SonexBuilders.net

Hi all,

Today my Sonex made its first flight piloted by my LAA (roughly the UK equivalent of the EAA) inspector. While the airframe is fine he reported that the engine RPM did not advance beyond the 3000 it is achieving statically giving poor climb performance.

Has anyone had similar results to this and if so what did you do to fix it? I am using the 2.5 needle and I get just over 3000 RPM static. There seems to be a very narrow range of needle adjustment to get a nice idle of around 800 RPM and 3000 RPM static. If the needle is leaned much I get around 3000 RPM followed by a drop of about 200 and a sort of popping noise (probably due to lack of fuel.) If I richen the mixture much it will not idle nicely at all.

What RPM should I expect to get at WOT in flight?
What RPM do you get on the takeoff run as speed starts to build? Should it immediately increase as soon as you start the run or is it gradual?

It is great to finally get the thing in the air but it's annoying to have trouble with the AeroCarb as so many people seem to.

Video of first flight: https://www.youtube.com/watch?v=x12CmkB5M3M

I had the same problem on first flight and my problem was prop related. I was using a Props Inc 54 X44 prop and ended up switching to a Prince 54X44 prop and problem was solved. I gained 150rpm static after switching props. Look for at least 3100 rpm static on the ground.

Thanks Rick,

I am using the Sensenich W54JV5L-44 prop which is the only prop approved for use in with the AeroVee in the UK. It's also sold by Sonex. To change it I'd have to submit a modification and a lot of stupid paperwork. You guys have it great with the EAA!

Each engine is different and with yours being new it may be a little tight until you have the chance to run it for a while. Having said that, in most cases a static rpm of 3000 or over means you have a healthy engine.

On takeoff I always looked for at or over 3000 rpm during the takeoff roll and normally saw 3100-3200 rpm on climb out. During full throttle, level flight you'll generally want to see at or over 3200 rpm. In most cases you'll see more like 3400-3500 rpm in level flight.

If it's running smoothly and well I'd consider running it wide open throttle for a while on your next flight and see if that helps at all.

I also can't help but ask but have you confirmed your indicated rpm is what you're actually getting?

Let us know how things go!

I have 125 hours on my AeroVee and have never seen 3,200 rpm. Climbout generally never exceeds 2,900 rpm. I have the Sensenich ground adjustable prop and it's on its finest setting, so I can't get any more RPMs out of this particular prop. Some other AeroVees easily get 3,200-3,400 rpm. I can sometimes get 3,150 WOT, but usually I'm down around 3,050, max. I've been offered other props to try, which I intend to do someday. But right now I'm rebuilding my AV (changed from Nickasil to standard cylinders), so I'll wait to see how it flies after the new break-in period.

MichaelFarley56 wrote:I also can't help but ask but have you confirmed your indicated rpm is what you're actually getting?

This is a very good point. I'm just trusting the output of my MGL E1 here but the values do look plausible. My test pilot took a considerable amount of time to reach 1000ft, going a second time around the pattern, so climb isn't good. I seriously doubt it is achieving anywhere near 80hp.

For what it's worth,I have 110 hours on my aerovee with a sensenich w54jv5l-44, and on climb out I rarely see over 2900 rpm. Static rpm is around 3000. It has been like this from new and has not changed.My rate of climb is almost spot on to sonex published numbers.

The video makes it look like you aren't using the wheel pants or fairings. The leg fairings are important and get you an extra ~8mph at cruise. I believe putting them on will make it seem like you have an extra 10-15% power. The wheel pants also help, but I think they are only good for another couple mph.

I have a different propeller (54x46 Prince P-Tip) and see 2850-2900rpm on climb out and 3150-3200rpm at WOT cruise. My intuition is whatever power you are lacking is not due to the Aeroinjector. Once you are sufficiently high above the ground, experiment with leaning the mixture control out and see how much rpm increase you get. I don't think any amount of needle-swapping or adjustment will be able to improve on this number--the needle adjustments just help it run smoothly at all power settings.

ccm wrote: There seems to be a very narrow range of needle adjustment to get a nice idle of around 800 RPM and 3000 RPM static.

If you're getting a nice idle you are no doubt too lean. You may need to try a richer needle.

Congratulations on your first flight!

I agree with the advice Chris has provided.

Also check your timing on your secondary ignition in flight as suggested by Sonex. I gained almost 100 rpm when I adjusted my timing after my first flight.

Jake