Engine quit upon landing

2nd505th

2nd505th

Pre-takeoff checklist
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2nd505th
I’ve had this happen twice in a year and a half. In both situations, (although I do this more often than I should) I was coming in a little high and a little fast so I throttled all the way back, carb heat was on. Upon landing as I’m slowing down and the throttle still completely off I could tell the engine want it to die, so I throttled gently up just a little which made the engine want to die even more, then I try to slightly aggressively pump the throttle and by that point my engine just quit. In both cases my aircraft died in the middle of the runway. I can think of things that I could try to do better which is to have a little RPM upon landing. Perhaps turn off the carb heat just before landing. Come in a little lower with less speed. So what I’m trying to figure out is did my engine become starved of fuel, had too much fuel is my technique not good enough that it would cause this or is there something possibly not quite right with my fuel system? In both cases after landing I was initially very gentle with the throttle, not jamming it.
 
what aircraft/engine?
 
Might just be something as simple as too low set idle RPM. I have this same problem, but it's intentional. My engine runs really well, so I have the throttle set really low without carb heat. Carb heat lowers it more, and sometimes it dies with it on.
 
Could be be the carb needs adjustment. Also check and make sure your intake isn't leaking.
 
After run-up, do you turn on carb heat before pulling the throttle back to check idle with carb heat on? Dumb question for internet diagnosis. Just checking to see if this only happens after a prolonged period airborne (hot, in motion).
 
I'm with the carb/idle adjustments guys. But it sure sounds to me like something to be corrected before you continue flying the thing.
 
How long did you have the carb heat on before landing?

Remember the engine is putting out very little heat at idle power. So if you had some ice it might not have sufficient heat to melt the ice quickly. Try adding carb heat earlier, say before turning base, or even while still on downwind.

I had this problem once, Piper Warrior, O-320, on a very humid day. A little more heat and she was fine!

One clue was how easily it started back up. Hot engine from flying melted any ice almost instantly. -Skip
 
Another for the idle camp. How hard was it to start back up?
 
455 Bravo Uniform said:
After run-up, do you turn on carb heat before pulling the throttle back to check idle with carb heat on? Dumb question for internet diagnosis. Just checking to see if this only happens after a prolonged period airborne (hot, in motion).
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Yes I do that procedure every run up.
 
Racerx said:
Another for the idle camp. How hard was it to start back up?
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They towed me to the ramp and got a jump. It started in a few seconds. But the jump gave me way more crank speed power than I ever get during a manual start.
 
Skip Miller said:
How long did you have the carb heat on before landing?

Remember the engine is putting out very little heat at idle power. So if you had some ice it might not have sufficient heat to melt the ice quickly. Try adding carb heat earlier, say before turning base, or even while still on downwind.

I had this problem once, Piper Warrior, O-320, on a very humid day. A little more heat and she was fine!

One clue was how easily it started back up. Hot engine from flying melted any ice almost instantly. -Skip
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I think I turned on the carb heat when I was downwind abeam the numbers.
 
Make sure you let us know what it was.
 
For what it’s worth my engine idles at about 500 RPM and goes down to about 450 with carb heat. Is that too low for a Lycoming O-235 ?
 
How much gas was in the tank feeding the engine and how aggressive was the stop? My bonanza will suck air if I slow down too quickly below about 10 gallons in the tank.
 
2nd505th said:
For what it’s worth my engine idles at about 500 RPM and goes down to about 450 with carb heat. Is that too low for a Lycoming O-235 ?
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That sounds pretty low to me. How do you know? The Tach in the plane? Maybe it isn’t accurate. Add me to the list of those saying, take it to an A&P. And don’t fly it until you do. It could be a symptom of a bigger problem.
 
If it's an injected continental, I suspect the idle mixture is off.
 
Initial Fix said:
How much gas was in the tank feeding the engine and how aggressive was the stop? My bonanza will suck air if I slow down too quickly below about 10 gallons in the tank.
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It was a normal slow rolling stop I think I had about 7 gallons left
 
luvflyin said:
That sounds pretty low to me. How do you know? The Tach in the plane? Maybe it isn’t accurate. Add me to the list of those saying, take it to an A&P. And don’t fly it until you do. It could be a symptom of a bigger problem.
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Yes from the tach in the plane.
 
2nd505th said:
For what it’s worth my engine idles at about 500 RPM and goes down to about 450 with carb heat. Is that too low for a Lycoming O-235 ?
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Too low. The service manual for the Cessna 152, which uses the O-235, calls for 600 +/- 25 RPM.

The idle mixture should be checked as well and set for a 25 RPM rise when the mixture is slowly pulled to idle cutoff.

The Lycoming uses a tiny carb heat muff and it doesn't deliver much heat. If you're on a long final at idle, that exhaust system gets cold and if there's enough humidity you can get ice that will kill the engine. Most airframe manufacturers recommend powering up the engine every 1000 feet or so to warm the exhaust and get more heat into that carb, and I don't mean for five seconds either. It takes some power for some time to get things warm again.

There's a common myth that Lycomings are carb ice-proof. They're not; they resist it better than some other engines but they can still get it. I've seen it plenty of times. The O-235 is a cool-running engine and that sump, where the carb is mounted, doesn't get all that warm.

So get the idle speed and mixture adjusted and see that the carb heat system is working properly. You might even have a misrigged carb heat control that isn't opening the heat all the way. As write-stuff said, get it fixed before it hurts you.

Is this a homebuilt with a homemade carb heat system?
 
Sounds like a low idle problem. Yes, that should be adjusted.

But also keep in mind that mixture is a real thing. An engine dying because you fed it gas indicates a low air component, which is probably coming because of the low RPMs. That will be even lower if the carb heat is still on and you're at any altitude. I can make my engine die at low idle too if I try hard enough by getting the mixture wrong.

You're full rich with low air, adding more gas into the mix. As counter intuitive as it sounds, try turning the carb heat off and leaning for ground operations.
 
bflynn said:
Sounds like a low idle problem. Yes, that should be adjusted.

But also keep in mind that mixture is a real thing. An engine dying because you fed it gas indicates a low air component, which is probably coming because of the low RPMs. That will be even lower if the carb heat is still on and you're at any altitude. I can make my engine die at low idle too if I try hard enough by getting the mixture wrong.

You're full rich with low air, adding more gas into the mix. As counter intuitive as it sounds, try turning the carb heat off and leaning for ground operations.
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Just open the throttle occasionally and clear that engine.

We had a Citabria with a Lyc O-320-A2B that would load up on final no matter what we did with it. Rebuilt the carb, mags, everything, and it would still do it. There were a few Lycoming models like that and it apparently had to do with the manifolding geometry. Idle fuel would condense on the manifold walls and puddle there, and get sucked in and overwhelm the cylinders when you opened the throttle. One could see black smoke sometimes in a landing overshoot. We had to just clear the engine more frequently or suffer that hesitation or quitting. Carb heat made it better, not worse, by limiting the condensation of the fuel in the manifold.

It was also the worst Lyc we had for making carb ice. It was as bad as an O-200 for that. Again, turning carb heat off on final was asking for trouble if one had to abort.
 
Many bush pilots here that fly into very short landing strips in the Sierra Madre mountains of Mexico deliberately set their idle RPM very low to permit steeper approaches and shorter landings. The throttle is used for idle RPM desired.
 
Snowmass said:
Many bush pilots here that fly into very short landing strips in the Sierra Madre mountains of Mexico deliberately set their idle RPM very low to permit steeper approaches and shorter landings. The throttle is used for idle RPM desired.
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Some floatplane operators do that too. It makes docking and maneuvering easier. Switching one mag off and pulling carb heat reduces the idle further.
 
Carb heat + low RPM + Pumping throttle = suspected flooding of engine.
 
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