Will turning off the master switch before turning off the magneto affect the magneto? (C172)

Funflight

Funflight

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Funflight
Hello guys, I have a question about shutting down procedures. (C172)

According to the checklist, the original order is

Mag off -> Master Off

But I usually do

Master off -> Mag off

I was confused about the order.

Left Magneto broke down a few days ago, could this be the cause?

Thx! have a great night.
 
The magneto broke because it broke. You didn’t do anything wrong.
 
midlifeflyer said:
I've even turned off the master while flying :eek::eek::eek::eek:
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I did that the other day in imc. Switched fuel tanks, reached for the fuel pump switch, and hit the master instead. I about had a heart attack when the gtn went black...

To the OP, you need to review your systems knowledge a bit. The whole point of having magnetos on our engines is to make them independent of the electrical system. If your instructor didn't shut the master off in flight to demonstrate that, they did you a disservice.
 
Jim K said:
did that the other day in imc. Switched fuel tanks, reached for the fuel pump switch, and hit the master instead. I about had a heart attack when the gtn went black...
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I did it on purpose. I was with a student who was absolutely convinced the electrical system (battery/alternator) made the prop turn in flight and it would quit if the master were switched off.
 
Clip4 said:
Op, I hope you are a pre solo student.
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This is the kind of thing that isn't on the PTS, so doesn't always get taught. I suspect there are instructors out there who don't really understand some of these simple systems too. Ain't their job, they might say...

But it is really good information to know.
 
Jim K said:
I did that the other day in imc. Switched fuel tanks, reached for the fuel pump switch, and hit the master instead. I about had a heart attack when the gtn went black...
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Did that once while exiting the runway, turned off the master instead of the fuel pump, just as tower told me to contact ground. Um yeah, hang on a minute...
 
Closest I ever got to something like that was my instructor trying to be subtle in pulling the power back and she pulled the mixture instead. The big spinny thing got quiet and I asked if she intended to cut the engine off.
 
Bill said:
Did that once while exiting the runway, turned off the master instead of the fuel pump, just as tower told me to contact ground. Um yeah, hang on a minute...
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I used to raise the flaps, turn off strobes, turn off landing light while taxing off the runway until I started commercial training. Now I wait until I am clear of the runway, announce that. Then while stopped off the runway I do the above. Helps insure I don't retract the gear or something stupid like that while taxing.

When I shutdown, I first turn off the avionics switch. Then I switch the mags off for a second to make sure to P leads are still attached. Then pull the fuel to kill the engine. Then I remove the key and place it on the glare shield so I can see it when I go to move the plane. The master switch is the last thing I turn off. If I forget the master I will notice because I leave the beacon switch on and I will see it flashing in the hangar while pushing the plane in. Seems to work pretty good for me. I do it the exact same every time.
 
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kyleb said:
This is the kind of thing that isn't on the PTS, so doesn't always get taught. I suspect there are instructors out there who don't really understand some of these simple systems too. Ain't their job, they might say...

But it is really good information to know.
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Not in the pts specifically, but I would be shocked if not covered in the oral.

My examiner even quizzed me about which engine gauges were electric and which were mechanical, and what would they indicate if we lost electrical power.

Systems can be very hard for people who didn't grow up wrenching on stuff. Even then magnetos would be unfamiliar to anyone not working on 1930's tractors, although I do have a single cylinder Wisconsin engine from the early 80's with a magneto on it. Even has an impulse coupling that you can hear go "clunk clunk" as you turn it over.
 
Bill said:
Anyone who's used your average pull start rotary lawn mower has used a magneto lol.
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That's true, but my point is how many people work on them, and understand them? Magnetos on small engines tend to outlast the rest of the motor in my experience.
 
@Funflight , you have the answer to your question now. But I’m wondering about this from your post:

According to the checklist, the original order is

Mag off -> Master Off

But I usually do

Master off -> Mag off

I was confused about the order.

Are there other things in other checklists you are confused about?
 
Jim K said:
I did that the other day in imc. Switched fuel tanks, reached for the fuel pump switch, and hit the master instead. I about had a heart attack when the gtn went black...

To the OP, you need to review your systems knowledge a bit. The whole point of having magnetos on our engines is to make them independent of the electrical system. If your instructor didn't shut the master off in flight to demonstrate that, they did you a disservice.
Click to expand...
Ouch. How long does it take for the GTN to spool back up and be useful?
 
Jim K said:
I did that the other day in imc. Switched fuel tanks, reached for the fuel pump switch, and hit the master instead. I about had a heart attack when the gtn went black...

To the OP, you need to review your systems knowledge a bit. The whole point of having magnetos on our engines is to make them independent of the electrical system. If your instructor didn't shut the master off in flight to demonstrate that, they did you a disservice.
Click to expand...

I know the feeling.
Jim K said:
That's true, but my point is how many people work on them, and understand them? Magnetos on small engines tend to outlast the rest of the motor in my experience.
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Anyone remember Vertex magneto's? I used to drag race a methanol injected big block V8 engine with one. It was so much more reliable than a MSD system 7AL system and ran really well. Am a long time lover of magnetos.

Then did switch to 44 amp MSD mags on a supercharged hemi.
MVC-893S-1.jpg
 
When shutting down I go with the flow, starting at the right of the switch panel and move left. In this case, trim power off, strobes off, avionics master off, then pull to idle cutoff. After the blades stop, master off, then mags off.

upload_2021-7-23_8-4-6.jpeg
 
Funflight said:
Left Magneto broke down a few days ago, could this be the cause?

Thx! have a great night.
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How many hours are on the mag that broke?

I lost my alternator earlier this year right at dusk. Luckily I was 7 miles from my airport and had no trouble flying back with everything off except the mags switches.
 
luvflyin said:
Does it remember anything about where it was? Or do you have to reload a Flight Plan?
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You get to re-load everything, hopefully you stored the flight plan to a memory location lol!
 
Bill said:
Anyone who's used your average pull start rotary lawn mower has used a magneto lol.
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But no points. Those went the way of dinosaurs prolly 30 years ago.

You may not have known that because, without points to fail, there is no reason to pull the flywheel.

Thank God that aircraft still use good old Model T technology.

 
luvflyin said:
Ouch. How long does it take for the GTN to spool back up and be useful?
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Not sure, but it felt like hours lol.

Thankfully I was direct cmi at the time, so it wasn't bad to get back. I figured atc would ask where my txdr went, but nobody said a word.
 
kyleb said:
This is the kind of thing that isn't on the PTS, so doesn't always get taught. I suspect there are instructors out there who don't really understand some of these simple systems too. Ain't their job, they might say...

But it is really good information to know.
Click to expand...
This is the kind of stuff that is taught in a real private pilot ground school.
 
luvflyin said:
Does it remember anything about where it was? Or do you have to reload a Flight Plan?
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That's where an iPad and FS 210 or 510 is helpful. Reload through bluetooth as soon as GTN comes back to life.
 
Jim K said:
I about had a heart attack when the gtn went black...
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My GTN went black for real in IMC a couple of years ago, along with the rest of my avionics stack (due to a broken avionics master switch). Definitely an attention getter, but not heart-attack worthy, even figuratively — my vacuum pump kept sucking and spinning those gyros, my pitot-static system kept sending varying air pressure to my ASI, ALT, and VSI, and unlike in the old days, I had a backup navigation system in my pocket (Garmin Pilot on my Android).
 
David Megginson said:
My GTN went black for real in IMC a couple of years ago, along with the rest of my avionics stack (due to a broken avionics master switch). Definitely an attention getter, but not heart-attack worthy, even figuratively — my vacuum pump kept sucking and spinning those gyros, my pitot-static system kept sending varying air pressure to my ASI, ALT, and VSI, and unlike in the old days, I had a backup navigation system in my pocket (Garmin Pilot on my Android).
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Cessna amended their maintenance manuals for the R and S models to include a five-year (IIRC) master and avionics switch replacement. Sudden loss of both the PFD and MFD and all the radios can be disconcerting. It seems that some pilots don't turn on the standby power switch when they start up, thinking they're saving the standby battery. They're not; it get charged during normal operation and that prevents sulfation from disuse. If they hit that switch after the airplane's electrics have died, they have to wait awhile for anything useful to show up.
 
Dan Thomas said:
Cessna amended their maintenance manuals for the R and S models to include a five-year (IIRC) master and avionics switch replacement. Sudden loss of both the PFD and MFD and all the radios can be disconcerting.
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The standby battery should prevent sudden loss of the PFD. After all, the engine is started with the master+avionics switches off, the STBY switch armed and the EIS on the PFD.
 
Dan Thomas said:
Cessna amended their maintenance manuals for the R and S models to include a five-year (IIRC) master and avionics switch replacement. Sudden loss of both the PFD and MFD and all the radios can be disconcerting. It seems that some pilots don't turn on the standby power switch when they start up, thinking they're saving the standby battery. They're not; it get charged during normal operation and that prevents sulfation from disuse. If they hit that switch after the airplane's electrics have died, they have to wait awhile for anything useful to show up.
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asicer said:
The standby battery should prevent sudden loss of the PFD. After all, the engine is started with the master off, the STBY switch armed and the EIS on the PFD.
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That all makes perfect sense for glass instruments. In the two cases mentioned, though, we're talking about a Garmin GTN navigator (GPS, VOR, COM), which does not have a backup battery.
 
asicer said:
The standby battery should prevent sudden loss of the PFD. After all, the engine is started with the master+avionics switches off, the STBY switch armed and the EIS on the PFD.
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Master has to be on or the starter won't work. The engine can be stsrted with the avionics and standby off.
 
Dan Thomas said:
Master has to be on or the starter won't work. The engine can be stsrted with the avionics and standby off.
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Oops, yes. Master on, avionics off.
I blame lack of caffeine.
 
Reminds me of the thread about the constant speed prop putting oil in the fuel tanks.
 
Gary Ward said:
Anyone remember Vertex magnetos? I used to drag race a methanol injected big block V8 engine with one. It was so much more reliable than a MSD system 7AL system and ran really well. Am a long time lover of magnetos.
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I was introduced into the world of magnetos as an unpaid 14 year old kid while working on a sprint car team. It was my first racing gig, which eventually led to the Indianapolis Motor Speedway and the Bonneville Salt Flats.

The sprint car was kept in my Dad's busy commercial sheet metal shop, which sponsored said sprint car. I was a lowly mud scraper and gofer. One day the chief mechanic handed me a magneto, and said "Grab that wire coming out of the housing and hang on to it.", to which I unquestioningly complied.

He then reached over, grabbed the drive gear, and gave the shaft a hard twist. I was of course unprepared for the healthy shock the magneto produced, and fell on my a$$ in surprise. Everyone in the shop got a big laugh at my expense.

:eek::rolleyes:
 
3393RP said:
I was introduced into the world of magnetos as an unpaid 14 year old kid while working on a sprint car team. It was my first racing gig, which eventually led to the Indianapolis Motor Speedway and the Bonneville Salt Flats.

The sprint car was kept in my Dad's busy commercial sheet metal shop, which sponsored said sprint car. I was a lowly mud scraper and gofer. One day the chief mechanic handed me a magneto, and said "Grab that wire coming out of the housing and hang on to it.", to which I unquestioningly complied.

He then reached over, grabbed the drive gear, and gave the shaft a hard twist. I was of course unprepared for the healthy shock the magneto produced, and fell on my a$$ in surprise. Everyone in the shop got a big laugh at my expense.

:eek::rolleyes:
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Cool story, sounds familiar about the mag...lol
I was only a lowly drag racer and have never been to a speed week at Bonneville, but I did drive my muscle car on the salt at Bonneville just for ****s and giggles several times back around 2010. We used to have family in Sacramento and we would drive our RV rig and open trailer out there about once a year to visit. We would stop at Wendover for the night. My wife would go in the casinos and I would drive my car out on the roads out there. Keep it on the street on the way out there and then drive it on the salt on the way home. I have been out there about 6 times and drove the car on the salt three times three different years.
Californiatrip7-1-10857-1.jpg

This car has been driven on all 4 coasts, top of Pikes Peak twice, across the Golden Gate, Daytona Beach in the sand, Key West and much more.
Californiatrip7-1-10181.jpg

I kept my toterhome after racing, sold my 49' enclosed race trailer and started pulling this open trailer with one of my muscle cars on it just for a driver car to get around when we were camping. Had way more fun pulling the open trailer than we did the enclosed because it was easier to pull and people could see what was on it. They used to ask on the CB what was in the enclosed trailer. With the open trailer we would get thumbs up all day long.
Californiatrip7-1-10916.jpg
 
That's very cool. The salt is something all racers should see. There's a lot of history there.
 
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