How to set Magnetos for Starting???

[AirbusPilot]

Hi,

I have a Lycoming IO-360-M1B from Vans in my RV-8, my engines has a Slick 4373 and a 4370, I think but not sure just the left one is a impulse coupling magneto so I understand that I should start my engine with just left magneto ON and the right one grounded.

Please confirm because I have never start any aircraft (Cessna old 150, 172, 210, Piper Cherokee, etc) that I remember with just left magneto, always both.

Thanks,

[rwhittier]

with the right grounded. If only one is a IC mag. That is normal on a lot of planes.

Originally Posted by AirbusPilot

Hi,

I have a Lycoming IO-360-M1B from Vans in my RV-8, my engines has a Slick 4373 and a 4370, I think but not sure just the left one is a impulse coupling magneto so I understand that I should start my engine with just left magneto ON and the right one grounded.

Please confirm because I have never start any aircraft (Cessna old 150, 172, 210, Piper Cherokee, etc) that I remember with just left magneto, always both.

Thanks,

[yakdriver]

If you have a key switch it should ground the right mag when you engage the starter. If you just have a right and left mag switch you start it on the left mag.All of the airplanes you mentioned have a key switch that grounds the right mag when the starter is engaged. Don

[az_gila]

Originally Posted by rwhittier

with the right grounded. If only one is a IC mag. That is normal on a lot of planes.

...switch, the right is grounded when the key is in the "Start" position.

That's why the Cessnas and Pipers don't usually have "Left mag for start" in their Check Lists....

[Andy Hill]

Just to clarify, the RH Mag being grounded during start by the Start Switch. This is not necessarily the case, it is an option with the Switch - via a link present or removed. For instance, our RV-8 has the standard Key Mag/Start switch, yet leaves both Mags on for start (Dual Impulse Slicks).

Andy Hill
RV-8 G-HILZ

[AirbusPilot]

Originally Posted by az_gila

...switch, the right is grounded when the key is in the "Start" position.

That's why the Cessnas and Pipers don't usually have "Left mag for start" in their Check Lists....

Hi,

The thing is that I fly an old cessna 150 (continental O-200) and 172 (lycoming 0-360). Both aircraft start check list said to set switch magnetos to both but those aircraft have a separate start bottom from the switch. So does those aircraft have both magnetos with impulse coupling or may we starting them with the wrong procedure for years????

Cheers,

[brianwallis]

Originally Posted by AirbusPilot

Hi,

The thing is that I fly an old cessna 150 (continental O-200) and 172 (lycoming 0-360). Both aircraft start check list said to set switch magnetos to both but those aircraft have a separate start bottom from the switch. So does those aircraft have both magnetos with impulse coupling or may we starting them with the wrong procedure for years????

Cheers,

Only the left mag has the impulse coupling, and it's the one that will provide the juice to get it started, the right mag comes online once operational rpm is attained.

[Mel]

Originally Posted by AirbusPilot

Hi,

The thing is that I fly an old cessna 150 (continental O-200) and 172 (lycoming 0-360). Both aircraft start check list said to set switch magnetos to both but those aircraft have a separate start bottom from the switch. So does those aircraft have both magnetos with impulse coupling or may we starting them with the wrong procedure for years????

Cheers,

If the starting procedure says to set the switch to "both", then chances are pretty good that the engine is equipped with dual impulse magnetos. Otherwise, you would be replacing starter drives regularly.

[AirbusPilot]

Originally Posted by Mel

If the starting procedure says to set the switch to "both", then chances are pretty good that the engine is equipped with dual impulse magnetos. Otherwise, you would be replacing starter drives regularly.

Thanks for the answer, anyway I will check what kind of magnetos has those aircraft because they do not have an original check list and also at list 150 has lot of maintenance troubles with the starter

[Mel]

Originally Posted by AirbusPilot

Thanks for the answer, anyway I will check what kind of magnetos has those aircraft because they do not have an original check list and also at list 150 has lot of maintenance troubles with the starter

Another point is that the older starters turned much more slowly than the modern ones. The older starters may have been so slow that the early firing of a non-impulse mag wasn't such an issue. I assure you that the modern starters will create a problem if a non-impulse mag is on line during start.