[lowleveljet]

thanks for the informative response. and yes it is a metro. i'd hate to get stuck up in shamattawa because i started in series and blew it haha

[Valkyrie_XB70]

Typically it is usually only used for the first start of the day, but your company SOP's may be different. I would highly recommend doing one just to see the funky sh1t that happens in the cockpit.

[altiplano]

I would rather wear out batteries sooner than have consistent near hot starts on a scabby old Garrett. Series starts rule.

[200hr Wonder]

If your doing the First Start of the day with the NTS test and you want to switch to Series.... where the heck are you suppose to get the fourth arm? As the FO is already guarding stop/feather. This is suppose to be a single pilot aircraft!

[Flying Low]

This was written by a former Thunder Airlines pilot and may be one of the best descriptions ever for starting a Garrett.

Starting the MU2!

1. Place your right hand on the condition lever in case it all goes to hell and you need to move it to "emergency stop". If you move your right hand at all during the process, you will be killed by the most senior pilot. If that's you, you are expected to commit suicide.

2. Take your left hand, and press the starter button, holding onto it until you get light-off, which is indicated by a rise in EGT and fine beads of sweat forming on your forehead.

3. Using your your third hand, hold the unfeathering pump button until the engine reaches roughly 40% and passes the NTS test.

4. Take your tail and use it to hold the fuel enrich button from start to light-off, then tap the fuel enrich button if the engine starts to hang, making sure you don't overtemp it in the process.

5. Take your left foot and use it to flick the batteries from parallel to series if the engine isn't accelerating quickly enough. Dont flick the switch the wrong way though, or you'll shear the starter motor, which is considered a 'bad thing' by most AME's.

You were expected to do all this simultaneously, and to also monitor critical engine parameters. If you messed up the order of any of these steps, or if you used the wrong appendages to do this, expect the engine to promptly melt, and you to enjoy a very, very extended holiday from work.