Starter duty cycle

[Spin737 102]

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

 

Yep.

 

25% or max over 20% = give it the gas.

[Driver170 42]

So does max motoring vary depending on any conditions?

[bjratchf 80]

Yes, start timing when the start valve opens

[skelsey 765]

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

 

I'm not sure Boeing do necessarily say that, however (which is the point being made by Andrew).

 

I don't know about the 737, but the relevant section of the B747 (RR) manual start procedure is:

 

Engine START switch .................................................... Pull P2

Verify that the N3 RPM increases. P2

When N3 is at 25%, or (if 25% is not possible), at maximum motoring:

FUEL CONTROL switch .......................................RUN

 

 

looking for a good explanation on what that term means.

 

Motoring = turning the engine over using the starter motor.

Maximum motoring = the maximum achievable N2 (or N3 for triple-spool engines) on the starter motor, i.e. when N2/N3 stops increasing.

 

EDIT: everyone else got there whilst I was writing this!

[pcubine 143]

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

You remind me of Nancy Kerigan.

[Driver170 42]

You remind me of Nancy Kerigan.

 

Haha why is that?

= turning the engine over using the starter motor.

Maximum motoring = the maximum achievable N2 (or N3 for triple-spool engines) on the starter motor, i.e. when N2/N3 stops increasing.

 

Good stuff simon

[JoeDiamond 67]

So does max motoring vary depending on any conditions?

 

It can but the only time I have seen it reach max motoring below 25% is when starting with an external air cart.  Even then most carts will get you above 25% but sometimes you get a lousy one.

[Driver170 42]

Even then the NO. 2 Engine will be started with a cross bleed start.

[dave_paige 11]

The Continental manual I have says start lever to idle at 25% or max motoring, which ever comes first.

 

Dave

[Copper. 78]

Even then the NO. 2 Engine will be started with a cross bleed start.

How do you suppose #1 got started? By air start cart or by...

 

Obviously you're going to get the required speed when conducting a crossbleed start. The same can't be guaranteed when air start carting the #1

[pcubine 143]

Haha why is that?

Vernon

Do a Internet search. BTW, I misspelled her last name. It is Kerrigan. "why, why, why?" The last time I saw the post attack video her words reminded of you. It's neither complementary nor derogatory. Just a remembrance.

[captain_adf 16]

The Continental manual I have says start lever to idle at 25% or max motoring, which ever comes first.

 

Dave

Interesting, I didn't know that if you reach 25% then it's ok to go to idle. Most of the time I hit Max motoring around 27%, but if 25% is good enough then no need to wait for MM.

[Driver170 42]

How do you suppose #1 got started? By air start cart or by...

 

Obviously you're going to get the required speed when conducting a crossbleed start. The same can't be guaranteed when air start carting the #1

 

I was just saying, starting NO. 2 you're guaranteed anyway!

These are the procedures from my FCOM RW airline SOPs

 

Position engine start lever to IDLE detent when:

• N1 rotation is observed and

• N2 RPM reaches 25% or

(if 25% N2 is not achievable)

• at max motoring and a

minimum of 20% N2.

Max motoring occurs when N2 acceleration is less than 1% in approximately 5 seconds.

At 56% N2 RPM, check ENGINE START switch moves to OFF.

Do a Internet search. BTW, I misspelled her last name. It is Kerrigan. "why, why, why?" The last time I saw the post attack video her words reminded of you. It's neither complementary nor derogatory. Just a remembrance.

 

Haha thanks alot man

[Driver170 42]

With this starter motor and the maximum time 2 mins, does this mean i can switch it off and on as many times as i want untill 2 minutes, and then i would need to wait 3 minutes?

[badderjet 181]

With this starter motor and the maximum time 2 mins, does this mean i can switch it off and on as many times as i want untill 2 minutes, and then i would need to wait 3 minutes?

 

I'm pretty sure we already covered that, 10 seconds between start attempts. Anyways, tell me just one good reason why would you wanna do that.