Starter duty cycle

[Driver170 42]

Hope someone can expand on the actuall procedure and what it means?

 

Starter Duty Cycle :

First attempt ....................................2 min. ON & 20 sec. OFF -

Second & subsequent attempts. ..........2 min. ON & 3 min. OFF

 

2 mins ON - does that mean the GRD switch on for 2?

[JoeDiamond 67]

 

 

2 mins ON - does that mean the GRD switch on for 2?

 

It means the starter can be on for a maximum of two minutes which must be followed by 20 seconds off before the next start attempt.

[Driver170 42]

So if you get an abnormal engine start wouldn't you place the starter to OFF anyway? Or are you going to leave it in GRD?

[codechris 9]

It's stating it must be off for 20 seconds before another attempt. Rather then 5 seconds in off, try again, for example

[Spin737 102]

So if you get an abnormal engine start wouldn't you place the starter to OFF anyway? Or are you going to leave it in GRD?

 

It depends. If you have a hot or hung start or no EGT, I would motor the engine. If you had no N1 or N2, I'd simply go to OFF on the START SWITCH.

 

For no oil pressure, my book still says to motor it. Not so sure on that one, but that's what it says.

[Driver170 42]

Do you ever start the stopwatch for engine starts? What do you mean motor the engine? Is that keeping the start switch to GRD?

[Mariopilot 9]

The meaning of the procedure is simly not to overheat the starter system. Therefore you wait for cooldown after a failed start.

"Motoring" the engine means cranking it but not allowing fuel in. If a start failed fuel was likely injected in the combustion chamber. Motoring the engine will blow it out, otherwise it may cause anything from a hot start to a fire on next attempt depending on how much fuel accumulated!

[badderjet 181]

Do you ever start the stopwatch for engine starts? What do you mean motor the engine? Is that keeping the start switch to GRD?

 

I always do that. Start the timer once the valve is open (that way you'll know when the two minutes are over), also I note the time when I place the start lever to idle. That way you know (+10 sec) when EGT should increase at the latest. I assume not many do this, but it might be worth a thought at least.

 

Motoring the engine means running the starter, yes.

 

[Driver170 42]

Thanks alot guys! Does anyone have any good articles i can read on about all of this? Also the correct procedure when using the stopwatch for monitoring ?

So if i place the switch to GRD i can keep it at that position for 2 mins MAX ?

[Spin737 102]

I just turn the start switch and hit the timer at the same time. Easier in the plane than in the sim, I suppose. You could just use an actual stopwatch or your phone or whatever works.

 

This is one thing the sim can't do: simulate where your limbs go and the muscle memory from practice.

[Driver170 42]

So what exactly is max motoring is it where your leaving the start switch on and not moving the fuel lever to IDLE at 25% N1. So N2 would be at 28 ?

[pcubine 143]

So what exactly is max motoring

Do you know what the Internet is for? https://books.google.com/books?id=J6wnCQAAQBAJ&pg=PA193&lpg=PA193&dq=max+motoring+737&source=bl&ots=wuEW-W6aTU&sig=IWFhRg5nszqlgLSGykpiJLBkZU0&hl=en&sa=X&ei=d7uBVaayNIGesQW_mYKYDg&ved=0CG8Q6AEwDQ#v=onepage&q=max%20motoring%20737&f=false

[captain_adf 16]

Great link. Max motoring is reached when N2 does not increase by more than 1% within 5 seconds. A lot of sim videos and tutorials get this wrong and tell you to flip the fuel lever when N2 reaches 25% or 22% but that's actually not the right procedure and risks a hot start.

 

My method is to keep a close eye on N2 as the rate of increase slows, start counting the seconds each time the single digit (1%, not the tenths digit) turns over. If you get to 5 and you're still on the same digit, introduce fuel.

[JoeDiamond 67]

 

 

A lot of sim videos and tutorials get this wrong and tell you to flip the fuel lever when N2 reaches 25% or 22% but that's actually not the right procedure and risks a hot start.

 

25% N2 or max motoring with a minimum of 20% if 25% is not achievable is what's in our manual.

[Driver170 42]

Michael yes! But looking for a good explanation on what that term means.

A lot of sim videos and tutorials get this wrong and tell you to flip the fuel lever when N2 reaches 25% or 22% but that's actually not the right procedure and risks a hot start.

 

Well there must be some wisdom in boeing saying that you need to put the start lever to idle at 25% or they would have mentioned to wait till the N2 reached max motoring