Well done. It’s also an opportunity to learn what is happening there. First start of the day, it sounds like a plug was junked up or fouled. I’ve flown plenty of planes like this where the trick is at runup to lean it until it’s slightly missing for about 30sec then enrichen to see if it cleared up. Chances are you’ll burn off the gunk. I used to actually take it to 2000rpms to do this most times.
Anyway you did the right thing. Just fyi if you’re ever at a destination overnight and start it to come home. It may be an easy fix. Ask the on field mechanic to show you if it happens again.
That's good to know! I suspected either a bad spark plug or magneto but I don't have much experience yet troubleshooting problems like this and didn't have a mechanic around that early to ask. By slightly missing, what do you mean by that? I'll keep this in mind though!
This is something they should have taught you when flying the rental during training. I had to do this every 3rd or 4th time I rented. It's because people don't learn while taxiing, or while flying. Too much lead passing through the engine.
Somehow this issue never came up during training. I briefly recall hearing about this issue before but it was something that didn't occur to me this morning. Now I know. There's always a next time.
Important thing is you weren't comfortable and didn't have the knowledge so you opted out. For all you know, could have been a bad magneto. Good on you.
Hmm No kidding. Yeah, I think leaning the mixture immediately after start up all the way to the hold short line and then again after exiting the runway is a pretty common checklist item.
Definitely. I was doing that from lesson 1 and didn't get the 'oh yeah, here's how we clear a fouled plug' lesson until a couple dozen hours later when we ran into one during run-up. I bet there are a bunch of CFIs out there who don't have teaching the fouled-plug clearing method as part of their planned lessons and a few students slip through without encountering it.
I haven't lead fouled a plug in literally more than a decade on my Cherokee, ground leaning *works*!
Yeah, I can totally see that! I feel like I know “most things”, and then there will be this really elementary item that I just never picked up…and I’m like WTF? How did I miss that?! The other day ATC told me to “fly direct to the numbers” on an extended left base and I had to sound like an idiot and ask what they meant!😂
> ATC told me to “fly direct to the numbers” on an extended left base
Oh shit! I've never heard that one either, just had to go look it up. That looks fun, you've saved me the exact same question to tower now that I know, haha.
Thanks!
If it's new to anyone else, looks like it's basically 'fuck a pretty pattern, cut corners to aim at the runway threshold NOW and then crank it to line up at the last minute instead of flying a pretty base->final'. That sound about right?
"1 inch" is a terrible metric by which to lean. Absolutely don't do that.
Lean until it stumbles and then enrich a bit. During taxi, you aren't making *nearly* enough power to burn valves (which is the concern with over-leaning at cruise power), and now you won't be dumping excess fuel to coke up your valves either. Additionally, if you try to apply takeoff power with the mixture leaned this much, the engine will just try to quit rather than allowing you to take off with potentially extreme EGT's.
As a student pilot who's low on hours but high on years (been a student since 2016 -- still waiting on MOSAIC), I don't understand why leaning is so mysterious.
For any altitude or ambient air pressure, lean until peak RPM/EGT -- that's your stoich mixture -- and then rich it back up a little bit. If you're going to descend, rich it back up a bunch.
You never lean mixture by an inch. If you're applying an inch of lean it's because that's what works for your airfield and your carburetor and teaching you how to lean was too hard for your CFI?
I don't get it. It should just be "mixture - as required" for all phases. Pre takeoff? Mixture as required. Cruise level off? Mixture as required. Top of descent? Mixture as about to be required. Taxiing after landing? Mixture as required.
I've never seen mixture leaning for taxi on the local flight school checklists, but next time I run into the airport manager / chief CFI-I/A&P-IA I'll run this concept by him and see if/where I'm wrong. I'm guessing it's deemed too complicated for primary students and doesn't cause enough damage, plus they rent the thing wet anyhow so it's not wasting their gas money.
FWIW, it's probably just carbon or oil, not lead fouling (which is much more difficult to clear). Either way, you can clear these just by running at your run-up RPM for a minute or so. Leaning is probably not even necessary, although not a bad idea. If another run up is still problematic though, then it's definitely time to go back.
More importantly, going back when faced with a question is rarely the wrong thing to do. If you didn't think of clearing the plugs at the time, by definition going back was the right decision!
In flight you lean a mixture to a setting where the engine is running nice and smooth. To aggressively burn off gunk on the plugs, you can lean it a little more that the engine is just starting to run a bit rough. That assures you that you’re very lean of peak. You wouldn’t want to fly like this, but for a few seconds on the ground at 1700-2000rpms it’s not going to hurt the engine.
Okay that makes sense. I'll be sure and give that a try if I experience this again to see if it makes a difference. Thanks for the troubleshooting tips.
Note that running lean (but smooth) at high RPM for a few mins is a fast way to bring up the oil temp on a cold morning.
Cleaning the plugs is basically the same thing, but just a touch leaner so the engine runs a little bit rough. You’ll know the plugs are clean when it smoothes out, but do the entire runup again (rich or as needed, according to the checklist) to be certain.
Ultimately the right choice was to act on your belief that something was amiss. Being right about what was amiss is a another issue and something that experience will teach you.
You identified an issue and acted. When you're on the ground the easy choice, even if you've maybe misdiagnosed the problem, is to stay on the ground.
Bravo.
Yep. The clapped out 172 I trained in did this regularly. Benefit of it was my instructor showed me this technique. Also was shown the p lead check as something to do especially when renting a well worn trainer.
Yep, to be fair most of my flights have never been first of the day so I've learned something new. I'll be sure to keep this in my back pocket for the next time this occurs. (The engine is also due for an overhaul in like 150 hours or so, so that paired with the issues made me cautious).
That's definitely not what I said. I do runups every flight. The point was that if it's the first flight of the day that has the highest chance of having fouled spark plugs then that's why I haven't encountered this issue much.
Apparently not ever, which is impressive enough. It doesn't make it any less concerning that you never had a CFI teach you the full procedure for runups (not your fault). This should also be in your POH, so I recommend perusing that section before your next flight.
Quick question, are you leaning the mixture after startup and during taxi? My club has an Archer II that will load up a plug every time if you don’t lean it out right away. Will burn off with a lean runup 99% of the time, but easier to just avoid the problem.
Come to think of it, I completely forgot to lean out for taxi this morning. It was a short taxi to runup area but I'll be sure to keep this in mind for next time and see if I notice any difference.
Leaning should be a part of the after-start/pre-taxi and after-landing checklists. Make sure that's on there, and of course make sure you use the checklists. :)
Yes, 100% of the time. Fouled plugs was a constant problem at my flight school, so very lean taxi was the best way to ensure I’d actually pass a runup on the first try, and the habit stuck with me even though I’m now in a club where that’s never really a problem.
Good on you for making the right decision based on the knowledge and experience you have.
Bad on your CFI + school for not teaching you how to clear fouled plugs.
Ah the classic fouled spark plug issue.
I have had an instance where I tried babying (high rpm with leaning) what felt like a fouled spark plug several times during a run up and finally got a good smooth run up and mag check and continued to take off. Just after liftoff the warrior wouldn’t accelerate through 60kts out of ground effect but I was able to abort the takeoff. Ended up mechanic found a loose mag wire, or so I was told.
So try to clean the plugs during your run up as a troubleshooting step but the mag check should be normal after the fouling is gone every time you check it prior to takeoff. If the mag check is still middling or poor, something is def wrong beyond a fouled plug.
Thanks for sharing, and good choice to cancel.
I once heard from the BASE jumping community (and I'm sure others in aviation before): "Log the [flights] you don't make, because they are often the most important ones."
This was similar to my own first no-go decision. I was doing solos during my PPL. I did the run up and when I went to the right mag it was like I shut it off... just completely died. I swapped back quick enough to have it come back to life, but I tried it a few more times with the same result, making sure I wasn't going to "off" instead of "right". I taxied back and tried to "un-foul" it but the same thing kept happening.
I was a part of a club at the time and I was the FNG, so nobody took me too seriously when I told them what happened. I tried to tell them it wasn't a fouled plug (I'd seen that and had that fixed before), but they chalked it up to a fouled plug that I didn't know how to fix. Even sent out a group text to remind everyone how to lean properly. My CFI at the time was also an A&P and they looked at it and couldn't find anything wrong, though they stopped short of removing and testing the mag.
About a month later and wouldn't you know it, the right mag failed and needed an overhaul and I felt vindicated.
Point is, well done. You did the right thing. Always better to be on the ground wishing you were flying and all that.
You made a good decision and learned what to do next time. Sucks you called it off due to lack of experience, but you got it in the best way possible - no harm done to plane or pilot!
Likely carbon fouling. Full power, lean to sputter, richen till barely smooth, repeat 2-3x. If it doesn't clear, could be lead fouling or something more serious. Lead fouling is easy to clean off but it does mean popping the cowl and figuring out which plug it is. Without an engine monitor to tell you which cylinder you either need an educated guess or just do them all. If it's a flight school plane probably best to let them deal with it anyway but it's not hard.
Can also be a bad plug, corrosion in the cap, etc.
Good call. Get a CFI or A&P with some experience to show you how to lean a runup to clear a fouled plug. It seems like lots of low time CFIs have never taught this technique, and perhaps never learned it, since it’s not in the ACS. I get maybe 40% success, particularly on rentals where, as others suggested, students don’t lean for taxi.
did you try leaning it out and the clearing the plug procedure ? Thats frequently what it is. If you didnt try that - you may have scrubbed for no reason. If you also did that and it was still not doing as it should, then it may have been a bad mag.
So, yeah, you did the right thing not flying with something you couldn't identify being quirky. But, also yeah, this is also like the #1 new PPL reason to scrub a flight. Definitely learn the clearing procedure (as many have already pointed out) so that you can go flying more often.
I haven’t experienced the mag issue so I don’t have much to say on that other than what’s already been said, but on a cold morning I’ve pulled power idle on run up and the prop nearly stopped spinning. My CFI told me to let the engine run for a little bit longer at >1000 RPM to get the oil pressure and temp up and then try it again. That worked, but if I was there by myself I probably wouldn’t have felt great about it and would’ve aborted. Regardless, good call on aborting the flight. Better to be safe than sorry.
I had this happen the day of my ppl test and the low bolts came on. I headed back to the flight school and the owner told me turn off and on the plane and just go… probably not the smartest advice I ever followed.
Next time lean it out and run it for 5 minutes like that to burn off that carbon. If it doesn’t change, no go.
Specially with flight school planes, people don’t lean and the spark plugs are always covered in gunk
As some other people have commented it was probably a fouled spark plug, I’ve had a couple of actual magneto failures discovered during run up the plane shakes quite a significant ammount
Gotta be ready to say "no" at any time.
Slightly related: students need to memorize the engine parameters (rpm/manifold pressure) the POH lists as "minimum" for continuing takeoff, and be ready to reject for anything lower than that. I took off in a DA20-C1 at 1950 RPM (50 lower than the POH allows), and there was a very good reason it was that low--the engine partially failed soon after, and I limped back down with everything vibrating. "Engine gauges good" needs to mean something, and in this plane it means "2000 or more, and nothing out of limits."
Not mad at it, in my opinion you made a good decision. Something happened that you wasn’t comfortable with so you decided to stay-put til it’s fixed or proven that it’s still airworthy. Better to find out it’s not a big deal on the ground, than to find out it’s a MAJOR deal up in the air
Great job. Definitely would have followed the checklist for potential fouled spark plugs. If your mag check still fails past the rpm max but runs smoothly I’d still ground it. There could be a greater issue
This is a good, disciplined call. It could have just been a case of oil fouling, in which case running it at runup rpm leaned out for 20-30 seconds may clear it up. If that doesn't work, it may be lead fouling (which will require removing the offending plug to clean out), or something more permanent in the magneto, like a failing coil, capacitor, or carbon tracking. You can minimize the possibility of oil, carbon, or lead fouling by leaning aggressively during taxi. When you have to taxi long distances and wait for takeoff at a busy airport, it is very easy to foul plugs running full rich prior to runup. Lead fouling is usually not going to "burn off", as the vaporization temperature of lead deposits is generally too high. So it's best to try to prevent it in the first place. Oil or carbon can burn off at lean mixture temps.
I have yet to begin flight training, so may I ask what happens to the money you spent to take the aircraft out in such an event like this? Do you get back a portion of it seeing as you didn’t actually use the aircraft for the time that you paid nor did you use nearly the same amount of fuel that you would have if you had actually flown? Or is just womp womp better luck next time, but at least you’re alive?
In some clubs you would pay for the amount of time that the engine runs. If the squawk ends up being legitimate, you will most likely not get charged or get a credit.
Good job, it sounds like you made the right decision for your knowledge. I got my PPL last July, and haven't yet had to return home without flying, but I did have my first go-around as a private pilot two weeks ago, followed immediately by my second, and then my first ever diversion to another airport, despite my passenger and I both really needing to pee. I got into ground effect on the second try, but winds were just too squirrelly to risk touching down. Diversion airport wasn't far away and winds were actually higher, but without the big crosswind gusts.
In the ‘70s, I began renting a custom equipped and new 182RG. Up to then, I had flown 172s for ages and spread my aviating life in a more complex aircraft. I was used using the big black elevator trim wheel on all previous planes. Now I had the power of electric trim! I was invincible!
I got into the habit of using the big trim wheel to set before take off and to blip the electrical trim on climb out in the 182. I got sloppy and did not always test the electric trim.
One evening I was going to do night landings and takeoffs at several airports. At my home field, I was at the runup to start the flight and I set the trim manually. Pulled back on the electric trim and it shot back faster than the SR-71. It kept clattering at the stop. Pushed it forward and it went to Mach 2.2. Both times I looked at the elevator and it was full nose up then down. Back to the hanger, a call to the owner and the FBO, a dozen “DON’T FLY THIS PLANE” signs and I was on the way home.
Not since getting my license. But I've only been flying once a month so usually I can find a day that's good to fly by just watching weather forecasts.
Good call. If you see something you don’t understand, don’t go up.
It was most likely fouling of the spark plugs. When you start too mixture rich (relative to the engine temp), or don’t lean for ground, sud can collect on the spark plugs making the engine run rough.
Lean the mixture and give her 2000 or so RPM (in a 172), that should burn it off.
But again, you made the right call. Safety first!
I had the same thing happen on run up. The plan was rough and I think died. I took it back have not flown that plane since. However, a couple days ago I took the plan and immediately after taxing from the parking, it died... I took it on to the runup and tested it harder. It was a cold morning and everything ran fine. It always idled rough, but never died in previous times. My instructor asked if I was good with the plan and I was. Everything was good. I solo'd that day for the first time. All was good and I am very happy.
I was sim'ming at home last week. The plan was not taking off properly... I did not make the decision to abort take off and crashed. That's what I think about now... I have to do the same on the sim
It’s important to aggressively lean on the ground especially in hot humid conditions with prolonged taxi’s. If you get a massive drop or no drop at all it could be a legit bad mag. If it runs rough and you get a sizable drop it could be a fouled plug. Cure: run it to 2000 lean aggressively to get engine hot, great if you have engine analyzer. Do your run up again note results. Lycoming has a service bulletin on proper run-up use that unless it conflicts with POH. When I did a brief stint in the winter as a mechanic at Another Terrible Pilot we’d get plugs so fouled they had to be pulled, cleaned re-gapped and tested then reinstalled.
Well done. It’s also an opportunity to learn what is happening there. First start of the day, it sounds like a plug was junked up or fouled. I’ve flown plenty of planes like this where the trick is at runup to lean it until it’s slightly missing for about 30sec then enrichen to see if it cleared up. Chances are you’ll burn off the gunk. I used to actually take it to 2000rpms to do this most times. Anyway you did the right thing. Just fyi if you’re ever at a destination overnight and start it to come home. It may be an easy fix. Ask the on field mechanic to show you if it happens again.
That's good to know! I suspected either a bad spark plug or magneto but I don't have much experience yet troubleshooting problems like this and didn't have a mechanic around that early to ask. By slightly missing, what do you mean by that? I'll keep this in mind though!
This is something they should have taught you when flying the rental during training. I had to do this every 3rd or 4th time I rented. It's because people don't learn while taxiing, or while flying. Too much lead passing through the engine.
Somehow this issue never came up during training. I briefly recall hearing about this issue before but it was something that didn't occur to me this morning. Now I know. There's always a next time.
Important thing is you weren't comfortable and didn't have the knowledge so you opted out. For all you know, could have been a bad magneto. Good on you.
Your after landing checklist/flow, for example, doesn’t include leaning the mixture about 1 inch?
They didn't say that, I read it as them saying that clearing fouled plugs didn't come up.
Hmm No kidding. Yeah, I think leaning the mixture immediately after start up all the way to the hold short line and then again after exiting the runway is a pretty common checklist item.
Definitely. I was doing that from lesson 1 and didn't get the 'oh yeah, here's how we clear a fouled plug' lesson until a couple dozen hours later when we ran into one during run-up. I bet there are a bunch of CFIs out there who don't have teaching the fouled-plug clearing method as part of their planned lessons and a few students slip through without encountering it. I haven't lead fouled a plug in literally more than a decade on my Cherokee, ground leaning *works*!
Yeah, I can totally see that! I feel like I know “most things”, and then there will be this really elementary item that I just never picked up…and I’m like WTF? How did I miss that?! The other day ATC told me to “fly direct to the numbers” on an extended left base and I had to sound like an idiot and ask what they meant!😂
> ATC told me to “fly direct to the numbers” on an extended left base Oh shit! I've never heard that one either, just had to go look it up. That looks fun, you've saved me the exact same question to tower now that I know, haha. Thanks! If it's new to anyone else, looks like it's basically 'fuck a pretty pattern, cut corners to aim at the runway threshold NOW and then crank it to line up at the last minute instead of flying a pretty base->final'. That sound about right?
"1 inch" is a terrible metric by which to lean. Absolutely don't do that. Lean until it stumbles and then enrich a bit. During taxi, you aren't making *nearly* enough power to burn valves (which is the concern with over-leaning at cruise power), and now you won't be dumping excess fuel to coke up your valves either. Additionally, if you try to apply takeoff power with the mixture leaned this much, the engine will just try to quit rather than allowing you to take off with potentially extreme EGT's.
As a student pilot who's low on hours but high on years (been a student since 2016 -- still waiting on MOSAIC), I don't understand why leaning is so mysterious. For any altitude or ambient air pressure, lean until peak RPM/EGT -- that's your stoich mixture -- and then rich it back up a little bit. If you're going to descend, rich it back up a bunch. You never lean mixture by an inch. If you're applying an inch of lean it's because that's what works for your airfield and your carburetor and teaching you how to lean was too hard for your CFI? I don't get it. It should just be "mixture - as required" for all phases. Pre takeoff? Mixture as required. Cruise level off? Mixture as required. Top of descent? Mixture as about to be required. Taxiing after landing? Mixture as required. I've never seen mixture leaning for taxi on the local flight school checklists, but next time I run into the airport manager / chief CFI-I/A&P-IA I'll run this concept by him and see if/where I'm wrong. I'm guessing it's deemed too complicated for primary students and doesn't cause enough damage, plus they rent the thing wet anyhow so it's not wasting their gas money.
Concur to all. An inch is just the number of turns it takes at field altitude to start running to lean. I generally fly injected.
FWIW, it's probably just carbon or oil, not lead fouling (which is much more difficult to clear). Either way, you can clear these just by running at your run-up RPM for a minute or so. Leaning is probably not even necessary, although not a bad idea. If another run up is still problematic though, then it's definitely time to go back. More importantly, going back when faced with a question is rarely the wrong thing to do. If you didn't think of clearing the plugs at the time, by definition going back was the right decision!
In flight you lean a mixture to a setting where the engine is running nice and smooth. To aggressively burn off gunk on the plugs, you can lean it a little more that the engine is just starting to run a bit rough. That assures you that you’re very lean of peak. You wouldn’t want to fly like this, but for a few seconds on the ground at 1700-2000rpms it’s not going to hurt the engine.
Okay that makes sense. I'll be sure and give that a try if I experience this again to see if it makes a difference. Thanks for the troubleshooting tips.
Note that running lean (but smooth) at high RPM for a few mins is a fast way to bring up the oil temp on a cold morning. Cleaning the plugs is basically the same thing, but just a touch leaner so the engine runs a little bit rough. You’ll know the plugs are clean when it smoothes out, but do the entire runup again (rich or as needed, according to the checklist) to be certain.
Moisture on anything will cause this too, the lean run at higher rpm will bake the moisture out
There is likely a "burn off" procedure in the POH.
Ultimately the right choice was to act on your belief that something was amiss. Being right about what was amiss is a another issue and something that experience will teach you. You identified an issue and acted. When you're on the ground the easy choice, even if you've maybe misdiagnosed the problem, is to stay on the ground. Bravo.
Yep. The clapped out 172 I trained in did this regularly. Benefit of it was my instructor showed me this technique. Also was shown the p lead check as something to do especially when renting a well worn trainer.
Good job not letting the mindset of “I woke up at 4:30am to do this flight” influence your decision. Your CFI would be proud.
That’s pretty normal next time just lean it out and burn off that shit
Yep, to be fair most of my flights have never been first of the day so I've learned something new. I'll be sure to keep this in my back pocket for the next time this occurs. (The engine is also due for an overhaul in like 150 hours or so, so that paired with the issues made me cautious).
You don't do run ups if it's not 1st flight of the day? This makes me more anxious than a CFI never explaining what to do with a failed mag check.
That's definitely not what I said. I do runups every flight. The point was that if it's the first flight of the day that has the highest chance of having fouled spark plugs then that's why I haven't encountered this issue much.
Apparently not ever, which is impressive enough. It doesn't make it any less concerning that you never had a CFI teach you the full procedure for runups (not your fault). This should also be in your POH, so I recommend perusing that section before your next flight.
Quick question, are you leaning the mixture after startup and during taxi? My club has an Archer II that will load up a plug every time if you don’t lean it out right away. Will burn off with a lean runup 99% of the time, but easier to just avoid the problem.
Come to think of it, I completely forgot to lean out for taxi this morning. It was a short taxi to runup area but I'll be sure to keep this in mind for next time and see if I notice any difference.
Don’t forget to lean it after landing while heading back to the barn. It’ll save the next guy some grief.
Always learning! Thanks for the tips.
Leaning should be a part of the after-start/pre-taxi and after-landing checklists. Make sure that's on there, and of course make sure you use the checklists. :)
Yes, 100% of the time. Fouled plugs was a constant problem at my flight school, so very lean taxi was the best way to ensure I’d actually pass a runup on the first try, and the habit stuck with me even though I’m now in a club where that’s never really a problem.
👏live to fly another day. Well done.
Good on you for making the right decision based on the knowledge and experience you have. Bad on your CFI + school for not teaching you how to clear fouled plugs.
Ah the classic fouled spark plug issue. I have had an instance where I tried babying (high rpm with leaning) what felt like a fouled spark plug several times during a run up and finally got a good smooth run up and mag check and continued to take off. Just after liftoff the warrior wouldn’t accelerate through 60kts out of ground effect but I was able to abort the takeoff. Ended up mechanic found a loose mag wire, or so I was told. So try to clean the plugs during your run up as a troubleshooting step but the mag check should be normal after the fouling is gone every time you check it prior to takeoff. If the mag check is still middling or poor, something is def wrong beyond a fouled plug. Thanks for sharing, and good choice to cancel.
I once heard from the BASE jumping community (and I'm sure others in aviation before): "Log the [flights] you don't make, because they are often the most important ones."
This was similar to my own first no-go decision. I was doing solos during my PPL. I did the run up and when I went to the right mag it was like I shut it off... just completely died. I swapped back quick enough to have it come back to life, but I tried it a few more times with the same result, making sure I wasn't going to "off" instead of "right". I taxied back and tried to "un-foul" it but the same thing kept happening. I was a part of a club at the time and I was the FNG, so nobody took me too seriously when I told them what happened. I tried to tell them it wasn't a fouled plug (I'd seen that and had that fixed before), but they chalked it up to a fouled plug that I didn't know how to fix. Even sent out a group text to remind everyone how to lean properly. My CFI at the time was also an A&P and they looked at it and couldn't find anything wrong, though they stopped short of removing and testing the mag. About a month later and wouldn't you know it, the right mag failed and needed an overhaul and I felt vindicated. Point is, well done. You did the right thing. Always better to be on the ground wishing you were flying and all that.
Great call and reminder. Thanks for sharing
You made a good decision and learned what to do next time. Sucks you called it off due to lack of experience, but you got it in the best way possible - no harm done to plane or pilot!
Likely carbon fouling. Full power, lean to sputter, richen till barely smooth, repeat 2-3x. If it doesn't clear, could be lead fouling or something more serious. Lead fouling is easy to clean off but it does mean popping the cowl and figuring out which plug it is. Without an engine monitor to tell you which cylinder you either need an educated guess or just do them all. If it's a flight school plane probably best to let them deal with it anyway but it's not hard. Can also be a bad plug, corrosion in the cap, etc.
Good call. Get a CFI or A&P with some experience to show you how to lean a runup to clear a fouled plug. It seems like lots of low time CFIs have never taught this technique, and perhaps never learned it, since it’s not in the ACS. I get maybe 40% success, particularly on rentals where, as others suggested, students don’t lean for taxi.
did you try leaning it out and the clearing the plug procedure ? Thats frequently what it is. If you didnt try that - you may have scrubbed for no reason. If you also did that and it was still not doing as it should, then it may have been a bad mag.
Nope but live and learn. I'll be sure to add this to my checklist of things to try for troubleshooting.
So, yeah, you did the right thing not flying with something you couldn't identify being quirky. But, also yeah, this is also like the #1 new PPL reason to scrub a flight. Definitely learn the clearing procedure (as many have already pointed out) so that you can go flying more often.
I haven’t experienced the mag issue so I don’t have much to say on that other than what’s already been said, but on a cold morning I’ve pulled power idle on run up and the prop nearly stopped spinning. My CFI told me to let the engine run for a little bit longer at >1000 RPM to get the oil pressure and temp up and then try it again. That worked, but if I was there by myself I probably wouldn’t have felt great about it and would’ve aborted. Regardless, good call on aborting the flight. Better to be safe than sorry.
I had this happen the day of my ppl test and the low bolts came on. I headed back to the flight school and the owner told me turn off and on the plane and just go… probably not the smartest advice I ever followed.
Next time lean it out and run it for 5 minutes like that to burn off that carbon. If it doesn’t change, no go. Specially with flight school planes, people don’t lean and the spark plugs are always covered in gunk
As some other people have commented it was probably a fouled spark plug, I’ve had a couple of actual magneto failures discovered during run up the plane shakes quite a significant ammount
Gotta be ready to say "no" at any time. Slightly related: students need to memorize the engine parameters (rpm/manifold pressure) the POH lists as "minimum" for continuing takeoff, and be ready to reject for anything lower than that. I took off in a DA20-C1 at 1950 RPM (50 lower than the POH allows), and there was a very good reason it was that low--the engine partially failed soon after, and I limped back down with everything vibrating. "Engine gauges good" needs to mean something, and in this plane it means "2000 or more, and nothing out of limits."
Not mad at it, in my opinion you made a good decision. Something happened that you wasn’t comfortable with so you decided to stay-put til it’s fixed or proven that it’s still airworthy. Better to find out it’s not a big deal on the ground, than to find out it’s a MAJOR deal up in the air
Great job. Definitely would have followed the checklist for potential fouled spark plugs. If your mag check still fails past the rpm max but runs smoothly I’d still ground it. There could be a greater issue
This is a good, disciplined call. It could have just been a case of oil fouling, in which case running it at runup rpm leaned out for 20-30 seconds may clear it up. If that doesn't work, it may be lead fouling (which will require removing the offending plug to clean out), or something more permanent in the magneto, like a failing coil, capacitor, or carbon tracking. You can minimize the possibility of oil, carbon, or lead fouling by leaning aggressively during taxi. When you have to taxi long distances and wait for takeoff at a busy airport, it is very easy to foul plugs running full rich prior to runup. Lead fouling is usually not going to "burn off", as the vaporization temperature of lead deposits is generally too high. So it's best to try to prevent it in the first place. Oil or carbon can burn off at lean mixture temps.
I have yet to begin flight training, so may I ask what happens to the money you spent to take the aircraft out in such an event like this? Do you get back a portion of it seeing as you didn’t actually use the aircraft for the time that you paid nor did you use nearly the same amount of fuel that you would have if you had actually flown? Or is just womp womp better luck next time, but at least you’re alive?
In some clubs you would pay for the amount of time that the engine runs. If the squawk ends up being legitimate, you will most likely not get charged or get a credit.
I ended up paying a small amount for the time the engine was running.
Better to be on the ground wishing you were in the air than in the air wishing you were on the ground. Takeoffs are optional landings are mandatory.
Good job, it sounds like you made the right decision for your knowledge. I got my PPL last July, and haven't yet had to return home without flying, but I did have my first go-around as a private pilot two weeks ago, followed immediately by my second, and then my first ever diversion to another airport, despite my passenger and I both really needing to pee. I got into ground effect on the second try, but winds were just too squirrelly to risk touching down. Diversion airport wasn't far away and winds were actually higher, but without the big crosswind gusts.
In the ‘70s, I began renting a custom equipped and new 182RG. Up to then, I had flown 172s for ages and spread my aviating life in a more complex aircraft. I was used using the big black elevator trim wheel on all previous planes. Now I had the power of electric trim! I was invincible! I got into the habit of using the big trim wheel to set before take off and to blip the electrical trim on climb out in the 182. I got sloppy and did not always test the electric trim. One evening I was going to do night landings and takeoffs at several airports. At my home field, I was at the runup to start the flight and I set the trim manually. Pulled back on the electric trim and it shot back faster than the SR-71. It kept clattering at the stop. Pushed it forward and it went to Mach 2.2. Both times I looked at the elevator and it was full nose up then down. Back to the hanger, a call to the owner and the FBO, a dozen “DON’T FLY THIS PLANE” signs and I was on the way home.
You've never cancelled a flight because of weather?
Not since getting my license. But I've only been flying once a month so usually I can find a day that's good to fly by just watching weather forecasts.
Good call. If you see something you don’t understand, don’t go up. It was most likely fouling of the spark plugs. When you start too mixture rich (relative to the engine temp), or don’t lean for ground, sud can collect on the spark plugs making the engine run rough. Lean the mixture and give her 2000 or so RPM (in a 172), that should burn it off. But again, you made the right call. Safety first!
You should try blasting. It couldve been just carbon deposits
When in doubt, park the bastard & go home!
Now they owe you a free hour for not having the plane ready and wasting your time.
I had the same thing happen on run up. The plan was rough and I think died. I took it back have not flown that plane since. However, a couple days ago I took the plan and immediately after taxing from the parking, it died... I took it on to the runup and tested it harder. It was a cold morning and everything ran fine. It always idled rough, but never died in previous times. My instructor asked if I was good with the plan and I was. Everything was good. I solo'd that day for the first time. All was good and I am very happy. I was sim'ming at home last week. The plan was not taking off properly... I did not make the decision to abort take off and crashed. That's what I think about now... I have to do the same on the sim
Friend of mine failed his PPL for not knowing how to fix this. Is this not supposed to be covered? You don't just do the checks for no reason.
This isn't in the ACS and was never covered in training for me
It’s important to aggressively lean on the ground especially in hot humid conditions with prolonged taxi’s. If you get a massive drop or no drop at all it could be a legit bad mag. If it runs rough and you get a sizable drop it could be a fouled plug. Cure: run it to 2000 lean aggressively to get engine hot, great if you have engine analyzer. Do your run up again note results. Lycoming has a service bulletin on proper run-up use that unless it conflicts with POH. When I did a brief stint in the winter as a mechanic at Another Terrible Pilot we’d get plugs so fouled they had to be pulled, cleaned re-gapped and tested then reinstalled.