At American we use ignitor 1 for the captains legs and 2 for the FOs. We start engine 2 first so we can have the right pack operating from the right engine with the isolation valve closed and the left from the APU in case we want to do a single engine taxi. When it comes time to start the left engine all we have to do is switch the left pack off and we still have AC from the right side. The first four of five years we operated the 737 we just started engine 1 first but came up with this procedure when the fuel prices started to skyrocket.

Except for flameout protection, CONT is similar to FLT but, with CONT you can select if using one or both sparks. With FLT the sparks are always both powered.CONT and GRD are also able to power both sparks regardless of ignition switch position if a flameout is detected in flight. But this is off topic.

The igniter switch is not normally put in BOTH according to the normal procedures guys. It stays in one position or the other for the duration of the flight and then is switched for the next flight. This evens out over time.

This adds more sense about using FLT to light up both sparks ;)

If FLT is Bad Weather what is CONT then?!?!?!

Takeoff, landing, TAI ON. My company turns if on for Crossfeed, too. Not quite sure why. I'd guess it's something to do with "That's how we did it on the Mudhen!" Or 727. Or Coronado. . .

Daniel,as spin 737 said, the right position is often choosen to test the right spark functionality as it is the only working spark in case of emergency.When we say RIGHT SPARK or RIGHT IGNITION, we talk of the right spark on both engines. Each engine has a left and right spark, so there are:Left engine, left spark,Left engine right sparkRight engine left sparkRight engine right spark.With the ignition switch you choice the lh and/or rh spark ON BOTH ENGINES.If you select L you will power left and right engine LEFT spark...Now, I don't know what the pilot said you, maybe you misunderstood something.The reason for right engine start is only for pneumatic system design, it is a preferred sequence to limit the dual bleed condition.There is nothing related to hydraulic leakages as there cannot be hydraulic leakages on the aircraft either running eng1 first or not.As a more correct procedure (for me) is to let the left spark works more than the right one, like using the right one for the first flight of the day, than after some trips, and use till its death the left one, this will result in a longer life of the right ignition system.However, less you use it, less you test it for operation...Using the right one more than the left one will increase the risk of having a right spark failure wich can lead in troubles during the flight or delays for ground operation (spark replacement or ignition swap)

thanks Andrea, the pilot told me that the put system A hydraulic off for the pushback.

thanks Andrea, the pilot told me that the put system A hydraulic off for the pushback.

That's true in case of pushback made without the bypass pin wich depressurize the steering mechanism. The steering system uses SYS A hydraulic pressure, so, if A is pressurized, when the tractor or tow bar tries to steer the nose gear will find that it is forcing, in that case, the tow bar HOPEFULLY breaks before the steering (it is designed to do that) but you have stressed the nose gear components and damage (with also hyd leakage) is possible.The bypass pin will lock the hyd supply and connect the actuator tubes to the system returns to let the actators to be freely moved.If you (ground personnel) don't have the bypass pin you must turn off both A pumps, or ELEC A with engine 1 started only after pushback.

Takeoff, landing, TAI ON. My company turns if on for Crossfeed, too. Not quite sure why. I'd guess it's something to do with "That's how we did it on the Mudhen!" Or 727. Or Coronado. . .

I only imagine a condition of missing safety for fuel contamination as the engines are feed by the same tank, so to restore a degree of safety, they want the ignition running. if fuel of the tank supplying both engines is contaminated you risk a double engine shut down istead of a single engine.But this is what I suppose, I don't know if there are other reasons.

Daniel,as spin 737 said, the right position is often choosen to test the right spark functionality as it is the only working spark in case of emergency.When we say RIGHT SPARK or RIGHT IGNITION, we talk of the right spark on both engines. Each engine has a left and right spark, so there are:Left engine, left spark,Left engine right sparkRight engine left sparkRight engine right spark.With the ignition switch you choice the lh and/or rh spark ON BOTH ENGINES.If you select L you will power left and right engine LEFT spark...Now, I don't know what the pilot said you, maybe you misunderstood something.The reason for right engine start is only for pneumatic system design, it is a preferred sequence to limit the dual bleed condition.There is nothing related to hydraulic leakages as there cannot be hydraulic leakages on the aircraft either running eng1 first or not.As a more correct procedure (for me) is to let the left spark works more than the right one, like using the right one for the first flight of the day, than after some trips, and use till its death the left one, this will result in a longer life of the right ignition system.However, less you use it, less you test it for operation...Using the right one more than the left one will increase the risk of having a right spark failure wich can lead in troubles during the flight or delays for ground operation (spark replacement or ignition swap)

Hi Andrea, could you explain a bit more about limiting the dual bleed condition?Engine bleeds are left ON to reduce workload and prevent possible errors.But what about isol valve? Wouldn't it be better to close it after engine 2 start? Could it be on AUTO during the whole start sequence?Thank you.

Hi Andrea, could you explain a bit more about limiting the dual bleed condition?Engine bleeds are left ON to reduce workload and prevent possible errors.But what about isol valve? Wouldn't it be better to close it after engine 2 start? Could it be on AUTO during the whole start sequence?Thank you.

Isolation valve isolates L and R packs, it is open during start sequence, since APU provides air to L pack only, if the isolation valve is closed, R pack won't recieve any air (from L pack) and thus you wouldn't be able to start right engine. During the rest of the flight it usually is on AUTO.

Isolation valve isolates L and R packs, it is open during start sequence, since APU provides air to L pack only, if the isolation valve is closed, R pack won't recieve any air (from L pack) and thus you wouldn't be able to start right engine. During the rest of the flight it usually is on AUTO.

Isol valve isolates leff and right bleed air ducts. You could start engine 2 with the valve open and then close it before starting engine 1, but that's not the normal procedure.

Hi Andrea, could you explain a bit more about limiting the dual bleed condition?Engine bleeds are left ON to reduce workload and prevent possible errors.But what about isol valve? Wouldn't it be better to close it after engine 2 start? Could it be on AUTO during the whole start sequence?Thank you.

The APU bleed feeds the left side of the pneumatic system, same for engine number 1, by starting the right engine first, you will have,after the start, 2 independent systems (left and right) if you close isolation valve, this letting you use of right pack for example.But, it also protect the system for having 2 sources on the same side (dual bleed).If you start engine 1 first, you will have 2 sources on the left side, and nothing on the right one, 2 sources on the same side is also a possible problem (expecially for APU) in case you advance thrust. The system is protected against damages by using check valves, but it is always better to limit the danger.Isolation valve is a valve wich connects the left side to the right one, it must be on each time you need to supply one side air to the other side user/s.It is used to start the right engine with APU air, to connect APU to both wing AI, to run right pack with APU, or maybe used to let one engine to supply both sides and so on...The AUTO position is sufficient to let the system open and close the valve when needed, so leave it to the auto position and you will forget it in normal operation.ENG bleeds are left to ON as the valves are pneumatically operated and controlled by the engine logics. So, the valve needs engine running to have sufficient force to open, it is also inhibited during starting sequence so it will open only when the starter switch goes to OFF. Putting them to OFF before start is more workload, and a possible missed item that could result in something bad in air.

Thanks Andrea! I didn't know the engine bleeds valves where inhibited by the starter. I read about it in the fcom but missed that.

The AUTO position is sufficient to let the system open and close the valve when needed, so leave it to the auto position and you will forget it in normal operation.

So why the preflight normal procedure says the valve should be open? Is it because you can run both packs with apu bleed that way?Bye.

Thanks Andrea! I didn't know the engine bleeds valves where inhibited by the starter. I read about it in the fcom but missed that.So why the preflight normal procedure says the valve should be open? Is it because you can run both packs with apu bleed that way?Bye.

To ensure valve is opened and both packs are pressurized.

The ignition switch select wich of the sparks (there are 2 for each engine, left igniter and right igniter) works when you start the engine(on ground) or when you select CONT.Normally you use only a spark at time to start the engine.But,you may need both sparks when you put the switch to CONT (bad wheater, TO and landing...).With good wheater, you can use CONT with one spark for TO and landing, you may use both if higher risks of flame out are present.The engines will self protect from flame out, but a little help is a good practice.When you select FLT the switch is disregarded and both sparks will work.

So L and R doesn't mean left and right engine but left or right spark?Bert Van Bulck

Thanks Andrea! I didn't know the engine bleeds valves where inhibited by the starter. I read about it in the fcom but missed that.So why the preflight normal procedure says the valve should be open? Is it because you can run both packs with apu bleed that way?Bye.

I don't know why checklist prefer to force the isol. valve in a open position, maybe is to prevent a wrong valve position due to a possible logic failure, but, it is something that will difficulty happens.To run both packs with APU you need to turn to OPEN the isolation valve or turn off one of the engine bleeds (also if engines are off). This will open the isolation valve if in AUTO position..

So L and R doesn't mean left and right engine but left or right spark?Bert Van Bulck

Exactly

I've just read that the apu burns more fuel when operating a single pack than both of them.Thanks for the answers.