PFH Sonex B

[Zack]

I was experiencing very high CHTs, especially on #3, with my Turbo Aerovee since the warm WX arrived. This high (p) side is what it is so I made the low side lower...see pic. The improvement far exceeded my expectations. That is a 30 deg angle, 3/4" high, closed ends. CHTs are all in line now and the temps are lower. The oil cooler performance has improved as well. I'll do more testing but so far so good...

peter

What did you use between you wings and fuselage skins?

[pfhoeycfi]

That is RV wing root seal from Van's Aircraft.
Peter

[karmarepair]

EAA test card 17 has one trim the airplane at 3 different speeds and push the nose over and increase the speed to plus 20, let go of the stick and count the number of oscillations to return to the trimmed speed. I can trim to any speed, but the plane does not want to return to the trimmed speed per the test. Has anyone else seen this in testing? Is this just the way the Sonex behaves?

Peter

It looks like you are within the "trim speed band". Ed Kolano has a series of articles on the EAA web site that talk about stability.
http://www.eaa.org/eaa/aircraft-buildin ... -technique
http://www.eaa.org/eaa/aircraft-buildin ... s-she-goes

These will require login
https://www.eaa.org/eaa/news-and-public ... ST%20PILOT
https://www.eaa.org/eaa/news-and-public ... ,-Friction

[kmacht]

EAA test card 17 has one trim the airplane at 3 different speeds and push the nose over and increase the speed to plus 20, let go of the stick and count the number of oscillations to return to the trimmed speed. I can trim to any speed, but the plane does not want to return to the trimmed speed per the test. Has anyone else seen this in testing? Is this just the way the Sonex behaves?

Peter

That test only works on airplanes with positive stability. The sonex has neutral stability. Whatever attitude you out it in it stays there. That is why it is such a bad IFR platform but a fun aerobatic one. What you experienced is completely normal in a sonex. Although you didn’t meet the stated test requirement objective on the card you still learned something about the flight characteristics of your airplane and that’s the whole point of doing the testing in the first place.

[DCASonex]

Sonex are designed for neutral stability, like fighter planes. My conventional tail A series Sonex does the same.

While it no doubt upsets John - (prolonged straight and level flight is strictly prohibited) - Monnett, a dual axis autopilot is a great assist if using the plane to go cross country.

David A.

[pfhoeycfi]

I'm frustrated with the gear shimmy. My setup is B model, tw and 5x5 tires on the standard Sonex wheels for the mains. My Sonex never had the smaller tires installed. I had widened the sonex wheel pants to fit the 5x5s. Not long ago, the axle assembly tab broke and the right side brake and wheel pant rotated forward and the pant was ruined. At this point I put collars on the axle assemblies to beef up the the gear leg bolt holes and that got rid of the shimmy. I purchased new T18 style wheel pants from spruce to fit the 5x5s rather than buy new sonex pants which I would have had to modify again to fit the 5x5s (alot of work). Anyway, the new wheel pants fit great. The mounting is very rigid. I have plenty of clearance between the pants and the tire. I installed new bearings and pucks while I was at it. However, with the new pants on, after landing, when I begin to slow down (not using brakes) a bad wobble sets in. A wobble here is more than a shimmy. I'm at a loss as to what is going on. My only though after all the work I've put in to the gear and wheel pants is that the mass of the 5x5 configuration with the larger wheel pant is too much for that length and diameter gear leg. One idea I suppose is to put the standard Sonex tires and pants. Any thoughts? Suggestions?

Peter

[T41pilot]

I was experiencing very high CHTs, especially on #3, with my Turbo Aerovee since the warm WX arrived. This high (p) side is what it is so I made the low side lower...see pic. The improvement far exceeded my expectations. That is a 30 deg angle, 3/4" high, closed ends. CHTs are all in line now and the temps are lower. The oil cooler performance has improved as well. I'll do more testing but so far so good...

peter

Do you happen to have a drawing of this part? I'm having a little trouble getting the dimensions of the closed ends just right.