Should I use seperate switches for mags?

[gizmos]

Rotax 100hp three blade prop, should I use two mag switches or use the standard Cessna type key switch/mags?

[Planesmaker]

I would go with seperate switches. Because rotax run AC powered CDI's there has been some problems ( occasionally) with key type switches.

[Av8r3400]

Yes. Two separate switches.

[mr bill]

I like the having ability to turn the engine over without starting it. I use two rockers for ignition and a momentary key switch for starting.

[SkySteve]

A related question: When turning the engine off, do you shut down one mag, then the second, or both at the same time?

[DesertFox4]

Two switches, push button start switch, no key. Both off at the same time.

[jiott]

I read somewhere, probably this forum, that it is a good idea to turn off one mag and wait a second or two, then turn the other off. It slows the idle speed somewhat so the final shutoff is less abrupt; supposed to be better for the gearbox. I have been doing this for several years now and I do believe it gives a smoother shutdown.

[DesertFox4]

I can usually get very smooth shut downs with no abrupt compression stops but that has to do with throttle manipulation during shut down.

[jiott]

DF4, so how do you manipulate the throttle?

[DesertFox4]

This method goes back to almost the first 912uls installed on a Kitfox.

Run up rpms to about 2500 and as you shut off ignition be pulling the throttle back to idle. Takes some practice to get the timing down but most times I can get a very smooth stop. I do have my idle set to about 1400 rpms.

[jiott]

Thanks, I'll give it a try.

[jiott]

DF4, I tried your shutdown method today and I like it! Quite smooth.

[kitfox2009]

Hi all
Having separate module switches allows you crank over a bit until oil pressure builds. These startups should improve engine life. On first startup of the day I usually pull the enricher during the oil pressure cranking phase.
Also, on shut down well timed throttle and module shut off works well.
Over 650 hours on a UL now with no problems.
Don

[Planesmaker]

I agree, I just found recently that if I increase revs a little it is a smoother shut down. I also allow oil p to come up before starting. Tom

[jtpitkin06]

The following is not pontificating, just friendly hangar flying. FWIW.

When an ignition module or magneto coil fails in flight, very few pilots will notice it. A small drop in RPM signaling the failure is usually met with a throttle correction and the pilot continues the flight. Only when the mag fails with a noticeable roughness does the pilot consider doing a mag check in flight.

Almost all pilots do an engine run up and mag check before takeoff. But how many do an end of flight ignition check?

Here's the scenario... You taxi in and shut down the engine in the usual way. Either pulling the mixture, or turning off the ignitions at the same time. The engine shuts down as expected. Unknown is one of the mags/modules has failed. It runs just fine on the remaining ignition.

You park the airplane and look forward to the big fly in just five days away. Wouldn't it be nice to know now about that bad mag/module now instead of getting the bad news during your next run up?

There's no need to do a run up at the end of the flight. Just do a quick mag check at idle power. You'll avoid bLowing dirt around the ramp and if a mag is inop, you'll prevent a backfire.

For engines that shut down by pulling the mixture be sure to check the both off position, too.

I hope this will prevent someone from cancelling a flight because they didn't know they had a bad ignition at the end of the last flight.

John P

[Dave S]

John,

I think there is a great deal of wisdom in your comments. I recall back in primary training the instructors were wanting people to do that very thing.....not sure everyone did.....one reason was to find if there was a broken P lead, the other reason was to know one mag had not failed during operation and gone unnoticed.

[jrevens]

That was good advice, John. I've had the habit of doing that since I learned to fly in the early '70s. Additionally, I always do a post-flight check in the hangar. I want the airplane to be ready to go when I am. 99% of the time I can't leave the airplane after a flight without cleaning the bugs off also... drives some of my friends crazy. :confused:

[jiott]

I do the same John, cleaning bugs and dirt postflight. When you do this it makes you look the whole airplane over like a mini preflight.