Had a SCARE during a flight today!

[netsurfr]

So went up for an IFR phase check today and during the climb at 5500 shortly after takeoff the engine momentarily hesitated (as best as I can describe it) and lost a bit of power during the climb. Conditions were cold (28F on the ground) but we were not and had not flown through moisture. Full throttle, prop, and mixture with fuel pump off & carb heat off. Engine indicators all in the green. Carb temp was about 22F during the climb and OAT was about 36F. I turned on the fuel pump and applied carb heat. The engine felt like it rumbled a little and after a bit carb heat and fuel pump off and no other problems for the duration of the 2.5 hour training flight. One thing I noticed in the JPI is that CHT of Cyl 1 was 275F where the rest were in the low to mid 300's. BTW - Both tanks were full w/ fresh gas and plane is in a heated hangar so no condensation/moisture in the fuel sumps.

JPI data showed the slight and momentary drop in RPM and EGTs but nothing else I can see (except Cyl 1 CHT being colder and dropping temp more than the rest) out of the ordinary.

Here's a link to the JPI data. If you add RPM data on the right to the EGT chart and go to 22 minutes into the flight you'll see the slight RPM and EGT drop.

https://www.savvyanalysis.com/flight...0-fdc212472c97

Here's a very short video clip. At 6 seconds you can sort of hear the change in engine noise & when you see me turn on the fuel pump and then carb heat you can hear some slight roughness.

http://youtu.be/GThj7Chd2qs

So what could cause a "hiccup" like that? If this could have been carb ice I'm surprised because it was cold (36F) and DP spread on the ground about 15F (50% relative humidity)plus no clouds/moisture. Carb Temp was 22F but with those conditions I would not expect carb icing so wondering what else it could be and what to do next????

So now I'm freaked out about this!!!

 

[Brad Z]

28F on the ground and 36F aloft? Didn't click on the links, but my guess is some frozen water in the tanks thawed and passed through the carb.

Water won't sump out below freezing.

 

[MichiPilot]

I couldn't really hear anything on the video

 

[Code90]

Would think small amt of water passing through too. Had similar episode yrs ago during my night cross country to get my PPL. Had instructor in plane at the time. Asked him "Did you hear that?" "Yeah". "Hope I don't hear it again".
Never did have any more issues, but drove home the issue of limited options on a night flight.

 

[netsurfr]

CFI w/ me said the same thing (some water in fuel or something) but the plane is stored in a heated hangar kept at 45F so rain and condensation should not be a problem based on my understanding. I tested the fuel as part of the pre-flight as well and no water so still curious.

Would think small amt of water passing through too. Had similar episode yrs ago during my night cross country to get my PPL. Had instructor in plane at the time. Asked him "Did you hear that?" "Yeah". "Hope I don't hear it again".
Never did have any more issues, but drove home the issue of limited options on a night flight.

 

[netsurfr]

Sorry yes it's hard to hear because it wasn't a major loss of RPM but if you turn up the volume and start listening about 5/6 seconds into the video you'll notice the change in sound. The engine data also shows the drop in rpm but it was quick and about 100 rpm difference so hard to see given that I had the JPI set to record every 6 seconds.

I couldn't really hear anything on the video

 

[Flocker]

shortly after takeoff the engine momentarily hesitated (as best as I can describe it) and lost a bit of power during the climb.

Exact same thing happened to me yesterday. I assumed it was water as well. Much different feel compared to a carbon deposit burning off. I'll never forget the sound of that either...

 

[Brad Z]

CFI w/ me said the same thing (some water in fuel or something) but the plane is stored in a heated hangar kept at 45F so rain and condensation should not be a problem based on my understanding. I tested the fuel as part of the pre-flight as well and no water so still curious.

Did you check for water while it was inside the hangar? Doesn't really matter, actually...here's why.

Take a cold soda out of the fridge and take it outside on a warm moist day and condensation will form on the outside of the can.

Conversely, gather a couple folks inside a tent on a cold evening. Condensation will form on the inside of the tent.

Like the second example, the the moisture suspended in the warmer air inside the tank condensed to the interior surface of the tank, when the wing was exposed to the colder air. It probably formed a minute amount of prozen droplets on the inside of the tank, as the temperature with the wing skins dropped below freezing.

In flight, that ice melted inside the tanks as you climbed up into warmer air. Most of the water passed without you noticing, but likely a few drops passed together (maybe you hit a bump just right). That's enough for a slight miss like you experienced. As you can tell, not a big deal (unless you're not expecting it!).

 

[tiger]

Anyone know how much water is required to cause a noticeable stumble in an motor (that I think is sucking maybe a third to a half an ounce per second?)

 

[James331]

You can get water in the tanks even at temps like 45f, you can also have straight water in the tank and not have it get to the sump, rocking the wings can help.... a little

My only thought was why everyone was eyes on that JPI and why you still were wearing that hood when the engine hiccuped?

Looked MVFR, and looked like you were still climbing up to the soup.

IMC isn't a place to be in a single engine piston that so much as coughed funny,

IMO, if something doesn't feel right, loose that silly hood, turn to the nearest field, trouble shoot enroute. Land and figure it out down there.

 

[netsurfr]

Good theory on that 2nd point. The plane is kept in a heated hangar maintained at 45F so as to keep it warm enough but not too warm and I never fill my tanks to the top so wonder if that's what happened.

My only concern is that looking at the JPI data it does appear that #1 Cylinder CHT & EGTs both dropped much more than the rest?

Did you check for water while it was inside the hangar? Doesn't really matter, actually...here's why.

Take a cold soda out of the fridge and take it outside on a warm moist day and condensation will form on the outside of the can.

Conversely, gather a couple folks inside a tent on a cold evening. Condensation will form on the inside of the tent.

Like the second example, the the moisture suspended in the warmer air inside the tank condensed to the interior surface of the tank, when the wing was exposed to the colder air. It probably formed a minute amount of prozen droplets on the inside of the tank, as the temperature with the wing skins dropped below freezing.

In flight, that ice melted inside the tanks as you climbed up into warmer air. Most of the water passed without you noticing, but likely a few drops passed together (maybe you hit a bump just right). That's enough for a slight miss like you experienced. As you can tell, not a big deal (unless you're not expecting it!).

 

[netsurfr]

Actually ceilings were at 12K and VFR so we never got even close to the soup/imc it just looks that way because the camera overexposes the sky so in video it always looks like I'm in the soup! I'm so used to that hood (very restricting) that it didn't even phase me when I felt the hesitation plus I believe we were under auto pilot on assigned heading & climb rate. My initial reaction and question to the CFI after turning fuel pump and carb heat on was to let Center know we're turning back to the airport (3 miles behind) but he was not as alarmed as I was!

Good learning point though.

You can get water in the tanks even at temps like 45f, you can also have straight water in the tank and not have it get to the sump, rocking the wings can help.... a little

My only thought was why everyone was eyes on that JPI and why you still were wearing that hood when the engine hiccuped?

Looked MVFR, and looked like you were still climbing up to the soup.

IMC isn't a place to be in a single engine piston that so much as coughed funny,

IMO, if something doesn't feel right, loose that silly hood, turn to the nearest field, trouble shoot enroute. Land and figure it out down there.

 

[Brad Z]

Good theory on that 2nd point. The plane is kept in a heated hangar maintained at 45F so as to keep it warm enough but not too warm and I never fill my tanks to the top so wonder if that's what happened.

My only concern is that looking at the JPI data it does appear that #1 Cylinder CHT & EGTs both dropped much more than the rest?

OK, I looked at your data. Nothing particularly significant happened. A momentary drop of EGT of 75° followed by a 3° drop in CHT.

I'm guessing Cylinder #1 is the front cylinder getting the most exposed air. Water in the fuel is not going to atomize the fuel will in the carb. If enough water passed to momentarily prevent combustion (as evidenced in the video) it is also going to drop the EGT momentarily. As CHT are slower to respond to such changes, the small drop in the #1 shows that the #1 cylinder cools faster than the others, which makes sense since it has more airflow.

 

[James331]

Actually ceilings were at 12K and VFR so we never got even close to the soup/imc it just looks that way because the camera overexposes the sky so in video it always looks like I'm in the soup! I'm so used to that hood (very restricting) that it didn't even phase me when I felt the hesitation plus I believe we were under auto pilot on assigned heading & climb rate. My initial reaction and question to the CFI after turning fuel pump and carb heat on was to let Center know we're turning back to the airport (3 miles behind) but he was not as alarmed as I was!

Good learning point though.

Were you climbing on AP on VS or IAS?

After two engine failures, I've become very black and white on these things.

I think your initial reaction to turn back was the wise move, imagine how silly you would have felt if things went the other way.

 

[netsurfr]

Thanks. That's what the CFI (who's also a charter pilot) thought (some water going through) and that's what my A&P suspects after I described the incident today.

Yes #1 is the cylinder that gets the best/most air so that would explain why CHTs are lower in it and your explanation makes sense if water was the culprit. I'm a new owner so learning a ton about all this stuff in the last 4 months!

Now I still don't understand how water could have gotten in there in the first place. I keep the plane in a heated (45F) hangar so not outside and although I don't top off the tanks after every flight I wouldn't think any water vapor in the tank would freeze the little bit of time the plane sits outside of the hangar before a flight and I test the drains and never have found any sediments or water in the tanks?

OK, I looked at your data. Nothing particularly significant happened. A momentary drop of EGT of 75° followed by a 3° drop in CHT.

I'm guessing Cylinder #1 is the front cylinder getting the most exposed air. Water in the fuel is not going to atomize the fuel will in the carb. If enough water passed to momentarily prevent combustion (as evidenced in the video) it is also going to drop the EGT momentarily. As CHT are slower to respond to such changes, the small drop in the #1 shows that the #1 cylinder cools faster than the others, which makes sense since it has more airflow.

 

[netsurfr]

Yes the Autopilot was engaged and we were climbing through 4400 for 6000. Autopilot was on attitude mode so keeping a climb rate of about 600 FPM. IAS was about 110knots and ground speed about 120knots.

I agree w/ you. I think the safest decision would have been to simply turn back and evaluate while staying within gliding distance of the airport should the situation gotten worse. That's what my instinct told me to do but then again I delegated the decision to the CFI but looking back I should have done what I thought was smart.

Were you climbing on AP on VS or IAS?

After two engine failures, I've become very black and white on these things.

I think your initial reaction to turn back was the wise move, imagine how silly you would have felt if things went the other way.

 

[James331]

Yes the Autopilot was engaged and we were climbing through 4400 for 6000. Autopilot was on attitude mode so keeping a climb rate of about 600 FPM. IAS was about 110knots and ground speed about 120knots.

I agree w/ you. I think the safest decision would have been to simply turn back and evaluate while staying within gliding distance of the airport should the situation gotten worse. That's what my instinct told me to do but then again I delegated the decision to the CFI but looking back I should have done what I thought was smart.

If you selected a climb at 600FPM, not and at a specific airspeed (IAS mode if you have it), loosing enough power you would have climbed right into a stall.

If you have IAS mode on your autopilot, climb in IAS mode and descend in VS mode, I find that works well, and is the safest option.

When things go sideways kill the automation, fly the plane, reinstate the automation as workload dictates, looking at a instrument during a possible impending engine failure while in VS climb mode, there have been deaths following the same path.

Sounds like you had a good reaction to the situation (unlike your CFI), enjoy your instrument training and always err on the side of saving your skin, tin, than ticket, in that order.

 

[netsurfr]

Good point. My AP does not have an IAS mode and although I've read about AP trying to keep a climb right to stall it never crossed my mind but another good thing to learn from this and incorporate as my standard reaction (kill the AP) should something like this happen again.

Looking back I feel bad that I didn't just follow my instinct to at least turn back towards the airport but the CFIs reaction made me feel I was blowing the momentary hiccup out of proportion and since engine data all looked fine I trusted his decision.

If you selected a climb at 600FPM, not and at a specific airspeed (IAS mode if you have it), loosing enough power you would have climbed right into a stall.

When things go sideways kill the automation, fly the plane, reinstate the automation as workload dictates, looking at a instrument during a possible impending engine failure while in VS climb mode, there have been deaths following the same path.

Sounds like you had a good reaction to the situation (unlike your CFI), enjoy your instrument training and always err on the side of saving your skin, tin, than ticket, in that order.

 

[timwinters]

Conversely, gather a couple folks inside a tent on a cold evening. Condensation will form on the inside of the tent.

As Click and Clack would say...booooooooooooooooogus

People in a tent add both heat and moisture to the air. A person's exhaled breath is laden with moisture that is picked up in the lungs.

By contrast, a heated hangar dries out the air instead of humidifying it...unless, of course, it has a humidifier or some other activity that adds humidity. Even then, as leaky as most hangars are, it takes something significant...like a wash bay...to make a significant difference in the winter.

20dF air heated to 40dF does not gain moisture without a significant external injection of moisture and thus, when cooled back down to 20dF, it doesn't condensate.

 

[tiger]

This is along the lines of what I was thinking (which is why I asked how much water would be required to cause stumbling).

The mass of air remaining in mostly full Dakota tanks, even at 45 degrees F and 100% relative humidity, can't contain more than a gram or two of water. If that air has been taken from outside at 20-something degrees F, the RH is much lower than 100%, and the volume of water correspondingly lower.

Unless it's somehow accumulating over multiple fill cycles, I don't think condensation from the air in the tanks is a plausible source of sufficient water.

I would be prepared to find out that my math and hazy physics are wrong, however.

 

[netsurfr]

Got a chance to go up today and all was fine! Finally had a chance to run a few of the savvyanalysis test flights so did the In Flight Mag Check while LOP and all looked and felt great so no issues with my ignition system (mags, plugs, wires). Also did the GAMI spread test and Induction Leaks test and no issues there either. Actually the results of all the tests (including GAMI) were MUCH better than anticipated so glad to see I can run well LOP even w/ a carbureted engine. I did not even run partial carb heat so that would help even more. So given that today's test flights looked/felt great I'm guessing/wondering if the hesitation I experienced the other day during climb was due to fuel contamination or perhaps carb icing (although conditions and phase of flight would not make expect carb icing) so still a bit of a mystery!!

BTW - I leaned the mixture much more on the ground to avoid any chance at plug fouling.

 

[Hank S]

I generally pull the mixture 1/2 - 2/3 towards cutoff on the ground. Parked in the grass this summer, needed more power to get up on the asphalt, the engine stumbled badly until I pushed the mixture forward some. That's a properly leaned taxi position, it will keep you from taking off if you forget to push the mixture in first.

 

[jesse]

Meh, no big deal, and no reason to beat yourself up over how it was handled.

 

[netsurfr]

That's how far I leaned it today on the advice of others. I had read and tried this much leaning in the past but the CFI sitting next to me said I was leaning WAY too much so I went back to being conservative w/ the ground leaning but not anymore! I do like the fact that when you lean this much you don't have to worry about fouling and more importantly should I forget to go full rich before takeoff run the engine won't let me go!

I generally pull the mixture 1/2 - 2/3 towards cutoff on the ground. Parked in the grass this summer, needed more power to get up on the asphalt, the engine stumbled badly until I pushed the mixture forward some. That's a properly leaned taxi position, it will keep you from taking off if you forget to push the mixture in first.

 

[netsurfr]

Thanks. In the grand scheme of things I'm still a relatively new pilot w/ 210 hours and just having bought my first plane so this hesitation on takeoff was my first "scare". I'm sure there will be others and hopefully they all end up well!

Meh, no big deal, and no reason to beat yourself up over how it was handled.

 

[dlsmith]

If you selected a climb at 600FPM, not and at a specific airspeed (IAS mode if you have it), loosing enough power you would have climbed right into a stall.

If you have IAS mode on your autopilot, climb in IAS mode and descend in VS mode, I find that works well, and is the safest option.

When things go sideways kill the automation, fly the plane, reinstate the automation as workload dictates, looking at a instrument during a possible impending engine failure while in VS climb mode, there have been deaths following the same path.

Sounds like you had a good reaction to the situation (unlike your CFI), enjoy your instrument training and always err on the side of saving your skin, tin, than ticket, in that order.

A big +1 for everything here