Aborted flight/chickened out?

J

JOhnH

Touchdown! Greaser!
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Right Seater
Down here in Florida we don't get too much experience with cold weather flight.

1977 Cessna 172n w 180hp engine.
Today, outside temp was 5 centigrade/ dew 1 centigrade.
Oil temp was about 120 during run up.
Took engine to 1800 and did mag check.
Left mag dropped around 60, Rt mag dropped around 40.
Takeoff roll was normal but at around 500 ft we felt a little engine miss. A couple of seconds later it seemed to miss again. Failing to apply carb heat we called tower and requested immediate return to field. We taxied back to the hangar. We shut down for about 15 minutes and then did another run up. L mag dropped around 60, Rt mag dropped around 25. I don't think a drop of only 25 is too bad, but I am not sure and never saw it drop that low on this plane so we called it a day.

Add to this that yesterday I received a service advisory from Cessna about a problem with Slick Mags. Mandatory service at next maintenance period, but also said before flight, be sure you are familiar with detecting engine roughness and how to respond.

So we are driving to Blue Springs to watch the Manatees instead.

Any comments other than asking why I was too stupid to remember to apply carb heat at the time we felt the engine miss?
 
JOhnH said:
Any comments other than asking why I was too stupid to remember to apply carb heat at the time we felt the engine miss?
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IMO if you have an ignition problem, then you have an ignition problem. It won't generally come and go.

I'm not saying you did this, but a lot of people rush the run-up. If the drops are not normal for that aircraft or slightly suspect. Leave the motor on the mag in question for awhile. Apply some power, high speed taxi, whatever. Take the time to see if there really is a miss or problem. Troubleshoot long enough to be satisfied all is well, or concerned enough to taxi to the mechanic. Don't just take off because it meet checklist minimum specs for 2 seconds.
 
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Too little mag drop is every bit the problem as too much. What is it usually and why does your poh say it should be?
 
Sounds like you made a good decision. Now get your ignition system checked before trying to fly again.

BTW, a good engine analyzer might have helped isolate the problem. Could have been as little as one lead-fouled plug.
 
Doubt carb ice was a factor. How big of a "miss" was this? A super noticeable stumble causing loss of power or a barely detectable small period of time where it sounded like it may not have fired?
 
Alexb2000 said:
IMO if you have an ignition problem, then you have an ignition problem. It won't generally come and go.
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While I agree that once a part has failed then the problem will be constant. I've had a couple-er-three experiences that lead me to disagree with that as a guiding statement. Some components such as the coil or a wire can be intermittent prior to failing completely. Of course tracking down the problem during the intermittent failure stage can be difficult and expensive.

Mostly just sayin' that there is nothing wrong with getting things checked when ya see or feel something out of the ordinary. A good mechanic will work with you on the problem. A bad mechanic will tell you that it's your imagination.
 
jesse said:
Doubt carb ice was a factor. How big of a "miss" was this? A super noticeable stumble causing loss of power or a barely detectable small period of time where it sounded like it may not have fired?
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Yeah, I told him it wast likely today as low as the humidity is, they went and confirmed that it was not carb ice. The only thing fuel wise I think it could be is condensation formed in the carb bowl. Ignition is potentially a p-lead issue or a bad condenser, maybe a bad coil, but doesn't sound it.
 
Were you leaned out too much? Cold temps mean thicker air.

I little intermittent miss until the plane is to operating temps is nothing to worry about too much. Climb over the airport and make a few circuits until operating temps are reached. If the miss doesn't return you are good to go. :dunno:
 
Geico266 said:
Were you leaned out too much? Cold temps mean thicker air.

I little intermittent miss until the plane is to operating temps is nothing to worry about too much. Climb over the airport and make a few circuits.
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It depends on what causes the intermittent miss is the problem, because the result could lead to nothing or a lunched engine depending on the cause.
 
Geico266 said:
Were you leaned out too much? Cold temps mean thicker air.

I little intermittent miss until the plane is to operating temps is nothing to worry about too much. Climb over the airport and make a few circuits until operating temps are reached. If the miss doesn't return you are good to go. :dunno:
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A minimal RPM drop is likely due to slightly advanced timing on one mag, something I wouldn't be too worried about on a NA engine. As to checking the ignition system's health, I agree that getting the engine to normal operating temp is a good idea but the best test is at cruise power and slightly on the lean side of peak.
 
Clark1961 said:
While I agree that once a part has failed then the problem will be constant. I've had a couple-er-three experiences that lead me to disagree with that as a guiding statement. Some components such as the coil or a wire can be intermittent prior to failing completely. Of course tracking down the problem during the intermittent failure stage can be difficult and expensive.

Mostly just sayin' that there is nothing wrong with getting things checked when ya see or feel something out of the ordinary. A good mechanic will work with you on the problem. A bad mechanic will tell you that it's your imagination.
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Negatory. He will make some halfass part-replacing diagnosis (an expensive one) without having a clue of the actual source of the problem
 
I'll have to disagree. A balky mag may not start misfiring until it heats up signficantly. You can do run ups for thirty minutes and it will do fine. One sure sign of an ignition problem is that it gets better on one side or the other. This isn't foolproof (sometimes it's a fouled plug). If you have a multicylinder engine analyzer you can usually identified a bad cylinder over something like carb ice or a bad mag. Of course, troubleshooting a balky engine in the air can be a bit unnerving.
 
wabower said:
Negatory. He will make some halfass part-replacing diagnosis (an expensive one) without having a clue of the actual source of the problem
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Yup, I've had'em try that too. Had a vibration in the drive train and mechanic wanted to replace the clutch. He didn't get the job.

flyingron said:
Of course, troubleshooting a balky engine in the air can be a bit unnerving.
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You can say that again. I just loooove afterfire through the turbo (NOT!).
 
gismo said:
A minimal RPM drop is likely due to slightly advanced timing on one mag, something I wouldn't be too worried about on a NA engine. As to checking the ignition system's health, I agree that getting the engine to normal operating temp is a good idea but the best test is at cruise power and slightly on the lean side of peak.
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This is a one sided FIRST time event on the mag check. While I agree that a few RPM isn't that big of a deal and I told him on the phone that it could just be from the temp, when adding the missfires and the mag drop difference as new, the best thing IMO is to drain the bowl on the carb and do the Service Bulletin on the mags that just arrived and says "Don't fly with a rough engine until you do this" as well as check the P-lead and condenser before giving it another go.
 
Alexb2000 said:
IMO if you have an ignition problem, then you have an ignition problem. It won't generally come and go.
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We still don't know if it was an ignition problem or just moisture in the line. This was our first flight in almost 3 weeks. We rarely go that long between flights. And that brings up another thing that was out of the ordinary. The plane sat an unusually long time and it was unusually cold. The first time we turned the key, NOTHING happened. We thought the battery was dead. We waited a few seconds and tried again and it turned over slowly, but then started right up. It ran rough for a few seconds, but it smoothed out pretty quickly. It does that when it is cold, but maybe just a little more today.

Alexb2000 said:
I'm not saying you did this, but a lot of people rush the run-up. If the drops are not normal for that aircraft or slightly suspect. Leave the motor on the mag in question for awhile. Apply some power, high speed taxi, whatever. Take the time to see if there really is a miss or problem. Troubleshoot long enough to be satisfied all is well, or concerned enough to taxi to the mechanic. Don't just take off because it meet checklist minimum specs for 2 seconds.
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We lost an engine at 1,000 agl a few years ago and had to put it down on a highway, so we always do a complete pre-flight and run-up. And today, the runup was completely normal. It wasn't until about 500 or 600 feet at full power and full rich during climbout that we both felt a hiccup. It sounded like just a single engine miss. Leslie asked if I felt that and I said yes. Then it happened again during our left turnout. Just another single hiccup. And then another so we turned around. We had to do a 360 turning descent to lose enough altitude to land and in the meantime the edm700 was flashing rapid cooling temps. So we couldn't look at the cylinder displays. (I wasn't going to start pushing buttons on the EDM while trying to keep the runway in sight during a 360) But right before that, I did note that the CHT on each cylinder was (as best as I can recall) 350, 320 380 & 390. #2 always runs a little low and 3 & 4 always run a little higher. I wasn't watching EGT at the time, but if my A&P wants to know, he has the software to read the memory from the monitor.

As I said, after landing and taxing back to the hangar we did another runup and the only thing out of the ordinary was the relatively low drop on one mag.

Any one of these things and we may have continued. But on top of all we experienced and getting that service advisory yesterday, and that landing on the Highway with a dead engine still fresh in our minds (3 years later), we decided there was no way we could continue the flight. I really feel bad about that Henning. We were looking forward to this trip.

But it was a lot of fun going to Blue Springs instead and watching hundreds and hundreds of manatees playing in the warm stream and us having a picnic with some fresh sourdough rye bread, some imported cheese and a few dark beers.
 
John-

Sounds like you did a great job recognizing a problem and got it back on the ground safely. Well done, you should feel really good about how you handled it. Everything else is just conversation.

Keeping in mind that I am a lowly pilot and not an A&P, sounds more like a fuel system issue to me, but that's just another wild guess.

Let us know what it is just for our education.

That picnic sounds great, just the way to deal with a canceled trip.
 
If it only made a few 'pops' and didn't go rough, it may be that your carb may not be getting rich enough at full rich for the colder denser air. Carb heat may have cleared it...
 
Henning said:
If it only made a few 'pops' and didn't go rough, it may be that your carb may not be getting rich enough at full rich for the colder denser air. Carb heat may have cleared it...
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I am pretty sure you are right, but neither of us said anything until we got on the ground, but we were both fixated on the last time the engine started acting a little funny, and got worse and worse and worse and POW.
 
JOhnH said:
I am pretty sure you are right, but neither of us said anything until we got on the ground, but we were both fixated on the last time the engine started acting a little funny, and got worse and worse and worse and POW.
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Don't get me wrong, I'm not faulting your call, I told you to park it as well. My point is that after the SB is done and the carb got drained and no issue was found, it's not something that you want to keep spending money chasing.
 
JOhnH said:
I am pretty sure you are right, but neither of us said anything until we got on the ground, but we were both fixated on the last time the engine started acting a little funny, and got worse and worse and worse and POW.
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Where was the mixture setting for the cold air?
 
Henning said:
Don't get me wrong, I'm not faulting your call, I told you to park it as well. My point is that after the SB is done and the carb got drained and no issue was found, it's not something that you want to keep spending money chasing.
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I know what you are saying. I plan to have my A&P check it out; then have him go up with us.
 
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