Fire Went Out?

[Hawgsforever]

Was practicing some short/soft field stop and go patterns at a remote but very long and well maintained dirt strip yesterday getting tuned up for moose camp. Winds were very gusty...probably 15 gust 25 down the runway (maybe 2-3 knot crosswind). I was fighting to be on speed and on glidepath down final which required constant control and throttle inputs. Went to idle at 2-3 feet above the ground and the engine actually quit at touchdown. Certainly got my attention!! Thankfully a good approach and easy roll out. Engine started right up and could not duplicate on the ground. Flying buddy I was with stated he had the same thing happen a few times in his cub under the same conditions (gusty, lots of throttle adjustments, constant changing load on prop). I have the O-540B4B5 carbureted Lycoming and have never had this happen before...have had occasional backfires on going to idle, but never quit before.

Anybody else ever have this happen?

My airplane is 2 flights after a thorough annual and ground mag checks and all other flight manual checks are nominal.

Wondering if this was just conditions plus poor throttle technique or something more seriously wrong with fuel delivery or spark.

Like to hear if anybody has ever had this happen or thoughts on maintenance items to look at.

Thanks.

[Andy Young]

First thing I thought of is if you pushed the throttle forward abruptly at low RPM, you could have due to a momentary over-lean condtion, but this doesn’t fit your description of the event. Is it possible you had built up a bit of carb ice? Did you have carb heat on? Is it adjusted/connected properly? Does the carb heat behave properly on a run up?

[Hawgsforever]

Andy,

I was jockeying the throttle so a temporary lean is possible. Carb heat works great on ground checks and was not on at the time. Temperature was 55 F., humidity 85% or so, and had not flown in visible moisture though I know at that humidity and low power settings, ice is a potential without visible moisture.

[flyusn99]

Hawgs,
My bet would be on carb ice. Based on the conditions you describe that's prime icing territory. What with the amount of moisture you guys recently have been having in the interior it makes sense.
Recently had a JPI-830 installed and was somewhat surprised at the outside conditions that lead to carb temps of 30-33degrees.
The only time I've ever actually had it was flying across Montana on a 60 degree day, around 70% humidity without a cloud in the sky for hundreds of miles. Started running rough at 75% and carb heat solved it in just a couple seconds... Just my 2 cents worth...


James

[maules.com]

I'd guess carb ice too. I have had carb ice on the B4B5 engine in cruise, and in landing and that temp and humidity is perfect for it to develop.
The best carb ice detector is the one that has a 'magic eye' probe in carb throat that actually sees the ice and flashes a red light on the panel.

[UP-M5]

i would concur on slight carb ice. i have been doing a bit of hunting season flying in the talkeetna mountains lately and have had to be very aware of carb ice on my -J1A5D (as is always the case). especially getting low and slow when lots of throttle inputs don't let you notice the slight reduction in manifold pressure that you would see in cruise with carb ice building.
in the beaver we set a partial carb heat at all times to maintain a carb temp above freezing. so i have adopted a similar procedure in the maule when slow and close to terrain when i don't have time to notice it happening. and always clear the carb with full heat on final. i usually go back to carb heat off for short final and touch down though- in case i need to use all available power.

also a good thing to make sure service bulletin 16 (IIRC) is up to date. it talks about the rubber seal inside the carb heat box valve coming apart and plugging up the venturi.

safe hunting season to all!