912S shutdown on Final

[kmach]

Has anyone had problems with fuel loading up and shutting down with a 912S ? I was on a long final with low rpm and just before touchdown it died, landed smooth rolled out and restarted without difficulty . I am a little concerned, any comments or is the key to clear the engine at regular intervals ?:confused:

[Agfoxflyer]

Five or so years ago there was an incident where a Model 4 (I think) was on a long decent with just a few gallons of fuel in the tanks. All the fuel migrated to the front of the tank and the fuel intake unported. The plane went down on a road with substantial damage. Could this be the situation? If I remember correctly the fuel on the plane was close to minimums. My brother use to have a C140 and it unported on take off twice with half tank.

[Dorsal]

out of curiosity what constitutes low RPM?

[Slyfox]

do you have a low fuel warn. If not, get it.

[napierm]

Seriously though, besides fuel level and/or pressure, could your idle mixture be set too rich? The prop windmilling with the throttles closed will make the idle circuit to run a little richer than it would on the ground. That can cause the plugs to load up.

Just a thought.

[kmach]

do you have a low fuel warn. If not, get it.
I was test flying a plane that was for sale and yes it has a low fuel warning light. we checked tanks before flight and had over half tanks, low ceiling so we were doing stop and goes , I was pretty high on a short base and on final had the throttle pulled right back. l was concetrateing on the slip characteristics and not the rpm, maybe a little too much , so I don't really know what the rpm was , I think the carb idle stops were set a little low on this plane. and I slipped in, just at flare -to touchdown engine quit, rolled out and stopped then it fired right back up with no real difficulty. I am thinking it pooled up with fuel as I did not clear the engine or move it off idle for some time,and as well we had the aux fuel pump on.:cool:

[Dorsal]

Unless you over pressure the fuel system the carb floats prevent excess fuel. I have only 6-7 hours on my 7 but I have noticed as I set the throttle on short final to 1800-200 rpm that by the time I'm rolling off the runway it is closer to 1400-1500. I was actually warned by CDE2fly to watch for killing the engine on final, not sure if that was just meant as a new engine thing or in general. I think you may be right to check the idle stops.

[DesertFox4]

Sounds like idle set a little low.

[Av8r3400]

Mine actually quit this last week on roll out on the UL field at Airventure. My problem is the idle was set too low and I didn't catch it in time...

These motors need to have ~1800 rpm to sustain a good idle. I have mine set a little lower to aid decent. I have never had any issue on decent with the prop windmilling, just after touchdown when the rpm drops too low.

[Slyfox]

Gee, I have my idle set at 500, you got it, and get this, I always pull back on the throttle for a nice short landing. I do set the idle back up as I flare for landing, but sometimes my idle will go down to 1000 and run just so sweet. I do set it back up to 1800 idle, but I have to say I never I repeat never have had the engine quit. I say if the idle is low and you have a problem with the engine quiting, than you better check the balance of the carbs. I don't mean idle stop either, I mean cable to cable, left carb to right carb. I would go into the carbs and make sure they are nice and clean and the orings are in prestine condition, Oh and don't forget about the carb sockets, a little crack in those things and all bets are off on things.

Also remove the spark plugs, any wetness and the 912 series doesn't run for anything, maybe on higher idle, but idle, forget it.

[catz631]

I had my engine quit on me 3 times on final when I first bought the aircraft. In fact I think it was 3 of the 6 landings I made. Fortunately I was high enough and it does a reasonable glide.
The problem was too low an idle. I adjusted that and have not had a problem since but always think about it happening again and try to adjust my flight path accordingly.
Not nice to have this happen when you are new to the aircraft ! (or any time)
Dick Maddux
Fox 4
912UL
Milton,Fl

[HighWing]

Interesting topic. I have a friend that typically sets his idle to stop at full back throttle. He does it for short field work - he had a 700 ft. strip at his house with a mountain of cow manure just short of the threshold. He flew it that way for years and never had a problem. I always had my idle set much higher than that but never tried to get into his place. My guess is that if I flew his airplane, It probably would not have been pretty on final. As Dick and others suggest, it may have more to do with what you are used to than the absolute idle numbers. My thought always was, these engines don't windmill given the gearbox and I don't want to deal with the potential need for an engine start in that situation.

Lowell

[DesertFox4]

If it's running good in all other power settings then it's idle setting.
Raising the idle setting 100 or 200 rpms makes all the difference. One of my friends has his set lower than mine and I can kill that engine every time if I pull back on the throttle firmly on short final. Happens when the load is removed from the prop. Most set for 1800 to 2000 rpms on idle. I like 1200 to 1400 on mine. Allows for much shorter landings, less float. Like Slyfox and Av8r3400, at touch down I advance the throttle to the 1800 rpm range to keep out of the gearbox "chatter" . Slyfox, Av8r3400, my friend and myself know our aircraft very well and can do this without thinking about it anymore.
We can all set our aircraft to our own particular likings. Of course this brings to mind letting some one unfamiliar with your aircraft fly it without knowing how you have it set it up. :eek: If buying an experimental aircraft from someone it might be a question that needs to be asked before you fly it.

[SaintAero]

I'm not sure if this is applicable to this topic, but I sure wish I had this info with my Rotec Radial/Bing Carb.
Certain electric pumps are known to flood the carbs on Rotax 912s. See the Special Airworthiness Information Bulletin on page 2 of the EAA Flight Advisor and Tech Counselor news, Safety Wire. http://www.eaa.org/safetywire/july10.pdf
Don

[kmach]

Sounds like idle set a little low.
That's what I am thinking too, I think I read awhile ago that an idle of 1800rpm is good , any lower and your putting stress on the gearbox,if I remember the article correct. The rotax engine manual I think shows a minimum rpm of 1400, and I think that was around where this aircraft was idling at with throttle right out. :rolleyes: