aircraft engines or planes without a mixture control knob?

N918KT · Post by **N918KT** » Sat Dec 08, 2012 10:30 pm

Hey guys, here is an interesting question. Are there any aircraft piston engines 100 hp or less that do not have a mixture control knob for airplanes, but has a throttle only, besides Rotax engines?

Are there any LSAs or SP eligible airplanes that does not have a mixture control knob, but only a throttle, besides Rotax engines?

I can't think of one piston engine or airplane off the top of my head besides Rotax engines.

drseti · Post by **drseti** » Sun Dec 09, 2012 9:49 am

The Rotax 912 series is the only carbureted engine I know that has self-compensating carbs, thus no mixture control needed. A number of high-performance engines use FADEC (full authority digital engine control) that use a single knob, no mixture control - those are all fuel injected engines. A lot of the 1930s antiques used Continental engines with no mixture control - but it was probably felt that nobody was going to fly them high enough to need to lean the mixture!

I've flown several Ercoupes that had the mixture wired to full rich, so the mixture control was essentially disabled, and you couldn't lean if you wanted to. I never quite understood that...

N918KT · Post by **N918KT** » Sun Dec 09, 2012 11:44 am

Paul, what are the names of the Continental engines you mentioned that do not use mixture control?

Jim Stewart · Post by **Jim Stewart** » Sun Dec 09, 2012 11:57 am

Jabiru engines don't have a mixture control as they use the Bing pressure compensating carbs like the Rotax 912 and 914.

N918KT · Post by **N918KT** » Sun Dec 09, 2012 12:16 pm

Thanks Jim. I didn't know that Jabiru engines do not have a mixture control knob. What exactly are compensating carbs by the way?

Jim Stewart · Post by **Jim Stewart** » Sun Dec 09, 2012 12:28 pm

From the Jabiru website:

"The Bing carburetor is an altitude compensating carburetor which when set for base altitude will take care of the leaning chores automatically. The carburetor accomplishes this by sensing the difference in pressure between the outside air and the engine air. A diaphram moves a jet needle to change the rate of fuel flow as pressures change and a carburetor bowl vent keeps fuel pressure in the bowl in line."

drseti · Post by **drseti** » Sun Dec 09, 2012 12:35 pm

The Bing 64 carb used on the Rotax, and old BMW motorcycles (and, as I've just now learned, on the Jab) is a really clever design. The mixture jet needle is suspended from the middle of a round rubber diaphragm. Ambient air pressure is applied to one side of the diaphragm, so it flexes as air density changes with altitude. This raises or lowers the needle in the jet, changing the mixture as required. Works quite well up to about 10,000 feet, above which the engine does start to run a bit rich.

drseti · Post by **drseti** » Sun Dec 09, 2012 12:38 pm

N918KT wrote:Paul, what are the names of the Continental engines you mentioned that do not use mixture control?

Depending on which carb they have installed, some Continental A45, 65, 75, and 85 engines may not be equipped with a mixture control. You find this engine in a lot of 1930s designs.

N918KT · Post by **N918KT** » Sun Dec 09, 2012 1:56 pm

Thanks Paul, just another question. The Continental engines that you just mentioned. Do any of the engines need to be hand propped to start the engine or can they use an electric starter?

drseti · Post by **drseti** » Sun Dec 09, 2012 2:08 pm

Most of those antiques were originally hand-propped, Kevin. But it's not so difficult to add an electrical system to them. I know of several C-65 powered Luscombes that have been modified with starters, batteries, and generators.

N918KT · Post by **N918KT** » Sun Dec 09, 2012 2:15 pm

Thanks Paul and Jim! That's all I need to know. Thanks for the information!

zaitcev · Post by **zaitcev** » Sun Dec 09, 2012 6:21 pm

Bristell announced that they are going to install an UL engine from the factory, and UL build them a new engine UL318i. If anything comes out of it, Bristell is going to have an alternative to Rotax with signle-lever power control.

I'm sure that some SP-eligible experimentals must be flying around with UL260i of 97 hp.

theskunk · Post by **theskunk** » Sun Dec 09, 2012 11:05 pm

I've heard that the carb on a 912 really only does a good job leaning itself out until about 6500... any higher and you end up richer than it really could be to make best power... any truth to this, and anything to be done about it?

gmohr · Post by **gmohr** » Wed Dec 12, 2012 7:59 am

The Bing on my Jab 3300 is good to about 5000' after that it runs rich. I had a Hackman mixture control put on
it and it made a world of difference in both the GPH and in EGT/CHTs. Coming back from Arizona at 9500'
I averaged 3.8gph and 120kts at 75% throttle.

CharlieTango · Post by **CharlieTango** » Wed Dec 12, 2012 9:05 am

My home field is at 7,100' and local terrain goes above 14,000 and typical destinations for me are near sea level.

The mixture has worked very well for me.

Sport Pilot Talk

aircraft engines or planes without a mixture control knob?

aircraft engines or planes without a mixture control knob?

Re: aircraft engines or planes without a mixture control kno

Re: aircraft engines or planes without a mixture control kno

Re: aircraft engines or planes without a mixture control kno

Re: aircraft engines or planes without a mixture control kno

Re: aircraft engines or planes without a mixture control kno

Re: aircraft engines or planes without a mixture control kno

Re: aircraft engines or planes without a mixture control kno

Re: aircraft engines or planes without a mixture control kno

Re: aircraft engines or planes without a mixture control kno

Re: aircraft engines or planes without a mixture control kno

Re: aircraft engines or planes without a mixture control kno

Re: aircraft engines or planes without a mixture control kno

Re: aircraft engines or planes without a mixture control kno

Re: aircraft engines or planes without a mixture control kno