Engine Start logics

[jimthomasjohnston]

Hi,

Should I be able to start, say, engine #2 if I have selected "Ign L" as opposed to either "Both" or "Ign R"? One would think not, however, I am. Is this an error in to logics?? Also, should I be able to start either engine without the appropriate engine bleed air open? Again, I can. Comments?

Jim

[Tomlin]

What aircraft are you dealing with?

[mauriceb]

Hi,

Should I be able to start, say, engine #2 if I have selected "Ign L" as opposed to either "Both" or "Ign R"? One would think not, however, I am. Is this an error in to logics?? Also, should I be able to start either engine without the appropriate engine bleed air open? Again, I can. Comments?

Jim

Does the same for me and does seem like an error in logic.

Maurice

[Michael Carter]

I wouldn't think you'd get a succesful start without a bleed open somewhere.

[jimthomasjohnston]

Me again,

The aircraft is a 737-700.

Jim

[Tony]

Hi,

"Ign L" as opposed to either "Both" or "Ign R

is only used for "saving", not to wear out the ignition and you can easily start engine 1 with ignition set to Right.

[Peter Dowson]

Should I be able to start, say, engine #2 if I have selected "Ign L" as opposed to either "Both" or "Ign R"? One would think not, however, I am. Is this an error in to logics??

Yes, you can, it is not an error. There are two ignition circuits in each engine. "Both" is used for emergency re-starts, in flight, in case one circuit is out. Otherwise pilots are encouraged to use Left and Right alternately on the start-up proceudre of each leg or each separate flight. This ensures any problems are detected early, on the ground.

Also, should I be able to start either engine without the appropriate engine bleed air open?

I always thought the Engine bleed air had to be closed to start it, as else the air being forced through it to turn the blades would mostly go straight out again. However, it seems that the outlet might remain closed automatically until the engine starts, making the switch position irrelevant at start. I leave them off till the engine starts, then turn the APU bleed off.

What is important is the source of air used to drive the starting process, and normally that would be the APU bleed. The only alternative is an external source of air, but I don't think pmSystems allows for that (though it may well do).

Regards

Pete