Inflight Mag Check

[C/SrA Ravlin]

When I say to run the one with higher rpms you only do this in an emergency situation... One of the mags will run better than the other and if you having trouble with one then switch to the other... The other will often run with higher rpms than the one that is having issues. Again this is for emergencies only!!!! Doing this under normal circumstances can be dangerous... And someone please correct me if I am wrong because I am a learning student pilot and need to know the correct version if this is incorrect. Also this completely depends on the plane you are flying. As stated earlier with the fuel selector issue. If there is water in the fuel than the engine will either quit or run extremely rough until the water is gone. Again please correct me if I am wrong...

[Flying Pig]

What airplane are you referring to.  I have about 1800hrs in FW in 172s, 182s, 206s, 210s, Warriors, Tomahawks, Arrows.....  Ive never heard of or read any procedures to switch to "the good Mag" and run the RPMs higher.  Instead of asking us if you have it wrong, show us where you were taught or read that.  There could be a plane out there that has that.  I would sincerely like to know which one it is.  Maybe I missed it.  This sounds more like a procedure someone used once or something thats been handed down over the years and nobody knows who made it up.  If one Mag is bad, rough is rough.  Im not a mechanic, but Im not seeing how shutting the bad one down improves your situation.
Running at higher RPMs compared to what?  RPMs are RPMs.  So do you now land faster because you have a bad mag?  Just saying "run at higher RPMs" leaves a lot out of the scenario.  Is this a constant speed prop? Fixed Pitch?  Is there a corresponding air speed you are looking for? Do you ever go to "Both" again?  What about 1-Mag go around procedures?  All these things would need to be addressed if this is a written EP.  Also... I wouldnt necessarily treat a bad mag as an Emergency.  You said "You only do this in an emergency".  So is that an Emergency.... and then you lose a mag?  Or does losing the mag make it an emergency situation?  If it does, simply go to the EP section of your POH and tell us what it says.

[Flying Pig]

If you ever fly for CAP as a Mission Pilot (or fly anything)....... beware of the official looking home made checklist the pilot before you leaves in the airplane.  Sometimes they can be quite entertaining   

[Luis R. Ramos]

There are lots and lots of things in life that I have learned from books, or done but I would never ever think to offer advice as it was done here. I left the experts -those that have countless hours in cockpits in several airplanes- be the ones offering advice on what to do.

Can you imagine me offering advice to Flying Pig or to Shuman because once while employed as an orderly at a hospital accompanied a Security Guard in a safety sweep?

Can you imagine me offering advice to PHall, Jeff, or Cliff (among others!) on air warfare because I have read about 70 books in air warfare or airplanes plus 50 books on land warfare, plus about 20 on naval warfare?

If you were not a pilot you should have stated so. Although most guessed it by your signature, and the advice...

Even if you want to help, please do not do it until you can profer countless hours in real life...

[Panzerbjorn]

Here's the thing about aviation, no matter how much experience you have, no matter what ratings you hold, there's always room to learn things.

Here's an article from AOPA's Flight Training talking about this very thing and it supports Ravlin's advice, with a little more clarification as to why you would want to turn off a mag in flight.  Apparently, it has to do with the timing of the magnetos.  If you have a bad mag, it can either fail on you, or the timing will be off, producing a rough engine symptom similar to what a fouled plug will do.  The mistiming could cause damage to your engine, so in that sort of situation, it's not a bad thing to shut off the bad mag, run on one, and land as soon as practical.

http://flighttraining.aopa.org/magazine/2004/August/200408_Departments_Learning_Experiences.html

I concede the point because now it makes sense.  It's still wouldn't be your FIRST solution necessarily, but I can see now where you could have a situation where turning off one mag and flying on the remaining good one would be a viable solution.  But I also agree with Flying Pig, flying on one mag is really more of a land as soon as practical situation, not an emergency and have ATC clear the runways and roll the fire trucks situation.

I tip my hat, and thank you for the opportunity to learn something new.

[Flying Pig]

Ill check it out.  Thanks.   I think the issue here is the differentiation between a bad being an Emergency Procedure.  Another procedure the writer mentions is that he checks his Mags every 20 minutes.  Ive heard of people doing that, but Ive always been of the idea that if there are no indications that there is an issue, you don't need to be shutting things off during flight just make sure it will turn back on.  I see that concept the same as when I teach a student to pre-flight.... You DONT need to grab on to things and shake them to make sure the piece is still attached! 

[jeders]

Another procedure the writer mentions is that he checks his Mags every 20 minutes. 

I do this also, but mostly because my instructor likes to take away my engine about that often. For the Dakota, switching mags is the second to last item on the engine loss EP checklist tight before 'randomly start moving levers and knobs hoping the engine will restart.'

[Flying Pig]

Im just curious how good of an idea this is when you start flying high performance pistons.  I dont mean "HP" as in the FAR definition, I mean things like a T206, P210s, Matrix, etc etc.  The 206 I used to fly had the IO-540/310HP.  intentionally turning off a mag as part of a routine 20 min check seems like it would make her mad.  You get all trimmed up, auto pilot and everything running as toasty as a fire on christmas morning, I wouldnt advise switching off the mags every 20 min. Now you add non-pilot passengers.  I personally dont know any working pilots who do that as a matter of any 20 min scan.  Lets face it sometimes what we learn in flight school just needs to stay at flight school.  I think the switching off mags every 20 minutes is probably one of those things. 

[jeders]

Lets face it sometimes what we learn in flight school just needs to stay at flight school.  I think the switching off mags every 20 minutes is probably one of those things.

I couldn't agree more. My point was more that switching off mags as part of running an established manufacturer provided checklist is ok. However, switching them off just as part of a routine cross-check on a long distance flight is a bit sketchy to my inexperienced mind.

[Flying Pig]

The only place Ive seen it mentioned is AFTER your engine has already failed.  At that point... who cares.   Ill need to research a couple of my POHs and see what it talks about with rough running Mags. 

[C/SrA Ravlin]

I was taught this by a good pilot friend who I have flown with in his 150... I do not mean to run the engine at higher rpms but to run the magneto that runs better (higher rpms) instead of the rough running one. This information has been passed down the chain from my friends great grandpa who flew in WWII. I will check a few pohs that I know of to find the real procedures. One thing I do know is that planes have 2 magnetos for a reason, this is to keep the plane going if one is not working. I will do some research this week and see what I find in the poh of a few aircraft and will talk with my instructor...

[Flying Pig]

Good discussion.  Just be careful of friends passing down family secrets when it comes to flying.   You dont need to check a few POHs.  Just check the POH for the airplane you are training on and see how its discussed in the plane YOU are flying today.

[Cliff_Chambliss]

I was taught this by a good pilot friend who I have flown with in his 150... I do not mean to run the engine at higher rpms but to run the magneto that runs better (higher rpms) instead of the rough running one. This information has been passed down the chain from my friends great grandpa who flew in WWII. I will check a few pohs that I know of to find the real procedures. One thing I do know is that planes have 2 magnetos for a reason, this is to keep the plane going if one is not working. I will do some research this week and see what I find in the poh of a few aircraft and will talk with my instructor...

While the "old School" may have some nuggets of wisdom there are also many Old Wives Tales (OWTs).  Flying on the Step, Never fly over square, etc.  Even Ernest K. Gann one of the great aviation authors talks of (in the 1930's) intentionally causing an engine to backfire to clear carburetor air intake icing I don't think anyone would even consider that today.  Also, my father's old Operations Manual from Pan American Airways days in South America even discussing the retracting the landing gear on short fields to avoid running into trees (lets float that idea past the FSDO and see how far it flies).  My point is that all thing aviation are fluid and are always changing.  What may have been a good idea or even gospel in days past may have no place in todays world.  The best I can suggest is always ask "Why is this so?  What makes this a good idea?" and anytime the answer is "because that's the way it's done, It's always been done that way" or variations thereof, then file the idea away for later bar bets or trivia but don't carry into the cockpit.

NOTE:  "Flying on the step"  some old timers would say to get maximum performance climb to 200 feet above your altitude and then do a shallow dive to target altitude and trim the plane.   TODAY:  We teach Pitch-Power-Trim at the level off. PITCH to level flight, POWER leave power on until you reach the desired airspeed, TRIM adjust engine and trim to maintain level flight.
"Flying Over Square"  Old timers would preach never let manifold pressure (in in) exceed RPM.  TODAY:  Check the airplane performance charts.

NOTE 2:  Watch out for OWT's.  If it sounds odd, strange, weird, challenge the teller.  I tell all my students to challenge me if I say something that just doesn't make a lot of sense.  If I can't show it to them in the proper publications (someone else's handouts/notes don't count.  Must be FAA or equivalent publication)  then it's opinion, and that particular period of instruction is free.  However, If I show them the printed word, they buy me a soft drink.

 

[Flying Pig]

Radials vs modern engines.

[A.Member]

Good discussion.  Just be careful of friends passing down family secrets when it comes to flying.   You dont need to check a few POHs.  Just check the POH for the airplane you are training on and see how its discussed in the plane YOU are flying today.

:clap:

I agree with everything Flying Pig has stated here and in earlier posts. 

He's being much more diplomatic than I'll be.  Again, I don't know everything (or even most things) but some of the stuff I've read here just baffles my mind. I'd even go so far as to call it stupid.

[docsteve]

I've read this post beginning to end and am somewhat confused, but nevertheless I have a couple of points to make.

1) I agree that a mag check should never be done in flight ("stress" as the OP said IIRC).  However . . .

2) A rough engine may be the result of a failed magneto, and a mag check would be necessary to isolate the failed mag (e.g., the Slick mags have a habit of coming apart, which does bad things to the engine's performance while that defective mag is still operating).  I think that that has been made clear already.

3) "Getting the plane on the ground" (if I got the quote right) means, in the FAA's terms, "as soon as practicable."  While "practicable" means a suitable landing site (e.g., an airport capable of handling the aircraft in question), it also means "as soon" as possible, so it means at the first suitable landing field: remember that the aircraft is certificated to fly on two mags, not one, and any prolonged operation with only one mag functioning is an FAR violation (and a mag failure would rquire -- if IFR -- nofication to ATC under 91.183[c]).

4) About carb heat, the sequence described earlier seems somewhat off.  Carb ice causes the engine to run at a lower RPM, not necessarilly roughly; applying carb heat reduces RPM further, then -- if ice were present -- the engine sounds like it is about to explode as the water (the melted ice) runs through the cylinders (not unlike my '73 'Vette running on regular gas, a knocking sound), then the RPM surges.  I've gotten carb ice on climb-out in a 172 and just watched as the RPM very smoothly dropped-off.

It always pays to be a bit scared of the machine and not push the envelope, but it also pays to remember that at times you still wind-up flying -- scared -- by the seat of your pants.

Steve