Recently, I was climbing out in a Cherokee 160, P-28 I have been renting when, at about 300' AGL there was a sudden, marked decrease in power. It sounded as if someone had pulled the throttle back about 25% and the engine started running roughly. I thought it was going to die compelely. I immediately checked the carb heat, mixture, and fuel pump while turning back to the runway while I still had some power. After about 15-30 seconds the engine regained full power, but still did not sound right. I landed safely, returned the airplane to the hanger and contacted the owner. Let me say, I did a complete pre-flight and run up, which included checking the fuel for water at all 3 drains. Magnetos and carb heat were functioning properly before take-off. A mechanic checked the plane and said the lower plugs were fouled. I was told he corrected the problem and tested the engine and that the plane is now "good to go." Honestly, I am not excited about getting back in that plane. Does the mechanics explanation sound reasonable? What precautions should I take or what questions should I ask before trusting my life to that same plane?
Decrease in power on take-off
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Dan Thomas
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Dan Thomas
Ignition first, since it's the biggest source of trouble. Magnetos aren't hard to open up and check if one knows how. A dead mag will cause some drop, but a 25% power drop is pretty big.
Then, the Piper mufflers sometimes had issues with internal baffles breaking loose and blocking the exhaust outlet. They should have had that figured out by the 160-hp versions.
Or a valve was sticking.
Dan
Then, the Piper mufflers sometimes had issues with internal baffles breaking loose and blocking the exhaust outlet. They should have had that figured out by the 160-hp versions.
Or a valve was sticking.
Dan
COFlyBoy
Line Up and Wait
I'd suggest a full power runup. I had some mag issues that only showed up under full power. During a normal runup the cylinder pressures weren't high enough to show the weak mag.
gismo
Touchdown! Greaser!
A single weak mag shouldn't cause anywhere near a 25% loss of power, try switching one mag off during a full power climb and I think you'll find the power decrease to be barely noticeable. Now if one plug was fouled and the mag powering the other one in the same cylinder quit, it would get your attention right away. It's also possible that crossfiring due to arcing inside one mag would make a big drop in power (and probably shake the bejezees out of the engine) so it's still worth looking inside the magnetos.
Other possibilities are something blocking the intake, a stuck valve or two fouled plugs in the same cylinder at the same time but it's rather unlikely that fouled plugs would unfoul by themselves when there was no fire in the cylinder so I'd place my money on a temporarily stuck valve.
PilotAlan
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Did you APPLY carb heat?
It seems to me that carb ice could significantly richen the mixture and foul plugs.
This seems like straight up carb icing to me.
murphey
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Before declaring a reason, some additional information would be useful, such as field elevation, temp, humidity, etc. Altho the engine went ??? at 300 ft, what altitude did the OP do the return to the runway? This one worries me even more.
gismo
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Given that full power was restored not to mention that said return was rather successful, I don't see much point in worrying about that.
Graueradler
Pattern Altitude
I have had mystery power reductions on a Cherokee twice. Once it was a mud dauber nest that had that had been built on the heat muff side of the carb heat valve but came loose and migrated to the normal induction side during the carb heat check on run-up. Run up power air flow was not enough to suck it into the carb throat but take off power was. It was not consistent on whether it would suck into the carb or not. Run-up at 2000 RPM was always good but full power might or might not move it to the carb throat. The other event was from muffler internal pieces intermittently blocking the muffler outlet in spit of the bail that is supposed to prevent this. Pulling off the flexible tube between the carb and induction filter will tell you if there is a mud dauber nest. Looking up the tail pipe with a flash light might show you a piece of broken muffler internals (and might not)
Thank you for all the replies. A lot to think about. I got the mechanics report second hand and now that you have mentioned it there was something said about some malfunction in one set of mags.
I am not a highly experienced pilot. When I heard the power drop and felt the engine laboring my first thought was that I had something set wrong. I wish I had looked at the RPM's, but did not. I glanced at the airspeed indicator just to insure I wasn't about to stall. It was at 80kts. I usually climb out at 100 kts. I know now I should have immediately applied a little carb heat. I did not. I just kept pushing hard on the throttle... like that was going to help. The air was humid, field elevation was 650', and temp was around 60F. Would carb icing have gotten better on its own w/o carb heat?
As far as the low altitude return to the field goes, I still had power and though the engine was laboring and sounded like it might shut down, the plane was still climbing and I was maintaining 80kts. I simply turned cross-wind, climbed above pattern altitude (just in case) and did a normal left pattern back to the runway I departed from. Nice, full-flaps landing, no harm done... Thank God.
I am not a highly experienced pilot. When I heard the power drop and felt the engine laboring my first thought was that I had something set wrong. I wish I had looked at the RPM's, but did not. I glanced at the airspeed indicator just to insure I wasn't about to stall. It was at 80kts. I usually climb out at 100 kts. I know now I should have immediately applied a little carb heat. I did not. I just kept pushing hard on the throttle... like that was going to help. The air was humid, field elevation was 650', and temp was around 60F. Would carb icing have gotten better on its own w/o carb heat?
As far as the low altitude return to the field goes, I still had power and though the engine was laboring and sounded like it might shut down, the plane was still climbing and I was maintaining 80kts. I simply turned cross-wind, climbed above pattern altitude (just in case) and did a normal left pattern back to the runway I departed from. Nice, full-flaps landing, no harm done... Thank God.
Capt. Geoffrey Thorpe
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Could have been the problem then.
Yea. you coulda pulled the carb heat. Fiddled with tank selectors. Tried shutting off mags (one at a time :wink2
. But in the end, the important thing to do is keep the airplane in the air. Sounds like you did just fine. Sounds like you did the right thing to me.
Skip Miller
Final Approach
In that situation, never go partial carb heat. Full on! Get that ice out of there NOW. ...but it may not have been ice. Regarding pushing the throttle beyond the stops, that is a natural reaction, but as you know, it doesn't help much!
Possible, but not likely. What is even more unlikely is that the engine would give you full power on takeoff and then ice up at wide open throttle. This is an O-320, right? Was this the first flight of the day, or was the engine thoroughly warmed up from prior flights? If the latter, I would all but discount icing as the problem at wide open throttle. I'll look for and post a carb ice probability chart, see next post (if I can find it!)
I hope I am wrong on this, but it could be a camshaft problem. We had that happen on one of our club's Arrows - different engine, yes. Intermittently it wouldn't make full power on takeoff. Somehow we had lunched the camshaft.
-Skip
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Skip Miller
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JeffDG
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Well...what tweaked my brain was the 25% loss of power (I know it was a guestimate).
But if you've got a completely fouled plug in one cylinder, and you lose the other mag...that one cylinder might stop producing power entirely, and in a 4-cyl engine that's a 25% drop!
If that plug started firing again, that would account for the recovery of power.
Richard
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Ack...city life
My most recent plane was born as a PA-128-160 on May 1962.
Jeff Oslick
Final Approach
What you experienced was almost certainly carb ice. I've experienced it in a PA-28-160 in identical conditions to what you found. Same temp, humidity, sea level, and 300' AGL on departure. You must apply full heat, and leave it there. If you only go partial heat, or worse, turn it off again, it will come back. Leave the mixture full rich.
Jeff
Jeff
eMKay
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At full throttle? Not likely.
gismo
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Actually if one of four cylinders goes dead from lack of spark you're left with just a little more than 50% power. A significant amount of power is consumed pumping air through that dead cylinder. Still given that there was no means of accurately assessing the remaining power this could indeed have been a completely dead cylinder.
Graueradler
Pattern Altitude
Maybe but I fly behind an O-320 in a Cherokee and have never had a need for carb heat in nearly 1000 hours. I fly from a 400' field in Arkansas - also high humidity in the summer. (dew points in the 60s and 70s). I doubt that it was carb ice.
Jeff Oslick
Final Approach
Once you're in the 60-70's dew points and 80-90 ambient temps, you're outside the range where climb/cruise power are likely to cause carb ice.
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Bob Gardner
Aerodynamics 101: The wings stalls at the critical angle of attack, not at a specific airspeed. You feel the onset of a stall in your butt and in the reaction of the flight controls. My students all had to do pattern work with the airspeed indicator covered...might be something your instructor could experiment with.
Bob Gardner
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You clearly have never flown an O-200 or O-300 (or if you have, not extensively), both of which I have had ice up on me at full throttle takeoff.
Witmo
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Tim
Lycoming engines are much less prone to carb icing. Sticky valve: loss of power and runs very rough, could be precursor to stuck valve--it
doesn't get better over time. Magneto timing issue could also account for roughness and power loss; check that both mags are securely fastened.
doesn't get better over time. Magneto timing issue could also account for roughness and power loss; check that both mags are securely fastened.
gismo
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And at full throttle, under the right conditions. It's just a lot less likely with the throttle open. It's also possible for ice to form prior to takeoff in a way that doesn't affect the engine much until the throttle is opened.
Skylane81E
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denverpilot
Tied Down
For sure. BTDT too.
My go-to assumption has become that my O-470 is making ice as the first thing wrong when power isn't what it's supposed to be.
flyingcheesehead
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For sure. BTDT too.
Weird... I am a chronic carb-heat-forgetter, but I have never gotten any carb ice in the 182, I don't think. So I don't even bother with carb heat most of the time.
We did have the carb temp option put in with the JPI install a couple summers ago, and that is VERY interesting - Carb temp in cruise is *just* above freezing!
denverpilot
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flyingcheesehead
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Skylane81E
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Now if you remember that the temp can drop even more in the induction tubes as the fuel vaporizes...
There is such a thing as fuel vaporization ice.
My plane iced so bad at WOT about a month ago that she quit climbing at just 5k feet (I let it go for only a min or two after first signs as an experiment) and man did she shake when I pulled the carb heat on
Should note that I was climbing through a "cloud" at the time. Cloud is in quotes because the vis at that layer was probably 7 miles but there was visible moisture.